Energy management system for hybrid battery pack

Abstract

An energy management system for a hybrid battery pack (HPB) comprising a high-energy assembly (HE) and a high-power assembly (HP), which are connected through one or more DC / DC converters (Conv, Conv1, Conv2) to one another and / or to a DC bus supplying power to a load, is disclosed, wherein the energy management system is configured to decide, by controlling the power output from the one or more DC / DC converters (Conv, Conv1, Conv2), how large a share of the total power delivered from the hybrid battery pack (HPB) is delivered by the high-energy assembly (HE) and by the high-power assembly (HP), respectively, wherein the energy management system is configured to switch between two or more modes of operation (MO-1, MO-2, MO-3, MO-4), with each of which a specific control criterion (CC-1, CC-2, CC-3) is associated, wherein the two or more modes of operation (MO-1, MO-2, MO-3, MO-4) are ranked in a hierarchy of priority depending on the importance of their respective associated control criteria (CC-1, CC-2, CC-3), and wherein the energy management system is arranged to operate in the highest ranking mode of operation (MO-1, MO-2, MO-3, MO-4), for which the associated control criterion (CC-1, CC-2, CC-3) is fulfilled. Furthermore, a hybrid battery pack (HPB) controlled by such an energy management system and an electric vehicle comprising such a hybrid energy pack are disclosed.

Description

[0001] ENERGY MANAGEMENT SYSTEM FOR HYBRID BATTERY PACK

[0002] Field of the invention

[0003] The present invention relates to an energy management system for a hybrid battery pack, in particular for a hybrid battery pack configured to supply power to an inverter and a motor of an electric vehicle.

[0004] Background of the invention

[0005] Hybrid battery packs comprising high-energy cells as well as high-power cells are well- suited for powering electric vehicles because a large amount of energy can be stored in the high-energy cells for obtaining a long driving range and, at the same time, large amounts of energy can quickly be released from the high-power cells during accelerations and other situations, in which high levels of power are needed. The optimal number and capacity of high-energy cells and high-power cells, respectively, depend on the performance requirements of the vehicle (minimum charging time, power requirement, driving range, etc.).

[0006] However, managing the energy delivery from such a hybrid battery pack is far from simple. If, for instance, the power consumption is divided equally between the two types of battery cells, the high-power cells are likely to be fully discharged, while a substantial amount of energy is still stored in the high-energy cells. Furthermore, a number of different performance parameters (such as the driving range of the electric vehicle and the lifetime of the hybrid battery pack) should be optimised, and the optimal strategies for optimising these performance parameters often contradict each other. Thus, the algorithm for managing the energy delivery from a hybrid battery pack may be complex, and the processing capability requirements of the computer equipment performing this task may be high.

[0007] Brief description of the invention

[0008] It is a purpose of the present invention to provide an energy management system for a hybrid battery pack, which energy management system overcomes or at least significantly reduces the above-mentioned disadvantages of energy management systems known in the art.

[0009] Thus, in a first aspect of the invention, it relates to an energy management system for a hybrid battery pack comprising a high-energy assembly and a high-power assembly, wherein the high-energy assembly comprises one or more high-energy battery cells, which are internally connected in parallel and / or in series, and the high-power assembly comprises one or more high-power battery cells, which are internally connected in parallel and / or in series, wherein the high-energy assembly and the high- power assembly are connected through one or more DC / DC converters to one another and / or to a DC bus supplying power to a load, such as an inverter and a motor of an electric vehicle, wherein the energy management system is configured to decide, by controlling the power output from the one or more DC / DC converters, how large a share of the total power delivered from the hybrid battery pack is delivered by the high- energy assembly and by the high-power assembly, respectively, wherein the energy management system is configured to switch between two or more modes of operation depending on the present state-of-charge and temperatures of the high-energy assembly and / or the high-power assembly, wherein a specific control criterion is associated with each of the two or more modes of operation, wherein the two or more modes of operation are ranked in a hierarchy of priority depending on the importance of their respective associated control criteria, and wherein the energy management system is arranged to operate in the highest ranking mode of operation, for which the associated control criterion is fulfilled.

[0010] With this configuration of the energy management system, each mode of operation can be dedicated to the optimization of a single parameter, and the energy management system can optimize one performance parameter at a time, thereby avoiding to optimise plurality of parameters simultaneously, which would repeatedly have led to a conflict between different optimisation goals. The control criteria do not necessarily require large computational requirements either, and thus, the energy management system of the present invention is computationally significantly less intensive than systems known in the art, and it can easily be implemented in a microcontroller.

[0011] In an embodiment of the invention, each of the control criteria of the two or more modes of operation are checked continuously or, preferably, at regular time intervals, such as once every second, for determining the mode of operation in which the energy management system is to be operated.

[0012] The frequency, at which the control criteria are checked, and thereby the frequency, at which the energy management system is able to switch between the two or more modes of operation can easily be varied according to different requirements for the energy management system, which may typically be decided by the manufacturer of the load, such as an electric vehicle, for which the hybrid battery pack is to be used.

[0013] In an embodiment of the invention, the two or more modes of operation comprise a first, preferably highest-ranking, mode of operation, wherein the power output from theone or more DC / DC converters is controlled in such a way that the share of the total power delivered from the hybrid battery pack, which is delivered by the high-energy assembly, is dynamically reduced if the temperature of the high-energy assembly is higher than the temperature of the high-power assembly, and dynamically increased if the temperature of the high-energy assembly is lower than the temperature of the high- power assembly.

[0014] This first mode of operation is aimed at preventing thermal runaway, i.e. overheating of the hybrid battery pack, which may be devastating for the function and structural integrity of the hybrid battery pack. In severe cases, overheating may even cause the hybrid battery pack to catch fire, which, in turn, may result in seriously dangerous situations for users of equipment, such as drivers and passengers of electric vehicles being powered by the hybrid battery pack. This is also the reason for this mode of operation preferably being given higher priority than the other modes of operation, which are aimed more at optimising parameters than at avoiding dangers and destruction of the hybrid battery pack.

