Research On Hybrid Active Power Filter In Low Voltage System

With the improvement of science and technology, more and more nonlinear power electronic devices have been rapidly developed and been widely applied. These nonlinear power electronic equipments increase the factories and mines production efficiency, liberate the productive forces and create the economic value. However, at the same time these devices also bring a lot of problems about power system, one of the problems is penetrating that the harmonics inject into the grid these devices produce, affect other electric equipment.The harmonic that nonlinear load product can be compensated by passive power filter (PPF),active power filter (APF) and hybrid power filter (HPF). Therefore, more and more scholars research on the hybrid power filter (HPF) topology. Especially the hybrid active power filter (HAPF) composed by active power filter and passive power filter have been rapidly developed and been widely applied. This kind of the HAPF has the advantages of both passive power filter and active power filter. The hybrid active power filter can reduce switching element voltage,power grade and economic costs, solve the problem of filtering properties and series-parallel resonance that happen to system impedance for passive power filter.In this paper the hybrid active power filter for low-voltage system links directly with power grid, which is comprised of the parallel active power filter and the single tuning passive power filter. The compensation characteristic of the single tuning passive power filter,the parallel active power filter and the hybrid active power filter is verification based on the MATLAB/Simulink and experimental method.When the single tuning passive power filter used alone, the simulation and experimental results show that the proposed filter can compensate the harmonic well. However, the passive power filter parameter in the experiment is not totally same as the designation parameter, which makes experiment filter effect insufficient ideal. When the active power filter used alone, it can compensate harmonic current that the nonlinear load generates, and the total harmonic distortion (THD) drops to below 5%, the harmonic content of 11^th harmonic down to below 2%. When the hybrid active power filter is used, it can compensate the harmonic current produced by the nonlinear load, making the total harmonic distortion dropped to below 5%. However, due to the same parameter problem of in 11^th passive power filter, 11^th harmonic current only drops by 25%.Through the MATLAB/Sinmulink and experiment the hybrid active power filter can achieve ideal filtering effect, reduce the capacity of active power filter,cut down the cost of the filtering system.