Optimal design of multiple controllers based on MIMO identification for large scale power system

The multiple damping controllers must be coordinately designed to avoid the low-frequency oscillation of inter-connected power systems. However,it is difficult to mathematically model a complicated power system. An optimal design approach based on system identification is proposed. A special injection signal,0.1~3 Hz covering all the electro-mechanical oscillation modes,is injected to excite the dynamics of system and the prediction error method is employed to identify the MIMO (Multiple Inputs and Multiple Outputs) order-reduced system model. Additional state and output variables are introduced to improve the traditional linear optimal control technique,which enable the controller to include both lead-lag and proportion blocks. The extended system equations and controller parameter calculation method are given. This approach is verified by the modulation controller design for two HVDC links. The curve fitting degree of MIMO order-reduced model identification is more than 80%.