Application of the Maximum Principle for Optimizing an Active Current Subharmonic Filter

The paper deals with one of the problematic issues of distributed generation facilities operation, namely increased vibration activity of a gas turbine unit (GTU) of an autonomous electric power system (AEPS) with thyristor variable frequency drives (VFD). This kind of phenomenon is considered as subsynchronous resonance (SSR), and the aim of the work is to choose an effective way to suppress it without the possibility of interfering with the design of the power system. It is proposed to use an active power filter (APF) with an automatic control system (ACS) to suppress negative resonance phenomena, which differs from the ACS by active filters, which deal with higher harmonics. The paper presents an approach to the development of control for APF based on the Pontryagin maximum principle. The synthesized ACS will make it possible to correctly determine the optimal control voltage for the APF inverter to suppress subharmonic current and voltage fluctuations in the network.