Background of the invention

The invention relates to a battery arrangement for producing direct current.

Various battery arrangements are used typically for producing emergency power inter alia for targets classified as critical, whose operation must not be disturbed by power failures in the operation of the primary power supply which, typically, is an electric power network. In addition, under developing country conditions, battery arrangements may be used for producing emergency power also for targets that are classified as less critical if the full- time operation of the primary electric power source on the whole or the capacity for producing instantaneously required peak powers is uncertain.

Brief description of the invention

An object of the invention is to provide a novel battery arrangement. The solution according to the invention is characterized by what is disclosed in the independent claim.

The battery arrangement for producing direct current comprises at least one alternating current input for connecting the battery arrangement to at least one alternating current source comprising at least one phase. The battery arrangement further comprises at least one rectifier unit to be connected to the alternating current input for converting alternating current into direct current, the rectifier unit comprising at least one alternating current input and at least one direct current output. The battery arrangement further comprises at least one rechargeable battery unit connectable to at least one direct current output of the rectifier unit for charging the battery unit with direct current produced by the rectifier unit, and a protection unit connected to each phase of the alternating current input.

An advantage of the solution is that properties or quantities describing the electric energy or electric power produced by the alternating current source may be examined phase-specifically, enabling only defectively operating or faulty phases to be disconnected from the rectifier unit and normally operating phases to be kept connected to the rectifier unit. This differs from the previously generally known solutions, wherein all phases being used are viewed together and the alternating current source is deactivated even in case of failure of one phase only. In the present solution, it is for instance possible to produce charging energy for the battery units as long as even one phase of the alternating current source is operable. The solution is particularly well suited to developing country conditions where breakdowns in electric power production and distribution are common but where, on the other hand, no significant atten- tion is necessarily paid to the symmetry of the load on the different phases of the electric power network.

Some embodiments of the invention are disclosed in the dependent claims.

Brief description of the figures

The invention is now described in closer detail in connection with preferred embodiments and with reference to the accompanying drawings, in which

Figure 1 schematically shows a battery arrangement for producing direct current,

Figure 2 schematically shows an embodiment of the battery arrangement according to Figure 1 , and

Figure 3 schematically shows the battery arrangement according to Figure 1 at a component level and divided into modules.

For the sake of clarity, the figures show some embodiments of the invention in a simplified manner. In the figures, like reference numerals identify like elements.

Detailed description of the invention

Figure 1 schematically shows an battery arrangement 1 for producing direct current power, i.e. direct current and voltage. The battery arrange- ment 1 comprises a rectifier unit ACDC, which converts alternating current supplied to the rectifier unit ACDC into direct current. The general structure and operation principle of various rectifiers are known per se to those skilled in the art, so they will not be discussed in any further detail herein.

The rectifier unit ACDC is provided with at least one alternating cur- rent input 2 connectable to at least one alternating current power source producing alternating current and voltage which, hereinbelow, may also be called an alternating current source. Figure 1 schematically shows a total of four alternating current sources ACS1 , ACS2, ACS3 and ACS4 that are separate from one another and connectable to the rectifier unit ACDC via a switch S1 , S2, S3 and S4 associated with each alternating current source. Said alternat- ing current sources may include for instance a normal electric power distribution network, a fuel-powered generator, a wind power plant comprising at least one wind turbine, or a solar power plant comprising at least one solar cell. Below in the description, the alternating current source ACS1 refers to a normal electric power distribution network, the alternating current source ACS2 to a fuel-powered generator, the alternating current source ACS3 to a wind power plant, and the alternating current source ACS4 to a solar power plant.

Between each alternating current source ACS1 , ACS2, ACS3 and ACS4 and a corresponding switch S1 , S2, S3 and S4 is connected a protection unit PU1 , PU2, PU3, PU4. Each protection unit PU1 , PU2, PU3, PU4 and the corresponding switch S1 , S2, S3 and S4 associated therewith form at least one alternating current input ACIN of the battery arrangement 1 , the battery arrangement 1 shown in Figure 1 thus comprising a total of four alternating current inputs ACIN. The protection unit PU1 , PU2, PU3, PU4 comprises measur- ing means, such as instrument transformers, which, for the sake of clarity, are not shown in the figures, or they are connected to said measuring means for determining values of at least one electrical quantity, such as current, voltage and frequency, describing the electric energy supplied by the alternating current source ACS1 , ACS2, ACS3 and ACS4. Said measuring means are obvi- ous per se to those skilled in the art. Further, the protection unit PU1 , PU2, PU3, PU4 is configured to compare said values with limit values set for the electrical quantities in question. If the value of at least one electrical quantity describing the electric energy supplied by the alternating current source ACS1 , ACS2, ACS3 and ACS4 deviates from the limit values set therefor in advance, the protection unit PU1 , PU2, PU3, PU4 is configured to control via a control line PU1_S1 , PU2_S2, PU3_S3, PU4_S4 a corresponding switch S1 , S2, S3, S4 to open so as to prevent the electric energy supplied from the corresponding alternating current source ACS1 , ACS2, ACS3 and ACS4 from being supplied to the rectifier unit ACDC. The operation of the protection units PU1 , PU2, PU3, PU4 will be discussed in closer detail below.

