Power management system

Abstract

To perform proper management of energy.SOLUTION: A power management system manages at least one power generation system that is connected to a power system, and at least one power storage device that is connected to the power system. On the basis of a predicted power generation amount which is a power generation amount of the power generation system and a predicted power demand which is a power demand in the power system predicted for each time section, the power storage device is charged / discharged in a time section during which the reliability of prediction of the time section-based power generation amount and power demand is high. Accordingly, proper management of energy can be performed.SELECTED DRAWING: Figure 3

Description

Technical Field

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[0001] The present invention relates to a power management system.

Background Art

[0002] Conventionally, as this type of power management system, there has been proposed one that manages a power generation system (power supply unit) connected to a power grid and a plurality of power storage devices (storage batteries) connected to the power grid (see, for example, Patent Document 1). In this system, the future power supply and demand balance is predicted, and based on the prediction result, the charge ratio of the power storage device is maintained at the reference SOC in advance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above-described power management system, it is difficult to accurately predict the power demand and the generated power in the power generation system. If the prediction is off, even though the generated power in the power generation system is actually surplus compared to the power demand, proper energy management may not be possible, such as charging the power storage device with power from the power grid or discharging from the power storage device to the power grid.

[0005] The main object of the power management system of the present invention is to perform more proper energy management.

Means for Solving the Problems

[0006] The power management system of the present invention has taken the following means to achieve the above main object.

[0007] The power management system of the present invention is A power management system for managing at least one power generation system connected to a power grid and at least one energy storage device connected to the power grid, Based on the predicted power generation amount, which is the amount of power generated by the power generation system for each time period, and the predicted power demand, which is the power demand in the power grid, the energy storage device is charged and discharged during time periods when the reliability of the predictions for the power generation amount and power demand for each time period is high. This is the gist of it.

[0008] In this power management system of the present invention, based on the predicted power generation amount (the amount of power generated by the power generation system for each time period) and the predicted power demand (the power demand in the power grid), the energy storage device is charged and discharged during time periods when the predictions for power generation amount and power demand for each time period are highly reliable. This suppresses the wasted charging and discharging of power between the power grid and the energy storage device. As a result, more appropriate energy management can be achieved.

[0009] In the power management system of the present invention, the charge and discharge instruction amounts for each time period are set so that the cumulative value obtained by dividing the charge and discharge instruction amounts for the energy storage device for each time period by the reliability is minimized, and the energy storage device is charged and discharged according to the charge and discharge instruction amounts set for each time period. In this way, the charge and discharge amount of the energy storage device for each time period can be set appropriately, and more appropriate energy management can be performed.

[0010] Furthermore, in the power management system of the present invention, the reliability may be set lower for predetermined time periods that are designated as time periods in which at least one of the power generation forecast and the power demand forecast is likely to be inaccurate, compared to time periods other than those designated in advance. This allows for a more appropriate setting of the reliability for each time period. As a result, the time periods for charging and discharging the energy storage device can be appropriately set, enabling more appropriate energy management.

[0011] In this case, the power generation system generates electricity using renewable energy, and the predetermined time period may be at least one of the following: sunrise time, sunset time, and cloudy time. In power generation systems using renewable energy, it is generally difficult to predict the amount of electricity generated during sunrise, sunset, and cloudy time. Therefore, by setting the predetermined time period to at least one of the following: sunrise time, sunset time, and cloudy time, the reliability of each time period can be set more appropriately. This allows for the appropriate setting of the time periods for charging and discharging the energy storage device, enabling more appropriate energy management. Examples of "renewable energy" include solar power, solar thermal energy, wind power, biomass, hydropower, geothermal energy, snow and ice thermal energy, temperature difference, and ground source heat.

[0012] Furthermore, the energy storage device may be mounted on a vehicle, and the predetermined time period may be the time period when the vehicle starts moving. The time period when the vehicle starts moving is difficult to predict because it varies depending on the vehicle user's circumstances, etc. Therefore, by setting the predetermined time period to the time when the vehicle starts moving, the reliability for each time period can be set more appropriately. This allows for the appropriate setting of the time periods for charging and discharging the energy storage device, and enables more appropriate energy management. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram showing the general configuration of the supply and demand management system 10. [Figure 2] This is a schematic diagram showing the general configuration of the electric vehicle 20. [Figure 3] This flowchart shows an example of a configuration routine executed by the CPU of the power management device 70. [Figure 4] This is a timing chart showing an example of the amount of power generated by the distributed power system 12, the power demand of the power grid 62, the reliability R, and the charge / discharge instructions for each time period. [Modes for carrying out the invention]

[0014] Next, embodiments for carrying out the present invention will be described using examples. [Examples]

[0015] Figure 1 is a schematic diagram showing the configuration of the supply and demand management system 10. The supply and demand management system 10 controls distributed power systems 12 owned by consumers such as residences and businesses to adjust the balance of electricity supply and demand. As shown in the figure, it comprises a supply and demand management server 60 and a power management device 70 incorporating the power management system of this embodiment.

