MAESHA

1. Description of the Use Case

1.1. Name of the Use Case

1.2. Version Management

1.3. Scope and Objectives of Use Case

1.4. Narrative of Use Case

Short description

This high-level use case describes different scenarios incl. all required steps for the implementation of a tender based frequency control system. The UC differentiates between FCR (frequency containment reserve) and FRR (frequency restoration reserve) services. The explained approach is technology agnostic and supports any kind of flexibility resource, that can meet the technical requirements for balancing service provision. A common approach to handle different technologies for flexibility provision (industrial demand response, residential demand response aggregated by a VPP, smart charging of electric vehicles, aggregation of renewables (PV) via a VPP, battery energy storage, power-to-hydrogen electrolyser) is explained.

The scope of the use case includes dimensioning of balancing service reserves for an islanding system, prequalification of suitable distributed energy assets and intermediary platforms (Virtual Power Plants, VPPs), tendering and contracting balancing services, balancing service activation, monitoring, validation, and remuneration.

All periodic communication between the system operator and the market participants, like bidding, monitoring and activation is organized via a Flexibility Management and Trading Platform (FMTP).

The use case focuses on the situation on the Island of Mayotte and aims to adapt to the historically grown infrastructure and processes, but also takes into account updates of the system operators SCADA in the near future.

Complete description

Introduction to balancing services for frequency control

The system operator Electricité de Mayotte (EDM), responsible for grid operation and supply of electric energy, needs to maintain the network frequency within a narrow bandwidth (+300 / -200 mHz) around 50 Hz. Frequency deviation is a consequence of an imbalance between generation (feed-in to the grid) and consumption (extraction from the grid) including losses of the grid itself. These imbalances are mainly caused by unpredictable fluctuations of the load (low impact on the grid frequency), general imprecisions in the load forecasting that cause improper generation schedules (medium impact) or rare fault-induced disconnection of entire branches or substations or even unexpected loss of generation (high impact). Until now, the electricity system in Mayotte relied on fast adaption of the generation of spinning diesel engines to balance the load fluctuations. These diesel engines also cover for the main generation schedule.

The mechanisms to maintain the grid frequency within a narrow bandwidth can be distinguished between three main types of control, as shown in Figure 24. After an incident like the unexpected outage of a generator, the imbalance between load and generation causes an immediate decrease of the grid frequency, which is mainly limited by the kinetic energy stored in spinning machines (synchronous inertia). The higher the inertia of the rotating machines connected to the grid, the lower the gradient of frequency change (Df/Dt), also known as rate of change in frequency (ROCOF). The frequency stabilization by inertia is a physical effect, responding spontaneously to any frequency gradient and acting in both directions. New generations of inverters can provide a frequency gradient dependent feed-in (with only a minor time lag), which can be considered as “virtual inertia”.

[See figure “Overview of phases of frequency control after a major outage” below]

The frequency containment reserve (FCR), also known as primary control, provides a variable feed-in linearly depending on the deviation of the frequency (Df) from the target value of 50 Hz. FCR is required to act very fast. The required full activation time (FAT) is determined by the considered maximum imbalance (e.g., due to loss of the largest generation unit in the system), the maximum allowed frequency deviation and the typical inertia of the system. FCR is a very fast service that requires frequency measurements and control logic directly at the providing asset, usually a generator or battery. Some loads controlled by power electronics might also be feasible to provide FCR. Usually, FCR is a symmetric service that acts in both directions. The linear function of FCR power only depending on the frequency deviation enables a fast response to limit the frequency deviation but does not allow to bring the frequency back to the target value. Some transmission system operators (TSO), e.g., in the NORDPOOL, differentiate between Frequency Containment Reserve for Normal Operation (FCR-N) and Frequency Containment Reserve for Disturbances (FCR-D). FCR-N is a symmetric service providing upregulation and downregulation with a linear characteristic while FCR-D differentiate between upward (increase feed-in or decrease consumption) and downward (decrease feed-in or increase consumption) regulation. FCR-D is only activated after exceeding a threshold value of frequency deviation.

[See figure “FCR architecture overview” below]

The frequency restoration reserve FRR is managed by the system operator (SO) using the automatic generation control (AGC). The AGC calculates setpoints for multiple balancing providing assets (generators, batteries but also fast and precisely controllable loads like electrolyser). After reception of the setpoint the assets will adapt the power output within a defined FAT that may be longer than required for FCR. The AGC aims to bring the system frequency back to the target value. FRR requires reliable communication between the central AGC and the distributed assets. FRR can be divided into positive products for upward control and negative products for downward control. European TSO differentiate between faster, automatically controlled reserves (aFRR), that follow to instantaneous setpoints, and slower reserves that might be manually controlled (mFRR) and follow to received schedules.

