Simulation Of A Space Vector Pwm Controller For A Three-Level Voltage-Fed Inverter Motor Drive

ABSTRACT

Multilevel voltage-fed inverters with space vector pulse width modulation strategy are gained importance in high power high performance industrial drive applications. This paper proposes a new simplified space vector PWM method for a three-level inverter fed induction motor drive. The three- level inverter has a large number of switching states compared to a two-level inverter. In the proposed scheme, three-level space vector PWM inverter is easily implemented as conventional two-level space vector PWM inverter. Therefore, the proposed method can also be applied to multilevel inverters. In this work, a three-level inverter using space vector modulation strategy has been modeled and simulated. Simulation results are presented for various operation conditions using R-L load and motor load to verify the system model.

CHAPTER ONE

1.0                                                        INTRODUCTION

1.2                                             OBJECTIVE OF THE PROJECT

SVPWM aims to generate a voltage vector that is close to the reference circle through the various switching modes of inverter. Space Vector Pulse Width Modulation (SVPWM) is one of the most used techniques to generate sinusoidal voltage and current due to its facility and efficiency with low harmonic distortion. This algorithm is special, used in power electronic applications. This paper describes simulation algorithm of SVPWM using MATLAB/SIMULINK. SVPWM based Inverter are broadly classified to reduce the switching losses and harmonics in the system.

1.3                                         SIGNIFICANCE OF THE PROJECT

The space vector pulse width modulation (SVPWM), as a new kind of vector control technique, has the advantages of high voltage utilization, less distorted output, simple control method, etc. In this paper, the control technique is applied to three-phase photovoltaic (PV) grid-connected inverter system. It uses double loop control method combined with PI control technique. The simulation model of PV grid-connected inverter system is established in Matlab/Simulink. The simulation results show that the application of SVPWM technique effectively improves the dynamic performance of PV grid inverter system and the THD of grid-connected current is low.

1.4                                                 SCOPE OF THE PROJECT

The Space Vector Pulse Width Modulation (SVPWM) refers to a special switching sequence of the upper three power devices of a three-phase voltage source inverters (VSI) used in application such as AC induction and permanent magnet synchronous motor drives. It is a more sophisticated technique for generating sine wave that provides a higher voltage to the motor with lower total harmonic distortion. Space Vector PWM (SVPWM) method is an advanced; computation intensive PWM method and possibly the best techniques for variable frequency drive application. In SVPWM technique, instead of using a separate modulator for each of the three phases, the complex reference voltage vector is processed as a whole. Therefore, the interaction between the three motor phases is considered. SVPWM generates less harmonic distortion in the output voltages and currents in the windings of the motor load and provides a more efficient use of the DC supply voltage in comparison with sinusoidal modulation techniques. Since SVPWM provides a constant switching frequency; the switching frequency can be adjusted easily.

1.5                                              PROBLEM OF THE PROJECT

The main problems in PWM viz. harmonic distortion and switching speed are overcome by implementing the Space-Vector PWM (SVPWM) technique by using the Xilinx tool VHDL (Verilog High Speed Integrated Circuit (VHSIC) Hardware Description Language) and tested in programmable Integrated Circuits of Field Programmable Gate Array (FPGA). The results are provided along with simulation analysis in terms of hardware utilization and schematic, power report, computing time and usage of memory.