Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
  • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
  • H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
  • H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
  • H02J7/0025—Sequential battery discharge in systems with a plurality of batteries
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
  • H02J7/0047—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with monitoring or indicating devices or circuits
  • H02J7/005—Detection of state of health [SOH]
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
  • H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
  • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
  • Y02B70/30—Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
  • Y02B70/3225—Demand response systems, e.g. load shedding, peak shaving
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
  • Y02E40/10—Flexible AC transmission systems [FACTS]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/60—Other road transportation technologies with climate change mitigation effect
  • Y02T10/70—Energy storage systems for electromobility, e.g. batteries
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
  • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
  • Y04S20/00—Management or operation of end-user stationary applications or the last stages of power distribution; Controlling, monitoring or operating thereof
  • Y04S20/20—End-user application control systems
  • Y04S20/222—Demand response systems, e.g. load shedding, peak shaving

Definitions

• the present invention generally relates to the field of energy storage systems for electrical energy. In particular to the field of battery-based energy storage systems.
• a common practice for providing primary balancing power is the use of gas-fired power plants which can ramp the produced power up and down relatively quickly. However, often this requires operation under non-ideal conditions which decreases efficiency and profitability.
• EP 2777120 B1 discloses a method for delivering balancing power to stabilize an AC electricity network, the AC electricity network operating at a set frequency, comprising an energy storage that can take up and deliver electrical energy.
• battery-based energy storage systems are also used for performing other tasks, such as reactive power compensation, uninterruptible power supply and/or peak-shaving, i.e. the reduction of the peak demand of an electricity consumer.
• a battery-based energy storage system is often used to provide several functions in order to profitably operate the system.
• the present technology relates to a battery unit configured to store and release electrical energy and/or power.
• the battery unit comprises a first set of rechargeable battery modules and a second set of rechargeable battery modules, wherein each set of rechargeable battery modules comprises at least one rechargeable battery module, wherein each battery module comprises at least one battery cell.
• the battery unit comprises at least one battery management system (BMS) for each set of rechargeable battery modules, configured to monitor, control and/or protect the rechargeable battery modules during operation.
• BMS battery management system
• at least 70% of charging and discharging processes of the battery unit during a 24 h period are performed utilizing only the first set of rechargeable battery modules. That is, during a time period of 24 hours primarily the first set of rechargeable battery modules is used.
• a battery cell typically is an electrochemical cell that can produce electrical energy from a chemical reaction as long as the chemicals required for the reaction are present. Once, the chemicals are no longer present in sufficient quantity a battery is considered empty.
• rechargeable batteries can reverse the chemical reaction by applying an electric current to the battery cell and thus recharge the battery cell.
• Rechargeable batteries may also be referred to as secondary batteries.
• rechargeable battery modules comprise rechargeable battery cells, i.e. the battery cells comprised by rechargeable battery modules can reverse the corresponding underlying chemical reaction if an electric current is applied.
• the underlying chemical reaction can be different for different types of battery cells.
• these battery cells may be connected in series, in parallel or any combination thereof.
• the battery modules of a set of battery modules may be connected in series, in parallel or any combination thereof.
• At most 95% of charging and discharging processes of the battery unit during a 24 h period may be performed utilizing only the first set of rechargeable battery modules.
• Each battery cell may comprise a state of health (SOH) that is configured to indicate the battery cells capacity with respect to its designed capacity.
• SOH state of health
• the SOH may be estimated or determined, which is indicative of the battery cells condition with respect to the designed battery cell properties, specifically regarding the capacity.
• the SOH may for example be a parameter that can be used to determine an aging of a battery cell, or in other words a decline in performance. This may for example be advantageous for estimating a remaining lifetime for the battery cell.
• first and second set of rechargeable battery modules can comprise identical battery modules, whereas in other embodiments the first and second set of rechargeable battery modules can comprise distinct battery modules. That is, in some embodiments the battery modules of the first set may be distinct from the battery modules of the second set.
• the at least one battery cell of the first set of rechargeable battery modules may be based on a battery cell type that is different to the battery cell type of the at least one battery cell of the second set of rechargeable battery modules. That is the battery cell may for example comprise different chemicals.
• the first and second set of rechargeable battery modules can comprise a different C-rate.
• the C-rate denotes the rate at which a battery is charged or discharged relative to its maximum capacity. That is, a C-rate of 1 C means that a discharge current will discharge the entire battery in 1 hour.
• a battery with 200 Ah and a C-rate of 1 C comprises a discharging (and charging) current of 200 A, wherein a C-rate of 0.5 C corresponds to a discharging (and charging) current of 100 A.
• the first and second set of rechargeable battery modules can comprise a different capacity.
• the battery modules of the first and second set may be distinct in that the at least one battery cell of the first set of rechargeable battery modules can have a different SOH than the at least one battery cell of the second set of rechargeable battery modules.
• the difference in SOH between the at least one battery cell of the first set of rechargeable battery modules and the second set of rechargeable battery modules may be at least 2%, preferably at least 5%, more preferably at least 10%.
• the SOH may correspond to the lowest SOH of the comprised battery cells. That is, the SOH of the battery module may be determined by the weakest SOH of the comprised battery cells. Similarly, the SOH of a set of battery modules may be determined by the SOH of the weakest battery module.
• the first set of rechargeable batteries can be a set of new batteries, i.e. comprising a SOH of at least 98%
• the second set of rechargeable batteries can be a set of second-use batteries, i.e. batteries that have been used in another application prior to the use in the battery unit.
• the battery unit may comprise a first set of rechargeable battery modules comprising new battery modules and a second set of rechargeable battery modules comprising second-use batteries. That is, batteries that have been used before, preferably in a different application than a stationary energy storage unit, such as battery modules of an electric car.
• the second-use batteries may comprise a SOH of at most 95%, preferably at most 90%, more preferably at most 85%, even more preferably at most 80%.
