JP5175451B2 - Power supply system - Google Patents

Description

  The present invention relates to a power supply system including a DC power source whose power generation amount varies greatly depending on the environment, such as a solar cell, a wind power generator, and a fuel cell, and more particularly to a system that supplies power efficiently even at low output.

A power converter that uses natural energy such as a solar battery, a wind power generator, or a fuel cell uses an electric power conversion unit to connect to an electrical load or system power. However, it is known that the power conversion unit generally has a low conversion efficiency at low output.
Therefore, as shown in FIG. 10, the conventional solar cell device is connected so that the outputs of the plurality of solar cells 31 a, 31 b, and 31 c are combined into one connection box 32. Thereafter, the load is connected to the load 34 or the system power 35 via a plurality of inverters 33a, 33b, 33c connected in parallel, and the operation of the inverters 33a, 33b, 33c is controlled by the control unit 36.
Thus, the system which controls an inverter is used by the large-scale solar cell system which has the electric power generation amount of a household solar cell system and several tens kW-several MW class, for example.
For example, Patent Document 1 discloses a system as shown in FIG. 10 as a technique for connecting a plurality of low-power inverters in parallel and reducing the number of inverters operated when the amount of power generated by a solar cell is small. Patent Document 2 discloses an inverter to be operated as a predetermined law, for example, as a technique of selecting each inverter in the order of decreasing output power amount, in order of decreasing operation time, or randomly.
JP-A-6-165513 JP 2000-305633 A

  However, since Patent Documents 1 and 2 reduce the number of inverters operated when the amount of power generated by the solar cells is small, and select the inverters in order of decreasing output power amount or in order of decreasing operation time or randomly, It is necessary to detect this and control it in a complicated manner based on the detection output. This complicates the configuration and control of the control unit. In addition, this control device requires measures when the amount of power generated by the solar cell suddenly increases, and requires advanced control. In addition, since the inverter is switched in accordance with fluctuations in the amount of power generated by the solar cell, the number of switching operations increases in a solar cell in which the amount of generated power frequently fluctuates frequently, and a highly reliable switching circuit is required. Furthermore, since the output fluctuates according to the amount of power generated by the solar cell, the load and the grid power are forced to operate unstablely. The maximum output of this system is determined by the amount of power generated by the solar cell, and the maximum power cannot be controlled.

  In view of the above-described problems, the present invention provides a power supply system that does not require complicated control of a power conversion unit. It is another object of the present invention to provide a power supply system capable of time-shifting the output power amount of a DC power source. Furthermore, the present invention provides a power supply system that can control the maximum power.

In order to solve the above problems, the power supply system of the present invention is a power supply system in which a plurality of power strings including a DC power source and a power conversion unit that converts DC power from the DC power source are connected in parallel. A control unit that controls the power conversion unit according to an output power amount of a power source and a power storage unit connected to at least one of the DC power sources.
Here, the direct current power source refers to one that obtains direct current power from a power generation device such as a solar cell, a wind power generation device, or a fuel cell. The power converter is a so-called inverter that converts direct current to alternating current, and can be used in any form, such as a system that uses a high-frequency insulation transformer or a system that uses PWM control and is insulated by a commercial frequency transformer. Each of which may be of the same type or different. The power storage unit stores DC power output from a DC power source, typically a storage battery, and besides that, like a hydrogen storage system of a type that stores power by changing it to hydrogen, Any device that can store and take out power can be used.

  As described above, the present invention includes the power storage unit connected to at least one of the DC power sources, so that it is possible to absorb sudden fluctuations and stabilize the output, and the power conversion unit is sophisticated and complicated. Control can be eliminated, and therefore the number of operations of the changeover switch can be reduced. In addition, by storing the power output from the DC power supply in the power storage unit, the power from the DC power supply is output at a time different from the output time, so-called time shift can be supplied to the load or the system. . Further, by extracting the maximum power stored in the power storage unit, it is possible to control the maximum output power amount according to the maximum output power output from the power supply system or the maximum power amount required by the load or the system.

In the power supply system of the present invention, the DC power supply may be a device that outputs DC power from a power generation device such as a solar cell, a wind power generation device, or a fuel cell, or a combination thereof. As a result, various power sources can be used as the DC power source, and any combination thereof can be used.
In the power supply system of the present invention, it is preferable that each of the DC power sources includes the power storage unit. When the power storage unit is provided in this way, fluctuations in the amount of output power from the DC power supply can be reduced and stabilized, and as a result, sophisticated and complicated control of the power conversion unit can be eliminated. Further, since a larger amount of power can be stored in the power storage unit, the amount of time-shifted power can be increased, and the maximum output power amount can be increased.
In the present invention, the control unit controls on / off of the power conversion unit to determine an output of the power supply system. In this case, the control unit can detect the power amount of each power string and determine the output value of the power supply system of the present invention as the total value thereof. Or it becomes possible to output the electric power value requested | required from load or a system | strain.
As described above, according to the present invention, it is possible to output the output of a direct current power source such as a solar power generation device, a wind power generation device, or a fuel cell, and the total power stored in the power storage unit.

