JP6917768B2 - Power storage system - Google Patents

Description

Embodiments of the present invention relate to a power storage system .

Conventionally, there is known a technique of controlling a power conversion device to generate invalid power to control the voltage of a power system. In connection with this, a technique for arbitrarily allocating the active power command and the ineffective power command of the static frequency converter in the combination of the rotary frequency converter and the static frequency converter, a plurality of active power control amounts or ineffective power control. A technique for selecting or integrating the power control amount to be output by the system from the amount, and a technique for allocating charge / discharge power to a plurality of power converters have been proposed. However, with the conventional technology, there are cases where high-efficiency operation and long life cannot be achieved.

Japanese Unexamined Patent Publication No. 1-1866 Japanese Unexamined Patent Publication No. 2015-149880 Japanese Unexamined Patent Publication No. 2014-171335

An object to be solved by the present invention is to provide a power storage system capable of suppressing output fluctuations of an electric power system, and achieving high-efficiency operation and long life.

The power storage system of the embodiment includes a plurality of power storage units, a power conversion unit, and a control unit. The plurality of power storage units store electric power. The power conversion unit is provided corresponding to each of the plurality of power storage units, converts the DC power from the power storage unit into AC power, and outputs the DC power to the power system. The control unit determines the respective amounts of active power and inactive power in the AC power output by the power conversion unit, and among the plurality of power conversion units , the power that is the target of causing the power system to output the active power. The conversion unit is preferentially determined as the power conversion unit that outputs the invalid power.

The figure which shows an example of the structure of the electric power system 1 including the power storage system 100 in 1st Embodiment. The figure which shows an example of the structure of the power storage system 100 in 1st Embodiment. The figure which shows an example of the structure of the power storage controller 110. The flowchart which shows the flow of a series of processing by the control unit 112 in 1st Embodiment. The figure which shows an example of the structure of the power storage system 100 in the modification of 1st Embodiment. The flowchart which shows the flow of a series of processing by the control unit 112 in 2nd Embodiment. FIG. 5 is a flowchart showing a flow of a series of processes by the control unit 112 in the third embodiment. The figure which shows an example of the correlation between the deterioration characteristic of a secondary battery which is an example of a power storage part 120, and SOC. The figure which shows an example of the charge need characteristic derived from the deterioration characteristic of the secondary battery of FIG. The flowchart which shows the flow of a series of processing by the control unit 112 in 4th Embodiment. The figure which shows an example of the power conversion efficiency of a power conversion unit PCS. The figure which shows an example of the charge / discharge efficiency of a power storage part 120. The figure which shows the characteristic of the efficiency of a unit which combined the power conversion efficiency of a power conversion unit PCS and the charge / discharge efficiency of a power storage unit 120. FIG. 5 is a flowchart showing a flow of a series of processes by the control unit 112 in the fifth embodiment.

Hereinafter, the power storage system of the embodiment will be described with reference to the drawings.

(First Embodiment)
FIG. 1 is a diagram showing an example of the configuration of the electric power system 1 including the power storage system 100 in the first embodiment. The power system 1 of the present embodiment, for example, transmits a voltage between the AC power power system EPS, the power storage system 100, the power generation system 200, the customer's power receiving equipment 300, and the power storage system 100 and the power system EPS. The transformer TF1 for conversion, the transformer TF2 for converting the voltage between the power generation system 200 and the power system EPS, and the transformer TF3 for converting the voltage between the power receiving facility 300 and the power system EPS are provided.

The power storage system 100 is provided together with the power generation system 200, which has an unstable power supply capacity to the power system EPS, for example, to alleviate fluctuations in the power supply to the power system EPS. That is, the power storage system 100 compensates for output fluctuations in the power system EPS. For example, the power storage system 100 includes a plurality of power storage units for charging surplus power that is excessive with respect to the power demand in the power system.

The power generation system 200 is a power generation system that uses renewable energy. The power generation system 200 may be, for example, a solar power generation system or a wind power generation system. Further, the power generation system 200 may be a geothermal power generation system or a tidal power generation system, or may be a system in which a plurality of these power generation systems are combined.

The power receiving facility 300 of the consumer receives power from the power system EPS, for example, and supplies power to various devices.

The transformers TF1 to TF3 step down the AC power supplied from the power system EPS and boost the AC power supplied from the connected system or equipment.

FIG. 2 is a diagram showing an example of the configuration of the power storage system 100 according to the first embodiment. For example, the power storage system 100 includes a power storage controller 110, a plurality of power storage units 120-1 to 120-N (N is an arbitrary natural number), a plurality of power conversion units PCS ₁ to PCS _N, and a plurality of detection units 130-. 1 to 130-N are provided. Hereinafter, when each of the plurality of power storage units 120-1 to 120-N is not distinguished, the description will be simply referred to as "power storage unit 120". Further, when each of the plurality of power conversion units PCS ₁ to PCS _N is not distinguished, the description will be simply referred to as “power conversion unit PCS”. Further, when each of the plurality of detection units 130-1 to 130-N is not distinguished, the description will be simply referred to as "detection unit 130".

By controlling the power conversion unit PCS, the power storage controller 110 switches the power storage unit 120 to be charged / discharged and adjusts the charge / discharge amount.

The power storage unit 120 is a medium capable of storing electric power energy. The power storage unit 120 includes, for example, a secondary battery such as a lithium ion battery, a lead storage battery, a sodium-sulfur battery, a redox flow battery, or a nickel hydrogen battery, and at least one of an electric double layer capacitor.

The power conversion unit PCS is provided, for example, corresponding to each of _{the plurality of power conversion units PCS 1} to PCS _N. The power conversion unit PCS has, for example, a semiconductor element (not shown) such as a transistor or a thyristor. The power conversion unit PCS converts AC power into DC power or DC power by switching the circuit between a conductive state (gate-on state) and a cut-off state (gate-off state) using this semiconductor element. To AC power. For example, when the power conversion unit PCS is controlled by the power storage controller 110, the power conversion unit PCS converts the AC power supplied from the power system EPS into DC power, and charges the power storage unit 120 with the converted DC power.

