Types Of Inverter Circuit And Hardware Design

7.1 Describe the different type of inverter circuit. 
7.2 Voltage source inverter circuit
7.2.1 A single phase half bridge inverter
7.2.2 A single phase full bridge inverter
7.3 Current source inverter
7.4 Impedance source inverter
7.5 Three phase inverter
7.5.1 Sinusoidal WPM
7.5.2 Square wave operation of three phase
7.6 Multilevel inverter

8. Hardware Design 
Describe below component and why chosen 
8.1 Transformer
8.2 Mosfet (IRF540)
8.3 IC (CD4047BCN)
8.4 Diod (1N4007)
8.5 Potential resistor
8.6 Resistor
8.7 Capacitor

Introduction to Inverter Circuit

An inverter is defined as an electric device that converts the direct current to alternating current that can be used in any electronic circuit. In the last few years, the use of the inverter circuit is growing rapidly because it is a very simple approach to produce AC power directly from the DC power supply. The static inverters have no moving part and mainly they are used for wide range applications such as for small switching power supplies and produce the high-level direct current for industry purpose. The power inverter is a large power oscillator that has the ability to control and manage the alternating current with the help of direct current.

To convert AC voltage into DC a new method is used which is called as rectifier and inverter is an opposite technique of rectifier. The DC power is the unidirectional flow of electric charge that does not change with time which is generated from various sources such as batteries, solar cells, and thermocouples. The main goal of this project report is to design and implement inverter circuit and discuss the different kinds of the inverter circuit with their specification. To improve the effectiveness of this project a literature will be conducted that provide the overview of types of inverter circuits [1].

It is observed that inverter allows the utilization of 220-volt power appliances from a solar battery system and supply a voltage which is equivalent to an arms value of 230 volts. The overall efficiency of a square wave inverter is very large as compared to the sine wave inverter because of their simplicity. By using transformer the produced square wave voltage can be transformed to a value of 230v which is used during radio transmission. In the field of engineering generation of a perfect square wave with a lower and upper threshold is one of the common challenges that can be avoided by using an amplification circuit.

Alternating current refer as the electric current that flows in the reverse direction of applied voltage but in DC the flow of charges is only in single direction. The main concept of AC power supply is that it changes with time and the input voltage, frequency signals and output voltage depends upon the size and design of the electronic circuit. An inverter is used by many electronic companies that produce small AC power supply by using DC voltage as an input.

Block Diagram of Inverter Circuit

The electronic inverters can be utilized to generate a smooth varying AC sine wave by using a DC input for which there are main two components used for example inductors and capacitors to produce the more effective output signal. A recent study indicates that this technique can be utilized with transformers to change a certain DC input signal into a different DC signal but the output voltage must be lesser than the applied input voltage [2]. It follows the property of energy conservation that an inverter cannot provide more output power because some of the energy can be lost as heat during the generation of AC signals. The key concept of an inverter circuit is that DC signal inserts into the primary windings of the transformer with the help of spinning.

When the plates of transformer rotate then it suddenly switches the connection to the primary winding and transformer gets an AC signal instead of DC power. Generally, a power inverter circuit uses a stable DC input voltage which is capable to provide enough current to the circuit and it depends upon the size and design of the circuit. There are following input voltages are used for the generation of AC voltage by using inverter circuit:

• 12 volt DC
• 24 and 48 volt DC
• 200 to 400 volt DC
• 300 to 450 volt DC

Block diagram of the inverter circuit

The block diagram of power inverter consists of the main three components, for example, DC source, an oscillator circuit, and step up transformer. The DC source is used to provide a DC input voltage which is generated from any battery because the inverter circuit requires a stable direct current to generate a high-level AC power supply. The output of DC source feed into the input of oscillator circuit or resonance circuit which is also called as a tank circuit. The tank circuit can be designed with the help of power transistors, inductor, capacitor and value of resistor [3]. The values of resistor, inductor and capacitor are also called an element of resonance circuit but the main condition for generation of the tank circuit is (R²) < [4L/C].

After that, the output of an oscillator is transferred on an input of step-up transformer and resonance circuit provide an unstable AC waveform. The main concept of step-up transformer is that they enhance the amplitude of applied waveform and most of the electronic circuit uses the step-up transformer as per requirement. This stage provides a proper AC output signal with 50Hz frequency by using 12 volt DC supply consumers can generate 230 volt AC power supply. During generation of AC voltage in the inverter circuit, there are mainly two kinds of oscillator circuits are used for example harmonic oscillator and a relaxation oscillator.