Moreover, in this invention, a control part starts arbitrary power conversion parts according to the determined output value. Thus, since an arbitrary power converter is started according to the output value which the control part determined, a power converter can be operated with high conversion efficiency.
The power supply system of the present invention further includes a detection unit that detects an output power amount of the DC power supply, and the control unit controls the power conversion unit according to the output power amount detected by the detection unit. desirable. Thereby, the electric power generated by the DC power source can be used effectively.
The power supply system according to the present invention preferably further includes a detection unit that detects a storage amount of the power storage unit, and the control unit controls the power conversion unit according to the storage amount detected by the detection unit. Thereby, the electric power stored in the power storage unit can be used effectively.

The power supply system according to the present invention preferably further includes a detection unit that detects an output power amount of the power supply system, and the control unit controls the power conversion unit according to the amount of power detected by the detection unit. . Thereby, the amount of stored electricity can be controlled according to the output power amount of the power supply system of the present invention.
In the power supply system of the present invention, the control unit may periodically and sequentially start the power conversion units. By starting in this way, each power converter can be operated uniformly.

  According to the present invention, complicated control of the power supply system can be eliminated, and therefore the number of operations of the switching circuit can be reduced. In addition, the power generated by the DC power supply can be supplied while being time-shifted. Furthermore, the maximum output power amount can be controlled by taking out the maximum power stored in the power storage unit.

《Power supply system configuration》
As shown in FIG. 1, the power supply system of the present invention has a plurality of DC power supplies 1a, 1b, 1c and power converters 2a, 2b, 2c for converting DC power from the DC power supplies 1a, 1b, 1c. Are connected in parallel. Furthermore, the control part 3 which controls electric power conversion part 2a, 2b, 2c according to the output electric energy of the said DC power supply, and the electrical storage part 4a, 4b or 4c connected to the said DC power supply 1a, 1b, 1c are provided. The outputs of the power conversion units 2a, 2b, and 2c are combined into one and connected to the commercial power 7 that is the system power via the load 5 or the switch 6.

The DC power source 1 is for obtaining DC generated power from a power generator such as a solar battery, a wind power generator or a fuel cell. In the case of a large-scale DC power supply, the specifications and performance of each DC power supply are naturally different. For example, in a solar battery or a wind power generator, the output power value differs depending on the installation location, direction, and inclination. FIG. 1 shows three DC power supplies 1a, 1b, 1c, and three power converters 2a, 2b, 2c, but this number is arbitrary and may be two or more. Each DC power source 1 and each power conversion unit 2 may be the same, have the same performance, or may be different from each other. The direct current power source may be any different combination such as a solar cell, a wind power generator, or a fuel cell. Further, the power storage units 4a, 4b, or 4c are not necessarily provided in the DC power supplies 1a, 1b, and 1c, respectively, and may be at least one or more.
The power converters 2a, 2b, and 2c are so-called inverters that convert direct current into alternating current. The power conversion unit can be used in any form, such as a system that uses a high-frequency isolation transformer, a system that uses PWM control to insulate with a commercial frequency transformer, and each may be the same or different. .

In addition to controlling according to the output power amount of the DC power source 1, the control unit 3 can be controlled by the power storage amount of the power storage unit 4, the output of the power supply system, or the output value determined by the control unit itself. is there.
The power supply system shown in FIG. 1 includes a control unit 3, and the control unit 3 controls the power conversion unit 2, but does not include the control unit 3, and any one of the power conversion units 2a to 2c. It is also possible to adopt a scheme in which one or all of the power conversion units mutually control other power conversion units. The case of this method is indicated by a connection line 8 in FIG. 1 and can be operated in the same manner as the case where the control unit 3 is provided.
The power storage unit 4 stores DC power output from the DC power source 1, and typically uses a storage battery. In addition, it may be a hydrogen storage system in which water is electrolyzed by the output from the DC power source 1, the generated hydrogen is stored, and hydrogen is burned as necessary to obtain electric power. The power storage unit 4 may be provided in at least one of the DC power sources 1, and more preferably provided in each DC power source 1.

