Analysis and control of unified active power filter.

摘要

The combined series and shunt active filters have been proposed to alleviate the power quality problems at the demand-side power systems. However, the conventional approach for the control of the combined active filter systems have resulted in large operating capacity of the shunt active filter because reactive power compensation involves only the shunt active filter. Furthermore, the harmonic mitigation problems are handled mainly by indirect harmonic compensation schemes rather than direct harmonic isolation schemes.; This thesis presents the analysis and control of Unified Active Power Filter (UAPF) and proposes a novel concept of load reactive power compensation involving both the series active filter and the shunt active filter. The thesis also applies discrete-time sliding-mode control technique to enhance the performance of the combined active filter system in terms of fast dynamic response and effective solution to harmonic mitigation problems. The thesis also presents simulation and experimental results to provide verification of the proposed UAPF concept.; The involvement of series active filter for reactive power compensation is achieved by controlling the phase difference between the load voltage and the utility voltage. The complete steady-state operating characteristics of UAPF are analyzed with the identification of the different operating modes of UAPF and the analysis of active and reactive power handled by the active filter components.; The performance of UAPF to meet the stringent power quality standards are realized by applying discrete-time sliding-mode control schemes for the load voltage regulation and the active power factor correction. The control algorithms are developed to track a given load voltage and line current reference signals respectively. The effect of computational delay in DSP implementation is studied extensively and the control law is designed with the consideration for the computational delay. The systematic approach for the design of DC link voltage regulation is also presented in this thesis.; A prototype experimental setup including the power circuit for UAPF and DSP based control circuit is built to implement the control and to verify the performance characteristics of UAPF. A real-time control algorithm is developed and is implemented on a DSP TMS320C40 system with PWM implementation by DMA without the intervention of CPU.; The operation of UAPF at the optimal operating point is shown to reduce the ratings of the shunt active filter and to improve the efficiency. With the discrete-time sliding mode control, the compensation characteristics of UAPF are shown to meet the stringent power quality standards. (Abstract shortened by UMI.)