Voltage Sensitivity Analysis Based Bus Voltage Regulation in Transmission Systems with UPFC Series Converter

For a unified power flow controller (UPFC) operated in constant power-flow control mode, a novel control scheme of bus voltage regulation is presented. The voltage magnitudes of the ac buses are monitored in real-time operation and are controlled within their limits by the adjustment of the reactive power setting of the series converter. Firstly, the sensitivity of the voltage magnitudes of ac buses to the adjustment the reactive power setting of the series converter is deduced. Secondly, the control scheme of the bus voltage regulation is developed, which adjusts the reactive power setting of the series converter intelligently when the bus voltage limits are violated. Otherwise, the reactive power setting is kept at the value given by the control center. The validity of the proposed control scheme and the voltage sensitivity analysis is proved by the case study in IEEE 39-bus system. The case study also indicates that the proposed control scheme is still valid with a 0.15 second time delay, which further confirms the feasibility of the proposed control scheme in practical engineering.