[0016] The distributed power generation system 12 is connected to the power grid 62 provided by the power company, and examples of such systems include a thermal power generation system 14 installed in a factory or other facility as a power generation system, a power generation system 16 that uses renewable energy such as solar power, solar thermal energy, wind power, biomass, hydropower, geothermal energy, snow and ice thermal energy, temperature difference, and ground source heat, and multiple electric vehicles 20 equipped with batteries 36 as energy storage devices. Hereinafter, multiple electric vehicles 20 may be collectively referred to as a group of vehicles 120.

[0017] Figure 2 is a schematic diagram showing the configuration of an electric vehicle 20. Each electric vehicle 20 comprises, as shown in the figure, a motor 32, an inverter 34, a battery 36 as an energy storage device, a charge / discharge device 40, and an electronic control unit 50.

[0018] The motor 32 is connected to a drive shaft 26, the rotor of which is linked to drive wheels 22a and 22b via a differential gear 24. The inverter 34 is used to drive the motor 32 and is also connected to the battery 36 via a power line 38. The motor 32 is rotationally driven by the switching control of multiple switching elements (not shown) of the inverter 34 by an electronic control unit 50. The battery 36 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery.

[0019] The charge / discharge device 40 is connected to the power line 38, and is configured to be able to charge the battery 36 with the power from the power system 62 and discharge the battery 36 to the power system 62 when the system-side connector connected to the power system (external power source) 62 and the vehicle-side connector 41 are connected. This charge / discharge device 40 is controlled by an electronic control unit 50.

[0020] The electronic control unit 50 is configured as a microprocessor centered on a CPU (not shown). In addition to the CPU, it includes a ROM that stores a processing program, a RAM that temporarily stores data, an input / output port, and a communication port. Signals from various sensors are input to the electronic control unit 50 via the input port. Examples of the signals input to the electronic control unit 50 include the rotational position θm of the rotor of the motor 32 from a rotational position sensor (not shown) that detects the rotational position of the rotor of the motor 32, the phase currents Iu, Iv, Iw of each phase of the motor 32 from a current sensor (not shown) that detects the phase currents of each phase of the motor 32, the voltage Vb of the battery 36 from a voltage sensor 像36a attached between the terminals of the battery 36, the input / output current Ib of the battery 36 from a current sensor 36b attached to the output terminal of the battery 36, and the temperature Tb of the battery 36 from a temperature sensor 36c attached to the battery 36. Also included are the ignition signal from the ignition switch 52, the accelerator opening Acc from an accelerator pedal position sensor 84 that detects the depression amount of the accelerator pedal 83, and the vehicle speed V from a vehicle speed sensor 54. Various control signals are output from the electronic control unit 50 via the output port. Examples of the signals output from the electronic control unit 50 include a control signal to the inverter 34 and a control signal to the charge / discharge device 40. The electronic control unit 50 calculates the stored electricity amount Sb and the state of charge SOC of the battery 36 based on the integrated value of the input / output current Ib of the battery 36 from the current sensor 36b. Here, the state of charge SOC is the ratio of the capacity stored in the battery 36 to the total capacity of the battery 36. The electronic control unit 50 is configured to be able to communicate wirelessly with the power management device 70.

[0021] In the electric vehicle 20 configured in this way, the electronic control unit 50 sets the required torque Td* as the torque command Tm*, and performs switching control of a plurality of switching elements of the inverter 34 so that the motor 32 is driven by the torque command Tm*.

[0022] In addition, in the electric vehicle 20, when the vehicle-side connector 41 and the grid-side connector are connected during parking, the electronic control unit 50 controls the charging / discharging device 40 so that the battery 36 is charged and discharged between the power grid 62, and charges and discharges the battery 36.

[0023] The supply-demand management server 60 is installed in the power company. When it is expected that there will be a shortage of the power supply amount of the power grid 62 based on the power generation status of the power company, future power generation plans, current weather, future weather forecasts, current power consumption, future power consumption forecasts, etc., the supply-demand management server 6 sends a request for reducing the demand for electricity (down DR) to the power management device 70. When it is expected that there will be an excess of the power supply amount, a request for increasing the demand for electricity (up DR) is sent to the power management device 70.