How Inverter Circuit Works

Circuit Diagram and working principle

Below diagram indicates a min inverter circuit that provides 230 volt AC output by using 12-volt input power supply. In which there are two NPN transistors used T1 and T2 that acts as a simple oscillator to produce the frequency signals. After that, these waves are inserted into the transformer by using secondary winding. The applied 12VDC power initially passes by the 330 uH choke that handles noise and distortion and R1 resistor connected through T1 and transistor T2 interconnected with secondary windings of the transformer. Therefore, capacitor C1, T1 and T2 oscillate and the oscillation is inserted into the transformer winding through centre tap which uses DC power from a battery source. So, the oscillation of transistor T1 and T2 produce Alternating current in the secondary windings of a transformer that lights the CFL [4].

5. Project objective

The main objective of this project report is to analyse the concept of the inverter circuit with their working principle and describes the various types of power inverters. To gain this objective a literature review will be conducted that explain the types of the inverter circuit with their block diagrams and also review the opinion of other experts.

6. Project scope

This project report is completely based on the inverter circuit and it can be used in an electronic circuit where AC power is required by using DC input voltage. A recent study shows that most of the small engineering projects are done by using rectifiers and inverters because rectifiers convert AC current into DC current and inverters convert DC into AC power. This mini project is categorized into main two parts to improve the effectiveness of the project, for example, literature review and hardware design.

Furthermore, the literature review will be divided into numbers of parts such as types of the inverter circuit, voltage source inverter, current source inverter, impedance source inverter, three-phase inverter and multilevel inverter. This literature review will provide an overview of the inverter circuit and their types with proper explanation and it will avoid the issues faced in previous research.

Hardware design will provide a platform for analysis and a design inverter circuit. There are numerous components will be evaluated in this step, for example, transformer, MOSFET, IC, diode, potential resistor, capacitor all these are used to generate an inverter circuit. The main focus of this project report is to design a 230-volt inverter circuit by using 12 volt DC input voltage. For which around 1.5 KVA power will be required and the output power will be less than these input power due to energy conservation [5].

Types of Inverter Circuit

7. Literature Review

The inverter circuit is an advanced step which is used in most engineering projects to produce an AC power by using DC input source. Recent investigation shows that power inverters are exactly the opposite of power converters that perform as an AC power source. There are numerous researchers that research on this topic and they identified that implementation of inverter circuit by using DC voltage is very difficult. Most consumers use the 12V battery to make DC input voltage and a step-up transformer is used during the generation of AC power that increases the amplitude of an applied signal.

The power inverter is a kind of source that provides proper AC signals or power of 50Hz frequency and it is detected that most of the inverter circuits use square wave as compared to sine wave due to their efficiency. To produce a sine wave is very complex and more expansive but the square wave can be easily generated by the oscillator. For this mini project, a square wave is used and the target of this project is a common home appliance, computer devices and other electronic components.

An inverter circuit includes a signal generating process that provides proper square wave with 50Hz frequency and this signals will be converted into AC waves by using the concept of push-pull amplifiers. This inverted alternate wave then allows driving two sets of power devices to wither power MOSFET or transistor in the configuration of the ladder network [6]. The main role of MOSFET transistor is to drives the DC current with the help of step-up transformer and an electromagnetic field is produced at the output of this transformer.

7.1 Describe the different type of inverter circuit

A recent study identified that there are mainly three kinds of inverter circuits used for the generation of AC output signals which are described below:

• The square wave inverter
• Modified sine wave inverter
• The pure sine wave inverter
• The Square wave inverter

It is observed that the square wave inverter is one of the simplest types of an inverter that converts a stable DC input voltage into a high-level AC output wave. But the main problem identified by Ajami, et al., (2014) with this inverter is that it cannot provide the proper AC waveform at the end of the output. It provides a square waveform which is very simple and cheap to generate from the oscillator circuit. According to Banaei, et al., (2014) the cheapest and simplest construction of a square wave inverter can be developed with the help of on-off switching system and small step-up transformer.

Voltage Source Inverter Circuit

The modified sine wave inverter circuit 

The design and implementation steps of this type inverter circuit are a bit more complex and expansive as compared to the square wave inverter and it is also called as quasi-sine wave inverter. This circuit indicates few pauses before the phase shifting stage that means, unlike a square wave circuit it does not change the phase from positive to negative. This process provides a good AC output wave and many electronic systems involve this step to produce an AC power supply.

Below figure shows the output waveform of a quasi-sine wave inverter circuit which is very similar to the pure sineAbove figure shows the circuit diagram of a quasi-sine wave inverter that involves a harmonic oscillator. The output of oscilloscope fed into the primary windings of a step-up transformer that increase the input values of the oscillator. After that these primary winding produce an electromagnetic field by which a DC current flow in the secondary winding and provide the proper AC output [6].

