Study On Three-level Active Power Filter With Instantaneous Reactive Power Theory And One-Cycle Control

With applications of power electronics equipments, power pollution drawn from nonlinear loads such as switching mode power supplies, commercial lighting, ovens and adjustable speed drives, results in the degradation of power quality (PQ) in the distribution system. The non-sinusoidal balanced or unbalanced currents generate harmonics and reactive power, which influence on not only the efficiency of the power system, but the operation of the power grid as well. Therefore, more and more scholars devote to research on ways to improve the power quality. Active power filter (APF) is one of the effective means for power quality enhancement. As one member of the APF family, shunt APF is connected in parallel to the power grid and cancels the reactive power and harmonics from a group of nonlinear loads so that the resulting total current drawn from the ac mains is sinusoidal. In this thesis, one-cycle controlled APF with three-level converter and ip-iq detecting method is presented for the first time.Taking advantage of the ip-iq detecting method based on the instantaneous reactive power theory, one-cycle controlled APF presented in this thesis can compensate harmonic component, reactive power component, harmonic and reactive power component altogether, respectively. Moreover, even under the distorted or asymmetric three-phase power source voltage working condition, the power source currents are sinusoidal when compensated by this APF. In addition, the three-level diode-clamped converter is used as the power stage for this APF, which provides more than two voltage levels and less distorted waveform. Hence, it offers many benefits for higher voltage and higher power applications.Based on the analysis of circuit configuration, control reference signals generation and control strategies for this APF, the control functions are deduced and the simulation model is developed. Furthermore, the circuit simulation is carried out under different working circumstances, such as symmetric three-phase power source voltage with or without waveform distortion, asymmetric ones without waveform distortion, for different compensation objectives including harmonic component compensation, reactive power component compensation, harmonic and reactive power compensation altogether. And the theoretical analysis and simulation results verify that this APF can effectively eliminate harmonics and compensate reactive power according to different compensation targets and functions well even under the distorted or asymmetric...