Effects of supply voltage non-idealities on the behavior of an active power conditioner for cogeneration systems

The use of a power conditioning system (PCS) connecting a cogeneration plant to the electrical network, makes it possible to employ high-speed turbines directly coupled to permanent magnet synchronous generators. This solution leads to a very compact arrangement, characterized by high reliability and efficiency. Furthermore, the PCS is able to deliver not only the rated active power to the mains, but reactive power and current harmonics as well. In this way, the PCS can operate as active filter when nonlinear loads are connected to the same network. Nevertheless, undesired behavior may occur when the supply voltages are nonideal, such as in presence of unbalance, harmonics, flicker, or when the line impedance is not negligible. This paper presents a new control strategy that allows good performance to be achieved under ideal and nonideal supply voltages. The stability and the dynamic behavior of the overall system has been analyzed by introducing suitable transfer functions. The analytical developments have been confirmed by performing numerical simulations an a realistic circuit model implemented with PSpice.