Emmanuel De Jaeger

Cost-based dimensioning of Battery Energy Storage and energy management system for Frequency Containment Reserves provision

Frequency Containment reserves (FCR), previously called primary reserves, are an important feature insuring safe and reliable operations of the Continental Europe grid. Due to their strong technical requirements, gas and hydro power plants are the almost exclusive provider of FCR. Since gas power plants are becoming less profitable in Europe, a lot of efforts are deployed into FCR diversification. This paper assesses the potential for battery energy storage systems (BESS) to deliver FCR combined with a slow-moving thermal power plant and other emergency solutions such as load shedding and dissipating resistances. A proportional-integral energy management control loop is used whose parameters are tuned by an economic evaluation. We show that economic opportunity already exists today. Some limitations are discussed due to simplifying assumptions. The best solution consists of a 1MW/1.4MWh battery and a 0.09MW power plant per MW of provided FCR reducing by 90% the reservation on power plants.

Provision of primary frequency control with variable-speed pumped-storage hydropower

The development of renewable and intermittent power generation creates incentives for the development of both energy storage solutions and more flexible power generation assets. Pumped-storage hydropower (PSH) is the most established and mature energy storage technology, but recent developments in power electronics have created a renewed interest by providing PSH units with a variable-speed feature, thereby increasing their flexibility. This paper reviews technical considerations related to variable-speed pumped-storage hydropower (PSH) in link with the provision of primary frequency control, also referred to as frequency containment reserves (FCRs). Based on the detailed characteristics of a scale model pump-turbine, the variable-speed operation ranges in pump and turbine modes are precisely assessed and the implications for the provision of FCRs are highlighted. Modelling and control for power system studies are discussed, both for fixed- and variable-speed machines and simulation results are provided to illustrate the high dynamic capabilities of variable-speed PSH.

A methodology for sizing primary frequency control in function of grid inertia

Large increase in wind and photovoltaics will lead to lower and more volatile grid inertia but also to the lack of primary frequency control, i.e. frequency containment reserve (FCR) providers in the Continental Europe Grid. This will therefore impact negatively the frequency dynamics. One potential solution for ensuring the frequency to stay in reasonable bounds is to take the dynamics of potential providers into consideration. From this observation, we develop a novel methodology for having a linear programming problem to select the most suited FCR providers. It is based on the minimization of the overall cost while respecting static and dynamic constraints which are respectively ensuring a sufficient amount of FCR and avoiding too large frequency deviations after a large disturbance. The methodology has been tested on a case with 200 potential FCR providers in function of various grid inertia and load damping factors.

Provision of frequency containment reserves with batteries and power-to-heat

Frequency Containment Reserves (FCR), previously referred to as primary reserves, are an important component for the safe operation of the Continental Europe grid. The growing share of renewables represents a forthcoming challenge since FCR are generally provided by synchronous generators. In this paper, batteries are associated with a power-to-heat system (P2H) composed of electrical resistances, allowing a very high flexibility as well as a valorization of the generated heat. They are controlled to react first, leading to a significant reduction of the battery use while allowing a satisfactory regulation of the batterys stored energy. This is made possible by adding an offset that allows the proposed system to consume power in average. In addition, batteries are controlled to only provide downward regulation and they are consequently smaller than in other propositions. An economic modelling has been realized and based on time simulations with actual frequency data.

A robust convex optimization framework for autonomous network planning under load uncertainty

Autonomous microgrid planning is a Mixed-Integer Non Convex decision problem that requires to consider investments in both distribution and generation capacity and represents significant computation challenges. We proposed in a previous publication a deterministic Second-Order Cone (SOC) relaxation of this problem that made it computationally tractable for real-size cases. However, this problem is subject to considerable uncertainty emanating from load consumption, RES-based generation and contingencies. In this paper, we thus present a robust optimization approach that extends our previous work by including load related uncertainty at the cost of a substantial increase of the computational burden. The results show that significantly higher investment and operational costs are incurred to account for the load related uncertainty.

On decentralized control of small loads and energy rebound within primary frequency control

Decentralized decision making is a promising candidate for cost-effective participation of small electric loads to power system operations. In such setup, individual loads take control decisions based on local information. Local control laws are designed to synchronize individual efforts. Large loads groups may thereby contribute to system stability in a predictable way. In this paper, Energy Constrained Loads (e.g., battery charging, night storage heater) participates in primary control in a communication-free setup. Three different controllers and associated actions are considered: (1) delay at start, (2) regular on/off switching, or (3) proportional power modulation. Control laws are respectively based on discrete thresholds, probabilistic algorithms and proportional control. Two linear aggregate models are introduced to render large-scale simulations tractable. They accurately reproduce the groups frequency response in the three proposed control strategies. Long-term system simulations are then run to assess the groups response performance.

