JP6922800B2 - Storage battery system and its charge / discharge loss arithmetic unit - Google Patents

Description

The present invention relates to a storage battery system and a charge / discharge loss arithmetic unit thereof.

A storage battery system attached to a power generation facility of a power plant or a load facility of a factory is known. Patent Document 1 proposes a storage battery control method for suppressing output fluctuations and minimizing charge / discharge loss in renewable energy power generation in which the output fluctuates from moment to moment depending on the environment, season, weather, or the like.

Japanese Unexamined Patent Publication No. 2008-259357

Patent Document 1 is a system for minimizing charge / discharge loss of a storage battery, but is not a system capable of measuring charge / discharge loss at various parts of the storage battery system. In order to grasp the deterioration status of the storage battery, it is desired to be able to measure the charge / discharge loss of the storage battery system.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a storage battery system capable of measuring charge / discharge loss and a charge / discharge loss calculation device thereof.

In order to achieve the above object, the storage battery system according to the present invention is configured as follows.

The storage battery system includes an electric wire, a transformer, a power conditioning system (hereinafter, PCS), a storage battery, a first watt-hour meter, and a charge / discharge loss calculation unit.

The electric wire is connected to the power generation equipment or the load equipment outside the storage battery system. The primary side of the transformer is connected to the electric wire. The PCS is connected to the secondary side of the transformer. The storage battery is connected to the PCS. At least one storage battery is arranged, and when a plurality of storage batteries are arranged, they are arranged in parallel. The PCS has a charging function that converts the AC power input from the secondary side of the transformer into DC power to charge the storage battery, and converts the DC power of the storage battery into AC power and outputs it to the secondary side of the transformer. It has a discharge function.

The first watt hour meter is connected to the electric wire and the primary side of the transformer. The first watt-hour meter has a total electric energy in the charging direction from the electric wire to the storage battery (charging electric energy) and a total electric energy in the discharging direction from the storage battery to the electric wire (discharged electric energy) between the electric wire and the primary side of the transformer. Amount) is measured respectively. The charge / discharge loss calculation unit subtracts the value obtained by dividing the discharge power amount measured by the first watt-hour meter by the charge power amount from 1 during the measurement period in which the SOC of the storage battery is the same at the start and end of the measurement. Then, the charge / discharge loss of the storage battery system is calculated.

Preferably, the storage battery system further comprises a second watt hour meter. The second watt hour meter is connected to the secondary side of the transformer and the PCS. The second watt-hour meter measures the charge power amount and the discharge power amount, respectively, between the secondary side of the transformer and the PCS. In addition, the charge / discharge loss calculation unit subtracts the value obtained by dividing the discharge power measured by the second watt-hour meter by the charge power during the above measurement period from 1, and the charge / discharge loss of the storage battery system excluding the trans loss. Is calculated.

Preferably, the battery system further comprises a third watt hour meter. The third watt hour meter is connected to the PCS and the storage battery. The third watt-hour meter measures the charge power amount and the discharge power amount, respectively, between the PCS and the storage battery. In addition, the charge / discharge loss calculation unit calculates the storage battery loss by subtracting the value obtained by dividing the discharge power amount measured by the third watt-hour meter in the measurement period by the charge power amount from 1.

Further, in order to achieve the above object, the charge / discharge loss arithmetic unit of the storage battery system according to the present invention is configured as follows.

The charge / discharge loss calculation device includes a first watt hour meter and a charge / discharge loss calculation unit. The first watt-hour meter measures the charge power amount and the discharge power amount, respectively, between the electric wire connected to the outside of the storage battery system and the primary side of the transformer connected to the electric wire. The charge / discharge loss calculation unit is the discharge measured by the first watt-hour meter during the measurement period in which the SOC of the storage battery connected to the secondary side of the transformer via the PCS is the same at the start of measurement and at the end of measurement. The storage battery system charge / discharge loss is calculated by subtracting the value obtained by dividing the electric energy by the electric energy for charging from 1.

