DESIGN OF SINGLE PHASE INVERTER USING ...

R. Senthilkumar et. al. / International Journal of Engineering Science and Technology Vol. 2(11), 2010, 6500-6506

DESIGN OF SINGLE PHASE INVERTER USING dsPIC30F4013 Mr. R.Senthilkumar, Associate Professor/EEE, Saveetha Engneering College, Thandalam, Chennai- 602105, India.

Prof. M.Singaaravelu, Professor/EEE, Saveetha Engneering College, Thandalam, Chennai- 602105, India. ABSTRACT This paper gives the design and implementation of a single-phase inverter that produces a symmetric ac output voltage of desired magnitude and frequency. A diode bridge rectifier is used to rectify the ac line voltage. Unipolar PWM technique is employed to control the output voltage magnitude and frequency. The digital signal Peripheral Interface Controller (dsPIC) dsPIC30F4013 of Microchip Technology is used for the implementation of the inverter. A DC to Ac voltage converter consists of four bidirectional switches that is used to convert the voltage. Sinusoidal unipolor Pulse Width Modulation is used for triggering the gates of IGBTs. The control circuit consists of the dsPIC controller and it is used to produce required SPWM for triggering the IGBTs.Tthe driver circuit isolates the control circuit from power circuit. The outputs for variable AC voltages are observed in the CRO. Key Words: Unipolar, PWM, dSPIC 1.

Introduction

Power Electronics is the technology associated with efficient conversion, control and conditioning of electric power by static means from its available input form into the desired electrical output form. Power electronic converters can be found wherever there is a need to modify the electrical energy form (i.e., modify its voltage, current or frequency). Therefore, their power ranges from some mill watts (as in a mobile phone) to hundreds of mega watts (e.g.in a HVDC transmission system).With “classical” electronics, electrical currents and voltage are used to carry information, whereas with power electronics, they carry power. Therefore the main metric of power electronics becomes the efficiency. An inverter is a circuit which converts a DC power into an AC power at desired output voltage and frequency. The AC output voltage could be fixed or variable voltage and frequency. This conversion can be achieved either by controlled turn on and turnoff devices (e.g. BJT, MOSFET, IGBT, and MCT etc.) or by forced commutated thyristors, depending on application. The output voltage waveform of an ideal inverter should be sinusoidal. The voltage waveforms of practical inverter are however, non-sinusoidal and contain certain harmonics. Square wave or quasi-square wave voltage maybe acceptable for low and medium power application and for high power application low distorted, sinusoidal waveform are required. The output frequency of an inverter is determined by the rate at which the semiconductor devices are switched on and off by the inverter control circuitry and consequently, an adjustable frequency AC output is readily provided. The harmonics content of output voltage can be minimized or reduced significantly by switching technique of variable high speed power semiconductor devices. The DC power input to the inverter maybe battery, fuel cell, solar cell or other DC source. But in most industrial applications, it is fed by a rectifier. This configuration of AC to DC converter and DC to AC inverter is called a DC link at network frequency is rectified and then filtered in the DC link before being inverter to AC at adjustable frequency. Rectification is achieved by standard diode or thyristors converter circuits and inversion is achieved by the circuit techniques. The objective is to produce a variable frequency and variable AC voltage. The various stages involved in achieving the aim are listed below.  Simulation of the power circuit using Matlab Simulink and the wave forms and outputs values are known.

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Designing IGBT power circuit to produce variable AC voltage frequency. Designing the control circuit to produce the sinusoidal Pulse Width Modulation (SPWM) for triggering the gates of the IGBT in power circuit. Designing the single phase rectifiers circuit to convert AC to DC voltage Designing the driver circuit to provide the isolation between the control circuit and power circuit. Fabrication of the designed circuit in sequential manner. Finally the fabricated circuit is tested and evaluated against the known standard values.

2. Related Works D.S.L.Simonethi et al (1994) studied theoretical aspects governing the equipment fed from a single phase line, control strategies and power topologies. The simplest diode rectifier used in the first stage of the AC to DC CONVERTER suffers from the power factor problem. So to overcome this problem DC to DC converter is used as a resistor, emulator and the power factor improvement. J.Drobnik (1994) studied the exciting possibility of the connector less power transfer. Since both the inverters and the converters contain transformers. Those transformers serve as a media for the magnetic coupling between the back plane and removable cards. To achieve this transformer primary will located in the primary and the secondary on the system card with the Ac to Dc converter. The energy can then be coupled through the magnetic field only without metallic connection. Drobnik et al (1999) studied the advantage using the high frequency power distribution architecture (HFAC).For personal computer power requirement. Their study deals with issues such as cost, efficiency, form factor and reliability. It has been determined that single phase voltage power architecture meets the requirement for the processors. P.K.Jain et al (1999) studied the advantage of using HFPDA for the telecommunication system. It advantage of the connector less power transfer improves the overall system efficiency, increased system reliability due to inherent short circuit protection at the power interface and limited power transfer to the load and compatibility with electrical connector less interface using the fiber optical connector for the signals. M.Qiu et al(2002) studied an Ac VRM topology for high frequency Ac power distribution system, which has the power factor very close to unity, low total harmonic distortion in the input current, zero voltage, switching under all load conditions and low voltage stress across of the active switch. This topology is very attractive for the point of use HFAC to DC converter in HFAC distribution system to power the future desktop personnel computers. The steady state performance of the proposed converter in terms of displacement, power factor, total harmonic distortion and power factor of the input resonant current and voltage stress of the ac switch are studied. James M.Simonelli et al (1992) studied and analyzed that, the complete Ac to Dc conversion requires an external EMI input filter to get rid of the high frequency noise generated by the converter. 3. Architecture of Single Phase Inverter

