Sun Yuanzhang

A novel transient rotor current control scheme of a doubly-fed induction generator equipped with superconducting magnetic energy storage for voltage and frequency support

A novel transient rotor current control scheme is proposed in this paper for a doubly-fed induction generator (DFIG) equipped with a superconducting magnetic energy storage (SMES) device to enhance its transient voltage and frequency support capacity during grid faults. The SMES connected to the DC-link capacitor of the DFIG is controlled to regulate the transient dc-link voltage so that the whole capacity of the grid side converter (GSC) is dedicated to injecting reactive power to the grid for the transient voltage support. However, the rotor-side converter (RSC) has different control tasks for different periods of the grid fault. Firstly, for Period I, the RSC injects the demagnetizing current to ensure the controllability of the rotor voltage. Then, since the dc stator flux degenerates rapidly in Period II, the required demagnetizing current is low in Period II and the RSC uses the spare capacity to additionally generate the reactive (priority) and active current so that the transient voltage capability is corroborated and the DFIG also positively responds to the system frequency dynamic at the earliest time. Finally, a small amount of demagnetizing current is provided after the fault clearance. Most of the RSC capacity is used to inject the active current to further support the frequency recovery of the system. Simulations are carried out on a simple power system with a wind farm. Comparisons with other commonly used control methods are performed to validate the proposed control method.

Discussion on strategy of stabilizing high proportion of renewable energy power fluctuation

The power fluctuation of power system with high proportion of renewable energy and its access have caused a huge challenge to the safe and reliable operation of the power grid. What kind of method should be adopt to stabilize the power fluctuations of renewable energy generation and what to do to ensure the safe and economic operation of power grid have become the focus of research in the world. On the basis of the detailed investigation and study over the power fluctuation of renewable energy based on wind and solar energy, high energy consumption load regulation characteristics, as well as natural gas and oil pipeline network characteristics, this paper puts forward the general idea about stabilizing the high proportion of renewable energy power fluctuation in China. The idea considers the conentrated renewable energy and the distributed renewable energy. First, considerding the concentrated renewable energy. Combined with the characteristics of China’s energy resource development and load distribution, a strategy of transferring high energy consumption load from eastern region to western and northern regions where renewable energy are developed centrally is put forward in this paper. The high energy consumption load such as electrolytic aluminium which was thought had no contribution to the satability of frequency before have developed a new role in this paper. The potential power regulation capability of high energy consumption load is developed to achieve the partly in-situ consumption and the stabilization of fluctuations of the large-scale renewable energy power generation. On the other hand, considering the distributed renewable energy. The method by combining power grid with natural gas pipeline network and oil pipeline network at the receiving-end of power grid of renewable energy distributed utilization is proposed to build the household and commercial hybrid energy system. This system mentioned above can achieve the stabilization of power generation fluctuation at the receiving-end of the power grid. The concept of combing power grid with natural gad pipeline nerwork and oil pipeline network is novel. On this basis, a detailed explanation of the principle of stablizing the concentrated renewable energy power generation fluctuation at the sending-end of the power grid and the principle of stablizing the distributed renewable energy power generation fluctuation at the distribution network side are given in this paper. To improve the effectiveness of this method, the regulation capacity of the two ways to stabilize renewable energy power fluctuation with different development mode of renewable energy in 2020 and 2030 is evaluated in this paper. The result turns out that by transferning the power regulation capability of high energy consumption load to stable the concentrated renewable energy power generation fluctuation at the sending-end of the power grid and combining power grid with natural gas pipeline network and oil pipeline network to stable the distributed renewable energy power generation fluctuation at the distribution network side, the power system with high proportion of renewable energy would be in safe operation.