JPWO2013002302A1 - Power storage device - Google Patents

Abstract

Power generated by a solar cell can be appropriately distributed to superimposition on a system and charging.
The DC power generated by the solar cell 1 is converted into AC power, and then connected to the power line connecting the solar cell 1 and the power conversion device 3 of the power conversion device 3 superimposed on the system, A charging circuit for charging the storage battery 12 by stepping up or down the DC power generated by the solar cell 1 within a range not exceeding a predetermined ratio of the DC power generated by the solar cell 1 is there.
[Selection] Figure 1

Description

  The present invention relates to a power storage device that is used together with a power conversion device that links power generated by a solar battery to a system.

  In recent years, power conversion devices that are generated by solar cells and convert DC power to AC power and superimpose on the system are used. In this power conversion device, AC power is generated at night when the solar cells are not generating power. The power could not be output, and especially when a power failure occurred at night, no power was supplied.

  As a solution to such a problem, there has been one described in Patent Document 1, for example. The one described in Patent Document 1 is provided with a storage battery, in which the power generated by the solar battery is charged to the storage battery in the daytime, and the storage battery is charged with the power of the system at night time. It corresponded to.

Japanese Patent No. 3181423

  In the conventional power converter, the storage battery is configured on the premise that charging and discharging are repeated in a short period of time. That is, it was charged at daytime and discharged at night, or charged at night and discharged as a daytime power peak cut.

  When using a storage battery as a countermeasure in the event of a power failure, it is necessary to always maintain the storage battery close to full charge or a predetermined amount of power storage for a power failure that does not know when it occurs, but the storage battery self-discharges Therefore, it is necessary to charge intermittently according to the remaining capacity of the storage battery, and every time this additional charging is performed, all the power generation output of the solar cell is used for power storage operation and the supply of output to the grid interconnection device is stopped Met.

  In order to solve such a problem, it is an object of the present invention to provide a power storage device that can simultaneously charge a storage battery while superimposing the power generated by the solar battery on the grid. For example, when the cooling operation is performed with an air conditioner that is an AC load on the system, the power consumption of the air conditioner reaches a maximum around 2 to 3 pm in the cooling operation. On the other hand, the generated power of the solar cell reaches its maximum around 2 o'clock to 3 o'clock. Therefore, by allowing the generated power of the solar cell to be supplied to the air conditioner via the power converter, The peak cut can be performed where the power dependency on the system during the period when the power consumption is maximum can be reduced, but if the battery is charged during this period, the effect of this peak cut cannot be obtained. It is intended to provide a power storage device in which the peak cut effect and the charging of the storage battery are made compatible by controlling the generated power of the solar battery used in the above to one part of the whole.

  The power storage device of the present invention is connected to a power line connecting the solar cell of the power conversion device and the power conversion device so as to be superimposed on the system after converting the DC power generated by the solar cell into AC power, A charging circuit that boosts or lowers the DC power generated by the solar battery within a range that does not exceed a predetermined ratio of the DC power generated by the battery and charges the storage battery, and outputs the storage battery to a predetermined voltage And a booster circuit 4 that boosts the voltage to the power line.

  In addition, after the DC power generated by the solar battery is converted to AC power, it is connected to the power line connecting the solar battery and the power converter of the power converter configured to be superimposed on the system, and supplied to the power converter. A charging circuit that boosts or lowers the DC power generated by the solar battery within a range that does not exceed a predetermined percentage of the DC power that is set in advance and charges the storage battery, and boosts the output of the storage battery to a predetermined voltage. And a booster circuit 4 for supplying power to the power line.

  Moreover, after converting the output of a solar cell into alternating current power, it is connected to the power line which connects the solar cell of the power converter device and the power converter device which are superposed on the system, and the direct current power or power generated by the solar cell A charging circuit that steps down the DC power and charges the storage battery within a range that does not exceed a predetermined ratio of the DC power supplied to the converter, and boosts the output of the storage battery to a predetermined voltage. The storage battery is charged when the DC output exceeds a predetermined voltage higher than the rated voltage of the storage battery.