• the BMS can comprise a deep discharge protection configured to protect the battery cells from deep discharge, i.e. too low voltages. This may be advantageous as deep discharge may cause an irreversible reduction of the capacity of a battery cell. Further, the BMS can comprise an overcharge protection configured to protect the battery cells from over charging, i.e. too high voltages. Similarly, overcharging may be detrimental to a battery cells lifetime. Further, deep discharge protection as well as overcharge protection may both also be relevant to the security of the battery unit.
• the BMS can also comprise a charge state detector, configured to detect or estimate the state of charge (SOC) of the battery cells.
• SOC state of charge
• the state of charge of a battery cell generally denotes the currently available capacity with respect to the overall (rated) capacity of the battery cell and is typically given in percentage. That is, the SOC is a measure of the currently stored electrical energy relative to the maximum energy that can be stored in the battery cell. In simple terms the SOC may be comparable to a fuel gauge in a car showing the level of fuel left in the tank.
• the BMS can also comprise a passive or active balancer configured to balance the SOC of the individual battery cells. That is, match the SOC of the individual battery cells to eliminate differences in capacity.
• a balancer may substantially equalize the SOC of battery cells in a battery module and/or a set of battery modules. This may be advantageous as battery cells typically comprise differences in the maximum available capacity, for example due to uncertainties in manufacturing and/or different rates of aging. Overall, balancing the SOC may improve the available capacity and can also improve the lifetime of battery cells.
• the BMS can further comprise a voltage monitor configured to monitor the voltage of the individual battery cells, the minimum cell voltage and/or the maximum cell voltage.
• the BMS can comprise a state of health detection, configured to determine the SOH of the battery cells and/or of the battery modules.
• Said state of health detection may comprise an algorithm for determining the current SOH based on a number of SOH parameters and their historic development. That is the BMS may comprise a state of health detection which may utilize an algorithm to calculate the SOH of the battery cells and/or battery modules based on a number of parameters and their historical development.
• Said SOH parameters may for example be development of the (overall) capacity over time, internal resistance or heating under load.
• the BMS can also comprise a temperature monitor configured to monitor the average cell temperature, coolant intake temperature, coolant output temperature and/or temperature of individual cells.
• the BMS can be configured to provide additional parameters on the battery cells such as residual capacity, internal resistance and/or leakage current of individual cells. That is, during operation additional parameters may be required or beneficial and thus the BMS may be configured to provide such additional information.
• Each BMS can comprise a Master-BMS and at least one sub-BMS, wherein each sub-BMS comprises a bus to the Master-BMS, which is configured to exchange data between the Master BMS and the sub-BMS.
• each battery module comprises a sub-BMS, configured to provide data on each battery cell of the battery module.
• the first or second set of battery modules may comprise a BMS comprising a Master-BMS and additionally a sub-BMS for each battery module of the corresponding set of modules.
• each sub-BMS may monitor, control and/or protect the battery cells comprised by the battery module and the Master-BMS may exchange data with each of the sub-BMS, thus providing functionality for the set of battery modules.
• the first and/or second set of the battery unit each comprise rechargeable battery modules with different battery cell types. That is, the battery cells may for example rely on different chemical reactions to provide electrical energy.
• the battery cells can be based on a battery cell type that is at least one of a lead-acid cell, a lithium-ion cell, a nickel-cadmium cell, a nickel metal hydride cell, a zinc-air cell and a redox flow cell.
• the Lithium-ion cell can be one of a lithium-sulphur cell, a lithium- nickel-manganese-cobalt-oxide cell, a lithium-iron-phosphate, a lithium-nickel-cobalt- aluminium-oxide cell, a lithium-titanate cell and a lithium-air cell.
• the present invention relates to an energy storage system, which is configured to store and provide electrical energy and/or power and wherein the system comprises a battery unit according to the present technology.
• the system can further comprise a power electronics unit, configured to control and/or convert electric power.
• the power electronics unit can comprise an inverter, configured to convert direct current (DC) to alternating current (AC) and additionally or alternatively, it can also comprise a rectifier, configured to convert alternating current (AC) to direct current (DC).
• rectifier and inverter are combined in a single device, i.e. a single device may provide bidirectional conversion of AC and DC.
• the power electronics unit can comprise a plurality of inverters, rectifiers and or single devices configured for the bidirectional conversion of AC and DC. That is, the power electronics unit may for example comprise one rectifier and inverter for each set of modules or even each battery cell, respectively.
• the system can further comprise an energy management system (EMS), configured to control the operation of the energy storage system. That is, the EMS may monitor, control, and/or optimize the performance of the energy storage system. In some embodiments, the EMS may be configured to control all energy flows within the system.
• EMS energy management system
• the EMS can further comprise an external interface.
• An external interface may generally provide a connection to a device outside of the energy storage system, e.g. an Ethernet, FireWire or USB connection or a serial or parallel port. It will be appreciated that an external interface may also be established via wireless connection such as a local WLAN connection.
• the EMS can be configured to control the power electronics unit. That is, during operation the EMS may for example control the inverter and the rectifier required for conversion of AC and DC.
• the EMS can be configured to send and receive data from at least one BMS. That is, the EMS may communicate with at least one BMS, preferably with each BMS. In embodiments where the BMS comprises a Master-BMS the EMS may preferably send and receive data from the Master-BMS, which may in turn exchange data with the corresponding one or more sub-BMS via a bus.
• the system can further comprise at least one air-conditioning (AC) unit, which is configured to control the temperature for at least a portion of the system. That is, the AC unit may for example only control the temperature of components that benefit from a constant temperature, such as for example the battery unit, whereas other components may just be ventilated, e.g. the power electronics unit.
• the at least one air-conditioning unit may further be configured to control the humidity for at least a portion of the system.
• the at least one air-conditioning unit may comprise an active temperature control. That is, the temperature may be actively controlled for example through a feedback loop based on a temperature measurement of a component comprised by the portion of the system for which the temperature is controlled.
• the system can comprise at least one transformer, such as a medium-voltage transformer.
• a transformer may typically be configured for voltage conversion of an AC voltage, i.e. a transformer may receive an AC input voltage and provide an AC output voltage, wherein generally the AC output voltage can be higher, lower or in some cases equal to the AC input voltage.
