Method for controlling charge and discharge of storage battery in power supply system

Abstract

To provide a charge / discharge control method for a storage battery in a power supply system having an emergency power supply function by the storage battery.SOLUTION: A charge / discharge control method for a storage battery in a power supply system in which a plurality of types of electrical facilities include an emergency load that operates during supply interruption of AC power and which includes: one or more transformers 12A to 13B that receive alternating current power from a power station or a substation and convert the power according to electrical facilities being loads; a plurality of switches SW1A to SW3B provided between the plurality of types of electrical facilities provided in an establishment to which power is to be supplied and the transformer; a power storage device 14 having a storage battery 41 that can be charged and discharged by AC power; battery state detection means that detects the state of the storage battery; and a system control device (EMS) 16 that controls charging and discharging operations of the plurality of switches and the power storage device.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for controlling charge and discharge of a storage battery in a power supply system having an emergency power supply function equipped with a storage battery, and particularly relates to a technique effective for use in controlling charge and discharge of a storage battery in a system for supplying power to electrical equipment in facilities used by an unspecified number of people such as railway stations and hospitals.

Background Art

[0002] Generally, as shown in FIG. 4, the power supply equipment in a railway station receives AC power supplied from a substation or the power grid of an electric power company through two lines, a normal line (high voltage No. 1) 11A and a standby line (high voltage No. 2) 11B, converts the voltage, and supplies power to electrical equipment such as lighting devices 21, outlets 22, ticket vending machines 23, ticket gates 24, elevators 25 such as escalators, and general power 26 such as air conditioners. In addition, in the railway station, there are installed induction lights 27A and fire fighting equipment (emergency load) 27B such as sprinklers.

[0003] On the other hand, in railway stations with a fire load defined by the Fire Service Act, it is obligatory to have an emergency power supply function that supplies power to emergency loads in the event of a fire in accordance with the provisions of the Fire Service Act. Also, in railway stations of a certain scale or more, they are required to have an emergency power supply function according to internal regulations. Therefore, conventionally, in railway stations of a certain scale or more, a generator (EG) 17 powered by an engine is installed as an emergency power supply, and when a power outage occurs, the power supply system is configured to supply power from the generator 17 to important loads such as ticket vending machines 23 and ticket gates 24 in addition to emergency loads such as induction lights 27A and fire fighting equipment 27B.

[0004] In addition, in the power supply system of the station building, when the power supply of the normal line 11A stops, it is necessary to switch to the standby line 11B and also switch to the power from the generator 17 during a power outage. Therefore, as shown in FIG. 4, switches SW1A, SW1B to SW5A, SW5B are provided on the load side. Among the above loads in the station building, lighting devices 21, outlets 22, etc. do not require urgency, so inexpensive electromagnetic power switches are used for switches SW1A, SW1B; SW3A, SW3B; SW5A, SW5B. On the other hand, ticket vending machines, ticket gates, etc. need to immediately switch the line and continue power supply when a power outage occurs. Conventionally, static switches that can switch instantaneously (SW2A, SW2B are 3 ms; SW4A, SW4B are 10 ms) have been used as power switches SW2A, SW2B; SW4A, SW4B.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, since static switches need to be provided for each load, the number of equipment points increases, and a lot of labor and time are required for maintenance and inspection. In addition, for the emergency generator, it is necessary to conduct a full-load test with a power outage of the entire station once a year, which requires labor for maintenance and inspection. Moreover, the emergency generator uses light oil, heavy oil, etc., and emits carbon dioxide, so there is a problem of having a large impact on the environment. Therefore, the inventors have considered using a storage battery and a solar power generation facility instead of the emergency generator.

[0007] Conventionally, in a power supply system that receives AC power from the power grid of an electric power company, is equipped with a power storage device and a renewable energy power generation device, and supplies power to general loads and important loads, there is an invention related to a power control device and a power control method that predict the power consumption of the load, calculate the target charge amount in the power storage device, and control the charging operation and discharging operation of the power storage device. For example, there is an invention described in Patent Document 1. In addition, an invention related to a battery state estimation device that estimates the charge rate of a storage battery based on the charge and discharge current of the storage battery and the voltage between the terminals of the storage battery has also been proposed (for example, Patent Document 2).

