JP2014192909A - Charger and power generating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charger which allows for stable charging in a short time, by preventing discharge of a battery during charge, without using an expensive device for making the voltage of a power line constant.SOLUTION: A charger 50 includes a battery 5, a charging line 55 having a switching element SW1 interposed between the battery 5 and a power line 7, a controller 5 for controlling a charging current Ic toward a target value through the switching element SW1, and voltage difference acquisition means 71 for acquiring the voltage difference of the voltage Vdc between the I/O ends 7a, 7b of the power line 7 and the voltage Vbt of the battery 5. When a determination is made that the warning conditions, where the voltage Vdc between the I/O ends 7a, 7b of the power line 7 goes below the voltage Vbt of the battery 5, are satisfied, the controller 4 controls the charging current Ic to lower, in preference to the control to a target value.

Description

  The present invention relates to a charging device capable of performing stable charging while suppressing discharge from a battery, and a power generation system including the charging device, in a forced charging mode in which the battery is forcibly charged.

  Battery charging can be roughly divided into two means: constant current charging and constant voltage charging. Among these, in order to perform charging in a shorter time, as disclosed in Patent Document 1, it is common to perform constant current charging. As an example of a charging device that performs constant current charging, a charging device 150 having a circuit shown in FIG. In such a charging device 150, the electric power supplied from the commercial power source 6 and rectified by the rectifier 61 is input to the battery 5 through the power line 7 or the like. At this time, the switching element SW1 and the like are controlled by a control unit (not shown) so that the current value of the charging current Ic becomes constant. The charging device 150 can also supply the power stored in the battery 5 to the load 64 via the power line 7 or the like. In this case, the discharge current is provided in parallel with the switching element SW1 from the battery 5. It flows to the power line 7 through the freewheeling diode 52.

JP 2005-261020 A

  By the way, in the charging device 150 capable of both charging and discharging as described above, the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 is installed in parallel between the input / output terminals 7a and 7b of the power line 7. It changes depending on the capacity of the capacitor 60, the amount of current Idc flowing through the switching element SW1, and the like. For example, it decreases as the current Idc increases. In the case of a charging device having an AC input circuit including a transformer between the commercial power supply 6 and the power line 7, the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 is the impedance of the AC input circuit. And also changes due to variations in the voltage of the commercial power source 6. On the other hand, the voltage Vbt of the battery 5 varies depending on the charging rate, and the voltage Vbt of the battery 5 tends to increase as the charging rate increases.

  As described above, the voltage of each device in the charging device 150 changes due to various factors. Therefore, when the change width increases, the voltage Vdc between the input / output terminals 7 a and 7 b of the power line 7 becomes higher than the voltage Vbt of the battery 5. When the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 becomes lower, the current flows from the battery 5 to the power line 7 through the freewheeling diode 52 even though it is in the charging mode. Flows and discharge from the battery 5 occurs. When the charging current Ic decreases due to this discharge, the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 increases and the amount of the charging current Ic increases again. Accordingly, the input / output terminals 7a and 7a of the power line 7 increase. There is a problem that an unstable operation in which charging / discharging is repeated such that the voltage Vdc between 7b decreases again, and overcurrent flows in some cases.

  In order to solve such a problem, a constant voltage device is provided for maintaining the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 constant, and the power line 7 is connected between the input / output terminals 7a and 7b. Although a method of keeping the voltage Vdc constant is conceivable, such a device is expensive, and it is not preferable to use it to make an inexpensive system.

  An object of the present invention is to effectively solve such a problem. Specifically, charging is performed without using an expensive device for maintaining a constant voltage between the input and output terminals of the power line. It is an object of the present invention to provide a charging device that can stably discharge in a short time while suppressing discharge of the battery.

  The present invention takes the following means in order to achieve such an object.

  That is, the charging device of the present invention connects in parallel between a battery that is charged and discharged with the power line, and an input / output terminal set on the power line and an input / output terminal of the battery. A charging line having a switching element arranged at a position, a discharging line bypassing the switching element, a charging current detecting means for detecting a charging current flowing into the battery through the charging line, and a detection result of the charging current detecting means Control means for controlling the charging current toward the target value through the switching element based on the voltage difference for obtaining a voltage difference between the voltage between the input and output terminals of the power line and the voltage of the battery The control means further comprises an acquisition means, wherein the charging current detected by the charging current detection means is less than a target value, and the voltage difference When it is determined that the precondition that the voltage between the input and output terminals of the power line is less than the voltage of the battery is satisfied based on the voltage difference acquired by the obtaining unit, the control is performed in preference to the control to the target value. Control is performed to reduce the charging current.

