Monitoring device

Abstract

To provide a monitoring device capable of easily monitoring a deterioration state of a battery included in a stationary power storage system.SOLUTION: The monitoring device comprises: a calculation part configured to calculate an estimated value of full charge capacity of a battery included in the stationary power storage system; a request part configured to require, when tolerance between the full charge capacity and the estimated value is a specified value or more, permission to calculate the estimated value from a user of the stationary power storage system; and a control part configured to control, when calculation of the estimated value is permitted according to the request from the request part, battery operation according to an operation pattern of charging and discharging with an electric conduction stop period for cancelling polarization of the battery interposed therebetween. The calculation part calculates the estimated value from at least one of charge capacity and discharge capacity of the battery according to the operation pattern.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a monitoring device. [Background technology]

[0002] For example, the deterioration state of a battery mounted on a hybrid vehicle can be monitored by checking the full charge capacity during external charging (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-7564 Summary of the Invention [Problem to be solved by the invention]

[0004] However, because batteries in stationary energy storage systems are constantly receiving and transmitting power from the power grid and power generation facilities, there are insufficient opportunities to check their full charge capacity. Even if there is an opportunity, the check may be interrupted due to a sudden increase in power demand. This makes it difficult to monitor the deterioration state of batteries in stationary energy storage systems.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to provide a monitoring device that can easily monitor the deterioration state of batteries provided in a stationary energy storage system. [Means for solving the problem]

[0006] The monitoring device of the present invention includes a calculation unit that calculates an estimate of the full charge capacity of a battery provided in a stationary energy storage system; a request unit that requests permission to calculate the estimate from a user of the stationary energy storage system when an error between the full charge capacity and the estimate is equal to or greater than a predetermined value; and a control unit that, when calculation of the estimate is permitted in response to the request from the request unit, controls operation of the battery in accordance with an operation pattern of charging and discharging with a power-off period sandwiched between to eliminate polarization of the battery, and the calculation unit calculates the estimate from at least one of the charge capacity and discharge capacity of the battery in accordance with the operation pattern. [Effects of the Invention]

[0007] According to the present invention, the deterioration state of a battery provided in a stationary electricity storage system can be easily monitored. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a configuration diagram showing an example of a stationary electricity storage system and a monitoring device. [Figure 2] FIG. 2 is a time chart showing an example of processing during capacity confirmation operation. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Configuration of stationary energy storage system and monitoring device) 1 is a configuration diagram showing an example of a stationary energy storage system 9 and a monitoring device 1. The stationary energy storage system 9 includes a plurality of energy storage units 90, a PCU (Power Control Unit) 91, a PCS (Power Conditioning System) 92, and a power management system 93. The plurality of energy storage units 90 are connected in parallel to the PCS 92 with an output capacitor 5 interposed therebetween. The PCS 92 is, for example, an inverter, and converts AC current on the power grid 70, power generation equipment 71, and load 72 side into DC current on the stationary energy storage system 9 side, and vice versa.

[0010] To promote efficient power utilization, the stationary power storage system 9 stores power generated by power generation equipment 71, such as wind power generation or solar power generation, in a power storage unit 90 and supplies the power in a timely manner to loads 72, such as hybrid vehicles, electric vehicles, household appliances, and factory production equipment, and to the power grid 70. The power management system 93 includes multiple servers and the like, and manages the loads 72 and PCS 92 according to the power status of the power grid 70 and power generation equipment 71.

[0011] The power storage unit 90 includes a battery (storage battery) 2 such as a lithium ion battery, a DC (Direct Current)-DC converter 3, a sensor 20, a pair of relays 40, 41, and an input capacitor 42. The sensor 20 includes a current sensor and a voltage sensor. The sensor 20 detects the current and voltage of the battery 2 and outputs the detected values ​​to the monitoring device 1.

[0012] The battery 2 is connected in parallel to the input capacitor 42 via the connected relays 40 and 41. Both ends of the input capacitor 42 are connected between the relays 40 and 41 and the DC-DC converter 3, respectively.

[0013] The DC-DC converter 3 is connected in parallel to a pair of input / output terminals T on the PCS 92 side, and boosts the voltage of the battery 2. The DC-DC converter 3 includes switches SWa, SWb and a reactor 43. The switches SWa, SWb are connected in series to each other and include an IGBT (Insulated Gate Bipolar Transistor) and a freewheeling diode connected between the collector and emitter of the IGBT. One end of the reactor 43 is connected to the relay 40 and the input capacitor 42, and the other end of the reactor 43 is connected between the switches SWa, SWb. The switches SWa, SWb are turned on and off by a PWM (Pulse Width Modulation) signal input from the PCU 91 to the gate of the IGBT.

[0014] The monitoring device 1 monitors the deterioration state by estimating the full charge capacity of the battery 2. The monitoring device 1 is, for example, a computer equipped with one or more ECUs (Electronic Control Units) each having a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), not shown. The monitoring device 1 communicates with the sensor 20, the PCU 91, and the power management system 93 via a network, a bus, or the like, not shown.