• the energy storage system may comprise a nominal power in the range of 1 MW to 500 MW, preferably 2 MW to 200 MW, even more preferably 5 to 100 MW, even more preferably 10 to 50 MW. Additionally or alternatively, the energy storage system may comprise a capacity in the range of lMWh to 500MWh, preferably 2 MWh to 200 MWh, such as 50 MWh. Further, the energy storage system may comprise a C-rate in the range of 0.1C to IOC, preferably 0.5C to 5C, more preferably 1C to 5C.
• the energy storage system can be configured for providing balancing power for stabilizing a power network to a pre-defined frequency. That is, the energy storage system may provide or store electrical energy depending on the current supply and demand of a power network. Typically, supply and demand can be determined through the frequency deviations of the grid frequency from the designated value.
• the energy storage system can be configured for peak shaving, i.e. reducing the peak load of an electricity consumer. That is, peak loads may be reduced through supplying part of the power by the energy storage system, which may be beneficial for stability of a power network and/or may save costs for the electricity consumer.
• the peak load may be reduced by at least 2%, preferably at least 4%, more preferably at least 5%. In some cases, the peak load may even be reduced by 50% and more, such as 80%, e.g. in the case of fast chargers for electrical vehicles.
• the energy storage system may be configured to provide emergency power such as an uninterruptible power supply (UPS), e.g. in case of a power outage.
• UPS uninterruptible power supply
• the energy storage system may also be configured for stand-alone operation, i.e. it may be configured to function without a power network.
• the system may be at least part of a stand-alone power system, sometimes also known as remote area power supply.
• the energy storage system may be configured for an atypical network use, i.e. shifting the peak load out of the peak time window. That is, the power consumption may be optimized such that the specific annual maximum load does not coincide with the maximum load of the system operator. This may be advantageous for the stability of the power network and/or may save costs for the electricity consumer.
• the energy storage system may also be configured to provide reactive power compensation.
• Reactive power typically exists in AC circuits or networks when voltage and current are out of phase and no actual work is done, i.e. reactive power moves back and forth between the power source and reactive loads without contributing to the active power that can be consumed by electrical resistance, motor or other devices.
• the power supplied to the network i.e. apparent power, comprises contributions from both active and reactive power, therefore reactive power compensation may be advantageous as it may decrease the overall current and a lower current also reduces the load on the grids and thus their (ohmic) power losses.
• an inverter of the energy storage system that is not already 100% loaded with active power can generate reactive power for the grid or, in other words, compensate the reactive power in the grid.
• the energy storage system can be configured for self-consumption optimization. That is, for example a household or commercial enterprise owning an electrical generator (generation plant) may expand the use of self-generated energy further through the use of the energy storage systems.
• the energy storage system can be configured to provide a black-start source. That is, the energy storage system may be configured to start up independently after a power grid interruption without requiring auxiliary power to start the controls. This may be advantageous in cases where a power network has failed in a wide area and cannot be started without an independent energy supply.
• the energy storage system can comprise an electrical generator. That is, the energy storage system may itself generate electrical energy by means of an electrical generator which may also be referred to as generation plant.
• an electrical generator may for example be a gas turbine, a photovoltaic system, a fuel cell, a wind turbine, a diesel generator, a combined heat and power unit, and/or a pumped-storage hydropower or a run-of-river power station.
• the electrical generator may either be an AC electrical generator, such as a gas turbine, a wind turbine or a combined heat and power unit, or it may be a DC electrical generator, e.g., a photovoltaic system or a fuel cell.
• the energy storage system may comprise an electricity consumer, for example, an electrolysis unit or an arc furnace in steel works. That is, the energy storage system may consume electrical energy, which may for example be beneficial for providing balancing power and/or achieving a uniform power consumption.
• the energy storage system can also be configured for active storage of battery cells or modules. That is, the second set may for example comprise new battery modules that require storage before their intended use. Actively storing these batteries may for example include gentle loading and unloading while keeping the SOC relatively close to an optimum of 50%, which may prevent deep-discharge of the battery cells and improve the SOH in comparison to a passive storage.
• the energy storage system may be configured as a stationary energy storage system, i.e. the energy storage system may not be configured to be moved during operation.
• the second set of rechargeable batteries of the battery unit may provide at least 20% of the capacity, preferably at least 50% of the capacity, more preferably at least 70% of the capacity such as 80% of the capacity. Similarly, the second set of rechargeable batteries of the battery unit may provide at most 95% of the capacity, preferably at most 90% of the capacity, such as 80% of the capacity.
• the present technology relates to a method comprising an energy storage system according to any of the preceding system embodiments, wherein the method comprises storing and releasing electrical energy and/or power from the battery unit of the energy storage system.
• the step of storing electrical energy and/or power can comprise converting AC to DC by means of the power electronics unit, whereas the step of releasing electrical energy and/or power can comprise converting DC to AC by means of the power electronics unit.
• the method can comprise at least one of the following steps of receiving a request for storing or providing electrical energy and/or power and determining need for storing or providing electrical energy and/or power.
• the method can also comprise receiving a set of input parameters, wherein the set of input parameters may comprise at least one of an amount of electrical energy to be stored or released, an amount of electrical power to be stored or released, current SOC of at least the first set of batteries or the second set of batteries, a designated system lifetime, a minimal state of health (SOH mm ), an estimate of at least one SOH of at least a portion of the system, e.g. a set of batteries, a measurement of at least one SOH of at least a portion of the system, e.g.
• An operation mode may for example be power balancing or peak shaving.
• the process of storing and releasing electrical energy may also be understood as storing and releasing electrical power.
• power is energy per unit of time and that in the context of a power network both electrical energy and electrical power may be relevant.
• storing and releasing power may primarily be relevant, whereas self-consumption optimization is generally concerned with storing and releasing energy.
• the method can comprise optimizing the distribution of provided and/or stored electrical energy and/or power between the first and second set of battery modules.