[0008] However, Patent Document 1 and Patent Document 2 do not disclose any technology for guaranteeing the supply of power to emergency loads in the event of a power outage or for achieving power leveling. The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for controlling the charge and discharge of a storage battery in a power supply system having an emergency power supply function capable of guaranteeing the supply of power to an emergency load in the event of a power outage by the storage battery. Another object of the present invention is to provide a method for controlling the charge and discharge of a storage battery capable of achieving power leveling in a power supply system equipped with an emergency power supply function by the storage battery.

Means for Solving the Problems

[0009] To achieve the above object, the present invention provides One or more transformers that receive the supply of AC power from a power plant or a substation and convert it according to the electrical equipment that becomes a load, A plurality of switches provided between a plurality of types of electrical equipment provided in the facility to be supplied with power and the transformer, A power storage device including a storage battery that can be charged and discharged by the AC power, Battery state detection means for detecting the state of the storage battery, A system control device that controls the switching operations of the plurality of switches and the charging and discharging operations of the power storage device, and in a power supply system including a plurality of types of electrical equipment that includes an emergency load that operates during interruption of the AC power supply, a method for controlling charging and discharging of a storage battery. The system control device Means for grasping the charging rate of the storage battery at the current time based on the battery state detected by the battery state detection means, and means for outputting a charging command for the storage battery when the charging rate drops below a predetermined minimum charging rate SOCmin. The predetermined minimum charging rate SOCmin is configured to be periodically corrected so that the emergency power consumption of the emergency load continues to be maintained at or above the required capacity.

[0010] According to the method as described above, after setting aside a battery capacity sufficient to operate the emergency load, the minimum charging rate is calculated and the charging control of the storage battery is performed. Therefore, it is possible to guarantee the supply of power to the emergency load at the time of a power outage by the storage battery without providing a generator that requires a periodic actual load test. In addition, if the emergency power supply is a storage battery, power can be instantaneously supplied from the storage battery at the time of a power outage, so there is no need to use a static switch as a power switch. Therefore, the labor required for maintenance and inspection of the switch can be reduced.

[0011] Furthermore, by charging the storage battery at times other than the peak of the power demand by the normal load and supplying power from the storage battery to the normal load at the peak of the power demand, it is possible to achieve leveling of the power received from the power plant or substation. In addition, in a station building power supply system that supplies power to a station building, it is provided with two power receiving lines (a normal line and a standby line) that receive AC power supply from a power plant or substation, and two sets of transformers are provided corresponding to each of the two power receiving lines.

[0012] Also, the system control device Based on the emergency capacity EC corresponding to the emergency power consumed when the emergency load is operated for a preset predetermined time, the rated capacity RC of the storage battery, the capacity maintenance rate SOH of the storage battery, and the ratio NC of the power capacity that needs to be left on the system, the following formula SOCmin = EC / (RC × SOH × (1 - NC)) is used to calculate the minimum charge rate SOCmin, and the minimum charge rate SOCmin used for control is periodically corrected. Thereby, an accurate minimum charge rate considering the aging change of the storage battery can be calculated.

[0013] Furthermore, preferably, the power storage device includes a bidirectional conversion circuit capable of converting alternating current to direct current and direct current to alternating current, and a power storage control circuit that performs switching control of the bidirectional conversion circuit and charge and discharge control of the storage battery. The system control device is composed of the power storage control circuit and a main control device having a function of transmitting commands to the power storage control circuit. The power storage control circuit is configured to calculate the charge start charge rate of the storage battery using the above formula and start charging the storage battery when the charge rate of the storage battery drops below the charge start charge rate. The main control device is configured to calculate the minimum charge rate of the storage battery using the above formula and transmit a command to start charging the storage battery to the power storage control circuit when the charge rate of the storage battery drops below the minimum charge rate. The charge start charge rate of the storage battery calculated by the power storage control circuit is set to be lower by a predetermined margin than the minimum charge rate of the storage battery calculated by the main control device.

