JP7652043B2 - Energy storage system and control method thereof - Google Patents

Description

This disclosure relates to a power storage system and a control method thereof.

The number of small-scale electricity consumers, such as ordinary households, who are installing solar power generation equipment is increasing. Such solar power generation equipment can be connected to the commercial power grid via a power conversion device and the electricity can be sold. In addition, during a power outage, the power conversion device can be disconnected from the commercial power grid and operated independently, allowing independent output power to be supplied to specific loads that need to be used during the power outage.

Furthermore, in recent years, distributed power supply systems that incorporate a storage battery-equipped power storage system in addition to a solar power generation device have begun to become popular (see, for example, Patent Document 1). During a power outage, the system can supply power to a specific load within the consumer's facility through independent output, and if there is excess power that can be generated, the storage battery can be charged, making it possible to use the generated power effectively without waste.

JP 2021-35236 A

When introducing a new distributed power supply system that combines a solar power generation system with a storage battery, it is possible to connect the solar power generation panel and the storage battery to a single power conversion device with hybrid functions and perform integrated advanced control. However, when a customer who already has solar power generation equipment wants to add a storage system later while making effective use of the existing equipment, the solar power generation system and the storage system will be controlled separately. In this case, from the storage system's perspective, it is unclear how much independent output can be obtained from the solar power generation system.

The present disclosure aims to provide a power storage system and a control method thereof that can perform appropriate control without linking with a power conversion device of a solar power generation system.

This disclosure includes the following inventions, however, the inventions are defined by the claims.

Energy Storage System
The present disclosure provides a power storage system provided between a power conversion device that provides independent output by solar power generation and a load,
an AC circuit extending from an input terminal for receiving the independent output to an output terminal to which the load is connected;
a power conversion unit that is disposed between the AC circuit and the storage battery and performs bidirectional power conversion between DC and AC;
A control unit that controls the power conversion unit,
The control unit is
Accepting a setting of a sink current value as a predicted value to be received from the power conversion device;
A peak value of a load current supplied to the load is calculated as an absolute value;
Controlling the power conversion unit so that a peak value of a current sent from the AC circuit to the power conversion unit does not exceed a current value obtained by subtracting the peak value of the load current from a value that is √2 times the incoming current value.
It is a power storage system.

<<Control method of power storage system>>
The present disclosure also provides a method for controlling a power storage system when the power storage system is provided between a power conversion device that provides an independent output by photovoltaic power generation and a load, comprising:
A current draw value is set as a predicted value to be received from the power conversion device;
A peak value of a load current supplied to the load is calculated as an absolute value;
Controlling the power conversion unit so that a peak value of a current fed to the power conversion unit for charging the storage battery does not exceed a current value obtained by subtracting the peak value of the load current from a value that is √2 times the value of the incoming current.
A method for controlling a power storage system.

This disclosure provides a power storage system and a control method thereof that can perform appropriate control without linking with the power conversion device of a solar power generation system.

FIG. 1 is a diagram showing an example of the configuration of a distributed power supply system of a consumer including a power storage system. FIG. 2 is a single-line connection diagram showing the power storage system and its peripheral devices during independent operation. FIG. 3 is a flowchart showing an example of a method for determining the peak value of the charging current command value. For reference, FIG. 4 is a waveform diagram showing an example of what happens when control is performed based on effective values rather than peak values and the load is a nonlinear load. FIG. 5 is a waveform diagram showing an example of a state in which the load is a nonlinear load under peak value-aware control according to the present disclosure. FIG. 6 is a time chart showing an example of changes in the load current value and the charging current command value. FIG. 7 is a time chart showing another example of changes in the load current value and the charging current command value. 8A shows a case where the independent output is used to supply power to a specific load and charge the storage battery at the same time, while (b) shows a bypass state where the control unit stops charging and the independent output passes directly through the storage battery system. FIG. 9 is a schematic diagram showing the setting of the lead current value based on weather information. FIG. 10 is a schematic diagram showing the setting of the draw current value based on the amount of solar radiation. FIG. 11 is a schematic diagram showing the setting of the lead-in current value using a mobile information terminal (smartphone).