Further, when the power conversion unit PCS is controlled by the power storage controller 110, the power storage unit 120 discharges the power (DC power) stored in the power storage unit 120. The power conversion unit PCS converts the DC power discharged from the power storage unit 120 into AC power. For example, the power conversion unit PCS converts the DC power discharged from the power storage unit 120 into active power (unit: [W]) and ineffective power (unit: [Var]) having different phase components from each other as AC power. ..

The detection unit 130 detects the power storage state of the power storage unit 120 and outputs a detection signal indicating the detection result to the power storage controller 110. For example, when the power storage unit 120 includes a secondary battery, the detection unit 130 detects SOC (State Of Charge) indicating the charge capacity of the secondary battery as the power storage state. Further, when the power storage unit 120 includes an electric double layer capacitor, the detection unit 130 detects the charge capacity of the electric double layer capacitor as a power storage state.

FIG. 3 is a diagram showing an example of the configuration of the power storage controller 110. The power storage controller 110 includes, for example, a communication unit 111, a control unit 112, and a storage unit 113.

The communication unit 111 transmits a charge power command value and a discharge power command value from the external server by communicating with an external server such as an EMS (Energy Management System) via a network including a WAN (Wide Area Network) or the like. Receive. The charging power command value is a command value for charging the power storage unit 120 with a predetermined power supplied from the power system EPS. The discharge power command value is a command value for discharging a predetermined power from the power storage unit 120 to the power system EPS. For example, the discharge power command value is information in which the amount of active power and the amount of ineffective power to be output to the power storage system 100 are defined. Hereinafter, the amount of active power determined to be output by _{the discharge power command value is referred to as "active power command value Pre} ", and the amount of invalid power determined to be output by the discharge power command value is referred to as "invalid power command value". It will be described as " _{Q ref".}

Further, the communication unit 111 communicates with the power conversion unit PCS and the detection unit 130 via a communication line such as PCI (Peripheral Component Interconnect). The communication unit 111 may be a separate body for communicating with an external device via a network and for communicating with a device inside the power storage system 100 via a communication line.

The control unit 112 may be realized by, for example, a processor such as a CPU (Central Processing Unit) executing a program stored in the storage unit 113. Further, the control unit 112 may be realized by hardware such as LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), or by cooperation between software and hardware. It may be realized.

The storage unit 113 may be realized by, for example, a ROM (Read Only Memory), a flash memory, an HDD (Hard Disk Drive), an SD card, an MRAM (Magnetoresistive Random Access Memory), a RAM (Random Access Memory), a register, or the like. The storage unit 113 stores a program or the like executed by the processor of the control unit 112.

When the communication unit 111 receives any of the charge power command value and the discharge power command value, the control unit 112 controls the power conversion unit PCS based on the power command value.

For example, when the communication unit 111 receives the charge power command value, the control unit 112 has a plurality of detection signals output by the detection unit 130 so that the power satisfying the charge power command value is charged. The power conversion unit PCS to be charged is determined _{from the power conversion units PCS 1 to PCS N.} For example, the control unit 112 prioritizes the power conversion unit PCS provided as a pair with the power storage unit 120 whose SOC and charge capacity are smaller than the reference value, and determines the power conversion unit PCS to be charged.

Further, for example, when the discharge power command value is received by the communication unit 111, the control unit 112 determines the respective amounts of active power and inactive power having different phase components in the AC power. For example, the control unit 112 causes the plurality of power conversion units PCS ₁ to output the active power from the PCS _{N so that the active power satisfying the active power command value Pre included in the discharge power command value is output.} The target power conversion unit PCS is determined. At this time, the control unit 112, for each of the power converter PCS, calculates the active power to be output, calculated active power command value P _{ref (i} showing the active energy that _| i is the argument 1~N (Any) is notified to each power conversion unit PCS using the communication unit 111 (assigned to each power conversion unit PCS) to control each power conversion unit PCS.

For example, the control unit 112 allocates (notifies) the amount of active power that can be output to the maximum by the power conversion unit PCS determined as the output target of the active power as the active power command value _{Ref (i). The sum of the active power command value Pref} (i) assigned to each power conversion unit PCS is, for example, about the active power command value _Pref .

On the other hand, the control unit 112, the discharge power so reactive power is output to meet the reactive power command value Q _ref included in the command value, the power converter is determined as the output target of the active power PCS (active power command value P _ref The power conversion unit PCS to which (i) is assigned is determined as the power conversion unit PCS to which the invalid power is output. At this time, the control unit 112 calculates the amount of invalid power to be output to each power conversion unit PCS, and uses the communication unit 111 to _{set the invalid power command value Qref (i) indicating the calculated amount of invalid power.} Then, each power conversion unit PCS is notified (assigned to each power conversion unit PCS) to control each power conversion unit PCS.

For example, the control unit 112 allocates (notifies) as _{the invalid power command value QRef} (i) the amount of invalid power that can be output to the maximum by the power conversion unit PCS determined as the output target of the invalid power. _{The sum of the invalid power command value Qref} (i) assigned to each power conversion unit PCS is, for example, about the _{invalid power command value Qref.}

_{In this way, the power conversion unit PCS i, which} is the output target of the active power and the ineffective power, stores electricity based on the active power command value _Pref (i) and the ineffective power command value _{Qref (i) assigned to itself.} The DC power discharged to the unit 120 is divided into the active power _{for the amount of power specified by the active power command value Pref} (i) and the invalid power for the amount of power specified by the invalid power command value _Qref (i). Convert to and.