  Here, the precursor condition refers to a condition in which the voltage between the input and output terminals of the power line is predicted to be lower than the voltage of the battery after a predetermined time if the state where this condition is satisfied continues.

  If configured as described above, the charging current can be lowered when the charging current is less than the target value and the precursor condition is satisfied, so that the voltage between the input and output terminals of the power line is adjusted to a constant value. Without using an expensive device, the voltage between the input and output terminals of the power line and the voltage of the battery can be controlled so as not to reverse. Therefore, even if the target value of the charging current is set to be relatively large and a large current is input to the battery, the charging device that can suppress the discharge through the discharge line during charging and can perform stable charging in a short time Can be realized with an inexpensive system.

  In particular, in order to enable easy and appropriate control of the charging current without performing complicated control such as feedback control, the control means is based on the detection result of the charging current detection means. The charging current is controlled by changing the duty ratio of the switching element, and the amount of change of the duty ratio per control in the control of the charging current is limited to a predetermined amount, and the control of the charging current is performed. It is desirable to repeat the process at predetermined intervals.

  In order to easily perform the control as described above, it is preferable to control the switching element within a range in which the duty ratio and the charging current maintain linearity. For this purpose, the duty ratio of the switching element increases. As the voltage between the input and output ends of the power line decreases, the charging current increases after linearly increasing, and the control means is configured to reduce the voltage between the input and output ends of the power line. When the voltage difference obtained by subtracting the voltage of the battery is equal to or less than a voltage difference corresponding to the inflection point of the charging current or a predetermined voltage difference set slightly larger than the voltage difference, the precursor condition is Desirably configured to be satisfied.

  Further, in order to suppress the fluctuation of the voltage between the input and output terminals of the power line and enhance the above effect, a capacitor for storing power is arranged in parallel between the input and output terminals of the power line. It is desirable to do.

  Furthermore, in order to simplify the circuit configuration of the charging device by using a part of the charging line also as the discharging line, a free-wheeling diode that flows current in a direction opposite to the charging current is provided in parallel with the switching element, It is desirable that at least a part of the charging line is constituted by the switching element, and at least a part of the discharging line is constituted by the reflux diode.

  In the case of a power generation system that effectively uses the charging device, one or a plurality of power generation sources that generate electric power using renewable energy, and a power line to which the electric power is supplied from the power generation source, And the charging device connected to the power line.

  According to the present invention described above, when there is a possibility that the voltage between the input and output terminals of the power line and the voltage of the battery are reversed while controlling the charging current to the target value, the voltage is corrected by correcting the control. Since reversal can be suppressed, battery discharge during charging can be suppressed and stable charging can be performed in a short time without using an expensive device for keeping the voltage between the input and output terminals of the power line constant. A charging device can be provided.

The circuit diagram which shows the charging device which concerns on one Embodiment of this invention. The block diagram of a power generation system provided with the charging device. The graph showing the relationship between the duty ratio of a switching element, charging current, and voltage. The flowchart which shows the process performed by the charging device. The circuit diagram which shows the conventional charging system.

  Embodiments of the present invention will be described below with reference to the drawings.

  A charging device 50 according to this embodiment shown in FIG. 1 is provided in the power generation system 100 shown in FIG. 2, and uses the power supplied from the commercial power supply 6, the solar panel 1, the hydroelectric power generation device 2, and the wind power generation device 3. The battery 5 is stored.

  As shown in FIGS. 1 and 2, the charging device 50 is used for charging / discharging between the commercial power source 6, the solar panel 1, the hydroelectric generator 2, and the power line 7 to which electric power is supplied from the wind power generator 3. A battery 5, a DC / DC converter 51 interposed between the battery 5 and the power line 7, current detection means 70 for detecting a charging current Ic flowing from the DC / DC converter 51 into the battery 5, and the power line 7 A voltage difference acquisition means 71 for acquiring a voltage difference between the voltage Vdc between the pair of input / output terminals 7a and 7b and the voltage Vbt of the battery 5, and a controller 4 as a control means for controlling the DC / DC converter 51, etc. including.

