JP2004222456A - Power storage system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power storage system wherein nighttime power can be effectively utilized and use of daytime power can be suppressed even if the power demand from a load exceeds the output capacity. <P>SOLUTION: The power storage system comprises: a two-way power converter 2 which functions as a converter when charging a storage battery 30 and as an inverter when discharging; a power selecting means 1 which is provided between a commercial power source 10, the two-way power converter 2 and the load 20, and selects power by switches MS1, MS2, and MS3; and a controlling means 4 which controls the switches. The switches MS1, MS2, and MS3 are controlled according to the modes: nighttime operation mode for nighttime electricity rate applied time period in which mode the storage battery 30 is charged and the load 20 is powered by the commercial power source 10; in the daytime discharge operation mode in which the load 20 is supplied with power only from the storage battery 20, and systematic supplementing operation mode in which the load 20 is supplied with power concurrently from the commercial power source 10 and the storage battery 30 according to the power consumption of the load 20. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention uses a power company's hourly contract menu to store nighttime electric power and discharge it during a time period other than the nighttime electric power supply time period, thereby reducing electric bills and leveling load. About the system.
[0002]
[Prior art]
Electricity companies set the power generation capacity by nuclear power, hydropower, thermal power generation, etc., so that they can respond to the peak power consumed during daytime and specific time periods, and control the power supply while forecasting the power demand are doing. The demand for power is increasing in urban areas, and the increase in peak power has led to an increase in the burden of constructing new power generation facilities. On the other hand, during nighttime, the power usage rate of the factory or office is reduced, so that the power usage rate is reduced. A nighttime power use promotion discount system has been implemented for the purpose of leveling out such a large difference between daytime and nighttime power demand. Nighttime power is cheaper than daytime power, and has a low proportion of fossil fuels, so it emits less carbon dioxide, which is convenient for global environmental protection.
[0003]
There are two types of nighttime power utilization technologies: a method of storing the power itself, a method of converting it to heat energy such as hot water supply equipment and ice heat storage, and a method of storing it as positional energy, such as pumped storage power generation. It is considered. Among them, a typical method of storing power is a power storage system that stores nighttime power in a storage battery and consumes power from the storage battery during daytime when the power load is large. According to this power storage system, there is an effect of reducing the power usage fee for the consumer, and it is possible to level up the power system from the bottom up and by suppressing the peak power during the daytime.
[0004]
However, it naturally happens that the power consumption during the daytime is greater than the capacity of the storage battery.
As a countermeasure for such a case in which a power supply equal to or larger than the storage capacity is performed to a load, for example, Japanese Patent Application Laid-Open No. 2000-308282 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2000-295784 (Patent Document 2) disclose. In some cases, a system switching means is provided to switch the power supply to the load from the storage battery to the commercial power when the load exceeds the capacity of the storage battery.
[0005]
As another countermeasure, for example, as disclosed in Japanese Patent Application Laid-Open No. 2001-008385 (Patent Document 3), several types of storage battery discharge patterns per day are stored in advance, and the user appropriately selects the pattern. Therefore, there is an electric power storage system in which nighttime electric power charged in a storage battery is used effectively and without waste.
[0006]
Further, Japanese Patent Application Laid-Open Nos. Hei 10-201129 (Patent Document 4) and Hei 10-201130 (Patent Document 5) disclose the use of a solar cell for daytime charging of a storage battery.
[0007]
[Patent Document 1] JP-A-2000-308282 [Patent Document 2] JP-A-2000-295784 [Patent Document 3] JP-A-2001-008385 [Patent Document 4] JP-A 10-201129 [Patent] Document 5: JP-A-10-201130
[Problems to be solved by the invention]
As described above, in the power storage systems proposed in Patent Documents 1 to 5, when the storage power of the storage battery connected to the load decreases, the power storage system cannot respond to the power request of the load. Power. However, a situation occurs in which the power stored in the cheap nighttime electricity rate band is not effectively used up, and the power of the daytime electricity rate is used, so that the purpose of the power storage system has not been sufficiently achieved.