FIG. 4 is a flowchart showing a flow of a series of processes by the control unit 112 in the first embodiment. In this flowchart, for example, the discharge power command value is received by the communication unit 111, and the control unit 112 determines the power conversion unit PCS to be output of the active power from among the _{plurality of power conversion units PCS 1} to PCS _N. It is performed later (after the active power command value Pref (i) is assigned to the power conversion unit PCS).

First, the control unit 112 selects one power conversion unit PCS _i to be processed from the plurality of power conversion units PCS ₁ to PCS _N , and erases the previous processing result (to clear to zero). _{In addition, the value Qref_temp} (0) tentatively calculated as the total amount of invalid power output from the entire power storage system 100 is set to zero (step S100).

Next, the control unit 112 determines whether or not the active power command value _{Pref (i) assigned to the power conversion unit PCS i} selected as the processing target is zero (step S102). _{That is, the control unit 112 determines whether or not the power conversion unit PCS i} selected as the processing target is selected as the output target of the active power.

When the active power command value _Pref (i) assigned to the power conversion unit PCS _i is zero, that is, when the power conversion unit PCS _i selected as the processing target is not selected as the active power output target, the control unit 112 sets the invalid power command value _Qref (i) assigned to the power conversion unit PCS _i to zero (step S104).

On the other hand, when the active power command value _{Pref (i) assigned to the power conversion unit PCS i} is not zero, that is, when the power conversion unit PCS _i selected as the processing target is selected as the active power output target, control is performed. With reference to the following formula (1), the unit 112 includes the _{apparent power S ref} (i) (unit: [VA]), which is the rated output of _{the power conversion unit PCS i , and the active power command value Pref} (i). Based on the above, the amount of invalid power that can be output to the maximum _{by the power conversion unit PCS i is calculated as the invalid power command value QRef} (i) (step S106).

_{Next, the control unit 112 sets the provisional invalid power value Qref_temp} (i), which is assumed to be output from the power storage system 100 at the i-th loop processing count, to the past (i-1) times. The value is changed to the sum of the invalid power command value Q _ref (i-1) calculated at the time of the current processing and the invalid power command value Q _{ref (i) calculated at the current i-th processing time (step S108).} .. In the case of initial processing (i = 1), provisional reactive power value _{Q ref_temp} (1) a reactive power command value _{Q ref} (1) to _{(Q ref_temp (1) = Q} ref (1)).

Next, the control unit 112, provisional reactive power value _{Q ref_temp} (i) it is determined whether a reactive power command value _{Q ref} than is required for the power storage system 100 (step S110).

If provisional reactive power value _{Q ref_temp} (i) is the reactive power command value _{Q ref} above, the control unit 112, a reactive power command value _{Q ref} (i) to be assigned to the power conversion unit PCS _i, requests disabled to be from the power command value _{Q ref,} it is set to a value obtained by subtracting the (i-1) -th reactive power command calculated by the processing time value _Q ref (i-1) (step S112). That is, the control unit 112 is a trial calculation value obtained by adding _{the invalid power command value Q ref} (i) to be assigned this time to the sum of the invalid power command value Q _{ref (i) assigned to the other power conversion unit PCS i.} a _{(= Q ref_temp (i))} , by comparing the reactive power command value _{Q ref} required, the larger the better estimates values than the reactive power command value _{Q ref} required, disabled allocated in this process The power command value Q _ref (i) is not set as the invalid power value that can be output to the maximum, but the required power command value Q _ref and the invalid power command value Q _ref assigned to the other power conversion unit PCS _i. It is the difference from the total of (i).

On the other hand, if the provisional reactive power value _{Q ref_temp} (i) is less than the reactive power command value _{Q ref,} the power control unit 112, which among PCS _N from a plurality of power converting unit PCS _1, and selected for processing conversion unit PCS _i and selects a different one of the power converter _{PCS i + 1} (step S114). Then, the control unit 112 shifts the processing to the above-mentioned S102 until the sum of the invalid power command values _{Qref (i) assigned to each power conversion unit PCS i} satisfies the required invalid power command value _Qref. , S102 to S108 are repeated. This completes the processing of this flowchart.

According to the first embodiment described above, the plurality of power storage units 120-1 to 120-N for storing electric power and the plurality of power storage units 120-1 to 120-N are provided corresponding to each of the plurality of power storage units 120-1 to 120-N. Control that determines the amount of active power and invalid power in the AC power output by the power conversion unit PCS that converts the DC power from the power storage unit 120 into AC power and outputs it to the power system EPS, and the AC power output by the power conversion unit PCS. and parts 112 includes a control unit 112, preferentially a predetermined condition is satisfied power conversion unit PCS from a plurality of the power converter PCS ₁ in PCS _N, determines the power conversion unit PCS to output reactive power As a result, the power conversion unit PCS determined as the target for outputting the active power also outputs the invalid power, so that the number of the power conversion unit PCS to be operated can be reduced. As a result, for example, the semiconductor element of the power conversion unit PCS that is not in operation can be gated off, so that power leakage on the power storage unit 120 side, which is a DC power source, can be minimized. As a result, it is possible to suppress output fluctuations of the power system EPS, achieve high-efficiency operation, and extend the service life.

(Modified example of the first embodiment)
Hereinafter, a modified example of the first embodiment will be described. FIG. 5 is a diagram showing an example of the configuration of the power storage system 100 in the modified example of the first embodiment. For example, the power storage controller 110 calculates the amount of invalid power carried by each power conversion unit PCS based on the _{invalid power command value QRef} included in the discharge power command value received from an external server such as EMS, and the calculated invalid power. reactive power command value _{Q ref} indicating an amount (i) is allocated to each power conversion unit PCS _i (allocated) in place of, the external controller 140, the reactive power command value _{Q ref} is allocated to each power conversion unit PCS _i (I) may be received. The external controller 140 holds information including, for example, the number of power conversion unit PCS included in the power storage system 100 and the amount of power that can be output by each power conversion unit PCS, and receives the discharge power command value from the external server. Then, the invalid power command value _Qref (i) to be distributed to each power conversion unit PCS _{i in the power storage system 100 is generated.} Then, the external controller 140 transmits the invalid power command value _QRef (i) to _{be distributed to each power conversion unit PCS i to the power storage controller 110.} Thereby, as in the above-described embodiment, it is possible to suppress the output fluctuation of the power system EPS, and to achieve high-efficiency operation and long life.

