计及系统强度约束的设备异构新能源场站集群协同紧急控制策略OA

With the acceleration of global energy transition,the penetration rate of new energy is gradually increasing,which weakens the voltage support strength of the system(referred to as"system strength")and easily induces stability problems such as static voltage instability and sub/super synchronous oscillation.In order to overcome the above challenges,this paper focuses on new energy bases containing multiple heterogeneous renewable energy plants.In response to small-probability events such as large deviations in renewable energy plants prediction and line shutdowns that may trigger a sudden drop in system strength,a collaborative emergency control strategy for multiple renewable energy plants considering system strength constraints is proposed to maintain the safe and stable operation of the new energy base after experiencing a sudden drop in system strength. Firstly,for new energy bases containing multiple heterogeneous renewable energy plants,an evaluation architecture is established based on the generalized short circuit ratio(gSCR)system strength index to facilitate real-time monitoring of system stability margin.Based on this,the emergency control objective is characterized as the problem of maximizing the output power of renewable energy plants that satisfies the system strength constraints,in order to maintain stable system operation while avoiding cascading failures,e.g.,frequency drop which may be induced by active power shortages as much as possible.In order to quickly achieve the above control objectives,real-time feedback of system stability margin is utilized to construct a collaborative emergency control strategy for multiple heterogeneous renewable energy plants in the new energy base based on the primal dual gradient algorithm.On the premise of ensuring sufficient system strength and small disturbance stability margin,the overall output of each renewable energy plants is maximized while maintaining sufficient system strength.After the system strength gradually recovers,the power output of each renewable energy plant will adaptively increase until it reaches the upper limit. The effectiveness of the proposed strategy is verified through simulation.Compared with traditional complex trial-and-error method,the relative error of the proposed fast calculation method for critical generalized short-circuit ratio is mostly within 3%,with a maximum of 5%,and is not less than trial-and-error value,which demonstrates that the fast calculation method possesses both accuracy and robustness.Under the fault condition,the system without emergency control will become unstable within 0.5 seconds.With the proposed emergency control scheme,the oscillation will stabilize within 3 seconds.In the IEEE 39-bus system with a stability margin set at 0.2,the new energy deloading ratio is 28.01%,which is lower than that of existing methods. The following conclusions can be drawn from this paper:(1)By analyzing the small disturbance stability of new energy systems,a critical generalized short-circuit ratio calculation method considering heterogeneous characteristics of multiple renewable energy plants is proposed to quantify the small disturbance stability margin.(2)Based on the aforementioned method,the small disturbance stability margin of the distributed real-time monitoring system can be monitored in the real time,providing a reference for the stability evaluation of the operation of new energy bases.(3)The proposed online distributed emergency control strategy for heterogeneous new energy bases enables each renewable power station to actively respond to random fluctuations in system operating conditions and adaptively meet the requirements of the proposed power allocation rules.When the system strength drops,the new energy deloading ratio is optimized,which can avoid sub/super synchronous oscillations caused by weak grid condition and large-scale renewable energy outage. For new energy bases that include grid-following and grid-forming devices,how to leverage the synergistic effect between grid-following and grid-forming devices to further enhance the effectiveness of emergency control will be an important research direction in the future.