[0014] According to the method as described above, since the roles of the two control devices can be shared, the main control device (EMS) can efficiently perform power leveling control. Also, since a margin is provided between the charging start rate calculated by the power storage control circuit (charge and discharge control circuit) and the minimum charging rate calculated by the main control device, it is possible to avoid the power storage control circuit from forcibly charging the battery at a timing unintended by the upper main control device.

[0015] Also, preferably, the power supply system includes a solar power generation device, and when there is power supply from the solar power generation device, the main control device is configured to execute control to reduce the amount of power received from the power receiving line. According to such a method, since a solar power generation device is provided in addition to the battery as an emergency power source, the power obtained by the solar power generation device can be used to drive the loads in the facility, so that the amount of power received from the power plant or substation can be reduced, and cost reduction can be achieved.

[0016] Furthermore, preferably, the power supply system includes power consumption detection means for detecting the total power supplied to the plurality of types of electrical equipment, and power generation power detection means for detecting the power generated by the solar power generation device, and when the amount of power detected by the power generation power detection means exceeds the amount of power detected by the power consumption detection means, the power storage control device is configured to execute charging control of the power storage device. According to such a method, when there is surplus power in the power of the solar power generation device, the battery can be charged, so that the power obtained by the solar power generation device can be used without waste, the environmental load can be reduced, and it can contribute to power leveling.

[0017] Also, preferably, the ratio of the power capacity that needs to be left on the system is made to be the ratio of the capacity corresponding to the cut-off voltage of the battery. By doing so, it is possible to prevent the performance of the battery from rapidly deteriorating due to over-discharge.

Advantages of the Invention

[0018] According to the charge and discharge control method of the storage battery of the present invention, in a power supply system equipped with an emergency power supply function using a storage battery, it is possible to guarantee the supply of power to emergency loads when a power outage occurs. Further, there is an effect that power leveling can be achieved.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0020] Hereinafter, with reference to the drawings, it is a system configuration diagram showing an embodiment of a station building power supply system as a suitable system example to which the present invention is applied. As shown in Fig. 1, the station building power supply system of this embodiment includes a normal line (high voltage No. 1) 11A for receiving high-voltage AC power supplied from the power grid of the power company and a standby line (high voltage No. 2) 11B, and the high-voltage AC power of each line is received through circuit breakers DSa, DSb and disconnectors CBa, CBb and converted into power suitable for the load of the low-voltage first AC power system by first transformers 12A, 12B and converted into power suitable for the load of the low-voltage second AC power system or converted three-phase AC into single-phase AC by second transformers 13A, 13B, a power storage device 14 composed of a storage battery and a control system for performing charge and discharge control thereof, a solar power generation device 15, and an EMS (Energy Management System) 16 for controlling the entire system for energy saving.

[0021] In addition, the station building power supply system is provided with switches SW1A, SW1B for selectively supplying the power converted by transformer 12A or 13A to lighting devices 21, outlets 22, etc., and switches SW3A, SW3B for switching the power supplied to general power 26 such as air conditioners. On the other hand, in addition to emergency loads such as induction lamps 27A and fire-fighting equipment (power for sprinklers) 27B, power is supplied to important loads such as ticket vending machines 23, ticket gates 24, and elevators 25 that require instantaneous power switching like escalators through the power storage device 14. In this embodiment, among these loads, power is supplied from the power storage device 14 to the ticket vending machine 23, ticket gate 24, and induction lamp 27A through a Scott transformer ST. Note that elevators (except escalators) may be treated the same as general power 26.

[0022] In a conventional power supply system (Fig. 4) equipped with an emergency generator, electromagnetic switches were used for switches SW1A, SW1B and SW3A, SW3B, and static switches were used for switches SW2A, SW2B and SW4A, SW4B. However, in the station building power supply system of this embodiment (Fig. 1) equipped with a power storage device 14 instead of an emergency generator, static switches can be made unnecessary. Therefore, when using a static switch, it was necessary to provide a static switch for each electrical facility, resulting in a large number of switches and requiring a lot of labor for maintenance and inspection. However, in the system of this embodiment, the static switch can be eliminated, thus reducing the labor required for maintenance and inspection.