(Second embodiment)
Hereinafter, the power storage system 100A according to the second embodiment will be described. In the power storage system 100 according to the first embodiment described above, it is assumed that the power conversion unit PCS determined as the target for outputting the active power also outputs the invalid power, but only the power conversion unit PCS that outputs the active power. When outputting the invalid power, it may not be possible to output the invalid power sufficient to satisfy the _{invalid power command value QRef included in the discharge power command value.} On the other hand, in the power storage system 100A of the second embodiment, when the invalid power _{sufficient to satisfy the invalid power command value QRef} cannot be output, the power conversion unit PCS which is not determined as the target to output the active power is also used. It differs from the first embodiment in that it outputs ineffective power. Hereinafter, the differences from the first embodiment will be mainly described, and the points common to the first embodiment will be omitted. In the description of the second embodiment, the same parts as those of the first embodiment will be described with the same reference numerals.

The control unit 112 in the second embodiment is the power that outputs the active power when the sum of the invalid power command value _{Qref (i) assigned to each power conversion unit PCS is less than the invalid power command value Qref.} When the amount of invalid power _{carried by the conversion unit PCS is less than the amount of invalid power indicated by the invalid power command value QRef,} the power conversion unit PCS that was not determined as the output target of the active power is also determined as the output target of the invalid power. ..

FIG. 6 is a flowchart showing a flow of a series of processes by the control unit 112 in the second embodiment. In this flowchart, for example, the discharge power command value is received by the communication unit 111, and the control unit 112 determines the power conversion unit PCS to be output of the active power from among the _{plurality of power conversion units PCS 1} to PCS _N. It is performed later (after the active power command value Pref (i) is assigned to the power conversion unit PCS).

First, the control unit 112 selects one power conversion unit PCS _i to be processed from the plurality of power conversion units PCS ₁ to PCS _N , and erases the previous processing result (to clear to zero). _{In addition, the value Qref_temp} (0) tentatively calculated as the total amount of invalid power output from the entire power storage system 100 is set to zero (step S200).

Next, the control unit 112 determines whether or not the number i (= loop processing number i) of the power conversion unit PCS selected as the processing target exceeds the total number N of the power conversion unit PCS included in the power storage system 100A ( Step S202).

When the number i of the power conversion unit PCS selected as the processing target is equal to or less than the total number N of the power conversion unit PCS, the control unit 112 assigns the active power command value _{Pre (assigned to the power conversion unit PCS i} selected as the processing target). It is determined whether or not i) is zero (step S204). Since the following processes S206 to S216 are the same as the processes S104 to S114 in the flowchart of FIG. 4 described above, the description thereof will be omitted.

On the other hand, when the number i of the power conversion unit PCS selected as the processing target exceeds the total number N of the power conversion unit PCS, the control unit 112 sets the processing target from among _{the plurality of power conversion units PCS 1} to PCS _N. One power conversion unit PCS _k is selected, and the estimated value Q _{ref_temp (0) of the invalid power is updated to the estimated value Q ref_temp} (N) at the time of the Nth processing (step S218).

Next, the control unit 112 determines whether or not the number k of the power conversion unit PCS selected as the processing target (= the number of times of loop processing described later k) exceeds the total number N of the power conversion unit PCS included in the power storage system 100A. Determine (step S220).

When the number k of the power conversion unit PCS selected as the processing target is less than the total number N of the power conversion unit PCS, the control unit 112 assigns the active power command value _{Pref (assigned to the power conversion unit PCS k} selected as the processing target). It is determined whether or not k) is zero (step S222). That is, the control unit 112 determines the power converter PCS _k were selected for processing, whether or not is selected as the output target of the active power.

If the effective allocated to the power converter PCS _k were selected for processing power command value P _{ref (k)} is not zero, i.e., the power conversion unit PCS _k were selected for processing, select as the output target of the active power If so, the control unit 112 assigns the invalid power command value _{Qref (k) to the power conversion unit PCS k} in the process of the above-mentioned processes from S202 to S216, so that the processes from S224 to S228 are omitted. , S230.

On the other hand, when the active power command value _Pref (k) assigned to the power conversion unit PCS _k selected as the processing target is zero, that is, the power conversion unit PCS _k selected as the processing target is set as the active power output target. If not selected, the control unit 112, a reactive power command value _{Q ref} (k) assigned to this power conversion unit PCS _k, the power converter PCS _k is the maximum possible output reactive power value _{Q ref_limit} (step S224). For example, the reactive power value _{Q Ref_limit,} in Equation (1) described above, may be a reactive power command value _{Q ref} (k) when the effective power command value _P ref (k) = 0.

_{Next, the control unit 112 sets the provisional invalid power value Qref_temp} (k), which is assumed to be output from the power storage system 100A at the kth loop processing count, to the past (k-1) times. The value is changed to the sum of the invalid power command value Q _ref (i-1) calculated at the time of processing of the above and the invalid power command value Q _{ref (k) calculated at the current kth processing time (step S226).} ..

Next, the control unit 112, provisional reactive power value _{Q ref_temp} (k) is equal to or a reactive power command value _{Q ref} than is required for the power storage system 100A (step S228).