[0015] In an embodiment of the invention, the first control criterion associated with the first mode of operation is that the temperature difference between the high-energy assembly and the high-power assembly has been above a predefined temperature difference threshold for a period of time, which is longer than a first predefined continuous period of time. If one of the two assemblies is significantly warmer than the other one for a longer period of time, it is a reliable indicator that the warmest assembly may be at risk of overheating and that cautiousness should be taken to avoid such a scenario. The reason for this is that the temperature of a battery cell, which is exposed to thermal runaway, will increase rapidly and differ significantly from the temperature of other battery cells without thermal runaway.

[0016] In an embodiment of the invention, the temperature difference is defined as the difference between the highest temperature measured within the high-energy assembly and the highest temperature measured within the high-power assembly.

[0017] The first mode of operation being aimed at detecting too high temperatures, the optimal results are obtained by comparing the highest temperatures measured within the two assemblies, respectively.

[0018] In an embodiment of the invention, the predefined temperature difference threshold is between 5° C and 20° C, preferably between 8° C and 15° C, such as 10° C.

[0019] In an embodiment of the invention, the first predefined continuous period of time is between 2 minutes and 15 minutes, preferably between 3 minutes and 10 minutes, such as 5 minutes.

[0020] The optimal predefined temperature difference and the optimal first predefined continuous period of time depend significantly on the capacity and configuration of the hybrid battery pack, the energy delivery of which is managed by the energy management system. However, the above-defined temperature and time intervals have proven to cover the optimal parameters for the vast majority of hybrid battery packs.

[0021] In an embodiment of the invention, if the first control criterion is still fulfilled when the energy management system has operated in the first mode of operation for a second predefined continuous period of time, the energy management system is configured to take action to cause the operation of the load, which is powered by the hybrid battery pack, to be discontinued. Due to the severe risks involved, if a thermal runaway is not prevented, this first mode of operation is preferably configured as a “fault mode”, in which the operation can be discontinued if the risk has not been successfully addressed and reduced within a certain period of time. In a first step, the energy management system will typically warn the operator of the machine (e.g. a driver of an electric vehicle) powered by the hybrid battery pack about the risk and inform the operator to stop the operation of the machine. Later, preferably following one or more additional warning, if the operation has not been stopped, the energy management system may automatically “trip” the system by simply discontinuing the supply of power from the hybrid battery pack to the machine being powered thereby.

[0022] In an embodiment of the invention, the second predefined continuous period of time is between 10 minutes and 30 minutes, preferably between 15 minutes and 25 minutes, such as 20 minutes.

[0023] The optimal second predefined continuous period of time also depends on the capacity and configuration of the hybrid battery pack, the energy delivery of which is managed by the energy management system. However, the above-defined interval has proven to cover the optimal second predefined continuous period for the vast majority of hybrid battery packs.

[0024] In an embodiment of the invention, the two or more modes of operation further comprise a second mode of operation, wherein the power output from the one or more DC / DC converters is controlled in such a way that the level of energy stored in the high-energy assembly is kept at a dynamically set level,

[0025] The purpose of this second mode of operation is to manage the power delivered from the hybrid battery pack when the amount of energy stored therein is at a low level. If one of the assemblies reaches a critically low state-of-charge, the total power capability of the hybrid battery pack is hampered, and it cannot be operated any longer. Therefore, it is the aim of this second mode of operation to ensure that the two assemblies discharge in such a way that they will reach their respective critically low state-of-charge at the same time. This can be obtained by controlling the output from the one or more DC / DC converters in such a way that the level of energy stored in the high-energy assembly (or alternatively, the level of energy stored in the high-power assembly) is controlled to a set level corresponding to a fixed percentage of the total amount of stored energy in the complete hybrid pack.

[0026] In an embodiment of the invention, the set level (E*HE) is defined by the equation wherein Enet is the total amount of stored energy in the hybrid battery pack, PHE, max is the maximum power, which can be delivered by the high-energy assembly, and PHP, max is the maximum power, which can be delivered by the high-power assembly.

[0027] Advantageously, the percentage of the total amount of stored energy to be used for controlling the energy level in the high-energy assembly (or alternatively the high- power assembly) can be calculated from the maximum power, which can be delivered by the high-energy assembly and the high-power assembly, respectively, as shown in this formula.

[0028] In general, the maximum power that can be delivered from an assembly is decided by the power rating of that assembly. However, it should be noted that if the power from a given assembly is delivered through a DC / DC converter, the maximum power, which can be delivered from that assembly will be limited to the power rating of the DC / DC converter instead, should it be lower than the power rating of the assembly.

[0029] In an embodiment of the invention, the second control criterion associated with the second mode of operation is that the state-of-charge of the complete hybrid battery pack is less than a first predefined state-of-charge threshold value.

[0030] This second mode of operation being aimed at controlling the hybrid battery pack at low energy levels, it is advantageous to use a threshold for the total state-of-charge of the hybrid battery pack as its control criterion indicating that such a low energy level has now been reached. In an embodiment of the invention, the first predefined state-of-charge threshold value is between 15 % and 35 % of full charge, preferably between 20 % and 30 % of full charge, such as 25 % of full charge.

[0031] The optimal first predefined state-of-charge threshold value may depend on the capacity and configuration of the hybrid battery pack, the energy delivery of which is managed by the energy management system. However, the above-defined intervals have proven to cover the optimal parameters for the vast majority of hybrid battery packs.

[0032] In an embodiment of the invention, the two or more modes of operation further comprise a third mode of operation, wherein the power output from the one or more DC / DC converters is controlled in such a way that the level of energy EHP stored in the high-power assembly is reduced to a minimum level E*HP.

[0033] This third mode of operation aims at making the hybrid battery pack ready for charging by reducing the fast charging time of the hybrid battery pack as much as possible. Therefore, the overall idea in this mode of operation is to use energy primarily from the high-power assembly, which can be recharged significantly faster than the high-energy assembly.

[0034] In an embodiment of the invention, the third control criterion associated with the third mode of operation is that the state-of-charge of the complete hybrid battery pack is higher than a second predefined state-of-charge threshold value and that the state-of- charge of the high-power assembly is lower than a third predefined state-of-charge threshold value, wherein the third predefined state-of-charge threshold value is lower than the second predefined state-of-charge threshold value.

[0035] It is relevant to operate the energy management system in this third mode of operation when the overall state-of-charge is still not so low that operating in the above-described second mode of operation would be prioritised but, at the same time, the state-of- charge of the high-power assembly is so low that charging of the hybrid battery pack is imminent. Therefore, a suitable third control criterion is that the overall state-of-charge of the hybrid battery pack is above a certain level and, at the same time, the state-of- charge of the high-power assembly is below a certain level. In an embodiment of the invention, the second predefined state-of-charge threshold value is between 15 % and 35 % of full charge, preferably between 20 % and 30 % of full charge, such as 25 % of full charge.

