JP2014072944A - Photovoltaic power generation system and boosting unit for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photovoltaic power generation system capable of suppressing heat evolution in a boosting unit without requiring increase in costs while improving efficiency of the entire system.SOLUTION: A photovoltaic power generation system composed of a solar cell circuit 1, a boosting unit 2, and a power conditioner 3 makes the boosting unit 2 raise voltage until the voltage reaches voltage at which a converter 6 in the power conditioner 3 stops its operation. The photovoltaic power generation system controls the boosting unit 2 so that a step-up width decreases to prevent temperature of a switching element in the boosting unit 2 from rising when the temperature of the switching element in the boosting unit 2 has reached predetermined upper limit temperature because of the voltage raising, and the step-up width returns again to an initial step-up width when the temperature has reached predetermined lower limit temperature.

Description

  The present invention relates to a photovoltaic power generation system and a booster unit thereof, and more specifically, a booster unit including a plurality of booster circuits capable of boosting a DC voltage output from each of a plurality of solar cell circuits, and such a booster knit. The present invention relates to a solar power generation system provided with

  Conventionally, in a photovoltaic power generation system, when a plurality of solar cell circuits having different output voltages are connected to a power conditioner, a boost unit (a boost connection box) is disposed between the solar cell circuit and the power conditioner. Yes.

  Many of this type of boosting unit has a plurality of boosting circuits capable of boosting the DC voltage output from each of the plurality of solar cell circuits, and one standard for directly outputting the DC current output from the solar cell circuit without boosting. Circuit (for example, Patent Document 1). The solar cell circuit having the highest output voltage among the solar cell circuits is connected to the standard circuit, the other solar cell circuits are connected to the booster circuit, and the output voltage of the solar cell circuit connected to the booster circuit is used as the standard circuit. The voltage is boosted to the output voltage of the connected solar cell circuit, aggregated with the output of the standard circuit, and input to the power conditioner. That is, a DC voltage having the same value as the output voltage of the solar cell circuit having the highest output voltage is supplied to the power conditioner.

  On the other hand, the power conditioner is provided with a converter (DC / DC converter) and an inverter (DC / AC inverter), and the DC voltage output from the boost unit is input to the converter. The inverter is input after boosting a predetermined AC power (for example, AC 200V AC power same as a commercial commercial power supply) to a predetermined voltage that can be output.

See FIG. 1 of Japanese Patent No. 4468372

  However, such a conventional configuration has the following problems, and improvements have been desired.

  That is, in the above-described configuration, the DC voltage output from the solar cell circuit is boosted in two stages by the boosting unit and the converter of the power conditioner, so that the efficiency of the entire photovoltaic power generation system is optimized. In particular, the efficiency drop was large at low power.

  In this regard, the booster unit is provided with the same number of booster circuits as the solar cell circuit, and using these booster circuits, all DC voltages output from the solar cell circuit are boosted to the predetermined voltage in the booster unit, That is, it is conceivable to employ a configuration in which the voltage is boosted by the boosting unit until the input voltage necessary for the inverter of the power conditioner to output predetermined AC power (required input voltage of the inverter) is reached.

  However, when boosting is performed only with the boosting unit in this way, the loss generated in the converter of the conventional power conditioner becomes the loss in the boosting unit. There is a risk of thermal damage. In addition, a large radiator is required to dissipate the switching element by the radiator, and there is a problem in that the cost of the boosting unit and thus the entire photovoltaic power generation system is increased.

  The present invention has been made in view of such problems. The object of the present invention is to improve the efficiency of the entire system and to suppress the heat generation in the boosting unit without increasing the cost. It is to provide a solar power generation system. In addition, a boosting unit for this purpose is provided.

  In order to achieve the above object, a photovoltaic power generation system according to claim 1 of the present invention includes a plurality of solar cell circuits and a plurality of booster circuits capable of boosting a DC voltage output from each of the plurality of solar cell circuits. A boost unit that outputs the DC voltage of one by connecting the outputs of the plurality of boost circuits in parallel, a converter that boosts the DC voltage output from the boost unit to a predetermined voltage, and the converter In the photovoltaic power generation system including a power conditioner having an inverter that converts a DC voltage into predetermined AC power, each booster circuit includes a control circuit that controls a boost ratio by a switching element, and Temperature detecting means for detecting temperature, and the control circuits share control information with control circuits of other booster circuits. And a voltage value lower than the target voltage when the detected temperature of the temperature detecting means is equal to or higher than a predetermined upper limit temperature. The second boost mode is set as a new target voltage, and the boost ratio is set based on the new target voltage.

  In the photovoltaic power generation system according to claim 1, in the boosting unit including a plurality of boosting circuits capable of boosting the DC voltage output from each of the plurality of solar battery circuits, a control circuit for controlling the boosting ratio of the boosting circuit Has two control modes, a first boost mode and a second boost mode.