[0023] In addition, in the station building power supply system of this embodiment, the energy storage device 14 can supply power to electrical facilities instead of the emergency generator when a power outage occurs, and is designed to be used not only for emergency power supply but also for power leveling.

[0024] The energy storage device 14 is not particularly limited, but includes a storage battery 41 composed of a secondary battery such as a lithium-ion battery or a lead-acid battery, a DC / DC converter 42 with MPPT (a function that automatically follows the maximum power point of the power generation output) for converting the voltage supplied from the solar power generation device 15, a bidirectional voltage conversion circuit 43 having an AC / DC converter for converting alternating current to direct current and an inverter for converting direct current to alternating current, a charge and discharge control circuit 44 for controlling the bidirectional voltage conversion circuit 43 in response to a command from the EMS 16, and the like.

[0025] In addition, the charge and discharge control circuit 44 of the energy storage device 14 and the EMS 16 are connected by a LAN cable or the like so as to be capable of data transfer, and the energy storage device 14 is provided with a communication interface (I / F) 45 to which a LAN cable is connected. Regarding the bidirectional voltage conversion circuit 43 and the power control device including the charge and discharge control circuit 44 of the storage battery, they are described in the above-mentioned Patent Document 1 and the like. In the present invention, a device having the same configuration as the power control device of Patent Document 1 can be used as the energy storage device 14, so a detailed description of the energy storage device 14 is omitted.

[0026] Furthermore, in the station building power supply system of this embodiment, a wattmeter or ammeter for measuring the power or current consumed in the station building itself and a wattmeter or ammeter for measuring the generated power or current output by the solar power generation device 15 are provided as sensors, and the power values or current values measured by these sensors are configured to be input to the EMS 16.

[0027] Then, the EMS 16 monitors the power consumption by all the loads in the station building and the power generation by the solar power generation device 15, and when the power generation exceeds the power consumption of the load, it transmits a command to execute charging of the storage battery 41 to the charge and discharge control circuit 44 of the energy storage device 14, or transmits a command to execute discharge of the storage battery 41 during the morning and evening commuting hours when the number of running trains is large. That is, the EMS 16 functions as a control device superior to the charge and discharge control circuit 44 of the energy storage device 14.

[0028] In the station building power supply system of this embodiment, by the EMS 16 performing the above control, solar energy can be effectively utilized to reduce the environmental load, and at the same time, the peak power amount received from the power company can be reduced to levelize the power, thereby reducing the fee paid to the power company and realizing cost reduction.

[0029] Next, the charging and discharging control characteristics of the charge and discharge control circuit 44 of the energy storage device 14 constituting the station building power supply system of this embodiment and the system control method will be described. The characteristics of the charging and discharging control in this embodiment are that in order to ensure that power can be supplied from the storage battery to the emergency load when a power outage (including momentary power outages) occurs, a certain amount of emergency capacity is set aside, and charging and discharging for power leveling is performed with the surplus (Characteristic 1); and since the storage battery's initial capacity retention rate (SOH) decreases due to aging, when the EMS (Energy Management System) manages the emergency capacity at the minimum charge rate (minimum SOC), it is managed with the SOC taking into account the SOH (Characteristic 2).

[0030] First, the replacement of the emergency capacity of the above-mentioned feature 1 will be described with reference to FIG. 2. In FIG. 2, (A) shows the battery capacity when the storage battery is new, and (B) shows the battery capacity when the storage battery has aged. RC is the rated capacity, SOC is the charge rate, and SOCmin1 and SOCmin2 are the respective minimum charge rates. Note that the fully charged capacity FC of the aged storage battery in (B) is expressed as the rated capacity RC × the capacity retention rate SOH.

