Excitation Limiters Design for a Micro-Alternator Buck Converter Based Static Excitation System

This paper presents the design of excitation limiters such as an under-excitation limiter, over-excitation limiter and V/Hz limiter as per IEEE std 421.5 and implemented on a DC-DC buck converter-based static excitation system to protect the generator during abnormal conditions such as overloading, overheating and over-fluxing of the machine. A digital time constant regulator (TCR) is incorporated to modify the field’s time constant of micro-alternator, to mimic the dynamics of large synchronous machines. The detailed tuning procedure of limiters and TCR is discussed to comply with IEEE STD 421.2 and IEEE STD 421.5. The performance of the developed excitation system with limiters is tested under various small and large disturbances.