  Further, an embodiment in which the power supply system of the present invention uses a solar cell as a DC power source will be described with reference to the block diagram of FIG. FIG. 2 shows an embodiment of the present invention, and the present invention is not limited by this FIG.

As shown in FIG. 2, the solar cell module 11 is a thin film-microcrystalline solar cell panel having a maximum power voltage Vpm = 51 V, a maximum short-circuit current Isc = 2 A, and an output of 85 W. The solar cell array 10 has a 12-sheet configuration in which the solar cell modules 11 are connected in 4 series and 3 parallel. Therefore, the maximum output is 1020W. FIG. 2 shows three solar cell arrays 10.
The storage battery module 12 is composed of 48 5.7 Ah lithium ion batteries in series, and includes a circuit unit having a protection circuit and a power counter.

  In this embodiment, the amount of power generated by the three solar cell arrays 10 and the storage capacities of the three storage battery modules 12 will be described as being the same, but they are not necessarily the same and may be different. Good. Further, since the amount of light received by the solar cell array varies depending on the installation location, the power generation amount may be different.

The protection circuit provided in the storage battery module 12 includes a known voltage monitoring IC, FET, control CPU, or the like. For example, when a voltage abnormality is detected, the circuit is opened to protect the storage battery. It is what has. That is, it includes an overcharge prevention circuit, an overdischarge prevention circuit, an overcurrent prevention circuit, a voltage monitoring circuit for each cell of storage battery devices connected in series, a balance circuit for adjusting the voltage of each cell, and the like.
The power counter uses a power monitoring IC, has a function of monitoring the charge / discharge power of the storage battery, and outputting the charge state of the storage battery to the outside.

The solar cell array 10 having the above configuration is connected in parallel to the storage battery module 12 via a backflow prevention element 13 formed of a diode provided so that the power of the storage battery module 12 does not flow back to the solar cell module 11.
A connection point 14 for connecting the solar cell array 10 and the storage battery module 12 in parallel, and a switch 15 is connected between the storage battery module 12, and the connection point 14 is further subjected to DC / AC conversion via a current sensor 16 and a backflow prevention diode 17. Connected to device 20.
The connection line 18 is an earth line that connects the solar cell array 10 and the storage battery module 12 to the DC / AC converter 20.

Here, a field effect transistor (MOS TFT) is used as the switch 15. The switch 15 controls the storage battery module 12 to be connected to the solar cell array 10 or opened from the solar cell array 10 by a control circuit (not shown). Details of the switch 15 will be described later.
The current sensor 16 may be, for example, one connected with a shunt resistor and measuring the voltage at both ends, or one using a hall sensor or the like.

In this way, a plurality of power strings in which the solar cell array 10 is connected to the DC / AC converter 20 are joined in parallel and connected to the load 30. Alternatively, the power is linked with the grid power 50 via the switch 40 so as to allow reverse power flow (outputting power generated by a distributed power source such as a solar cell toward the grid).
An ammeter 21 and a voltmeter 22 are provided in the output unit in order to detect the voltage and current combined with the plurality of DC / AC conversion devices 20, and the detection result is supplied to the output management device 60.
Signals such as the voltage value, the amount of charge and the SOC (State of Charge) of the storage battery module 12 are supplied to the DC / AC converter 20 via the signal line 19 and the output of the DC / AC converter 20 is determined. Use to do. The signal is supplied to the output management unit 60 and used as a control signal for the DC / AC converter 20.
The signal line 23 that connects the signal line 19 and the output management unit 60 supplies a signal such as a voltage value, a storage amount, and SOC to the output management unit 60, and the output management unit 60 performs DC / AC conversion as described later. It is used as a connection line for supplying a signal for instructing 20 operation / stop.

In the configuration as described above, the solar cell array 10 is installed in a sunny place such as a normal roof or a rooftop. On the other hand, the storage battery module 12 and the DC / AC conversion device 20 are stored in a building installed under the solar cell base or near the solar cell array 10. Therefore, since the distance between the solar cell array 10 and the storage battery module 12 or the DC / AC converter 20 is long, a design in consideration of wiring resistance is required.
In the above configuration, it is desirable that the solar cell module 11 is an element that has excellent temperature characteristics and can be set in an appropriate voltage range, such as a thin film solar cell. An amorphous silicon solar cell or a tandem solar cell in which crystalline silicon and amorphous silicon are stacked can also be used.