[0031] In this embodiment, for each station building, from the total consumption current of the emergency loads that need to be operated during a power outage, the power consumed when the emergency loads are operated for a predetermined time (for example hours) (emergency power) is calculated in advance. Then, assuming that the power is supplied only from the storage battery provided in the station building, the emergency power is secured as the emergency capacity EC from the battery capacities in FIGS. 2(A) and 2(B). Also, a proportion (for example, 7%) of the power capacity that needs to be left on the system, such as the capacity corresponding to the cut-off voltage to prevent rapid deterioration of the storage battery due to over-discharge, is secured as the non-use capacity NC. Then, the capacity obtained by subtracting the above-mentioned emergency capacity EC and non-use capacity NC from the rated capacity RC or the fully charged capacity FC (rated capacity RC × SOH) is used as the charge and discharge capacity managed by the EMS16.

[0032] That is, the EMS16 always calculates the current charge rate of the storage battery based on the charge and discharge amount of the storage battery or the battery state such as the battery voltage, and uses the following formula SOCmin = EC / (RC × SOH × (1 - NC)) to periodically calculate the minimum charge rate SOCmin, for example, once a month. If the current charge rate SOC drops to the minimum charge rate SOCmin, a charge start command is sent to the charge and discharge control circuit 44 of the power storage device 14, and the charge and discharge control circuit 44 controls the bidirectional voltage conversion circuit 43 to charge the storage battery. Incidentally, when the above formula for calculating the charge rate is described in words, Minimum charge rate = Emergency capacity ÷ (Rated capacity × Capacity retention rate × (1 - Non-use capacity ratio)).

[0033] Note that the state of charge (SOC) at the calculation time (hereinafter referred to as the current time) can be calculated from the voltage of the storage battery to obtain the remaining battery amount, and can be calculated by the formula: charge rate = remaining amount / full charge capacity. Also, the state of health (SOH) of the current time can be obtained from the charge and discharge control circuit 44 of the power storage device 14, and the full charge capacity can be obtained from the state of health (SOH) of the current time and the rated capacity as described above.

[0034] As described above, in this embodiment, since the EMS 16 automatically calculates and corrects the minimum state of charge SOCmin by the above calculation formula, there is an advantage that it is not necessary to manually input and correct the minimum state of charge as in the prior art. Also, conventionally, in order to eliminate the trouble of the above manual input, a value of the minimum state of charge considering a certain number of years has been set from the beginning, and thereby it is possible to avoid the remaining amount of the storage battery from encroaching on the emergency capacity, but the surplus of the storage battery cannot be fully utilized effectively. On the other hand, according to this embodiment, there is an advantage that the surplus of the storage battery can be utilized to the maximum extent possible.

[0035] By the way, in the above embodiment, it has been described that the EMS 16 calculates the minimum state of charge SOCmin of the storage battery and the state of charge SOC at the current time by the above calculation formula, and if the state of charge SOC at the current time drops below the minimum state of charge SOCmin, a charge start command is transmitted to the charge and discharge control circuit 44 of the power storage device 14, and the charge and discharge control circuit 44 charges the storage battery. However, in parallel with such control, the charge and discharge control circuit 44 of the power storage device 14 calculates the minimum state of charge SOCmin of the storage battery and the state of charge SOC at the current time by the above calculation formula, and if the state of charge SOC at the current time drops below the minimum state of charge SOCmin, it is also possible to configure the system to execute control to forcibly charge the storage battery.

[0036] However, in the case as described above, there is a possibility that the charge and discharge control circuit 44 forcibly charges the storage battery at a timing not intended by the upper control device, the EMS 16. Therefore, as shown in FIG. 3, the charge start state of charge (SOCcs) of the storage battery determined by the charge and discharge control circuit 44 according to the above calculation formula is set to be lower than the minimum state of charge (SOCmin) of the storage battery calculated by the EMS 16 according to the above calculation formula by a predetermined margin M (for example, 1%).

[0037] Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments. For example, in the above embodiments, the power storage device 14 is configured to include the charge and discharge control circuit 44 of the storage battery 41, but the EMS 16 may also have the function of the charge and discharge control circuit 44.

[0038] Furthermore, in the above embodiments, the case where the present invention is applied to a station power supply system including the photovoltaic power generation device 15 together with the power storage device 14 has been described, but the present invention can also be applied to a station power supply system without a photovoltaic power generation device. In addition, in the above embodiments, the case where the present invention is applied to a station power supply system has been described, but the present invention is not limited to stations, and can be applied to power supply systems in facilities equipped with emergency power generation devices such as hospitals, evacuation shelters during disasters, and parking lots.