  In addition, a lead storage battery is used as a storage battery, constant voltage charging is performed at a voltage higher than a rated voltage obtained by combining a plurality of lead batteries, and the power required for the constant voltage charging is set at the predetermined ratio set in advance. When the corresponding electric power is exceeded, the voltage used for the constant voltage charging is lowered.

  The predetermined ratio is in the range of 10% to 20%.

  Further, the discharge of the storage battery is started in response to the switch operation.

  According to the present invention, the power used for charging the storage battery corresponds to a part of the generated power of the solar battery or the direct-current power supplied to the power converter, so that the remaining generated power is superimposed on the system and used in the load. For example, it becomes possible to simultaneously perform the peak cut effect and charge the storage battery.

It is explanatory drawing which shows the Example of this invention. It is a flowchart which shows the operation | movement at the time of charge. It is explanatory drawing which shows the other Example of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram showing an embodiment of the present invention. DC power generated by a solar cell 1 is supplied to a power conversion device 3 that converts DC power into AC power via a wiring 2. The solar cell 1 is formed by connecting a plurality of solar cell modules connected in series and in parallel to obtain a predetermined rated voltage and a predetermined rated output in series and / or in parallel. For example, the rated voltage is 300 V, the output is 2.4 Kw, the output is 4.8 Kw, and the like.

  The power conversion device 3 includes a booster circuit 4 that boosts the DC power supplied from the solar cell 1 side, and the pseudo sine based on the DC power boosted by the booster circuit 4 based on PWM (pulse width modulation) having the same frequency as the system 5. After being converted into a wave, it is further converted into AC power via a low-pass filter 6 and superimposed on the system 5. Here, the generated power of the solar cell 1 (DC power supplied to the booster circuit 4) and the power superimposed on the grid 5 must be equal. (However, the conversion loss and the power for operation are assumed to be “0”.) The generated power of the solar cell 1 can be obtained by the product of the current and voltage, and the power superimposed on the system 5 is superimposed on the system 5. It can be obtained by the product of the alternating current and the voltage of the system 5. In order to equalize these two electric powers, the DC power is boosted to such an extent that a current obtained by back-calculating the product (electric power) from the voltage of the system 5 which can be regarded as a substantially fixed voltage can be supplied to the system 5. Press to boost. In addition, the generated power of the solar cell 1 is constantly changing according to the amount of solar radiation, and the maximum amount of power generated according to the amount of solar radiation is also changed at the same time. Although it is obtained, it is impossible to obtain an open state every time, so in this control, the boosting circuit that maximizes the generated power of the solar cell while intentionally changing the current superimposed on the grid 5 and connecting the load A boost ratio of 4 is determined.

  By controlling in this way, the solar cell 1 can be substantially maintained in a state of generating the maximum generated power corresponding to the amount of solar radiation.

  The booster circuit 4 is mainly composed of a reactor, a switching element, a diode, and a capacitor to form a non-insulated switching power supply. The PWM conversion circuit includes an inverter circuit in which four switching elements are connected in a single-phase bridge shape. It has become. The low-pass filter 6 uses an L-type filter composed of a reactor and a capacitor.

  A control unit 7 of the power conversion device 3 controls the operation as described above, the open / close control of the normally open contact pieces 8a and 8b, the switching of the switching contact pieces 9a and 9b, and the like. Switching between the switching contacts 9a and 9b switches whether the AC output of the power converter 3 is supplied to the system 5 or output to the independent operation output outlet 10.

  The power storage device 11 uses, for example, a lead-type storage battery 12 (for example, a rated voltage of DC 48 V is obtained by combining four deep cycle types 105Ah in series and a total of eight batteries in two rows in parallel). The rated voltage is not limited to this, and any voltage such as 12V may be used. The output per hour may be changed according to the number of batteries connected in parallel. Moreover, a lithium ion battery etc. may be used and does not limit the kind of livestock battery.