  The battery 5 stores the power supplied from the commercial power source 6 and the power generated by the solar panel 1, the hydroelectric power generation device 2, and the wind power generation device 3, and discharges the stored power to the power line 7. .

  The DC / DC converter 51 functioning as a charge / discharge control device operates in response to an operation command from the controller 4 and adjusts the charging current Ic.

  As shown in FIG. 1, the DC / DC converter 51 includes two switching elements SW1 and SW2 each formed of a transistor. In addition, freewheeling diodes 52 and 53 are provided in parallel with the switching elements SW1 and SW2. As the switching elements SW1 and SW2, it is also preferable to use switching elements with freewheeling diodes having freewheeling diodes 52 and 53 inside. The switching element SW1 is connected to the input / output end 7a of the power line 7, and the switching element SW2 is connected to the input / output end 7b of the power line 7 and the low voltage side of the battery 5 (input / output end 5b of the battery 5). The element SW1 and the switching element SW2 are connected in series. Furthermore, a reactor 57 is interposed between the midpoint of switching element SW1 and switching element SW2 and the high voltage side of battery 5 (input / output terminal 5a of battery 5). Thus, the switching element SW1 is disposed at a position where the input / output ends 7a and 7b of the power line 7 and the input / output ends 5a and 5b of the battery 5 are connected in parallel. The switching elements SW1 and SW2 are reciprocally controlled so that when one is on, the other is off.

  At the time of charging, the charging current Ic passes through the charging line 55 extending from the input / output end 7a of the power line 7 to the input / output end 5a of the battery 5 through the switching element SW1 and the like as shown by a two-dot chain line in FIG. It flows into the battery 5. On the other hand, at the time of discharging, a discharge current flows out to the power line 7 through the discharge line 56 extending from the input / output terminal 5a of the battery 5 to the input / output terminal 7a of the power line 7 through the return diode 52 and the like. That is, the switching element SW1 and the free wheeling diode 52 cause currents to flow in opposite directions, and the charging line 55 and the discharging line 56 are configured by the same line except for the switching element SW1 and the free wheeling diode 52. The charging current Ic has an upper limit value determined by the battery 5, the switching element SW1, and the like.

  As shown in FIG. 3, the charging current Ic flowing through the charging line 55 increases linearly as the duty ratio of the switching element SW1 increases, and accordingly, between the input / output terminals 7a and 7b of the power line 7. The voltage Vdc decreases. When the voltage difference between the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 and the voltage Vbt of the battery 5 decreases to ΔV1, the charging current Ic reaches the inflection point Ic1 and starts to decrease. Therefore, the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 can be adjusted by controlling the duty ratio of the switching element SW1 and adjusting the amount of the charging current Ic. When the voltage difference between the voltage Vdc between the input / output terminals 7a and 7b and the voltage Vbt of the battery 5 is equal to or less than ΔV1, it is predicted that the linear relationship is broken and the control of the charging current Ic becomes unstable. Therefore, by setting the range in which the voltage difference exceeds ΔV1 as the control range, it is possible to stabilize the charging current Ic and to suppress the discharge phenomenon due to the reversal of the voltages Vdc and Vbt.

  The power line 7 is supplied with power from the commercial power source 6, the solar panel 1, the hydroelectric power generator 2, and the wind power generator 3, and one of the input / output terminals 7 a and 7 b of the power line 7 is a charging line. The other side is connected to the low voltage side of the battery 5. The voltage Vdc between the input / output terminals 7a and 7b of the power line 7 and the voltage Vbt of the battery 5 are DC voltages. As shown in FIG. 1, a capacitor 60 for storing power is arranged in parallel between the input / output terminals 7 a and 7 b of the power line 7 in the power line 7. In FIG. 2, a part of the apparatus shown in FIG. 1 such as the capacitor 60 is omitted.

  A solar panel 1 shown in FIG. 2 generates power using sunlight, which is renewable energy, and is configured by solar cells (not shown). The solar panel 1 is connected to a DC / DC converter 11, and the solar converter 11 outputs a direct current generated from the solar panel 1 to a power line 7 that is a bus.

