Design of a Compensation Network for an LLC Power Converter Applied to Motor Drive Control Systems under Rapid Load Variations

The paper focuses on the design of a Type II compensation network for a 500 W half-bridge LLC converter to stabilize a 60 VDC output voltage supplied to a motor under rapidly changing load conditions. By applying the K-factor method in combination with SIMPLIS-based simulation, the design parameters of the compensation network are selected and verified, enabling the system to achieve a crossover frequency in the range of 3.89 kHz - 4.6 kHz and a phase margin of 28.3°–37° across an input voltage range of 370-410 VDC. Experimental results show that when the load current changes abruptly from 0 A to 9 A, the output voltage undershoot is limited to 938 mV, while the overshoot during load removal is 705.5 mV. With the transient voltage deviation maintained below approximately 2% and the output voltage returning to steady state without sustained oscillation, the proposed compensation network improves the load-transient response and helps preserve the regulated DC output-voltage quality within the investigated operating range. These results support the feasibility of the compensated LLC converter for regulated drive-supply applications and provide a basis for further power-density improvement in future work.