Aggregation of Type-4 Large Wind Farms Based on Admittance Model Order Reduction

Abstract

This paper presents an aggregation technique based on the resolution of a multi-objective optimization problem applied to the admittance model of a wind power plant (WPP). The purpose of the presented aggregation technique is to reduce the order of the wind power plant model in order to accelerate WPP simulation while keeping a very similar control performance for both the simplified and the detailed models. The proposed aggregation technique, based on the admittance model order reduction, ensures the same DC gain, the same gain at the operating band frequency, and the same resonant peak frequency as the detailed admittance model. The proposed aggregation method is validated considering three 400-MW grid-forming Type-4 WPPs connected to a diode rectifier HVDC link. The proposed aggregation technique is compared to two existing aggregation techniques, both in terms of frequency and time response. The detailed and aggregated models have been tested using PSCAD-EMTsimulations, with the proposed aggregated model leading to a 350-fold reduction of the simulation time with respect to the detailed model. Moreover, for the considered scenario, the proposed aggregation technique offers simulation errors that are, at least, three-times smaller than previously-published aggregation techniques.

Modal Aggregation Technique to Check the Accuracy of the Model Reduction of Array Cable Systems in Offshore Wind Farms

“…The voltage drop [21][22][23], the power loss #1 [42], and the power loss #2 [22,24,28] aggregation techniques use weighting of the individual impedance with respect to the amount of current injected that it carries (per unit) (The IDs added for the power loss methods is our notation.). In Figure 1a, an OWF is represented by M feeders, with corresponding N m WTs of the individual feeder, m. In Figure 1b, it is shown that the WT itself is simplified with a current source connected to the grid bus with the voltage v g and an associated current source, representing current injections from the grid, i g .…”

“…In [21][22][23], a voltage drop-based analysis of the equivalent string impedance in the collector system is considered. In [24][25][26][27][28], a similar approach is noted, but the individual impedance is weighted with respect to a consideration of power losses.…”

Small‐signal stability and fault performance of mixed grid forming and grid following offshore wind power plants connected to a HVDC‐diode rectifier

“…1. WTGs have been aggregated as per [14]. Therefore, the considered system shows a great level of granularity, so results can be obtained at the wind turbine and string levels, at a reasonable computational cost.…”

“…Figs. [13][14][15][16] show the response of the system to a fault in the offshore AC-grid ring bus (see Fig. 1).…”

Impedance-based Stability Analysis for HVDC Diode-Rectifier Connected Off-shore Wind Farms

“…As Z W T is designed to be stable, the stability of the system can be found by checking the generalized Nyquist criterion on the loop impedance L dq = Z W T Y DRU . The considered WPP consists of 50 WTGs arranged in 6 strings, and it is aggregated using system order reduction techniques which ensure a faithful representation of the array cable main resonant peak [18].…”