[Description of the embodiments of the present disclosure]
The gist of the present disclosure includes at least the following.

(1) The present disclosure relates to a power storage system provided between a power conversion device that provides an independent output by photovoltaic power generation and a load, the power storage system including an AC circuit extending from an input terminal that receives the independent output to an output terminal to which the load is connected, a power conversion unit that is between the AC circuit and a storage battery and performs bidirectional power conversion between AC and DC, and a control unit that controls the power conversion unit, the control unit receiving a setting of a draw current value as a predicted value received from the power conversion device, determining an absolute value of a peak value of a load current to be supplied to the load, and controlling the power conversion unit so that the peak value of a current sent from the AC circuit to the power conversion unit does not exceed a current value obtained by subtracting the peak value of the load current from a value that is √2 times the draw current value.

In such a storage battery system, while receiving an independent output from an external power conversion device and supplying power to a load, control is performed so that the difference between the value multiplied by √2 of the set draw current value (fixed value) and the peak value of the load current becomes the peak value of the current (AC) for charging the storage battery. Therefore, the storage battery system can perform appropriate control based on the draw current value that it has set itself, without the need to communicate with an external power conversion device. Furthermore, even in the case of a nonlinear load, control can be performed to suppress the stoppage of the external power conversion device.

(2) In the energy storage system of (1), when the peak value of the load current is greater than a value that is √2 times the value of the draw current, the control unit may stop operation of the power conversion unit.
In this case, theoretically the current value obtained by subtracting the peak value of the load current from √2 times the draw current value will be negative. However, in reality, the solar power generation will be able to provide the load with a current (power) greater than or equal to the set draw current value, so it is appropriate not to charge or discharge the storage battery.

(3) In the energy storage system of (1) or (2), a remote control device may be provided that is electrically connected to the control unit and has an operation reception function, and the draw current value may be set for the control unit by the remote control device.
In this case, the incoming current value can be arbitrarily set from the remote control device.

(4) In the power storage system of (3), the sink current value may be a value selected by a user from a plurality of candidate values displayed on the remote control device.
In this case, the user can select and set the lead-in current value from the candidate values that serve as a guideline.

(5) In any of the power supply systems (1) to (4), when distortion of a predetermined value or more occurs in the isolated output from the power conversion device, the control unit can stop operation of the power conversion unit and establish a bypass state directly from the input terminal to the output terminal.
Operating the power conversion unit of the energy storage system may affect the operation of the power conversion device of the solar power generation, causing distortion in the independent output (voltage). In this case, if the power conversion device that detects the distortion stops, the power that can be generated cannot be utilized. Therefore, by stopping the power conversion unit of the energy storage system and putting it into a bypass state, it is possible to prevent the power conversion device from stopping. This allows the independent output from the solar power generation to be used continuously.

(6) In the power storage system of (5) above, when the distortion becomes less than the predetermined value, the control unit may operate the power conversion unit to charge the storage battery.
Since distortion may occur temporarily, it is preferable to operate the power conversion unit and charge the storage battery when the distortion falls below a predetermined value in order to make full use of the power generated by solar power.

(7) In the power storage system of (5) above, when the storage battery is fully charged even if the distortion becomes less than the predetermined value, the control unit may continue the bypass state.
In this case, since the storage battery cannot be further charged, it is preferable to continue the bypass state to supply power to the load.

(8) In the energy storage system of (3), the remote control device is connected to a server that stores weather-related information via a telecommunications line, and the remote control device can also set the draw current value based on the information obtained from the server.
Since the amount of power generated by solar power generation is greatly affected by the weather, it is possible to set an appropriate draw current value depending on the weather.