The rectifier unit ACDC is further provided with at least one direct current output 3, which is connectable via a switch S5 to at least one direct current load DCL1 , DCL2 and DCL3. Said direct current loads may include for instance a medical device, a mobile telephone network base station, or an in- verier unit, which converts direct current into alternating current for alternating current loads. The general structure and operation principle of various inverters are known per se to those skilled in the art, so they will not be discussed in any further detail herein.

With each direct current load DCL1 , DCL2 and DCL3 is associated a corresponding switch S6, S7 and S8 via which each direct current load DCL1 , DCL2 and DCL3 is individually separable from the direct current output 3 of the rectifier unit ACDC or from direct current outputs 4 of battery units AU1 , AU2, AUn to be discussed next. Each switch S6, S7 and S8 and a branch of a circuit connected thereto form one direct current output DCOUT of the battery arrangement 1 , the system shown in Figure 1 thus comprising a to- tal of three direct current outputs DCOUT.

The battery arrangement 1 further comprises one or more battery units AU1 , AU2, AUn mutually coupled in parallel, in Figure 1 n battery units. One or more battery units are connectable to at least one direct current load DCL1 , DCL2 and DCL3 to be in parallel with the rectifier unit ACDC via corresponding switches SAU1 , SAU2, SAUn associated with the battery units AU1 , AU2, AUn and their direct current outputs 4 and the switches S6, S7 and S8 associated with the direct current loads DCL1 , DCL2 and DCL3. One battery unit AU1 , AU2, AUn may comprise one battery or, alternatively, more interconnected batteries. The battery units AU1 , AU2, AUn may comprise lithium-ion batteries, for instance.

The battery units AU1 , AU2, AUn may be recharged via a charging circuit CC connectable via a switch S9 to the direct current output 3 of the rectifier unit ACDC. With each battery unit AU1 , AU2, AUn is associated a charging unit CHU known per se to those skilled in the art, which is inde- pendently responsible for charging the battery or batteries of the battery unit AU1 , AU2, AUn when the charging circuit CC is connected by the switch S9 to the direct current output 3 of the rectifier unit ACDC and when the alternating current input 2 of the rectifier unit ACDC is connected to at least one operating alternating current source ACS1 , ACS2, ACS3, ACS4. Said charging unit CHU may also be shared by two or more battery units. When the battery unit AU1 , AU2, AUn is being charged, in an output 4 of the battery unit AU1 , AU2, AUn the corresponding switch SAU1 , SAU2, SAUn is controlled to be open.

The battery arrangement 1 further includes a control unit CU to en- able inter alia the operation and/or state information of both parts, components and/or devices belonging to the battery arrangement 1 itself and of parts, com- ponents and/or devices associated with the battery arrangement 1 to be controlled and monitored.

The control unit CU is connected via a signal bus CU_PU to each protection unit PU1 , PU2, PU3, and PU4. This enables the control unit CU to follow the operation of said protection units PU1 , PU2, PU3, and PU4 and register the protection procedures implemented by the protection units PU1 , PU2, PU3, and PU4. Via said signal bus CU_PU the control unit CU may also influence the set values of the protection settings of the protection unit PU1 , PU2, PU3 and PU4, i.e. for instance the limit values of current, voltage or frequency that for each electrical quantity limit the value range acceptable therefor, the electric power or electric energy produced by the alternating current source ACS1 , ACS2, ACS3, ACS4 corresponding to the value range being accepted to be supplied to the rectifier unit ACDC. Further, the control unit CU may via said signal bus CU_PU determine the amount and quality properties of electric power or electric energy received from each alternating current source ACS1 , ACS2, ACS3, ACS4 on the basis of measurement of the aforementioned at least one electrical quantity, such as voltage, current or frequency, for instance, if the protection unit PU1 , PU2, PU3, and PU4 has such current, voltage or frequency measuring means available for use that are equipped with a connection for outputting measurement information from the measuring means.

Further, the control unit CU is connected via a signal bus CU_SAC to each alternating current source ACS1 , ACS2, ACS3, ACS4 and to the switch S1 , S2, S3 and S4 associated with the protection unit PU1 , PU2, PU3, and PU4 corresponding thereto, in which case the control unit CU may directly control the operation of said switches S1 , S2, S3, S4, i.e. opening and closing of the switches S1 , S2, S3 and S4. The control unit CU may thus either connect each alternating current source ACS1 , ACS2, ACS3, ACS4 to the alternating current input 2 of the rectifier unit ACDC or disconnect it therefrom by controlling the corresponding switch S1 , S2, S3, S4 to be either closed or open.

Further, the control unit CU is connected via a signal bus CU_ACDC to the rectifier unit ACDC, in which case the control unit CU may via said signal bus CU_ACDC control the operation of the rectifier unit ACDC for instance by changing the set values influencing the operation of the rectifier unit ACDC, or receive from the rectifier unit ACDC for instance state information describing the operating state of the rectifier unit ACDC.

