Simple four‐quadrant grid‐tie control scheme with unity power factor rectifier mode for single‐phase DC/AC converters

Abstract

This study proposes a voltage-oriented control scheme for four-quadrant grid-tie of a single-phase bidirectional direct current/alternating current (AC) voltage-sourced converter (VSC) to operate smartly at modes of unity power factor (PF) rectifier (UPFR), inverter or static var compensator. Given the possible harmonic-distorted AC grid voltage, the proposed scheme follows or filters the grid voltage to generate the appropriate current command template for minimising the harmonic current while synchronising with the grid. The following template is for the UPFR mode, whereas the filtered template is for the other modes. The scheme proposes a unique band-pass filter (BPF) to proceed with direct component generation for the filtered template. The proposed scheme further unifies the grid-tie inductor current-to-voltage conversion for the following emplate and the quadrature component generation for the filtered template into a differentiator. The control laws under the filtered and following templates are derived. The BPF and differentiator designs are introduced. Simulations and experiments are conducted with a one-cycle control full-bridge VSC to verify the proposed grid-tie control scheme and evaluate its performance. Nomenclature v grid AC grid voltage source R grid , L grid AC grid wire resistance, inductance v R grid , v L grid voltages across R grid , L grid i grid , i sgrid , i dgrid AC grid current, its assumed sinusoid, their difference i R , i sR , i dR rectifier mode input current, its assumed sinusoid, their difference i NL , i 1NL , i hNL non-linear load current, its fundamental, harmonic components g emulated conductance of UPFR mode v AC , V AC AC grid voltage vector on point of common coupling, its RMS value v out VSC AC output voltage vector v filter , v R f , v L f voltage across grid-tie filter, resistance, inducatnce of the filter k VSC AC voltage gain v 1 , V^1, V 1 VSC fundamental output voltage vector, its amplitude, RMS value θ 1 phase angle of v 1 * * , I 1 * * AC output voltage command for arm A, B of FB VSC v oA , v oB AC output voltage on arm A, B of FB VSC V oA , V oB average values of v oA , v oB f s , T s , d switching frequency, period, duty cycle over T s V DC DC grid voltage f c , ω c central frequency of the pass band of the BPF, its angular form f cL , ω cL corner frequency of the pass band of the low-pass filter, its angular form f cH , ω cH corner frequency of the pass band of the highpass filter, its angular form ζ L , ζ H damping ratio of low-pass, high-pass filters K L , K H gain in the pass band of low-pass, high-pass filters