Optimized FPGA Implementation of PWAM-Based Control of Three—Phase Nine—Level Quasi Impedance Source Inverter

Syed Rahman,Lazhar Ben-Brahim,Atif Iqbal,Mohammad Meraj

doi:10.1109/access.2019.2942210

Syed Rahman, Lazhar Ben-Brahim + Show 2 more

Open Access

https://doi.org/10.1109/access.2019.2942210

Copy DOI

Abstract

Inherent buck–boost capability, reduced component count, controlled power injection and multilevel operation are some of the advantages which makes cascaded qZSI popular for integrating the generated solar energy with the utility grid. Phase–Shifted Carrier PWM (PSCPWM) and Pulse Width Amplitude Modulation (PWAM) are the most popular techniques for achieving multilevel qZSI operation. Generally, closed loop control implementation of three – phase qZSI system consists of large number of slave controllers (placed locally for voltage control) and one centralized master controller (for grid integration or load current control). Since the aim is to control single system with this highly distributed control structure, issues of clock pulse and interrupt signal synchronization, hardware and software redundancy are common in these implementations. This limits the utilization factor and step size of these control boards. To address these issues, either more optimized solutions must be suggested, or distribution of control structure must be reduced. In this paper, closed loop control of nine – level three – phase qZSI system is implemented using single FPGA control board thereby eliminating above said problems. Since, PWAM control algorithm is more complex than PSCPWM, FPGA based implementation for PWAM control is discussed. Critical implementation processes consisting of DAC – ADC interfacing, FPGA code per unitization, PI Controller realization and different clock pulse utilization are presented. For highlighting and comparing the resource consumption, PWAM and PSCPWM modulation are compared in terms of device utilization. Transient analysis and control algorithm are presented and validated during both starting and load transient conditions by means of simulation results. Finally, hardware results of these modulation methods are discussed and analyzed.

Highlights

The most common configuration for feeding renewable power to the utility grid consists of two-stage conversion i.e., DC-DC converter connected to an inverter [1], [2]
DC-DC converter receives the variable energy generated from solar panels and converts it to a form with fixed dc voltage using MPPT algorithms [3]–[5]
Impedance based inverters are categorized into Z Source Inverter (ZSI) and quasi Z Source Inverter. qZSIs have advantage of continuous input current which helps in minimizing the component size [6]–[10]

Summary

INTRODUCTION

The most common configuration for feeding renewable power to the utility grid consists of two-stage conversion i.e., DC-DC converter connected to an inverter [1], [2]. Cascaded multilevel qZSI is discussed in literature It offers all benefits of multilevel operation including achievement of higher voltage and power ratings, lower dV/dt and lower THD [11]. S. Rahman et al.: Optimized FPGA Implementation of PWAM met when solar PV panels are connected at input of qZSI modules [12]–[16].For achieving multilevel operation, many modulation methods are used for conventional multilevel inverters [17]. FPGA technology has surfaced as one of the most popular platforms for implementation of real-time control algorithms for experimental setups They can work up to 100MHz clock frequency and can accommodate more than 10 million equivalent gates in addition to other resources provided like DSPs [30], [31].

SYSTEM DESCRIPTION

CONTROL ALGORITHM The control algorithm must meet the following requirements:

HARDWARE RESULTS