• the provided power may for example be the provided balancing power, depending on the application of energy storage system.
• the step of optimizing the distribution of provided and/or stored electrical energy and/or power between the first and second set of battery modules can comprise at least one of achieving substantially identical states of health (SOHs) for the first and second set of battery modules at a designated system lifetime and/or an economic lifetime of the system, sparing the second set of battery modules and optimizing the distribution according to at least a subset of input parameters.
• SOHs states of health
• the first set of battery modules may comprise battery cells with 95% efficiency, whereas the battery cells comprised by the second set of battery modules may only comprise an efficiency of 90%. Therefore, by primarily utilizing the first set of battery modules the average statistical efficiency of the overall system may be optimized and losses may be limited.
• the method can comprise estimating a prediction for a future development of the state of health (SOH) of the first and/or second set of battery modules, based on a set of prediction data.
• SOH state of health
• the future development of the SOH may only comprise a single value of the SOH at a future time.
• the set of prediction data may comprise at least one, or a plurality of the current SOH of the set of battery modules, historical development of the SOH of the set of battery modules, historical utilization of the set of battery modules and predicted utilization of the set of battery modules.
• the provided and/or stored electrical energy and/or power may be distributed between the two sets of battery modules based on at least one of the current SOH of at least one set of battery modules and the predicted future development of the SOH of at least one set of battery modules.
• At least one input parameter of the set of input parameters can be changed during operation. That is, an input parameter may for example be updated during the operation of the energy storage system according to the method of the present technology.
• the method may comprise receiving a set of input parameters and updating, i.e. changing during operation, at least one input parameter. That is, the method may comprise receiving a new value for an input parameter.
• the method can comprise providing primary balancing power for stabilisation of a power network to a predefined frequency. Further, providing primary balancing power may comprise storing and releasing electrical energy and/or power from the battery unit depending on the frequency deviation from the desired value, i.e. the deviation of the frequency from the predefined frequency.
• the frequency deviation from the desired value can be measured by the energy storage system. Additionally or alternatively may the frequency deviation from the desired value be provided at the external interface by an external source.
• the step of optimizing the distribution of the provided and/or stored electrical energy and/or power can comprise monitoring of the volume of the provided balancing power. For example, to determine if both sets of battery modules are utilized or if only the first set may provide the balancing power. Additionally or alternatively may the step of optimizing the distribution of the provided and/or stored electrical energy and/or power comprise monitoring the gradient of the provided balancing power at the beginning of a stabilisation action. That is, the gradient may for example enable to provide an estimate of the overall energy required for the balancing and thus may serve to indicate if only one set may be utilized or if both sets may be required to provide the estimated required energy for the balancing action, e.g. to fulfil a request for balancing power.
• the step of optimizing the distribution may comprise keeping the SOC of the second set of rechargeable batteries in the range of 40% to 60%, preferably 45% to 55%, such as 50% for at least 70% of the operation time of the energy storage system.
• the method can comprise protecting the battery cells from deep discharge.
• the method can comprise protecting the battery cells from over charging.
• the method can comprise detecting and/or monitoring the SOC of the battery cells.
• the method can comprise balancing the SOC of the battery cells within a battery module and/or a set of battery modules.
• the method can comprise monitoring the voltage of the individual battery cells, the minimum cell voltage and/or the maximum cell voltage.
• the method can comprise determining the SOH of the battery cells, e.g. by monitoring the capacity of the battery cells and identifying changes thereof.
• the method can comprise monitoring the average cell temperature, coolant intake temperature, coolant output temperature and/or temperature of individual cells.
• the method may comprise determining additional parameters of the battery cells, e.g. residual capacity, internal resistance and/or leakage current.
• the method can also comprise providing energy storage capacity for load balancing.
• load balancing may generally refer to adjusting the load distribution in a power network with respect to time.
• load balancing may comprise storing excess electrical power (or energy) in periods of low demand and releasing electrical power (or energy) in periods of high demand.
• the method may comprise controlling the temperature of the battery unit. Further, the method can comprise actively stabilising the temperature at least of the first set of rechargeable battery modules.
• the method may comprise reducing the peak load of an electricity consumer. That is, the system may be utilized for peak shaving.
• the method may comprise providing emergency power. That is, for example utilizing the system as an uninterruptible power supply (UPS).
• UPS uninterruptible power supply
• the method may comprise operating the system without a connection to a power network. That is, the system may be utilized in a stand-alone fashion. In other words, the system may be at least part of a stand-alone power system, sometimes also known as remote area power supply.
• the method comprises shifting the peak load out of a peak time window. That is, the system may be utilized for an atypical network use.
• the method may comprise providing reactive power compensation.
• the method may comprise optimizing self-consumption.
• the method may comprise providing a black-start source.
• the method may comprise actively storing battery cells or modules.
• the present invention also relates to the use of the battery unit and the energy storage system according to the present technology described above in a method according to the present invention.
• the present invention is also defined by the following numbered embodiments.
• battery unit embodiments These embodiments are abbreviated by the letter “B” followed by a number. Whenever reference is herein made to “battery unit embodiments”, these embodiments are meant.
• a battery unit configured to store and release electrical energy, the battery unit comprising, a first set of rechargeable battery modules, comprising at least one rechargeable battery module; a second set of rechargeable battery modules, comprising at least one rechargeable battery module;
• BMS battery management system
• each battery module comprises at least one battery cell
• each battery cell comprises a state of health (SOH), configured to indicate the battery cells capacity with respect to its designed capacity.
• SOH state of health
• BIO The battery unit according to the preceding embodiment, wherein the difference in SOH between the at least one battery cell of the first set of rechargeable battery modules and the second set of rechargeable battery modules is at least 2%, preferably at least 5 %, more preferably at least 10%.
• Bl l The battery unit according to any of the 2 preceding embodiments, wherein the first set of rechargeable batteries is a set of new batteries, i.e. comprising a SOH of at least 98%; and
• the second set of rechargeable batteries is a set of second-use batteries, i.e. batteries that have been used in another application prior to the use in the battery unit.