  The solar converter 11 receives an operation command from the controller 4 and controls the output voltage or output current of the solar panel 1 so that the maximum power can be obtained from the solar panel 1 (Maximum Power Point Tracking). MPPT) control.

  The wind power generator 3 generates power using wind power, which is renewable energy. For example, a rotor including a generator (not shown) and a plurality of blades connected to a rotor of the generator and the generator The wind power generator 3 comprised from the battery which stores the electric power which generate | occur | produces more is mentioned. The wind power generator 3 can generate power by receiving wind and rotating the rotor. In addition, the said generator in the wind power generator 3 produces | generates alternating voltage, and after this is converted into direct voltage, it is given to the said battery in the wind power generator 3.

  The hydroelectric generator 2 generates power using hydropower that is renewable energy. For example, the hydroelectric generator 2 has a configuration in which a turbine (not shown), a generator, and a battery that stores electric power generated by the generator are integrated. Things. As long as a water flow can be ensured, the hydroelectric generator 2 can obtain a certain amount of power generation regardless of weather conditions. The generator in the hydroelectric generator 2 generates an AC voltage, which is converted into a DC voltage and then supplied to the battery in the hydroelectric generator 2.

  The wind power generator 3 includes a DC / DC converter (hereinafter referred to as “wind power generator converter”) 31 for wind power generation, and the hydroelectric generator 2 includes a DC / DC converter for hydroelectric power generation (hereinafter “converter for hydropower generation”). ) 21 is connected, and upon receiving an operation command from the controller 4, the DC output voltage supplied from the battery provided in each of the wind turbine generator 3 and the hydroelectric generator 2 is boosted to a specified value voltage of the power line 7. To output to the power line 7.

  The DC / AC inverter 62 is connected to the power line 7, receives an operation command from the controller 4, and receives direct current power supplied from the solar panel 1, the wind power generator 3, the hydroelectric power generator 2, or the battery 5. This is a power converter that electrically generates (reverses) AC power (for example, 200 V). Electric power is supplied from the battery 5 or the like to the load 64 via the DC / AC inverter 62. As the load 64, any electric appliance for home use, electric equipment in factories, offices, etc. can be used, and the output voltage is adjusted on the DC / AC inverter 62 side according to the specifications on the power receiving side. It is preferable to configure as described above.

  The commercial power supply 6 is connected to the power line 7 via the rectifier 61, and is configured to be able to supply power to the battery 5 and the DC / DC converter 41 via the power line 7.

  A DC / DC converter 41 as a control voltage generation unit is connected to the power line 7 and is obtained from the solar panel 1, the hydroelectric generator 2, the wind power generator 3, the battery 5, and the commercial power supply 6 through the power line 7. A control voltage is generated based on the electric power. The DC / DC converter 41 can step down the voltage appearing on the power line 7 and generate a control voltage (for example, 24V). Then, the generated control voltage is input to the controller 4, the solar power converter 11, the wind power generator converter 31, the hydroelectric power converter 21, the DC / DC converter 51 connected to the battery 5, and the DC / AC inverter 62. These devices perform each operation using the input control voltage.

  The controller 4 as control means controls the entire system according to a control program stored in a storage unit (not shown), and executes a normal control mode and a forced charging mode, which will be described later. The control program includes a normal control program corresponding to a normal control mode in which the DC / DC converter 51 performs constant voltage control, a forced charge program corresponding to a forced charge mode in which the DC / DC converter 51 performs constant current control, and the like. included.