Fig 3.1 Block Diagram of Single Phase Inverter

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R. Senthilkumar et. al. / International Journal of Engineering Science and Technology Vol. 2(11), 2010, 6500-6506 The block diagram of the whole circuit is shown in figure 3.1. The operation starts by taking the 230v 50Hz AC from the main supply. The 230v AC is given directly given to the Power circuit. The 230v AC voltage is stepped down to 12v using 230/12v step down transformer to provide the supply to the driver circuit and the control circuit. The block diagram has three modules.  Power Circuit Module  Control Circuit Module  Driver Circuit Module 

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Power Circuit Module The power circuit module consists of a rectifier unit along with the filter and the IGBT bridge circuit. The Circuit contains 2MBI 200L-060 as a power IGBT. IGBT is used as a switch due to high power applications. IGBTs are arranged as a bridge circuit. The input to the power circuit is obtained from the 230v supply main. Depending on the voltage of the output required at the output the gates of the IGBTs are triggered with proper pulse sequence. The gate pulses are obtained from the control circuit. Control Circuit Module The control circuit module of the work consists of the dsPIC30F4013 controller circuit. The control circuit is used to produce the PWM pulses and the pulses that obtained from the controller is given to the driver circuit such that the inverter IGBTs gates can be triggered on and off Driver Circuit Module o The driver circuit module consists of the buffer IC LM358, SG3524, 4151, 4518, 4081 IC and the Optocoupler. o The input control signal from the microcontroller (0-5V) is buffered using an LM 358 Operational amplifier IC With unity gain. The input voltage to the motor is varying using PWM Pulses. Here we have used SG3524 as a PWM Generator. It also varies the ontime of the PWM Pulses according to the control signal from the controller. o The input control signal is fed to a 4151 to convert the corresponding voltage to a frequency. The frequency will be 2KHZ for 5V input signal. o The generated frequency is then divided by a 4518 by 20 times to get a 100HZ frequency. It is then fed to 4013 (D type Flip Flop) to convert it into a 50HZ signal for the Positive and Negative Half cycles. o The generated PWM and the frequency is mixed using an 4081 AND Gate. Finally the output of the amplifier is given to the collector and emitter of the IGBTs Power Circuit The power circuit of Single Phase Unipolor inverter consists of four bidirectional IGBT arrangedin bridge form. The circuit diagram of the power circuit is shown in figure 3.2

Figure 3.2 Power circuit

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The circuit diagram consists of four distinct IGBTs such that they are connected as the bridge circuit. The input to the circuit is the 220v DC supply from the rectifier unit. The IGBTs are triggered accordingly such that the AC output voltage is obtained at the output. The operation of the circuit is as follows. First the IGBT S1 and S4 are turned on by triggering the gate of the IGBT. During this time the input supply is 220v DC and at the output the 220v is applied across the load. The current starts from the supply positive, S1, S2, load and to the negative of the supply. The conduction path for the first cycle of operation is shown in figure 3.3.

Figure 3.3 Current conduction when S1 and S4 is ON

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During the next phase or the cycle the IGBT S2 and S3 are turned on by giving trigger pulse to the gate of the IGBTs. During this period the input voltage is applied at the output but in the negative direction. The current conduction starts from the supply, S2, S3, load and to the negative of the supply. The current conduction is showed in the figure 3.4.

Figure 3.4 Current conduction during when S2 and S3 is ON

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As the two cycles continue the positive and the negative voltage is applied at the load and the current direction changes in the two cycles. As the current direction changes the alternative voltage is obtained at the load thus converting Dc voltage to AC voltage.

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R. Senthilkumar et. al. / International Journal of Engineering Science and Technology Vol. 2(11), 2010, 6500-6506 4. Experimental Setup 4.1 Simulation Diagram The Simulation diagram drawn using Matlab Simulink is shown in Figure 4.1 The simulation diagram consists of the following blocks  Rectifier Circuit  IGBT bridge Section  PWM Pulse Generator  Filter and Load Circuit 4.1.2 Rectifier Circuit The rectifier circuit consists of the four identical diodes which are connected in such a way to from the bridge network. The input to this block is given from the voltage source block of value 220v and 50Hz. 4.2.2 IGBT Bridge Section  The next block is the IGBT block. We use four IGBTs which are connected to form a bridge circuit. The input to the bridge is the output of the filtered rectified DC voltage. The gates of the IGBTs are triggered using the PWM pulses. 4.2.3 PWM Pulse Generator The PWM pulse generator block generator block generator block generates the four PWM pulses and these pulses are given to the gates of the IGBTs for turning on and turn off.

