Chi Yongning

Research on offshore wind farm VSC-HVDC transmission system fault ride through issue

With the development of power electronics technology, VSC-HVDC has been applied in some offshore wind farm integration projects in Europe by IGBTs and PWM control technology. At the same time, a lot of works have been done on wind farm AC integration fault ride through, and certain results have been achieved, but offshore wind farm DC integration fault ride through issue needs to be studied deeply. The paper focus on offshore wind farm VSC-HVDC transmission system fault ride through. Based on AC and DC wind energy integration stability influence analysis, compared the different integration mode technology characteristics, the main stability influence factors of DC integration will be given. Then the offshore wind farm VSC-HVDC transmission system fault ride through scheme is studied according to the wind farm capacity. Chopper and wind turbine coordinated control scheme will be adopted to provide dynamic reactive support on the basis of the system meeting the requirements of the fault ride through. Finally, a practical example is done to verify the correctness and effectiveness of the proposed scheme.

On the Road to Wind Power: China's Experience at Managing Disturbances with High Penetrations of Wind Generation

Today, electric power generated from renewable energy sources accounts for a large share of the Chinese power system. By the end of 2015, the total wind power installed capacity had reached 129 GW , ranking wind as the second largest power source following thermal power in some regions of China.

Study on LVRT capability of D-PMSG based wind turbine

Wind power in China is experiencing rapid development in recent years, and problems come forth due to the grid connection of large-scale wind power. Based on the status of wind power development in China, necessity of wind farm low voltage ride through (LVRT) capability is studied in this paper. The strategy for LVRT realization of D-PMSG based wind turbine is presented by studying the control system of wind turbine, and the control processes during LVRT period is showed. A study case is given to show the impact on power grid when wind farm is with or without LVRT capability and also to show the validity of LVRT models and control system presented in the paper.

Research on market mechanism of wind power accommodation based on power bidding

With development of smart grid and enhancement of wind power integration technology, competition mechanism, gradually introduced into the power market in China, will provide convincing external environment for the wind power accommodation. Wind power accommodation mechanism based on power bidding is presented, as well as accommodation analysis model and calculation method are put forward in this paper. Firstly, feed-in tariff of wind power is declared by wind farms according to operating cost and economic performance, then wind farms are arranged according to costs from low to high order, then dispatching schedule and commitment of wind farms are formulated based on the principle of minimum purchase cost. Finally, wind power accommodation space is calculated by using continuous time series production simulation method. Consequently, the impartial and open power dispatching principle is held to realize priority dispatching under the situation of a provincial power market and system peak regulation capabilities. In the environment of power market, reasonable and effective power bidding will be significant for wind power benefit and will provide referenced frames for practical operation of power bidding.

Fault ride through characteristics of connection of large wind power island to VSC-HVDC grid

With increasing scale of wind power development, large wind power bases will, where there is no support from synchronous power source, be directly connected to the grid and therefore one of developing trends to transmit currently large-scale wind power is transmit the wind power “island” with the long distance VSC-HVDC transmission technology when it is connected to the grids. When a large-scale wind power island is connected to a VSC-HVDC grid, the wind turbines and the VSC-HVDC grid will influence each others operation and control, and in particular, in the case of fault, mutual coupling of dynamic characteristics of electrical variables at different time scales between the wind turbines and the VSC-HVDC grid cannot be ignored. The paper is focused on non-synchronous detection of disturbance, one of key problems found in connection of wind power to the VSC-HVDC grid, and studies the fault ride-through (FRT) technology for the island-connected large-scale wind power and the VSC-HVDC grid, by analyzing the impact of fault-response characteristics of the wind power and the VSC-HVDC grid at different time scales on each other.

Deployment and control strategy of reactive power devices in large wind power collection stations

Due to the features of wind sources location and power grid structure, the development mode of wind power in China presents characteristics of building large wind power bases and connecting into bulk power grid at present and for a period of time in the future. Several 10GW-level wind power bases will be built in Hebei, Jiangsu, Inner Mongolia, Gansu, Xinjiang, Jilin according to the development plan made by National Development and Reform Commission, and some of these bases will be connected to power grid via 500kV or even 750kV lines. Consequently, the interaction between wind power and power system become greater. Since wind power has the characteristics of randomness, variability, intermittence, unpredictability and uncontrollability, the integration of wind power will inevitably bring some impact on the plan and operation of power system. The deployment of reactive power devices in wind power collection substation will help to improve the voltage stability of local power grid, to avoid the large-scale trip-off of wind turbines and to improve the capability of substation to exporting wind power. As to the development mode of wind power in China, this paper conducts a study on reactive power compensation of 500kV wind power collection substation in large wind power base. Principle that determines the capacity and type of reactive power devices will be developed considering the active power change and reactive power characteristics of wind power base. The type of dynamic compensation devices will be analyzed based on transient stability analysis. Finally, the technical requirements and control strategy of reactive power compensation devices in wind power collecting substation will be given.