Study On The Impact Of Load Characteristic And Wind Power Generation On Voltage Stability Of Power System

In recent years, power system at home and abroad is gradually getting closer to large unit, great power grid, long distance and super high pressure. At the same time, due to the growing load demand, power system is getting closer and closer to its limit of operation state, voltage stability problem has become increasingly prominent. In various factors which influence system voltage stability, load characteristic is the most critical, the most active and the most direct one, which directly determines the process of voltage instability and even collapse to a great extend. As a renewable energy, wind power has rapidly developed. But wind speed has the characteristics of volatility and randomness, the problem of wind power system voltage stability has become the bottleneck of interconnecting massive wind farm with power grid. Using bifurcation theory, this paper analyzes the impacts of load characteristics and wind power generation on voltage stability. The main contents are summarized as:1) Based on a typical single machine infinite busbar power system, the influences of different load characterstics on system voltage stability are studied using continuation method and bifurcation theory. Respectively, under static ZIP load, induction motor load, Walve load, the load with recovery characteristics and a special load of wind power, the equilibrium solution manifold curves of power system are tracked and the bifurcation points are searched by calculating the eigenvalues of system state matrix point by point.2) Bifurcation is closely related to the parameters of power system.Under different load models, this paper researchs the impacts of load parameters on equilibrium solution manifold curves and the positions of bifurcation points. Using time simulation, this paper studies the voltage stability of important sections on solution manifold curve and analyzes the impact of time constant of of load models on the change process of voltage, so as to get the parameters which are most conductive to power system voltage stability.3) The effect of wind power interconnecting with power grid on system voltage stability is conducted. Firstly, the active power and reactive power interface equations of third-order asynchronous wind turbine and network are deduced. Secondly, based on typical3node system,when the synchronous generator is replaces by asynchronous wind generator.comparative analyses about PV curve and bifurcation point are performed.Without reactive power compensation, the wind power system based on ordinary induction wind power generator has a small transmission power limit. In other words, the power system containing wind farm is highly dependent on reactive power compensation device. And wind farm should not be run in both cases of reactive power lacking and reactive overloading, in which cases, the active power from wind farm to power system will be significantly reduced.4) Based on3machines6nodes system, voltage stability analysis is performed under doubly-fed wind power generator and third-order induction wind power generator, respectively. Then, under third-order model of ordinary induction wind power generator, SVC is treated as a part of the wind power system. Through single-parameter bifurcation analysis, multi-parameter bifurcation analysis and time-domain simulation, the influences of the time constant, magnification factor, reference voltage of SVC on the equilibrium solution manifold, bifurcation points and voltage instability process of the wind power system are studied, revealing bifurcation mechanism of the various parameters influence wind power system voltage stability.