  The normal control mode is executed at normal time, and the controller 4 reads the normal control program from the storage unit and operates according to the program in the normal control mode, thereby cooperating with peripheral hardware resources, A control signal is transmitted to the solar power converter 11, the wind power converter 31, the hydropower converter 21, the DC / DC converter 51, etc. (by giving an operation command), and the above-described MPPT control, boost control, and the like are performed. At the same time, the DC / DC converter 51 controls the constant voltage so that the voltage Vdc between the input / output terminals 7a and 7b of the voltage line 7 becomes a predetermined value. During this constant voltage control, the voltage Vdc between the input / output terminals 7a and 7b of the voltage line 7 is controlled so as to be always higher than the voltage Vbt of the battery 5, and the amount of charge current Ic and discharge current is determined for each power generation. It is determined by the difference between the power supplied from the devices 1, 2, 3 and the power supplied to the load 64. In other words, whether the battery 5 is charged or discharged is automatically determined according to the balance of power. By doing so, in the normal control mode, when the solar panel 1, the hydroelectric power generator 2 and the wind power generator 3 are sufficiently generating electric power, the load 64 is exclusively transmitted via the power line 7 from these. The electric power is supplied to the battery 5 and the battery 5 is appropriately charged. In addition, when the amount of power generated by the solar panel 1, the hydroelectric generator 2, and the wind power generator 3 is not sufficient, power is appropriately supplied from the battery 5 to the load 64.

  Further, the charging rate of the battery 5 has an upper limit value and a lower limit value. When the charging rate of the battery 5 exceeds a set range (at the time of charging limit), the DC / DC converter 51 is set so as not to be overcharged. By controlling, the battery 5 is not charged. On the other hand, when the charging rate of the battery 5 falls below the set range (at the time of discharge limit), the normal control mode is switched to the forced charging mode so that the overdischarge state does not occur, and the battery 5 is charged via the power line 7. To be done. The forced charging mode may be automatically executed when the predetermined condition is satisfied as described above, or may be executed according to a command given from the outside. Furthermore, if the battery 5 is charged at night when the power cost is low and the stored power is used during the day, the running cost can be reduced. In addition, peak power can be reduced by refraining from using the commercial power source 6 during the daytime.

  In the forced charge mode, the controller 4 reads the forced charge program from the storage unit and operates according to the program, thereby causing the DC / DC converter 51 to direct the charge current Ic to the target value in cooperation with peripheral hardware resources. Make constant current control to be performed. This target value is preferably set to the upper limit value of the charging current Ic described above, whereby a large current can be caused to flow into the battery 5 to shorten the charging time. In the forced charging mode in which constant current control is performed, the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 is determined according to the balance of power supplied to the power line 7.

  Specifically, as the constant current control, the controller 4 obtains the duty ratio at which the charging current Ic is directed to the target value based on the detection result of the charging current detection means 70 shown in FIG. 1, and the on / off operation is performed at the duty ratio. Thus, the switching element SW1 and the like are controlled. Further, the controller 4 determines that the charging current Ic detected by the charging current detecting means 70 is less than the target value and the voltage difference (input / output terminals 7a and 7b of the power line 7) acquired by the voltage difference acquiring means 71 shown in FIG. Based on the voltage Vdc between the battery 5 and the voltage Vbt of the battery 5), it is determined that the precursor condition that the voltage Vdc between the input / output terminals 7 a and 7 b of the power line 7 is less than the voltage Vbt of the battery 5 is satisfied. Then, the DC / DC converter 51 is controlled to lower the charging current Ic in preference to the above control to the target value.

  In the present embodiment, the controller 4 determines that the voltage difference ΔV1 corresponding to the inflection point Ic1 of the charging current Ic is a voltage difference obtained by subtracting the voltage Vbt of the battery 5 from the voltage Vdc between the input / output terminals 7a and 7b of the power line 7. In other words, when the voltage difference ΔV1 between the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 and the voltage Vbt of the battery 5 at the upper limit value of the control range shown in FIG. Then, control for reducing the charging current Ic is performed. By doing this, it is possible to avoid the region where the charging current Ic becomes unstable as described above, thereby preventing the reverse of the voltages Vdc and Vbt and suppressing the discharge.

  Note that the controller 4 has a voltage difference obtained by subtracting the voltage Vbt of the battery 5 from the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 slightly smaller than the voltage difference ΔV1 corresponding to the inflection point Ic1 of the charging current Ic. It may be configured to determine that the precursor condition is satisfied when the voltage difference is less than or equal to a predetermined voltage difference that is set to a large value, thereby further improving the charge / discharge stability of the battery 5. . Furthermore, for example, the greater the amount of change per unit time of the voltage difference acquired by the voltage difference acquisition means 71, the higher the risk that the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 will be lower than the voltage Vbt of the battery 5. Therefore, the voltage difference can be sequentially stored, and the controller 4 is configured to determine that the precursor condition is satisfied when the change amount of the voltage difference per unit time is equal to or greater than a predetermined value. Also good.

