Researches Of Device-level Control Strategy For The Distributed Power Flow Controller

Distributed Power Flow Controller(DPFC) is derived from the Unified Power Flow Controller(UPFC), the DC bus between the shunt and series devices is eliminated. Distributed Power Flow Controller has the same control ability as UPFC whereas the modular structure increase the flexibility of overall control method. The main research contents of this thesis focus on the device-level control strategy for the distributed power flow controller, including following details:Firstly, the topology of the distributed power flow controller DPFC is presented and its working principle analyzed including the calculation of its power flow control ability. Phase lock loop for 50 Hz signal is designed based on second-order generalized integral method and the cascaded delayed signal cancellation method utilized for the third harmonic 150 Hz current extraction and calculation.Next, the device level controller for the shunt side of the DPFC is designed. The relationship between the current and the modulation voltage of the converter is analyzed by current mathematical model, and the feed-forward decoupling control method is utilized for direct power control. The effect of the power hysteresis direct power control is not satisfactory. Voltage oriented direct power controller is designed using the feed forward decoupling method to solve the cross coupling problems in the power mathematical model. The simulation model of the shunt side dual converters can be used as the basis for the experimental platform. For the series side converter control, second-order generalized integral utilized to construct orthogonal coordinate system in both fundamental and third harmonic circuit. Vector control is designed for both 50 Hz and 150 Hz voltage. Based on the instantaneous power calculation for base and third harmonic system, the power prediction controller is established.Simulation model of distributed power flow controller test system is set up on the basis of both shunt and series converters, through its ability to control power flow, the functions of the device-level controllers is verified.Finally, 800 VA experimental prototype of the DPFC shunt side dual converters is developed, software and hardware designed and debugged. Experimental results show the shunt side can achieve unit power factor rectify and send active power via the third harmonic current.