[0036] In an embodiment of the invention, the first predefined state-of-charge threshold value and the second predefined state-of-charge threshold value are identical.

[0037] In an embodiment of the invention, the third predefined state-of-charge threshold value is between 10 % and 30 % of full charge, preferably between 15 % and 25 % of full charge, such as 20 % of full charge.

[0038] The optimal predefined state-of-charge threshold values depend significantly on the capacity and configuration of the hybrid battery pack, the energy delivery of which is managed by the energy management system. However, the above-defined intervals have proven to cover the optimal parameters for the vast majority of hybrid battery packs.

[0039] In an embodiment of the invention, the two or more modes of operation further comprise a fourth mode of operation, wherein the share (%PHE) of the total power delivered from the hybrid battery pack, which is delivered by the high-energy assembly, is computed by the equation wherein RLILHE is the remaining useful life of the high-energy assembly, RLILHP is the remaining useful life of the high-power assembly, Emax, HE is the maximum stored energy capability of the high-energy assembly, Emax, HP is the maximum stored energy capability of the high-power assembly, SOHHE is the state of health of the high-energy assembly, and SOHHP is the state of health of the high-power assembly.

[0040] The remaining useful life of a battery cell indicates how long it can operate till it reaches its end of life for that application. Conventionally, for electric vehicles the end of life of a battery cell occurs when its state of health reaches 80 % or its internal resistance is doubled. This parameter is normally estimated using an algorithm which runs online. The maximum stored energy capability of a battery cell denotes the initial energy capacity of the battery cell when manufactured and is provided by the manufacturer. The state of health of a battery cell indicates the actual energy capacity of the battery cell at present (during its operation) compared to the capacity mentioned by the manufacturer. This parameter is also estimated online.

[0041] The purpose of this fourth mode of operation is to ensure that the two assemblies degrade at similar rates so that the total hybrid battery pack does not need to be serviced or replaced due to the degradation of one assembly while the other assembly could run for a much longer time before needing such service or replacement.

[0042] It has turned out that this can be obtained by calculating the share of the total power to be delivered, which is delivered by the high-energy assembly, according to the above- mentioned equation. Alternatively, the share to be delivered by the high-power assembly could be calculated according to a similar equation.

[0043] In an embodiment of the invention, the fourth mode of operation is the lowest-most ranking of the two or more modes of operation, and wherein the fourth control criterion associated with the fourth mode of operation is that none of the control criteria associated with any higher ranking modes of operation are fulfilled.

[0044] This fourth mode of operation will typically be the one with the lowest priority. Therefore, in most cases, no specific control criterion is needed for this mode of operation.

[0045] In a second aspect of the invention relates to a hybrid battery pack comprising a high- energy assembly and a high-power assembly, wherein the high-energy assembly comprises one or more high-energy battery cells, which are internally connected in parallel and / or in series, and the high-power assembly comprises one or more high- power battery cells, which are internally connected in parallel and / or in series, wherein the high-energy assembly and the high-power assembly are connected through one or more DC / DC converters to one another and / or to a DC bus supplying power to a load, and wherein the operation of the hybrid battery pack is controlled by an energy management system as described above.

[0046] In an embodiment of the invention, the hybrid battery pack is configured to supply power to an inverter and a motor of an electric vehicle. As mentioned above, hybrid battery packs comprising high-energy cells as well as high-power cells are well-suited for powering electric vehicles.

[0047] In a third aspect of the invention, it relates to an electric vehicle comprising a hybrid battery pack as described above..

[0048] The drawings

[0049] In the following, a few exemplary embodiments of the invention are described in more detail with reference to the drawings, of which

[0050] Fig. 1 is a schematic drawing of a hybridisation architecture, in which a hybrid battery pack according to an embodiment of the invention may be applied,

[0051] Fig. 2 is a schematic drawing of a first embodiment of a hybrid battery pack according to the invention,

[0052] Fig. 3 is a schematic drawing of a second embodiment of a hybrid battery pack according to the invention,

[0053] Fig. 4 is a schematic drawing of a third embodiment of a hybrid battery pack according to the invention,

[0054] Fig. 5 is a flowchart describing the overall structure of an energy management system according to an embodiment of the invention,

[0055] Fig. 6 illustrates schematically a control implementation for a first mode of operation of an energy management system according to an embodiment of the invention,

[0056] Fig. 7 illustrates schematically a control implementation for a second mode of operation of an energy management system according to an embodiment of the invention, and Fig. 8 illustrates schematically a control implementation for a third mode of operation of an energy management system according to an embodiment of the invention,

[0057] Detailed description

[0058] Fig. 1 is a schematic drawing of a hybridisation architecture, in which a hybrid battery pack HBP according to an embodiment of the invention may be applied. In the illustrated application, the hybrid battery pack HBP delivers DC power to a three-phase inverter Inv through a DC link (indicated by the polarities + and — ). The inverter Inv converts the DC power into a three-phase AC power, which is supplied to a motor M, such as the motor of an electric vehicle. Due to the combination of a high-energy assembly HE (not shown in Fig. 1) comprising high-energy battery cells, which allow storage of large amounts of energy resulting in a long driving range, and a high-power assembly HP (not shown in Fig. 1) comprising high-power battery cells, which are able to release relatively large amounts of energy in a short time when high levels of power are needed, hybrid battery packs HBP are well-suited for powering electric vehicles.

[0059] Fig. 2 is a schematic drawing of a first embodiment of a hybrid battery pack HBP according to the invention. Basically, this embodiment of the hybrid battery pack HBP consists of a high-energy assembly HE, a high-power assembly HP and a bidirectional DC / DC converter Conv. The high-energy assembly HE comprises one or more high- energy battery cells, which are internally connected in parallel and / or in series and, similarly, the high-power assembly HP comprises one or more high-power battery cells, which are also internally connected in parallel and / or in series. The number, capacities and configuration of the battery cells within the high-energy assembly HE and the high- power assembly HP, respectively, depend on the performance requirements of the load to be powered by the hybrid battery pack HBP.