Description of Reference Numerals

[0039] 11A Normal line 11B Standby line 12A, 12B First transformer 13A, 13B Second transformer 14 Power storage device 15 Photovoltaic power generation device 16 EMS (Energy Management System) 17 Generator 21 Lighting device 22 Outlet 23 Ticket vending machine 24 Ticket gate 25 Elevator (escalator, elevator) 26 General power (air conditioner, etc.) 27A Induction lamp (emergency load) 27B Fire extinguishing equipment (emergency load) SW switch 41 Battery 42 MPPT converter 43 Bidirectional voltage conversion circuit 44 Charge and discharge control circuit 45 Communication interface

Claims

1. One or more transformers that receive AC power supply from a power plant or a substation and convert it respectively according to electrical equipment that becomes a load, A plurality of switches provided between a plurality of types of electrical equipment provided in the facility to be supplied with power and the transformer, A power storage device including a storage battery that can be charged and discharged by the AC power, Battery state detection means for detecting the state of the storage battery, A system control device for controlling the charging and discharging operations of the plurality of switches and the power storage device, and in a power supply system in which the plurality of types of electrical equipment includes an emergency load that operates during interruption of the AC power supply, a method for controlling charging and discharging of a storage battery, The power storage device and the system control device, It is provided with a charging rate calculation means for calculating the current charging rate of the storage battery based on the battery state detected by the battery state detection means, The power storage device includes a bidirectional conversion circuit that can convert AC to DC and DC to AC, and a power storage control circuit that controls switching of the bidirectional conversion circuit and charging and discharging of the storage battery, The system control device is composed of the power storage control circuit and a main control device having a function of transmitting commands to the power storage control circuit, The power storage control circuit is configured to calculate a charging start charging rate of the storage battery using a predetermined formula and start charging of the storage battery when the charging rate of the storage battery drops below the charging start charging rate, The main control device is configured to calculate a minimum charging rate SOCmin of the storage battery using a predetermined formula and transmit a command to start charging of the storage battery to the power storage control circuit when the charging rate of the storage battery drops below the minimum charging rate SOCmin, The charging start charging rate of the storage battery calculated by the power storage control circuit is set to be lower by a predetermined margin than the minimum charging rate SOCmin of the storage battery calculated by the main control device. A method for controlling charging and discharging of a storage battery in a power supply system.

2. The main control device, Using the emergency capacity EC corresponding to the emergency power consumed when the emergency load is operated for a preset predetermined time, the rated capacity of the storage battery as RC, the capacity retention rate SOH of the storage battery, and the ratio NC of the power capacity that needs to be left on the system, the following formula SOCmin = EC / (RC × SOH × (1 - NC)) Calculate the minimum state of charge SOCmin using the above, and periodically correct the minimum state of charge SOCmin so that the emergency power consumption of the emergency load continues to be maintained at or above the required capacity. A method for controlling charging and discharging of a storage battery in the power supply system according to claim 1, characterized in that.

3. The power supply system includes a solar power generation device, The main control device executes control to reduce the amount of power received from the power receiving line when power is supplied from the solar power generation device. A method for controlling charging and discharging of a storage battery in the power supply system according to claim 2, characterized in that.

4. The power supply system is Power consumption detection means for detecting the total power supplied to the plurality of types of electrical equipment, Power generation power detection means for detecting the power generated by the solar power generation device, and is provided with, When the amount of power detected by the power generation power detection means exceeds the amount of power detected by the power consumption detection means, the charge control circuit executes charge control of the power storage device. A method for controlling charging and discharging of a storage battery in the power supply system according to claim 3, characterized in that.

5. The ratio of the power capacity that needs to be left on the system is the ratio of the capacity corresponding to the cut-off voltage of the storage battery. A method for controlling charging and discharging of a storage battery in the power supply system according to any one of claims 2 to 4, characterized in that.

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