Zhong Yanru

A Novel Control Method for DSTATCOM Using Artificial Neural Network

In this paper, a new control method for distribution static compensator (DSTATCOM) using artificial neural networks (ANN) instead of the conventional direct controller is presented. A feedforward three-layer neural network is adopted to control the output compensating currents. This is accomplished by producing the appropriate switching patterns of the IGBTs. A backpropagation algorithm trains this network. A practical case with PSCAD/EMTDC is presented to check the proposed control performance. The simulation results show a better source current waveforms and a near unity power factor operation is achieved. This technique offers an alternative to the multi-pulse techniques that require complex magnetic circuit arrangements as well as to the conventional PI controller that the parameters are hard to determine

A novel DC-rail parallel resonant ZVT VSI for three-phase AC motor drive

This paper proposes a novel circuit of DC-rail parallel resonant zero voltage transition voltage-source inverter (DC-Rail PR ZVT VSI) for three-phase motor drive. In this circuit all switches are turned on or turned off under the zero voltage switching (ZVS) or zero current switching (ZCS) without high stress of voltage and current. Power ratings of the resonant components and auxiliary switches required are small. The control scheme is simple and less dependant on load current This paper gives details of the theoretical analysis, the rules of selecting the auxiliary switches and the commutation components and the control strategy of the proposed circuits. Finally, the validity and the efficiency of the circuit are tested and verified by experiment results. Some questions in practical application are discussed.

The comparative study of different methods about constructing switching table in DPC for three-level rectifier

According to the mathematical model of three-level rectifier based on direct power control (DPC) in dq rotating coordinates, the influence of all voltage vectors on active power and passive power were analyzed. All vectors switch tables and simplified switch table based on the fastest power rise were presented. The simulations about the presented switch tables and the conventional all vector switch table based on neighboring vector have been completed. The results show that the system stability based on the fastest power rise is better while loads could be changed rapidly. Simplified switch table based on the fastest power rise is the most simple. In all vectors switch table based on neighboring vector, the balance properties of neutral point voltage of rectifier in DC side is the best, the current in AC side and power are much smooth.

Research of the effect for relay protection based on STATCOM

This paper deals with the influence of the STATCOM to the relay protection. The fundamental compensation principle, the main circuit and control strategies of STATCOM are all proposed. Then the mathematical model of the distribution system with STATCOM is established, the three-phase short-circuit fault is analyzed. The EMTDC/PSCAD is used for analyzing the dynamic characteristics and protection of distributed power system during balanced fault. And then the instantaneous over-current protection, the time delay instantaneous over-current protection and definite time over- current protection are installed. The operation logic of the relay protective in distribution system with STATCOM is analyzed. Simulation results show that a STATCOM voltage controller can improve the stability performance of voltage and reduce the reactive and fault current, but the selectivity of the relay protection is impacted. To ensure the protective selectivity, a new five-step protection scheme is presented. The results of the dynamic simulation verify the validity of the presented scheme.

State-Variable Description and Analysis of a DC-Rail ZVT Inverter Feeding a Permanent Magnet Synchronous Motor

This paper proposes a state-variable description and analysis of a DC-rail parallel resonant zero voltage transition (ZVT) voltage-source three-phase inverter feeding a permanent synchronous motor drive. In this DC-rail ZVT inverter, consists of two major parts: a ZVT resonant converter and an three-phase inverter. The DC-rail inverter is operated at a higher frequency and has higher efficiency than traditional inverters. A three-phase 1.1 kW 20 kHz DC-rail ZVT inverter has been constructed and successfully tested to feed a permanent magnet synchronous motor drive based on a field-oriented control. State variable description and analysis, simulation and implementation of the whole system are described The experimental results not only validate the theoretical development but also prove that this new system has better performance than traditional systems

Combined Modulation and Harmonic Suppression

The output of pulse width modulation includes harmonics with invariable frequencies and invariable magnitudes, which are sources of conducted interference and load resonance. Based on the spectrum analysis of switching modulation and sinusoidal pulse width modulation (SPWM), frequency modulation and low frequency amplitude modulation are combined to make a nonlinear swing for the modulated frequencies, to spread the harmonics frequencies broader, to reduce the average amplitudes of various harmonics, and the experimental results are also given out in this paper