Generation of SPWM Control Pulses for ZSI Using dsPIC33EP256MU810

Author Name(s): Punam C. Moundekar, Gaurav Goyal, Dr. M. M Renge
Author Email: pmoundekar94@gmail.com

Abstract

The aim of this paper is to present the design and implementation of an algorithm for controlling a 3-phase Z-source inverter (ZSI) using a digital signal controller (DSC), the complexity arises due to analog circuit can be eliminated by DSC algorithm also reduces cost, size of filter required, and improved overall inverter efficiency. In this paper, the power inverter i.e. ZSI are controlled by high performance dsPIC33EP256MU810 DSC that can achieve high-level inverter control, therefore this DSC is the heart of the system and it controls entire system. The DSC is programmed using embedded MPLAB software and it generates sinusoidal pulse width modulated (SPWM) pulses for ZSI for simple boost control and maximum constant boost control. To validate the proposed algorithm of ZSI MATLAB simulation and experimental results are presented.

Keywords:  dsPIC33EP256MU810, Maximum Constant Boost Control (MCBC), Sinusoidal Pulse Width Modulation (SPWM), Simple Boost Control (SBC), Voltage Source Inverter (VSI), Z-Source Inverter (ZSI).

Introduction

In the present situation, electricity plays a major role in day to day life. There is a peak demand of power supply. But during the case of power outage, power electronic devices like inverters play the major role to provide the continuous supply to the system. Therefore it is necessary to design the power inverter with low cost and higher efficiency. By using the power inverter DC power is converter to AC power at required output voltage and frequency. The power inverter is significantly used in hybrid power system and micro-grid system. The variable frequency & variable voltage supply is needed in industrial applications, such as single phase and three Phase Induction Motor & other rotating machines therefore, to vary the supply frequency and supply voltage, Voltage Source Inverter (VSI) is used [1-2]. Various new PWM techniques are developed for efficient power utilization. Now a day’s many types of pulse width modulating techniques have been proposed such as, Sinusoidal PWM (SPWM), Space Vector PWM (SVPWM), Selective Harmonic Elimination PWM (SHEPWM). However, these methods have some advantages as well as disadvantages. But in industry standard, the SPWM has proved to be most potential technique among all others. The SPWM technique for generating a fundamental sine wave that provides a higher voltage to the motor has lower total harmonic distortion (THD) [3]. However, these traditional voltage source inverters have conceptual and theoretical barriers and limitations as indicated in [4]. Therefore, to overcome these limitations of Voltage Source Inverter (VSI) new topology had been proposed known as Z-source inverter (ZSI).

Conclusion

The control pulses for SBC and MCBC for Z-source inverter is generated using dsPIC33EP256MU810 and to validate this experimentation was performed. The experimental results shows that the fundamental rms of line & phase voltage and THD are almost equal to calculated or simulated value with small error under tolerable limits. The experimentation was performed in laboratory at low voltage level. It is been observed that the boost is more in MCBC technique as compared to SBC with same modulation index in experimented results also. The DSC used is easy to program and control. The operating frequency of DSC used is 60MHz; hence the computation time required is also less. With this advantage this DSC can be used for closed loop operation also. This can be further extended using PV panels as a dc source operating in closed loop.

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