[See figure “FRR architecture overview” below]

FCR and FRR provision in Europe usually require active power measurements with high precision (e.g., 0.5% error class) and submission of data points to the SO in short intervals (e.g., 1-2 s) for the purpose of real-time monitoring of provision and ex-post validation of the provided services.

Additional Emergency measures will be activated in case that the frequency regulation system failed, and the frequency deviation exceeds defined thresholds. Emergency measure can include load shedding, disconnection of large, robust consumers or disconnection of generators. The rules for frequency protection devices to disconnect sensible assets in case of high frequency deviations must be defined accordingly to support system frequency stabilization and to avoid negative feedback on the frequency control mechanisms.

Context

The rising number of PV power plants to be installed and connected to the main grid in Mayotte may increase the difficulty of frequency control as the production is highly dependent on weather conditions challenging to forecast (e.g., a passing cloud leads to a decline in PV production) which may increase the imbalances between generation and consumption. With increasing number of PV generation, partly replacing diesel generators the ratio of spinning machines in the system will be reduced which has negative impact on the synchronous inertia. To avoid reaching low frequency thresholds leading to load shedding (48.5 Hz, 48 Hz and 47.5 Hz), the French Energy Regulatory Commission (CRE) granted an exemption to EDM to operate the grid at a higher frequency. The current mean frequency value is thus of 50.15 Hz, higher than the 50 Hz stipulated in the EU Electricity Network code.

The main balancing service to cope with the frequency deviation currently applied on the island of Mayotte is the “primary reserve” (covering FCR and FRR), which is estimated at 15% of the daily demand and mainly supported by the EDM diesel generation sets of Longoni and Badamiers. The generators are limited to operate at 80-85% of their maximal capacity. For the past few years, the primary reserve hadn’t exceeded 8 MW, but this will change soon with an expected rising demand and RES integration.

To stabilize the frequency in the island and ease the penetration of renewable energy, the French Energy Regulatory Commission CRE launched a call for tender to install a battery for frequency control in July 2018. This 4 MW/2 MWh battery should be installed and be ready to operate in October 2021. Following this installation, the exemption (of higher system frequency) should disappear for the time-being. It is estimated that further investments will be needed to fulfil the requirements that are foreseen in the future.

One of the goals when considering the frequency use case is to find a way for moving from the energy assets providing frequency services with the help of fossil fuel to assets using renewable energy sources (RES) and Battery Energy Storage Systems (BESS). To further reduce the primary reserve provided by the EDM’s diesel generation sets new sources for providing frequency regulation services are needed to have a direct impact on reduction of CO2 emissions.

The main challenges when implementing the frequency control framework are related to the identification of sufficient assets from RES to reduce the required capacity of fossil fueled generators that are capable to provide similar reliable frequency services.

The use case describes the interactions between the main actors and platforms but doesn’t discuss the details of the balancing products. The details of the designed balancing products will be defined Deliverable D4.1 Report detailing the energy market framework and specific product design details.

For the MAESHA project, it has been decided to examine how different flexibility sources could support the frequency control on the island:

•Industrial Demand Response

Industry’s main purpose is manufacturing of goods or provision of other services. Some industrial assets are additionally able to provide a certain help to the system operator by adjusting their internal manufacturing process and thus increase or decrease the consumption for the time being (load shifting) and help minimizing the frequency deviation. Such industrial energy assets usually have some restrictions, such as limited duration of delivery (e.g., max 4 h), poor controllability (e.g., ON-OFF operation), or can provide such action only at a certain time of the day or year. Therefore, industrial demand response is not considered as a primary source for providing balancing services to the power grid, but they may serve as secondary source for additional support when other services are already fully activated (e.g., for emergency measures).

• Residential Demand Response managed by a virtual power plant (VPP)

Residential customers may have flexible loads that end-users do not necessarily need instantaneously to ensure their comfort, e.g., air-conditioning units and electric heating, but also dishwashers, washing machines, cloth dryers, etc. Optimally controlling the on/off times of these devices, considering local frequency deviations, can help in ensuring the frequency stability. Depending on the characteristics of the device, the activation time and activation duration differ. Heat pumps or air conditioning units can be used for frequency response, considering the heat storage capacity of the building or heat storage in a hot water tank. The activation duration depends upon the stored heat capacity in the building or the tank and the comfort requirements of the end-users. These units can be activated very fast (remote switch-off) but their availability is difficult to forecast.

