High Power DC Chargers with Extended Negative-Sequence Current Control for Load Balancing in Low-Voltage Networks

Public three phase low-voltage networks are capable of feeding high power DC chargers. For charger installation in remote network locations, active front-end (AFE) rectifiers using voltage source converters ensure network power quality. A modular parallel current control decoupled by a multiple complex-coefficient filter is proposed to achieve low negative-sequence and harmonic current emission. Furthermore, the AFEs capability of compensating network load unbalance is discussed. As unbalance compensation significantly increases DC-voltage ripple, the proposed current control is extended by a parallel third harmonic current control module to optimize DC-capacitor dimensioning. Simulation and experimental tests validate the proposed current control concept.