(9) The power storage system according to (3) may further include an actinometer that detects an amount of solar radiation, and the remote control device may set the draw current value based on the amount of solar radiation obtained from the actinometer.
Since the amount of power generation can be estimated from the amount of solar radiation, an appropriate draw current value can be set based on the estimated amount of power generation.

(10) In the energy storage system of (3), the remote control device may obtain information on past power generation from the power conversion device for solar power generation, and the remote control device may set the draw current value based on the information.
Since the current amount of power generation can be estimated from information on the amount of power generation in the past, an appropriate draw current value can be set based on the estimated amount of power generation.

(11) The energy storage system of (3) may further include a mobile information terminal capable of communicating with the remote control device, and the remote control device may receive a setting of the draw current value from the mobile information terminal and, if the set draw current value is greater than a value equivalent to the amount of power generated by solar power generation, send information to the mobile information terminal prompting the mobile information terminal to change the setting.
In this case, the draw current value can be set from the mobile information terminal. If the set draw current value is not appropriate, information is received prompting a change of setting, and the draw current value can be changed. If the draw current value is greater than the amount of power generated by the solar power generation system, the power conversion device of the solar power generation system will stop, but this can be avoided by changing the setting.

(12) The present disclosure relates to a control method for a power storage system when a power storage system is provided between a power conversion device that provides independent output by photovoltaic power generation and a load, the control method for a power storage system setting a draw current value as a predicted value to be received from the power conversion device, determining an absolute peak value of a load current to be supplied to the load, and controlling the power conversion unit so that the peak value of a current sent to a power conversion unit that charges a storage battery does not exceed a current value obtained by subtracting the peak value of the load current from a value that is √2 times the draw current value.

According to this control method for the energy storage system, while receiving an independent output from an external power conversion device and supplying power to a load, control is performed so that the difference between the value multiplied by √2 of the set draw current value (fixed value) and the peak value of the load current becomes the peak value of the current (AC) for charging the storage battery. Therefore, the energy storage system can perform appropriate control based on the draw current value that it has set itself, without the need to link with an external power conversion device. Furthermore, even in the case of a nonlinear load, control can be performed to suppress the stoppage of the external power conversion device.

[Details of the embodiment of the present disclosure]
Hereinafter, specific examples of the power storage system according to the present disclosure will be described with reference to the drawings.

<An example of a distributed power system>
FIG. 1 is a diagram showing an example of the configuration of a distributed power supply system of a consumer including a power storage system. In the diagram, a photovoltaic power generation panel 2 is installed on the roof of a consumer 1. The photovoltaic power generation panel 2 is connected to a power conversion device (power conditioner) 3. The output side of the power conversion device 3 is connected to a general load distribution board 4. The general load distribution board 4 is connected to a commercial power system 7 via a power selling power meter 5 and a power purchasing power meter 6. A power storage system 8 is connected to the general load distribution board 4 at AC 100V/200V. The general load distribution board 4 is also connected to a specific load distribution board 9 at AC 100V. Up to this point, the commercial power system 7 is connected in a normal state.

When the commercial power grid 7 experiences a power outage, the power conversion device 3 can disconnect itself from the commercial power grid 7 and operate independently. During independent operation, an independent output of 100V AC is provided to the storage system 8. The storage system 8 supplies 100V AC to the specific load distribution board 9.

A remote control device 8r (also a part of the power storage system 8) is connected to the power storage system 8. The remote control device 8r can be used to operate the power storage system 8 and also to display the operating status. The remote control device is connected to the router 10 via Wi-Fi (Wi-Fi is a registered trademark). The router is connected to the Internet.

Energy Storage System
Next, the power storage system 8 during independent operation will be described.
2 is a single-line connection diagram showing the power storage system 8 and its peripheral devices during independent operation. The independent output of the power conversion device 3 is input to an input terminal 8 _in , which serves as an auxiliary input to the power storage system 8. A specific load distribution board 9 is connected to an output terminal 8 _out of the power storage system 8. A specific load 11 to which it is desired to continue supplying power even during a power outage is connected to the specific load distribution board 9.