[0015] The monitoring device 1 has, for example, a calculation unit 10, a request unit 11, and a control unit 12 as software functions that drive a CPU. The calculation unit 10, the request unit 11, and the control unit 12 may be realized by hardware such as an IC (Integrated Circuit). The monitoring device 1 also has a SOC (State Of Charge) table 13 stored in a storage means such as a memory.

[0016] When the user of the stationary energy storage system 9 has permitted the capacity confirmation operation of the battery 2, the calculation unit 10 calculates an estimate of the full charge capacity of the battery 2. In the capacity confirmation operation, the battery 2 is charged and discharged in accordance with a predetermined operation pattern for calculating the estimate of the full charge capacity. At this time, the power management system 93 restricts normal power supply and reception to the power grid 70, the power generation equipment 71, and the load 72, and controls the PCS 92 in accordance with the operation pattern of the battery 2.

[0017] When the error between the full charge capacity and the estimated value is equal to or greater than a predetermined value, the request unit 11 requests permission to calculate the estimated value from the user of the stationary energy storage system 9. For example, the request unit 11 requests the power management system 93 to perform a capacity confirmation operation when a predetermined period has elapsed since the calculation unit 10 last calculated the estimated value. This period is determined based on, for example, the change characteristic of the capacity of the battery 2 with respect to the usage time.

[0018] The user operates the power management system 93 to permit the capacity confirmation operation. When the user permits the capacity confirmation operation, the power management system 93 transmits a permission flag and operation pattern data to the request unit 11. The operation pattern is set, for example, as a change in the command value of the amount of power to be charged and discharged with respect to time. As will be described later, the operation pattern is set so that charging and discharging are performed alternately, with a power-off period sandwiched between them to eliminate polarization of the battery 2. The request unit 11 outputs the permission flag and operation pattern data to the calculation unit 10 and the control unit 12.

[0019] When calculation of the estimated value is permitted in response to a request from the request unit 11, the control unit 12 controls the operation of the battery 2 in accordance with an operation pattern of charging and discharging with a power-off period sandwiched therebetween to eliminate polarization of the battery 2. The control unit 12 controls the duty ratio of the PWM signal for the PCU 91 in accordance with the operation pattern.

[0020] For example, during capacity confirmation operation, the calculation unit 10 acquires the current and voltage of the battery 2 from the sensor 20. The calculation unit 10 calculates the integrated current values ​​(Ah) during the charging period and the discharging period of the battery 2. The integrated current value during the charging period is the charging capacity, and the integrated current value during the discharging period is the discharging capacity. The voltage is acquired after the polarization of the battery 2 is eliminated during the power-off period.

[0021] The calculation unit 10 obtains the SOC of the battery 2 from the SOC table 13 based on the voltage of the battery 2 when power is not being supplied, i.e., the open circuit voltage (OCV). The SOC table 13 is map data that shows the change characteristics of the SOC with respect to the OCV of the battery 2. The calculation unit 10 calculates the difference (%) in SOC between the start and end of charging, and the difference in SOC between the start and end of discharging. The difference in SOC is referred to as the interval SOC.

[0022] Estimated value = Integrated current value / SOC section × 100 (1)

[0023] The calculation unit 10 calculates an estimated value of the full charge capacity for each of charging and discharging from the above formula (1). The estimated value of the full charge capacity is used as an index of the deterioration state of the battery 2.

[0024] (Processing during capacity confirmation operation) FIG. 2 is a time chart showing an example of the processing during the capacity confirmation operation. FIG. 2 shows a permission flag and a command for discharge power input from the power management system 93 to the monitoring device 1, the SOC of the battery 2, the states (on or off) of the switches SWa and SWb, and the time change of the calculation process. Note that the command for discharge power is an operation pattern of the battery 2, and when it is a positive value, it indicates a command value for the amount of power to be discharged, and when it is a negative value, it indicates a command value for the amount of power to be charged.

[0025] The permission flag changes from "0" (not permitted) to "1" (permitted) at time To in response to the request from the request unit 11. Thereby, the capacity confirmation operation is started.

[0026] In the operation pattern of the battery 2, the periods from time Ta to Tb and from Tg to Th are charging periods, the period from time Td to Te is a discharging period, and the periods from time Tb to Td, from Te to Tg, and from Th to Tj are power-off periods. Thus, the operation pattern is set such that the charging period and the discharging period alternately come with a power-off period in between. The power-off period is longer than the time required to eliminate the polarization of the battery 2. The power-off period enables accurate estimation of the full charge capacity.

[0027] During the power-off period, the switches SWa and SWb are alternately turned off. The switch SWa is turned off at times Tb to Tc, Te to Tf, and Th to Ti, and the switch SWb is turned off at times Tc to Td, Tf to Tg, and Ti to Tj. The off time of each of the switches SWa and SWb is, for example, half of the power-off period. When one of the switches SWa and SWb is turned off, no current flows between the battery 2 and the PCS 92, so charging and discharging are not performed. Note that during the time from Ta to Tj, the relationship Ta < Tb < Tc < Td < Te < Tf < Tg < Th < Ti < Tj holds.

