Power quality enhancement of distribution grid using a photovoltaic based hybrid active power filter with three level converter

Abstract

This paper employs a second-order sequence filter (SOSF) and proportional–integral (PI) controller to control a hybrid active power filter with photovoltaic (HAPF-PV) through three-level neutral point clamped (NPC) converters. The PV system uses perturbation and observation (P&O) method to track the maximum power point and drive a boost DC/DC converter. A reference signal of a shunt active power filter (SAPF) is generated by estimating the real (not imaginary) term of the polluted load current. The estimation of this term relies on adopting a SOSF and sampling that its input at points the load voltage crosses the zero. SAPF is responsible for compensating grid current harmonics. The suggested approach helps obtain fundamental real term of the polluted unbalanced load current with good accuracy and minimal mathematical computations. In addition to improve power quality, this system can produce green output using the PV arrays connected to the HAPF via a DC-link. HAPF-PV has advantages of power quality enhancement and distributed generation simultaneously. Also, in this system, three-level NPC converters are used in order to reduce harmonic currents injected into the grid by HAPF-PV. Escalating the converter output voltage had led to obtaining output sinusoidal waveform of the converter, and so in this paper, a three-level NPC converter with a neutral point is used to reduce harmonics due to PWM switching. Besides, a series active power filter (SeAPF) is presented for series compensation such as voltage sag/swell. The scheme was implemented in MATLAB considering various types of disturbances including the PCC voltage sag/swell, unbalanced load and changes in irradiance.