If provisional reactive power value _{Q ref_temp} (k) is less than the reactive power command value _{Q ref,} the control unit 112, from the PCS _N from a plurality of power converting unit PCS _1, a power conversion unit which is selected for processing One power conversion unit PCS _{k + 1} different from PCS _k is selected (step S230). Then, the control unit 112 obtains the sum of the invalid power command value _{QRef (k) assigned to each power conversion unit PCS k} by transferring the processing to the above-mentioned S220, and the processing in the previous stage (processing from S202 to S216). the sum of the provisional reactive power value _{Q ref_temp} (N) was found to meet the reactive power command value _{Q ref} required, the process is repeated S226 from S222.

On the other hand, in the processing of S220, when the number k of the power conversion unit PCS selected as the processing target is equal to or greater than the total number N of the power conversion unit PCS, or in the processing of S228, the provisional invalid power value _{Qref_temp} (k) When is equal to or greater than the invalid power command value Q _ref , the control unit 112 sets the invalid power command value Q _{ref (k) assigned to the power conversion unit PCS k} from the requested invalid power command value Q _ref to (k-1). ) Set the value obtained by subtracting _{the invalid power command value QRef} (k-1) calculated at the time of the third processing (step S232). That is, the control unit 112 _{does not set the invalid power command value Q ref} (k) assigned in this process to the invalid power value Q _{ref_limit} that can be output to the maximum, but instead sets the required invalid power command value Q _ref and the so far. It is the difference from the sum of the invalid power command value _{Qref (k) assigned in the process of.} This completes the processing of this flowchart.

According to the second embodiment described above, similarly to the first embodiment, the power conversion unit PCS determined as the target for outputting the active power also outputs the invalid power to operate the power conversion. The number of parts PCS can be reduced. As a result, it is possible to suppress output fluctuations of the power system EPS, achieve high-efficiency operation, and extend the service life.

Further, according to the second embodiment, when the power conversion unit PCS that outputs the active power outputs the invalid power, the invalid power _sufficient to satisfy the invalid power command value QRef required for the power storage system 100A is output. If this is not possible, the power conversion unit PCS, which is not the target of active power output, is also made to output invalid power. As a result, the output fluctuation of the power system EPS can be further suppressed while reducing the loss caused by the operation of the power conversion unit PCS.

Further, according to the second embodiment, when the power conversion unit PCS, which is not the output target of the active power, is to output the invalid power, the power conversion unit PCS is operated by outputting the invalid power that can be output to the maximum. It is possible to suppress the output fluctuation of the power system EPS while minimizing the increase in the power conversion unit PCS.

(Third Embodiment)
Hereinafter, the power storage system 100B according to the third embodiment will be described. In the power storage system 100B according to the third embodiment, the power conversion unit PCS to be output of the invalid power is determined based on the power storage state of the power storage unit 120 connected to each power conversion unit PCS. It differs from the second embodiment. Hereinafter, the differences from the first and second embodiments will be mainly described, and the points common to the first and second embodiments will be omitted. In the description of the third embodiment, the same parts as those of the first and second embodiments will be described with the same reference numerals.

FIG. 7 is a flowchart showing a flow of a series of processes by the control unit 112 in the third embodiment. In this flowchart, for example, the discharge power command value is received by the communication unit 111, and the control unit 112 determines the power conversion unit PCS to be output of the active power from among the _{plurality of power conversion units PCS 1} to PCS _N. It is performed later (after the active power command value Pref (i) is assigned to the power conversion unit PCS).

First, the control unit 112 in the third embodiment describes the storage state of the power storage unit 120 detected by the detection unit 130 (the charge capacity of the SOC of the secondary battery and the electric double layer capacitor) and the deterioration characteristics of the power storage unit 120. Based on the above, the charging needs are derived (step S300). The charging need is an index value indicating how much charging should be performed in order to suppress deterioration of the power storage unit 120. For example, the control unit 112 derives charging needs based on the deterioration characteristics according to the storage state of the power storage unit 120.

FIG. 8 is a diagram showing an example of the correlation between the deterioration characteristics of the secondary battery, which is an example of the power storage unit 120, and the SOC. In the figure, the horizontal axis represents SOC (unit: [%]), and the vertical axis represents deterioration rate (unit: [Ah / day]). As shown in the figure, for example, the deterioration rate of a secondary battery is significantly faster when the SOC is higher than when the SOC is low. For example, the control unit 112 uses the differential value of the deterioration rate that takes the maximum value by differentiating the deterioration rate with respect to the SOC and inverting the positive and negative signs in the deterioration characteristics of the secondary battery as illustrated in FIG. The standardized (normalized) characteristics (hereinafter referred to as charging needs characteristics) are derived. Information indicating the correlation between the deterioration characteristics of the secondary battery and the SOC as illustrated in FIG. 8 may be stored in the storage unit 113 in advance.

FIG. 9 is a diagram showing an example of charging needs characteristics derived from the deterioration characteristics of the secondary battery of FIG. In the figure, the horizontal axis represents SOC (unit is [%]), and the vertical axis is the value obtained by standardizing the differential value of the deterioration rate with respect to SOC and taking the absolute value (unit is [dimensionless]). Represents. In FIG. 8, for example, when the differential value of the deterioration rate with respect to the SOC is a positive value, the deterioration rate becomes faster as the SOC increases, so that the charging need becomes smaller as shown in FIG. Therefore, when the SOC increases and the differential value of the deterioration rate takes a positive value, it is preferable to discharge the secondary battery to lower the SOC.

The control unit 112 derives the charging needs corresponding to the current storage state of the storage unit 120 detected by the detection unit 130 according to the derived charging needs characteristics. As for the charging needs characteristics as illustrated in FIG. 9, instead of being derived by the control unit 112, those derived in advance may be stored in the storage unit 113.

Next, the control unit 112 determines the priority order for determining each of the _{plurality of power conversion units PCS 1} to PCS _N as an output target of the invalid power based on the charging needs derived for each power storage unit 120. (Step S302).