The storage battery module 12 is preferably a battery having no cycle deterioration due to insufficient charging and no memory effect. As such a battery device, a lithium ion battery is suitable, and the lithium ion battery can be set to a narrow voltage range by making the voltage range correspond to a solar cell, and the charge / discharge curve is flat, There is no cycle deterioration or memory effect in charging, which is preferable.
The voltage range of the storage battery module 12 can extract 60% to 100% of power at a predetermined solar radiation amount and temperature with respect to the maximum power voltage point (Vpmax) when the solar cell has a predetermined solar radiation amount and temperature. Set to the correct voltage range. Thereby, a voltage range can be narrowed and the output of a solar cell can be smoothed.
In an ordinary solar cell system, the operating point is controlled by the maximum power point tracking method that changes according to the solar radiation conditions and the temperature of the solar cell element. In this invention, the voltage of the storage battery module 12 is the operating point of the solar cell array 10. Operate to become voltage. Thereby, the operating point voltage of the solar cell array 10 can be limited to the voltage range in which the storage battery module 12 operates.

  As shown in FIG. 3, the operating voltage range of the storage battery module 12 is set to a range of SOC 20% to SOC 80% in the PV curve A of the solar cell array 10. SOC indicates the state of charge of the power storage unit, where SOC 100% indicates full charge and SOC 0% indicates completion of discharge. It can be seen that the ratio of the SOC to the maximum power point voltage (Pmax) in the range of 20% to SOC 80% is 92% to 100% from the right scale of FIG. 3 and the efficiency curve B.

In general, when the temperature of the solar cell module 11 rises, the output tends to decrease, and the temperature coefficient representing the inclination is negative. For example, the temperature coefficient of crystalline silicon is −0.45 to 0.5% / ° C.
On the other hand, since the operating voltage of the storage battery module 12 is hardly affected by the temperature, it is desirable to select a solar battery having excellent temperature characteristics for the solar battery module 11 used in the present invention. For example, the temperature coefficient is preferably −0.42% / ° C. or lower, more preferably −0.3% / ° C. or lower. As described above, a thin film solar cell having a temperature coefficient of −0.17 to −0.2% ° C. is suitable as a solar cell having a small temperature coefficient, and high system efficiency is obtained when the thin film solar cell is used. be able to.

<Setting the voltage range>
In this invention, the voltage range which charges / discharges the storage battery module 12 can be shown like FIG. FIG. 4 shows the relationship between the charge capacity and the charge / discharge voltage. The battery is charged as shown by the charge curve C and discharged as shown by the discharge curve D. Although this voltage range can be set arbitrarily, in the present invention, it is in the range of SOC 20% to SOC 80%. Therefore, the charge end voltage is a SOC 80% voltage, and the discharge end voltage is a SOC 20% voltage. is there. After all, the battery usage area is 60% of the center of the SOC.
Lithium ion batteries deteriorate even if they are not used when left in a fully charged state. Therefore, when using lithium ion batteries as power storage devices, it is important to use the power at the center of the battery. It is preferable in terms of characteristics.

The said voltage is realizable by selecting suitably the kind and number of series of the solar cell module 11, the kind and number of series of the storage battery module 12, and the charge condition to be used. The voltage range may be fixed, or the set value may be changed sequentially depending on the amount of solar radiation, the climatic conditions, the deterioration status of the storage battery device, or the like.
When the voltage is changed depending on solar radiation conditions or climatic conditions, the voltage range may be set by dividing into appropriate periods based on past solar radiation data and temperature data.
For example, since the temperature of the solar cell module is low in winter when the temperature is low, the voltage range is set high. In summer when the temperature is high, the voltage range is set low. In spring and autumn, the voltage range is set between winter and summer. Thus, when setting in consideration of solar radiation conditions, the lower limit value can be set to 80% or more in an area where solar radiation is stable.
Moreover, since the internal resistance of the storage battery module 12 increases as the deterioration progresses, it can be set in advance so that the end-of-charge voltage is gradually increased within the above range and decreased at the end-of-discharge voltage. It is. For this purpose, it is preferable to provide a switch so that the set value set in the control software can be updated using communication means or the like.

<Charging control method>
In the present invention, by controlling the output from the DC / AC conversion device 20, it is possible to smooth the output from the DC / AC conversion device 20 and to control the charging of the storage battery module 12. That is, charging power is obtained by subtracting the output of the DC / AC converter 20 from the amount of power generated by the solar cell array 10. By controlling the output in this way, the power generation output of the solar cell array 10 can be smoothed and the charge control can be performed.
The output control of the DC / AC converter 20 may be a constant output to absorb the output fluctuation from the solar cell array 10, or the output of the DC / AC converter 20 so that the charging current is constant. It is possible to control.