Further, the control unit CU is connected via a signal bus CU_CC to a switch S9 in the charging circuit CC, in which case the control unit CU may either control said switch S9 to be connected to the direct current output 3 of the rectifier unit ACDC for supplying charging current to the battery units AU1 , AU2, AUn, or control said switch S9 to be open to prevent charging current from being supplied to the battery units AU1 , AU2, AUn. When the switch S9 is closed for supplying charging current to the battery units AU1 , AU2, AUn, the charging unit CHU associated with each battery unit AU1 , AU2, AUn may, however, prevent a corresponding battery unit AU1 , AU2, AUn from being charged, either independently or controlled by the control unit CU.

Further, the control unit CU is connected via a signal bus CU_AU to each battery unit AU1 , AU2, AUn, in which case the control unit CU may receive from each battery unit AU1 , AU2, AUn state information describing for instance the operating state of the battery unit AU1 , AU2, AUn in question. The battery unit AU1 , AU2, AUn has an integral battery management system (BMS) which monitors the operating state of the battery unit AU1 , AU2, AUn and transmits the state information describing said operating states to the control unit CU. Further, the control unit CU may via said signal bus CU_AU control separately a charging unit associated with each battery unit.

Further, the control unit CU is connected via a signal bus CU_SAU to a switch SAU1 , SAU2, SAUn associated with each battery unit AU1 , AU2, AUn. In such a case, the control unit CU may, for instance on the ba- sis of the aforementioned state information describing the operating state of the battery unit AU1 , AU2, AUn, either control the switch SAU1 , SAU2, SAUn to be closed for connecting the corresponding battery unit AU1 , AU2, AUn to the direct current output DCOUT of the battery arrangement 1 , or control the switch SAU1 , SAU2, SAUn to be open for disconnecting the battery unit AU1 , AU2, AUn from the direct current output DCOUT of the battery arrangement 1 . When the battery unit AU1 , AU2, AUn is being charged, the corresponding switch SAU1 , SAU2, SAUn is controlled to be open.

Further, the control unit CU is connected via said signal bus CU_SAU also to the switch S5 in the direct current output 3 of the rectifier unit ACDC, in which case the control unit CU may control the switch S5 to be closed for connecting the direct current output 3 of the rectifier unit ACDC to the direct current output DCOUT of the battery arrangement 1 , or control the switch S5 to be open to disconnect the direct current output 3 of the rectifier unit ACDC from the direct current output DCOUT of the battery arrangement 1 .

Further, the control unit CU is connected via a signal bus CU_SDC to the switch S6, S7 and S8 associated with each direct current load DCL1 , DCL2 and DCL3, in which case the control unit CU may control each switch S6, S7, S8 to be closed separately from one another for connecting the direct current load DCL1 , DCL2 and DCL3 associated with the switch S6, S7, S8 in question to the direct current outputs 3, 4 from the rectifier unit ACDC and/or the battery units AU1 , AU2, AUn, or control each switch S6, S7, S8 to be open separately from one another for disconnecting the direct current load DCL1 , DCL2 and DCL3 associated with the switch S6, S7, S8 in question from the direct current outputs 3, 4 from the rectifier unit ACDC and/or the battery units AU1 . AU2, AUn.

The aforementioned signal buses CU_PU, CU_SAC, CU_ACDC,

CU_CC, CU_SAU, CU_AU and CU_SDC may be implemented for instance by means of an internal virtual private network VPN (Figure 3) of the battery arrangement 1 .

Further, it is possible to connect via a communication line CL at least one monitoring unit MU external to the battery system 1 to the battery arrangement 1 and to its control unit CU in particular. The monitoring unit MU may receive from the control unit CU the aforementioned information describing the operation of the battery arrangement 1 , the alternating current sources ACS1 , ACS2, ACS3, ACS4 or the direct current loads DCL1 , DCL2, DCL3. Further, the monitoring unit MU may send the control unit CU information on the basis of which the control unit CU may influence the operation of the rectifier unit ACDC and the battery units AU1 , AU2, AUn as well as the connecting of the alternating current sources ACS1 , ACS2, ACS3, ACS4 and/or the direct current loads DCL1 , DCL2, DCL3 to the battery arrangement 1 . Said in- formation may include for instance a prediction for the amount and/or power and/or cost of electric energy obtainable within a time period of a given length from each available alternating current source. Said information may also be for instance the mutual priority levels of the direct current loads DCL1 , DCL2 and DCL3, i.e. the order of importance of said loads for situations where no electric energy can be supplied to all the loads DCL1 , DCL2 and DCL3 from one or more alternating current sources and/or battery units when the amount or power of the available electric energy is insufficient for all the loads DCL1 , DCL2 and DCL3.

One or more monitoring units MU may be physically located for instance on the premises of the possessor of the battery arrangement 1 and/or on the premises of the supplier of the battery arrangement 1 , in which case necessary control, error diagnostic, system update or maintenance procedures may be carried out remotely.

Figure 2 is a schematic view of an battery arrangement 1 according to Figure 2, which relates to the protection of the rectifier unit ACDC and the battery unit AU1 , AU2, AUn behind it from the disturbance present in the electric energy or electric power produced by the alternating current source, such as overvoltage, overcurrent, or excessive frequency variation. For reasons of clarity, Figure 2 only shows one alternating current source ACS1 , which has three phases A, B, C, that is, phase outputs A, B, C which may be connected to the alternating current input 2 of the rectifier unit ACDC. The other alternating current sources ACS2, ACS3, ACS4 may be similar, or alternatively they may only have one or two phases, that is, phase outputs. In the following, the operation will be examined with reference to the alternating current source ACS1 , but it is similar with regard to the alternating current sources ACS2, ACS3, and ACS4.