For example, since a power storage unit 120 having a low charging need is desired to be discharged as soon as possible, the control unit 112 has a power conversion unit PCS _{i provided as a pair with the power storage unit 120.} Set a high priority when selecting as an output target.

On the other hand, since the power storage unit 120 having a higher charging need is desired to be charged, the control unit 112 outputs the invalid power _{to the power conversion unit PCS i provided as a pair with the power storage unit 120.} Set a low priority when selecting as.

As a result, for example, for a secondary battery having a high SOC, the DC power charged inside can be preferentially discharged as invalid power, and for a secondary battery having a low SOC, further deterioration is suppressed. In addition, it is possible to refrain from discharging. As a result, deterioration of the secondary battery and the like can be suppressed.

_{Next, the control unit 112 selects one power conversion unit PCS i} to be processed from among the plurality of power conversion units PCS ₁ to PCS _N based on the respective priorities of the power conversion unit PCS. _{In order to erase the previous processing result (to clear to zero), the value Qref_temp} (0) tentatively calculated as the total amount of invalid power output from the entire power storage system 100 is set to zero (step S304). As a result, for example, the power conversion unit PCS connected to the power storage unit 120 having a higher SOC is preferentially selected from the plurality of power conversion units PCS ₁ to PCS _N.

Since the following processes S306 to S336 are the same as the processes S202 to S232 in the flowchart of FIG. 6 described above, the description thereof will be omitted.

According to the third embodiment described above, as in the first and second embodiments, the power conversion unit PCS determined as the target for outputting the active power is also operated by outputting the invalid power. The number of power conversion units PCS to be generated can be reduced. As a result, it is possible to suppress output fluctuations of the power system EPS, achieve high-efficiency operation, and extend the service life.

Further, according to the third embodiment described above, charging needs are derived based on the power storage state of the power storage unit 120 detected by the detection unit 130 and the deterioration characteristics of the power storage unit 120, and based on the derived charging needs. By determining the priority when determining the output target of the ineffective power for each power conversion unit PCS, the ineffective power can be output while maintaining the charge amount so as to reduce the deterioration.

In general, the invalid power output operation that outputs only the invalid power is different from the active power output operation that involves charging / discharging to the DC power supply side, although in principle there is no increase / decrease (loss) in the energy of the power storage unit 120. For example, when power is supplied from the power storage unit 120 to a control power source for driving the power storage controller 110, or due to a power loss of a circuit or the like, the phase is delayed to output invalid power, or the phase is advanced. In any case of the operation of outputting the ineffective power, the power on the DC side is consumed. Therefore, by preferentially using the power conversion unit PCS provided as a pair with the power storage unit 120 having a small charging need, the power storage unit 120 having a high SOC can be discharged preferentially. As a result, deterioration that occurs when the SOC is high can be suppressed.

(Fourth Embodiment)
Hereinafter, the power storage system 100C according to the fourth embodiment will be described. In the power storage system 100C according to the fourth embodiment, the power conversion unit PCS to be output of the invalid power is determined based on the energy efficiency of each unit when the power conversion unit PCS and the power storage unit 120 are combined into one unit. This is different from the first to third embodiments. Hereinafter, the differences from the first to third embodiments will be mainly described, and the points common to the first to third embodiments will be omitted. In the description of the fourth embodiment, the same parts as those of the first to third embodiments will be described with the same reference numerals.

FIG. 10 is a flowchart showing a flow of a series of processes by the control unit 112 in the fourth embodiment. In this flowchart, for example, the discharge power command value is received by the communication unit 111, and the control unit 112 determines the power conversion unit PCS to be output of the active power from among the _{plurality of power conversion units PCS 1} to PCS _N. It is performed later (after the active power command value Pref (i) is assigned to the power conversion unit PCS).

First, the control unit 112 in the fourth embodiment has a plurality of power conversion units based on the efficiency characteristics of the unit based on the power conversion efficiency characteristics of the power conversion unit PCS and the charge / discharge efficiency characteristics of the power storage unit 120. For each of PCS ₁ to PCS _N , the priority order for determining the output target of the invalid power is determined (step S400). The efficiency characteristic of the unit is an example of the "third efficiency characteristic".

FIG. 11 is a diagram showing an example of the efficiency characteristics of power conversion of the power conversion unit PCS. The horizontal axis in the figure represents the standardized value (unit: [%]) of the input / output value of the power conversion unit PCS based on the rated input / output value, etc., and the vertical axis represents the efficiency (unit) obtained by dividing the output power by the input power. Represents [%]). The input power may be the AC side power and the output power may be the DC side power, or the input power may be the DC side power and the output power may be the AC side power. The input / output values represent, for example, active power. As shown in FIG. 11, in the power conversion unit PCS, the smaller the active power that is input / output, the lower the efficiency due to the influence of loss generated in the internal circuit, and the larger the active power, the higher the efficiency tends to be. ..

FIG. 12 is a diagram showing an example of charge / discharge efficiency characteristics of the power storage unit 120. In the figure, the horizontal axis represents the value obtained by standardizing the input / output value of the power storage unit 120 by the rated input / output value or the like (unit: [%]), and the vertical axis represents the efficiency when the power storage unit 120 is charged / discharged (the unit is [%]). The unit is [%]). For example, the loss generated inside the power storage unit 120 (for example, the loss caused by heat generation) can be derived as ^{the square of the internal resistance R and the current I (R × I 2).} Therefore, as the power as input / output (charge / discharge power) increases, the loss also increases exponentially. Therefore, as shown in FIG. 12, the charge / discharge efficiency of the power storage unit 120 decreases exponentially as the power as input / output increases.

