Synthesis of variable harmonic impedance in inverter-interfaced distributed generation unit for harmonic damping throughout a distribution network

This paper proposes a harmonic impedance synthesis technique for voltage-controlled distributed generation inverter in order to damp harmonic voltage distortion on a distribution network. The approach employs a multiloop control scheme, where a selective load harmonic current feedforward loop based on band-pass filter is developed in addition to the inner inductor current and the outer capacitor voltage control loops. Together with the use of multiple resonant integrators in the voltage control loop, the negative harmonic inductances and positive harmonic resistances are synthesized at dominant harmonic frequencies. Thus, the harmonic voltage drop and harmonic resonances throughout a distribution line with multiple shunt-connected capacitors can be effectively attenuated. Simulation and laboratory test results are shown to verify the performance of the proposed control method.