[0009]
Therefore, the present invention is to reduce the effective use of nighttime power and the suppression of daytime power by effectively using up the power stored in the power storage means even when the load requests a power larger than the output capacity. It is an object of the present invention to provide a power storage system which can be used.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, a power storage system of the present invention includes a rectifier that converts commercial power into DC power, a power storage unit that stores rectified DC power, and a DC power stored in the power storage unit. Power conversion means for converting AC power substantially equal to the voltage and frequency of the commercial power, and power selection means for selectively supplying the AC power converted by the commercial power and the power conversion means to a load by switching a plurality of switches And control means for controlling a plurality of switches of the power selection means, wherein the control means supplies power from the commercial power to the power storage means via the rectification means during a nightly charge application time zone. In addition, in the night operation mode for supplying power to the load, and in a time zone other than the night rate application time zone, when the power consumption of the load is less than a predetermined value, the storage is performed. A discharge operation mode for supplying power to the load only from the means, and when the power consumption of the load is equal to or more than the predetermined value, the commercial power and the power supply to the load from the power storage unit are performed in parallel. The plurality of switches are controlled in accordance with each of the system replenishment operation modes to be performed.
[0011]
In the present invention, when discharging from the power storage means other than the nightly charge application time zone, even when a load requires a power greater than the output capacity, by effectively using up the power stored in the power storage means, Effective use of nighttime power and use of daytime power can be suppressed.
[0012]
The rectifier and the power converter are bidirectional power converters having both functions, so that they operate as a converter when charging the power storage unit, and discharge power from the power storage unit to a load. During operation, it is controlled to operate as an inverter.
[0013]
The power selection means has a first input terminal connected to commercial power via a first switch, a second input terminal connected to the power conversion means via a second switch, and a first input terminal connected to the first input terminal. A predetermined intermediate tap between the second input terminals is connected to the load, and an autotransformer in which a third switch is connected between the first input terminal and the second input terminal, The power from the two AC power supplies can be balanced and supplied to the load in parallel without using a complicated power adjustment circuit.
[0014]
Further, by providing a power failure detection means and a circuit breaker for shutting off the commercial power supply on the commercial power side of a connection point between the output section of the power storage means and the commercial power, the output of the power storage means and the commercial power supply during power supply of the commercial power supply are provided. While the current is being balanced, power is supplied to a predetermined load, and upon detecting a power failure of the commercial power supply, the circuit breaker is opened immediately and the output control of the power storage means is allowed to operate independently, and after the self-sustaining operation starts, the full load current of the predetermined load is reduced. The power can be controlled to be supplied by the power storage means. As a result, it is possible to prevent reverse power flow to the commercial power system that occurs when the power storage unit performs the self-sustaining operation.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a power storage system of the present invention will be described with reference to FIGS.
[0016]
FIG. 1 is a block diagram (single line diagram) showing a configuration of an embodiment of a power storage system according to the present invention. In FIG. 1, a power storage system according to the present embodiment includes a power source selecting unit 1 for switching power supply from a commercial power source 10 and a storage battery 30 constituting a power storage unit 3 to a load 20, and an AC power source from the commercial power source 10 Bidirectional power converter 2 having both functions of a converter for converting DC power for charging battery 30 and an inverter for converting DC power stored in storage battery 30 to AC power, and power storage means 3 including storage battery 30 And a control means 4 for controlling the power selection means 1 and the bidirectional power converter 2. Further, when a power failure occurs in the commercial power supply, an opening / closing means for detecting the power failure and preventing reverse power flow from the present system to the commercial power supply side is provided.
[0017]
The power selection means 1 includes three changeover switches MS1, MS2, MS3 and an autotransformer (also called a balance transformer) 11.
