Analysis and Control of Three-Phase Shunt Active Power Filters

• Main Authors: Kuo, Hung-hsi, 郭鴻熹
• Other Authors: Yeh, Sheng-nian
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/06298344311625324905

博士 === 國立臺灣科技大學 === 電機工程系 === 89 === This dissertation presents the design and implementation of three-phase shunt active power filters. The principle of operation of active power filters is to generate compensating current into the power system for cancelling the current harmonics generated by nonlinear loads and correcting power factor of input source. The determination for compensating currents is conducted by firstly sensing the currents from the nonlinear loads. The direct and quadrature components of the compensating currents are then obtained from the corresponding load current components in the rotating frame by mean of a digital low-pass filter. Using the proposed determination method needs no calculation for the instantaneous real and reactive powers on the load side. This will thus results in pronounced reduction of calculation procedure and sensor component cost. A novel and simple analytic model is proposed to a three-phase active power filter system for design and implementation of the active power filter controller. The voltage decouplers and pole-zero cancellation are used in the current regulators to simplify the current control plant to a first-order delay type. This simplification is conducted by considering the delay times caused by the low-pass filter of reference current calculation circuits, line inductors of active power filter and feedback circuit of dc-link voltage. From the derived analytic model, the cut-off frequency of low-pass filter and controller parameters can be appropriately determined to increase the harmonic current compensating capability of active power filter and improve the dynamic response of dc-link voltage. In addition, the active power filter of centralized, non-common dc-link voltage topology designed with small-rated power modules are adopted to the proposed paralleled active power filter system. The compensating capacity and utilization rate of the parallel system can be flexibly increased by mean of suitable switch in and off control. A current distribution controller is used to determine the required number of parallel module and calculate the compensating current commands for each module. The compensating weighting factor for each module can be computed according to the current sharing control strategy. Applying the proposed control approach, the parallel operation system has the advantages of easy maintenance, good expandability as well as higher reliability and efficiency. The performance of the proposed system is first simulated by digital computer. A personal-computer based digital control is used to implement the system. A 2.5 kVA single module and two 2.5 kVA module parallel operation prototype are then built to evaluate the performance of the single active power filter and the parallel operation system, respectively. The proposed system performances have been shown to possess fast current harmonic compensation, low input current harmonics, near unity input power factor and low dc-link fluctuation voltage with balanced and unbalanced nonlinear loads.