A control method when emphasizing output smoothing will be described with reference to FIG. This figure shows the relationship between the generated power E of the solar cell array from 16:00 to 17:00 on one day, the output F of the DC / AC converter, the charging power G to the storage battery module, and the SOC (charging state) H. Is.
As the evening approaches, the amount of solar radiation decreases and the generated power E gradually decreases. However, since the output F from the DC / AC converter is controlled to be constant, the amount of solar radiation decreases. Despite this, it is possible to obtain a constant output. At the same time, the charging power G to the storage battery module can be gradually lowered, and two controls can be achieved simultaneously.
When such control is used at the end of charging of the storage battery module, the same effect as the constant current / constant voltage charging often used in the charging control of the storage battery module is obtained, which is very effective. Normally, when the battery is almost fully charged by the charge control device, control is performed to reduce the charging power. However, in the solar power generation system of the present invention, control is performed to reduce the charging power near the full charge. The charging control can be achieved simultaneously only by the output control of the DC / AC converter.

Next, the case of controlling the charging current will be described with reference to FIG. This figure shows the relationship between the generated power I of the solar cell array 10 from 10:00 to 11:00 on a certain day, the output J of the DC / AC converter, and the charging power K to the storage battery module.
Although the generated electric power I of the solar cell array 10 changes steeply as the amount of solar radiation changes, the present invention is not a control that follows at any time. The output J from the conversion device can be smoothed. Further, the charging power K is controlled at the same time so that the charging power K is always equal to or lower than a certain level, although it varies. In battery control, controlling not to charge more than the rated charge power is important for extending the life of the battery. Normally, such control is performed by a dedicated charger. In the invention, the output from the DC / AC converter can be smoothed, and at the same time, the control of the charging power can be achieved.

<Balance of capacity>
When the output of the solar cell array is P1 (W) and the storage capacity W1 (Wh) of the storage battery module, the balance is preferably P1 × 1 hour <W1. If the storage battery capacity is at this level, the output can be leveled at fine time intervals.
In normal storage battery charging control, a current limit is provided so that a large current does not flow into the storage battery. However, in the solar cell module, the maximum current that can be passed to the device is determined by the internal resistance and wiring resistance of the solar cell module, and the balance between the output of the solar cell array and the storage capacity of the storage battery module is adjusted. This eliminates the need for a current limiting circuit during charging, which is normally required.

Therefore, this capacity balance is very important. From such a viewpoint, the minimum value of the charging current is preferably the above lower limit value, more preferably P1 × 0.5 hours, and further preferably P1 × 0.3 hours. Since a normal storage battery device allows a charging current of about 1 C (current that charges the storage battery capacity in 1 hour), if the minimum value is P1 × 1 hour, the options for the storage battery device can be considerably expanded, which is preferable. .
Even if the maximum capacity value of the storage battery module 12 is large, there is no problem in carrying out the present invention. However, from the viewpoint of equipment size, cost, equipment availability, etc., P1 × 10 hours, more preferably P1 × 5 hours. It is preferable to set the degree. Sufficient power storage capacity is preferable because it is possible to achieve both smoothing of output at fine time intervals and power shift (leveling) at a large time for time shifting power.

<Description of switch switching operation>
In the present invention, the voltage of the storage battery module 12 connected to the solar cell string is detected and the switch 15 is connected or opened, so that the solar cell array 10 is disconnected for a while after full charge, for example. Only the generated power is utilized by the maximum power point tracking method. After that, when the generated power of the solar battery decreases, the storage battery module 12 is connected again, and the combined power of the solar battery array 10 and the storage battery module 12 can be utilized.
Further, the present invention detects the current from the solar cell array 10 and switches the switch 15. Therefore, for example, when the solar cell strings are connected in parallel as shown in FIG. 2 and constant power control is performed, the solar radiation amount of some solar cell arrays is reduced or shaded, When the output of the solar cell array decreases, it becomes possible to avoid the concentration of output requests only on a certain solar cell array when power generation becomes impossible due to a failure.

Since the solar cell string of the present invention has a storage battery module, it can supply only the required power without solar radiation. However, when a certain amount of stored electricity is consumed, the output is supplied only to the solar cell array 10. If switched, the electric power from the solar cell array 10 is finite. Therefore, when the electric power is required to exceed the capacity, the voltage decreases, and the output from the storage battery modules 12 in the other solar cell strings is promoted.
If the switch 15 opens the solar cell array 10 and the storage battery module 12 by sending a signal from the outside through normal communication means, it is possible to operate the solar cell array 10 with maximum power point tracking. It becomes.

