JP7761882B2 - Power Control Device - Google Patents

Description

The present invention relates to a power control device that controls the charging and discharging of a storage battery.

The basic electricity charge contracted between an electric power company and an electric power consumer is determined based on the maximum demand value over the past year. The maximum demand value refers to the average power consumption over a 30-minute period. Therefore, electric power consumers calculate the predicted demand value for the demand period based on power consumption trends, and if the predicted demand value is expected to exceed the base value for the basic charge, they adjust the load and take measures to reduce power consumption.

Furthermore, in recent years, as renewable energy sources are connected to the grid, the demand side is also required to change demand in response to sudden changes in grid output (a process known as demand response). For example, if a solar power generation forecast proves incorrect and the sky turns cloudy, supply will be insufficient, requiring the demand side to reduce demand (a process known as downward demand response). In such cases, the demand value, which was previously set with the aim of lowering the basic charge, must be lowered to the downward demand value for a certain period of time. In such cases, the demand value is not only used to calculate the basic charge, but is also used as a value for downward demand, and measures to reduce power consumption are taken.

For example, Patent Document 1 discloses a battery control system that controls the discharge of power stored in a battery system of a consumer that is a target for demand cutting so that the cumulative received amount of grid power from the start of each demand cutting period (hereinafter, DC period) of the consumer that is the target of demand cutting does not exceed a predetermined target value within each DC period. The system includes a data storage unit that records a first reference received amount, which serves as a criterion for determining whether or not to discharge the battery system, for the cumulative received amount for each elapsed time from the start of each DC period for each first unit time that is an even division of the length of the DC period; a data communication unit that transmits and receives data to and from the battery system; and a data communication unit that transmits and receives data to and from the battery system. The system determines, for each first unit time, the magnitude relationship between the cumulative received amount and the first reference received amount based on received power amount data indicating the cumulative received power amount from the start of the DC period to the elapsed time, and determines whether or not the cumulative received power amount is greater than the first reference received amount. and a battery control unit that transmits discharge command data to the battery system via the data communication unit when it determines that the received power amount is equal to or exceeds the quasi-received power amount. During each DC period, the first reference received power amount is set to monotonically increase from a lower limit to an upper limit as the elapsed time increases for each first unit time. If the target integrated received power amount is defined as the integrated received power amount that increases linearly from 0% to 100% of the target value as the elapsed time increases from the start to the end of the DC period, the difference obtained by subtracting the first reference received power amount from the target integrated received power amount monotonically increases during a first initial period from the start of each DC period until a predetermined time has elapsed, reaches a maximum positive value at the end of the first initial period, and monotonically decreases from the end of the first initial period until the first reference received power amount reaches the upper limit.

Japanese Patent Application Laid-Open No. 2020-167756

As such, conventionally, battery discharge control is performed during demand cut periods to maintain demand values. However, the issue of minimizing battery capacity by charging during demand cut periods has not been disclosed.

The present invention was made in consideration of the above circumstances, and aims to minimize the rechargeable battery capacity required to control power demand below the power demand by efficiently charging the storage battery.

In order to solve the above problems, an embodiment of the present invention has the following configurations 1 to n.
[Item 1]
A power control device that controls charging and discharging of a storage battery installed in a consumer facility of a power system via a power conversion device,
a communication unit that receives power measured at a power receiving point where power is input from a power grid;
a processor that controls the power conversion device to perform charge/discharge control for the storage battery in a first period, acquires and holds power for each second period that is shorter than the first period, and holds a maximum demand value;
Equipped with
The processor:
A first predicted power (W1) at time t3, which is the end of the current first period (P1a), is calculated using the following formula:
where t2 denotes the current time, P2 denotes the power measured at t2, t1 denotes a time after the beginning of the current first period and ahead of t2, and P1 denotes the power measured at t1;
Calculating the statistical variation of the power acquired in the second period measured in the current first period (P1a);
calculating a corrected predicted power at time t3 by adding the first predicted power and the statistical variation;
When the corrected predicted power exceeds the maximum demand value, the power control device outputs a control instruction to the storage battery to discharge the power.
[Item 2]
2. The power control device according to claim 1, wherein the discharge power to the storage battery is a value obtained by subtracting the maximum demand value from the corrected predicted power.
[Item 3]
If the corrected predicted power does not exceed the maximum demand value, a second predicted power (W2) at time t3, which is the end of the current first period (P1a), is calculated using the following formula:
where t4 denotes the start time of the current first period, P4 denotes the power measured at t4,
3. The power control device according to claim 1, wherein the power control device outputs a control instruction to the storage battery to discharge power obtained by subtracting the statistical variation and the second predicted power from the maximum demand value.
[Item 4]
4. The power control device according to any one of items 1 to 3, wherein the statistical variation is a standard deviation.

According to the present invention, by efficiently discharging the storage battery, it is possible to minimize the rechargeable battery capacity required to maintain power below demand.