The power storage system 8 includes a voltage sensor 80, a switch 81, current sensors 82 and 83, a power conversion unit 84, a storage battery 85, a BMS (Battery Management System) 86, a control unit 87, and an external remote control device 8r, which are connected as shown in the figure. When the switch 81 is closed, an AC circuit 88 is formed from an input terminal 8 _in to an output terminal 8 _out . The voltage at the input terminal 8 _in is detected by the voltage sensor 80. The current flowing through the specific load 11 is detected by the current sensor 82. The power conversion unit 84 is connected to a branch point 88j of the AC circuit 88. The current flowing between the branch point 88j and the power conversion unit 84 is detected by the current sensor 83. The power conversion unit 84 is a bidirectional inverter main circuit, and can charge or discharge the storage battery 85.

The opening and closing of the switch 81 and the switching operation of the power conversion unit 84 are controlled by the control unit 87. The detection output of the voltage sensor 80, the detection output of the current sensors 82 and 83, and the monitoring signal of the BMS 86 are sent to the control unit 87. The BMS 86 sends the SOC (State of Charge) of the storage battery 85 and other information to the control unit 87. The control unit 87 is a computer system including, for example, a CPU and memories such as ROM and RAM (not shown), and the CPU executes software (computer programs) to realize the necessary control functions. The software is stored in the memory.

In the energy storage system 8 configured as described above, when the voltage of the independent output from the power conversion device 3 is input to the energy storage system 8, the voltage sensor 80 detects this, and the control unit 87 closes the switch 81. The input current value flowing from the power conversion device 3 to the energy storage system 8 is Iin, the load current value flowing from the energy storage system 8 to the specific load 11 is Iout, and the current flowing from the branch point 88j to the power conversion unit 84, i.e., the charging current command value, is Ibat.

The user can also set the draw current value Ipv in the remote control device 8r as a predicted value of the AC current to be drawn from the power conversion device 3 to the power storage system 8 for the control unit 87. The set value can be selected from, for example, one of three values: 5 A, 10 A, and 14 A. This is an example of a stepped value with the upper limit set to the rated maximum value of 1500 W for independent output. Note that these set values are merely examples, and it is also possible to set them in more finely stepped values.

Here, the input current value Iin (= Iout + Ibat) is not an amount determined by the power conversion device 3, but depends on how much current is drawn. Also, the maximum current (maximum power) that the power conversion device 3 can output depends on the amount of solar radiation, so it is not always possible to ensure a constant value. Therefore, it is unknown to the storage system 8 how much current can actually be drawn as the input current value Iin.

Therefore, using the incoming current value Ipv as a provisional predicted value, the relationship between the peak value Ibat_peak, which is a value that is √2 times the charging current command value Ibat (effective value), the peak value Iout_peak, which is a value that is √2 times the load current value Iout as an effective value, and the charging current command value Ipv (effective value) is expressed as the following formula (1) or (1a). Note that each value is an absolute value.
When Ipv×√2>Iout_peak,
Ibat_peak=Ipv×√2−Iout_peak (1)
When Ipv×√2≦Iout_peak,
Ibat_peak=0...(1a)
According to formula (1), the current value obtained by subtracting the peak value of the load current from the value √2 times the set draw current value becomes the upper limit of the peak value of the charging current command value. The charging current command value Ibat (effective value) is (1/√2) of the peak value Ibat_peak. However, when Ibat_peak is a negative value in the calculation of formula (1), it means that a peak value of the load current exceeding √2 times the draw current value is being provided as an independent output, so charging is not performed, and the peak value of the charging current command value Ibat_peak = 0 according to formula (1a).