Preferably, the charge / discharge loss arithmetic unit further includes a second watt hour meter. The second watt-hour meter measures the charge power amount and the discharge power amount, respectively, between the secondary side of the transformer and the PCS connected to the secondary side. In addition, the charge / discharge loss calculation unit subtracts the value obtained by dividing the discharge power measured by the second watt-hour meter by the charge power during the above measurement period from 1, and the charge / discharge loss of the storage battery system excluding the trans loss. Is calculated.

Preferably, the charge / discharge loss arithmetic unit further includes a third watt hour meter. The third watt-hour meter measures the charge power amount and the discharge power amount, respectively, between the PCS and the storage battery connected to the PCS. In addition, the charge / discharge loss calculation unit calculates the storage battery loss by subtracting the value obtained by dividing the discharge power amount measured by the third watt-hour meter in the measurement period by the charge power amount from 1.

According to the storage battery system according to the present invention and the charge / discharge loss calculation device thereof, the charge / discharge loss of the storage battery system can be measured. Transformers and PCS have little deterioration over time, whereas storage batteries deteriorate due to repeated charging and discharging. Due to the increase in resistance due to deterioration, heat generation increases and loss increases. By periodically measuring and comparing the charge / discharge loss of the storage battery system, the deterioration status of the storage battery can be grasped.

It is a figure for demonstrating the structure of the storage battery system which concerns on Embodiment 1 of this invention. It is a figure for demonstrating the control image of the storage battery system attached to the solar power generation facility. It is a figure for demonstrating the control image of the output fluctuation mitigation measure by a storage battery system, and the concept of charge / discharge loss. It is a figure which shows an example of charge / discharge loss in each part of a storage battery system.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The elements common to each figure are designated by the same reference numerals, and duplicate description will be omitted.

Embodiment 1.
(Configuration of storage battery system)
FIG. 1 is a diagram for explaining a configuration of a storage battery system according to a first embodiment of the present invention.

The storage battery system 1 attached to the power generation equipment of the power plant and the load equipment of the factory includes an electric wire 2, a transformer 3, a power conditioning system (hereinafter, PCS) 4, a storage battery 5, a storage battery monitoring unit (BMU) 6, and charge / discharge loss. A computing device 10 is provided.

The electric wire 2 is connected to an external power generation facility or load facility of the storage battery system 1. The primary side of the transformer 3 is connected to the electric wire 2. The PCS 4 is connected to the secondary side of the transformer 3. The storage battery 5 is connected to the PCS 4. Although three storage batteries 5 arranged in parallel are drawn in FIG. 1, the number of storage batteries 5 is not limited to this, and at least one may be used. The storage battery monitoring unit 6 is connected to the storage battery 5.

The PCS4 has a charging function of converting the AC power output to the electric wire 2 by the power generation facility into DC power and charging the storage battery 5, and a discharging function of converting the DC power of the storage battery 5 into AC power and discharging the electric power to the electric wire 2. Be prepared.

The storage battery 5 may be composed of a single storage battery cell, or may be configured as an aggregate of a plurality of storage battery cells. As the type of storage battery, a large-capacity storage battery such as a lithium ion battery, a sodium-sulfur battery, or a nickel-metal hydride battery is preferable.

The storage battery monitoring unit 6 monitors the state of the storage battery 5. The monitoring items are, for example, state quantities such as current, voltage, and temperature. The storage battery monitoring unit 6 constantly monitors the state quantity, which is a monitoring item, with a sensor. The constant monitoring in the present embodiment is a concept including not only an operation of continuously capturing a continuous signal from a sensor but also an operation of capturing a sensor signal in a predetermined short cycle. The storage battery monitoring unit 6 outputs a part or all of the obtained information to the charge / discharge loss arithmetic unit 10 as storage battery information.

(Configuration of charge / discharge loss arithmetic unit)
The charge / discharge loss calculation device 10 includes a first watt hour meter 11, a second watt hour meter 12, a third watt hour meter 13, and a charge / discharge loss calculation unit 14.

