3. Switching Control of Synchronous Generators for Transient Stability Enhancement

This chapter firstly proposes a coordinated SPSS to enhance the stability of multi-machine power systems. The SPSS switches between a BPSS and a CPSS according to a state-dependent switching strategy. The BPSS is designed as a BCFC, and it is able to provide fast damping of rotor speed oscillations in a bang-bang manner. The closed-loop stability of the power system controlled by the SPSSs and the CPSSs is analyzed. To test the performance of the SPSS, simulation studies were undertaken in a four-generator eleven-bus power system and the IEEE 16-generator 68-bus power system. SPSS is evaluated in aspects of small-signal oscillation control and transient stability enhancement, respectively. Meanwhile, the coordination between different SPSSs and that between SPSS and CPSS are studied therein. Synchronous generators are the main power sources in power systems, and their resilience significantly impact the reliability and resilience of the entire power system. Hence, it is disable to explore the largest control energy of synchronous generators during severe grid faults, in order to damp the oscillations and achieve energy re-balance in the system. Hence, this chapter also proposes two switching controllers working in a coordinated manner to enhance the transient stability of multi-machine power systems. The first one is SEC and the other is SG. The SEC switches between a BEC and a CEC and the SG switches between a BG and a CG, via a state-dependent switching strategy. The BEC and the BG are designed as BCFCs, which are able to provide fast switching of excitation voltage and valve position between their upper and lower limits. The boiler pressure effect is concerned in the detailed steam turbine model in the controller design. Simulation studies were undertaken in the IEEE 16-generator 68-bus power system to evaluate the performance of the switching controllers. Coordination between the excitation loop and speed governing loop was studied. Two system resilience indexes were introduced, and the short-term resilience is investigated for the power systems with and without switching controllers installed, respectively.