Dynamic Droop-based Inertial Control of a Wind Power Plant

Abstract

-The frequency of a power system should be maintained within the allowed limits for stable operation. When a disturbance such as generator tripping occurs in a power system, the frequency is recovered to the nominal value through the inertial, primary, and secondary responses of the operating synchronous generators (SGs). However, for a power system with high wind penetration, the system inertia will decrease significantly because wind generators (WGs) are operating decoupled from the power system. This paper proposes a dynamic droop-based inertial control for a WG. The proposed inertial control determines the dynamic droop depending on the rate of change of frequency (ROCOF). At the initial period of a disturbance, where the ROCOF is large, the droop is set to be small to release a large amount of the kinetic energy (KE) and thus the frequency nadir can be increased significantly. However, as times goes on, the ROCOF will decrease and thus the droop is set to be large to prevent over-deceleration of the rotor speed of a WG. The performance of the proposed inertial control was investigated in a model system, which includes a 200 MW wind power plant (WPP) and five SGs using an EMTP-RV simulator. The test results indicate that the proposed scheme improves the frequency nadir significantly by releasing a large amount of the KE during the initial period of a disturbance.

A study on frequency adjustment mechanism for wind turbine generation systems

“…This section describes problems of active power control and regulation of rotor angular speed in the conventional approaches. Figure 1 shows a typical governor controller [4]. In Figure 1, the speed regulation factor, R, can be calculated by using the deviation between the standard power grid frequency and the actual one as defined in Eq.…”

“…Under these circumstances, frequency control mechanisms for the WTs have been actively developing especially in recent years. In prior studies, the hidden inertia, the rate of change of frequency (RoCoF) loop and the droop are commonly adopted [4].…”

Frequency Support of Smart Grid Using Fuzzy Logic-Based Controller for Wind Energy Systems

“…Variable droop controller was proposed to enhance the response of WES based on doubly fed induction generator DFIG in reference [30]. The concept of droop can be implemented in the local controller of the WES, at the wind farm level, or to the coordinated distributed generator in the smart grid [31][32][33][34][35][36][37][38][39][40].…”

Hybrid Reference Function for Stable Stepwise Inertial Control of a Doubly-Fed Induction Generator

“…While FBIC contributes to an increase in the frequency nadir (FN), it shows a relatively slow response, because the additional power from the auxiliary loops relies on frequency variations. On the other hand, to improve the performance of inertial control, the gain of frequency deviation loop was regulated depending on the rotor speed of WTGs [8] and the ROCOF [9].…”

“…Inertial control can be divided into two groups: frequency based inertial control (FBIC) [4][5][6][7][8][9] and stepwise inertial control (SIC) [10][11][12][13][14][15]. Based on the measured frequency, FBIC employs one or two auxiliary loops: a rate of change of frequency (ROCOF) loop [4], a frequency deviation loop [5], ROCOF and frequency deviation loops [6], and maximum ROCOF and frequency deviation loops [7].…”