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This paper presents a dynamic event data-based stability risk assessment method for power grids with high penetrations of inverter-based resources (IBRs). This method relies on obtaining the IBRs’ DQ admittance through dynamic event data and computing the system’s eigenvalues based on the admittance models. Two critical technologies are employed in this research, including time-domain and frequency-domain data fitting and $dq$ -frame voltage and current signal derivation. The first technology is key to obtaining the $s$ -domain expressions from the transient response data, and the $s$ -domain DQ admittance model from the frequency-domain measurements. The second technology is key to obtaining the $dq$ -frame voltage and current signals from either the three-phase instantaneous measurements or the phasor measurement unit (PMU) data. The method is illustrated using data generated from a Type-4 wind power plant modeled in PSCAD. This paper demonstrates the technical feasibility of the proposed approach. [ABSTRACT FROM AUTHOR]

In this paper, an analytical two-machine equivalent method of DFIG-based wind power plants (WPPs) is proposed. Through simulations of a 49.5 MW WPP, the root causes of errors of the single-machine equivalent are identified. Taking a four-machine WPP as an example, analytical expressions of fault-ride through (FRT) behaviors of the WPP model and its single-machine equivalent model are derived, and root causes of errors are revealed in theory including: inconsistent transient power behaviors in the initial FRT stage; unequal quasi-steady-state active power during a fault; and mismatching initial points and ramp rates of active power after the fault clearance. To eliminate equivalent errors, an improved equivalent method is proposed with two steps: 1) Group wind turbines into two clusters by the crowbar actions and represent them as two equivalent machines; 2) Correct their controller reference settings based on the derived FRT behavior expressions of the detailed WPP. Simulation results verify that the proposed method can accurately reproduce FRT behaviors of the WPP under various wind scenarios and voltage dips. [ABSTRACT FROM AUTHOR]

This article analyzes the transient stability of an offshore wind farm connected via modular multilevel converter (MMC)-based high-voltage direct-current transmission system. The wind farm is composed by full-scale type-4 wind turbines, whereas short-circuit faults occurring in between the MMC and wind farm are considered. The MMC tends to be switched to the current limiting mode or the overmodulation mode during the ac-side fault, which further interacts with the control systems of wind turbines, complicating the transient stability problem of the system. Hence, in this work the parametric impacts of the phase-locked loop of wind turbine converters and over-current/-modulation limiters of the MMC are revealed analytically, and further corroborated by time-domain simulations. [ABSTRACT FROM AUTHOR]

An improved single-machine equivalent method is proposed for wind power plants (WPPs) by calibrating the postfault power recovery behaviors. A real WPP is simulated with extensive wind scenarios to evaluate the traditional single-machine equivalent model, and it is found that its equivalent error is mainly resulted from the postfault recovery process. The simulation analysis further indicates that a wind turbine operating at different wind speeds restores to its prefault active power at a certain ramp rate after fault clearance, with different starting power and different recovery time. Taking a two-machine WPP as an example, the analytical expression for active power of the WPP is derived for the fault ride through process, and thus the equivalent error of traditional single-machine model is found to be resulted from two aspects. One is the mismatch of the starting power of the postfault recovery process, and another is the mismatch of the power recovery rates between the complete WPP and its equivalent model. The analytical expressions are extended to multimachine WPP to calibrate the starting power and the ramp rates of the postfault recovery process. Simulation results show that the proposed method has good performance for various voltage drops, wind scenarios, and grid characteristics. [ABSTRACT FROM AUTHOR]

This paper develops enhanced hybrid generic (nonlinear) models of Type-3 and Type-4 wind power plants (WPPs) and extracts the corresponding linear (small-signal) dynamic models for power system transient stability analysis. The models are hybrid in nature since they consider both continuous states and discrete logic-controlled variables. The introduced enhancements include (i) a freezing function to reactivate reactive power emulator of Type-3 and Type-4 WPPs, (ii) active-current command recalculation step for Type-3 WPP and (iii) elimination of an activating logic of PI-controller limits in real current control path. The main feature of the enhanced models is that they can replicate the field-verified responses of the built-in PSS/E software models in any adopted software platform. It should be noted that the generic models described in the technical literature do not necessarily provide such replication. The paper also deduces small-signal dynamic models of Type-3 and Type-4 WPPs and addresses the multiple eigen structures of the linearized enhanced generic model of Type-3 WPP, which has not been comprehensively discussed in the technical literature. The enhanced nonlinear hybrid models and the corresponding linearized models are evaluated and verified based on time-domain simulation studies in PSS/E and MATLAB platforms, using NPCC system as the test bed. [ABSTRACT FROM PUBLISHER]

This paper presents a general methodology for analysis of sub-synchronous interaction in wind power plants. These include appropriate frequency scanning method for the assessment of the sub-synchronous control interaction, and calculation of the electrical damping provided by the wind turbine generator for investigation of the sub-synchronous torsional interaction. A general formulation of both methods applicable to any given wind turbine and network is presented. A dynamic frequency scanning method for the turbine side is developed which takes account of the turbine nonlinearities and its active behavior. Various aspects that need to be considered when injecting a voltage or current signal into the system for dynamic frequency scanning are discussed in detail. The veracity of these methods is confirmed against electromagnetic transient analyses. The application of these tools and techniques is demonstrated on a practical power system comprising type 3 wind turbines and series compensated lines. [ABSTRACT FROM PUBLISHER]