Transient Stability Improvement for Combined Heat and Power System Using Load Shedding

The purpose of the paper is to analyze and improve the transient stability of an industrial combined heat and power (CHP) system in a high-tech science park in Taiwan. The CHP system installed two 161 kV/161kV high-impendence transformers to connect with Taipower System (TPS) for both decreasing the short-circuit fault current and increasing the fault critical clearing time. The transient stabilities of three types of operation modes in CHP units, 3G1S, 2G1S, and 1G1S, are analyzed. Under the 3G1S operation mode, the system frequency is immediately restored to 60Hz after tie line tripping with the TPS. Under the 1G1S and 2G1S operation modes, the system frequencies will continuously decrease and eventually become unstable. A novel transient stability improvement approach using load shedding technique based on the change in frequency is proposed to improve the transient stability.