Active Power Filter Simplified Control Strategy

Author: Yushaizad Yusof, Nasrudin Abd. Rahim
Publisher: UKM Press
ISBN: 9789672429708
Weight: 0.240kg
Pages: 141
Year: 2021
Price: RM30

A new simplified control strategy for a single-phase shunt active power filter (SAPF) system is introduced. The SAPF circuit injects the compensated current comprising the harmonic and reactive current components of load current but with an opposite phase at the point of common coupling (PCC) of the line so that the source current will be free from harmonic distortion as well as in phase with the source voltage. Known as a nonlinear load equivalent resistance estimation control strategy, the source voltage should see a load as a near pure resistor. The control strategy features a simple configuration and has only two mathematical division operations. Therefore, the nonlinear load equivalent resistance can be determined by dividing an average DC load voltage over an average DC load current. Both quantities are obtained by filtering the absolute values of source voltage and load current respectively. A sinusoidal reference current is obtained by dividing the source voltage over the calculated equivalent resistance. 

Then, the load current is subtracted from the sinusoidal reference current to yield a compensated reference current. Next, the actual compensated current is sensed before being subtracted by the reference compensated current at a set point to produce an error signal. In order to compensate for the error signal, proportional (P) and proportional plus integral (PI) controllers are employed to yield a control signal. Then, the control signal is compared with a 20 kHz carrier signal to form pulse width modulation ( PWM ) gating signals that drive Insulated Gate Bipolar Transistor (IGBT) switches of H-bridge voltage source inverter (VSI) based SAPF configuration. The computer simulation was carried out for verification purposes. Based on the result analysis, the performance of the SAPF's simplified control strategy is excellent in mitigating the harmonic current and compensating the reactive power.