  The charging circuit and booster circuit 4 (discharging circuit) constitutes a bidirectional charging / discharging circuit composed of two sets of single-phase inverter circuits 13 and 14 in which four switching elements are connected in a bridge shape and a transformer 15. Yes. In the following description, the winding ratio of the transformer 15 is assumed to be 1: 1, but when changing the winding ratio, the ON / OFF ratio of the switching element at the time of step-up / step-down is adjusted based on the winding ratio. An open / close contact 16 closes the contact when the power storage device 11 is charged and when the power storage device 11 is discharged. Reference numerals 17 and 18 denote current detectors, which are current detectors (current detectors such as direct current CT) for detecting the generated current of the solar cell 1 and the current supplied to the power converter, respectively. By detecting the voltage at the connection point V, each power can be obtained from the product of this current and voltage.

  When the storage battery 12 is charged, each switching element of the single-phase inverter circuit 13 is turned on / off by a signal based on PWM to convert the DC power obtained through the open / close contact piece 16 into a pseudo sine wave, and then the transformer 15. To the primary side (single-phase inverter circuit 13 side). PWM modulates a sine wave and a carrier wave, and the amplitude of the sine wave is feedback-controlled based on the output on the secondary side (single-phase inverter circuit 14 side) of the transformer 15. By changing the amplitude of the sine wave, the amplitude (voltage) of the sine wave induced on the secondary side of the transformer 15 changes. The AC power generated by the sine wave is full-wave rectified via diodes provided in parallel with the switching elements of the single-phase inverter circuit 14. The storage battery 12 is charged with the rectified DC power. The charge control detects the value of the applied voltage Vp and current Ip to the storage battery 12, and the amplitude of the PWM sine wave is feedback-controlled so that the applied voltage Vp is about 10% higher than the rated voltage of the storage battery 12. The For example, if the rated voltage of the storage battery 12 is 48V, feedback control is performed so that the applied voltage to the storage battery 12 is 52.8V. For example, if the rated voltage of the storage battery 12 is 12V, the applied voltage is 13.2V. Is feedback-controlled.

  The applied voltage to the storage battery 12 is not limited to a voltage that is 10% higher than the rated voltage, and may be set so as to be a charging applied voltage suitable for the storage battery 12 to be used. The charging power Pp at the time of charging is obtained by the product of the applied voltage Vp and the current Ip.

  The limit power Ps is set to a value of about 10% of the product of the power generated by the solar cell, that is, the current detected by the current detector 17 and the voltage at the connection point V. Note that this value is not limited to 10%, and may be arbitrarily changed according to the magnitude of the generated power of the solar cell 1. For example, if it is set according to the rated power generation amount of the entire solar cell, the storage battery 12 Taking into account the power required for charging when the charging characteristics are close to full, and ensuring the amount of power superimposed on the grid 5 when the amount of solar radiation decreases, as a guideline, the range is 10% to 20%. Can be set.

  When the amount of solar radiation decreases and the amount of power generated by the solar cell 1 decreases, the feedback control to PWM is regulated so that the power Pp used for charging the storage battery 12 does not exceed the limit power Ps. The applied voltage Vp to the storage battery 12 is lowered to reduce the current Ip used for charging. By controlling in this way, when the amount of solar cell power generation is reduced due to a decrease in the amount of solar radiation, the power generated by the solar cell is used for charging the storage battery 12 and the power superimposed on the grid 5 is eliminated or greatly reduced. The state which impairs the peak cut effect can be suppressed.

  The limited power Ps may be replaced with a product value of the current supplied to the power converter 3 (current detected by the current detector 18) and the voltage at the connection point V. In this case, when the storage battery 12 is charged with a power equivalent to a part of the power superimposed on the grid 5, the amount of solar radiation is reduced and the generated power of the solar battery is decreased, so that the power is superimposed on the grid 5. As the power decreases, the power supplied to the storage battery 12 also decreases.