[0060] The high-energy assembly HE is connected through the DC / DC converter Conv to the high-power assembly HP, which, in turn, is coupled directly to a DC link for supplying power to a load, such as an inverter Inv and a motor M of an electric vehicle. The load is not shown in Fig. 2. The total power delivered from the hybrid battery pack HBP through the DC link to the load corresponds to the current power requirements from the load. By controlling the power output of the DC / DC converter Conv, the energy management system of the present invention decides how large a share of this total power is delivered from the high-energy assembly HE, the remaining part of the total power being delivered from the high-power assembly HP, which is coupled directly to the DC link.

[0061] Fig. 3 is a schematic drawing of a second embodiment of a hybrid battery pack HBP according to the invention, in which the positions of the high-energy assembly HE and the high-power assembly HP have been reversed. Thus, in this embodiment, the energy management system decides how large a share of the total power is delivered from the high-power assembly HP by controlling the power output from the DC / DC converter Conv, and the high-energy assembly HE, which is coupled directly to the DC link, will deliver the remaining part of the total power required by the load.

[0062] Fig. 4 is a schematic drawing of a third embodiment of a hybrid battery pack HBP according to the invention, in which the high-energy assembly HE is connected to the DC link through a first bidirectional DC / DC converter Convl , and the high-power assembly HP is connected to the DC link through a second bidirectional DC / DC converter Conv2. This means that, in order to control the shares of the total power, which are delivered from the high-energy assembly HE and the high-power assembly HP, respectively, the energy management system must control the power output of both the DC / DC converters Convl, Conv2.

[0063] Fig. 5 is a flowchart describing the overall structure of an energy management system according to an embodiment of the invention. In the illustrated embodiment, the energy management system is configured to switch between four different modes of operation MO-1 , MO-2, MO-3, MO-4 in such a way that the energy management system can only operate in one of the four modes of operation MO-1 , MO-2, MO-3, MO-4 at any given time. It will be clear to the person skilled within the art that, in other embodiments of the energy management system, the number of modes of operation may be higher or lower than four, meaning that some of the modes of operation MO-1, MO-2, MO-3, MO-4 in the embodiment described below may be omitted, and / or other modes of operation not described herein may be added to the energy management system. A specific control criterion CC-1, CC-2, CC-3 is associated with each of the four modes of operation MO-1 , MO-2, MO-3, MO-4, and the four modes of operation MO-1 , MO-2, MO-3, MO-4 are ranked in a hierarchy of priority depending on the importance of their respective associated control criteria CC-1, CC-2, CC-3, and the energy management system is arranged to operate in the highest ranking mode of operation MO-1 , MO-2, MO-3, MO-4, for which the associated control criterion CC-1 , CC-2, CC-3 is fulfilled.

[0064] In the illustrated embodiment, the first mode of operation MO-1 is the highest-ranking mode of operation followed in a prioritised order by the second MO-2, the third MO-3 and the fourth MO-4 mode of operation. The fourth mode of operation MO-4 being the lowest ranking mode of operation, the fourth control criterion associated with that specific mode of operation is that none of the control criteria CC-1, CC-2, CC-3 associated with any of the higher ranking modes of operation MO-1, MO-2, MO-3 are fulfilled.

[0065] The first and highest-ranking mode of operation MO-1 of the illustrated embodiment of the energy management system is a “Thermal runaway prevention” mode, in which the power output from the one or more DC / DC converters Conv, Convl, Conv2 is controlled in such a way that the share of the total power delivered from the hybrid battery pack HBP, which is delivered by the high-energy assembly HE, is dynamically reduced if the temperature TPE of the high-energy assembly HE is higher than the temperature TPH of the high-power assembly HP, and dynamically increased if the temperature TPE of the high-energy assembly HE is lower than the temperature TPH of the high-power assembly HP.

[0066] Thermal runaway consists of overheating of the hybrid battery pack HBP, typically originating from one or a few of the battery cells of the hybrid battery pack HBP, and may be devastating for the function and structural integrity of the hybrid battery pack HBP. Even devastating and life-threatening fires may be the result of such thermal runaways and, therefore, this first mode of operation MO-1 has the highest priority and it configured as a “fault mode”, in which the operation can be discontinued, if the risk has not been successfully addressed and reduced within a certain period of time.

[0067] Because the temperature of a battery cell, which is exposed to thermal runaway, will typically increase rapidly and differ significantly from the temperature of other battery cells without thermal runaway, it is a reliable indicator of the risk of a potential thermal runaway that one of the two assemblies is significantly warmer than the other one for a longer period of time. Preferably, the compared temperatures THE, THP are the maximum temperatures measured within the high-energy assembly HE and the high- power assembly HP, respectively.

[0068] Therefore, the first control criterion CC-1 associated with the first mode of operation MO-1 is that the temperature difference |THE - THP| between the high-energy assembly HE and the high-power assembly HP has been above a predefined temperature difference threshold Tset for a period of time t™, which is longer than a first predefined continuous period of time t-TH.set. If this first control criterion CC-1 is fulfilled, the energy management system will always operate in the first mode of operation MO-1 .

[0069] Fig. 6 illustrates schematically a control implementation for this first mode of operation MO-1 of the energy management system illustrated in Fig. 5. The illustrated control implementation relates to a hybrid battery back HBP, in which the high-energy assembly HE is connected to the DC link through a DC / DC converter Conv, Convl

[0070] A controller Ctr compares the temperature THE of the high-energy assembly HE with the temperature THP of the high-power assembly HP. The controller Ctr calculates a percentage of the total power, which should be delivered by the high-energy assembly HE for minimising the difference between the two temperatures THE, THP, and multiplies the calculated percentage with a total power reference P*ref for obtaining a power reference P*HE for the DC / DC converter Conv, Convl between the high-energy assembly HE and the DC link. This power reference P*HE is used for controlling the DC / DC converter Conv, Convl so that the desired percentage of the total power is delivered by the high-energy assembly HE through the DC / DC converter Conv, Convl . If the hybrid battery pack HBP being controlled by the energy management system comprises a high-power assembly HP connected to the DC link through a DC / DC converter Conv, Conv2, a similar control implementation may be used for controlling the percentage of the total power, which is delivered by the high-power assembly HP instead.

