Chunlin Guo

The simulation research of STATCOM based on cascaded multi-level converter

Cascaded multi-level converter based STATCOM (CMC-STATCOM), with a topology of modular-cascaded structure, has a wide prospect of applications in both transmission and distribution system. Under the background of application of STATCOM in high voltage power grid, there are many advantages of CMC-STATCOM compared with other kinds of STATCOM. On the basis of mathematical model of main topology, the states feedback decoupled reactive power control strategy based on the d-q coordinate system is studied in this paper, together with the application principle of carrier phase shift PWM modulation method in CMC. The balance of DC bus voltage is a key factor to the stable operation of devices. In this paper, the hierarchical control method is used to achieve a balance of DC bus voltage, and it involves the DC bus voltage overall control and individual control of each cascade module. At last, the simulation results of 10-kV, 1-MVA CMC-STATCOM verify the correctness and effectiveness of the control strategy and modulation method in this paper using PSCAD/EMTDC.

Power Quality Disturbances Identification Based on dq Conversion, Wavelet Transform and FFT

Based on the waveform characteristic of virtual value by dq conversion, Wavelet Analysis and FFT, seven types of power quality disturbances are layered-recognized. Firstly, according to the size of voltage virtual value, the disturbances will be divided into two types, the first type includes voltage sag, swell and interruption. The second type includes the rest of the disturbances. Secondly, wavelet analysis will be carried out to the second type, transient pulse and low frequency oscillation will be identified by the characteristic of high frequency coefficient and then they will be separated by the number of zero-crossing points. Finally, as far as the disturbances, which present similar distribution in high frequency coefficient, as the comparability, FFT can be used. We can identify them with spectrum characteristic. Simulation results show the effectiveness of the proposed method.

An empirical research on application of electric vehicles

This paper studies the prospects of electric vehicles and the critical factors associated based on the questionnaires in the EVS25 convention. The survey demonstrates that both BEV and HEV have good prospects, where the HEV are more readily to be promoted extensively. Some technical and economic factors, e.g. price and supporting facilities, are major problems of the development of EV. The approval extent of the basic business modes and charging modes of BEV are different. However, the demands of them have been indicated and any business mode or charging mode cannot be neglected. This paper serves as a basic for R&D of EV and can support the constitute of public policies and industry strategies.

Analysis on Parameters Selection of Injection Circuit of Differentiation Cascade type Controllable Custom Power Quality Disturbance-Generator

Theoretical and simulated analysis on the injection circuit parameters of the Controllable Custom Power Quality Disturbance-Generator which is designed as differentiation cascade type has been done. The topology has three modules: fundamental-frequency module, high-frequency module and rectifier module. The theoretical analysis results have shown that the regulation precision of output of the fundamental-frequency module, the voltage level of the high-frequency module, the current tracking performance and the harmonic current circumfluence in the high frequency module will be influenced by the linking inductor of the fundamental-frequency module. The harmonic current output of the high-frequency module will be influenced by the linking inductor of the high-frequency module. Furthermore, taking a capacitor in series with the inductor in the injection circuit of the high-frequency module is an effective method to reduce the voltage level of the high-frequency module. However, this method will influence the amount of the fundamental frequency current that generated by fundamental-frequency module. The simulations have been carried out to show the correctness of the theoretical analysis and provide a reference for parameters selection of the injection circuit and the design of the devices control methods.

The impact of large scale of charge on residential distribution system

For the power grid, the electric vehicle is a new load. The electric vehicles are different from other electrical loads in that they are highly controllable and adjustable. As the rapid development of electric vehicles, the use of residential parking with charging piles for electric vehicles has broad prospects. This paper analyzes the electric vehicle charging mode and the characteristics of charging time, studies the impact of large scale of charge on residential distribution system such as normal power supply, harmonic pollution, peak-valley difference, and put forward some countermeasures in the areas of residential distribution system upgrade, harmonic control, and peak load shifting by use of electric vehicles.

The Study on the Compensation Strategy of Three Single-Phase H-bridge DVR

Three single-phase H-bridge DVR is a kind of dynamic voltage restorer (DVR) which is used very widely. The traditional analysis method of compensation strategy has some shortcomings so that it is not suitable for this kind of DVR. A new analysis method which could overcome the shortcomings of the tradition method is proposed in the paper. The new method not only has definite physical concept but also could determine the compensation range easily when unbalanced voltage sag happened. More importantly, it could be applied to unbalanced load. Adopting the new method, the compensation strategy of three single-phase H-bridge DVR is studied. The simulation result shows the correctness of the theoretical analysis.