Figure 3 is a flowchart showing an example of how to calculate the peak value of the charging current command value Ibat. First, in step S1, the control unit 87 (Figure 2) continues to update the absolute value of the instantaneous value of the load current to the larger value in sequence between zero crossings and the next zero crossings based on the detection output of the current sensor 82 (Figure 2), and sets the maximum value as the peak value Iout_peak. Note that this calculation may be performed after filtering such as moving average to remove noise. It may also be performed in one cycle or multiple cycles. Next, the control unit 87 compares the value of √2 times the draw current value Ipv with the peak value Iout_peak of the load current (step S2), and if Ipv x √2 > Iout_peak (YES), proceed to step S4, and if Ipv x √2 ≦ Iout_peak (NO), proceed to step S3.

When the process proceeds to step S4, the control unit 87 checks the SOC of the storage battery 85 from the information of the BMS 86, and if the SOC is 100% (or an upper limit value close to that), the process proceeds to step S3, and if charging is possible, the process proceeds to step S5. In step S3, the peak value Ibat_peak of the charging current command value is set to 0 (no charging). In step S5, the peak value Ibat_peak of the charging current command value is set to Ibat_peak = Ipv × √2 - Iout_peak according to formula (1), and the storage battery 85 is charged.

For reference, Figure 4 is a waveform diagram showing an example of what happens when control is performed with an effective value in mind, rather than a peak value as described above, and the load is nonlinear. The horizontal axis is time, which is common to (a) to (d). (a) shows the actual current waveform when the incoming current value is Ipv. Since the incoming current value Ipv is an effective value, the peak value (wave height value) of the current waveform is Ipv x √2 in absolute value.

Figure 4 (b) is a waveform diagram showing an example of the load current Iout flowing through a nonlinear load. In this case, the peak value is Iout_peak in absolute value. Because it is not a continuous sine wave, the effective value is relatively small. If it is considered that the charging current command value Ibat can be increased accordingly, the waveform will be, for example, (c). In this case, the peak value is Ibat_peak in absolute value.

However, when the instantaneous values of (b) and (c) are superimposed, the input current value Iin from the power conversion device 3 takes the waveform of (d). At times t1 and t2, the peak value of Iin exceeds the peak value of the incoming current value Ipv. In this case, the power conversion device 3 may stop. In other words, while it would not stop at the effective value level, it may stop unnecessarily at the peak value level.

Figure 5 is a waveform diagram showing an example of the state that occurs when the load is a nonlinear load and control is performed with peak values in mind as shown in equation (1). The horizontal axis is time, which is common to (a) to (d). (a) shows the actual current waveform when the draw current value is Ipv. Since the draw current value Ipv is an effective value, the peak value (wave height value) of the current waveform is Ipv x √2 in absolute value.

Figure 5 (b) is a waveform diagram showing an example of the load current Iout flowing through a nonlinear load. In this case, the peak value is Iout_peak in absolute value. From equation (1), the peak value Ibat_peak of the charging current command value is Ipv × √2 - Iout_peak. (c) is a waveform diagram of this charging current command value Ibat. In this case, the peak value is Ibat_peak in absolute value. As is clear from a comparison with Figure 4 (c), the charging current command value Ibat is suppressed.

The input current value Iin from the power conversion device 3 has a waveform (d) that is a superposition of the instantaneous values (b) and (c) in FIG. 5. Peak values of Iin occur at times t1 and t2, but do not exceed the peak value of the draw current value Ipv. Therefore, unnecessary shutdowns of the power conversion device 3 are suppressed.

Next, FIG. 6 is a time chart showing an example of the change in the load current value and the charging current command value. It is assumed that the current of the independent output is a constant value, and the draw current value Ipv is set to 10 A (peak value 14.1 A). When the load current value is 0 A, the peak value Ibat_peak of the charging current command value is 14.1 A according to formula (1). When the peak value Iout_peak of the load current increases to 9.9 A, the peak value Ibat_peak of the charging current command value becomes 4.2 A according to formula (1). When the peak value Iout_peak of the load current increases to 18.4 A, the peak value Ibat_peak of the charging current command value becomes 0 A (charging stopped) according to formula (1a).