FIG. 13 is a diagram showing the efficiency characteristics of the unit in which the power conversion efficiency characteristics of the power conversion unit PCS and the charge / discharge efficiency characteristics of the power storage unit 120 are combined. In the figure, the horizontal axis represents the active power (unit: [%]) indicating the input / output of the power storage system 100C, and the vertical axis represents the efficiency (unit: [%]) obtained by dividing the output power by the input power. .. Since the power conversion efficiency of the power conversion unit PCS and the charge / discharge efficiency of the power storage unit 120 have a trade-off relationship, when these two index values having a trade-off relationship are regarded as the unit efficiency, FIG. 13 shows. In the efficiency characteristics as shown, the efficiency becomes the maximum E _{MPP at} a certain input / output value MPP (Max Power Point). _{The input / output value MPP} that takes the maximum efficiency E MPP is not limited to one point, and may exist in a plurality of points. _{Further, the maximum efficiency EMPP} may be constant in a certain range of input / output values (for example, a numerical range such as 30 to 70%). Information indicating the efficiency characteristics of the unit as illustrated in FIG. 13 may be stored in advance in the storage unit 113.

In the control unit 112, for example, each electric power depends on how much the input / output value MPP at which the efficiency of the unit is the maximum efficiency _EMPP and the input / output value assumed when the power conversion unit PCS is operated deviate from each other. Determines the priority of the conversion unit PCS. For example, the control unit 112 derives the degree of deviation between these input / output values as the deviation Def_MPP shown in the following mathematical formula (2).

In the formula, Q _ref (i) represents the power consumption of _{each power conversion unit PCS i} assumed when the invalid power is output. This power consumption _Qref (i) may be theoretically derived when designing the circuit of the power storage system 100C in advance, or may be actually measured during a test operation. Further, theoretically, since no energy loss occurs when the invalid power is output, the power consumption _QRef (i) may be the power consumption peculiar to the circuit that does not depend on the output amount of the negative power or the like. ..

As shown in Equation (2), the control unit 112, the output value (active power value) MPP, active power _{P ref} (i) and power _{Q ref} (i) and of which the output to the power conversion unit PCS _i The absolute value of the value obtained by subtracting the sum is derived as the deviation Def_MPP. At this time, _{the code of the active power Pref} (i) is positive in the case of charging the power storage unit 120 and negative in the case of discharging.

The control unit 112 determines the priority order of each power conversion unit PCS according to the value of the derived deviation Def_MPP. For example, the power conversion unit PCS having a smaller deviation Def_MPP value is set to have a higher priority when deciding as an output target of invalid power, and the power conversion unit PCS having a larger deviation Def_MPP value is an output target of invalid power. Set a low priority when deciding as. As a result, for example, when the efficiency of the unit _{drops by a certain value (for example, 10%) or more from the maximum efficiency EMPP} when the invalid power is output, the power conversion unit PCS is not targeted for the output of the invalid power. , Etc. can be performed.

Next, the control unit 112 performs one power conversion to be processed from among _{the plurality of power conversion units PCS 1} to PCS _N based on the priority of each power conversion unit PCS determined based on the efficiency of the unit. In order _{to select the part PCS i and erase the previous processing result (to clear zero), the value Qref_temp} (0) tentatively calculated as the total amount of invalid power output from the entire power storage system 100 is set to zero. (Step S402). As a result, from among the plurality of power conversion units PCS ₁ to PCS _N , for example, the power conversion unit PCS capable of maintaining the efficiency of the unit in a higher state even if the invalid power is output is preferentially selected. NS.

Since the following processes S404 to S434 are the same as the processes S202 to S232 in the flowchart of FIG. 6 described above, the description thereof will be omitted.

According to the fourth embodiment described above, as in the first to third embodiments, the power conversion unit PCS determined as the target for outputting the active power is also operated by outputting the invalid power. The number of power conversion units PCS to be generated can be reduced. As a result, it is possible to suppress output fluctuations of the power system EPS, achieve high-efficiency operation, and extend the service life.

Further, according to the fourth embodiment described above, in order to determine the power conversion unit PCS to be output of the invalid power based on the priority order based on the efficiency of the unit including the power conversion unit PCS and the power storage unit 120. , Further high efficiency operation can be achieved.

(Fifth Embodiment)
Hereinafter, the power storage system 100D according to the fifth embodiment will be described. In the power storage system 100D according to the fifth embodiment, the power conversion unit PCS to be output of the invalid power is determined based on both the charging needs and the efficiency of the unit including the power conversion unit PCS and the power storage unit 120. Therefore, it is different from the first to fourth embodiments. Hereinafter, the differences from the first to fourth embodiments will be mainly described, and the points common to the first to fourth embodiments will be omitted. In the description of the fifth embodiment, the same parts as those of the first to fourth embodiments will be described with the same reference numerals.

FIG. 14 is a flowchart showing a flow of a series of processes by the control unit 112 in the fifth embodiment. In this flowchart, for example, the discharge power command value is received by the communication unit 111, and the control unit 112 determines the power conversion unit PCS to be output of the active power from among the _{plurality of power conversion units PCS 1} to PCS _N. It is performed later (after the active power command value Pref (i) is assigned to the power conversion unit PCS).

First, the control unit 112 in the fifth embodiment derives charging needs for each power storage unit 120 based on the power storage state of the power storage unit 120 detected by the detection unit 130 and the deterioration characteristics of the power storage unit 120. Step S500).

Next, the control unit 112 determines the priority order for determining each of the _{plurality of power conversion units PCS 1} to PCS _N as an output target of the invalid power based on the charging needs derived for each power storage unit 120. (Step S502).

Next, the control unit 112 invalidates each of the _{plurality of power conversion units PCS 1} to PCS _N based on the efficiency of the unit based on the power conversion efficiency of the power conversion unit PCS and the charge / discharge efficiency of the power storage unit 120. The priority order for determining the power output target is determined (step S504).