The first watt hour meter 11 is connected to the electric wire 2 and the primary side of the transformer 3. The second watt hour meter 12 is connected to the secondary side of the transformer 3 and the PCS 4. The third watt hour meter 13 is connected to the PCS 4 and the storage battery 5. The charge / discharge loss calculation unit 14 is connected to the first watt hour meter 11, the second watt hour meter 12, the third watt hour meter 13, and the storage battery monitoring unit 6.

The first watt hour meter 11 has a total electric energy (charging electric energy) in the charging direction from the electric wire 2 to the storage battery 5 and a discharge from the storage battery 5 to the electric wire 2 between the electric wire 2 and the primary side of the transformer 3. Measure the total electric energy (discharge electric energy) in each direction. The first watt-hour meter 11 outputs the measured charge power amount and discharge power amount to the charge / discharge loss calculation unit 14.

The second watt-hour meter measures the charge power amount and the discharge power amount, respectively, between the secondary side of the transformer 3 and the PCS4. The second watt-hour meter 12 outputs the measured charge power amount and discharge power amount to the charge / discharge loss calculation unit 14.

The third watt-hour meter measures the charge power amount and the discharge power amount, respectively, between the DC side of the PCS 4 and the storage battery 5. The third watt hour meter 13 outputs the measured charge power amount and discharge power amount to the charge / discharge loss calculation unit 14.

Each of the first watt-hour meter 11 to the third watt-hour meter 13 may be composed of one watt-hour meter or a plurality of watt-hour meters.

The charge / discharge loss calculation unit 14 executes various calculation processes (programs) based on an input / output interface for inputting / outputting various information, a memory for storing various information, initial settings, programs, calculation results, etc., and various information and initial settings. It has a possible processor. The processing of the charge / discharge loss calculation unit 14 will be described later.

(Control image of output fluctuation mitigation measures by storage battery system and charge / discharge loss)
The storage battery system 1 attached to the power generation equipment of the power plant or the load equipment of the factory charges or discharges according to the supply and demand of these equipments. As an example, it is assumed that the power generation facility is a photovoltaic (PV: Photovoltaics) power generation facility connected to the grid for selling power. When connecting the photovoltaic power generation equipment and the storage battery system 1 to the electric power system, control satisfying a predetermined constraint condition is required. The control that satisfies a predetermined constraint condition is, for example, the control shown in FIG. 2 that alleviates the output fluctuation per unit time in order to suppress an adverse effect on the power system, and the specified storage battery after sunset to prevent deterioration of the storage battery. It is a control that discharges until the remaining amount (SOC) is reached. Such control is executed by a control device (not shown) including the charge / discharge loss calculation device 10 of FIG. 1 or a separate control device (not shown).

FIG. 3 is a diagram for explaining a control image of measures for mitigating output fluctuations by the storage battery system and the concept of charge / discharge loss.

FIG. 3 (1) shows the time change of the original PV power generated by the photovoltaic power generation facility without any restrictions. Area A shows the amount of PV power generated in a certain day.

As described above, it is necessary to satisfy a predetermined constraint condition in order to connect to the power system. As an example of the constraint conditions for selling power, the output fluctuation and the upper limit power per unit time to the power system are defined. The area a in (2) of FIG. 3 represents the amount of charging power. This means that the storage battery 5 is charged with the excess amount of PV generated power in order to satisfy the above-mentioned constraint condition. Region b represents the amount of discharge power. This means that the shortage of PV generated power is discharged from the storage battery 5 in order to satisfy the above-mentioned constraint condition. Further, in the storage battery system attached to the photovoltaic power generation, the start SOC and the end SOC of the day are controlled in the same manner in order to prevent the storage battery 5 from deteriorating. Therefore, in FIG. 3 (2), the battery is discharged after sunset.

Area B in FIG. 3 (3) shows the amount of power sold. The electric energy sold (region B) is a value obtained by adding the discharge electric energy (region b) to the original PV generated electric energy (region A) and subtracting the charging electric energy (region a). This "discharge power amount (region b) -charge power amount (region a)" means the charge / discharge loss generated by the charge / discharge of the storage battery 5.