• B13 The battery unit according to any of the preceding embodiments, wherein the BMS comprises a deep discharge protection, configured to protect the battery cells from deep discharge, i.e. too low voltages.
• B14 The battery unit according to any of the preceding embodiments, wherein the BMS comprises an overcharge protection, configured to protect the battery cells from over charging, i.e. too high voltages.
• B15 The battery unit according to any of the preceding embodiments, wherein the BMS comprises a charge state detector, configured to detect or estimate the state of charge (SOC) of the battery cells.
• SOC state of charge
• B16 The battery unit according to any of the preceding embodiments, wherein the BMS comprises a passive or active balancer configured to balance the SOC of the individual battery cells.
• B17 The battery unit according to any of the preceding embodiments, wherein the BMS comprises a voltage monitor, configured to monitor the voltage of the individual battery cells, the minimum cell voltage and/or the maximum cell voltage.
• the BMS comprises a voltage monitor, configured to monitor the voltage of the individual battery cells, the minimum cell voltage and/or the maximum cell voltage.
• B18 The battery unit according to any of the preceding embodiments with the features of B4, wherein the BMS comprises a state of health detection, configured to determine the SOH of the battery cells and/or the battery modules.
• the state of health detection comprises an algorithm for determining the current SOH based on a number of SOH parameters and their historic development.
• B20 The battery unit according to any of the preceding embodiments, wherein the BMS comprises a temperature monitor, configured to monitor the average cell temperature, coolant intake temperature, coolant output temperature and/or temperature of individual cells.
• B21 The battery unit according to any of the preceding embodiments, wherein the BMS is configured to provide additional parameters on the battery cells such as residual capacity, internal resistance and/or leakage current of individual cells.
• each BMS comprises a Master-BMS and at least one sub-BMS
• each sub-BMS comprises a bus to the Master-BMS, configured to exchange data between the Master BMS and the sub- BMS.
• each battery module comprises a sub-BMS, configured to provide data on each battery cell of the battery module.
• system embodiments These embodiments are abbreviated by the letter “S” followed by a number. Whenever reference is herein made to “system embodiments”, these embodiments are meant.
• An energy storage system configured to store and provide electrical energy and/or power, the system comprising a battery unit according to any preceding battery unit embodiments.
• the system comprises a power electronics unit, configured to control and/or convert electric power.
• the power electronics unit comprises an inverter, configured to convert direct current (DC) to alternating current (AC).
• the power electronics unit comprises a rectifier, configured to convert alternating current (AC) to direct current (DC).
• the power electronics unit comprises a plurality of inverters, rectifiers and or single devices configured for the bidirectional conversion of AC and DC.
• EMS energy management system
• system further comprises at least one air-conditioning (AC) unit, configured to control the temperature for at least a portion of the system.
• AC air-conditioning
• the at least one air-conditioning unit comprises an active temperature control.
• the system further comprises at least one transformer, such as a medium-voltage transformer.
• the energy storage system comprises a nominal power in the range of 1 MW to 500 MW, preferably 2 MW to 200 MW, even more preferably 5 to 100 MW, even more preferably 10 to 50 MW.
• the energy storage system comprises a capacity in the range of 1 MWh to 500 MWh, preferably 2 MWh to 200 MWh, such as 50 MWh.
• energy storage system comprises a C-rate in the range of 0.1C to IOC, preferably 0.5C to 5C, more preferably 1C to 5C.
• the energy storage system is configured to provide emergency power such as an uninterruptible power supply (UPS), e.g. in case of a power outage.
• UPS uninterruptible power supply
• B28 The battery unit according to any of the preceding battery unit embodiments, wherein the second set of rechargeable batteries provides at most 95% of the capacity, preferably at most 90% of the capacity, such as 80% of the capacity.
• a method comprising an energy storage system according to any of the preceding system embodiments, wherein the method comprises storing and releasing electrical energy and/or power from the battery unit of the energy storage system.
• a measurement of at least one SOH of at least a portion of the system e.g. a set of batteries; a characteristic of at least one of the battery cells, e.g. efficiency or energy density; a pre-set distribution of the provided and/or stored electrical energy between the first and second set of modules;
• an operation mode i.e. which task the system primarily performs.
• step of optimizing the distribution of provided and/or stored electrical energy and/or power between the first and second set of battery modules comprises at least one of
• SOHs states of health
• the method comprises estimating a prediction for a future development of the state of health (SOH) of the first and/or second set of battery modules, based on a set of prediction data.
• the set of prediction data comprises at least one, or a plurality of
• Mi l The method according to any of the preceding method embodiments with the features of M5, wherein at least one input parameter of the set of input parameters is changed during operation.
• providing primary balancing power comprises storing and releasing electrical energy and/or power from the battery unit depending on the frequency deviation from the desired value, i.e. the deviation of the frequency from the predefined frequency.
• step of optimizing the distribution of the provided and/or stored electrical energy and/or power comprises monitoring of the volume of the provided balancing power.
• step of optimizing the distribution of the provided and/or stored electrical energy and/or power comprises monitoring the gradient of the provided balancing power at the beginning of a stabilisation action.
• optimizing the distribution comprises keeping the SOC of the second set of rechargeable batteries in the range of 40% to 60%, preferably 45% to 55%, such as 50% for at least 70% of the operation time of the energy storage system.
• the battery unit comprises the features of B16, wherein the method comprises detecting and/or monitoring the SOC of the battery cells.
• the battery unit comprises the features of B17, wherein the method comprises balancing the SOC of the battery cells within a battery module and/or a set of battery modules.
• the battery unit comprises the features of B18, wherein the method comprises monitoring the voltage of the individual battery cells, the minimum cell voltage and/or the maximum cell voltage.
• the battery unit comprises the features of B19, wherein the method comprises determining the SOH of the battery cells, e.g. by monitoring the capacity of the battery cells and identifying changes thereof.
• the battery unit comprises the features of B20, wherein the method comprises monitoring the average cell temperature, coolant intake temperature, coolant output temperature and/or temperature of individual cells.