As described in Figure 1 , the embodiment of Figure 2 similarly comprises a rectifier unit ACDC, one or more battery units AU1 , AU2, AUn, and a control unit CU. In addition, Figure 2 shows similarly to Figure 1 a monitoring unit MU as well as switches S6, S7, S8 on the direct current output DCOUT of the battery unit 1 .

The embodiment according to Figure 2 further includes a phase- specific protection unit PU1_A, PU1_B, PU1_C connected to each phase A, B, C running from the alternating current input ACIN of the battery arrangement 1 to the rectifier unit ACDC, and together forming a protection unit PU1 connect- ed to the alternating current source ACS1 . Each protection unit PU1_A, PU1_B, PU1_C may be a separate device or they may formed as separate devices and/or functions in one device forming the protection unit PU1 . The control unit CU is connected to each protection unit PU1_A, PU1_B, PU1_C through a signal bus CU_PU.

Each protection unit PU1_A, PU1_B, PU1_C is connected to a phase-specific switch S1_A, S1_B, S1_C connected to the corresponding phase via the corresponding control line PU1_AS1 , PU1_BS1 , PU1_CS1 , whereby the protection unit PU1_A, PU1_B, PU1_C may control the corresponding switch S1_A, S1_B, S1_C to open or close. The control unit CU, too, is connected via the signal bus CU_SAC to each switch S1_A, S1_B, S1_C, whereby the control unit CU may also control said switch S1_A, S1_B, S1_C to open or close.

The protection unit PU1_A, PU1_B, PU1_C is configured to determine a value of at least one electrical quantity representing the electric energy supplied by the alternating current source ACS1 , ACS2, ACS3, ACS4 on at least one phase by means of measuring equipment, such as instrument transformers, connected to it. Said electrical quantities may be phase voltage U, phase current I, and frequency f, for example. Further, the protection unit PU1_A, PU1_B, PU1_C is configured to compare said values with limit values set for the electrical quantities in question. If the value of at least one electrical quantity U, I, f does not meet the condition according to at least one limit value Uset, Iset, fset set for said quantity U, I, f on said protection unit PU1_A, PU1_B, PU1_C on said phase A, B, C, the protection unit PU1_A, PU1_B, PU1_C is configured to control the corresponding switch S1_A, S1_B, S1_C to open in order to disconnect said phase of the alternating current source ACS1 from the rectifier unit ACDC. In such a case, it will no longer be possible to supply electric energy to the rectifier unit ACDC from said phase A, B, C of the alternating current source ACS1 .

An advantage of the described embodiment is that the properties or quantities describing the electric energy or electric power produced by the al- ternating current source ACS1 may be examined phase-specifically, and only defectively operating or faulty phases may be disconnected from the rectifier unit ACDC and keep the normally operating phases still connected to the rectifier unit ACDC. This differs from the previously generally known solutions wherein all phases being used are viewed together and the alternating current source is deactivated when even one phase fails or its operation deviates from the normal. In the presently disclosed solution, it is for instance possible to produce charging energy for the battery units AU1 , AU2, AUn as long as even one phase is operational. The solution is particularly well suited for developing country conditions where breakdowns in electric power production and distribution are common but where, on the other hand, no significant atten- tion is necessarily paid to the symmetry of the load on the different phases of the electric power network.

The limit values of protection, that is, the set values U _se t, Ut, fset defined in the protection units PU1_A, PU1_B, PU1_C may be fixed. Alternative- ly, the limit values of protection U _se t, Ut, fset set for the protection units may be set freely. The control unit CU is connected via the signal bus CU_PU to the protection units PU1_A, PU1_B, PU1_C, whereby the limit values defined in the protection units PU1_A, PU1_B, PU1_C may be changed via the control unit CU. The control unit CU may also register the protection measures taken by the protection units PU1_A, PU1_B, PU1_C and store the values of the electrical quantities relating to being below/exceeding the limit values of protection for later examination.

The set limit of the protection of the protection unit PU1_A, PU1_B, PU1_C may be one value that said electrical quantity must not exceed or be below. Advantageously, the limit value U _se t, Ut, fset of the protection of the protection unit PU1_A, PU1_B, PU1_C comprises a settable lower limit value

Usetmin, Isetmin. fsetmin and Upper limit Value Usetmax, Utmax, fsetmax. In SUCh a Case, the protection unit PU1_A, PU1_B, PU1_C is configured to disconnect at least one phase A, B, C of the alternating current source ACS1 from the rectifier unit ACDC when the value of at least one electrical quantity U, I, f representing the electric energy supplied by the alternating current source ACS1 is in a value range outside of said lower limit values U _se tmin, Isetmin, fsetmin and upper limit values Usetmax, Utmax, fsetmax.