(Function of charge / discharge loss calculation unit)
The charge / discharge loss calculation unit 14 according to the present invention automatically calculates this charge / discharge loss.

The charge / discharge loss calculation unit 14 inputs the charge power amount and the discharge power amount from the first watt-hour meter 11 to the third watt-hour meter 13. Further, the charge / discharge loss calculation unit 14 inputs storage battery information from the storage battery monitoring unit 6. The charge / discharge loss calculation unit 14 estimates the SOC (State Of Charge) of the storage battery 5 from the storage battery information. Any method can be applied to estimate the SOC. As an example, there is a method of setting an initial value of SOC and then estimating SOC by integrating charge / discharge currents.

As described above, in the storage battery system with photovoltaic power generation, the start SOC and the end SOC of the day are controlled in the same way. The charge / discharge loss calculation unit 14 performs the following calculation with the measurement period from the start of measurement by the watt-hour meter until the SOC becomes the same as the SOC at the start of measurement.

The charge / discharge loss calculation unit 14 calculates the value obtained by dividing the discharge power amount measured by the first watt-hour meter 11 by the charge power amount during the measurement period in which the SOC of the storage battery 5 is the same at the start and end of the measurement. Subtract from 1 to calculate the storage battery system charge / discharge loss. In the example shown in FIG. 4, when the charge power amount measured by the first watt-hour meter 11 is 100, the discharge power amount is 92. In this case, the storage battery system charge / discharge loss can be evaluated as 1-92 / 100 = 0.08, that is, 8%. The storage battery system charge / discharge loss includes a transformer loss of the transformer 3, a conversion loss of the PCS 4, and a storage battery loss of the storage battery 5.

The charge / discharge loss calculation unit 14 subtracts the value obtained by dividing the discharge power amount measured by the second watt-hour meter 12 by the charge power amount from 1 in the above measurement period to obtain the charge / discharge loss of the storage battery system excluding the trans loss. calculate. In the example shown in FIG. 4, the charge power amount measured by the second watt-hour meter 12 is 99, and the discharge power amount is 93. In this case, the charge / discharge loss of the storage battery system excluding the trans loss can be evaluated as 1-93 / 99≈0.06, that is, about 6%. The storage battery system charge / discharge loss excluding the trans loss includes the conversion loss of the PCS 4 and the storage battery loss of the storage battery 5.

The charge / discharge loss calculation unit 14 calculates the storage battery loss by subtracting the value obtained by dividing the discharge power amount measured by the third watt hour meter 13 by the charge power amount from 1 in the measurement period. In the example shown in FIG. 4, the charge power amount measured by the third watt hour meter 13 is 97, and the discharge power amount is 95. In this case, the storage battery loss can be evaluated as 1-95 / 97≈0.02, that is, about 2%.

The charge / discharge loss calculation device 10 automatically calculates these charge / discharge losses periodically and accumulates the calculation results.

(effect)
As described above, according to the charge / discharge loss calculation device 10, the charge / discharge loss can be measured by measuring the total discharge power amount and the total charge power amount using a watt-hour meter at various places in the storage battery system 1. be. While the transformer 3 and the PCS 4 have little deterioration over time, the storage battery 5 deteriorates due to repeated charging and discharging. Due to the increase in resistance due to deterioration, heat generation increases and loss increases. By automatically calculating and comparing the charge / discharge loss of the storage battery 5 on a regular basis, the deterioration status of the storage battery can be grasped. In addition, by using it in a storage battery system with renewable energy for the purpose of selling electricity, it is possible to obtain measured data of charge / discharge loss, so that it is possible to predict the amount of electricity sold with high accuracy. In addition, it is possible to predict the amount of electricity sold with high accuracy from the change tendency of the accumulated actual measurement data.

(Modification example)
By the way, in the system of the first embodiment described above, the configuration in which the charge / discharge loss arithmetic unit 10 includes the first watt-hour meter 11 to the third watt-hour meter 13 has been described, but the present invention is not limited thereto. .. For example, the configuration may not include any one watt-hour meter and arithmetic processing based on the measured value thereof. Further, the configuration may not include any two watt-hour meters and arithmetic processing based on the measured values.