A pure sine wave inverter

The electronic and electrical figure of the pure sine wave is more complex as compared to the other kinds of the inverter circuit. Binbin, (2008) identified another approach to generate a high-level output sine wave in which first produce a square wave by using square wave inverter and then modify this waveform to achieve a perfect sine wave. There are many benefits of this inverter circuit which are the following:

• More efficient and consume less power
• It can be adjusted as per requirement
• The output sine wave is more reliable
• More sensitive equipment

The voltage source inverter is very less expansive to design and implement which is used to produce the high-level AC output power. In this kind of inverter, circuit switches are turned on and off in particular intervals to transfer the rectangular pulses of the input voltage. The voltage source inverter has stiff the DC voltage with zero impedance at the input terminal of the inverter circuit

According to Ajami, et al., (2014) if the applied DC signal is in the form of a voltage source then the inverter is known as voltage source inverter. It is discussed that the VSI circuit has the ability to control the AC output voltage and the output waveform of this circuit does not depend on load interconnect at the output terminal. Above figure shows the fundamental working of voltage source inverter that involves the DC input voltage and a combination of resistor, capacitor and inductor is used to produce a resonant circuit for inverter [7].

Current Source Inverter Circuit

A Single phase inverter is defined as an inverter circuit that uses only a single phase input power supply which is used for small electrical projects. It divided into main two parts which are described below:

• Half-bridge inverter
• Full bridge inverter
• 7.2.1 A single phase half bridge inverter

The single phase half bridge inverter is defined as a circuit that uses a half bridge connection of diode to produce the AC power supply. It contains the main two switches and every of their capacitor has a voltage which is equal to the fraction of applied DC voltage. In which both diodes works in the opposite manner for example if D1 is in on condition that D2 will be in off condition and at a time the only diode will work. Half-bridge VSI uses two large value capacitor that provides a neutral point O, in which every capacitor maintain a constant voltage (v1=v2=Vdc/2).

 This is the main reason that produces very low order harmonics and for bidirectional flow both diode connected into the opposite manner [8]. According to Ajami, et al., (2014) both rectifiers cannot be ON simultaneously because these are connected across the DC source. If both two switches conduct at the same time then a short circuit situation will be developed by data link source.

In half-bridge inverter circuit, the input DC power divided into equal voltages by using capacitive potential divider rule. The half bridge circuit involves one pole and every pole consist of 2 series connection which is shown in the below figure.

In which every switch consist of an IGBT kind transistor that controls the overall performance of the circuit and two diodes D1 and D2 are connected in anti-parallel with Q1 and Q2 switch. According to Ajami, et al., (2014) the main advantage of these switches is that they have the capability to conduct a bidirectional current. In the configuration of the half-bridge circuit, the single-phase load is interconnected between the mid-points of the applied DC power supply and in circuit diagram these points are O and A.

The working principle of half bridge inverter

In the configuration of the above circuit, there are main two states for both Q1 and Q2 and the overall output voltage can be produced from either upper half or lower half DC power. The working principle and operation of these states are described below:

State 1

In which upper half DC power and switch Q1 both are in conducting situation and remaining parts are in the non-conducting situation. During a time of 0 to T/2, the switch Q1 is on and an upper DC value appears across the load and output will be taken from only diode D1.

Impedance Source Inverter Circuit

State 2

In this step, lower half part of DC voltage and switch Q2 is in conducting situation and remaining parts will not involve in this operation. During the time from T/2 to T, Q2 is on and lower DC power is obtained across the load and th

The output waveform of the single phase half bridge will be shown below that works on both upper DC and lower DC voltage. For the first half cycle (O to T/2) diode D1 will work and D2 will turn off but in the next half cycle (T/2 to T) D2 will turn ON and provide an AC output.

7.2.2 A single phase full bridge inverter

The full bridge inverter is very similar to the half bridge inverter circuit but the main difference is numbers of diode that means it involves 4 rectifiers as compare to the half bridge. It used the concept of half bridge, both switches Q1 and Q2 or Q3 and Q4 cannot work simultaneously due to short circuit issue. It is identified that the AC output is more effective that is twice of the half bridge output value and the output voltage is defined by V_AB received from the load [4]. Below figure indicates the circuit diagram of full bridge inverter that involves four switches Q1, Q2, Q3, and Q4 and four diodes D1, D2, D3, and D4.

In which there are main two pole voltages, for example, VAO and VBO which are very similar to the half-bridge pole (VAO). These both poles consist square wave but they have few phase difference and the voltage across this pole can be determined with the help of Thevenin’s theorem. The working and operation of this inverter divided into main four states which are described below:

State 1

In which the switch Q1 and Q4 are in conducting situation and rest of components will not work and through Thevenin method, the voltage at point A and B are calculated. Total output voltage collected as V_AB =V_AO -V_BO =V_d. Below figure shows the configuration and path of current and output value obtained between point A and B.

State 2

In this condition, the switches Q2 and Q3 are in only conduction manner and rest of switches are in OFF mode. The voltage between pole A and B can be calculated from the load connected between A and B and output is found by V_AB =V_AO -V_BO = -V_dc.

