Coordination And Optimization Of Additional Damping Controller In Multi-HVDC Control Systems

As the development of the power system in our country, long-range transport oflarge-scale wind powerand the implementation of west-east electricity transmission project;mutual power supply between north and south; the national network connected strategy,interconnection between regional power grid in China has entered the stage of planning andimplementation. Characteristics of regional power grid interconnection, long distance, largecapacity transmission, parallel operation of multi-AC-loop and multi-DC-loop are graduallypresented in power system. However, with the development of AC/DC hybrid power grid,power grid dynamic stability problem is increasingly complex. Interval weak dampingproblem becomes one of the major challenges facing large-scale ac/dc hybrid powergrid.Multi-loop high-capacity high-voltage DC transmission HVDC system has theadvantages of rapid response, strongly controllable, large adjust capacity and wide acrossregion, which provides powerful means to improve the dynamic performance of the system.Additional damping control of DC as an effective way of DC modulation control has beenwidely studied.Around the multi-loop DC control system with additional dampingcontroller, this article carried out a series of research on controller feedback signal selectionand coordination optimization of controller parameters.Firstly, this article carried on the small signal stability analysis to Southern Power Grid.On this basis, a dominant mode ratio indicator was proposed based on Prony analysis toreflect the observability of the feedback signal of specified oscillation mode. By doing this,the wide area feedback signal could be filtered. In view of large grid, DC additionaldamping controller parameters optimization presents the problem of dimension disaster. Anoptimization algorithm based on subspace identification and genetic algorithm is proposed.Firstly the open-loop state-space equation of Southern Power Grid was obtained by thesubspace identification. Then the close-loop state-space equation with additional dampingcontroller was derived. Finally, with maximization the minimum damping ratio as theoptimization goal, genetic algorithm was used to coordinately optimize the additionaldamping controller parameter in matrix A in closed loop state. Then the optimal additionaldamping controller parameters were obtained. A series of simulation and analysis proceed under the environment of DC system fault, AC system fault and the operation mode change.Simulation results show that the optimization of additional damping controller inmulti-loop DC control system can obviously improve the damping level in Southern PowerGrid. Thus the stable operation of the system is guaranteed.