Further, in the system of the first embodiment described above, the solar power generation equipment has been described as an example of the power generation equipment attached to the storage battery system, but the present invention is not limited to this. It may be a power generation facility using other renewable energy, or a power generation facility using fossil energy or nuclear energy. Further, the storage battery system may be installed in a load facility such as a factory in place of the power generation facility or together with the power generation facility.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be variously modified and implemented without departing from the spirit of the present invention.

A Original PV power generation amount B Selling power amount a Charging power amount b Discharging power amount 1 Storage battery system 2 Electric wire 3 Transformer 4 Power conditioning system (PCS)
5 Storage battery 6 Storage battery monitoring unit 10 Charge / discharge loss calculation device 11 1st watt-hour meter 12 2nd watt-hour meter 13 3rd watt-hour meter 14 Charge / discharge loss calculation unit

Claims (6)

Electric wires connected to power generation equipment or load equipment,
A transformer whose primary side is connected to the electric wire,
A power conditioning system (hereinafter referred to as PCS) connected to the secondary side of the transformer,
With at least one storage battery connected to the PCS,
A first watt-hour meter that measures the amount of charging power and the amount of discharging power between the electric wire and the primary side of the transformer.
The storage battery system is obtained by subtracting the value obtained by dividing the discharge power amount measured by the first watt-hour meter by the charge power amount from 1 in the measurement period in which the SOC of the storage battery is the same at the start of measurement and the end of measurement. The charge / discharge loss calculation unit that calculates the charge / discharge loss,
A storage battery system characterized by being equipped with. Further, a second watt-hour meter for measuring the charge power amount and the discharge power amount is further provided between the secondary side of the transformer and the PCS.
The charge / discharge loss calculation unit further
To calculate the storage battery system charge / discharge loss excluding the trans loss by subtracting the value obtained by dividing the discharge power amount measured by the second watt hour meter by the charge power amount in the measurement period from 1.
The storage battery system according to claim 1. A third watt-hour meter for measuring the amount of charging power and the amount of discharging power is further provided between the PCS and the storage battery.
The charge / discharge loss calculation unit further
To calculate the storage battery loss by subtracting the value obtained by dividing the discharge electric energy measured by the third watt-hour meter by the charging electric energy in the measurement period from 1.
The storage battery system according to claim 1 or 2. It is a charge / discharge loss arithmetic unit of the storage battery system.
A first watt-hour meter that measures the amount of charge power and the amount of discharge power between the electric wire connected to the outside of the storage battery system and the primary side of the transformer connected to the electric wire.
The SOC of the storage battery connected to the secondary side of the transformer via the power conditioning system (hereinafter referred to as PCS) is measured by the first watt hour meter during the measurement period in which the SOC is the same at the start of measurement and at the end of measurement. A charge / discharge loss calculation unit that calculates the charge / discharge loss of the storage battery system by subtracting the value obtained by dividing the discharged power amount by the charging power amount from 1.
A charge / discharge loss arithmetic unit characterized by being equipped with. Further, a second watt-hour meter for measuring the charge power amount and the discharge power amount is further provided between the secondary side of the transformer and the PCS connected to the secondary side.
The charge / discharge loss calculation unit further
To calculate the storage battery system charge / discharge loss excluding the trans loss by subtracting the value obtained by dividing the discharge power amount measured by the second watt hour meter by the charge power amount in the measurement period from 1.
The charge / discharge loss arithmetic unit according to claim 4. A third watt-hour meter for measuring the charge power amount and the discharge power amount, respectively, is provided between the PCS and the storage battery connected to the PCS.
The charge / discharge loss calculation unit further
To calculate the storage battery loss by subtracting the value obtained by dividing the discharge electric energy measured by the third watt-hour meter by the charging electric energy in the measurement period from 1.
The charge / discharge loss arithmetic unit according to claim 4 or 5.

Images