Reliability Assessment Of Power System With Wind Farm

With the increasing demand of energy and the development and utilization of renewable energy, wind power, as a renewable clean energy, is attracting more and more attention. Due to the rapid development of wind generation technique and sharply drop of wind power cost, wind power has become an important alternative to traditional power generation sources. As the random and intermittent inherent characteristic of wind energy, wind power has an important effect on the security and stability of power system, especially on the reliability of power system. The characteristic of wind power system is analyzed and the impact of wind farm reactive power compensation on power flow distribution is studied in this paper. Wind power reliability model is established based on the randomness of wind power and the uncertainty of power system operation state. Based on sequential Monte Carlo simulation and steady-state power flow, the reliability impact of wind power is evaluated respectively.The main content and research conclusion of this paper are as follows:(1) The foundation knowledge of wind farms connected into power system is introduced, such as the basic components of wind turbine, the energy conversion process and the basic requirements and grid-connected manner of wind farm. The impact on voltage fluctuates and flash, harmonics pollution and the corresponding improvement measures are presented in this paper.(2) Sequential Monte Carlo simulation algorithm is utilized to calculate the reliability of power system containing wind farm. The Weibull probability distribution model is used to generate wind speed. The output of wind turbines is achieved by using the mathematical relationship between wind speed and active power output. The reliability model of wind turbines is established based on the random characteristic and forced outage rate of wind turbine. The reliability of system EPRI-36 containing wind farm is evaluated using sequential Monte Carlo method. The effect of wind turbine number variation on the power system reliability and the influence factor of wind farm are calculated respectively. The result showed that wind farm has advantageous influence on power system reliability level though the fluctuation and uncertainty of wind speed would bring down power supply reliability of wind farm. In terms of economy and reliability, a number of wind turbines injected into power system will improve the reliability of power system.(3) Wind turbine need to absorb reactive power from power system to establish magnet field while transporting active power to system. According to this characteristic, the steady-state model and reactive power compensation model of wind turbine are established. The effect on power system voltage is calculated in the following two conditions: wind farm connected with power system at different node and the reactive power compensation capacity varying. The results showed that the system voltage level rise with the increase of reactive power compensation capacity, the nearby node voltage rise markedly and the voltage of nodes far away from wind farm rise slowly.(4) Sequential Monte Carlo simulation has limitations in power system reliability assessment because transmission line overload and voltage collapse are not taken into account in the process of reliability assessment. Based on power system steady-state analysis, the reliability is evaluated in the following two conditions: wind farm connected with power system at different node and the reactive power compensation capacity varying. The results showed that the reliability level of power system containing wind farm rise with the increase of reactive power compensation capacity; the location of wind farms has a great influence on power system reliability. Site selection of wind farm is an important work in planning project.