• the battery unit comprises the features of B21, wherein the method comprises determining additional parameters of the battery cells, e.g. residual capacity, internal resistance and/or leakage current.
• M27 The method according to any of the preceding method embodiments, wherein the method comprises providing energy storage capacity for load balancing.
• M28 The method according to any of the preceding method embodiments, wherein the energy storage system comprises the features of S12, wherein the method comprises controlling the temperature of the battery unit.
• Fig. 1A depicts a battery unit according to a general embodiment
• Fig. IB depicts a battery module according to an embodiment of the present invention
• Fig. 2 depicts an embodiment of an energy storage system
• Fig. 3 depicts a method according to the present invention
• Fig. 4 depicts an exemplary time evolution of the state of health of a first and second set of rechargeable battery modules
• Fig. 5 schematically depicts a method embodiment of the present invention
• Fig. 6 depicts a standardized characteristic curve of the balancing power output as a function of the frequency deviation
• Fig. 7 shows exemplary data of the frequency distribution of the grid frequency in the synchronous grid of Continental Europe.
• the invention relates to a battery unit 1.
• the battery unit 1 comprises a first set of rechargeable battery modules 11 and a second set of rechargeable battery modules 12, wherein each set comprises at least one rechargeable battery module.
• the first set of rechargeable battery modules 11 may also be referred to as the first set of battery modules 11, the first set of modules 11 or simply the first set 11.
• the second set of rechargeable battery modules 12 may also be referred to as the second set of battery modules 12, the second set of modules 12 or simply the second set 12.
• the battery unit 1 comprises a battery management system (BMS) 13, 14 for each set of rechargeable battery modules 11,12 that is configured to monitor, control and/or protect the rechargeable battery modules and the comprised battery cells during operation.
• BMS battery management system
• a rechargeable battery module 111, 121 or simply battery module 111, 121 is depicted in Fig. IB.
• Each battery module 111, 121 comprise at least one battery cell 1111, 1211. That is a battery module 111, 121 may comprise one or more battery cells 1111, 1211.
• Each battery cell 1111, 1211 comprised by the battery unit 1 may comprise a state of health (SOH), which indicates the battery cells capacity with respect to its designed capacity.
• SOH state of health
• the SOH may be estimated or determined, wherein the SOH may be indicative of the batteries condition relative to its designed properties.
• the SOH may simply be given by the current capacity C c relative to the designed capacity C d . That is,
• the SOH may also be quoted as percentage, that is a SOH of 0.9 may be referred to as a SOH of 90%.
• a SOH of 1 (or accordingly 100%) corresponds to a battery cell 1111, 1211 that comprises a capacity identical to the designed capacity. This may typically be the case for a new battery cell 1111, 1211 that is produced according to the designed specifications.
• the SOH may also be determined for a battery module 111, 121, the first set of modules 11, the second set of modules 12 and/or the whole battery unit 1.
• the first set 11 of the battery unit 1 may be primarily utilized for providing and/or storing the electrical energy during operation of the battery unit 1. That is, the first set 11 may be utilized for at least 70% of the charging and discharging processes of the battery unit during a 24 h period.
• the present invention also relates to an energy storage system 2 that is configured to store and/or provide electrical energy and/or power.
• the energy storage system 2 may comprise a battery unit 1 according to the present invention for storing and providing electrical energy.
• the energy storage system 2 may also be referred to as storage system 2 or simply system 2.
• the energy storage system 2 typically comprises a power electronics unit 21 that may be configured to control and/or convert electric power.
• the power electronics unit 21 typically comprises an inverter, also known as power inverter, configured to convert a direct current (DC) into an alternating current (AC). That is, the inverter may convert a direct current typically supplied by the battery unit 1 to an alternating current that may for example be fed into a power network.
• the power network may also be referred to as mains, power grid or simply network.
• the power electronics unit 21 may further comprise a rectifier that is configured to convert AC to DC, therefore for example enabling to store electrical energy from a power network in the battery unit 1 of the system 2.
• inverter and rectifier may combined in a single device.
• the power electronics unit 21 may comprise a device that can provide a bidirectional conversion of AC and DC, i.e., conversion from AC to DC and vice versa.
• the power electronics unit 21 may further comprise a plurality of rectifiers and/or converters or devices that provide a bidirectional conversion.
• each set of rechargeable battery modules 11, 12 of the battery unit may be connected to separate components of the power electronics unit 21.
• the system may further comprise an energy management system (EMS) 22, configured to control the operation of the energy storage system 2. That is, the EMS 22 may monitor, control and optimize the operation of the system 2 and control all energy flows therein.
• the EMS may be configured to control the power electronics unit 21 and communicate with the BMS 13, 14, i.e. send and receive data from the BMS 13, 14.
• the EMS 22 may provide an external interface to receive instructions and/or parameters relating to the operation of the energy storage system 2.
• the EMS may receive data on the current frequency of the power network or peak loads or receive instructions from a user of the system 2.
• the energy storage system 2 may comprise an air-conditioning (AC) unit 23 for temperature control of at least a portion of the system.
• AC air-conditioning
• the power electronics unit 21 and at least a portion of the battery unit 1 may require cooling.
• the AC unit 23 may further comprise active temperature control. This may be particularly useful for at least a portion of the battery unit 1 as some battery cells 1111, 1211 may require operation in a specified temperature range and/or benefit from operation within a certain temperature window.
• the energy storage system 2 can be configured for a plurality of different applications.
• the system 2 may provide balancing power to stabilize a power network to a pre-defined grid frequency, e.g. 50 Hz. That is, depending on a frequency deviation the system may store or release electrical energy and/or power to stabilize the power network.
• a higher frequency i.e. higher than the pre-defined frequency, indicates an excess of electrical energy in the network and thus the system 2 may store electrical energy in order to correct for the surplus of electrical energy, whereas a lower frequency indicates a shortage of electrical energy and/or power in the network and thus the system 2 may release electrical energy to correct for the lack of electrical energy.
