Liu Zhang

Research and Design for a New Storage Type Converter

In the micro-grid, power storage converter is played as a interface between the battery pack and grid electricity storage device, to achieve a two- way exchange of energy. In this paper, the research and development of power storage converter can realize multiple sets of independent control of the battery, flexible configuration of the system capacity and flexible cutting of the battery pack. Structural design uses multi-level topology. It contains 15 non-isolated half-bridge parallel bi-directional DC / DC converter. Control strategy designed to be grid inverter adopts SVPWM control technology. DC / DC converter designed to improve the droop control strategy based on environmental design. The high-power energy storage converter product this paper designed have completed the charge and discharge related droop control and Full power grid experiment.

Crowbar circuit in wind power grid low voltage ride through

The principle of DFIG wind power generation system is analyzed and the mathematic model is developed. The function of the active Crowbar in LVRT is studied and the parameters of the active Crowbar are given. The simulation result shows that the DFIG system with active crowbar can protect converter against overvoltage and over current. Finally, main power circuit and driving circuit of the active Crowbar is designed. A VSG (Voltage Sag Generation) based on resistor is built. The corresponding experiment is done on the 90kWDFIG experimental platform. The LVRT scheme based on the active Crowbar is studied through experimentation. The experiment result shows that Crowbar is necessary for improving LVRT capability of DFIG wind power generation system and LVRT scheme based on the active Crowbar is effective.

Research on Speed Sensorless Vector Control of Induction Motor

With the 2407 and VC33 double DSP system as the foundation of hardware, the basic idea is using a modified voltage model, implementation, and equivalent amplitude and phase characteristic of integral operation. Motor steady-state operation, the rotor counter electromotive force signal is a sine wave. And an ideal sinusoidal signal frequency for omega after integral link operation, output phase lag, amplitude to times. Observations can be found from the experiment of flux linkage and rotor counter electromotive force signal on the output phase and phase is obtained by pure integral part still have a little deviation, it will need a further study on the compensation link, how to make the compensation phase completely equivalent to the integral effect. From the point of the results of the experiment of 5 Hz low speed estimation error, verify the theory in this paper. One step closer to the test is more slow speed estimation.

Research of State Estimation in Power Network Based on Data Mining Technology

In this paper, a new method that extracting and fixing load characteristic curve in the power system network state estimation is proposed, based on the combination of The data mining technology in the critical meams assorts algorithm and effective index standards. In the course of the study, this paper put forward a new algorithm ,which simulates used matlab software programming and combined with the actual load data, and extracts load characteristic curve for amended. Revised characteristic curve will serve as a typical load model used to add system state estimation of pseudo measure. The simulation results fully support that the proposed method is rational and effective.