Dual bi-directional converter control for wind-solar-hydro system in grid connected and islanded operation

This paper describes a control approach applied to dual bi-directional voltage source converter for composite wind-solar-hydro power system to operate in grid connected and islanded modes. The dq-based control strategy deployed for power converter allows bi-directional power flow, in order to maintain magnitude of load voltage and frequency within permissible tolerances. A control technique is devised based on sum-of-product of load and utility voltages, which would generate requisite phase angle for utility synchronization. The phase angle calculated is utilized for abc- to dq-transformation and viceversa. The control topology is such that any of the energy conversion system (ECS) or in combination can work in utility synchronized or autonomous modes to meet the demand. In such scenario, the controller toggles between current and voltage control modes by changing the set points. The effectiveness of the control technique is demonstrated through simulation of proposed scheme under constant as well as changing meteorological and load conditions.