A hybrid power quality compensator (HPQC) is proposed in this paper for comprehensive compensation under minimum dc operation voltage in high-speed traction power supplies. Reduction in HPQC operation voltage can lead to a decrease in the compensation device capacity, power consumptions, and installation cost. The parameter design procedures for minimum dc voltage operation of HPQC are being explored. It is shown through simulation results that similar compensation performances can be provided by the proposed HPQC with reduced dc-link voltage level compared to the conventional railway power compensator. The system rating can thus be reduced. It is also verified that HPQC would operate at the minimum dc voltage with the proposed parameter design via simulations. A hardware prototype is constructed and the experimental results show that through the proposed design, HPQC is able to provide system unbalance, reactive power, and harmonic compensation in cophase traction power with reduced operation voltage. The cophase traction power supply with proposed HPQC is suitable for high-speed traction applications.