Improvement Of Dynamic Voltage Regulator And Research Of The New Topology

With the coming of the information technology era, power consumers demand higher quality power supply. Power quality compensating devices based on Custom Power technology provide a novel method to solve the power quality problems. Dynamic Voltage Regulator (DVR) can restraint voltage sags, eliminate voltage harmonics and ripples, and have become a hot topic of researchers all over the world. The thesis first analyzes different compensation schemes of DVR and conventional DVR topology, designs and implements the DVR control system. The control system includes a digital control part and an analog control part. Experiments have been conducted to test the performances of DVR. The results demonstrate that the device has good dynamic and steady state performances, and has the capacity to improve the quality of the power supply of sensitive loads. Based on the experiments, this thesis also introduces some technology and methods to make the device more feasible and effective in application. A new voltage-sag detecting method was applied to improve DVR response speed. A new synchronous signal produce method was applied to avoid the unwanted signal caused by voltage flash. Based on the Electromagnetic Compatibility (EMC) theory, some EMC methods were applied in DVR and the device passed the EMC test under the National Standard. Compared to the conventional DVR, a new topology of single-phase DVR is introduced in this thesis, employing the pulse width modulation three-arm rectifier-inverter topology, and this thesis introduces the advantages of new topology DVR. This thesis builds up the model of the proposed DVR by using the switch function method, and by setting the common-arm control signal decouples the model into two independent subsystems-inverter subsystem and rectifier subsystem. The inverter portion is in series with the load so that the load voltage can be stepped up and down and has low distortion even if the input voltage is distorted or disturbed and the load is nonlinear. The feedback control strategies of the compensating voltage injection of DVR inverters are also analyzed. The rectifier portion regenerates the real power absorbed by the inverter portion from the dc link to the utility and it acts as an active power filter to compensate the reactive power and harmonic current of the load so that the input is unity power factor.In PSCAD this thesis tests the topology and control method under several different load and different voltage sag conditions. The effectiveness is demonstrated by the simulation results.