[0024] The power management device 70 manages the distributed power system 12. Although not shown in the figure, the power management device 70 is configured as a computer including a CPU, ROM, RAM, etc. It communicates wirelessly with a plurality of electric vehicles 20 related to the contract via the network 72, or communicates with the thermal power generation system 14 or the power generation system 16 via the network 72, either wired or wirelessly. The power management device 70 sets a charging / discharging instruction including a charging / discharging instruction amount Wc* as the charging / discharging amount required for the vehicle group 120 for each time period. Then, based on the set charging / discharging instruction, a charging / discharging planned value for each electric vehicle 20 is created and transmitted to the electronic control unit 50 of the electric vehicle 20. The electronic control unit 50 of the electric vehicle charges and discharges the battery 36 based on the received charging / discharging planned value.

[0025] Next, the operation of the supply and demand management system 10 of the embodiment configured in this way, in particular, the operation when setting charge and discharge instructions for the vehicle group 120, will be described. Figure 3 is a flowchart of an example of a setting routine executed by the CPU of the power management device 70. Figure 4 is a timing chart showing an example of the amount of power generated in the distributed power system 12 for each time period, the power demand of the power grid 62, the reliability R, charge and discharge instructions, and the energy storage ratio SOCt in the vehicle group 120 (the sum of the energy storage ratio SOCs of the batteries 36 of the multiple electric vehicles 20). In Figure 4, for comparison, the time change of the charge and discharge instructions and the energy storage ratio SOCt in the vehicle group 120 of a comparative example, which are determined without considering the reliability R, are shown as a comparative example. This routine is executed at predetermined intervals (for example, every 12 hours, 24 hours, 36 hours, etc.).

[0026] When this routine is executed, the CPU of the power management device 70 performs the process of obtaining the predicted power generation Wgest, predicted power demand Wpd, and confidence level R for each time period from the present until a predetermined time (for example, every 30 minutes, 1 hour, 1.5 hours) (step S100).

[0027] The predicted power generation amount Wgest is a predicted value of the power generation amount of the distributed power system 12. The predicted power generation amount Wgest is set by pre-defining and storing in ROM a first prediction relationship, which is the relationship between the date, weather, temperature, and the power generation amount of the distributed power system 12 for each time period, and deriving the corresponding power generation amount from the stored first prediction relationship given the current date, weather, and temperature. The first prediction relationship is determined from data acquired in the past, which consists of weather, temperature, and power generation amount of the distributed power system 12 for each time period, for each date and time period.

[0028] The predicted power demand Wpd is the predicted value of power demand in the power grid 62. The predicted power generation Wgest is set by pre-defining and storing a second prediction relationship, which is the relationship between the date, weather, temperature, and power demand of the power grid for each time period, in ROM, and then deriving the corresponding power demand from the stored second prediction relationship given the current date, weather, and temperature. The second prediction relationship is determined from data on the weather, temperature, and power demand of the power grid 62 for each time period that has been acquired in the past.

[0029] The confidence level R is the confidence level of the forecasts for predicted power generation Wgest and predicted electricity demand Wpd. As shown in Figure 4, the confidence level R is set lower for low-confidence periods (predetermined periods) that are predetermined as periods when at least one of the power generation forecasts or electricity demand forecasts is likely to be wrong, compared to periods other than the low-confidence periods. Examples of low-confidence periods include the sunrise period, which is a range of several hours including sunrise; the sunrise period, which is a range of several hours including sunset; cloudy periods; and the period when electric vehicles 20 start up.

[0030] Next, the routine is terminated by setting charge and discharge instructions, including the charge and discharge instruction amount Wc* for each time period, using a mathematical optimization method so that the charge and discharge amounts are greater during time periods with high confidence R (step S110). In this mathematical optimization method, the constraints are that the energy storage ratio SOCt of the vehicle group 120 does not exceed the upper and lower limits SOCtmax and SOCtmin of the energy storage ratio SOCt of the vehicle group 120, which are the sum of the upper and lower limits SOCmax and SOCmin of the energy storage ratio SOC of the batteries 36 of each electric vehicle 20, and that charging occurs when the predicted charge and discharge amount Wcest, obtained by subtracting the predicted power demand Wpd from the predicted power generation amount Wgest, is positive, discharging occurs when it is negative, and no charging or discharging occurs when the value is 0. Then, the charge and discharge instruction amount Wc* for each time period is set to minimize the value of the charge and discharge instruction amount Wc* divided by the confidence R for each time period, which is used as the objective function. This allows the charge / discharge instruction amount Wc* to be set so that the charge / discharge amount is greater during periods of high reliability R, as illustrated in Figure 4. In the comparative example, for example, if the predicted power generation amount Wgest or predicted power demand Wpd is incorrect in the area enclosed by the dashed line in Figure 4, the battery 36 will be charged and discharged using power from the power grid 62 during that period. In the embodiment, since the charge / discharge amount is increased during periods of high reliability R, the wasted charge / discharge of power between the power grid 62 and the battery 36 is suppressed, and more appropriate energy management can be achieved.

