In a planning stability study focusing on a specific wind power plant (WPP), it is dispatched at full output. Its dynamic response is not expected to be noticeably affected by the loading of WPPs in close electrical proximity. To investigate the validity of this approach and better understand the mutual effect of the loading levels of nearby WPPs on their dynamic responses to power system faults, four case studies with different local areas and wind turbine generator (WTG) devices are performed. Fault simulations are carried out on real large power system databases. While most numerical experiments confirm the approach, some others suggest that it does not necessarily lead to the severest stability conditions. Further EMTP-type analysis is needed. Meanwhile, and especially when a planning study identifies concerns about the stability of a WPP and/or its fault ride through capability, more combinations of WPP loading levels should be evaluated.
Wind energy has become one of the fastest advancing alternative energy technologies. In power system planning studies, stability evaluations for a new wind power plant (WPP) are based on time-domain contingency simulations. Their scenarios mostly involve short circuit faults differing in location, type and clearing procedure. To carry out the simulations, positive-sequence commercial software programs are applied, along with simplified wind turbine generator (WTG) dynamic (stability) models intended for transient stability studies. Essential information about the development and validation of such WTG models can be found in -.
Given the multitude of factors affecting the dynamic response of a WPP and, on the other hand, the fact that planning study conclusions are to be made based on a limited number of simulations, the role of study methodology is crucial. In particular, contingency simulations need to be run on a representative set of power flow cases reflecting different load conditions and generation dispatch scenarios. Most often, seasonal high and low load conditions, normal or stressed, are assumed for the power system.
When a planning stability study focuses on a specific WPP, it is dispatched at full output, which is widely thought to be most limiting in terms of its stability performance. When another WPP is very close electrically and, especially, when it shares the same point of interconnection (POI), a potential for mutual dynamic effects should be evaluated. As an example, the investigation of control interaction between multiple WPPs in close electrical proximity  shows that their voltage regulators need to be coordinated. However, the dynamic response of a WPP is usually not expected to be noticeably affected by the loading of nearby WPPs. Therefore, their loading is usually defined by the logic of the overall power system dispatch, desired interface flow levels, etc.
Simulation experience, however, has provided evidence that this approach does not necessarily lead to the severest stability conditions, which became an impetus for this work. In particular, the assumption of full output does not necessarily ensure the worst-case stability performance of a WPP and, therefore, more operating conditions should be simulated to adequately assess the fault ride through (FRT) capability of a WPP , . The described approach to setting nearby WPPs’ loading levels also needs more justification.
This paper discusses setting the loading level of a WPP and the mutual effect of nearby WPPs’ loading levels on their dynamic responses to close-in faults. The investigation is based on four case studies with real different local areas and WTG devices. Fault simulations with the Siemens PTI PSS/E software program are carried out on real large power system databases developed by the New York Independent System Operator (NYISO). Since WTG models intended for stability studies are known to be able to exhibit questionable behavior , , the paper considers model features essential in terms of simulation of partially loaded WTGs.
The work is part of NYISO activities intended to ensure the high quality of wind generation interconnection studies.
II. STUDY METHODOLOGY
At the core, the investigation is based on a large number of numerical experiments on a representative set of network cases with real WPP projects utilizing different WTG devices.
A. Local Area
Here, a “local area” of the power system is defined as its relatively small subsystem that includes three nearby WPPs (WPP-1, WPP-2 and WPP-3) whose mutual effect is evaluated. A schematic diagram of a local area is shown in Fig. 1. This topology is only an example; note that the transmission lines directly connecting WPP-2 to the two other WPPs are present only in case study CS#1.