[0071] The second mode of operation MO-2 of the illustrated embodiment of the energy management system is a “Low energy” mode, in which the power output from the one or more DC / DC converters Conv, Convl , Conv2 is controlled in such a way that the level of energy EHE stored in the high-energy assembly HE is kept at a dynamically set level E*HE. Thus, the second control criterion CC-2 associated with this second mode of operation MO-2 is that the state-of-charge SOCHBP of the complete hybrid battery pack HBP is less than a first predefined state-of-charge threshold value SOCHBP, min. If this second control criterion CC-2 is fulfilled, and the first control criterion CC-1 is not fulfilled, the energy management system will operate in the second mode of operation MO-2.

[0072] It is the aim of this second mode of operation MO-2 to ensure that the two assemblies HE, HP discharge in such a way that they will reach their respective critically low state- of-charge, at which they cannot any longer be operated, at the same time. This is obtained by ensuring that the levels of energy EHE, EHP stored in the two assemblies HE, HP correspond to the ratio of maximum power that they can deliver, respectively. Thus, the aim is to keep the level of energy EHE stored in the high-energy assembly HE as close to a set level E*HE, which is a fixed percentage of the total amount of stored energy in the complete hybrid pack HBP defined by the equation wherein Enet is the total amount of stored energy in the hybrid battery pack, PHE, max is the maximum power, which can be delivered by the high-energy assembly, and PHP, max is the maximum power, which can be delivered by the high-power assembly.

[0073] Fig. 7 illustrates schematically a control implementation for this second mode of operation MO-2 of the energy management system illustrated in Fig. 5. The illustrated control implementation relates to a hybrid battery back HBP, in which the high-energy assembly HE is connected to the DC link through a DC / DC converter Conv, Convl.

[0074] A controller Ctr compares the level of energy EHE stored in the high-energy assembly HE with the set level E*HE. The controller Ctr calculates a percentage of the total power, which should be delivered by the high-energy assembly HE for minimising the difference between the two levels of energy EHE, E*HE, and multiplies the calculated percentage with a total power reference P*ref for obtaining a power reference P*HE for the DC / DC converter Conv, Convl between the high-energy assembly HE and the DC link. This power reference P*HE is used for controlling the DC / DC converter Conv, Convl so that the desired percentage of the total power is delivered by the high-energy assembly HE through the DC / DC converter Conv, Convl . If the hybrid battery pack HBP being controlled by the energy management system comprises a high-power assembly HP connected to the DC link through a DC / DC converter Conv, Conv2, a similar control implementation may be used for controlling the percentage of the total power, which is delivered by the high-power assembly HP instead.

[0075] The third mode of operation MO-3 of the illustrated embodiment of the energy management system is a “Minimum fast charging time” mode, in which the power output from the one or more DC / DC converters Conv, Convl , Conv2 is controlled in such a way that the level of energy EHP stored in the high-power assembly HP is reduced to a minimum level E*HP.

[0076] The third control criterion CC-3 associated with the third mode of operation MO-3 is that the state-of-charge SOCHBP of the complete hybrid battery pack HBP is higher than a second predefined state-of-charge threshold value, which in the illustrated embodiment is equal to the first predefined state-of-charge threshold value SOCHBP, min, and that the state-of-charge SOCHP of the high-power assembly HP is lower than a third predefined state-of-charge threshold value SOCHP, min. If this third control criterion CC-3 is fulfilled, and none of the first control criterion CC-1 and the second control criterion are fulfilled, the energy management system will operate in the third mode of operation MO-3.

[0077] The aim of this third mode of operation MO-3 is to make the high-power assembly HP of the hybrid battery pack HBP ready for charging, thus reducing the fast charging time of the hybrid battery pack HBP as much as possible. Therefore, the overall idea in this third mode of operation MO-3 is to use energy primarily from the high-power assembly HP, which can be recharged significantly faster than the high-energy assembly HE. If the high-power assembly HP is discharged to a set minimum level EHP, min and the high- energy assembly HE is only discharged to a lesser degree, the high-power assembly HP can be fully charged during fast charging, while the high-energy assembly HE is charged to a certain extent. If, on the other hand, the high-power assembly HP is not completely discharged to the set minimum level EHP, min, and the high-energy assembly HE is discharged to a larger degree, the fast-charging capability will not be fully utilised.

[0078] Fig. 8 illustrates schematically a control implementation for this third mode of operation MO-3 of the energy management system illustrated in Fig. 5. The illustrated control implementation relates to a hybrid battery back HBP, in which the high-energy assembly HE is connected to the DC link through a DC / DC converter Conv, Convl.

[0079] A controller Ctr compares the level of energy EHP stored in the high-power assembly HP with a set minimum level EHP, min. The controller Ctr calculates a percentage of the total power, which should be delivered by the high-energy assembly HE for minimising the difference between the levels two levels EHP, EHP, min, and multiplies the calculated percentage with a total power reference P*ref for obtaining a power reference P*HE for the DC / DC converter Conv, Convl between the high-energy assembly HE and the DC link. This power reference P*HE is used for controlling the DC / DC converter Conv, Convl so that the desired percentage of the total power is delivered by the high-energy assembly HE through the DC / DC converter Conv, Convl . If the hybrid battery pack HBP being controlled by the energy management system comprises a high-power assembly HP connected to the DC link through a DC / DC converter Conv, Conv2, a similar control implementation may be used for controlling the percentage of the total power, which is delivered by the high-power assembly HP instead.

[0080] The fourth and lowest ranking mode of operation MO-4 of the illustrated embodiment of the energy management system is an “Equal battery subpack degradation” mode, in which the share (%PHE) of the total power delivered from the hybrid battery pack, which is delivered by the high-energy assembly, is computed by the equation wherein RLI LHE is the remaining useful life of the high-energy assembly HE, RLI LHP is the remaining useful life of the high-power assembly HP, Emax, HE is the maximum stored energy capability of the high-energy assembly HE, Emax, HP is the maximum stored energy capability of the high-power assembly HP, SOHHE is the state of health of the high-energy assembly HE, and SOHHP is the state of health of the high-power assembly HP. This fourth mode of operation MO-4 typically being the one with the lowest priority, the fourth control criterion associated with this mode of operation is simply that none of the control criteria CC-1 , CC-2, CC-3 associated with any of the higher ranking modes of operation MO-1 , MO-2, MO-3 are fulfilled.

