DC chopper based test circuit for high voltage DC circuit breakers

High voltage DC circuit breakers (DC CB) are essential components for the future DC transmission grid. One of the challenges after manufacturing the DC CB is testing it and confirming the working of the DC CB under different conditions. In this paper, a 320kV, 1.5kA test circuit is proposed for testing DC CB in conditions very close to real DC transmission systems. In the proposed circuit topology a chopper is used to regulate the DC voltage. A DC capacitor bank is used to provide the energy required during the fault replication. In the test circuit the initial DC voltage is boosted by 12% which results in a DC voltage drop of 88% at the end of discharge period. The test circuit keeps the voltage at nominal level as soon as the fault is cleared to enable testing dielectric stress. The proposed test circuit is modelled using PSCAD and the simulation results are shown which confirm the working principle of the proposed test circuit.