Jialong Wu

The protection link within the wind farm is the key link that affects the transient characteristics of the wind farm, and also has the greatest impact on the complexity of scene construction. Therefore, it is urgent to study the method that can quickly build the chopper circuit and crowbar circuit action scene during the evaluation of the equivalent model of the wind farm. In this paper, a fast generation method of wind farm protection state scenarios based on Deep Belief Network (DBN) is proposed. Firstly, characteristic quantities that affect the protection action of a single fan in a wind farm are extracted, such as terminal voltage drop (the junction voltage of a single fan is equal to the terminal voltage), wind speed, etc. Simulation is carried out on a single fan in scenarios with different characteristic quantities, and records of characteristic quantities and protection actions are put into the DBN model for training as a sample set. Through training, a DBN model which can directly and accurately generate the fan protection state according to the characteristic quantity is obtained. Then, the topological structure and line impedance information of the wind farm are obtained, and the relationship between the voltage drop at the junction point and the voltage drop at the end of each fan in the wind farm is obtained. Combined with the voltage drop at the end of each fan in the wind farm and the deep belief network model, the fan protection action scene in the wind farm can be quickly generated for equivalent model evaluation. Finally, a numerical example is given to verify the effectiveness of the proposed method.

An accurate wind farm model is a crucial prerequisite to ensure that the simulation results of the power system containing wind power align with reality. Hence, it is imperative to establish a system for evaluating the accuracy of wind farm models. This paper examines the fault response characteristics of wind turbines and proposes a multi-dimensional quantitative index system for assessing the equivalency of wind farm models. The entire process can be segmented into two stages: the transient period immediately following the fault occurrence and the subsequent steady-state phase. The evaluation indexes for assessing the accuracy of wind farm models are voltage dynamic response, active power dynamic response, and reactive power dynamic response. These indexes are formulated to evaluate the equivalency of wind farm models across various stages.

Large-scale grid-connection of wind power has a profound impact on the characteristics of power grids. To study the mechanism of the influence of voltage sudden changes on the transient response characteristics of double-fed wind fields is the basis of ensuring the safe and stable operation of power grids. In this paper, the expression of rotor current under symmetrical voltage sudden changes is derived, and the related factors affecting the transient response characteristics of rotor current are analyzed. Then, a detailed DFIG model is built in PSCAD, and a variety of scenarios are simulated to verify the accuracy of the proposed doubly-fed fan’s transient response characteristics under symmetrical voltage sudden changes.

Load aggregators can aggregate user loads, achieve demand response, and relieve the pressure on the power grid. In view of the lack of scientificity in the selection of users in demand response work, the lack of full consideration of constraints such as power loss and user satisfaction, and the failure to optimize the interests of multiple participants, as well as the low response capacity, this paper establishes a game model of load aggregators based on two-level optimization, taking into account subsidy incentives. Among them, the upper layer model is a game model between load aggregators, and the lower layer is a clearing model based on system operators, which is solved using a diagonalization algorithm. On the basis of the above model, the potential of users participating in demand response is assessed, so that load aggregators can screen out high-quality users. Finally, the effectiveness and feasibility of the model and its solution method were verified through numerical simulation calculations.

The stability control system is a facility critical for the power grid operating safely and stably in the event of severe faults. The failure of its devices or communication channels can impact on the operation of the power grid seriously. Based on analysis of the business functions and control architecture of the stability control system, a stable control system modeling and risk quantification evaluation method based on control strategies has been proposed. Firstly, a logical correlation model for the stability control system and communication network is constructed. Then, a quantitative evaluation method of stability control system risk based on strategic control quantity is proposed. Finally, based on a typical power grid scenario, the rationality and usability of the method were analyzed and verified.

Large-scale grid-connected power supply based on inverters brings severe challenges to the stability and security control of power system. Due to the simulation resources and calculation efficiency, it's necessary to equivalent the multi-inverter power supply in the new energy field when conducting the system stability and security simulation analysis. In this paper, for the scenario where multiple inverters of the same type are connected to weak grid, the open-loop transfer function and output impedance of the inverter grid-connected current are derived based on frequency analysis, and the stability judgment based on the impedance model in weak grid is obtained. Furthermore, the transfer functions of the inverter single equivalent and multiplication equivalent solutions are derived. The stability differences and key influencing factors are analyzed between the two equivalent solutions and the actual parallel multi-inverter system. Finally, the results of the theoretical analysis are verified by simulation based on an example. Through theoretical and simulation studies, the differences in the principles, effects of different equivalent schemes and the applicable conditions are clarified, and guidance is provided for reasonable selection of inverter equivalent solutions and simulation analysis.