[0081] The aim of this fourth mode of operation MO-4 is to ensure that the two assemblies HE, HP degrade at similar rates so that the total hybrid battery pack HBP does not need to be serviced or replaced due to the degradation of one assembly HE; HP while the other assembly HP; HE could run for a much longer time before needing such service or replacement. This can be obtained by calculating the share of the total power to be delivered, which is delivered by the high-energy assembly HE, according to the above- mentioned equation. Alternatively, the share to be delivered by the high-power assembly HP could be calculated according to a similar equation.

[0082] List of references used in the drawings

[0083] Conv Bidirectional DC / DC converter

[0084] Convl First bidirectional DC / DC converter

[0085] Conv2 Second bidirectional DC / DC converter

[0086] Ctr Controller

[0087] EHE Level of energy stored in the high-energy assembly

[0088] E*HE Set level of energy stored in the high-energy assembly

[0089] EHP Level of energy stored in the high-power assembly

[0090] EHP, min Set minimum level of energy stored in the high-power assembly HBP Hybrid battery pack

[0091] HE High-energy assembly

[0092] HP High-power assembly

[0093] Inv Three-phase inverter

[0094] M Motor

[0095] MO-1 First mode of operation

[0096] MO-2 Second mode of operation

[0097] MO-3 Third mode of operation

[0098] MO-4 Fourth mode of operation

[0099] P*HE Power reference for DC / DC converter between high-energy assembly and DC link

[0100] P ref Total power reference

[0101] SOCHBP State-of-charge for the full hybrid battery pack SOCHBP, min First predefined state-of-charge threshold value SOCHP State-of-charge for the high-power assembly SOCHP, min Third predefined state-of-charge threshold value tth Time with too large temperature difference tth, set First predefined continuous period of time

[0102] THE Temperature of high-energy assembly

[0103] THP T emperature of high-power assembly

[0104] Tset Predefined temperature difference threshold Items describing different embodiments

[0105] 1. An energy management system for a hybrid battery pack (HPB) comprising a high-energy assembly (HE) and a high-power assembly (HP), wherein the high-energy assembly (HE) comprises one or more high-energy battery cells, which are internally connected in parallel and / or in series, and the high-power assembly (HP) comprises one or more high-power battery cells, which are internally connected in parallel and / or in series, wherein the high-energy assembly (HE) and the high-power assembly (HP) are connected through one or more DC / DC converters (Conv, Convl , Conv2) to one another and / or to a DC bus supplying power to a load, such as an inverter (Inv) and a motor (M) of an electric vehicle, wherein the energy management system is configured to decide, by controlling the power output from the one or more DC / DC converters (Conv, Convl, Conv2), how large a share of the total power delivered from the hybrid battery pack (HPB) is delivered by the high-energy assembly (HE) and by the high-power assembly (HP), respectively, wherein the energy management system is configured to switch between two or more modes of operation (MO-1, MO-2, MO-3, MO-4) depending on the present state-of-charge (SOCHBP, SOCHP) and temperatures (THE, THP) of the high-energy assembly (HE) and / or the high-power assembly (HP), wherein a specific control criterion (CC-1 , CC-2, CC-3) is associated with each of the two or more modes of operation (MO-1, MO-2, MO-3, MO-4), wherein the two or more modes of operation (MO-1 , MO-2, MO-3, MO-4) are ranked in a hierarchy of priority depending on the importance of their respective associated control criteria (CC-1 , CC-2, CC-3), and wherein the energy management system is arranged to operate in the highest ranking mode of operation (MO-1, MO-2, MO-3, MO-4), for which the associated control criterion (CC-1 , CC-2, CC-3) is fulfilled.

[0106] 2. The energy management system according to item 1 , wherein each of the control criteria (CC-1, CC-2, CC-3) of the two or more modes of operation (MO-1, MO-2, MO-3, MO-4) are checked continuously or, preferably, at regular time intervals, such as once every second, for determining the mode of operation (MO- 1 , MO-2, MO-3, MO-4), in which the energy management system is to be operated.

[0107] 3. The energy management system according to item 1 or 2, wherein the two or more modes of operation (MO-1, MO-2, MO-3, MO-4) comprise a first, preferably highest-ranking, mode of operation (MO-1), wherein the power output from the one or more DC / DC converters (Conv, Convl , Conv2) is controlled in such a way that the share of the total power delivered from the hybrid battery pack (HPB), which is delivered by the high-energy assembly (HE), is dynamically reduced if the temperature (THE) of the high-energy assembly (HE) is higher than the temperature (THP) of the high-power assembly (HP), and dynamically increased if the temperature (THE) of the high-energy assembly (HE) is lower than the temperature (THP) of the high-power assembly (HP).

[0108] 4. The energy management system according to item 3, wherein the first control criterion (CC-1) associated with the first mode of operation (MO-1) is that the temperature difference (|THE - THP|) between the high-energy assembly (HE) and the high-power assembly (HP) has been above a predefined temperature difference threshold (Tset) for a period of time (t™), which is longer than a first predefined continuous period of time (t-TH.set).

[0109] 5. The energy management system according to item 4, wherein the temperature difference is defined as the difference between the highest temperature (THE) measured within the high-energy assembly (HE) and the highest temperature (THP) measured within the high-power assembly (HP). 6. The energy management system according to item 4 or 5, wherein the predefined temperature difference threshold (Tset) is between 5° C and 20° C, preferably between 8° C and 15° C, such as 10° C.

[0110] 7. The energy management system according to any of items 4-6, wherein the first predefined continuous period of time (tth.set) is between 2 minutes and 15 minutes, preferably between 3 minutes and 10 minutes, such as 5 minutes.

[0111] 8. The energy management system according to any of items 4-7, wherein, if the first control criterion (CC-1) is still fulfilled when the energy management system has operated in the first mode of operation (MO-1) for a second predefined continuous period of time, the energy management system is configured to take action to cause the operation of the load, which is powered by the hybrid battery pack (HPB), to be discontinued.

[0112] 9. The energy management system according to item 8, wherein the second predefined continuous period of time is between 10 minutes and 30 minutes, preferably between 15 minutes and 25 minutes, such as 20 minutes.