The set value of the protection of the protection unit PU1_A, PU1_B, PU1_C may also include at least one settable delay setting D. The delay setting D may be used, for example, in situations where the closing of the switch S1_A, S1_B, S1_C between the alternating current source ACS1 and the rectifier unit ACDC is prevented until the operating of the alternating current source ASC1 has reached a balanced state either due to a restart or a fault that has cleared. In such a case, it is possible to prevent voltage or current surges from reaching the rectifier unit ACDC.

The monitoring unit MU is connected to the control unit via a communication link CL. The monitoring unit MU may convey information to the control unit CU on, for example, the most cost-efficient alternating current source available at the moment in question. In such a case, the control unit CU may, by opening and closing switches S1 , S2, S3, S4, disconnect expensive alter- nating current sources from the alternating current input ACIN of the battery arrangement 1 and connect more economical alternating current sources to the alternating current input ACIN of the battery arrangement 1 . In such a case, wind and solar energy, for example, may be used whenever they are available, and at other times energy available from the normal electricity distribution network. A fuel-operated generator will only be used when other energy sources are unavailable.

The control unit CU may further be configured to store the value information of at least one electrical quantity U, I, f representing the electric en- ergy supplied by at least one alternating current source ACS1 , ACS2, ACS3, ACS4, and/or determine information derived from them, such as the amount or power of the electric energy taken from each of the alternating current sources during a particular time period or instantaneously. Furthermore, the control unit CU may be configured to forward said information to the monitoring unit MU.

Referring anew to Figure 1 , the battery arrangement 1 shown in

Figure 1 for producing alternating current thus comprises a rectifier unit ACDC for converting alternating current to direct current. The rectifier unit ACDC comprises at least one alternating current input 2, which may be connected to at least one alternating current input ACIN of the battery arrangement 1 in or- der to connect the battery arrangement 1 to at least one alternating current source ACS1 , ACS2, ACS3, ACS4. The rectifier unit ACDC further comprises at least one alternating current output 3, which may be connected to at least one direct current output DCOUT in order to connect the battery arrangement 1 to at least one direct current load DCL1 , DCL2, DCL3.

The battery arrangement 1 further comprises at least one battery unit, but advantageously two or more battery units AU1 , AU2, AUn, which may be connected mutually in parallel to at least one direct current output DCOUT of the battery arrangement 1 in order to produce direct current on at least one direct current output DCOUT of the battery arrangement 1 . In addi- tion, said battery units AU1 , AU2, AUn may be connected in parallel with the rectifier unit ACDC to the direct current output DCOUT of the battery arrangement 1 . In addition, said battery units AU1 , AU2, AUn may be connected to the direct current output 3 of the rectifier unit ACDC to charge the battery units AU1 , AU2, AUn with the direct current produced by the rectifi- er unit ACDC. According to an embodiment, the battery arrangement 1 for producing direct current comprises at least one alternating current input ACIN to connect the battery arrangement 1 to at least one alternating current source ACS1 , ACS2, ACS3, ACS4, at least one direct current output DCOUT to con- nect the battery arrangement 1 to at least one direct current load DCL1 , DCL2, DCL3, at least one rectifier unit ACDC to be connected to the alternating current input ACIN for converting alternating current to direct current, which rectifier unit ACDC comprises at least one alternating current input 2 and at least one direct current output 3 and at least one chargeable battery unit AU1 , AU2, AUn, which battery unit AU1 , AU2, AUn may be connected to at least one direct current output 3 of the rectifier unit ACDC to charge the battery unit AU1 , AU2, AUn with the direct current produced by the rectifier unit ACDC, and which battery unit AU1 , AU2, AUn may be connected in parallel with the rectifier unit ACDC to at least one direct current output DCOUT of the bat- tery arrangement 1 to produce direct current on at least one direct current output DCOUT of the battery arrangement 1 .

So, the rectifier unit ACDC may be connected, depending on the usage situation at any one time, to either charge the battery units AU1 , AU2, AUn or only to supply direct current to at least one direct current output DCOUT of the battery arrangement 1 , or both to charge the battery units AU1 , AU2, AUn and supply direct current to at least one direct current output DCOUT of the battery arrangement 1 . The control unit CU controls, via signal buses CU_CC and CU_SAU, the position of the switches S5 and S9 to supply direct current produced by the rectifier unit ACDC to a charging circuit CC and/or the direct current output DCOUT of the battery arrangement 1 .

According to an embodiment, the rectifier unit ACDC is connected to the direct current output DCOUT of the battery arrangement 1 , and at least one battery unit AU1 , AU2, AUn is also connected to the direct current output DCOUT of the battery arrangement 1 in parallel with the rectifier unit ACDC. In such as case, the direct current used by the direct current load DCL1 , DCL2, DCL3 is supplied from at least one alternating current source ACS1 , ACS2, ACS3, ACS4 via the rectifier unit ACDC, and the at least one battery unit AU1 , AU2, AUn in parallel with the rectifier unit forms a back-up power source, which may immediately supply the direct current load, if said alternating current source ACS1 , ACS2, ACS3, ACS4 can no longer supply power to the battery arrangement 1 , or the need arises to disconnect it from the battery arrangement 1 .