<Operation algorithm>
The power supply system of the present invention shown in FIG. 1 or 2 operates according to the following operation algorithm.
The power supply system of the present invention derives the output power according to a predetermined algorithm (a function using the variable) with the instantaneous solar radiation intensity as an input variable. As shown in Table 1 of FIG. 7, this algorithm controls the number of units corresponding to the solar radiation intensity. This algorithm is a mechanism in which the required output power value stored in the storage unit 61 in the output management device 60 and calculated by the output management device 60 is transmitted to each DC / AC inverter 20 in the form of an electrical signal.

In Table 1 shown in FIG. 7, “unit control 1” shown as an instruction pattern means an instruction to operate only one DC / AC inverter when the solar radiation intensity is 0 to 0.3 kW / m ² . . At this time, the required output to the DC / AC inverter 20 instructed for operation is the solar radiation intensity × the power generated by one solar cell array × 3.
“Number control 2” is an instruction to operate two DC / AC inverters when the solar radiation intensity is 0.3 to 0.6 kW / m ² . At this time, the required output to the DC / AC inverter 20 instructed for operation is the solar radiation intensity × the power generated by one solar cell array × 1.5.
The “total number operation” is an instruction to operate all the DC / AC inverters 20 provided in each solar cell array 10 when the solar radiation intensity is 0.6 to 1.0 kW / m ² . At this time, the required output to each DC / AC inverter 20 instructed for operation is the solar radiation intensity × the generated power of one solar cell array × 1.

“Unit control” will be explained using specific examples.
If the current sensor 16 obtains a detection output equivalent to about 1.0 kW / m ² (intensity of sunlight on a fine day in Japan) which is incident on each solar cell array 10, output management The device 60 selects “all operations” as an instruction pattern in accordance with the algorithm shown in Table 1 shown in FIG. 7, and issues start-up and operation instructions to all DC / AC inverters 20a, 20b, and 20c. Since each solar cell array 10 exhibits the maximum power generation capacity, the storage battery module 12 is charged, and at the same time, the maximum power is reversely flowed to the system 30 via the DC / AC inverters 20a, 20b, and 20c. Alternatively, power is supplied to the load 40.

In this description, the solar radiation intensity is detected by the current sensor 16, but it may be detected by an ammeter 21 and a voltmeter 22 provided where a plurality of DC / AC converters 20 are joined. The following description is also the same.
The above operation is continued while the solar radiation intensity continues. That is, each solar cell array 10 exhibits the maximum power generation capacity, charges the storage battery module 12, and simultaneously reverses the maximum power to the system 30 via the DC / AC inverters 20a, 20b, and 20c. Alternatively, power is supplied to the load 40.

Next, when it is detected from the detection output of the current sensor 16 that the solar radiation intensity is 0.1 kW / m ² , the output management device 60 reads “number control 1” from the algorithm of FIG. Here, the output management device 60 reads out the voltage value detected by the voltage detection unit provided in each storage battery module 12 via the signal lines 19 and 23, compares it, and compares all the storage battery modules 12a, 12b, The storage battery module which shows the largest voltage value in 12c is selected.
For example, it is assumed that the storage battery module 12a is selected. Then, the DC / AC inverter 20a connected to the storage battery module 12a is activated to instruct a DC / AC conversion operation. The other DC / AC inverters 20b and 20c are instructed to stop. (See t1 to t2 in FIG. 8)

At this time, the required output power to the DC / AC inverter 20a is approximately three times the power generated by the solar cell array 10a. The calculation formula for the required output power is the solar radiation intensity (kW / m ² ) × the generated power of one solar cell array × 3. Therefore, in this case, 0.1 × 1.02 × 3 = 0.306 kW.
In this case, since the required output power is naturally insufficient only by the amount of power generated by the solar cell array 10a, the insufficient power amount is brought out from the storage battery module 12a. As a result, the DC / AC inverter 20a operates at high output and operates with high conversion efficiency.
During this time, the DC / AC inverters 20b and 20c stop operating, and the storage battery modules 12b and 12c are charged by the outputs of the solar cell arrays 10b and 10c. The charging current at this time is charged with a small charging current.