[0028] When the capacity check operation is started, first, charging is performed until the SOC of the battery 2 reaches substantially 100(%) from the initial value X(%). During the subsequent power-off period (Tb to Td), the calculation unit 10 acquires the open-circuit voltage OCV_H from the sensor 20 after the time required to eliminate polarization of the battery 2 has elapsed. Note that the open-circuit voltage OCV_H may be acquired once each during the off period of the switches SWa and SWb, in preparation for a failure in acquisition, as will be described later.

[0029] Next, during the discharge period (Td to Te) of the battery 2, the calculation unit 10 calculates an integrated current value by integrating the current of the battery 2. This provides the discharge capacity. The SOC also substantially decreases from 100% to 0%. During the subsequent power-off period (Te to Tg), the calculation unit 10 acquires the open-circuit voltage OCV_L from the sensor 20 after the time required to eliminate polarization of the battery 2 has elapsed. Note that the open-circuit voltage OCV_L may be acquired once each during the off period of the switches SWa and SWb, in preparation for a failure in acquisition, as will be described later.

[0030] Next, during the charging period (Tg to Th) of the battery 2, the calculation unit 10 calculates an integrated current value by integrating the current of the battery 2. This provides the charge capacity. The SOC also increases substantially from 0% to 100%. During the subsequent power-off period (Th to Tj), the calculation unit 10 acquires the open-circuit voltage OCV_H from the sensor 20 after the time required to eliminate polarization of the battery 2 has elapsed. Note that the open-circuit voltage OCV_H may be acquired once each during the off period of the switches SWa and SWb, in preparation for a failure in acquisition, as will be described later.

[0031] The calculation unit 10 calculates the section SOC from the open circuit voltages OCV_H and OCV_L acquired during the period from time Tb to Tg, and calculates an estimated value #1 using the above formula (1) from the integrated current value during the discharging period (Td to Te) and the section SOC. The calculation unit 10 also calculates the section SOC from the open circuit voltages OCV_H and OCV_L acquired during the period from time Te to Tj, and calculates an estimated value #2 using formula (1) from the integrated current value during the charging period (Tg to Th). In this case, the monitoring device 1 may use either estimated value #1 or #2 as an index of the degradation state of the battery 2.

[0032] However, the power management system 93 may interrupt the capacity confirmation operation due to, for example, a sudden increase in power demand in the load 72. In this case, the operation pattern is interrupted, which may result in failure to obtain the charge capacity or discharge capacity.

[0033] In response to this, the calculation unit 10 calculates an estimated value from at least one of the charge capacity and discharge capacity of the battery 2 according to the operation pattern. This allows the calculation unit 10 to calculate an estimated value more reliably than when only one of the charge capacity and discharge capacity is acquired.

[0034] For example, the calculation unit 10 determines that the charge capacity or discharge capacity that is below a predetermined threshold has failed to be acquired and does not use it in calculating the estimated value, but calculates the estimated value using the one that is equal to or greater than the threshold. Therefore, even if the operation pattern is interrupted, the calculation unit 10 can calculate the estimated value as long as it successfully acquires at least one of the charge capacity and the discharge capacity. Note that when the operation pattern is interrupted, there is a risk that it may fail to acquire the open-circuit voltage OCV_H or OCV_L after polarization elimination. In this case, the calculation unit 10 calculates the estimated value from the combination of the open-circuit voltages OCV_H and OCV_L that were successfully acquired.

[0035] As described above, when the error between the full charge capacity and the estimated value is equal to or greater than a predetermined value, the request unit 11 requests permission to calculate the estimated value from the user of the stationary energy storage system 9. This allows the monitoring device 1 to prompt the user to check the full charge capacity in a timely manner.

[0036] When calculation of the estimated value is permitted in response to a request from the request unit 11, the control unit 12 controls the operation of the battery 2 in accordance with an operation pattern of charging and discharging with a power-off period sandwiched therebetween to eliminate polarization of the battery 2. The calculation unit 10 calculates the estimated value from at least one of the charge capacity and discharge capacity of the battery 2 in accordance with the operation pattern. This allows the monitoring device 1 to reliably and highly accurately calculate the estimated value. Therefore, the monitoring device 1 can easily monitor the deterioration state of the battery 2 provided in the stationary energy storage system 9.

[0037] The above-described embodiment is a preferred example of the present invention, but the present invention is not limited to this and can be modified in various ways without departing from the spirit of the present invention. [Explanation of symbols]

[0038] 1 monitoring device, 2 battery, 3 DC-DC converter, 9 stationary energy storage system, 10 calculation unit, 11 request unit, 12 control unit, 90 energy storage unit

Claims

[Claim 1] a calculation unit that calculates an estimated value of a full charge capacity of a battery provided in the stationary energy storage system; a request unit that requests permission to calculate the estimated value from a user of the stationary energy storage system when an error between the full charge capacity and the estimated value is equal to or greater than a predetermined value; a control unit that controls the operation of the battery in accordance with an operation pattern of charging and discharging with a power-off period for eliminating polarization of the battery when calculation of the estimated value is permitted in response to a request from the request unit, the calculation unit calculates the estimated value from at least one of a charge capacity and a discharge capacity of the battery according to the operation pattern. monitoring equipment.

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