Novel transformer active filters
Novel transformer active filters are proposed to obtain high attenuation of voltage or current ripple without deteriorating the transient response of the system considered. Experimental results show that the scheme gives good steady-state performance of the power supply. >
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/spl times/10/sup -6/ (peak-to-peak) and 1/spl times/10/sup -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.
A Generalized Firing Angle Controller Using Phase-Locked Loop for Thyristor Control
A generalized firing angle controller using a phase-locked loop, for control of thyristors is described. Different types of firing angle variation characteristics are possible because of the generalized phase detector used in the circuit. The controller can operate over a wide range of supply frequencies and is immune to the transients and harmonic distortions in the supply voltage. Also changes in the supply voltage amplitude do not have any effect on the firing angle. The same circuit can be used to provide firing pulses for three- or six-element thyristor configurations. The scheme can be successfully used for thyristor converters and cycloconverters.