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Hu X.-S.,Chongqing University | Sun C.-X.,Chongqing University | Li H.,Chongqing University | Zhao M.,Chongqing University | Tang X.-H.,Wind Power Control Equipment Sub Company of Chongqing Qianwei Instrument and Meter Factory
Chongqing Daxue Xuebao/Journal of Chongqing University | Year: 2010

Based on a on-site wind turbine's output active-power vs. generator speed curve, the shortage of conventional power control strategies of doubly-fed wind turbine generation system are analyzed. Considering the generator speed restriction and active-power fast-track control requirement, the power decoupling control strategy in the rotor-side converter and variable pitch control strategy are improved, that is, an output mechanical torque of wind turbine and the generator speed of DFIG are used in the rotor-side active power control loop in order to achieve an accurate optimal speed control, as well as a direct active-power control method is also adopted in the variable pitch control strategy. Finally, the overall operational performances of DFIG wind turbine generation system using the proposed control strategies are simulated, and also compared with the conventional control strategies. The results show that the improved control strategy is more valid and correct. Source


Zhang Z.-J.,Chongqing University | Li H.,Chongqing University | Chen H.-W.,Chongqing University | Yang C.,Chongqing University | Tang X.-H.,Wind Power Control Equipment Sub Company of Chongqing Qianwei Instrument and Meter Factory
Chongqing Daxue Xuebao/Journal of Chongqing University | Year: 2011

In order to comprehensively and correctly analyze the real-time operational characteristics of a grid-connected wind turbine generator system, it is necessary to analyze the overall control strategies and operation performances of the wind turbine generator system. According to the type of a doubly fed wind turbine generator system, the mathematical models of wind turbine, drive train and doubly fed induction generator (DFIG) are presented. From the viewpoints of the maximum wind energy capture and safe operation of the wind turbine, a maximum power output control strategy is proposed by considering the DFIG loss minimization, and a variable pitch control strategy is also presented by considering generator rotational speed restriction and the output power restriction. Combined with a power decoupling strategy of DFIG, the overall operational performances of the doubly fed wind turbine generator system are simulated. By comparing the simulation, theoretical analysis and actual operational data, the results show that the presented model and overall control strategies of the doubly fed wind turbine generator system are valid. Source


Li H.,Chongqing University | Hu Y.,Chongqing University | Yang C.,Chongqing University | Li X.,Chongqing University | Tang X.,Wind Power Control Equipment Sub Company of Chongqing Qianwei Instrument and Meter Factory
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2011

In order to accurately assess the real-time operating conditions of a grid-connected wind turbine driven generator system (WTGS) while referring to the on-line monitoring information, a matter-element assessing method for the operating conditions is proposed. Firstly, by analyzing the monitored physical quantities of the control system of a WTGS, an evaluation indicator system of operational conditions for a grid-connected WTGS is constructed that can reflect the important operational characteristics of the WTGS. Secondly, by using a method of Bin, the evaluation indicators of the monitoring temperature values are analyzed respectively, and the concept of inferiority indicator is introduced to quantify all evaluation indicators. Thirdly, by using both the analytic hierarchy process (AHP) method and equalization function, the comprehensive weights are calculated. In addition, by referring to the extended relation functions in the matter-element analysis theory, the matter-element assessing model of the operating conditions for the WTGS is developed. Finally, based on the actual monitoring data of a 850 kW WTGS within a period of time, the operating conditions are evaluated with the matter-element method proposed. A comparison with the actual operation conditions shows that the assessment method and model proposed are effective. © 2011 State Grid Electric Power Research Institute Press. Source


Li H.,Chongqing University | Zhao M.,Chongqing University | Zhao B.,Chongqing University | Yang C.,Chongqing University | Tang X.,Wind Power Control Equipment Sub Company of Chongqing Qianwei Instrument and Meter Factory
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2011

From the basic principle of rotating machines stable operation, a rotor speed redundant signal observation method for doubly-fed induction generator (DFIG) is proposed, and the fault tolerant control strategy of the rotor speed sensor is studied by the fault diagnosis. First, by introducing the role of rotor speed signal on the wind turbine driven DFIG control system, a rotor speed observer model of DFIG based on a PLL method is established. Secondly, by the simulation on the operation performance for wind turbine driven DFIG under a step change of wind speed, the output values of the proposed rotor speed observer are compared with the results from the rotor speed sensor output and the closed-loop speed observer from the presented literature respectively. Finally, an adaptive threshold speed signal fault diagnosis method and fault-tolerant control strategy is also proposed, using the examples of the possible soft and hard fault types of the rotor speed sensor, the fault-tolerant control performance of wind turbine driven DFIG is investigated. The compared results show that the proposed speed observer model has a better performance to achieve the redundancy for the rotor speed signal, and the fault-tolerant control of the rotor speed sensor can also be exactly performed when the sensor has a fault. © 2010 State Electric Power Research Institute Press. Source


Li H.,Chongqing University | Chen H.-W.,Chongqing University | Yang C.,Chongqing University | Zhao B.,Chongqing University | Tang X.-H.,Wind Power Control Equipment Sub Company of Chongqing Qianwei Instrument and Meter Factory
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2011

In order to analyze accurately the factors and rules of influencing the power oscillation of a grid-connected wind turbine generator system, the frequency analysis for active power oscillation of a wind turbine with squirrel-cage induction generator(SCIG) system is proposed according to different operational conditions and different wind turbine models and parameters. Firstly, by using the equivalent lump mass method, and combining the electro-magnetic transient models of SCIG, the mathematical models of the wind turbine with a SCIG are presented with different wind turbine drive-train equivalent models. Secondly, according to a wind speed disturbance, simulations on the frequency for active power oscillation of the WTGS are investigated under the conditions of different drive-train models, rigid coefficients, and different wind speed disturbed frequencies. Finally, according to a 3-phase short-circuit fault of the connected grid, by using a two-mass equivalent drive-train model, simulations on the frequency for active power oscillation of the WTGS are also investigated under the conditions of different drive-train rigid coefficients and different fault durations. The compared results have shown that the active power oscillation amplitude at the same oscillation frequency is related closely with the drive train models, drive-train rigid coefficient and the fault duration. Source

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