Comparison of four control methods to active power filters applied in accelerator power supplies

This paper proposes a hybrid filter structure consisting of a passive power filter and a DC active power filter (DCAPF) applied in high current, high precision and low ripple accelerator power supplies. The configuration of the power system with the DCAPF is firstly introduced. Then four control schemes to obtain the reference signal for the DCAPF control circuit is presented. For each method, the basic operation principle of eliminating output voltage and current ripples is analyzed in detail. Furthermore, the compensation characteristics of each method is discussed and compared. To verify the proposed circuit configuration and the control methods, the testing results of the practical field operation of the DCAPF with a 120kW accelerator power supply is introduced. By adopting the control method of detecting the load ripple voltage, the output current ripple factor and tracking accuracy of the accelerator power supply achieve 8.87×10^-6 (peak-to-peak) and 1×10^-4 respectively, which is very satisfactory for this kind of power supplies. The dynamic response of the accelerator power supply is also greatly improved through the application of the DCAPF.