1 is a diagram illustrating the overall configuration of a power control device according to an embodiment of the present invention; FIG. 2 is a diagram illustrating details of a power control device according to an embodiment of the present invention. 3 is a diagram illustrating discharge control to a rechargeable battery by a power control device according to an embodiment of the present invention. FIG. 3 is a diagram illustrating charging control of a rechargeable battery by a power control device according to an embodiment of the present invention. FIG. 3 is a power control flowchart of a power control device according to an embodiment of the present invention. 10 is a graph showing power consumption in conventional control. 10 is a graph showing changes in power consumption in conventional control. 1 is a power consumption graph with general demand control. 1 is a graph showing changes in power consumption with general demand control. 10 is a graph showing power consumption when demand control according to the present invention is performed. 1 is a graph showing changes in power consumption according to the present invention.

The power control device according to this embodiment will be explained below using Figures 1 to 6.

1. Configuration of the Power Control Device Fig. 1 is a diagram illustrating the overall configuration of a power control device and other devices according to one embodiment of the present invention. Power equipment 11 of a consumer 7 includes a power receiving point 12 connected to an external power system (system) 10, a transformer facility 13, a load 14, a storage battery 15, a power conversion device 16 for the storage battery, and a power control device 20. The power control device 20 is connected by communication so as to receive received power data from a power detection sensor 161 connected to the power receiving point 12. The power control device 20 is also connected by communication with the power conversion device 16 and the storage battery 15.

A power conversion device 16 is provided for each storage battery 15, and performs AC-DC conversion of the power used to charge the storage battery 15, or DC-AC conversion of the power output by discharging the storage battery 15. The power conversion device 16 has a circuit including switching elements, and although it is connected to the storage battery 15 via DC, it performs DC-AC conversion by boosting the DC to a predetermined voltage and converting it to AC, and also performs the reverse operation of AC-DC conversion.

The storage battery 15 is a stationary storage battery installed in consumer equipment or a battery in an electric vehicle. It stores the power input during charge control and discharges the stored power for output. The storage battery 15 includes, for example, secondary batteries such as lithium-ion batteries, lead-acid batteries, and nickel-metal hydride batteries. The storage battery 15 includes a battery management unit that monitors the remaining battery charge and transmits battery status information (voltage, SOC, etc.) to the power control device 20.

Figure 2 is a diagram illustrating the configuration of a power control device. The power control device 20 may be configured as a computer device including a processor 22, memory 24, a communication unit 26, storage 28, and a bus 29. Each device is connected by the bus 29 for communicating information.

The processor 22, for example, runs an operating system to control the entire computer. The processor 22 may be configured as a central processing unit (CPU) including interfaces with peripheral devices, a control unit, an arithmetic unit, registers, etc. The processor 22 also reads programs (program code), software modules, and data from the storage 28 and/or the communication unit 26 into the memory 24 and executes various processes in accordance with these. The program used is a program that causes the computer to execute at least some of the operations described in the above embodiments. For example, each functional unit of the power control device 20 may be implemented by a control program stored in the memory 24 and executed by the processor 22, and similar programs may be implemented for other functional blocks. The program may also be transmitted from a network via a telecommunications line.

Memory 24 is a computer-readable recording medium and may be composed of, for example, at least one of ROM (Read Only Memory), EPROM (Erasable Programmable ROM), EEPROM (Electrically Erasable Programmable ROM), RAM (Random Access Memory), etc. Memory 24 may also be called a register, cache, main memory (primary storage device), etc. Memory 24 can store executable programs (program code), software modules, etc. for implementing a method according to one embodiment of the present invention.

Storage 28 is a computer-readable recording medium and may be composed of at least one of, for example, an optical disk such as a CD-ROM (Compact Disc ROM), a hard disk drive, a flexible disk, a magneto-optical disk (e.g., a compact disk, a digital versatile disk, a Blu-ray® disk), a smart card, flash memory (e.g., a card, a stick, a key drive), a floppy disk, a magnetic strip, etc. Storage 28 may also be referred to as an auxiliary storage device.

The communication unit 26 is hardware (transmission/reception device) for communicating between computers via a wired and/or wireless network, and is also referred to as, for example, a network device, network controller, network card, or communication module.

The power control device 20 may be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA).

2. Control Method of the Control Unit 2.1 Battery Discharge Control The discharge control of the rechargeable battery by the power control device will be explained using Figure 3.
In Figure 3, the vertical axis represents power at the receiving point, and the horizontal axis represents time. 200a represents power demand, which increases and decreases over time like a sine curve. DV is the received power, which indicates the demand value.

The power control device 20 controls the charging and discharging of the storage battery every first period P1. Here, the first period is a 30-minute time interval, which is the unit of time for trading electricity. Furthermore, the power control device 20 acquires electricity every time every second period P2, which is shorter than the first period, and stores the electricity in memory. The second period P2 is, for example, every minute. The maximum demand value is also stored in memory. Figure 6 will be explained using the first period (P1a) that is the target of calculation processing by the processor.

The processor 22 of the power control device 20 calculates the first predicted power (W1) at time t3, the end of the current first period (P1a), using the following formula:

Here, t2 denotes the current time, P2 denotes the power measured at t2, t1 denotes a time later than the start of the current first period and earlier than t2, and P1 denotes the power measured at t1.

