SRF based current controller using PI and HC regulators for DSTATCOM with SPWM switching

Abstract

This paper presents Distribution Static Compensator (DSTATCOM) for compensation of unbalanced nonlinear load with dq0 current controller (using proportional integrator and harmonic compensation regulators) and Sinusoidal Pulse Width Modulation (SPWM) switching. The dq0 current controller is implemented in Synchronous Reference Frame (SRF) rotating at fundamental frequency and consists of Harmonic Compensation (HC) regulator (realized by sum of Sinusoidal Signal Integrators (SSI)) in parallel to Proportional Integrator (PI) regulator. The SSI provides high gain to specified tuned harmonic frequency and helps in improving filter current tracking performance for harmonic load current compensation. Each SSI in fundamental rotating dq0 reference frame can simultaneously compensate for two load current harmonics and thereby reducing the computational effort compared to SSI in stationary reference frame. Neutral current compensation, which is required for compensating unbalance in load, is carried out through 0-axis controller. SPWM switching strategy results in switching of inverter switches at constant frequency. This will simplify the design of inverter output filter (L/LC), reduces stress on switches and switching noise. Simulation studies of DSTATCOM load compensation using dq0 current controller with interface L and LC filters is carried out in Matlab/Simulink and the corresponding results are presented. Experimental studies are carried out on three phase DSTATCOM prototype using dSPACE 1104 with Matlab Real Time Interface (RTI).