Research On Coordinated Control Of Generator And Grid For Transient Stability In Power System Centrally Integrated With Large-scale Wind Power

It is good for resource optimization and wind energy utilization that large-scale of wind power is integrated. However, it brings new challenges to the security and stability of power system due to different characteristics between wind turbine generator and conventional synchronous generator. Therefore, it is very necessary to research protection and control method for power system integrated with large-scale of wind power.Gansu wind-thermal-bundled power system (shorted for WTBPS) is chosen as the research object as it is centrally integrated with large-scale wind power. On the basis of WTBPS, transient stability and coordinated control of generator and grid are studied. Firstly, transient preventive control for WTBPS is analyzed by comparing transient stability of systems with different capacity of wind power. Secondly, the reason of transient instability in WTBPS is explained when the critical transmission line is in fault, and two transient emergency control approaches, namely tripping thermal units and wind power units, are compared. Based on the concluded rules that unit tripping obeys when effecting on WTBPS power system, a new unit tripping method is proposed. At last, coordinated thermal units tripping methods are suggested with reactive power control mode of DFIG and its LVRT ability.Firstly, by using EEAC theory, 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 WTBPS by simulation which can improve transient stability margin.Secondly, by analyzing simulation results, it is revealed that there are two decisive aspects that dominate WTBPS 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. 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. Under the premise that system has an enough stability to support its voltage, the thermal units with largest unbalanced energy should preferentially be tripped, based on which wind power generators are tripped gradually. The superiority of new unit tripping method is demonstrated by simulation.At last, based on the scenario that WTBPS’s critical transmission line is in sever fault, the law of wind power generator’s reactive power control mode and its LVRT ability effecting on thermal units tripping in power system is researched. Based on the law, the thermal units tripping method is proposed coordinated with wind power generator’s reactive power control mode and its LVRT ability.