State 3

In which voltage switch Q1 and Q3 are in conveyance manner and output voltages between pole A and B are determined by V_AB =V_AO -V_BO = 0. The main difference between each state is the point of contact and below diagram shows that when D1 and D3 turn ON then remaining diode work as an open circuit.

Three-Phase Inverter Circuit

State 4

This is the last state of full bridge inverter and Q2 and Q4 both are in conducting manner. The output voltage in this state is determined and load voltage is calculated as VAB =VAO -VBO = 0. In which only diode D2 and D4 will participate and rest of diode D1 and D3 will work as an open circuit. Below diagram describes the concept of full bridge inverter at state 4:

Below figure indicates the final output waveform for a single phase full bridge inverter circuit. In which the output voltage depends upon the time and configuration of each state. For VAO the first half cycle of input wave works on switch Q1 and next half cycle conducted in Q2 switch [10].

7.3 Current source inverter

The current source inverter is defined as a circuit that converts input DC current into AC output current. The main difference between voltage source inverter and current source inverter is that VSI use DC voltage as an input and CSI use DC current as an input power. It is also known as a current fed inverter and the output voltage of this circuit does not depend on the load but the nature of current depends upon load impedance [11]. The main benefit of this inverter circuit is that it is more reliable that involves large inductor value to avoid the issue of commutation failure.

Below figure indicates the single-phase current source inverter that involves a combination of diode and thyristors. In which load is connected between the configuration of four diodes and two high-level capacitors are used to store electric energy. A constant source is used with stable DC current that contains an inductance of suitable value and thyristor Th1 and Th3 are turned ON in the first stage and Th2 and Th4 both are turned ON in next stage. Capacitor C1 is used for an upper half cycle and C2 is used for next lower half cycle and four diodes D1, D2, D3, and D4 are interconnected in series combination with thyristors.

The working and operation of current source inverter divided into main two modes which are described below:

Mode 1

At t=0-, thyristor Th₂ and Th₄ are in conduction manner for an upper half cycle and current flows by the path Th₂, L, D₄, Th₄ and I. initially capacitor C₁ charged with the polarity –Vco and both capacitor works for upper half and lower half respectively. At t=0, thyristor Th₁ and Th₃ both are activated through a clock pulse and remaining Th₂ and Th₄ are in the non-conducting situation.  

Multilevel Inverter Circuit

Mode 2

In this mode, both diode D₂ and D₄ are in leading manner but at time t=t₁ both diodes D₁ and D₃ get in forward prejudiced and start conducting. At the finish of time t₁ diode D₁, D₂, D₃, and D₄ will be turned ON and capacitor interconnected in parallel with L.

7.4 Impedance source inverter

The impedance source inverter is also called as Z-source inverter which is a combination of capacitor, inductor. Generally, it is used in automobile application like cars, bike and many more that contain 2 capacitors and two inductors. As compared to the voltage source inverter circuit which is operated in only six active stages and 2 zero modes, the impedance source circuit can be performed in the shoot through stage [12]. In which the upper and lower cycle involve one or more phase legs and it is the very advanced approach that provides more effective AC output. Below diagram gives an overview of the impedance inverter circuit with shoot through mode and non-shoot through mode.

It is assumed that both capacitors C1 and C2 are identical and initially charged through input voltage, Vin. In the case of shoot through the stage, the diode D1 is in reverse biased that blocks the capacitor voltage due to this situation the input voltages are removed from the remaining circuit. At that time the electric energy is shifted from capacitor C1 to L1 and C2 to inductor L2 but in non-shoot through mode D1 diode is in forward biased and energy is moved from inductor L1 to C2 and L2 to C1 [13]. There are many applications of this inverter circuit, for example, adjustable speed drives, offshore wind energy, vehicular applications, hybrid electric vehicle, photovoltaic cell, uninterruptible power transfer application, and grid applications.

7.5 Three-phase inverter

A 3-phase inverter circuit converts a DC power supply into an AC voltage with three phase and their three arms A, B, and C are delayed by a 120-degree angle. In which the inverter switches produced a proportion of 50% and the swapping stage happens after each T/6 time. It is studied that the pole voltage of 1-phase across the load is equal to the extreme voltage of the 3-phase inverter. In the configuration of three-phase inverter switches Sw1 and Sw4 or Sw3 and Sw6 or Sw5 and Sw2 are connected into series with each other [14].

In the above configuration, the stage order of the shaft voltage is obtained as V_AO, V_BO, and V_CO and a high-level capacitor placed in the parallel with switches system that stores the applied input voltage. It is investigated that the switching system in three-phase inverter circuit follows a proper sequence that is Sw1, Sw2, Sw3, Sw4, Sw5, Sw6, Sw1, Sw2…… and so on. It can be observed that every switch conducts for 180-degree angle and the higher and lesser configuration of the inverter circuit conduct in a balancing situation [15].