  Reference numeral 19 denotes a control unit that performs these controls of the power storage device 11.

  FIG. 2 is a flowchart showing the operation at the time of charging. When charging is started, the charging voltage Vp 'of the storage battery 12 is set in step S1. For example, the voltage is set at 10% higher than the rated voltage of the storage battery 12. If the rated voltage of the storage battery 12 is 48V, Vp 'is 52.8V. Next, in step S2, a voltage Vp (substantially applied to the storage battery 12) used for control is set as a target value of the charging voltage with Vp = Vp '. In step S3, the limit power Ps is calculated. The value of Ps is a value of 10% of the power generated by the solar cell 1 (the product of the voltage at the connection point V and the current detected by the current detector 17), and the generated power of the solar cell 1 according to the amount of solar radiation. And fluctuates depending on the MPPT operation of the power converter 3.

  In step S4, the charge power Pv (product of Vp and Ip) is compared with the limit power Ps. When Pv> Ps, the charge power exceeds the limit power, so the charge voltage Vp of the storage battery 12 is determined in step S5. As a charging voltage Vp corrected by subtracting α, the process proceeds to step S6, where the voltage applied to the storage battery 12 is stabilized with this voltage Vp for charging. That is, the charging voltage of the storage battery 12 has a value of Vp lower than Vp ′. This stabilization is to perform feedback control from the secondary side of the transformer 15 to the single-phase inverter circuit unit 13 side.

  If the charge power does not exceed the limit power in step S4, the process proceeds to step S7, and the magnitude of Vp used for control and the value of Vp ′ obtained in step S1 is compared. When the condition of Vp> Vp ′ is satisfied, the charge power to the storage battery 12 may have exceeded the limit power Ps, and the power generation amount of the solar battery has been recovered. Are added to bring the value of Vp closer to the original value of Vp ′. After that, if the value of Vp increases and the condition of step S7 is not satisfied, the charging voltage Vp is returned to the value of Vp ′ in step S9.

  Therefore, the charging voltage Vp to the storage battery 12 is always performed within a range of 10% of the generated power of the solar battery. When it is determined in step S10 that the storage battery 12 is fully charged (when the charging current Ip to the storage battery 12 becomes equal to or less than a predetermined current value), the process proceeds to step S11 and the charging is terminated. If the predetermined current value is set to be equal to or less than the current value of the storage battery 12 that spontaneously discharges, the charging operation is continued without ending.

  When the storage battery 12 discharges, a pseudo sine wave is generated by PWM control as in the case of charging the switching element of the single-phase bridge circuit 14 and output to the secondary side of the transformer 15. With this output, the AC power induced on the primary side of the transformer 15 is full-wave rectified via a diode connected in parallel to the switching element of the single-phase bridge circuit 13 and connected via a capacitor and an opening / closing contact 16. V is supplied. The voltage of the DC power supplied to the connection point V is, for example, 300 V, and is set in the vicinity of the open-circuit voltage at the time of power generation by the solar cell, but is not limited to this and should be set according to the input conditions of the power converter 3. That's fine. An upper limit is set for the DC power supplied to the connection point V. This upper limit value is a value obtained by a 5-hour value or the like according to the capacity of the storage battery 12. The discharge power of the storage battery 12 can be determined by the product of the terminal voltage Vp and the current Ip of the storage battery 12.

  When discharging the storage battery 12 at the time of a power failure of the system 5, the system 5 is shut off and the switching contacts 9 a and 9 b of the power conversion device 3 are switched to supply AC power to the independent operation outlet 10. When the solar cell is generating power, both the generated power and the discharged power of the storage battery 12 can be supplied to the power conversion device 3.