Fig 4.1 MATLAB Simulink of the circuit

4.2.4 Filter and Load circuit The last block is filter and load circuit. The outputs from the IGBTs have some harmonics. The harmonics can be filtered using filter circuit. The load is connected to the filtered output. 4.3 Components in Driver circuit The components used in the driver circuit are

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R. Senthilkumar et. al. / International Journal of Engineering Science and Technology Vol. 2(11), 2010, 6500-6506  Power Supply  Buffer  PWM Regulator  Voltage to Frequency Converters  Frequency Divider  Frequency and PWM Mixer  Isolators  Rectifier unit 4.3.1 Power supply: It consists of a step down transformer and Bridge rectifier with filters and regulators to provide supply to the rest of the Ics used in the circuit. 4.3.2 Buffer: The input control signal from the microcontroller (0-5V) is buffered using an LM 358 Operational amplifier IC With unity gain. 4.3.3 PWM Regulator: The input voltage to the motor is varying using PWM Pulses. Here we have used SG3524 as a PWM Generator. It also varies the ontime of the PWM Pulses according to the control signal from the controller. 4.3.4 Voltage to Frequency Convertor: The input control signal is fed to a 4151 to convert the corresponding voltage to a frequency. The frequency will be 2KHZ for 5V input signal. 4.3.5 Frequency Divider: The generated frequency is then divided by an 4518 by 20 times to get a 100HZ frequency. It is then fed to 4013 (D type Flip Flop) to convert it into a 50HZ signal for the Positive and Negative Half cycles. 4.3.6 Frequency and PWM Mixer: The generated PWM and the frequency is mixed using an 4081 AND Gate. 4.3.7 Isolation: The mixed output is then given to an opto coupler for isolation and is finally applied to the gates of the IGBT through a current amplifier section. 4.3.8 Rectifier unit: The input AC Signal is rectified and fed to the IGBT through a Time delay circuit. This time delay is required to prevent the motor from high voltage due to any false triggering of the IGBT. 5. Components Used Table 4.1 List of components used

NO 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

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NAME OF COMPONENT BRIDGE RECTIFIER FILTER CAPACITOR Microcontroller IGBT Output filter inductor Output filter capacitor Power resister Buffer amplifier Voltage to frequency converter BCD up counter PWM regulator Mixer Opto coupler Supply transformer Voltage Regulator

SPECIFICATION BR1010 1000µF,600V dsPIC30F4013 2MBI-200L-060 2mH 1.5pF,2000V 500W,100Ω LM358 XR4151 CD4518 LM3524 CD4081 MCT2E 4x230/12V IC7812

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R. Senthilkumar et. al. / International Journal of Engineering Science and Technology Vol. 2(11), 2010, 6500-6506 5.1 Simulation Waveforms The input and output obtained from simulating the circuit is shown in Figure 5.1

Figure 5.1Simulation Waveforms of input and output voltages

6. Conclusion The design and implementation of a single-phase inverter that produces a symmetric ac output voltage of desired magnitude and frequency. The digital signal Peripheral Interface Controller (dsPIC) dsPIC30F4013 of Microchip Technology is used for the implementation of the inverter The Inverter consists of four bidirectional switches that is used to convert the voltage. Sinusoidal Unipolor Pulse Width Modulation is used for triggering the gates of IGBTs. The control circuit consists of the dsPIC controller is used to produce required PWM signal. The voltage and the frequency can be varied by using connecting the controller to the computer. The simulation of the circuit is done using Simulink of Matlab. The outputs for variable AC voltages are observed in the CRO. The Simulation waveforms and the output waveforms are compared against the standard values. 7. References [1] [2] [3] [4] [5] [6] [7] [8]

Bose.K.B (1997) “Power Electronics and Variable Frequency Drives”, IEE Press ISBN 0-7803-1061-6, New York. B.R.Gupta and V.Singhal(2002),”Power Electronics”, Tata McGraw Hill Publications, Delhi Cyril W.Lander(1981) “Power Electronics”, McGraw-Hill, MaidenHead. John D.Ryder “Engineering Electronics with Industrial Applications and Control”, Second Edition Muhammad H.Rashid “Power Electronics-Circuits, Devices and Applications.” Paul Horowitz & Winfield Hill (1980) “The Art of Electronics” Cambridge University Press, Second Edition. P.S.Bimbra,”Power Electronics”, third edition, Khanna Publishers. S.K. Datta (1985)”Power Electronics and Control”, Reston Publishing Company, New York.

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