• the system 2 may provide balancing power to aid with balancing the supply and demand within the network.
• a system based on a battery unit 1 may be particularly useful for providing primary balancing power, e.g. for a timescale of up to 30 minutes or However, alternatively or additionally, it may also provide secondary balancing power, e.g. for timescales up to several hours.
• the system 2 may also comprise an electrical generator, such as a gas turbine, a photovoltaic system, a fuel cell, a wind turbine or a combined heat and power unit.
• the system may also be configured to provide reactive power compensation in order to counteract the reactive power in the power network. This may be advantageous since reactive power may limit the accessible capacity of the power network.
• a further application may be peak shaving, which denotes the process of reducing the peak power of an electricity consumer. That is, sharp peaks in the electricity use of a consumer (typically an industrial power consumer) may be levelled out using the energy storage system. This process may be beneficial for the overall power network stability.
• the system 2 may also be configured to atypical use of the network. That is, peak loads may be shifted out of a peak time window that may be specified by a network provider. Again, this process may be beneficial for the overall power network stability.
• an energy storage system 2 may be configured to provide emergency power and/or provide an uninterruptible power supply (UPS). That is, the system 2 may provide electricity for example during a power outage, i.e. in case the power networks breaks down. This may be beneficial as it allows to continue to run critical systems, e.g. medical systems in hospitals, and/or to properly shut down systems, e.g. to reduce the risk of damage to the system or data loss.
• UPS uninterruptible power supply
• system 2 may be configured for stand-alone operation, i.e. to function without a power network.
• system 2 may be part of a stand alone power system or remote area power supply.
• the system 2 may comprise, or be combined with, at least one electrical generator to provide electricity in a remote area without an accessible power network.
• the system 2 may be configured for self-consumption optimization, i.e. in combination with an electrical generator the system may be configured to store and provide the electrical energy of the electrical generator such that the amount of energy fed and/or drawn from the power network may be minimised.
• the energy storage system 2 in combination with a photovoltaic system may store the electricity produced when the sun is shining and provide the electricity to a user at times where it is required and no sun is shining, e.g. at night or in the morning.
• the first set 11 and the second set 12 may comprise identical battery modules 111, 121.
• the SOH of the second set 12 may degrade slower than the SOH of the first set 11 which may be primarily utilized and consequently the expected lifetime of the second set 12 may be longer.
• the first set 11 may be replaced after the corresponding SOH reaches a lower threshold SOH mm .
• This may be advantageous as the first set 11 may comprise less battery modules than the second set 12, that is the first set may comprise less than 50% of the capacity of the system, for example 30% or 20% of the total system capacity.
• the first set may comprise battery modules 111 that are different from the battery modules 121 of the second set 12, i.e. the battery modules 111, 121 of the first set 11 and the second set 12 may be distinct.
• the difference may be at least one or a combination of a difference in battery cell type, C-rate, capacity or SOH at the time of taking the system into operation.
• the difference in SOH may be at least 5%, preferably 10%.
• the first set may comprise new batteries with a SOH of at least 95%, i.e. batteries that have not been in use for a different application, whereas the second set may comprise second-use batteries, i.e. batteries that have been used in another application prior to the use in the battery unit.
• second-use batteries may be batteries that have been used in electric vehicles, such as electric cars.
• Such second-use batteries may comprise a SOH of at most 90%, preferably at most 85%. This may be advantageous as it may increase the economic efficiency of the battery unit 1 and thus the energy storage system 2 and further contribute to the environmental sustainability of the battery modules 121.
• the present invention relates to a method for storing and releasing electrical energy from a battery unit 1 of the system 2.
• the method very generally comprises a first step 41 of receiving a set of input parameters, wherein the set comprises at least one input parameter.
• An input parameter may for example be one of an amount of electrical energy and/or power to be stored or released, a current SOC of at least the first set of batteries 11 or the second set of batteries 12, a designated system lifetime, a minimal state of health (SOH mm ), an estimate of at least one SOH of at least a portion of the system, e.g. a set of batteries, a measurement of at least one SOH of at least a portion of the system, e.g.
• An operation mode may for example be power balancing or peak shaving.
• the second step 42 comprises receiving a request or determining a need for storing or providing electrical energy and/or power. That is, a request for storing or providing electrical energy and/or power may be received, e.g. through an external input, or determined, e.g. through measuring a frequency deviation in a power network.
• a next step 44 the distribution of the provided or stored electrical energy and/or power between the first set 11 and the second set 12 is optimized. That is, the method comprises optimizing the utilization of the two sets of modules 11, 12.
• the step 44 of optimizing the distribution of provided and/or stored electrical energy and/or power may in some embodiments comprise achieving substantially identical SOHs of the first set 11 and the second set 12 at a designated system lifetime and/or an economic lifetime of the system 2. For example, if the first set 11 comprises new battery modules 111 and the second set 12 comprises second-use battery modules 121 the SOH may be generally be different between the two sets 11, 12.
• the aging process i.e. reduction of the SOH
• the aging of the first set 11 (new cells) and the second set 12 (2nd use) is shown in terms of the development of the SOH with respect to time.
• the first set 11 comprises a SOH of 100 %.
• the second set 12 comprises a SOH of less than 100% due to a first use in a first cycle of the battery modules 121.
• the battery modules 121 of the second set comprised a SOH of 100% at the beginning of their first use, it declined during the duration of the first cycle as indicated by the black line.
• the SOH of both, the first set 11 and the second set 12 is reducing, or in other words the battery modules 111, 121 and the comprised battery cells 1111, 1211 are aging.
• the aging of the first set 11 is indicated by the dashed line, whereas the aging of the second set 12 is indicated by the solid line.
• the threshold for the usability of the battery cells in terms of their SOH is indicated by the minimal SOH (SOH mm ).
• the first set 11 is aging faster than the second set 12 (the slope of the dashed line is higher than the slope of the solid line during the battery unit cycle).
• the aging may for example be optimized that both sets reach the SOH mm basically at the designated system lifetime.