Figure 7 is a time chart showing another example of the change in the load current value and the charging current command value. It is assumed that the current of the independent output is a constant value, and the draw current value Ipv is set to 14 A (peak value 19.8 A). When the load current value is 0 A, the peak value Ibat_peak of the charging current command value is 19.8 A according to formula (1). When the peak value Iout_peak of the load current increases to 9.9 A, the peak value Ibat_peak of the charging current command value becomes 9.9 A according to formula (1). When the peak value of the load current increases to 18.4 A, the charging current command value Ibat_peak becomes 1.4 A according to formula (1).

<Input voltage distortion>
2, when the power conversion device 3 is operating independently and the power conversion unit 84 of the power storage system 8 is also charging, for example, the difference in switching frequency between the two may cause mutual interference, resulting in distortion of the voltage of the independent output. The distortion can be easily detected by the voltage sensor 80 and the control unit 87 that receives the detection output from the voltage sensor 80, by comparing it with an ideal sine wave voltage.

Figure 8 (a) shows a case where the independent output is simultaneously supplying power to the specific load 11 and charging the storage battery 85. In this state, if the control unit 87 detects that the voltage of the independent output is distorted by a predetermined value or more, the control unit 87 stops charging and switches to state (b). In state (b), the power conversion unit 84 stops switching, and the independent output goes into a bypass state where it passes directly through the storage system 8. This makes it possible to eliminate distortion in the voltage of the independent output.

If the above distortion is left unchecked, the power conversion device 3 itself will detect an abnormality in the output voltage and stop operation. When operation stops, the switch 81 opens and the power storage system 8 discharges the storage battery 85 to provide independent output to the specific load 11. However, this does not allow for effective use of the independent output from solar power generation. There is more energy wasted by not being able to effectively use the energy of solar power generation than by stopping the charging of the power storage system 8. Therefore, by stopping charging, the power storage system 8 can prevent the power conversion device 3 from stopping operation and can stably supply independent output from solar power generation to the specific load 11.

After charging is stopped, if the distortion falls below a predetermined value, the control unit 87 resumes the switching operation of the power conversion unit 84 and performs charging. Since distortion may occur temporarily and not reoccur, it is preferable to perform charging proactively from the perspective of effective energy utilization. However, even if the distortion falls below the predetermined value, if the SOC of the storage battery 85 is fully charged, the control unit 87 continues the bypass state.

<Options for setting the lead-in current value>
As described above, the lead-in current value Ipv can be manually set by the user on the remote control device 8r. However, the setting method is not limited to this. Other setting methods will be described below. Note that the following setting methods may be used in combination with each other.

Figure 9 is a schematic diagram showing the setting of the draw-in current value based on weather information. The remote control device 8r of the power storage system 8 is communicatively connected to the weather information server 100 via the Internet. The amount of power generated by solar power generation is affected by the weather. Therefore, the remote control device 8r can acquire weather information at any time and change the setting of the draw-in current value Ipv according to the amount of power generated estimated from the weather information. For example, if the weather information is sunny, the maximum setting value can be used, if it is cloudy, the intermediate setting value can be used, and if it is raining, the minimum setting value can be used. In addition, taking into account the probability of precipitation, the draw-in current value can be set higher when the probability of precipitation is low, and lower when the probability of precipitation is high.

Figure 10 is a schematic diagram showing the setting of the draw-in current value based on the amount of solar radiation. The remote control device 8r of the power storage system 8 is connected to an actinometer 200 provided near the solar power generation panel 2. The amount of power generated by solar power generation is closely related to the amount of solar radiation. Therefore, the remote control device 8r can acquire the amount of solar radiation at any time and change the setting of the draw-in current value Ipv according to the amount of power generated estimated from the amount of solar radiation. For example, the amount of solar radiation can be divided into high, medium, and low levels, and the aforementioned values can be set to 14 A for the high level, 10 A for the medium level, and 5 A for the low level.