Hardware Design Components

To reverse the phase sequence at output terminal can reverse the switching sequence of the three-phase inverter circuit. According to the conduction sequence the working operation of three-phase inverter is conducted into main six combinations for example: (Sw5, Sw6, Sw1), (Sw4, Sw5, Sw6), (Sw6, Sw1, Sw2), and (Sw2, Sw3, Sw4), (Sw1, Sw2, Sw3), and (Sw3, Sw4, Sw5).

This type of configuration is used in motor drives, unified power controller, active filters, and uninterrupted power supplies. The standard 3 phase inverter circuit involved six switches the sequence of these switches depends upon the modulation scheme. The DC input power can be taken from either single phase or three phase power source by using half bridge or full bridge rectifier system. In which states 7 and  8 are known as zero switch stages that generate Zero AC voltage across the load and AC current will flow through the upper part or lower part of the inverter circuit. The rest of switching states (1, 2, 3, 4, 5, and 6) are known as non-zero modes that generate non-zero AC output voltage. There are mainly two kinds of mode involves in the three-phase inverter circuit which are described below:

• 180-degree mode of conduction
• 120-degree state of transmission

180 mode of conduction

In such kind of state, each switching device is in transmission stage for 180-degree angle and turned ON at the angle of 60 degrees. The point A, B, and C are the output terminals of the three-phase inverter which are interconnected to the star or delta process of the load. For the angle period 0 to 60 degree the switches S1, S5 and S6 are turned ON and point A and C are interconnected to the applied power source. The load voltages across these three terminals are given by:

• VAN=V/3
• VBN=-2V/3
• VCN=V/3

The streak voltage of this configuration is described below:

• V_CA= V_CN − V_AN = 0
• V_AB= V_AN − V_BN = V,
• V_BC= V_BN − V_CN = −V,

120-degree mode of conduction

In this kind of approach, every electronic device is in a conduction state for 120 degrees and it is a more effective process for a delta connection in the load. Moreover, only two devices are in conducting manner because every system conducts at an only 120-degree angle. In this type of configuration, the point A is connected through the positive end but the terminal B is interconnected with the negative end of the applied input source. The point C on the load is called a floating stage and line voltage is always equal to the phase voltage [15].

Phase voltages = Line voltages

Design of Inverter Circuit

VBC = −V/2

VCA = −V/2

VAB = V

7.5.1 Sinusoidal PWM

The PWM is defined as a technology which is used for the reduction of harmonic distortion in a load current. It is a part of modulation techniques that improve the width of the input clock pulse and transfer from one source to another. In the field of the inverter circuit, a high-level harmonic distortion occurs due to turned ON switches for long times. The sinusoidal pulse width modulation waveform is taken by comparing the desired modulated signal with a triangular waveform. With the help of this approach, the strength of the input signal can be increased and the modulation index for PWM is given by Am/Ac.

In the sinusoidal PWM three-phase inverter three sine waves phase shifted by 120-degree angle and the output voltage is compared with a large frequency carrier signal. The two signals are mixed in a comparator whose output is very high when the sine wave is higher than the triangle [16]. It is observed that the output waveform of the inverter circuit is not much smooth due to which some harmonic distortion occurs into the system. Such kind of problem can be resolved by adopting a pulse width modulation technique and people can enhance the efficiency of the inverter circuit.

Figure: PWM illustration by the sine-triangle comparison method (a) sine-triangle comparison (b) switching pulses

This technique provides a sinusoidal waveform with the help of the filtering process and output waveform depends upon the width of the applied signal. The appropriate output is obtained through varying the frequency signals and amplitude of a carrier signal. In the three phases SPWM a triangular waveform is compared with 3 sinusoidal power voltage such as Va, Vb, and Vc that are 120 degrees out of phase with every another and the relative levels of the waveforms are utilized to analyse the switching of the devices in every phase [17]. There are numerous applications of this technique, for example, motor speed control, audio amplifiers, converters and many more.

Above figure shows that the strength of applied DC voltage is very low due to which inverter circuit cannot provide a high-level AC output voltage. A high-level harmonic distortion occurs during DC to AC conversion process and PWM provides a platform to handle such kind of issue in the circuit and enhance the overall efficiency of the system.

7.5.2 Square wave operation of three phase

Conclusion

In such kind of operation, a square wave is used to convert DC voltage into an AC voltage and it involves a DC source to produce a stable waveform. The configuration of a three-phase inverter circuit includes six IGBT switches, a high-level capacitor and input voltage source. For the greatest simple mechanism scheme, the process of the three switches is synchronized so that one button functions at every 60-degree opinion of the important output waveform [18]. This generates a line-to-line yield waveform that has 6 ladders. The six-state waveform has a zero-voltage stage between the positive and negative pieces of the square-wave that can address the issue of harmonic distortion. When carrier-based PWM methods are applied to six-step waveforms, the simple inclusive form, or envelope, of the waveform is engaged therefore the 3rd harmonic and its multiples can be reduced.