  In the first boost mode, the voltage value of the boost target voltage of the converter of the power conditioner is used as the target voltage value of the output voltage boosted by the boost circuit, so that the voltage is output from the boost unit in the first boost mode. The DC voltage is an input voltage required for the inverter of the power conditioner to output predetermined AC power. Therefore, under this first boost mode, the converter of the power conditioner can be stopped, and the efficiency of the entire system can be improved.

  On the other hand, under this first boost mode, the boost ratio of the booster circuit is high, and therefore the loss of the booster circuit becomes large when the generated power in the solar cell circuit is large or the outside temperature is high. Heat generation of the switching element provided in the booster circuit is increased. Therefore, in the present invention, when the temperature of the switching element becomes equal to or higher than the predetermined upper limit temperature, the control circuit sets a voltage value lower than the target voltage in the first boost mode as a new target voltage, and this new A transition is made to a second boost mode in which the boost ratio is set based on the target voltage.

  Under this second boosting mode, the boosting ratio of the boosting circuit is lower than in the first boosting mode, so heat generation of the switching elements of the boosting circuit is suppressed. As a result, under this second boost mode, the temperature of the switching element changes from rising to falling, and the switching element is prevented from being damaged by heat. At this time, since the boosting ratio of the boosting circuit is lowered, the output voltage of the boosting unit is lower than that in the first boosting mode, but this reduction is boosted by operating the converter of the power conditioner. Even in the second boost mode, predetermined AC power is output from the inverter of the power conditioner.

  The photovoltaic power generation system according to claim 2 of the present invention is the photovoltaic power generation system according to claim 1, wherein the new target voltage in the second boosting mode is the highest among the input voltages of the boosting circuits. The voltage value is set to a high input voltage.

  That is, in the photovoltaic power generation system according to claim 2, since the target voltage set in the second boost mode is the voltage value of the highest input voltage (maximum input voltage) among the input voltages of the respective boost circuits. In this second boost mode, the booster circuit to which the maximum input voltage is input functions as a standard circuit, and the other booster circuits perform the boosting operation. Therefore, even when the temperature of the switching element is reduced in the second boost mode, the same operation as that of the conventional photovoltaic power generation system can be performed.

  The photovoltaic power generation system according to claim 3 of the present invention is the photovoltaic power generation system according to claim 1 or 2, wherein the output reduction rate of the boosting circuit in the second boosting mode is fixed to a constant value. It is characterized by that.

  That is, in the photovoltaic power generation system according to the third aspect, the output voltage of the booster circuit decreases in accordance with the output reduction rate fixed toward the new target voltage in the second boosting mode. By setting gently, it is possible to avoid sudden fluctuations in the output voltage of the booster circuit.

  The photovoltaic power generation system according to claim 4 of the present invention is the photovoltaic power generation system according to claim 1 or 2, wherein the output reduction rate of the booster circuit in the second boosting mode is a detected temperature of the temperature detecting means. It is characterized by being changed based on

  That is, in the photovoltaic power generation system according to claim 4, since the output reduction rate of the booster circuit in the second boost mode is changed based on the temperature detected by the temperature detecting means, it depends on the state of the switching element (element temperature). And an appropriate output reduction rate can be used. For example, when the temperature of the switching element does not decrease even after the transition to the second boosting mode, it is possible to take measures such as increasing the output reduction rate of the boosting circuit and quickly reducing the output voltage.

  According to a fifth aspect of the present invention, a booster unit includes a plurality of booster circuits capable of boosting a plurality of DC voltages, and outputs the plurality of booster circuits in parallel to obtain one DC voltage. The boosting circuit includes a control circuit that controls the boosting ratio by a switching element, and a temperature detection means that detects the temperature of the switching element. A first boost mode for setting a boost ratio using a necessary input voltage value of the inverter of the power conditioner as a target voltage, and a control circuit of the booster circuit; When the detected temperature is equal to or higher than the predetermined upper limit temperature, a voltage value lower than the target voltage is set as a new target voltage, based on the new target voltage. Characterized in that a second boost mode for setting the step-up ratio.

  According to the present invention, the control circuit that controls the boost ratio of the booster circuit in the booster unit of the photovoltaic power generation system has two control modes of the first booster mode and the second booster mode, Since the voltage value of the booster target voltage of the converter of the inverter is used as the target voltage value of the output voltage of the booster circuit, the operation of the converter of the power conditioner can be stopped and the efficiency of the entire system is improved. Can be made.