  Hereinafter, the processing performed in the charging device 50 will be specifically described mainly with respect to the control in the forced charging mode.

  As shown in the flowchart of FIG. 4, the controller 4 first determines whether or not the forced charging mode is set (step SP1), and determines that the mode is not the forced charging mode (step SP1: NO), the process is terminated. If it is determined that the current mode is the forced charging mode (step SP1: YES), the current value of the charging current Ic is acquired from the charging current detecting means 70, and the current value of the charging current Ic is the above-described upper limit value (target value). It is judged whether it is less than (step SP2). If the controller 4 determines that the charging current Ic is not less than the upper limit value, that is, greater than or equal to the upper limit value (step SP2: NO), the controller 4 decreases the duty ratio of the switching element SW1 shown in FIG. Processing is performed (step SP4), and this processing ends. The process for reducing the charging current Ic corresponds to the control to the target value described above. When the controller 4 determines that the charging current Ic is less than the upper limit value (step SP2: YES), the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 and the voltage Vbt of the battery 5 from the voltage difference acquisition means 71 And determine whether the acquired voltage difference is equal to or less than a predetermined value (step SP3). This predetermined value is a value that serves as a reference when the controller 4 determines whether or not the precursor condition is satisfied, and is a voltage difference ΔV1 corresponding to the inflection point Ic1 in the present embodiment. If it is determined that the voltage difference acquired here is equal to or less than a predetermined value, that is, the voltages Vdc and Vbt may be reversed (step SP3: YES), the duty ratio of the switching element SW1 is decreased by a certain value, and the charging current is reduced. Processing to lower Ic is performed (step SP4), and this processing ends. If the controller 4 determines that the voltage difference exceeds a predetermined value, that is, the voltages Vdc and Vbt are not likely to reverse (step SP3: NO), the controller 4 increases the duty ratio of the switching element SW1 by a constant value to increase the charging current. Processing to increase Ic is performed (step SP5), and this processing ends. The process of increasing the charging current Ic corresponds to the control to the target value. In the processing as described above, the duty ratio of the switching element SW1 is adjusted within the control range shown in FIG. The above process is repeatedly performed at a predetermined interval.

  In the power generation system 100 as described above, weather conditions and the like are monitored, and the controller 4 executes the above-described normal control program for changing the operation state of the solar panel 1 and the like accordingly. By doing so, for example, during the day of a sunny day when the wind is weak, although the amount of power generated from the wind power generator 3 is reduced, a large amount of power can be supplied from the solar panel 1 to the load 64 at night. When a sufficiently strong wind is blowing, it is possible to supply a large amount of power from the wind power generation device 3 to the load 64 although the solar panel 1 cannot generate power. In addition, during daytime on a windy and sunny day, the amount of power generated by both the solar panel 1 and the wind power generator 3 increases, so that it is possible to store surplus power in the battery 5 while supplying power to the load 64. it can. Moreover, since the power generation amount of the solar panel 1 and the wind power generator 3 decreases on a cloudy day when strong wind is not blowing, the shortage can be compensated by supplying the power stored in the battery 5 to the load 64. it can. Further, when the electric power stored in the battery 5 decreases, the electric power supplied from the commercial power supply 6 is stored in the battery 5 by shifting from the normal control mode to the forced charging mode, or supplied from the commercial power supply 6 to the load 64. It is configured to be able to.

  As described above, the charging device 50 of the present embodiment of the present embodiment includes the battery 5 that is charged and discharged with the power line 7, the input / output terminals 7 a and 7 b that are set on the power line 7, and the battery 5. The charging line 55 having the switching element SW1 disposed at a position connecting the input / output terminals 5a and 5b in parallel, the discharging line 56 bypassing the switching element SW1, and the charging flowing into the battery 5 through the charging line 55 A device comprising a charging current detection means 70 for detecting the current Ic and a controller 4 as a control means for controlling the charging current Ic toward the target value through the switching element SW1 based on the detection result of the charging current detection means 70. The voltage difference acquisition for acquiring the voltage difference between the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 and the voltage Vbt of the battery 5 The controller 4 further includes a stage 71, and the controller 4 has an input / output terminal of the power line 7 based on the voltage difference acquired by the voltage difference acquisition unit 71 when the charging current Ic detected by the charging current detection unit 70 is less than the target value. When it is determined that the precursor condition that the voltage Vdc between 7a and 7b is lower than the voltage Vbt of the battery 5 is determined, control is performed to lower the charging current Ic in preference to the control to the target value.

