Implementation of absolute rotor angle controller based on PMU in multi-machine systems

A new solution to eliminate inter-area low frequency oscillations through accurate control of absolute rotor angles is put forward recently. The new solution adds extra proportion and integration blocks to the turbine governor. The input of the new governor is the absolute rotor angle measured by a local PMU. The governor ensures that the rotor reaches the same angle position every time PPS arrives by means of PID control. This way, no deviating regulation of frequency and absolute rotor angles can be achieved. Consequently, low frequency oscillations are eliminated. This paper described the problems encountered when implementing rotor angle controller in multi-machine systems and how to solve them. Analysis shows that, when the turbine reaches its capacity limit, the order given by the proportion and the integration block in the governor should be fixed. Otherwise, a new kind of oscillations may be triggered. Besides, when the active power shortage is tremendous, the angle control in all generators should be paused and the traditional primary frequency control should take action instead. The angle control can be restored later, when the generator outputs are increased according to the dispatching center orders and the system frequency deviation is small enough.