Each battery unit AU1 , AU2, AUn comprises an associated internal management system BMS, configured to form status information AU _s tat representing the operating mode of the battery unit AU1 , AU2, AUn in question. The operating modes of the battery unit are the battery unit AU1 , AU2, AUn being in use, whereby the switch SAU1 , SAU2, SAUn associated with the battery unit AU1 , AU2, AUn is connected to at least one direct current output DCOUT of the battery arrangement 1 , and the battery unit AU1 , AU2, AUn being charged, whereby the switch SAU1 , SAU2, SAUn associated with the battery unit AU1 , AU2, AUn is open and the battery unit AU1 , AU2, AUn is disconnected from each direct current output DCOUT of the battery arrangement. Status information describing the operating mode of the battery unit AU1 , AU2, AUn include the current of the battery unit, the voltage of the battery unit, the charge level of the battery unit, and the temperature of the battery unit.

The control unit CU of the battery arrangement 1 is connected to the battery units AU1 , AU2, AUn and configured to receive status information representing the operating mode of the battery unit AU1 , AU2, AUn from the management system BMS of the battery unit AU1 , AU2, AUn, and to control the connecting and disconnecting of the battery unit AU1 , AU2, AUn to and from the direct current output DCOUT of the battery arrangement 1 on the basis of at least one status information representing the operating mode of said battery unit AU1 , AU2, AUn.

According to an embodiment, the control unit CU is configured to control the battery unit U1 , AU2, AUn to disconnect from the direct current output DCOUT of the battery arrangement 1 in response to receiving status information on the battery unit AU1 , AU2, AUn, which indicates the battery unit AU1 , AU2, AUn having developed a fault, or the charge level of the battery unit AU1 , AU2, AUn having gone below the minimum. The battery unit AU1 , AU2, AUn having become faulty may be indicated on the basis of a high temperature of the battery unit, for example.

When the control unit CU receives status information indicative of the fault in the battery unit, the control unit CU controls, via the signal bus CU_SAU, the switch SAU1 , SAU2, SAUn associated with the battery unit AU1 , AU2, AUn in question to open, which prevents direct current supply from the battery unit AU1 , AU2, AUn to the direct current output DCOUT of the battery arrangement 1 . The control unit CU may further forward information to the management unit MU on the battery unit AU1 , AU2, AUn having developed a fault and the identification information of the faulty battery unit AU1 , AU2, AUn, whereby the owner of the battery arrangement 1 may replace the faulty battery unit AU1 , AU2, AUn with a new one.

Correspondingly, when the control unit CU receives status information indicative of the charge level of battery unit having gone below the minimum, the control unit CU controls, via the signal bus CU_SAU, the switch SAU1 , SAU2, SAUn associated with the battery unit AU1 , AU2, AUn in question to open, which prevents direct current supply from the battery unit AU1 , AU2, AUn to the direct current output DCOUT of the battery arrangement 1 . This way, excessive exhaustion of the battery unit AU1 , AU2, AUn and the potentially resulting damage to the battery unit AU1 , AU2, AUn may be prevented.

According to an embodiment, the control unit CU is configured to control the battery unit AU1 , AU2, AUn to connect to the direct current output DCOUT of the battery arrangement 1 in response to receiving status information on the battery unit AU1 , AU2, AUn reaching a preset charge level. Said preset charge level may be such a smallest charge level after the reaching of which the battery unit in question may be connected to supply the direct current load DCL1 , DCL2, DCL3, if this is imperative in order to continue the operation of the loads. Said preset charge level may also be the maximum charge level of an battery unit, corresponding to the largest allowed charge set for the battery unit. In such a case, the battery unit AU1 , AU2, AUn may be connected immediately after reaching the maximum charge level to the direct current output DCOUT of the battery arrangement 1 to increase the magnitude of the back-up power produced by the battery units AU1 , AU2, AUn. Said preset charge level may also be a percentage of the maximum charge level of the battery unit.

According to an embodiment, the battery arrangement 1 comprises battery units AU1 , AU2, AUn whose voltage levels differ from each other, so the nominal voltages of battery units AU1 , AU2, AUn belonging to the same battery arrangement 1 may differ from each other.

When each battery unit AU1 , AU2, AUn is connected in parallel, a fault in one or more battery units AU1 , AU2, AUn, or the reaching of the minimum charge level, does not affect the ability of the other battery units AU1 , AU2, AUn to act as back-up power sources. Further, since the battery units AU1 , AU2, AUn are connected in parallel with the rectifier unit ACDC, a possible fault in the rectifier unit ACDC, only, and/or in one or a few battery units AU1 , AU2, AUn does not prevent the supply of direct current to the direct current loads DCL1 , DCL2, DCL3.

Still referring to Figure 1 , for at least one load DCL1 , DCL2, DCL3 connected to the direct current output DCOUT of the battery arrangement 1 , priority levels PR _s tat may be defined or set in the control unit CU, indicating the order of importance of the loads DCL1 , DCL2, DCL3. Loads with higher priority levels are the loads where the aim is to keep them operational for as long as the battery arrangement 1 is able to produce enough electric power or electric energy for said loads, whereas the loads having a lower priority level are such loads that may first be disconnected from the battery arrangement 1 , if the bat- tery arrangement 1 is unable to produce enough electric power or electric energy for all the loads. With reference to Figure 1 , it may be assumed, for example, that the load DCL1 illustrates the highest level loads, which need to be kept operational for as long as possible. Such loads may include, for example, equipment used for maintaining a person's vital functions, or for operations. The load DCL2 may describe loads whose continuous operation is not necessary, but which preferably are not disconnected entirely for long periods of time. Such loads may be equipment used for communications links, for example. The load DCL 3 may for its part describe the lowest-level loads, which may, if need be, be entirely disconnected for long periods of time. Such loads may be, for example, loads used for illumination of households.

