Research And Application On Sliding Model Control Of Active Power Filter

Active power filter is a new power electronics device used to dynamically clearing up harmonic and improving power factor. By real time detecting harmonics in power line, then it generates the compensating current which is equal to harmonic current in amplitude and opposite in polarity, aim at improvement and advancement of electric quality. This kind of technique can compensate the harmonic and reactive power with variable both of frequency and amplitude, and it makes up the drawback of the passive power filter. Moreover, the compensation performance is not affected by impedance of power system, it has advantages as follows, fast response, high controllability and adaptability, etc. so, more and more importance is attached to it.The two key technologies of control system are harmonic current detection, and compensation currents control. They directly influence the capability of the APF. In this paper, we first analyse FFT and instantaneous reactive power in detail, and give the simulation model of the two methods. Then the mathematic model of shunt active power filter is established. Based on the model, the common sliding-mode control strategy of current control loop is deduced. The simulation results show that the effect is good. In order to reduce chattering and improve current tracking speed, a novel control strategy based on sliding-model variable structure control is proposed. Compared to traditional hysteresis current control method, this method has the high compensation precision and rapid response speed.According to the actual pollution status of some coal mine, a APF which compensation capacity is 400Kva, and can be used in 6KV high voltage system is designed. The output reactor, the parameters of DC-side voltage, DC-side capacitance and the output filter are decided. Simulation is carried out using Matlab, the simulation results verify that this APF has excellent compensating capability.In the end, a digital-analog hybrid control system which takes the double-DSP+CPLD as the core is designed, meanwhile the hardware system and software system have been introduced in detail. Results of the on-site operational experiences indicate that this active power filter is effective in field of harmonic prevention and has quick dynamic tracking ability and excellent robustness...