[0018]
The main conversion unit of the bidirectional power converter 2 is configured by the switching element 12 so as to operate as a converter when charging the storage battery 30 and to supply power from the storage battery 30 to the load 20 by discharging. It is controlled by the switching control unit 13 to operate as an inverter. By controlling the switching element 12 in this way, the alternating current waveform of the bidirectional power converter 2 is controlled so as to match the reference sine wave, thereby enabling bidirectional power conversion in which charging and discharging can be performed.
[0019]
Specifically, the following switching control is performed.
(1) The switching voltage is input to the switch element 12 to give a command to perform a switching operation, and the input voltage is pulsed.
(2) Control is performed so that this pulse becomes a sine wave in an arbitrary section.
(3) This sine wave makes the charging current a sine wave during charging, and makes the output voltage a sine wave during discharging.
(4) This control enables bidirectional power conversion in the bidirectional power converter 2.
[0020]
When the pulse width during the switching control is increased, the current and the voltage are increased, and when the pulse width is reduced, the current and the voltage are decreased. The storage means 3 is charged at a constant current with an arbitrary current. When the charge amount approaches the charge amount, the pulse width is reduced to reduce the charge current, and charging is performed until the charge amount is completed. During the discharging operation, the discharge of the power storage means 3 can be controlled by changing the pulse width and the inverter output voltage.
[0021]
(1) The switching voltage is input to the switch element 12 to give a command to perform a switching operation, and the input voltage is pulsed.
(2) On / off operation is performed in an arbitrary section (100 μS in this configuration). The current value in an arbitrary section is determined by utilizing the fact that the current increases when the element is on and decreases when the element is off. This current value increases as the pulse width of the ON state in an arbitrary section increases, and decreases when the pulse width decreases. By utilizing this, the pulse width is controlled so that the current value becomes a sine wave in the entire arbitrary section (here, 8 mS).
(3) When charging the sine wave, the storage battery is charged as a DC current by smoothing with the capacitor C. At the time of discharging, the power is supplied to the load at the same frequency as the commercial frequency. Further, when performing a system replenishment operation from a commercial operation, the inverter output is performed in synchronization with the commercial frequency.
(4) These controls enable bidirectional power conversion in the bidirectional power converter 2.
[0022]
The bidirectional power converter 2 is provided with a reactor L and a smoothing capacitor C, and smoothes a charging current to the storage battery 30. Further, a transformer 15 is provided between the power selection means 1 and the bidirectional power converter 2 to step down when the storage battery 30 is charged and to step up when discharging the storage battery 30.
[0023]
The power storage means 3 is provided with a temperature sensor 14 for detecting the temperature of the storage battery 30.
[0024]
The control means 4 is constituted by a CPU in the present embodiment, and controls each switch of the power selection means 1 based on the voltage and current of the commercial power supply, the output voltage and current, the voltage of the storage battery, and the time information of the internal timer. And controls the inverter function and the converter function of the bidirectional power converter 2.
[0025]
The principle of operation of the autotransformer 11 is shown in FIG. Assuming that the number of turns on the input 1 side of the autotransformer 11 is n1 and the number of turns on the input 2 side is n2, the relationship between the current I1 from the input 1 side flowing to the output side and the current I2 from the input 2 side is equal amperes. By the law of turn,
I1 * n1 = I2 * n2
Is represented by When the output is the intermediate tap of the autotransformer 11, n1 = n2, and therefore I1 = I2. By utilizing this principle, a system replenishment operation from the commercial power supply 10 and the storage battery 30 is performed.
[0026]
When the winding ratio of the intermediate lead terminal is n1: n2 (n1 ≠ n2), the use of the autotransformer 11 enables n2 / n1 times the inverter output. As for the turns ratio, a sliderack, tap switching and other switching means can be used.
In this way, even when the output of the storage battery is reduced, by supplying the commercial power by changing the winding ratio, power can be supplied to the load in any way up to the discharge limit of the storage battery.
[0027]
Next, the operation in the present embodiment will be described with reference to the flowcharts of FIGS. 3 to 7 and the system connection diagrams of FIGS.