[0031] According to the supply and demand management system 10 incorporating the power management system of the embodiment described above, more appropriate energy management can be achieved by charging and discharging the battery 36 during time periods when the reliability R of the forecasts for power generation and power demand is high, based on the forecast power generation amount Wgest and forecast power demand Wpd for each time period.

[0032] Furthermore, by setting the time periods for charging and discharging the battery 36 and the charge / discharge instruction Wc* so as to minimize the cumulative value obtained by dividing the charge / discharge instruction Wc* for each time period by the reliability R, and by charging and discharging the battery 36 with the charge / discharge instruction Wc* set for each time period, more appropriate energy management can be achieved.

[0033] Furthermore, by setting the reliability R lower for low-reliability time periods, which are predetermined as time periods where at least one of the power generation forecast or the power demand forecast is likely to be incorrect, compared to time periods other than the predetermined time periods, the time periods for charging and discharging the battery 36 can be appropriately set, enabling more appropriate energy management.

[0034] In this case, by making the power generation system 16 a system that generates electricity using renewable energy, and by setting the low-reliability period to at least one of the following: the sunrise period, the sunset period, and the cloudy period, more appropriate energy management can be achieved.

[0035] Furthermore, by installing the battery 36 in the vehicle and designating the low-reliability period as the time when the electric vehicle 20 starts up, more appropriate energy management can be achieved.

[0036] In the power management system of the embodiment, the supply and demand management system 10 incorporates a battery 36 as an energy storage device, which is mounted on the electric vehicle 20. However, the energy storage device does not have to be mounted on the electric vehicle 20. It may be mounted on a hybrid vehicle that can run using the power of an engine and a motor, or on a moving vehicle other than an automobile, such as a train or an airplane, or it may be a stationary energy storage device that does not move.

[0037] In the power supply and demand management system 10 incorporating the power management system of the embodiment, the setting routine exemplified in Figure 3 is executed by the CPU of the power management device 70. However, at least one of the processes of the setting routine exemplified in Figure 3 may be executed by the CPU of the electronic control unit 50 mounted on the electric vehicle 20.

[0038] The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem will be explained. In the embodiment, the power management device 70 corresponds to the "power management system".

[0039] Furthermore, the correspondence between the main elements of the examples and the main elements of the invention described in the section on means for solving the problem is not intended to limit the elements of the invention described in the section on means for solving the problem, as the examples are merely one example to specifically illustrate a form for carrying out the invention described in the section on means for solving the problem. In other words, the interpretation of the invention described in the section on means for solving the problem should be based on the description in that section, and the examples are merely one specific example of the invention described in the section on means for solving the problem.

[0040] Although embodiments for carrying out the present invention have been described above using examples, the present invention is not limited in any way to these embodiments, and can be carried out in various forms without departing from the spirit of the present invention. [Industrial applicability]

[0041] This invention can be used in industries such as the manufacturing of power management systems. [Explanation of Symbols]

[0042] 10 Supply and demand management system, 12 Distributed power system, 20 Electric vehicle, 22a, 22b Drive wheels, 24 Differential gear, 26 Drive shaft, 32 Motor, 34 Inverter, 36 Battery, 36a Voltage sensor, 36b Current sensor, 36c Temperature sensor, 38 Power line, 40 Charge / discharge device, 41 Vehicle-side connector, 50 Electronic control unit, 52 Ignition switch, 54 Vehicle speed sensor, 56 Accelerator pedal, 58 Accelerator pedal position sensor, 60 Supply and demand management server, 62 Power grid, 70 Power management device, 72 Network, 92 Management device, 120 Vehicle group.

Claims

1. A power management system for managing at least one power generation system connected to a power grid and at least one energy storage device connected to the power grid, Based on the predicted power generation amount, which is the amount of power generated by the power generation system for each time period, and the predicted power demand, which is the power demand in the power grid, the energy storage device is charged and discharged during time periods when the reliability of the predictions for the power generation amount and power demand for each time period is high. Power management system.

2. A power management system according to claim 1, The charge / discharge instruction amount for each time period is set to minimize the cumulative value obtained by dividing the charge / discharge instruction amount for the energy storage device for each time period by the reliability, and the energy storage device is charged and discharged according to the charge / discharge instruction amount set for each time period. Power management system.

3. A power management system according to claim 1 or 2, The reliability is set lower for predetermined time periods that are designated as times when at least one of the power generation forecast and the power demand forecast is likely to be inaccurate, compared to time periods other than those designated. Power management system.

4. A power management system according to claim 3, The aforementioned power generation system generates electricity using renewable energy, The aforementioned predetermined time period is at least one of the following: the time of sunrise, the time of sunset, and the time of cloudy weather. Power management system.

5. A power management system according to claim 3, The aforementioned energy storage device is mounted on a vehicle, The aforementioned predetermined time period is the time period during which the vehicle departs. Power management system.

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