  FIG. 3 is an explanatory view showing another embodiment of the power storage device. The same components as those shown in FIG. Reference numerals 20 and 22 denote switching elements connected in series, and diodes 21 and 23 are connected in parallel, respectively. In this series-connected circuit, a capacitor 24 is connected in parallel, and the plus side is connected to the connection point V via the open / close switch 16. A connection point between the switching element 20 and the switching element 22 is connected to the storage battery 12 through the reactor 25.

  In such a circuit, when charging the storage battery 12, a step-down circuit is configured in which the on / off of the switching element 20 is controlled so that the charging voltage Vp applied to the storage battery 12 becomes the voltage Vp ′. At this time, the switching element 22 remains in the off state. Since the charging voltage is stabilized by step-down, the voltage at the connection point V must be a predetermined voltage or higher and at least higher than the charging voltage of the storage battery 12. If the rated voltage of the storage battery 12 is 48V and the charging voltage is 52.8V, the voltage V at the connection point V needs to be at least about 60V. In the power storage device of FIG. The flowchart shown in FIG. 2 may be modified so that it operates when the output voltage of 1 is 60 V or higher.

  When discharging from the storage battery 12, the booster circuit is configured together with the reactor 25, the diode 21, and the capacitor 24 by maintaining the switching element 20 in the off state and turning the switching element 22 on / off. Since a circuit corresponding to a general-purpose non-insulated switching power supply is configured, detailed description thereof is omitted. The voltage supplied to the connection point V is, for example, 300 V, and feedback control for changing the ON duty of the switching element 22 is performed.

  In such a charge / discharge circuit, it is not necessary to increase the voltage at the time of charging, so that the charging circuit is simplified and the power storage device can be reduced in size and weight.

DESCRIPTION OF SYMBOLS 1 Solar cell 3 Power converter device 5 System | strain 11 Power storage device 12 Storage battery 13, 14 Single phase inverter circuit 15 Reactor 17, 18 Current detector

Claims (6)

After the DC power generated by the solar cell is converted to AC power, it is connected to a power line connecting the solar cell and the power conversion device of the power conversion device configured to be superimposed on the system, and is generated by the solar cell. A charging circuit for boosting or stepping down DC power generated by the solar battery to charge the storage battery within a range not exceeding a predetermined ratio of DC power set in advance, and boosting the output of the storage battery to a predetermined voltage And a step-up circuit that supplies the power line. After the DC power generated by the solar cell is converted to AC power, it is connected to the power line connecting the solar cell and the power converter of the power converter configured to be superimposed on the system, and supplied to the power converter A charging circuit for boosting or stepping down the DC power generated by the solar battery and charging the storage battery within a range not exceeding a predetermined ratio set in advance, and boosting the output of the storage battery to a predetermined voltage And a booster circuit that supplies the power line to the power line. After converting the output of the solar cell into alternating current power, connected to the power line connecting the solar cell and the power conversion device of the power conversion device configured to be superimposed on the system, the DC power generated by the solar cell or the A charging circuit that steps down the DC power and charges the storage battery within a range that does not exceed a predetermined ratio of DC power supplied to the power converter, and boosts the output of the storage battery to a predetermined voltage. And a booster circuit for supplying power to the power line, wherein the storage battery is charged when the DC output exceeds a predetermined voltage higher than a rated voltage of the storage battery. The storage battery is a lead storage battery, and constant voltage charging is performed at a voltage higher than the rated voltage obtained by combining a plurality of lead batteries, and the power required for the constant voltage charging corresponds to the predetermined ratio set in advance. The power storage device according to any one of claims 1 to 3, wherein a voltage used for the constant voltage charging is reduced when the power to be exceeded is exceeded. The power storage device according to any one of claims 1 to 4, wherein the predetermined ratio is in a range of 10% to 20%. The power storage device according to any one of claims 1 to 5, wherein discharging of the storage battery is started in response to a switch operation.

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