Validated electrical performance models of power system components are required to support a range of power system planning studies, interconnection studies and plant design. This includes steady-state (power flow) models, detailed transient models for the study of electromagnetic interactions, dynamic models for the study of electromechanical phenomena, and short circuit models. Transmission and distribution simulation platforms commonly used by system planners do not presently have full-featured models for PV systems representation. Interest in positive-sequence power flow and dynamic models has increased recently due to the trend toward larger PV system plant sizes, both commissioning and interconnection applications, and interest in understanding the possible impacts of high PV penetration levels on grid performance. Compared to conventional generator models, PV system models are very much a work in progress. This paper describes advances in power flow and dynamic modeling of PV systems for grid planning studies based on on-going efforts by the Western Electricity Coordinating Council (WECC) Renewable Energy Modeling Task Force (REMTF). The goal of REMTF is to improve the adequacy, availability and accessibility of PV system models for grid planning and interconnection studies.
PV SYSTEM MODELSIn the past, most grid-connected PV deployment consisted of small isolated residential and commercial-scale installations on distribution systems. Concerns about safety and grid compatibility were addressed by adherence to IEEE 1547 standards and associated inverter certification. A formal evaluation involving technical studies and simulations was seldom required. Currently applicable interconnection procedures still allow for small PV systems to be installed with minimal technical evaluations when the systems are relatively small and the penetration level is relatively low. Today, many proposed PV installations are large enough to warrant a full interconnection study that involves power flow, dynamic and short-circuit simulations. A different set of standards and procedures apply, including those issued by the North American Electric Reliability Corporation (NERC) and the Federal Energy Regulatory Commission (FERC). Access to adequate PV system models for regional planning requirements and to process the growing queue of large utility scale PV interconnection applications needs to be improved.Currently, standard library models for PV systems are not widely available. Interconnection studies are typically conducted with manufacturer-specific, user-written models that tend to be proprietary. These types of models are discouraged for the purposes of regional planning studies. Confidentiality issues complicate a study process that often involves multiple stakeholders. In addition, manufacturer-specific models are difficult to maintain, document and use, compared to standard library models. Even in the context of interconnection studies, the userwritten models can become very difficult to work with in practice. In ...