• Smart Charging of electric vehicles (EV) and vehicle to grid (V2G)

Smart charging of EV can be a source of consumption flexibility and theoretically be used even for balancing services. The challenges for provision of FRR by an EV are linked to the prediction of the charging process’ time and duration as well as the limited hours per day, when EV charging can be used for load shifting. Nevertheless, the forecasting of consumption and flexibility becomes easier on a fleet of EVs, as such an aggregate of a higher number of EV’s can provide ancillary services reliably using a minor share of the predicted consumption. Load reduction in EV charging can be achieved by reducing the charging power (e.g., switch from 3-phase to 1-phase charging) of a certain number of vehicles. Advanced fleet management might also allow downward services by increasing the charging power during the requested period. Feed-in of energy stored in the EV’s batteries (V2G) will been investigated as another possibility of upward regulation by EVs but comes with practical drawbacks like possible reduction of battery lifetime and the need for bidirectional inverters. Due to the nature of the fleet management and lower frequency of data acquisition, EV charging will be preferably applied for mFRR than for aFRR or FCR like frequency services.

• Virtual Power Plant (VPP) aggregating RES

The variability of renewable energy sources, such as wind and solar, are causing continuous, small frequency deviations due to their hard to predict short-term dynamics and their lack of synchronous inertia to stabilize the frequency during disturbances. Lowering the output of PV plants (downward regulation) during high frequency periods can support frequency stabilization. If PVs are operated below their maximal inverter power, PV plants can inject additional power into the grid with different activation times, ranging from seconds to minutes during low frequency periods (upward regulation). The latter will result in a reduction of overall generation or require the installation of PV batteries. The activation duration depends on the amount of reserve kept for upward frequency response and will be the result of a cost-benefit analysis, where the outcome depends on the remuneration of the different frequency response products compared to the value of electric energy fed-in by PV. In the last years, much development effort has been made on virtual inertia provided by PV and wind power, which might become state-of-the-art within the next decades.

• Battery Energy Storage System

By supplying or absorbing power in response to deviations from the nominal frequency and imbalances between supply and demand, the rapid response of a BESS will provide a frequency stabilizing services. The fast response capability of BESS allows them to participate in all kinds of frequency response (e.g., FCR, FRR) or even a fast or enhanced frequency response markets (activation in less than 5 s). The BESS will also provide virtual inertia by modulating active power as a function of the ROCOF. The duration of the service provision will be determined by the SoC. BESS providing ancillary services will require an additional charge management to maintain the state of charge (SOC) within predefined limits (e.g., 30%<SOC<70%) in order to ensure the continuous availability of upward and downward regulation ability. Load management (consumption or feed-in) is based on schedules and should be communicated with the SO, e.g., via an intraday program. The BESS should be able to provide multiple balancing services and perform load management in parallel.

• Power-to-Hydrogen system

Proton Exchange Membrane (PEM) electrolysers have the capability of modifying their load rapidly with very high ramps rates (i.e., within seconds) and within a wide operational range up to the nominal power. This flexibility can be utilized for large range of frequency regulation (e.g., FCR, aFRR, mFRR). Despite the hydrogen storage capacity, there is no limit in the duration of the service as the service is provided by reducing/increasing the load of the electrolyser.

These DER provide their flexibility to the SO via the FMTP, as indicated in Figure below.

[See figure “Architecture overview for frequency control in MAESHA” below]

Functions

This Use Case relies on the following functions: •Asset contraction and technical preparation, incl. pre-qualification •Detection of frequency deviations •Evaluation of flexibility available from different assets or via intermediate platforms •Contracting balancing service products •Calculation of setpoints by the AGC of the SO •Flexibility activation through the Flexibility Management and Trading Platform (FMTP) •Monitoring of service provision •Settlement process to remunerate flexibility activation

This Use Case supports a technology-agnostic approach for provision of balancing services by central or decentralized energy assets. In the MAESHA project, the following technologies are aimed to be investigated in the scope of the use case demonstration: •Detection of frequency deviations, central by SO or decentral by the DER •Frequency regulation by industrial DR •Frequency regulation by residential DR via VPP •Frequency regulation by Smart charging/V2G •Frequency regulation by RES via VPP •Frequency regulation by BESS •Frequency regulation by P2H system

1.5. Key Performance Indicatiors (KPI)

1.6. Use case conditions

1.7. Further information to the use case for classification/mapping

1.8. General remarks

2. Diagrams of Use Case

3. Technical Details

3.1. Actors

3.2. References

4. Step by Step Analysis of Use Case

4.1. Overview of Scenarios

Notes

4.2. Steps – Scenarios

5. Information Exchanged

6. Requirements (optional)

7. Common Terms and Definitions

8. Custom Information (optional)