Hyeong-Jin Choi

Enhanced Dynamic Response of SRF-PLL System for High Dynamic Performance during Voltage Disturbance

Usually, a LPF (low pass filter) is used in the feedback loop of a SRF (synchronous reference frame) - PLL (phase locked loop) system because the measured grid voltage contains harmonic distortions and sensor noises. In this paper, it is shown that the cut-off frequency of the LPF should be designed to suppress the harmonic ripples contained in the measured voltage. Also, a new design method for the loop gain of the PI-type controller in the SRF-PLL is proposed with consideration of the dynamics of the LPF. As a result, a better transient response can be obtained with the proposed design method. The LPF frequency and the PI controller gain are designed in coordination according to the steady state and dynamic performance requirements. Furthermore, in the proposed method, the controller gain and the LPF cut-off frequency are changed from their normal value to a transient value when a voltage disturbance is detected. This paper shows the feasibility and usefulness of the proposed methods through the computer simulations and experimental results.

Simulation Modeling and Experimental Validation of Generator Control Strategy in DFIG System

To investigate the dynamic response of WECS to the events in power system, an accurate simulation m odel for DFIG(doubly-fed induction generator) system is d eveloped using PSCAD/EMTDC and a hardware-in-loop si mulator is implemented using 3kW M-G set. The model c onsists of wind model, rotor dynamics, wound rotor induc tion generator, power electronics converter and control str ategies. Control strategies can be programmed at torque-s peed plane as needed and implemented in DSP controlled power converters. Simulation and experimental results sh ows smooth change of control modes and efficient power control performances.

Design of SRD-F-PLL system with consideration of low-pass filter for high dynamic performance during voltage disturbance

Usually, LPF(low pass filter) is used in the feedback loop of SRF(Synchronous Reference Frame) - PLL (Phase Locked Loop) system because the measured grid voltage contains harmonic distortions and sensor noises. In this paper, it is shown that the cut-off frequency of the LPF should be designed to suppress the harmonic ripples contained in the measured voltage. Also, a new design method of the loop gain of the PI-type controller in the SRF-PLL is proposed with the consideration of the dynamics of the LPF. As a result, a better transient response can be obtained with the proposed design method. The LPF frequency and PI controller gain are designed in coordination according to the steady state and dynamic performance requirement. This paper shows the feasibility and the usefulness of the proposed methods through the computer simulation and the lab-scale experiments

Implementation of active and reactive power control strategy in a lab-scale DFIG simulator

To investigate the dynamic response of WECS to the events in power system, an accurate simulation model for DFIG(doubly-fed induction generator) system is developed using PSIM and a hardware-in-loop simulator is implemented using 3kW M-G set. The model consists of wind model, rotor dynamics, wound rotor induction generator, power electronics converter and control strategies. Control strategies can be programmed at torque-speed plane as needed and implemented in DSP controlled power converters. Simulation and experimental results shows control of Reactive Power and efficient power control performances.