Autonomous adjustable speed decoupled generation systems and their parallel operation

The paper presents decoupled autonomous adjustable speed generation systems and their parallel operation. The adjustable speed generation unit consists of driving Diesel engine, permanent magnet axial flux generator, power electronic converter and DSP based control unit. The power electronic converter, with intermediate DC link voltage, converts variable frequency and amplitude of the voltage, produced by the permanent magnet generator, to standardized AC three phase four wires 400 V voltage. In each unit the engine speed is adjusted to meet power demand. Proposed method of power sharing does not use any control signal interconnection between generating sets operating parallel. The method of control is based on novel modified flexible droop technique. A steady state and transients are considered. Especially the method provides control of transients of power sharing for connected adjustable speed generating sets operating initially with different speeds. A case of control of nonlinear load current sharing, is developed too. Theory of control and results of laboratory tests of 40 kVA/400 V/50 Hz units are presented to justify the developed modified flexible droop method.