HOW RESERVE SOLUTIONS ENSURE GRID STABILITY WITH 100 % RENEWABLE ENERGY!
RESERVE TACKLES POWER GRIDS WITH UP TO 100 % RES GENERATION The EU has set an ambitious goal of using at least 32% completely new operational methods that could be the Renewable Energy Sources (RES) in Europe by 2030. key to solving the problem of controlling grid frequency As a result, many new RES, driven by power electron- and voltage in the future. These solutions are urgent- ics, will be installed in the grid. This change afgects the ly needed given that high penetration of renewables fundamentals of grid operation and makes rethink the for short time periods is a reality even today, so new basics of grid control and automation necessary. This is solutions for grid automation and control are already the challenge which RESERVE addresses. required. RESERVE has analysed what introducing 100% RES means RESERVE focuses on these changes and on how to for the distribution and transmission grids. RESERVE manage the power electronics-driven RES components moves from the components to the system level, defjning addressing the following questions: ➤ How are we going to maintain frequency stability in future power systems? ➤ How can power electronics play a new role and actually make the grid even better than before? ➤ What is a good systems level approach for future power systems? ➤ Which role will communication infrastructures play? ➤ How should we change the grid operational logic to adapt to the new grid paradigms? The RESERVE project is developing answers to these questions. Its vision is based on the following pillars which represent the areas of activity of the project: RESERVE VISION IT AND PAN- ANCILLARY FREQUENCY VOLTAGE COMMS EUROPEAN SERVICES STABILITY STABILITY FOR FUTURE TESTING AND GRID BY DESIGN BY DESIGN GRIDS (5G) APROACH CODES The RESERVE Vision The project results are reported in the RESERVE deliver- reviewed journals. The complete list of publications and ables. RESERVE’s scientifjc results have been published all of the project deliverables are available on the project in 3 books and in over 30 scientifjc conferences, with web site ( https://www.re-serve.eu/library.html ). 14 articles having been published in international peer- 2
RESERVE GRID STABILITY SOLUTIONS FOR UP TO 100 % RES The challenges of having high RES penetration include RESERVE captured the main technical characteristics ensuring grid stability with much less rotational inertia of the solutions by defjning four exemplary scenarios. being provided by large synchronous generators, iden- They form the basis for the development of automation, tifying and implementing needed updates to harmonise control and ICT technologies performed in the project. network codes and the provision of a communication infrastructure supporting near-real-time services with In power systems with low inertia, improvements to high reliability. RESERVE has developed innovative fre- frequency control are needed to use Energy Storage quency and voltage control approaches to ensure system Systems (ESSs) and volatile solar and wind power to slow stability, supporting them with validation in large scale down the change in frequency caused by disturbances, simulations and fjeld trials and by promoting the research maintain it within the allowed range and restore it to its concepts and policies as harmonised network codes. nominal value. Frequency control scenarios with 100% RES have been developed at the high and medium volt- RESERVE investigates using 5G-enabled ICT to provide the age grid levels, one of which using hydro-electric power communications services needed to ensure system sta- to provide inertia. The scenario without hydro-electric bility by enabling near real-time control of the distributed power uses the concept of Linear Swing Dynamics (LSD) energy network. Performance characteristics of the new to provide faster control and considers DC grids. control mechanisms have been investigated through the integration of grid simulations and live 5G wireless com- One voltage control scenario uses a novel Virtual Out- munications as hardware in the loop. A pan-European put Impedance (VOI) control technique to address the multi-site simulation test-bed, which brings together the dynamic instability in distribution systems coming from best facilities in Europe, was created in order to enable the proliferation of power-electronic-based RES, ESSs and a large-scale validation of the new concepts. loads. A second voltage control scenario manages the voltage and energy fmows using power converters instead of today’s use of on-line tap changing transformers and shunt devices that inject or draw reactive power. The RESERVE strategy DEFINE NEW ENABLING UP TO NETWORK CODES BUILDING A 100 % POWER CUSTOMER CENTRIC ELECTRONIC DRIVEN GRID VERIFY IN GRID FIELD TRIALS TEST IN LARGE SIMULATIONS DEVELOP NEW THEORY VOLTAGE FREQUENCY CONTROL CONTROL 3