The amount of power generated by solar power generation can also be estimated from information (history) on the amount of power generated in the past. For example, if output information can be acquired from the power conversion device 3 or the power meter for power sale 5, the remote control device 8r stores information on the amount of power generated in the past. The remote control device 8r then estimates the amount of power generated from the date based on the information on the amount of power generated in the past, and sets the draw current value (Ipv) appropriate for the amount of power generated.

Figure 11 is a schematic diagram showing the setting of the draw-in current value using a mobile information terminal (e.g., a smartphone) 300. The remote control device 8r of the power storage system 8 can communicate with the mobile information terminal 300 via the router 10 (Figure 1). The screen of a dedicated app installed on the mobile information terminal 300 displays information including the current power generation amount, the draw-in current value, and the load current value. When the user determines that the setting of the draw-in current value needs to be changed while looking at the screen displaying this information, the user can change the setting value from the mobile information terminal 300. In addition, if the draw-in current value exceeds the power generation equivalent value (current value equivalent to the power generation amount = generated power / voltage) estimated from the weather, the amount of solar radiation, etc., a signal can be displayed from the remote control device 8r to the mobile information terminal 300 to prompt the mobile information terminal 300 to change the setting.

Summary of disclosure
The above disclosure can be generalized and expressed as follows.

In the energy storage system 8 of the present disclosure, the control unit 87 receives the setting of the incoming current value (Ipv) as a predicted value received from the power conversion device 3 of the solar power generation device, and controls the power conversion unit 84 so that the peak value (Ibat_peak) of the charging current command value (Ibat) sent from the AC circuit 88 to the power conversion unit 84 does not exceed a current value obtained by subtracting the peak value (Iout_peak) of the load current (Iout) supplied to the load from a value √2 times the incoming current value.

In such a storage system 8, while receiving an independent output from the external power conversion device 3 and supplying power to the specific load 11, the difference between the value multiplied by √2 of the set draw current value (Ipv, fixed value) and the peak value (Iout_peak) of the load current (Iout) becomes the peak value (Ibat_peak) of the charging current command value (Ibat, AC) for charging the storage battery 85. Therefore, the storage system 8 can perform appropriate control based on the draw current value (Ipv) set by itself without linking with the external power conversion device 3, under the draw current value. Furthermore, even in the case of a nonlinear load, control can be performed to suppress the stop of the power conversion device 3.

However, if the peak value (Iout_peak) of the load current (Iout) is greater than √2 times the value of the draw current (Ipv), the control unit 87 stops the operation of the power conversion unit 84. In this case, theoretically, the current value obtained by subtracting the peak value (Iout_peak) of the load current (Iout) from √2 times the value of the draw current (Ipv) is negative, but in reality, a current (power) equal to or greater than the set draw current (Ipv) is being provided to the specific load 11 by photovoltaic power generation, so it is appropriate not to charge or discharge the storage battery 85.

The setting of the pull-in current value (Ipv) can be manually set as desired using the remote control device 8r. The user can select the pull-in current value (Ipv) from multiple candidate values displayed on the remote control device 8r. In this case, the user can select and set the pull-in current value from the candidate values that serve as a guideline.

The incoming current value (Ipv) can also be set (automatically set) based on other information, for example, as follows.
(a) The remote control device 8r sets the incoming current value (Ipv) based on information acquired from the weather information server 100 via the Internet.
(b) The remote control device 8r sets the draw current value (Ipv) based on the amount of solar radiation obtained from the actinometer 200.
(c) The remote control device 8r sets the draw current value (Ipv) based on information on the amount of power generated in the past.

It is also possible for communication to occur between mobile information terminal 300 and remote control device 8r.
The remote control device 8r accepts the setting of the draw current value (Ipv) from the mobile information terminal 300, and may also send information to the mobile information terminal 300 prompting the mobile information terminal 300 to change the setting if the set draw current value (Ipv) is greater than the value equivalent to the amount of power generated by solar power generation.

