Design and Implementation of a Low-Voltage-Stress DC Impedance Measurement Device Featuring DC-Blocking Capacitive Voltage Division

The proliferation of power electronic devices in DC distribution networks, compounded by inherent supply instability and significant load fluctuations, presents substantial challenges for system stability analysis. As impedance analysis - the most expedient and widely adopted stability assessment method - requires prior knowledge of grid-connected equipment impedance characteristics, this paper investigates a DC-blocking capacitive divider-based impedance measurement apparatus with low voltage stress. This article proposes a topology of a DC distribution network impedance measurement device that can effectively reduce the voltage stress on the switching devices of a single-phase full-bridge inverter, enhance the effective modulation ratio of the device, and achieve electrical isolation between high and low voltages, allowing the disturbance source to exhibit current source characteristics. Subsequent analysis quantifies the proposed topology's advantages over conventional solutions through comparative assessment of loop gain and modulation performance. Finally, an impedance measurement prototype was implemented, with experimental results demonstrating close agreement between measured impedance characteristics and theoretical predictions.