FREQUENCY STABILITY BY DESIGN Description & Benefjts Reducing the number of large centralised generators as under dynamic conditions and of “Rate of Change of more distributed generation is introduced at medium Frequency” (RoCoF) in the Frequency Divid er Formula and low voltage levels means that the amount of rotat- (FDF) and Linear Swing Dynamics (LSD), for which rec- ing mass drops severely, resulting in a reduced ability ommendations for new Ancillary Services and Network to provide inertial response to maintain grid stability. Code defjnitions have been drafted. RESERVE has developed novel defjnitions of “frequency” Frequency Divider Formula (FDF) Linear Swing Dynamics (LSD) approach: approach: ➤ What it is? FDF is a mathematical tool that ➤ What it is? LSD emulates conventional syn- estimates the frequency variations at every chronous generators by providing virtual bus of the network after a contingency. inertia and participating in frequency control while achieving enhanced dynamic behav- ➤ How it works: the estimation is based on a iour and linearised characteristics. linear relationship between bus frequencies and synchronous machine rotor speeds ➤ How it works: The LSD concept linearises the based on the augmented admittance matrix non-linear power-angle characteristic by tai- of the system. loring voltage control, exploiting the permit - ted voltage tolerance in power systems. ➤ What it is for? the applications of the FDF and its variations include monitoring, ➤ What it is for? RES-tied power converters, dynamic state estimation, frequency control, namely Virtual Synchronous Generators, advanced models of power system devices, emulate the classical synchronous generator. identifjcation of critical parts of the system ➤ Benefjts: LSD exploits the degrees of free - that need to be measured, etc. dom introduced by power electronics. ➤ Benefjts: FDF gives an accurate and complete It incorporates the advantages of the syn- picture of the behavior of the frequency in chronous generator while overcoming its systems with low-inertia. drawbacks (i.e. non-linearities) by achieving a linear dynamic behaviour ofgering high - ly-predictable dynamics, enhanced system stability and simplifjed stability analysis of future power systems. 4
VOLTAGE STABILITY BY DESIGN Description High penetration of RES can cause short time-frame AVM works by extracting the local load profjle, which is dynamic instabilities and large time-frame steady state used to determine the inverter set-points to ensure that voltage unbalances and over or under voltage. These the power losses and voltage unbalances are minimised. key issues are-addressed by the concepts of Dynamic Voltage Stability Monitoring (DVSM) and Active Voltage Benefjts Mangemant (AVM). The proposed techniques contribute to grid stability, ena- Using DVSM, the local grid impedances are calculated bling a smooth transition from conventional distribution at the distributed generators. To do this, small signal grids to future power electronics driven grids. perturbations are injected locally and used to measure the grid impedance. The measured grid impedance is used to synthesise a virtual inverter output impedance which stabilises the inverter. RESERVE PROGRAMMABLE INVERTER The RESERVE Low Power Inverter Prototype Description Benefjts The programmable inverter prototype, developed by the RESERVE project, accurately measures the grid imped- Grid operators can use this device to measure grid im- ance from the point of interconnection with the grid. Its pedances at nodes in the grid, enabling grid stability to low-cost gives it a signifjcant advantage over currently be monitored in real-time. It can be included in existing available inverters on the market. It is used in the RE- residential photo-voltaic inverters as a software com- SERVE voltage control fjeld trials on the ESBN network in ponent. It can also be used to enable ancillary services, Ireland and in laboratory tests in the RWTH laboratory in such as impedance measurement and local harmonic Germany. Discussions regarding the commercialisation stability monitoring, to be ofgered to the grid operator. of the inverter are ongoing. 5
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