If distortion of a predetermined value or more occurs in the independent output from the solar power generation power conversion device 3, it is preferable for the control unit 87 to stop the operation of the power conversion unit 84. From the viewpoint of effective use of generated power, it should be avoided that the independent operation of the power conversion device 3 is stopped due to the occurrence of distortion.

《Addendum》
The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, and it is intended to include all modifications within the scope and meaning equivalent to the claims.

Reference Signs List 1 Consumer 2 Photovoltaic power generation panel 3 Power conversion device 4 General load distribution board 5 Power selling watt-hour meter 6 Power purchasing watt-hour meter 7 Commercial power system 8 Energy storage system 8 _in input terminal 8 _out output terminal 8r Remote control device 9 Specific load distribution board 10 Router 11 Specific load 80 Voltage sensor 81 Switch 82, 83 Current sensor 84 Power conversion unit 85 Storage battery 86 BMS
87 Control unit 88 AC circuit 88j Branch point 100 Weather information server 200 Pyranometer 300 Mobile information terminal

Claims (12)

A power storage system provided between a power conversion device that provides independent output by photovoltaic power generation and a load,
an AC circuit extending from an input terminal for receiving the independent output to an output terminal to which the load is connected;
a power conversion unit that is disposed between the AC circuit and the storage battery and performs bidirectional power conversion between DC and AC;
A control unit that controls the power conversion unit,
The control unit is
Accepting a setting of a sink current value as a predicted value to be received from the power conversion device;
A peak value of a load current supplied to the load is calculated as an absolute value;
Controlling the power conversion unit so that a peak value of a current sent from the AC circuit to the power conversion unit does not exceed a current value obtained by subtracting the peak value of the load current from a value that is √2 times the incoming current value.
Energy storage system. The energy storage system of claim 1, wherein the control unit stops operation of the power conversion unit when the peak value of the load current is greater than √2 times the value of the draw current. a remote control device electrically connected to the control unit and having an operation reception function;
The power storage system according to claim 1 or 2, wherein the draw current value is set for the control unit by the remote control device. The energy storage system according to claim 3, wherein the draw current value is a value selected by the user from a plurality of candidate values displayed on the remote control device. The power storage system according to any one of claims 1 to 4, wherein when distortion of a predetermined value or more occurs in the independent output from the power conversion device, the control unit stops the operation of the power conversion unit and sets up a bypass state in which the input terminal is directly connected to the output terminal. The power storage system of claim 5, wherein when the distortion becomes less than the predetermined value, the control unit operates the power conversion unit to charge the storage battery. The power storage system according to claim 5, wherein the control unit continues the bypass state if the storage battery is fully charged even when the distortion falls below the predetermined value. The remote control device is connected to a server that stores weather information via an electric communication line,
The power storage system according to claim 3 , wherein the remote control device sets the draw current value based on the information acquired from the server. Equipped with a pyranometer to detect the amount of solar radiation,
The power storage system according to claim 3 , wherein the remote control device sets the draw current value based on the amount of solar radiation acquired from the actinometer. the remote control device acquires information on past power generation amount from the power conversion device for solar power generation,
The power storage system according to claim 3 , wherein the remote control device sets the draw current value based on the information. a mobile information terminal capable of communicating with the remote control device,
4. The power storage system according to claim 3, wherein the remote control device accepts a setting of the draw current value from the mobile information terminal, and sends information to the mobile information terminal prompting the mobile information terminal to change the setting if the set draw current value is greater than a value equivalent to a power generation amount of solar power generation. A method for controlling a power storage system in a case where the power storage system is provided between a power conversion device that provides an independent output by photovoltaic power generation and a load, comprising the steps of:
A current draw value is set as a predicted value to be received from the power conversion device;
A peak value of a load current supplied to the load is calculated as an absolute value;
Controlling the power conversion unit so that a peak value of a current fed to the power conversion unit for charging the storage battery does not exceed a current value obtained by subtracting the peak value of the load current from a value that is √2 times the value of the incoming current.
A method for controlling an energy storage system.

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