[0028]
1. Steady-state operation In step 100 shown in FIG. 3, it is determined whether the current time is in a discharge start time zone, that is, a time zone other than a nightly charge time zone. This can be done by using a timer (not shown) inside the CPU of the control device 4 to measure time. If it is the discharge start time zone, it is determined in step 110 whether the discharge start condition is satisfied.
The discharge start conditions in this example are the remaining amount of the storage battery power, the storage battery temperature, and the discharge time zone.
[0029]
If the condition is satisfied, it is determined in step 120 whether the load power is equal to or greater than a set value (3 kVA in this example). If it is less than the set value, the switches MS2 and MS3 of the power selection means 1 are turned on in step 130, and the "battery" independent operation mode using only the storage battery 30 is set (FIG. 10). If the load power is equal to or greater than the set value, all switches MS1, MS2 and MS3 of the power selecting means 1 are turned on in step 140 to set the system replenishment operation mode for supplying commercial power to the "battery" independent operation (FIG. 11). ). When the operation mode is determined, the discharge operation output control of step 150 is performed.
[0030]
In step 160, the discharge operation continuation conditions such as the remaining amount of the storage battery, the storage battery temperature, and the discharge time zone are monitored. If the condition is not satisfied, the discharge operation is stopped and the discharge amount is recorded in step 170. For this purpose, the discharge amount monitoring process of step 180 is always performed. In step 190, the switch MS2 of the power selection means 1 is opened, and the switches MS1 and MS3 are closed to switch the power distribution to commercial operation (FIG. 8).
[0031]
2. Unsteady operation When a power failure occurs in step 200 shown in FIG. 4, the current operation state is determined in step 210. If it is the charging mode, the charging operation unsteady process is performed in step 220. If it is the discharge mode (including the system replenishment operation mode), the discharge operation unsteady process is performed in step 230. If it is in the commercial operation mode, the commercial operation unsteady process is performed in step 240. In step 250, the depth of discharge is determined.
If the depth of discharge is exceeded, at step 260, an equal charge request flag is set.
[0032]
That is,
(1) In the non-stationary operation, when the storage capacity is reduced by supplying power from the storage battery to the load and reaches the depth of discharge, the operation of step 260 is performed. During this time, commercial power is down.
(2) When the commercial power returns from the power failure, the system shifts from the unsteady operation to the steady operation (commercial operation). At this time, if the flag is set, charging is performed during the charging time zone.
In step 270, power failure occurrence recording is performed. (FIG. 12)
[0033]
3. Charge control (1)
In step 300 shown in FIG. 5, it is determined whether or not the charging time period. If it is the charging time zone, it is determined in step 310 whether or not charging is necessary. If charging is necessary, the switches MS1, MS2 and MS3 of the power selecting means 1 are turned on in step 310 and the bidirectional power converter 2 Charge from commercial power supply (FIG. 9).
[0034]
4. Battery temperature monitoring In step 400 of FIG. 6, the temperature at the start of charging is recorded. In step 410, the current battery temperature value measured by the temperature sensor 14 is compared with the temperature at the start of charging.
In step 420, it is determined whether or not charging has been completed. If charging has not been completed, it is determined whether or not the temperature has risen by 6 ° C. or more. If there has been a temperature rise, a charging stop flag is set in step 440 to stop charging. I do.
[0035]
5. Charge control (2)
In step 500 of FIG. 7, battery voltage detection and battery temperature detection processing are performed. In step 510, various charging amounts are set.
Here, the various charging amounts refer to a current value setting when performing charging by gradually reducing the charging current value until reaching the charging electric amount when performing the charging operation.
Next, at step 520, low-current charging is performed. In step 530, it is determined whether or not the charged amount has been reached, and if it has, the battery voltage determination process is performed in step 540.