Processor 22 calculates the statistical variance of the power acquired in the second period measured in the current first period (P1a), and calculates the corrected predicted power W3 at time t3 by adding the first predicted power and the statistical variance. If the corrected predicted power W3 exceeds the maximum demand value, processor 22 outputs a control instruction to the storage battery to discharge.

The statistical variation is, for example, the standard deviation σ, which is derived from the following number:

Here, n is the number of power values acquired in the second period, x is the power value acquired in the second period, and x bar is the average value of the power values acquired in the second period.

The discharge power to the storage battery is the corrected predicted power W3 minus the maximum demand value DM.

2.2 Battery Charging Control Method The charging control of the rechargeable battery by the power control device will be described with reference to Fig. 4. Note that in Fig. 4, the description of the same configuration as in Fig. 3 will be omitted.

If the corrected predicted power W3 does not exceed the maximum demand value, the processor 22 calculates the second predicted power (W2) at time t3, the end of the current first period (P1a), using the following formula:

Here, t4 denotes the start time of the current first period, and P4 denotes the power measured at t4.

If the value obtained by adding the second predicted power (W2) and the statistical variation is smaller than the maximum demand value, the processor outputs a control instruction to discharge the power obtained by subtracting the statistical variation and the second predicted power from the maximum demand value to the storage battery.

3. Power Control Flowchart The power control flowchart of the power control device will be described with reference to FIG.
In S101, the power control device 20 acquires the power for the second period of the current period (P1a) from the power detection sensor. Next, the processor 22 determines whether W3 is greater than or equal to the maximum demand value (S102). If W3 is greater than the maximum demand value (Y in S102), the processor 22 controls the storage battery to perform a discharge process (S103), and returns to the initial process (S101) via S201. If W3 is less than the maximum demand value (N in S102), the processor 22 proceeds to S111.

In S111, the processor 22 determines whether "W3 + σ" is smaller than the maximum demand DR. If "W3 + σ" is smaller than the maximum demand DR (Y in S112), the processor 22 controls the storage battery to perform charging processing (S112). If "W3 + σ" is greater than the maximum demand DR (N in S112), the process returns to S101. S201 returns to the initial process (S101).

An embodiment will be described below using Figures 6 to 8. Figure 6A is a power consumption graph without the control of the present invention, and Figure 6B is a power consumption change graph without the control of the present invention. Figure 7A is a power consumption graph with general demand control, and Figure 7B is a power consumption change graph with general demand control. Figures 6A and 7A show power usage, contracted power, target power, and power consumption. The power usage in Figure 6A is used by loads 1 to 3 in Figures 6B and 7B, respectively. Current demand control is predictive control, and in the unlikely event that power usage exceeds the forecast, it can only cut off predetermined loads and cannot respond to unexpected power increases. Furthermore, because it is predictive control, power cutting must be performed at a point with a sufficient margin above the contracted power, and depending on the forecast, it may not be possible to use enough power up to the contracted power, reducing convenience.

Figure 8A is a power consumption graph in which demand control according to the present invention is implemented, and Figure 8B is a power consumption change graph in accordance with the present invention. Figure 8A shows the power usage, contracted power, target power, and power consumption. The power usage in Figure 8A is used by loads 1 to 3 in Figure 8B, respectively. As shown in Figure 8A, battery discharge control is being performed without exceeding the demand value.

The embodiments described above are merely typical examples, and combinations, modifications, and variations of the components of each embodiment will be apparent to those skilled in the art. It is clear that those skilled in the art will be able to make various modifications to the above-described embodiments without departing from the principles of the present invention and the scope of the invention as set forth in the claims.

10 External power system 11 Power equipment 12 Power receiving point 15 Storage battery 16 Power conversion device 20 Power control device

Claims (3)

A power control device that controls charging and discharging of a storage battery installed in a consumer facility of a power system via a power conversion device,
a communication unit that receives power measured at a power receiving point where power is input from a power grid;
a processor that controls the power conversion device to perform charge/discharge control for the storage battery in a first period, acquires and holds power for each second period that is shorter than the first period, and holds a maximum demand value;
Equipped with
The processor:
A first predicted power (W1) at time t3, which is the end of the current first period, is calculated using the following formula:
where t2 denotes the current time, P2 denotes the power measured at t2, t1 denotes a time after the beginning of the current first period and ahead of t2, and P1 denotes the power measured at t1;
Calculating a statistical variation of the power acquired in the second period measured in the current first period;
calculating a corrected predicted power at time t3 by adding the first predicted power and the statistical variation;
When the corrected predicted power exceeds the maximum demand value, the power control device outputs a control instruction to the storage battery to discharge power obtained by subtracting the maximum demand value from the corrected predicted power . If the corrected predicted power does not exceed the maximum demand value, a second predicted power (W2) at time t3, which is the end of the current first period, is calculated using the following formula:
where t4 denotes the start time of the current first period, P4 denotes the power measured at t4,
The power control device according to claim 1 , further comprising: a control instruction to charge the storage battery with power obtained by subtracting the statistical variation and the second predicted power from the maximum demand value. The power control device of claim 1 , wherein the statistical variation is a standard deviation.