Study of Inertia and Damping Characteristics of Doubly Fed Induction Generators and Improved Additional Frequency Control Strategy

Abstract

Large-scale wind farms connect to the grid and deliver electrical energy to the load center. When a short-circuit fault occurs on the transmission line, there will be an excess of electric power, but the power demand will increase instantaneously once the fault is removed. The conventional additional frequency control strategies of wind farms can effectively reduce the frequency fluctuation caused by load mutation, but still there are some limitations for the frequency fluctuation caused by the whole process of occurrence, development and removal of a short-circuit fault on the transmission line. Therefore, this paper presents an improved additional frequency control strategy for wind farms. According to the variation law of system frequency during the whole process of a short-circuit fault, the proposed strategy revises the parameters in conventional additional frequency control of the doubly-fed induction generator (DFIG) to have effective damping characteristics throughout the entire process from failure to removal, thereby the output power of DFIGs could respond to frequency fluctuation rapidly. MATLAB/ Simulink is used to build a four-machine two-area model for simulation analysis. The results show that the control strategy can effectively reduce the frequency fluctuation of DFIGs, and enhance the stability of the system.

Analysis of Doubly Fed Induction Generators Participating in Continuous Frequency Regulation with Different Wind Speeds Considering Regulation Power Constraints

“…In the example system of this paper, it is reasonable that the reserve coefficient is equal to 0.05. (5) In this paper, the capability and effects of DFIGs participating in long-term continuous frequency regulation are analyzed theoretically. The simulation results are obtained with the initial conditions of the wind speed and equivalent load fluctuation of the designed example.…”

“…At present, there are three control methods for DFIGs participating in primary frequency regulation, including virtual inertia control, rotor speed control and pitch control. References [5][6][7] studied the virtual inertial control of the WT and realize the virtual inertial response of the system. It is verified that the virtual inertial control reduces the frequency fluctuation and improves the system frequency transient stability.…”

Inertia and Droop Frequency Control Strategy of Doubly-Fed Induction Generator Based on Rotor Kinetic Energy and Supercapacitor

“…In order to verify the correctness of inertia and droop frequency control strategy based on rotor kinetic energy and supercapacitor, a four-machine and two-area model [38] was built in a MATLAB/ SIMULINK simulation platform as shown in Figure 10. The power supply of area one was composed of a SG with a governor and excitation regulator, and 300 DFIG with an energy storage device.…”

Power Electronics in Renewable Energy Systems

“…The rest of the converter system is similar to the full-power converter systems used in wind power interfacing. Yan et al [13] study the inertia and damping characteristics of a doubly-fed induction generator (DFIC) during a grid fault. The paper proposes methods to control the frequency in such a manner that the system stability is improved.…”