  As shown in FIG. 3, until the charging current Ic reaches the current amount Ic1, the duty ratio of the switching element SW1 and the charging current Ic are kept linear, and the charging current Ic flowing into the battery 5 through the charging line 55 is As the voltage increases, the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 decreases. Therefore, even if the charging current Ic is controlled to a preferable target value, the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 is lower than the voltage Vbt of the battery 5 due to various causes described in the background art. In spite of being charged, discharge occurs from the input / output terminals 5a and 5b of the battery 5 through the discharge line 56. In order to avoid this, it is also necessary to monitor the voltages Vdc and Vbt while controlling the charging current Ic to the target value, and correct the control when there is a possibility that the voltages Vdc and Vbt are reversed.

  On the other hand, when configured as described above, the charging current Ic can be set to the target value without using an expensive device for adjusting the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 to a constant value. If it is less than the above and the precursor condition is satisfied, the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 can be controlled not to fall below the voltage of the battery 5 by reducing the charging current Ic. Therefore, even if the target value is set to be relatively large and a large current is input to the battery 5, it is possible to suppress discharge from occurring through the discharge line 56 during charging, and charging that enables stable charging in a short time. The device 50 can be realized with an inexpensive system.

  In particular, the controller 4 controls the charging current Ic by changing the duty ratio of the switching element SW1 based on the detection result of the charging current detecting means 70, and the controller 4 controls the charging current Ic. Since the change amount of the duty ratio is limited to a predetermined amount and the control of the charging current Ic is repeatedly performed at predetermined intervals, the charging current Ic can be controlled without performing complicated control such as feedback control. Control can be performed easily and appropriately.

  The relationship between the duty ratio of the switching element SW1 and the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 and the charging current Ic indicates that the input / output terminal 7a of the power line 7 increases as the duty ratio of the switching element SW1 increases. , 7b decreases, and the charging current Ic increases linearly and then starts decreasing. The controller 4 determines that the voltage Vdc between the input / output terminals 7a, 7b of the power line 7 is greater than the voltage Vdc. When the voltage difference obtained by subtracting the voltage Vbt of the battery 5 is equal to or less than the voltage difference ΔV1 corresponding to the inflection point Ic1 of the charging current Ic or a predetermined voltage difference set slightly larger than the voltage difference ΔV1, Since it is determined that the precursor condition is satisfied, the duty ratio of the switching element SW1 and the charging current Ic maintain linearity. The switching element SW1 can be controlled within the range, and the control to the target value and the control to lower the charging current Ic can be easily performed.

  In particular, since the capacitor 60 for storing power is arranged in parallel between the input / output terminals 7a and 7b of the power line 7, the fluctuation of the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 is suppressed. Thus, the voltage Vdc between the input / output terminals 7 a and 7 b of the power line 7 can be reliably prevented from falling below the voltage Vbt of the battery 5.

  In addition, a free-wheeling diode 52 that allows current to flow in a direction opposite to the charging current Ic is provided in parallel with the switching element SW1, at least a part of the charging line 55 is configured by the switching element SW1, and at least a part of the discharge line 56 is formed of the free-wheeling diode Therefore, the circuit configuration of the charging device 50 can be simplified by using a part of the charging line 55 also as the discharging line 56.

  The power generation system 100 also includes a solar panel 1, a hydroelectric generator 2 and a hydroelectric generator 3 as power generation sources that generate electric power using renewable energy, and the power generated from these power generation sources 1, 2, and 3. Is provided with a power line 7 to which power is supplied and a charging device 50 connected to the power line 7, so that power can be stably supplied while using relatively unstable renewable energy. It becomes possible to supply.

  The specific configuration of each unit is not limited to the above-described embodiment.

  In the present embodiment, a part of the charging line 55 and a part of the discharging line 56 are configured as the same line, but the discharging line 56 may be a completely different line from the charging line 55.