The input current switch of the planned circuit is reached by a zero phase module of the output voltage and the current of the motor is realized with the help of positive phase at the same time [19]. It is identified that the zero phase current in the circuit does not produce torque and a square wave operation is involved in the configuration of the three-phase inverter to avoid the switching loss of the circuit. At the time of square wave operation, the frequency of the switching system agrees with the frequency of output waveforms.

7.6 Multilevel inverter

A multilevel inverter circuit is defined as a power device that has the potential to more effective AC voltage at the end of output terminal through applying multiple low-level voltages. Generally, a two-level inverter circuit is utilized in order to produce the AC output voltage with the help of DC voltage. A two-level circuit generates 2 various voltages for the load which are used for the generation of AC power supply [20]. For switching a pulse width modulation process is used which is a more effective approach to produce an AC output power supply. Mainly, this kind of technique is used for a few applications because it produces a bit more distortion losses in the output signal.  

In this kind of technology, more than two levels of voltages are combined with each other and the output voltage has very low Dv/Dt and also avoids the issue of harmonic distortion. It is studied that the smoothness of the output waveform is completely depended upon the level of input voltage. There are main three topologies used in multilevel inverter topologies which are described below:

• Cascaded H-bridge multilevel inverters
• Flying Capacitor multilevel inverters
• Diode Clamped multilevel inverters
• Cascaded H-bridge multilevel inverters

This kind of inverter circuit uses few H-bridges circuits which are connected in series to generate a sinusoidal output waveform. In which every cell involve 1 hybrid bridge and the output power is produced by this multi-level inverters. Suppose, if there are total K cells in an H-bridge circuit than the numbers of the output voltage is given by 2K+1. The main advantage of suck kind of inverter circuit is that it needs fewer amounts of components as compared to the two-level inverter. Below figure shows the circuit diagram of an H-bridge inverter circuit that involve three modules for example module 1, module 2 and module h.

In a single phase inverter system every phase is interconnected to a single stable DC power and every level produce 3 voltages for example, positive, zero and negative. It can be taken by combining the AC power with the Dc output and using various four switches. It is analysed that the inverter circuit will turn ON when two switches with the opposite place will remain ON [22]. There are mainly two kinds of cascaded H-bridge inverter which are described below:

• 5 levels h-bridge inverter
• 9 levels H-bridge inverter circuit
• More effective process
• The manufacturing process is very simple
• Fewer distortion losses
• Cheap
• Each H-bridge network needs a separate dc supply
• Very limited applications

Diode Clamped Multilevel Inverters

This kind of inverter circuit utilizes a clamping diode to handle the issue of voltage stress and it was developed in the 1981 year by Babae. In which total 8 switches are used to control and monitor the DC power source and obtain the AC output voltage. This technique involves the five capacitor and 6 levels and every capacitor store a certain voltage by using an applied DC source [23]. The main advantage of this inverter circuit is that it can turn ON all five switches at any time and below figure shows the one phase diode clamped circuit.

The most important application of diode-clamped inverter is when a large voltage DC and AC transmission lines are required. It can be used for controlling the speed of a DC motor and some of the industries use the technique in static variable compensation.

Advantages

• The values of capacitors are very low
• Back to back inverter circuits can be used
• Large efficiency as compare to H-bridge inverter circuit
• All capacitors are pre-charged
• The value of clamping diodes are growing with the increase of every level
• DC voltage level will discharge when controlling and monitoring are not precise

Flying capacitor multilevel inverter

The configuration process of this kind of circuit is very simple and similar to the clamping diode inverter but in which the flying capacitor is used to limit the output voltage. In which the applied DC voltages are categorised through the capacitors and voltage value across every capacitor is given by Vdc. It is observed that if a K level flying capacitor involves in an inverter than 2K-2 switches will be used in order to obtain the AC output voltage.

As compared to the diode clamped inverter this technique also involves switches, diodes, and DC capacitors but it does not use the clamped circuit to obtain the AC output voltage. In which a flying capacitor is used that has the potential to avoid the distortion losses and block reverse bias voltage that increases the efficiency of the circuit [24]. It used a ladder network that develops the different voltages levels for each capacitor. There are numbers of advantages of this technique which are following

Advantages of flying capacitor inverter

• Provide more effective AC output signals
• People can control and monitor reactive and real power flow
• Voltage control is more difficult
• Very complex process
• The efficiency of switches are very less
• More expensive process
• 8. Hardware Design

For a generation of an AC power by using inverter circuit there are numbers of hardware and devices used which are described below:

• Transformer
• MOSFET
• IC
• Diode
• Potential resistor
• Resistor
• Capacitor
• 8.1 Transformer

A transformer is defined as electric equipment that transfers electric power from one circuit to another by using electromagnetic induction. A recent study shows that electromagnetic induction generates an electromotive field within a conductor that provides a time-varying magnetic field [25]. The main purpose of this device is to improve and reduce the AC voltage in electric power applications. In the last few years, most of the information technology use this process to increase the strength of input voltage and it has the potential to control the input voltage as per requirement.