After 5 minutes, when the solar radiation intensity does not vary greatly and is within the range of 0 to 0.3 kW / m ² , the output management device 60 sets the largest voltage value among all the storage battery modules 12a, 12b, and 12c. Select the storage battery module shown. That is, since the storage battery module 12a is selected and the amount of stored electricity is consumed in the previous 5 minutes, the storage battery module 12a is searched for a storage battery module having a voltage value larger than that of the storage battery module 12a.
In this case, if the storage battery module 12b shows a larger voltage value, a start-up / operation instruction is issued to the DC / AC inverter 20b connected to the storage battery module 12b. Then, a stop instruction signal is output to the DC / AC inverter 20a. A stop instruction signal is continuously output to the DC / AC inverter 20c. (See t2 to t3 in FIG. 8)

Thus, when switching the operation from the DC / AC inverter 20a to the DC / AC inverter 20b, the DC / AC inverter 20a instructed to stop gradually decreases the voltage, while the DC / AC inverter 20b gradually increases the voltage. By doing so, seamless switching can be realized.
Therefore, this time, the same required output power is output to the DC / AC inverter 20b, and the generated power of the solar cell array 10b and the discharged power from the storage battery module 12b are output to the grid 30 via the DC / AC inverter 20b. The

Furthermore, when the solar radiation intensity increases to 0.5 kW / m2 three minutes later, it is detected by the detection output of the current sensor 16, and the output management device 60 immediately determines “number control 2”, and all storage batteries Two storage battery modules showing the largest voltage value and the next voltage value among the modules 12a, 12b, and 12c are selected. Then, a startup / operation instruction is issued to the inverter connected to the two storage battery modules. In this case, it is assumed that the DC / AC inverters 20a and 20c are selected and an activation / operation instruction is issued. A stop instruction is issued to the DC / AC inverter 12b. (See t3 to t4 in FIG. 8)
The required output power to each inverter at this time is 0.5 × 1.02 × 1.5 = 0.765 kW, which is 1.53 kW in total.

  By operating the power supply system as described above, the number of inverters to be operated can be minimized when the solar radiation intensity decreases and the power generation amount of the solar cell array decreases. This is an advantage in that the energy for maintaining the operation of the inverter can be reduced compared to the conventional operation method in which all inverters are operated even in low solar radiation.

<Generalized operation algorithm>
The operation algorithm of the present invention described above can be generalized as follows.
First, it is assumed that the preconditions are as follows.
-Number of solar cell arrays (= number of inverters): n
・ Insolation intensity: Less than 1 / n (kW / m ² )

Under this condition, the operation algorithm is generalized as follows.
a) Of the n inverters, only the inverter x connected to the storage battery module having the largest voltage value is started and operated, and the other (n−1) inverters are stopped.
b) The required output power to the activated inverter x is n times the amount of power generated by one solar cell array depending on the solar radiation intensity. (That is, (n-1) times as much power is taken out of the storage battery module connected to the solar cell array.
c) The output management device re-determines the inverter to be operated at regular intervals. That is, after the inverter x has been operated for a certain time, the storage amounts of all the storage battery modules are compared again, and the inverter y connected to the storage battery module showing the highest voltage value starts to start up and operate. Instructs inverter x to stop operation.
d) When switching the inverter, the output power of the inverter x decreases with a constant slope over several seconds so that the output power does not break, and the output power from the inverter y remains the same over the same time. Increase with slope.
e) If the solar radiation intensity changes beyond the threshold before a certain time elapses, the output management device immediately makes a re-judgment and issues an instruction to each inverter again.

The operation algorithm when the preconditions are as follows is as follows.
-Number of solar cell arrays (= number of inverters): n
Insolation intensity is 1 / n to ² / n (kW / m ² )

a) Always start and operate only the inverters x and y connected to the two storage battery modules having the highest voltage value and the next highest voltage value among the n inverters, and the other (n-2) units The inverter is stopped.
b) The required output power to the activated inverters x and y is n / 2 times the amount of power generated by one solar cell array depending on the solar radiation intensity. (That is, (n / 2-1) times as much power is taken out from the storage battery module connected to the solar cell array.
c) The output management device re-determines the inverter to be operated at regular intervals. That is, after the inverters x and y have been operated for a certain time, the voltage values of all the storage battery modules are compared again, and the inverters z and a connected to the two storage battery modules having the largest voltage value and the next voltage value are compared. Start-up / operation starts. The inverters x and y are stopped.
d) At the time of this switching, the output power of the inverters x and y decreases with a constant slope over several seconds so that the output power does not break, and the output power from the inverters z and a takes the same time. Increase at the same constant slope.
e) If the solar radiation intensity changes beyond the threshold before a certain time elapses, the output management device immediately makes a re-judgment and issues an instruction to each inverter again.

  In another embodiment of the present invention, each solar cell string is activated in turn, assuming that the output of the solar cell array and the power stored in the storage battery module are substantially equal. That is, as shown in FIG. 9, the DC / AC inverters 20a to 20c are sequentially activated at equal intervals. Thus, if the order and time interval are determined in advance, sensors and control are not required, and each DC / AC inverter can be controlled by a simple algorithm. Therefore, it is only necessary to eliminate the control unit 3 and determine the starting order between the DC / AC inverters.

