Yan Xiangwu

Double Closed-loop Control of Three-Phase Five-level PWM Current Source Inverter

A direct type multilevel current source inverter (CSI) and its closed-loop strategy are studied in this paper. In the three phase static symmetric axes (a, b, c), parameters on the AC side of the three phase five-level CSI are time-variant AC variables, which is a difficult point in the designing of control system. So a direct current control method based on the synchronous rotational axes (d, q, 0) is proposed. This strategy transforms AC variables in the three-phase static symmetric axes into direct values in the synchronous rotational axes (d, q, 0), so the problem of controlling the AC variables is transformed into adjusting the direct values. This control strategy has little influence over changes of system parameter, it suit well with linear system and nonlinear system. Simulations are carried out with software PSIM to confirm feasibility of the proposed control method.

Design and Realization of Power Quality Monitoring System Based on DSP and PCI Technique

In order to evaluate power quality more accurately a power quality monitoring system based on DSP and PCI bus technique is proposed. This system combines the powerful operational capability of DSP chip and the abundant resource of the computer together. It can monitor the five targets of power quality real-time and storage the history data with database technique. Test proved that this monitoring system can meet the requirement of the modern power quality monitoring

Design Method of Low Loss and Fast Response LC Filters Based on Locomotive Battery Testing System

Abstract The locomotive battery is sensitive to the fluctuation of its charge/discharge current, so the battery test system is proposed to offer high quality current, such as low ripples (≤ 0.5 %), fast response and wide adjustable extent. Because the battery test system is a non-matched network to the filter, there is a flat decay for the DC current which can’t be avoided. Besides, the locomotive battery has a very tiny inner resistance which is capacitive and with opposing voltage, it makes the filter design more difficult. This paper introduces a method for bidirectional DC/DC filter design. The synthesis method for single-end system is introduced to minimize the flat decay to the DC current. The influence to the characteristic of the filter caused by component dissipation is demonstrated. The dissipation factor of the lossy filter made a left shift to the normalized pole and zero of its transfer-function, this feature is imposed to enhance the response speed of the filter. Simulations and tests proved that the filter possesses low transient peak value, fast converse ability and good filtering result.

Static state stability analysis of AC-excited generators

The most significant difference between the ac-exited generator and the traditional synchronous generator is the adjustable speed. A detail analysis of the static state stability of the ac-excited generator is present. The stability of the ac-excited generator is limit not only by the static state stability limit as synchronous machine but also by the breakdown torque as asynchronous machine. The relation between static state stability limits and rotor speed is derived from the mathematic model, thereby the law of static state stability at any speed is presented and these have been tested by dynamic physical simulative experiment.

LC filter parameter design for the bidirectional converter

New fashioned batteries such as nickel-zinc cell, has characteristics as follows: minimal internal resistance, maximal equivalent capacitance and opposing electromotive force. When testing its performance, the rectifier is required to have special abilities such as fast response, constant and adjustable output current and voltage, could work bidirectional etc. This paper indicated a fast bilateral filter which has low dissipation and fast response speed. The design method and component parameter selections are detailed presented. The merits of the filter are also testified by the MATLAB emulator, which matched the theoretical calculation very well. It has an important application value on bilateral converters

The application of DSP and virtual instrument to online power quality detection

This paper designed a compositive power quality monitor system based on the DSP and PCI bus-mastering technology, which combines the powerful operate capability and the abundant resource of the computer together. This system can measure the five target of the power quality provided with an ability of a databank. So it can detect the power quality more accurately. Test proved that it can meet the requirement of the power quality detection currently

A modified demodulation method for flicker measurement

This article analyses the square demodulation method recommended by IEC on flicker measure and calculate the error brought by this method. On the base of these analyze a new demodulation method is put forward; theoretical derivation and simulation indicate this modified method can reduce measurement error without notable increase of calculation

Analysis of filter circuit of DC side in high-frequency current transformer based on battery performance measurement

Along with the development of battery, the maintenance of battery becomes more and more important, performance measurement and capacity measurement of battery are needed. Moreover, the refreshment of the charge technique should not only feet the charge/discharge requirement of new battery, but also improve the quality of charge/discharge of battery, prolong the operation life span. The text discusses the choice and compare of several filters, on the basis of the demand of circuit in the process of charge or discharge. Finally, the T-filter is chose, the text analyze the dynamic response characteristic, especially when the load is capacitive load, analyze the response function, and the discussion of several physical quantity relatively. In order to eliminate the harmonic component and advance response speed, we design the filter parameter in particular

Experimental study of Micro sources inverter based on virtual synchronous generator

The virtual synchronous generator (VSG) inverter implemented based on real-time workshop (RTW) is proposed. The design cycle of VSG implemented based on RTW is shown. Consulting the traditional mathematical model of synchronous generator in power system, the virtual synchronous generator model is built in MATLAB/Simulink, and realizing the model conversion to the code automatic. Then the Micro-source inverter platform is built. Comparison with the droop control strategy by experiments, it is proved that the control strategy of virtual synchronous generator is superior. The method based on RTW can reduce the time of compilation, integration and debugging, the efficiency is improved greatly on research. Finally, the method of measuring inertia and the formula are given.

Evaluate the Effect of Hydro Turbine Governor Decentralized Control by Transient Energy

The power fluctuation (ΔPe) between generator and electric power system is the main measurable disturbance for destroying generator stability. In order to improve the ability of generator for restraining disturbance, a governor additional decentralized control (HGADC) used on hydro-turbine generator is proposed in the paper based on H∞ robust control theory. When the ΔPe is used as a feedback in HGADC, the couple and nonlinear problem of generator equation will be avoided, and the control equation will be simplified. At the same time, in order to quantitatively evaluate the control effect of HGADC by transient energy (TE), the TE curve is shown in the paper comparing with the curve of rotor speed under different conditions. The results of theoretical analysis and simulating tests show that TE is reduced more quickly by HGADC and HGADC is helpful to improve the stability of synchronous hydro-turbine generator. TE can be used as a quantitative index to evaluate and compare the effect of different stability control laws.