[0113] 10. The energy management system according to any of the preceding items, wherein the two or more modes of operation (MO-1 , MO-2, MO-3, MO-4) further comprise a second mode of operation (MO-2), wherein the power output from the one or more DC / DC converters (Conv, Convl , Conv2) is controlled in such a way that the level of energy (EHE) stored in the high-energy assembly (HE) is kept at a dynamically set level (E*HE).

[0114] 11. The energy management system according to item 10, wherein the set level (E*HE) is defined by the equation wherein Enet is the total amount of stored energy in the hybrid battery pack (HBP), PHE, max is the maximum power, which can be delivered by the high-energy assembly (HE), and PHP, max is the maximum power, which can be delivered by the high-power assembly (HP). 12. The energy management system according to item 10 or 11, wherein the second control criterion (CC-2) associated with the second mode of operation (MO- 2) is that the state-of-charge (SOCHBP) of the complete hybrid battery pack (HPB) is less than a first predefined state-of-charge threshold value (SOCHBP, min) .

[0115] 13. The energy management system according to item 12, wherein the first predefined state-of-charge threshold value (SOCHBP, min) is between 15 % and 35 % of full charge, preferably between 20 % and 30 % of full charge, such as 25 % of full charge.

[0116] 14. The energy management system according to any of the preceding items, wherein the two or more modes of operation (MO-1 , MO-2, MO-3, MO-4) further comprise a third mode of operation (MO-3), wherein the power output from the one or more DC / DC converters (Conv, Convl , Conv2) is controlled in such a way that the level of energy (EHP) stored in the high-power assembly (HP) is reduced to a minimum level (E*HP).

[0117] 15. The energy management system according to item 14, wherein the third control criterion (CC-3) associated with the third mode of operation (MO-3) is that the state-of-charge (SOCHBP) of the complete hybrid battery pack (HPB) is higher than a second predefined state-of-charge threshold value, and that the state-of-charge (SOCHP) of the high-power assembly (HP) is lower than a third predefined state-of-charge threshold value (SOCHP, min) , wherein the third predefined state-of-charge threshold value (SOCHP, min) is lower than the second predefined state-of-charge threshold value.

[0118] 16. The energy management system according to item 15, wherein the second predefined state-of-charge threshold value is between 15 % and 35 % of full charge, preferably between 20 % and 30 % of full charge, such as 25 % of full charge.

[0119] 17. The energy management system according to item 12 or 13 and to item 15 or 16, wherein the first predefined state-of-charge threshold value (SOCHBP, min) and the second predefined state-of-charge threshold value are identical. 18. The energy management system according to any of items 15-17, wherein the third predefined state-of-charge threshold value (SOCHP, min) is between 10 % and 30 % of full charge, preferably between 15 % and 25 % of full charge, such as 20 % of full charge.

[0120] 19. The energy management system according to any of the preceding items, wherein the two or more modes of operation further comprise a fourth mode of operation, wherein the share (%PHE) of the total power delivered from the hybrid battery pack, which is delivered by the high-energy assembly, is computed by the equation wherein RLILHE is the remaining useful life of the high-energy assembly (HE), RLILHP is the remaining useful life of the high-power assembly (HP), Emax, HE is the maximum stored energy capability of the high-energy assembly (HE), Emax, HP is the maximum stored energy capability of the high-power assembly (HP), SOHHE is the state of health of the high-energy assembly (HE), and SOHHP is the state of health of the high-power assembly (HP).

[0121] 20. The energy management system according to item 19, wherein the fourth mode of operation (MO-4) is the lowest-most ranking of the two or more modes of operation (MO-1, MO-2, MO-3, MO-4), and wherein the fourth control criterion associated with the fourth mode of operation (MO-4) is that none of the control criteria (CC-1 , CC-2, CC-3) associated with any higher ranking modes of operation (MO-1 , MO-2, MO-3) are fulfilled.

[0122] 21. A hybrid battery pack (HPB) comprising a high-energy assembly (HE) and a high-power assembly (HP), wherein the high-energy assembly (HE) comprises one or more high-energy battery cells, which are internally connected in parallel and / or in series, and the high-power assembly (HP) comprises one or more high-power battery cells, which are internally connected in parallel and / or in series, wherein the high-energy assembly (HE) and the high-power assembly (HP) are connected through one or more DC / DC converters (Conv, Convl , Conv2) to one another and / or to a DC bus supplying power to a load, and wherein the operation of the hybrid battery pack (HPB) is controlled by an energy management system according to any of the preceding items.

[0123] 22. The hybrid battery pack (HPB) according to item 21, wherein the hybrid battery pack (HPB) is configured to supply power to an inverter (Inv) and a motor (M) of an electric vehicle.

[0124] 23. An electric vehicle comprising a hybrid battery pack (HPB) according to item 22.

Claims

Claims1. An energy management system for a hybrid battery pack (HPB) comprising a high-energy assembly (HE) and a high-power assembly (HP), wherein the high-energy assembly (HE) comprises one or more high-energy battery cells, which are internally connected in parallel and / or in series, and the high-power assembly (HP) comprises one or more high-power battery cells, which are internally connected in parallel and / or in series, wherein the high-energy assembly (HE) and the high-power assembly (HP) are connected through one or more DC / DC converters (Conv, Convl , Conv2) to one another and / or to a DC bus supplying power to a load, such as an inverter (Inv) and a motor (M) of an electric vehicle, wherein the energy management system is configured to decide, by controlling the power output from the one or more DC / DC converters (Conv, Convl, Conv2), how large a share of the total power delivered from the hybrid battery pack (HPB) is delivered by the high-energy assembly (HE) and by the high-power assembly (HP), respectively, wherein the energy management system is configured to switch between two or more modes of operation (MO-1, MO-2, MO-3, MO-4) depending on the present state-of-charge and temperatures (THE, THP) of the high-energy assembly (HE) and / or the high-power assembly (HP), wherein a specific control criterion (CC-1 , CC-2, CC-3) is associated with each of the two or more modes of operation (MO-1, MO-2, MO-3, MO-4), wherein the two or more modes of operation (MO-1 , MO-2, MO-3, MO-4) are ranked in a hierarchy of priority depending on the importance of their respective associated control criteria (CC-1 , CC-2, CC-3), andwherein the energy management system is arranged to operate in the highest ranking mode of operation (MO-1 , MO-2, MO-3, MO-4), for which the associated control criterion (CC-1 , CC-2, CC-3) is fulfilled.

