Improved dynamic power flow model with DFIGs participating in frequency regulation

Abstract

Summary The primary frequency regulation of the DFIGs is newly introduced to dynamic power flow to analyze the post‐disturbance power flow and system frequency. Based on the overspeed/pitch angle control, the equivalent inertia of the DFIGs is quantified by their inherent inertia and the adjustable range of the rotor speed, which together with the inertia of the SGs determines the system frequency. With simultaneous solution to the constraints of the DFIGs and power system, the captured power by the wind turbine, the rotor speed, and the slip of the DFIGs are adjusted in dynamic power flow, thus to quantify power loss and active output of the DFIGs, and avoid optimistic judgment to the frequency regulation capability of the DFIGs. With increasing wind power, the wind turbine generators are expected to participate in the frequency regulation to save the burden of synchronous generators (SGs). The primary frequency regulation of doubly fed induction generator (DFIG) using the dynamic power flow is proposed. The equivalent inertia of the DFIG is decided by the inherent inertia and the rotor speed. Its captured power and rotor speed respond to the change of the system frequency. The constraints of the DFIG and power system are solved simultaneously to quantify the active loss of the DFIG. Then, the power flow is solved alternatively with the dynamic equation describing system frequency. The numerical results validate the feasibility of the proposed model and quantify the frequency‐support capability of the DFIG. The proposed model helps to balance the utilization of wind power with the stability of system frequency, while reducing the reserve requirement to the SGs.

Analysis of Frequency Regulation Capability of Doubly Fed Induction Generator and Supercapacitor Energy Storage Based on Dynamic Power Flow

“…The releasable kinetic energy of the DFIG rotor is affected by various factors, including the wind speed, the deloaded operation, and the amount of active power reserve. The calculation of the equivalent inertia time constant of the DFIG within different wind speed sections is shown below [27].…”

Hierarchical Predictive Control to Frequency of DFIG‐Integrated Power System Based on Improved Dynamic Power Flow

“…By predicting the torsional angle and pitch angle, the active power output as well as the mechanical and electromagnetic torques are reduced (seen in Fig. 17 Although the optimization goal in (21) includes both the upper and lower level, hierarchical strategy helps to improve efficiency of the optimization process. The upper level prescribes adjustment to the DFIG power output for the frequency regulation.…”

“…Effectiveness of the MPC relies on accuracy of the prediction model. To predict the average system frequency, dynamic power flow (DPF) algorithm using the equivalent inertia is often used [19–21], with reduced calculation effort compared with full‐order time domain analysis [22]. However, some simplifications to the SGs and the DFIGs in the existing DPF model may reduce the prediction accuracy: For the SGs, the response of the mechanical power to the frequency deviation is mainly decided by the governors.…”

Solution of dynamic power flow technique considering governor nonlinearity

“…11 While subject to some events like generator tripping and load variation, power system responds according to its inherent characteristic that all connected equipment operate in a closed-loop under droop control when the regulation of generators in open-loop is not applied. On account of calculating the generation change of all units in post-contingency steady state, literature [12][13][14] combine the characteristic equations of dynamic components and network equations to simultaneously obtain algebraic and differential variables. It accords with the practical situation, but more variables are brought into computation.…”