Decreasing of current harmonics via parallel active power filter using a new control algorithm

In this thesis, a Parallel Active Power Filter (PAPF) control mechanism via a novel Adaptive Harmonic Injection (AHI) algorithm is proposed in order to filter out harmonics generated by non-linear loads and carry out reactive power compensation. This is a three-phase Parallel Active Power Filter control mechanism that uses the AHI algorithm. The proposed AHI algorithm is a novel adaptive reference current extraction method that operates in the time domain. The AHI algorithm is based on the normalized least mean square method that is used to determine the reference current. The presented PAPF mechanism is composed of two stages. The first stage is the extraction of reference current to determine currents with harmonics. The AHI algorithm accurately estimates the proper amplitudes and phases of the harmonics online in order to extract the reference current. By accurately multiplying the estimated phase and amplitude information with sine and cosine values, a harmonic value is obtained in the desired amplitude and phase. In the second stage, the inverter switching signals are generated to inject the obtained harmonic currents to system in reverse phase. The gate signals required to trigger the inverter switches are obtained by means of current controller methods. In this study, gate signals for the inverter's switches were obtained using a hysteresis band current controller (HBAD). The system adressed was simulated by both AHI method and other Synchronous Reference Frame, Instantaneous Reactive Power Theory and Fast Fourier Transformation methods. In the example system where five different loads were handled; the loads were analyzed in order, and then 50% and 90% of the total load were taken into account. In the AHI method, THB decreased to 1.2%, 1% and 0.83%, respectively. In the other three methods, THB remained above the recommended value of 5% in IEEE-519 standards. Studies have shown that the AHI method proposed in this thesis is a very successful method for harmonic removal and reactive power compensation.