Study On The Transient Stability And Control Strategy For Wind-thermal-bundled Transmission System

Under the situation of traditional fossil energy’s reducing and the increasingly serious environmental pollution, renewable clean energy development and utilization get national attention. China has lots of wind power, The development of wind power generation technology can reduce the pollution of the environment. With the development of the wind power generation, the capacity greatly improved, the proportion of wind power in the power supply is growing. But the uncertainty of wind power brings a lot of risks to the security and stability of power grid. In this thesis, the Wind-Thermal-bundled of AC/DC delivery system to study the impact of wind power thermal power between each other on the transient stability of the grid, on the end-system failure evacuation should take emergency control strategy research.Firstly, the Wind-Thermal-bundled typical system, the models that can adequately reflect the basic characteristic of wind-thermal-bundled power system is built based on the MATLAB. Including the mathematical models of doubly-fed induction generator, thermal power and the DC systems.Secondly, by using EEAC theory and energy imbalance theory, the transient stability is researched in systems that are integrated with different capacity of wind power under certain boundary conditions. The best transient preventive control is suggested for Wind-Thermal-bundled system by simulation which can improve transient stability margin. It shows that the greater the system’s transient stability margin has the better transient stability of the system. For a typical simulation of the Wind-Thermal-bundled system, shows that increase the proportion of wind power in Wind-Thermal-bundled system can get the better system stability when disturbed cluster inertia unit is less than the remaining fleet inertia unit at the fault system. This provides a reference for the system transient stability preventive. According to the simulation results, it is revealed that there are two decisive aspects that dominate Wind-Thermal-bundled power system’s instability when its critical transmission line is in fault. One aspect is that large amount of accelerating energy is generated in system fault and the other is that the disturbed system is in a low level of voltage.Finally, different thermal units tripping and wind power generator tripping methods are compared by simulation and the rules are concluded that units tripping obeys when it has an effect on transient stability. Based on the rule, a new thermal-wind power-combined units tripping method is proposed. The superiority of new unit tripping method is demonstrated by simulation;Then analysis of the wind farm configuration FACTS dynamic reactive power compensation devices, respectively for SVC and STATCOM two kinds of compensation devices were analyzed, concluded that STATOCM is the better choice to provide more reactive power support when the economy is allowed;And method for suppressing wind power fluctuation by power modulation mode of HVDC system, achieved HVDC power dynamic followed wind power fluctuations relieved the pressure of generator at short-term frequency modulation pressure, to improve transient stability of the system.