Study On Active Power Filter Based On Digital Frequency Trap

With more and more non-linear loads used in our country's power system, especially in the recent 20 years, various kinds of power electronic equipments application rapidly, harmonic current that pours into electrical network is day by day serious, and the power quality deterioration turned more and more serious. How to improve the electrical energy quality, harmonic suppression to power supply system, is suspends in front of people's practical significance topic.The numerous related literature, have provided the important theory and exploration for the product development. Especially in Shandong University master's paper "100kvar Parallel Hybrid Active Power Filter ", after giving main work principle and the control policy, developed a 100kvar parallel hybrid active power filter's prototype finally. In experiment, has made the favorable effects. However, its harmonic detection circuit is based on the instantaneous reactive power theory. from Shandong University master's paper "Parallel Hybrid Active Power Filter's Research", we know, if uses the frequency trap separation circuit, not only may achieve better filtering performance compared with the instantaneous reactive power theory, moreover may obtain faster transient response speed, and has the structure succinctly, easy to realize, the low cost, run reliably and so on many merits. Parallel hybrid active power filter based on the frequency trap, and the voltage source closed loop control strategy, and the digital processing technology, have the practical significance very much.Because main circuit is identical with "100kvar Parallel Hybrid Active Power Filter", this paper focus on design of control system. Entire control system include two major parts:hardware and software.This article first introduced control system's hardware design. It Including various voltage and current sampling circuit, supply current AD transform circuit, control core circuit, DA transform circuit, following control circuit, RS485 communication interface circuit and so on. The circuits' structure, work principle, component's function, component's selection, are mainly studied in details. This article then introduced control system's software design. The DSP software are divided into two parts roughly:(1) digital signal processing partThis part of software module includes:Digital phase-lock, digital frequency trap, overload control system, DC Bus Balance adjust system, serial communication. The digital frequency trap is difficulty to realize, Start with analog prototype circuit, analysis its principle of work, obtained the practical digital frequency trap, and has made favorable effects.(2) logical control partThis part of software module includes:various electricity parameter's computation, logical control to start and stop the device, the protection logic, receiving and delivering in serial communication, and the human-machine interface. This subprogram's timely request is relatively low. The RS485 serial communication is also software's important component, in this topic, has used internationally standard communication protocol-MODBUS protocol, the protocol and the software realization are studied.After the control system design and debug, experiments on the manufacture of PHAPF were carried on. We got favorable effects on the sieve harmonics and transient response according to the experiment.