Research On Key Technology Of Interference Suppression For Wind-storage Hibrid Power System

With social development and population growth, people on the earth confront problems of conventional energy shortage and serious environment pollution. Wind power is one of the most popular technologies generating clean energy, and thus it attracts more and more attentions from industries to academia. The intermittent and randomness of wind velocity affects a stable power output. Therefore, energy storage systems together with wind power gradually constitute wind-storage power systems. Currently, the wind-storage power system has been widely applied, and its related research topics are very popular.The combination of wind power and the storage system helps to large-scale development of new energy, while there are still lots of issues need to be addressed. On one hand, complexity of the power generation system increases uncertainty of the entire wind-storage power system; on the other hand, higher requirements of grid access arise along with the system size continually expanding. Therefore, the recent research focuses on how to make a robust wind-storage power system that can maintain stable operation and high-quality output power under various interferences factors, either inner or outer ones. The present thesis is to eliminate and reduce the adverse impact of interferences, maintain stability of the system, and guarantee the wind-storage power system having high-quality output power and control. The thesis has carried out the following studies:1. Considering the grid access specifications of wind farms and the operation principles of the wind-storage power system, the thesis discusses all kinds of interference from the input, output, and the internal system, and analyzes key issues that affect the stability of the system. That is, if the grid is abnormal, fluctuations of wind velocity can cause power fluctuations and instant voltage drop; as a result, it appears off-grid of the wind-storage power unit and harmonic interference of inverters.2. To eliminate effects of wind fluctuations on the wind-storage power system, the method based on wind velocity prediction is proposed to predict the output power. Considering the characteristics of the control system hardware, the ultra-short-term prediction method on gray theory is proposed to deal with two cases, i.e. limit computation ability and strong computation ability. The proposed method has been validated by comparing simulated results with the actual wind velocity data. In addition, the grid scheduling optimization strategy of power output is also proposed to balance the number of start-stop and the expected power output. The strategycan reduce effects of wind fluctuations on the operation and power generation quality.3. To avoid interference with normal wind power converter and energy storage grid voltage inverter instant fall causing off-grid, the current adaptive control and the sliding mode variable structure control scheme are proposed for low voltage crossing of double-fed inverters in wind turbine. It can reduce the impact on the grid voltage momentary drop system. The experimental results demonstrate the superiority of the proposed method by comparing the simulation results with conventional vector control.4. To reduce the harmonic interference on the system, the thesis analyzes principles of inverter operation and root reasons of harmonic, and proposes a repeat the zero crossing current distortion control and suppression method to suppress harmonics for storage of three-phase and single-phase inverters. The proposed method has been validated by modeling and simulations.5. The above key technologies have all been validated with the corresponding experiments. First, wind power prediction and power allocation experiments have been conducted after selecting the appropriate storage of wind power plants. Experimental results show that the proposed method has a rapid response to the grid schedule and avoids unstable phenomenon caused by frequent start-stop. Secondly, the storage inverter test rig has been built for the harmonic suppression experiment. The experimental results show that harmonic contents meet the relevant requirements of the power grid, and the total number of harmonic contents is better than the required specification. Finally, the low voltage ride through experimental platform has been built for the wind power converter and energy storage inverter. The different voltage drop depth tests have been conducted according to the grid specifications for the low voltage ride through. The experimental results show that the system can have a stable operation during instant grid voltage drop, and can quickly return to normal state after recovery of the power grid voltage, which realizes the low- voltage ride.