  In this embodiment, the controller 4 acquires the voltage difference between the voltage Vdc between the input / output terminals 7 a and 7 b of the power line 7 and the voltage Vbt of the battery 5 via the voltage difference acquisition unit 71. Means for detecting the voltage Vdc between the input / output terminals 7a and 7b and the voltage Vbt of the battery 5, respectively. The controller 4 obtains the voltages Vdc and Vbt from such means, and the voltages Vdc and Vbt are obtained. You may comprise so that the said voltage difference may be acquired by calculating a difference.

  In this embodiment, when the voltage difference between the voltage Vdc between the input / output terminals 7a and 7b of the power line 7 and the voltage Vbt of the battery 5 is equal to or less than a predetermined value, the duty ratio of the switching element SW1 is decreased by a certain value. Although controlled, the reduction amount of the duty ratio may be changed according to the voltage difference. In this case, it is preferable to increase the reduction amount of the duty ratio as the voltage difference is smaller.

  Furthermore, in this embodiment, the controller 4 executes both the normal control program and the forced charging program. However, the present invention is not limited to this. For example, a controller that executes these programs is provided, and normal control is performed by one controller. You may comprise so that a program may be run and a forced charge program may be run by the other controller which is a control means higher than this controller.

  Furthermore, although the solar panel 1, the hydroelectric generator 2, and the wind power generator 3 were used as the power generator as a power generation source, other power generators such as a geothermal power generator may be further used. Or the wind power generator 3 may be used selectively.

  Other configurations can be variously modified without departing from the spirit of the present invention.

1, 2, 3 ... Power generation (solar panels, hydroelectric generators, wind generators)
4 ... Control means (controller)
DESCRIPTION OF SYMBOLS 5 ... Battery 5a, 5b ... Input / output terminal 7 ... Electric power line 7a, 7b ... Input / output terminal 50 ... Charging device 52, 53 ... Freewheeling diode 55 ... Charging line 56 ... Discharge line 70 ... Charging current detection means 71 ... Voltage difference acquisition means SW1 ... Switching element Ic ... Charging current Vdc, Vbt ... Voltage Ic1 ... Inflection point ΔV1 ... Voltage difference

Claims (6)

A battery to be charged / discharged to / from the power line, and a switching element disposed at a position connecting in parallel between the input / output terminal set on the power line and the input / output terminal of the battery A charge line and a discharge line bypassing the switching element; charge current detection means for detecting a charge current flowing into the battery through the charge line; and the charge current through the switching element based on a detection result of the charge current detection means Comprising control means for controlling the value toward the target value,
Voltage difference obtaining means for obtaining a voltage difference between the voltage between the input and output terminals of the power line and the voltage of the battery;
The control unit is configured such that the charging current detected by the charging current detection unit is less than a target value, and the voltage between the input and output terminals of the power line is based on the voltage difference acquired by the voltage difference acquisition unit. When it is determined that the precursor condition that indicates that the voltage is lower than the target voltage is determined, control is performed to reduce the charging current in preference to the control to the target value.   The control means controls the charging current by changing the duty ratio of the switching element based on the detection result of the charging current detection means, and the duty ratio per time in the control of the charging current is The charging device according to claim 1, wherein the change amount is limited to a predetermined amount and the control of the charging current is repeatedly performed at predetermined intervals. As the duty ratio of the switching element increases, the voltage between the input and output ends of the power line decreases, and the charging current increases linearly and then decreases.
The control means sets the voltage difference obtained by subtracting the battery voltage from the voltage between the input and output terminals of the power line, or a voltage difference corresponding to the inflection point of the charging current or slightly larger than this voltage difference. The charging device according to claim 2, wherein when the voltage difference is equal to or less than a predetermined voltage difference, it is determined that the precursor condition is satisfied.   The charging device according to claim 1, wherein a capacitor for storing electric power is arranged in parallel between input and output terminals of the power line. Provided in parallel with the switching element a reflux diode for flowing a current in a direction opposite to the charging current,
5. The charging device according to claim 1, wherein at least a part of the charging line is configured by the switching element, and at least a part of the discharging line is configured by the reflux diode. One or more power generation sources that generate power using renewable energy;
A power line to which the power is supplied from the power source;
A power generation system comprising: the charging device according to claim 1 connected to the power line.

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