Stochastic programming for valuing energy storage providing primary frequency control

This paper introduces a novel modelling of the economics of energy storages providing frequency containment reserves. The focus lies both on the practical operation of day-ahead markets and the stochastic and autocorrelation characteristics of the grid frequency as they are practical concerns for any energy storage operator. Based on yearly series of grid-frequency measurements we put in light seasonal trends in the grid frequency. After having removed these trends we build an ARMA-GARCH model with fat-tail feature to explain the remaining autocorrelation. The overall model can be used to generate scenarios of 15-minute time-step frequency deviations and we explain how these scenarios can be used along with stochastic programming to dispatch and compute the revenues of a storage providing frequency containment reserves. By considering two different cases, battery storage and variable-speed pumped-storage, the paper emphasizes the importance of the technical characteristics of energy storages providing frequency containment reserves.

A dynamic programming approach to multi-period planning of isolated microgrids

An original methodology is presented to perform multi-period planning of isolated microgrids in a green field context. The aim is to build an isolated radial network to supply power to a set of initially unconnected loads whose consumption is growing through the planning horizon. The planning tool’s outputs are: (1) network routing, (2) network sizing and (3) investments timing. These 3 steps are undertaken so that they minimize the total Net Present Value of the whole system. In this paper, the emphasis is put on the structure of the distribution planning problem. In particular, its optimal substructure allows to make use of a dynamic programming approach to tackle the time dimension of the optimization problem. Furthermore, several characteristics of radial networks are presented on the basis of which the main problem can be decoupled in independent subproblems. This reduces the size of the search space and consequently the computational burden. A non-linear and unbalanced tri-phase representation of the network is used to account for the effect of single-phase connected loads on the voltage profile. The effectiveness of the proposed method is illustrated through a case study.

Frequency containment reserves with large deadband

Frequency containment reserves (FCR) or formerly called primary reserves are a major component for the stability of the continental Europe power grid. Up to now, mainly gas power plants are providing FCR and their ongoing decreasing profitability in Europe has a non-negligible impact on the FCR provision cost. In this paper, the concept of FCR with large deadband is introduced and discussed. We show that frequency dynamics after a large disturbance and frequency distribution can be maintained at a satisfactory level. The introduction of FCR with large deadband could lower their procurement cost without impacting significantly the frequency quality and enable new participants, e.g. Demand-Side Management or renewable curtailment, to enter the reserve markets.

Phase-error correction by single-phase phase-locked loops based on transfer delay

A heterogeneous mix of recently installed and significant base of renewable energy resources in some countries combined with conventional power generation results in national and cross-border network instabilities. In fact, electricity from renewable energy resources is by nature intermittent and not steadily available locally and temporarily. This leads to a reduced functionality or life cycle of effected assets that shall be avoided. A decisive factor for network stability is the permanent balance between generation and load. The balance can be reached in an effective way if both energy generation and load sides are bundled to clusters on national, regional or even international levels. Examples of such clusters are virtual power plants or integrated markets. In addition, cultural differences in users’ behavior (e.g. electrical heating) or different time zones can be used to balance generation and loads if appropriately integrated. In order to fulfill this integration successfully, novel ready-tomarket distribution and transmission technologies play a crucial role as networks will be expanded and modernized towards smart grids in an intelligent, i.e., effective way to keep necessary investments under control, and to maintain public acceptance. Some examples of smart grid technologies will be outlined in the present paper/presentation, namely: HVDC technologies including a DC breaker for DC grid applications, developed by Alstom and its partners in the frame of the European FP7Program; Phase shifting and voltage control technologies, such as wide-area monitoring in possible combination with thyristor and transistor controlled dynamic VAR compensation (SVC/StatComs); and appropriate network management systems, i.e., market management systems that help manage the financial and physical flows of electricity, transmission and distribution management systems, as well as demand response management and energy market systems.Power monitoring of nuclear reactors is done by means of neutronic instruments, but its calibration is always done by thermal procedures. The reactor thermal power calibration is very important for precise neutron flux, fuel element burn up calculations, and mainly to electrical power. The burn up is linearly dependent on the reactor thermal power and its accuracy is important to the determination of the mass of burned U-235, fission products, fuel element activity, decay heat power generation and radiooxicity. Different methods for monitoring and controlling power in nuclear reactors are used.Comparative studies of different single-phase phase-locked loops (PLL) algorithms have been made. They show that the PLL based on sample delay (dPLL), presents the lowest computational load and is as robust as the three-phase synchronous reference frame PLL dqPLL by input signal amplitude and phase variations. Its weakness appears when the input signal frequency differs from its rated frequency: it depicts a steady error on the calculated signal phase-angle. After a brief review of the dqPLL which constitutes de base structure of the dPLL, the following work will present three methods that improves the phase detection accuracy of dPLL. It is shown that the modifications brought in the original structure do not influence the robustness and stability of the algorithm but reduce the phase angle offset error by input signal frequency variation. This is corroborated by tests including not only the fundamental input voltage disturbance like amplitude, phase and frequency variation but also harmonic voltage distortion.