A simple transformer uses two type of winding system like primary and secondary winding and works on the concept of faradays law of induction. Most the electric devices use this process to interconnect two or more circuits by using an oscillating circuit. The mutual induction is a kind of process by which a coil generates an electric voltage into another coil without modifying their frequency [26]. The primary winding takes the applied voltage and secondary windings received the output voltage which may be high or low depends upon the nature of the application. There are mainly two kinds of transformers uses in electric engineering which are the following:

• Step down transformer
• Step up transformer
• Step down transformer

The main concept of a step-down transformer is to reduce the output voltage that depends on the nature of the application. In which the input applied voltage is very high and the output voltage is very low. Step down transformer contains the high voltage in primary windings and high current in secondary windings which is made of thick insulated copper wires. There are numerous applications of this transformer, for example, doorbell, and voltage converter and an inverter circuit.  

Step up transformer 

A step up transformer devices is the opposite of a step-down transformer that increases the value of input voltage. In which the amount of wires on the secondary winding is very high as compared to the primary winding due to which the output voltage of secondary winding is very large. For this project, a step-up transformer is used because the inverter circuit converts DC into AC and we required a transformer that increase the output voltage and provide 230-volt power [27]. Due to the principle of energy conservation, the transformer converts low voltage high current to high voltage low current.

MOSFET is defined as metal oxide silicon field effect transistor which is a part of the transistor that operates in only enhancement mode. This kind of electronic device is more sensitive as compare to FET because their input impedance is very high. For this project, IRF540 MOSFET is used that has the potential to increase the efficiency of the circuit and it is very fast switching speed as compare to IGBT and other.

This MOSFET is completely based on HEFFER technique and operates on the temperature range between -55 degree and 175 degree Celsius. For the application of inverter circuit, IRF540 is one of the best transistors that provides high switching speed. There are numerous applications of this technology, for example, switching regulator, converters, large power switching drivers for large speed, and motor drivers.

IRF540 is defined as N-channel MOSFET which is used for very high switching process and amplification of input signal. There are main three terminals of this transistor for example drain, source and gate in which source provide an input power supply and drain collect the output voltage from the circuit. Below figure indicates the pin diagram of an IRF540 transistor that involves three terminals D, G, and S.

The working operation of this transistor is very simple and when the drain and gate terminal gets shorts then people can obtain the proper output. There are many applications of this electronic device which are described below:

• Can be used as a switching converter
• Relay drivers
• Used as a high switching system
• Motor Drives

An IC is defined as an integrated circuit which is a combination of electronic circuit and devices on a single chip. It is produced to avoid the complexity of the circuit by which the overall efficiency and performance of an electronic device can be increased. In this project, CD4047BCN IC is used that has the potential to handle large inverter circuit and people can control the value of output voltage. Such kind of device is used in many computer systems, wireless networks, frequency counters and modems. The fundamental concept of an integrated chip is based on the logic gates that work on binary data such as 0 and 1.

CD4047BCN has the potential to operate in both mono-stable and a-stable mode and most electronic devices works on this IC. It used a capacitor and resistor to identify the output pulse width in the mono-stable state and frequency of output signal in the a-stable state. A mono-stable stage can be obtained when the circuit is triggered through low to high transition and it can be retriggered by applying a low to high transition. The voltage range for this IC is from 3 volt to 15 volt that uses low power transistor-transistor logic to obtain the proper output. There are numbers of applications of this integrated circuit such as timing circuits, time delay applications, frequency division, frequency multiplication, and envelope detection.

Above figure shows the connection process of CD4047BCN IC that have total 14 pins in which pin 7 is connected by a voltage source (Vss) and 14 is connected through another voltage source (Vdd). With the help of this IC chip, people can connect two or more electronic circuit with each other and it can be used in the inverter circuit to improve the efficiency of the system.

8.4 Diode (1N4007)

A diode is defined as a semiconductor device that provides a platform to transfer current in only one direction. The current will always flow from anode to cathode and it works as a rectifier that converts AC power into DC by using a combination of diodes. For this project, the 1N4007 diode is used because it has the potential to provide 1A maximum current and it also works a switch to trigger the applied voltage source. The power dissipation of such diode is very low that is 3 watt and most of the electronic devices use this component to handle the applied voltage source for different cycles. For example, in half bridge inverter circuit, there are main two diodes uses one is used for an upper half cycle and another is used for a lower half cycle. There are numbers of applications of this component which are described below:

• Used as a rectifier
• Used as a protection process for electronic devices
• Current flow regulators

Generally, diode works in the forward's bias when any electric power applies on diode then it works as a short circuit and in reverse bias, it works as an open circuit. It allows the electric current in only one direction due to which most the engineers use this component to convert AC power into DC power and this step is called as a rectifier. It has main two terminals for example anode and cathode that contains opposite charges on each other. The forward voltage of this diode is around 1.1 volt and reverse current is around 5 microamperes which are very less.