[0036]
【The invention's effect】
As described above, according to the present invention, when the power consumption of the load is equal to or more than the predetermined value in a time zone other than the nighttime charge application time zone, the power supply to the load from the commercial power and the power storage means to the load is performed. Function in parallel, the power stored in the power storage means is effectively used up even when the load requires a power larger than the output capacity, so that nighttime power can be effectively used and daytime power can be used. Can be suppressed.
[0037]
The rectifying means and the power converting means are bidirectional power converters having both functions, so that they operate as converters when charging the power storage means, and when discharging power from the power storage means to the load. Is controlled to operate as an inverter.
[0038]
By configuring the power selection means with three switches and an autotransformer, the power from the two AC power supplies can be balanced and supplied to the load in parallel without combining a complicated power adjustment circuit.
[0039]
By providing a switch that shuts off commercial power between the commercial power and providing a power failure detection means on the commercial power side of the switch, if a power failure occurs on the commercial power side, by opening the switch, It is possible to prevent reverse power flow to the commercial power system that occurs when the power storage means performs an independent operation.
[Brief description of the drawings]
FIG. 1 is a block diagram (single line diagram) illustrating a configuration of an embodiment of a power storage system according to the present invention.
FIG. 2 is an explanatory diagram showing an operation of the autotransformer in the embodiment of the present invention.
FIG. 3 is a flowchart illustrating an operation of a control unit according to the embodiment of the present invention.
FIG. 4 is a flowchart illustrating an operation of a control unit according to the embodiment of the present invention.
FIG. 5 is a flowchart illustrating an operation of a control unit according to the embodiment of the present invention.
FIG. 6 is a flowchart illustrating an operation of a control unit according to the embodiment of the present invention.
FIG. 7 is a flowchart illustrating an operation of a control unit according to the embodiment of the present invention.
FIG. 8 is an explanatory diagram of each operation mode in the embodiment of the present invention.
FIG. 9 is an explanatory diagram of each operation mode in the embodiment of the present invention.
FIG. 10 is an explanatory diagram of each operation mode in the embodiment of the present invention.
FIG. 11 is an explanatory diagram of each operation mode in the embodiment of the present invention.
FIG. 12 is an explanatory diagram of each operation mode in the embodiment of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 power selection means 2 bidirectional power converter 3 power storage means 4 control means 10 commercial power supply 11 autotransformer 12 switching element 13 switching control unit 14 temperature sensor 15 transformer 20 load 30 storage battery

Claims (4)

Rectifying means for converting commercial power into DC power, power storage means for storing rectified DC power, and power for converting DC power stored in the power storage means into AC power substantially equal to the voltage and frequency of the commercial power Conversion means, power selection means for selectively switching the commercial power and the AC power converted by the power conversion means to a plurality of switches to selectively supply the load to a load, and control for controlling the plurality of switches of the power selection means Means,
The control means includes a night operation mode in which the night charge application time zone supplies power to the power storage means through the rectifier from the commercial power and supplies power to the load, and a night operation mode other than the night charge application time zone. In the time period, when the power consumption of the load is less than a predetermined value, a discharge operation mode for supplying power to the load only from the power storage unit, and when the power consumption of the load is equal to or more than the predetermined value. Wherein the plurality of switches are controlled in accordance with each mode of a system replenishment operation mode in which the commercial power and power supply from the power storage means to the load are performed in parallel. The power storage system according to claim 1, wherein the rectifier and the power converter are bidirectional power converters having both functions. The power selection means has a first input terminal connected to commercial power via a first switch, a second input terminal connected to the power conversion means via a second switch, and a first input terminal connected to the first input terminal. 2. An autotransformer in which a predetermined intermediate tap between the second input terminals is connected to the load, and a third switch is connected between the first input terminal and the second input terminal. Or the power storage system according to 2. The power failure detecting means and a circuit breaker for shutting off commercial power are provided on the commercial power side of a connection point between the output part of the power storage means and commercial power, and the circuit breaker according to any one of claims 1 to 3, wherein Power storage system.

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