As yet another embodiment, when the present invention is applied to a large-scale power supply system, the solar cell array has a large area, and thus the same output cannot be obtained from each solar cell array. For example, there are a solar cell array that generates a large amount of electricity in the morning and a solar cell array that generates a large amount of electricity in the evening depending on the installation location or direction and inclination of the solar cell array. In addition, it is necessary to use solar cell arrays having different areas. Therefore, the output power of each solar cell array and the amount of power stored in the storage battery module are different. Furthermore, when it is predicted that the next day will be cloudy or rainy, each power supply system may be controlled according to the prediction.
That is, for a solar cell string including a solar cell array that generates a large amount of electricity in the morning, it is preferable to control so that a large amount of electric power is stored in the morning and discharged in the evening. Conversely, for a solar cell string including a solar cell array that generates a large amount of electricity in the evening, it is preferable to control so that a large amount of electric power is stored in the evening and discharged in the morning.
Similarly, if it is predicted that the next day will be cloudy or rainy, the discharge on that day will be reduced, and the next day will be discharged more.

The block diagram of an electric power supply system is shown. The block diagram of embodiment is shown. The PA characteristic view of a solar cell array is shown. The charge / discharge characteristic figure of a storage battery module is shown. A control method emphasizing output smoothing is shown. The figure explaining the control method which controls charging current is shown. The control algorithm of a power supply system is shown. The time chart figure explaining control of an electric power supply system is shown. The time chart figure explaining control of an electric power supply system is shown. The block diagram of the conventional power supply system is shown.

Explanation of symbols

1 DC power supply 2 Power conversion unit 3 Control unit 4 Power storage unit 5, 30 Load 7, 50 Commercial power (system)
DESCRIPTION OF SYMBOLS 10 Solar cell array 11 Solar cell module 12 Storage battery module 15 Switch 16 Current sensor 19 Signal line 20 DC / AC converter 21 Ammeter 22 Voltmeter 60 Output management device 61 Memory | storage part

Claims (5)

A power supply system in which a plurality of power strings including a DC power source and a power conversion unit that converts DC power from the DC power source into AC power are connected in parallel,
A control unit that controls the power conversion unit according to the output power amount of the DC power supply;
A power storage unit connected to each of the DC power sources,
When the number of the DC power sources is n and the output power amount of one of the DC power sources is less than 1 / n of the output power amount of the entire power supply system, the control unit a) of n DC power sources, The power conversion unit connected to the power storage unit with the highest voltage value is activated and operated, the other (n-1) power conversion units are deactivated, and b) the required output power amount of the activated power conversion unit Is n times the amount of power generated by one DC power source, and c) every time the power conversion unit is operated for a predetermined time, the amount of power stored in all the power storage units is compared and connected to the power storage unit showing the highest voltage value. A power supply system for starting up and starting the power conversion unit . A power supply system in which a plurality of power strings including a DC power source and a power conversion unit that converts DC power from the DC power source into AC power are connected in parallel,
A control unit that controls the power conversion unit according to the output power amount of the DC power supply;
  A power storage unit connected to each of the DC power supplies;
With
  When the number of the DC power sources is n and the output power amount of the one DC power source is 1 / n to 2 / n of the output power amount of the entire power supply system, the control unit a) n DC power sources Among them, the two power conversion units connected to the two power storage units having the highest voltage value and the next highest voltage value are activated and operated, and the other (n-2) power conversion units operate. B) The required output power amount to the two activated power conversion units is n / 2 times the power generation amount generated by one DC power supply, and c) every time the two power conversion units are operated for a predetermined time. The power storage amounts of all the power storage units are compared, and the two power conversion units connected to the power storage unit having the highest voltage value and the next highest voltage value are started and started.
A power supply system characterized by that. The control unit further d) when switching the power conversion unit, the output power of the power conversion unit to stop operation is decreased over a predetermined time, and the output power from the power conversion unit to start activation has the same predetermined time. The power supply system according to claim 1, wherein the power supply system is increased over time. The control unit further performs e) if the output power amount of the power conversion unit has changed beyond the threshold before the predetermined time operation, immediately performs a re-determination, and issues an instruction to each power conversion unit again. The power supply system according to any one of claims 1 to 3, wherein the power supply system is characterized in that: 5. The DC power supply according to any one of claims 1 to 4 , wherein the DC power source is a device that outputs DC power from a power generation device such as a solar cell, a wind power generation device, or a fuel cell, or a combination thereof. The power supply system described.

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