Abstract
Recently, due to the rapid progress in high technology industry, much better power quality is required to meet the need of highly accurate automation machinery. As a result, how to eliminate the harmonics to achieve high power quality in a rectifier has been discussed in many literatures. Owing to the fast response, easy implementation and with fixed bounded errors, the hysteresis current controller has been widely used in various applications. However, the variable switching frequency has rendered the increasing switching loss and the harder design of the filter. Hence, how to achieve fixed switching frequency control is one of the hot topics in the literature. In fact, it is the main object of this thesis to propose a novel control strategy of constant switching frequency hysteresis current controller.First at all, the operation principle of the traditional hysteresis current controller and the corresponding controllable condition under different output DC voltages are introduced. The inequality constraint of the controllability is obtained through the derived model. Second, the closed form expression of switch turn-on time and the corresponding partition into proper sequence are obtained to achieve constant switching frequency and with fixed error bound at the same time. Third, by modifying the formula derived before, the error due to transient and nonideal switch characteristics can be corrected at the same time while calculating the turn-on time. By this way, one can not only avoid the accumulation of the error but also can reduce unnecessary computing time for additional error correction. Fourth, the control strategy is further refined to reduce half of the computing time and make the current error distribution more uniformly inside the error bound. Hence, one can achieve a better performance without increasing the switching frequency. Finally, a prototype is constructed and some experimental results are presented for verifying the feasibility of the proposed controller.