Study of the bidirectional power flow in Back - to - Back converters by using linear and nonlinear control strategies

This paper studies the performance of the Back-to-Back (BTB) power converter based on Voltage Source Converters (VSC) for the management of the bidirectional transference of active power between two interconnected AC systems (the power supply and the load); as well as the bidirectional reactive power (for either generate and/or absorb) in both terminals of the AC interconnected systems. For power flow management two control laws are explored based on the theory of linear and nonlinear control. The nonlinear control is developed based on the feedback linearization approach. Through the two control laws is possible to obtain a decoupled model of the current components (active and reactive) in the dq synchronous reference frame. The power flow control is achieved by independently controlling the active and reactive components of the current. The control scheme includes two cascade loops (nested), for regulating DC-link voltage, as well as active and reactive power; this control scheme is typically used for VSC control, since it allows increasing the control objectives. The performance of the BTB converter for power flow control is demonstrated through simulation and experimental results using a 3kVA BTB power converter.