The Application Of Energy Storage System In Wind Farm

Energy and environment are the material foundation of the human survival and social development, and related to the national economy and security. With the increasing tension of traditional fossil fuel resources, and the greenhouse effect caused by a large number of CO2emissions, the requirement of renewable energy is more and more intense. By2020, China’s clean energy capacity will reach570million kilowatts, accounting for35%of installed capacity. However, due to its stochastic variability of distributed generation, it will bring many adverse effects while accessed to the traditional power grid. With energy storage technology, the smart grid could give an effective solution of the problem, and reduce the variety of disturbances caused by distributed power generation. So the energy storage plays an important role in the Large-scale applications of renewable energy.On the one hand, this paper presents an integrated power generation and energy storage system (ESS) for doubly-fed induction generators in wind farm. An ESS is connected to the point of common coupling through a bi-directional power converter. The ESS is controlled so as to smooth out the total output power as the wind speed varies. The decoupling control of active and reactive power can be achieved by controlling the d-axis and q-axis components of the controller currents. And the control algorithms are developed by this principle for the ESS converter and are tested on a simulation model developed in MATLAB/Simulink. Simulation studies are carried out on a9MW wind farm and the result suggest that the integrated power generation and ESS can supply steady output power as the wind speed changes. In addition, when the grid voltage sags, ESS could release reactive power to compensate the voltage sag. Consequently, wind power system could remain the grid-connected operation and the LVRT capability is improved effectively by the ESS. The result shows that ESS plays an important role in output power smoothing and fault ride through enhancement.On the other hand, a comparative analysis of cost to determine the most suitable storage technology for mitigating wind power problems related to power quality introduced by wind power short-term fluctuation is presented. Then, a method is proposed for scheduling and operating a virtual power plant in an electricity market environment. The proposed method is able to take advantage of existing market opportunities for increasing operational profits while smoothing out energy imbalances caused by the errors associated to wind power forecasts.