• the step 44 of optimizing the distribution of provided and/or stored electrical energy and/or power between the first and second set of modules 11, 12 may comprise optimizing the aging of the first and second set 11, 12 such that both sets 11, 12 reach the SOH min at about the same time, ideally corresponding to the designated system lifetime. This may be advantageous, as it may allow to prolong the lifetime of the battery cells 1211 in the second set 12 compared to a case where both sets are utilized identically.
• the step 44 of optimizing the distribution of provided and/or stored electrical energy and/or power between the first and second set of modules 11, 12 may for example comprise optimizing the aging of the first and second set 11, 12 such that the second set 12 may reach the SOH min at the designated system lifetime, whereas the first set 11 may age significantly faster such that the first set 11 or at least a portion of the first set 11 may be replaced during the system lifetime. Further, other optimization strategies according to a set of optimization parameters may be realized.
• the temperature of the battery cell has an impact on the calendar aging.
• the second major factor is cyclical ageing, i.e. ageing due to charging and discharging.
• the method may further allow to adjust the optimization based on new input, for example a new SOHmm, a new designated lifetime or new estimates for the predicted development of a SOH of a set of modules 11, 12 during the operating time of the system 2.
• Such a method may be particularly useful in an energy storage system 2 configured for providing balancing power, peak shaving or emergency power and/or an UPS.
• the step 44 of optimizing the distribution of provided and/or stored electrical energy and/or power between the first set 11 and the second set 12 comprises sparing the second set of battery modules 12. That is, in such embodiments the first set 11 may always be utilized and the second set of 12 may only be utilized if the first set cannot provide the capacity and/or C-rate to provide and/or store the required electrical energy and/or power at a time of demand. This may for example be preferable if the first and second set 11, 12, comprise identical battery modules 111, 121.
• the step 44 of optimizing the distribution of provided and/or stored electrical energy and/or power between the first set 11 and the second set 12 may comprise optimizing the distribution according to a set of parameters comprising at least one optimization parameter.
• Optimization parameters may for example be a designated system lifetime, SOH mm , a pre-set distribution, an estimate of at least one SOH of at least a portion of the system, e.g. a set of batteries, or the amount of energy required to be stored or provided, i.e. released, at a point in time, e.g. for a request of balancing power.
• the optimization may be based on at least one or a plurality of input parameters. For example, optimizing the distribution such that a substantially identical state of health (SOH) is achieved for each set of modules 11,12 may utilize an estimate or a measurement of a SOH of a set 11, 12, a module 111, 121 or a battery cell 1111, 1211, a designated lifetime or a minimal state of health (SOH mm ).
• SOH state of health
• a final step 45 the electrical energy and/or power is provided or stored according to the optimized distribution between the first and the second step 11, 12. That is, based on the optimization of the distribution of electrical energy and/or power (step 44) the energy is stored in the first set 11 and/or the second set 12.
• the method may further comprise a step 43 of estimating a future development of the SOH of the first and second set of battery modules 11, 12, respectively, based on a set of prediction data.
• Such prediction data may comprise the current SOH of the set of battery modules, a historical development of the SOH of the set of battery modules, a historical utilization of the set of battery modules and/or a predicted utilization of the set of battery modules.
• the prediction data may also be part of the input parameters.
• the system 2 may be configured to provide balancing power. That is, the system may be configured to contribute to the balancing of the differences between electricity input and output of a power grid, also referred to as power network.
• the current deviation can typically be determined by the deviation of a grid frequency from its setpoint, the setpoint may for example be 50 Hz.
• the grid frequency may also be known as power grid frequency, network frequency, mains frequency or supply frequency.
• Figure 6 shows an example for a standardized characteristic curve of the balancing power output as a function of the frequency deviation.
• power is taken from the mains, i.e. drawn from the power network, (typically in accordance with a specified characteristic curve); in the case of underfrequency, i.e. a grid frequency above the set point, power is delivered to the power network, i.e. fed into the power network.
• the so-called primary balancing power is the fastest form of balancing power after the rotating masses in the network (the so-called instantaneous reserve).
• the secondary balancing power or the so-called minute reserve may be provided.
• the balancing power may also be referred to as control power. Balancing power may only be provided if the deviation is larger than a minimal threshold, for example if the frequency deviates by more than 20 mHz, as shown in Fig. 6.
• the step of optimizing the distribution of the provided and/or stored electrical energy and/or power comprises between the first set of modules 11 and the second set of modules 12 may further comprise monitoring of the volume of the provided balancing power and or monitoring the gradient of the provided balancing power at the beginning of a stabilisation action. That is, the power may be distributed according to the overall volume of requested balancing power. Further, also the gradient may be monitored to determine the best distribution of the required balancing power.
• providing balancing power includes feeding power to a power network as well as drawing power from a power network. That is, providing balancing power includes storing and providing/releasing electrical energy and/or power from the energy storage system 2.
• Fig. 7 exemplary data of the frequency distribution of the grid frequency in the synchronous grid of Continental Europe in 2014 is shown.
• the data are derived from real balancing power applications in the power network.
• a fraction of the prequalified power of the system 2 such as 20% to 25%, may completely cover the majority of the balancing power applications.
• a significant fraction of the prequalified power of the system 2 may not be required for the majority of the balancing power application.
• the described method in a system 2 configured for providing balancing power as the first set 11 may provide the power for the majority of the balancing power applications while the second set 12 may be kept at a SOC close to 50%, such as 40% to 60% for the majority of the operation time, e.g. 70% of the operation time.
• a relative term such as "about”, “substantially” or “approximately” is used in this specification, such a term should also be construed to also include the exact term. That is, e.g., "substantially straight” should be construed to also include “(exactly) straight”.
• step (X) preceding step (Z) encompasses the situation that step (X) is performed directly before step (Z), but also the situation that (X) is performed before one or more steps (Yl), ..., followed by step (Z).
• step (Z) encompasses the situation that step (X) is performed directly before step (Z), but also the situation that (X) is performed before one or more steps (Yl), ..., followed by step (Z).

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• 2019
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