Series Voltage Injection Impedance Measurement Device With Resonance Shunt

The series impedance measurement device (SIMD), which is connected in series between the grid and the inverter, is applied to inject a small voltage perturbation for the impedance measurement of the inverter. Yet, the rated fundamental current of the inverter under test, which flows into the SIMD, limits the switching frequency. For addressing this issue, SIMD with the
LC
resonance shunt is proposed. The fundamental current flows through the resonance branch, and SIMD withstands only a small current perturbation. Meanwhile, the fundamental voltage across the SIMD also is limited by the
LC
resonance branch. The capacity of SIMD is reduced by the proposed method, and the switching frequency thereby is increased. The high-frequency perturbation can be injected by SIMD with this proposed method. Furthermore, a control scheme is proposed to suppress the fundamental current through the SIMD and the oscillation between the SIMD filter and the
LC
branch. Finally, experimental tests validate the proposed topology and control strategy.