8.5 Potential resistor 

A potential resistor is defined as a three-terminal resistor with a rotating contact that forms a controllable voltage divider. When only two terminals of the potential resistor are utilized then it called as a variable resistor. It is measuring equipment which is used in electric engineer to determine the electric potential between two or more terminals in a circuit. In this project, a potentiometer is used to control and manage the value of resistor to get the better output AC voltage and it has the ability to handle the electric devices. People can adjust the value of resistor as per their requirement and they can find and minimum and maximum values of the resistor where the output voltage will move at a high level or low level.  

The main advantage of this component is that it is bi-directional that means it can be used in both direction and it does not need any external power source in order to operate their basic functions. Today, there are numbers of potentiometers available in the market with various applications that provide a way to control a current level and voltage value to obtain a high-level output voltage. Inverter circuit involves such kind of device to handle the applied input voltage and produce large AC power on the output side.

When this component is used in a circuit the connections are made to both ends and the position of the wiper provides an appropriate output voltage that will vary between the voltages stages applied to one finish of the resistive track. It also acts as a voltage divider that generates a variable output voltage which is directly proportional to the corporeal place of the wiper along the track.

8.6 Resistor

A resistor is defined as a passive element that implements electric resistance as a circuit part and in most, the electric devices resistors are utilized to decrease the flow of current. In this project, high-level resistors are used that adjust the signal levels and terminate the transmission line by which people can obtain more effective AC output. Most of the resistors are used in an electric and electronic circuit that opposes the flow of current which are implemented with integrated chips. According to tp ohms low, the value of the resistor is directly proportional to the applied voltage and a high-value resistor produce a large output voltage.  

A resistor is a passive element that does not require any external power source and it is a bidirectional electric component. There are many kinds of resistor available which are the following:

• Carbon composition resistor
• Film resistor
• Wire-wound resistor
• Semiconductor resistor

In all Electrical and Electronic circuit graphs and schematics, the most usually utilized image for a settled esteem resistor is that of a "crisscross" type line with the estimation of its obstruction given in Ohms, Ω. Resistors have settled obstruction esteems from short of what one ohm, ( <1ω ) to well more than a huge number of ohms, ( >10MΩ ) in esteem.

A capacitor is defined as passive electronic equipment which stores the electric energy in the form of charge. The impact of a capacitor is called capacitance that exists between two or more electrical conductors in a circuit. This component is used in this project to store a large amount of applied voltage and maintain the voltage value in the inverter circuit. It is observed that most of the capacitors involve at least two conductors which are separated by an electric medium. There are different kinds of materials uses in a capacitor, for example, plastic film, mica, oxide layers, glass, and paper.

Most of the capacitors are mostly used as parts of electrical circuits in various devices. When any capacitor is attached with a power supply that produces an electric field produced across the dielectric causing a net optimistic charge to gather on one plate and negative charges composed on the other plate. Capacitance is defined as the relation of the electric accuses on every performer to the possible differences them. The value of the capacitor is given by Farad or coulomb per volt and the capacitance of any capacitor is completely based on the outside region of the conductors. The main purposes of these capacitors are generally used in electronic devices to blocks DC current and pass only

There are two kinds of electrical charge, positive charge as Protons and negative charge as Electrons. At the point when a DC voltage is put over a capacitor, the positive (+ve) charge rapidly aggregates on one plate while a comparing and inverse negative (- ve) charge collects on the other plate. For each molecule of +ve charge that touches base at one plate a charge of a similar sign will withdraw from the - ve plate.

Conclusion

This project report is completely based on the inverter circuit and with the help of this report readers can enhance their knowledge in the area of electronic engineering. An inverter is one of the advanced technologies that convert direct current into an alternating current and motor drive is the best application of this technique. This report describes the concept of the inverter circuit and also analysis their advantages and disadvantages. There are mainly three types of the inverter circuit are used in the engineering field, for example, the square wave, the modified sine wave and pure sine wave inverter which are described in this report.

In which a literature review is conducted that evaluates different types of the inverter circuit with their operations. A step up transformer is used to enhance the value of output voltage because an inverter circuit provides low AC power. The main problem occurs with this technique is that it produce a very large amount of harmonic distortion due to which people are not able to obtain the effective output. People should involve the pulse width modulation technique in order to address the distortion losses by which the overall efficiency of the inverter circuit can be increased. 

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