Inertia Estimation of Wind Power Plants Based on the Swing Equation and Phasor Measurement Units

Abstract

High penetration of wind power plants may have an adverse impact on power systems’ stability by reducing the inertia, and problems like frequency stability could appear due to total inertia in the system being reduced, making the power system more vulnerable to disturbances. However, most recent grid codes include an emulation inertia requirement for wind power plants, because modern wind turbines are capable of providing virtual inertia through power electronic converter controls to improve frequency stability issues. Because of this, it is necessary that the inertia estimation analyze and quantify the impact of the inertia reduction in power systems. In this paper, an implementation of a methodology for the inertia estimation of wind power plants is presented. It is evaluated through synchrophasor measurements obtained from a Real-Time Digital Simulator (RTDS) implementation, using industrial Phasor Measurement Units (PMUs). This methodology is based on the swing equation. Furthermore, a comparison of the results obtained between two professional tools RSCAD and DIgSILENT PowerFactory is performed, in order to evaluate the accuracy and the robustness of the methodology. This methodology is applied for the inertia estimation of an equivalent of the southeast zone of the Mexican power system, where there is a large-scale penetration of wind power plants. The results demonstrate that this methodology can be applied in real power systems using PMUs.

Inertia Provision and Small Signal Stability Analysis of a Wind-Power Generation System Using Phase-Locked Synchronized Equation

“…Therefore, Equation (8) is defined as the swing equation of the DFIG, which is established on the PLL model, the active power equation, and the voltage-oriented control from (1) to (5). According to (8), the swing equation of the DFIG has the same components with the rotor motion equation, including the inertia constant, the damping coefficient, the synchronizing torque, and the power angle. In the next sections, the physical significance of the model will be explained further, and the accuracy of the model will be verified in the simulations of inertia provision and damping analysis.…”

“…Note that the typical values of PLL parameters are K P_PLL = 40 and K I_PLL = 100 [27]. According to (8), the value of M w is small enough to be neglected under typical values, which explains why the DFIG could not respond to the frequency excursion under the general state. If both of K P_PLL and K I_PLL decrease, M w will increase, and the inertial response ability for the DFIG will be enhanced.…”

“…Different from the synchronous generators (SGs), the DFIG operates at the maximum power producing point for a given wind speed [7]. For this reason, the system frequency is decoupled from the partially rated power converter, which results in a loss of ability in the DFIG to provide inertia and frequency support [8,9]. The reduced inertia has also presented challenges to the system small signal stability [10,11].…”

Special Issue on “Wind Energy Conversion Systems”

“…Large-scale wind power integration has changed the power system inertia and could affect the system frequency control and stability. The paper "Inertia Estimation of Wind Power Plants Based on the Swing Equation and Phasor Measurement Units" [13] presents a method for the inertia estimation of wind power plants based on the swing equation and phasor measurement units (PMUs). The proposed method has been applied to the case study of a power system with large-scale penetration of wind power plants.…”

Virtual Synchronous Control Based on Control Winding Orientation for Brushless Doubly Fed Induction Generator (BDFIG) Wind Turbines Under Symmetrical Grid Faults

“…The recent controls for the BDFIG system use phase-locked loops (PLLs) to synchronize the vector control system with the grid voltage, and such controls have no contribution to the system stability. Recently, many control methods, such as virtual inertia control [13,14], droop control [15], pitch angle control [16], coordinated control [17], and the virtual synchronous generator [18], have been proposed for DFIG or grid-tied converters. Among them, the virtual synchronous generator uses extra short-term energy storage units plus Virtual Synchronous Control (VSC) to simulate the virtual rotor inertia [19,20].…”