The Basics of a VPP
A Virtual Power Plant (or VPP for short) is a concept developed in the early 2000’s consisting of an aggregation of different power generation and/or consumption units that are operated in a coordinated manner so that from the system’s point of view this set behaves as one single power plant. The assets under a VPP can include conventional generation units (gas or pump hydro power plant), renewable resources (wind, solar) but also storage units or even flexible power consumers. VPPs have been used primarily to aggregate small generation units (e.g. rooftop photovoltaic panels) to enable their participation in energy markets.
The concept explored in EU-SysFlex’s WP7 takes a different approach: by jointly operating and dispatching renewable power plants with conventional, controllable power plants under the same system – a Virtual Power Plant – we can smooth out the intermittency of renewables. The result is a new Power Plant that from the power system’ perspective behaves as a conventional power plant (increasing and decreasing output when needed) while integrating large shares of Renewables “under its hood”.
The diagram below shows how the demonstration of the Portuguese utility-scale VPP will look like.
Portuguese utility EDP will provide the two types of assets:
- EDP Produção will have large Pump Storage Hydro Plant: Venda Nova III (756 MW rated power)
- EDP Renewables will supply two wind farms, Alto da Coutada and Falperra (totalling 170MW)
The VPP itself will be integrated in EDP’s trading unit’s (EDP UNGE) systems where data of wind forecast and information of each power plant’s status is fed to the VPP’s algorithm. EDP UNGE will oversee the participation of the VPP in five different Energy and Ancillary Services markets: Day-ahead, Intraday, “Secondary” and “Tertiary” reserve and Cross-border Intraday market.
All three companies of EDP are part of the EU-SysFlex, working under the coordination of EDP CNET, Work Package 7 leader.
Inside the VPP
The main steps of the process of the VPP are depicted in the figure below as the modules composing the VPP:
The Forecasting Module gathers the forecast of natural resources (Wind, Water inflow to the hydro plant) as well as the availability of the units in the VPP to assess the potential generation and also forecast the system’s situation and market prices. With this information, the dispatch of each unit is performed in the Dispatch Optimization module and the bids are then sent to the different markets. The Results module gathers the different market results and sends the power setpoints to each unit. All these services are based on a Cloud-based Backend service where a user interface allows the follow up of each of these actions.
The Virtual Power Plant, developed by Siemens (also a partner in EU-SysFlex) is divided into two major components, the VPP Core and the VPP Controller. The VPP Core is the “brains” of the system: responsible for performing the stochastic optimization of the generation units through a workflow engine deployed into a cloud-based which allows the periodic execution of each task and supports functions like data collectors & persistence, user interface, monitoring & logging. The VPP Core creates the bids to the markets (capacities and prices), fetches the market clearing results and then sends it to the VPP Controller, which acts as the “muscle” of this operation, as it implements the VPP Core results and provides feedback from the units to the VPP Core. Once the market is cleared and the dispatch optimization is performed, the VPP Controller also sends the power setpoints to the units and at the same time and return the information regarding the availability of the generation resources back to the VPP Core to be used for the next optimization process. The VPP Controller also manages the imbalances between the scheduled and actual dispatch, using the dispatchable units (hydro in our case) to correct the possible deviations from the non-dispatchable (wind, in this case) units.
Testing the VPP
The demonstration of the operation of the VPP in EU-SysFlex’s WP7 will feature two sets of tests: offline and online.
For the offline testing, the VPP tool will be calculating the appropriate bids for the VPP but still as a simulation only as test data (not real data) will be fed to the tool, allowing the test of widely varied conditions (high/low wind availability of renewables, different market prices, etc). The overall goal of the offline testing will be to provide results from the various conditions and use the data to fine tune the algorithm for the online testing. Offline testing is expected for July 2020.
The online testing will be in close coordination with Portuguese TSO REN (member of the project’s Advisory Board) and will be performed under a two-week testing period, in which the VPP operation will be enabled upon REN’s authorization. The aim is to evaluate in real conditions the VPP response, namely from the VPP controller, to the wind farms’ imbalances monitored in real-time, as well as the dispatch schedule update doing to the participation on the intraday or XBID market during the testing days. Online testing is scheduled for September and October 2020.
The possibilities and expected benefits
The concept of the VPP can expand beyond the hydro+wind configuration tested in Portuguese Demo: the VPP is designed to be “asset-agnostic” so that elements like energy storage, demand response enabled consumers or solar PV can be easily integrated.
As utilities like EDP explore ways of increasing the efficiency of the management of their generation portfolios, the aggregation of intermittent energy sources (wind or solar) with controllable power plants (conventional like gas or hydro) granted by the VPP is expected to yield economic and technical benefits. The flexibility expected from this aggregation will allow the VPP coordinator (acting as its own Balance Responsible Party) to make optimal bids to the market and manage the portfolio more efficiently and automatically as well as avoid costs of penalties for imbalances. The VPP is also expected to bring benefits to the grid operator, by reducing the need to procure balancing reserves, bringing efficiency to the whole energy value chain and paving the way for further integration of intermittent renewable sources – to levels above 50%.
Written by: Miguel Jorge Marques, EDP CNET
EDP Group is a large multinational and integrated energy player, with strong presence in 15 countries worldwide, especially in Europe, US and Brazil. EDP operates across all the energy value chain in generation, distribution, energy trading and retail of electricity and gas, with a specially relevant role as wind energy developer (#4 in the world in installed capacity). EDP is in project EU-SysFlex with its R&D center, EDP CNET coordinating the efforts of EDP Produção (operator of conventional generation portfolio, including Hydro), EDP Renewables (operator of the renewable units, including wind) and EDP SA – UNGE (Energy trading unit).
Disclaimer: blog entries reflect individual views of the author(s) that may not reflect official positions or communication of the project / project consortium.
Author : EU-SysFlex Project