According to an embodiment, the battery arrangement 1 for supplying direct current comprises at least one direct current output DCOUT for connecting the battery arrangement 1 to at least one load DCL1 , DCL2, DCL3, at least one battery unit AU1 , AU2, AUn, which is connectable to the at least one direct current output DCOUT of the battery arrangement 1 , and at least one control unit CU, which is configured to determine electric power P _A u available from the at least one battery unit AU1 , AU2, AUn and to control the supply of direct current to the at least one direct current output DCOUT of the battery arrangement 1 on the basis of electric power P _A u available from said at least one battery unit AU1 , AU2, AUn and a priority level PR _s tat assigned to the at least one load DCL1 , DCL2, DCL3. The control unit CU of the battery arrangement 1 may have one or more predetermined limit values P| _imit to which the electric power available from the battery arrangement 1 is compared. When the electric power available from the battery arrangement 1 is less than the predetermined limit value, one or more loads of low priority level may be disconnected from the battery arrangement 1 , whereas when the electric power available from the battery arrangement 1 exceeds said limit value, one or more loads of low priority level may be connected again to the battery arrangement 1 . Said load priority levels and limit values associated with the electric power available from the battery arrangement 1 may also be changed dynamically by the control unit CU when new battery units or loads are connected to the battery arrangement 1 , or when the electric power or energy available from the battery arrangement 1 drops due to removal of battery units AU1 , AU2, AUn, for instance. In addition, the control unit CU may comprise or may be provided with means for de- termining load-specific real-time energy consumption and means for estimating the time available for using the loads on the basis of the electric power or electric energy available from the battery arrangement 1 and the load-specific realtime data on energy consumption.

In its minimum configuration, the battery arrangement 1 may com- prise only one battery unit and an associated control unit CU. In that case said battery unit is the only unit producing electric power to the direct current output DCOUT of the battery arrangement 1 . This means that the value to be assigned to the one or more limit values P| _imi t, which indicates the limit under which loads of a lower priority level P _sta t, e.g. loads DCL2 and/or DCL3, are disconnected from the battery arrangement 1 , may even be quite high in relation to the value of the electric power P _A u of the battery unit available in the battery unit 1 . Loads of a higher priority level, in this example load DCL1 , are thus assigned the longest time of use possible.

According to an embodiment, the battery arrangement 1 comprises two or more battery units AU1 , AU2, AUn connectable in parallel with one another, and the control unit CU is configured to control the supply of direct current to at least two direct current outputs DCOUT of the battery arrangement 1 on the basis of the electric power P _A u available from said at least two battery units AU1 , AU2, AUn and the priority levels PR _s tat assigned to the loads DCL1 , DCL2, DCL3 connectable to said at least two direct current outputs DCOUT. The electric power P _A u or the electric energy available from the one or more battery units AU1 , AU2, AUn may be determined by means of the control unit CU, for example, or on the basis of the charging state of the battery units AU1 . AU2, AUn.

According to an embodiment, the battery arrangement 1 may be associated with only one load provided with a priority level enabling the supply of electric power to the load in question to be disconnected from time to time. This enables to extend the total time during which the battery arrangement 1 is capable of at least occasionally supplying direct current to said load. This type of arrangement is possible for example in situations where electric energy to the battery arrangement 1 is not available for a long time for charging the battery units AU1 , AU2, AUn of the battery arrangement 1 and where the loads to be used are not critical.

According to the embodiment illustrated in Figure 1 , the battery ar- rangement 1 also comprises at least one alternating current input ACIN and at least one rectifier unit ACDC connectable to the alternating current input ACIN for converting the alternating current to direct current. The rectifier unit ACDC comprises at least one alternating current input 2 and at least one direct current output 3. In addition, the at least one battery unit AU1 , AU2, AUn is a rechargeable battery unit AU1 , AU2, .., AUn and connectable to the at least one direct current output 3 of the rectifier unit ACDC for recharging the battery unit AU1 , AU2, AUn with direct current produced by the rectifier unit ACDC. Said at least one rechargeable battery unit can then be used for producing electric power for loads while non-rechargeable battery units possibly included in the system are being replaced by new ones.

According to an embodiment, the at least one direct current output 3 of the rectifier unit ACDC is connectable to the direct current output DCOUT of the battery arrangement 1 in parallel with said at least one battery unit AU1 , AU2, AUn. Consequently, direct current may be supplied to the at least one direct current output DCOUT of the battery arrangement 1 both directly from the rectifier unit and from the one or more battery units AU1 , AU2, AUn.