Next, the control unit 112 sets the priority determined in the process of S502 (hereinafter referred to as the first priority α) and the priority determined in the process of S504 (hereinafter referred to as the second priority β). Based on this, one power conversion unit PCS _i to be processed is selected (step S506). For example, the control unit 112 treats the first priority α _i and the second priority β _{i of the power conversion unit PCS i} as weights, respectively, and power conversion having a large _{addition value (α i} + β _{i) of these weights.} It may be preferentially selected from the part PCS _i.

Further, the control unit 112 may change the degree of contribution of _{the weight α i} and the weight β _i according to the order of processing in the flowchart. For example, in the flowchart, the control unit 112 sets _{the contribution of the weight β i} determined in the process of S504 executed later to a predetermined value X, and sets the contribution of the weight β i to a predetermined value X, and in the process of S502 executed before the process of S504. The determined _{contribution of α i} may be (X-1). That is, the control unit 112 may cause a bias in the priority order in each process by _{setting the weight of each power conversion unit PCS i} to ((X-1) α _i + Xβ _i).

_{Further, in the processing of S506, the control unit 112 tentatively calculates a value Qref_temp} (0) as the total amount of invalid power output from the entire power storage system 100 in order to erase the previous processing result (to clear to zero). ) To zero.

Since the following processes S508 to S538 are the same as the processes S202 to S232 in the flowchart of FIG. 6 described above, the description thereof will be omitted.

In the above-mentioned flowchart, the order of the processing of S500 and S502 and the processing of S504 may be reversed. In this case, for example, the control unit 112 may set _{the weight of each power conversion unit PCS i} to ((X) α _i + (X-1) β _i ).

According to the fifth embodiment described above, as in the first to fourth embodiments, the power conversion unit PCS determined as the target for outputting the active power is also operated by outputting the invalid power. The number of power conversion units PCS to be generated can be reduced. As a result, high-efficiency operation and long life can be achieved.

Further, according to the fifth embodiment described above, the power conversion unit to which the invalid power is output is based on both the first priority α based on the charging needs and the second priority β based on the efficiency of the unit. Since the PCS is determined, more efficient operation can be achieved.

According to at least one embodiment described above, the plurality of power storage units 120-1 to 120-N for storing electric power and the plurality of power storage units 120-1 to 120-N are provided corresponding to each of the plurality of power storage units 120-1 to 120-N. Control that determines the amount of active power and invalid power in the AC power output by the power conversion unit PCS that converts the DC power from the power storage unit 120 into AC power and outputs it to the power system EPS, and the AC power output by the power conversion unit PCS. and parts 112 includes a control unit 112, preferentially a predetermined condition is satisfied power conversion unit PCS from a plurality of the power converter PCS ₁ in PCS _N, determines the power conversion unit PCS to output reactive power As a result, the power conversion unit PCS determined as the target for outputting the active power also outputs the invalid power, so that the number of the power conversion unit PCS to be operated can be reduced. As a result, for example, the semiconductor element of the power conversion unit PCS that is not in operation can be gated off, so that power leakage on the power storage unit 120 side, which is a DC power source, can be minimized. As a result, it is possible to suppress output fluctuations of the power system EPS, achieve high-efficiency operation, and extend the service life.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... Power system, 100 ... Power storage system, 110 ... Power storage controller, 111 ... Communication unit, 112 ... Control unit, 113 ... Storage unit, 120 ... Power storage unit, 130 ... Detection unit, PCS ... Power conversion unit, 200 ... Power generation system , 300 ... Power receiving equipment, 400 ... External controller, EPS ... Power system, TF ... Transformer

Claims (3)

Multiple power storage units that store power,
A power conversion unit provided corresponding to each of the plurality of power storage units, which converts DC power from the power storage unit into AC power and outputs the power to the power system.
A control unit for determining the respective amounts of active power and ineffective power in the AC power output by the power conversion unit is provided.
Among the plurality of power conversion units, the control unit preferentially determines the power conversion unit that is the target for outputting the active power to the power system as the power conversion unit that outputs the ineffective power.
Power storage system. Multiple power storage units that store power,
A power conversion unit provided corresponding to each of the plurality of power storage units, which converts DC power from the power storage unit into AC power and outputs the power to the power system.
A control unit for determining the respective amounts of active power and ineffective power in the AC power output by the power conversion unit is provided.
The control unit
Among the plurality of power conversion units, the first power conversion unit, which is the target for outputting the active power to the power system, is preferentially determined as the power conversion unit for outputting the ineffective power.
When the determined negative power amount exceeds the amount of invalid power that can be output by the first power conversion unit, the power system is not a target for outputting the active power among the plurality of power conversion units. 2 The power conversion unit is determined to be the power conversion unit that outputs the invalid power.
The first power conversion unit and the second power conversion unit determined by the power conversion unit that outputs the ineffective power are made to output the ineffective power that can be output to the maximum.
Power storage system. Further, a detection unit for detecting the storage state of each of the plurality of power storage units is provided.
The control unit
Based on the power storage state detected by the detection unit for each power storage unit and the deterioration characteristics of the power storage unit, an index value based on the necessity of charging of each power storage unit is derived.
Among the plurality of power conversion units, the power conversion unit connected to the power storage unit whose derived index value is smaller than that of the other power storage units is preferentially output to the power conversion unit. Decide or
The sum of the active power to be output to the power conversion unit and the power consumption when the ineffective power is output by the power conversion unit is derived.
The active power derived from the power output by the power conversion unit at the maximum efficiency in the third efficiency characteristic that combines the power conversion efficiency characteristics of the power conversion unit and the charge / discharge efficiency characteristics of the power storage unit. Based on the deviation obtained by subtracting the sum of the power consumption and the power consumption, the power conversion unit that preferentially outputs the ineffective power is determined from the plurality of power conversion units.
The power storage system according to claim 1 or 2.

Images