2. The energy management system according to claim 1 , wherein the two or more modes of operation (MO-1 , MO-2, MO-3, MO-4) comprise a first, preferably highest-ranking, mode of operation (MO-1), wherein the power output from the one or more DC / DC converters (Conv, Convl , Conv2) is controlled in such a way that the share of the total power delivered from the hybrid battery pack (HPB), which is delivered by the high-energy assembly (HE), is dynamically reduced if the temperature (THE) of the high-energy assembly (HE) is higher than the temperature (THP) of the high-power assembly (HP), and dynamically increased if the temperature (THE) of the high-energy assembly (HE) is lower than the temperature (THP) of the high-power assembly (HP).

3. The energy management system according to claim 2, wherein the first control criterion (CC-1) associated with the first mode of operation (MO-1) is that the temperature difference (|THE - THP|) between the high-energy assembly (HE) and the high-power assembly (HP) has been above a predefined temperature difference threshold (Tset) for a period of time (t™), which is longer than a first predefined continuous period of time (t-TH.set), and wherein the predefined temperature difference threshold (Tset) is preferably between 5° C and 20° C, most preferred between 8° C and 15° C, such as 10° C.

4. The energy management system according to 3, wherein the first predefined continuous period of time (tth.set) is between 2 minutes and 15 minutes, preferably between 3 minutes and 10 minutes, such as 5 minutes.

5. The energy management system according to claim 3 or 4, wherein, if the first control criterion (CC-1) is still fulfilled when the energy management system has operated in the first mode of operation (MO-1) for a second predefined continuous period of time, the energy management system is configured to take action to cause the operation of the load, which is powered by the hybrid battery pack (HPB), to be discontinued, andwherein the second predefined continuous period of time is preferably between 10 minutes and 30 minutes, most preferred between 15 minutes and 25 minutes, such as 20 minutes.

6. The energy management system according to any of the preceding claims, wherein the two or more modes of operation (MO-1 , MO-2, MO-3, MO-4) further comprise a second mode of operation (MO-2), wherein the power output from the one or more DC / DC converters (Conv, Convl , Conv2) is controlled in such a way that the level of energy (EHE) stored in the high-energy assembly (HE) is kept at a dynamically set level (E*HE), and wherein the set level (E*HE) is defined by the equationwherein Enet is the total amount of stored energy in the hybrid battery pack (HBP), PHE, max is the maximum power, which can be delivered by the high-energy assembly (HE), and PHP, max is the maximum power, which can be delivered by the high-power assembly (HP).

7. The energy management system according to claim 6, wherein the second control criterion (CC-2) associated with the second mode of operation (MO-2) is that the state-of-charge (SOCHBP) of the complete hybrid battery pack (HPB) is less than a first predefined state-of-charge threshold value (SOCHBP, min) , and wherein the first predefined state-of-charge threshold value (SOCHBP, min) is preferably between 15 % and 35 % of full charge, most preferred between 20 % and 30 % of full charge, such as 25 % of full charge.

8. The energy management system according to any of the preceding claims, wherein the two or more modes of operation (MO-1 , MO-2, MO-3, MO-4) further comprise a third mode of operation (MO-3), wherein the power output from the one or more DC / DC converters (Conv, Convl , Conv2) is controlled in such a way that the level of energy (EHP) stored in the high-power assembly (HP) is reduced to a minimum level (E*HP).

9. The energy management system according to claim 8, wherein the third control criterion (CC-3) associated with the third mode of operation (MO-3) is that the state-of-charge (SOCHP) of the complete hybrid battery pack (HPB) is higher than a second predefined state-of-charge threshold value, and that the state-of- charge (SOCHP) of the high-power assembly (HP) is lower than a third predefined state-of-charge threshold value (SOCHP, min) , wherein the third predefined state-of- charge threshold value (SOCHP, min) is lower than the second predefined state-of- charge threshold value, wherein the second predefined state-of-charge threshold value is preferably between 15 % and 35 % of full charge, most preferred between 20 % and 30 % of full charge, such as 25 % of full charge, and / or wherein the third predefined state-of-charge threshold value (SOCHP, min) is preferably between 10 % and 30 % of full charge, most preferred between 15 % and 25 % of full charge, such as 20 % of full charge.

10. The energy management system according to claim 7 and to claim 9, wherein the first predefined state-of-charge threshold value (SOCHBP, min) and the second predefined state-of-charge threshold value are identical.

11. The energy management system according to any of the preceding claims, wherein the two or more modes of operation further comprise a fourth mode of operation, wherein the share (%PHE) of the total power delivered from the hybrid battery pack, which is delivered by the high-energy assembly, is computed by the equationwherein RLILHE is the remaining useful life of the high-energy assembly (HE), RLILHP is the remaining useful life of the high-power assembly (HP), Emax, HE is the maximum stored energy capability of the high-energy assembly (HE), Emax, HP is the maximum stored energy capability of the high-power assembly (HP), SOHHE is the state of health of the high-energy assembly (HE), and SOHHP is the state of health of the high-power assembly (HP).

12. The energy management system according to claim 11 , wherein the fourth mode of operation (MO-4) is the lowest-most ranking of the two or more modes of operation (MO-1, MO-2, MO-3, MO-4), and wherein the fourth control criterion associated with the fourth mode of operation (MO-4) is that none of the control criteria (CC-1 , CC-2, CC-3) associated with any higher ranking modes of operation (MO-1 , MO-2, MO-3) are fulfilled.

13. A hybrid battery pack (HPB) comprising a high-energy assembly (HE) and a high-power assembly (HP), wherein the high-energy assembly (HE) comprises one or more high-energy battery cells, which are internally connected in parallel and / or in series, and the high-power assembly (HP) comprises one or more high-power battery cells, which are internally connected in parallel and / or in series, wherein the high-energy assembly (HE) and the high-power assembly (HP) are connected through one or more DC / DC converters (Conv, Convl , Conv2) to one another and / or to a DC bus supplying power to a load, and wherein the operation of the hybrid battery pack (HPB) is controlled by an energy management system according to any of the preceding claims.

14. The hybrid battery pack (HPB) according to claim 13, wherein the hybrid battery pack (HPB) is configured to supply power to an inverter (Inv) and a motor (M) of an electric vehicle.

15. An electric vehicle comprising a hybrid battery pack (HPB) according to claim

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