According to an embodiment, the control unit CU is configured to control the supply of direct current produced by the rectifier unit ACDC between the at least one battery unit AU1 , AU2, AUn and a load DCL1 , DCL2, DCL3 connected to the at least one direct current output DCOUT of the battery arrangement 1 on the basis of the electric power P _A u available from the battery unit AU1 , AU2, AUn and the priority level PRSTAT assigned to said at least one load DCL1 , DCL2, DCL3. This enables loads of higher priority levels PRSTAT, for example, to be fed directly by the direct current produced by the rectifier ACDC, and any excess direct current produced by the rectifier ACDC may be routed for charging the battery units AU1 , AU2, AUn. Loads of lower priority levels may be used, when necessary, by means of battery units already charged, or they may even be disconnected altogether for a while if charging of the battery units AU1 , AU2, AUn is more critical due to future breaks in the use of alternating current sources ACS1 , ACS2, ACS3, ACS4.

According to an embodiment, the control unit CU is configured to determine the electric power P _A u produced by the rectifier unit ACDC and to control the supply of the direct current produced by the rectifier unit ACDC between at least one battery unit AU1 , AU2, AUn and a load DCL1 , DCL2, DCL3 connected to the at least one direct current output DCOUT of the battery arrangement 1 on the basis of the electric power P _A u available from the at least one battery unit AU1 , AU2, AUn, the priority level PRSTAT assigned to said at least one load DCL1 , DCL2, DCL3, and the predetermined electric power PACDC produced by the rectifier unit ACDC. In this embodiment, also the electric power PACDC produced by the rectifier unit ACDC is determined with preci- sion, whereby the supply of electric power for the load DCL1 , DCL2, DCL3 connectable to the at least one direct current output DCOUT of the battery unit 1 may be controlled on the basis of the electric power PACDC produced by the rectifier unit ACDC of the battery arrangement 1 , the electric power P _A u available in the battery units AU1 , AU2, AUn, and the priority levels of the loads DCL1 , DCL2, DCL3.

An advantage of this solution is that since the amount of electric power or electric energy available from the battery unit 1 is limited in relation to the power taken by loads connectable to the battery arrangement, it provides a simple means for restricting the supply of electric power to loads of less im- portant priority levels and hence to increase the time of use available to loads of more important priority levels.

Figure 3 schematically shows the battery arrangement 1 according to Figure 1 at a component level and divided into modules. Figure 3 illustrates an alternating current input unit or module ACIN_M, which comprises neces- sary coupling points and the related electric circuits and switches for connecting the available alternating current sources ACS1 , ACS2, ACS3, ACS4 to the battery arrangement 1 , and protection units PU1 , PU2, PU3, PU4. If one of the available sources of electric energy is a solar power plant, the input unit ACIN_M may also contain the necessary coupling points and the related electric circuits and switches for supplying electric energy in the form of direct cur- rent directly from the solar power plant to the battery arrangement 1 . In other words, if one of the alternating current power sources is a solar power plant, the solar power plant may be connected through a controllable switch, for example, either to the direct current output 3 of the rectifier unit ACDC or to the direct current output DCOUT of the battery arrangement 1 , without converting the direct current produced by the solar power plant to alternating current at any point.

Figure 3 also shows three battery unit modules AU_M, each of which comprises one or more battery units AU1 , AU2, AUn. The battery unit module AU_M comprises the necessary coupling points, the related elec- trie circuits and switches for connecting alternating current inputs 2 coming from the alternating current input module ACIN_M to the battery unit modules AU_M, and a necessary number of rectifier units ACDC.

Figure 3 further shows a direct current output unit or module DCOUT_M, which comprises the necessary coupling points and the related electric circuits and switches through which the direct current outputs 4 of the battery unit modules AU_M may be connected to the direct current output module DCOUT_M. The direct current output unit or module DCOUT_M may also comprise the necessary coupling points and the related electric circuits and switches through which the direct current output module DCOUT_M may be connected to loads DCL1 , DCL2, DCL3 that are connectable to the battery arrangement 1 .

Figure 3 also shows a control unit module CU_M connected to the input module ACIN_M through signal buses CU_PU and CU_SAC and to the direct current output module DCOUT_M through a signal bus CU_SDC.

Figure 3 still further shows a virtual private network VPN through which the control unit module CU_M may be connected to the battery unit modules AU_M and to a user interface unit or module UI_M connectable to the system and implemented by means of a touch screen technology, for example, through which the settings or functions of the battery arrangement 1 may be controlled on site. A device or devices implemented by means of the virtual private network VPN may obtain the necessary operating energy for instance from the direct current output 4 of one battery unit module AU_M over a connection PWR_VPN depicted schematically in Figure 3. Also the user interface module UI_M may obtain the necessary operating energy from the direct current output module DCOUT_M over a connection PWR-UI_M depicted sche- matically in Figure 3. As stated above, also the aforementioned signal buses CU_PU, CU_SAC, and CU_SDC may be implemented by means of the virtual private network VPN.

The modules shown in Figure 3 may be stacked one on top of the other, for instance, into a mounting cabinet reserved for them so that each in- dividual module may be replaced while other modules stay in place. Consequently, the electric power capacity of the battery arrangement 1 is also easy to increase by adding new battery unit modules AU_M.

It will be apparent to a person skilled in the art that as technology advances, the basic idea of the invention may be implemented in many differ- ent ways. The invention and its embodiments are thus not restricted to the examples described above but may vary within the scope of the claims.