  Further, when the temperature of the switching element of the booster circuit rises in the first boost mode, the second boost mode is entered, and a new target voltage having a voltage value lower than that of the first boost mode is set as the target voltage value of the output voltage of the booster circuit. Therefore, heat generation of the switching element is suppressed, the element is prevented from being damaged by heat, and a heat dissipation measure can be taken at a low cost without performing an excessive heat dissipation design.

It is a block diagram which shows an example of schematic structure of the solar energy power generation system which concerns on this invention. It is a block diagram which shows schematic structure of the pressure | voltage rise unit of the solar power generation system. It is a flowchart which shows an example of the control procedure of the pressure | voltage rise unit in the solar power generation system. It is explanatory drawing which shows the relationship between the output voltage of a pressure | voltage rise unit and the temperature of a switching element in the solar power generation system. It is explanatory drawing of other embodiment of the solar power generation system, FIG. 5A shows the relationship between the output voltage of the boost unit and the temperature of the switching element, and FIG. 5B shows the output voltage of the boost unit. The relationship of elapsed time is shown respectively. It is a flowchart which shows an example of the control procedure of the pressure | voltage rise unit in other embodiment of the solar power generation system.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1
FIG. 1 shows a schematic configuration of a photovoltaic power generation system according to the present invention. As shown in FIG. 1, the photovoltaic power generation system according to the present invention includes a plurality of solar cell circuits 1, 1,..., A boost unit 2, a power conditioner 3, and a power system 4 as main parts. Has been.

  The solar cell circuit 1 is a circuit configured by connecting a plurality of solar cells (cells) in series and parallel to each other and connecting solar cell modules configured to obtain a necessary DC voltage and DC current in series. Yes, this solar cell circuit 1 is appropriately disposed in accordance with the structure or orientation of the place (for example, the roof) where the photovoltaic power generation system is installed. For example, in the case of a typical house-built roof, a plurality of solar cell circuits 1 having about 4 to 5 circuits are arranged. In FIG. 1, only a part of the circuit is omitted and only two circuits are shown.

  The step-up unit 2 is a connection box for collecting DC voltages output from each of the plurality of solar cell circuits 1 and inputting them to the power conditioner 3 as one output voltage. In this embodiment, the step-up unit 2 The unit 2 includes the same number (ie, a plurality) of booster circuits 5 as the number of solar cell circuits 1 so that the output voltages of the solar cell circuits 1 having different output voltage values can be input to the power conditioner 3 in a uniform manner. Each output of each booster circuit 5 is connected in parallel and output as one DC voltage (details of the booster unit 2 will be described later). In addition, this pressure | voltage rise unit 2 is comprised by the box-shaped metal case, and is normally arrange | positioned outdoors near the solar cell circuit 1. FIG. For this reason, the temperature in the boosting unit 2 (specifically, the temperature of a switching element described later) is easily affected by the outside air temperature.

  The power conditioner 3 is a grid-connected inverter device for linking the DC voltage output from the boosting unit 2 to the power system 4, and boosts the DC voltage output from the boosting unit 2 to a predetermined voltage V1. The converter 6 includes an inverter 7 for converting the DC voltage boosted by the converter 6 into predetermined AC power.

  More specifically, for example, when the power system 4 is a single-phase AC 200 V commercial power source, the inverter 7 is connected to the commercial power source in order to link the DC power generated by the solar cell circuit 1 to the commercial power source. The same single-phase 200V AC power must be output. In order for the inverter 7 to output this AC power, the converter 6 converts the DC power of the DC voltage (required input voltage value of the inverter 7) that can be converted into AC power of 200 V single-phase AC in the inverter 7 into the inverter 7. (That is, the predetermined voltage V1 that is the boost target voltage of the converter 6 is the required input voltage of the inverter 7. The required input voltage value is the AC power of the single-phase AC 200V by the inverter 7. Is set to about 350V).

  For this reason, the converter 6 of the power conditioner 3 shown in this embodiment is configured so that the DC voltage output from the boosting unit 2 (that is, the input voltage Vin to the converter 6) is less than the predetermined voltage V1. 6 is controlled to perform the boosting operation so that the output voltage Vout becomes the predetermined voltage V1, and when the DC voltage output from the boosting unit 2 is equal to or higher than the predetermined voltage V1, the boosting operation ( That is, the operation of the converter 6 itself is stopped. The voltage value at which converter 6 stops the boosting operation is hereinafter referred to as “Vin max”.

FIG. 2 shows a schematic configuration of the boosting unit 2.
As shown in FIG. 2, the booster unit 2 includes a plurality of booster circuits 5 having the same configuration, and each booster circuit 5 includes a booster circuit unit 51, a temperature sensor 52, and a control circuit. 53 as a main part.

  The booster circuit unit 51 is a circuit unit that boosts the DC voltage output from the solar cell circuit 1 based on the boost ratio set by the control circuit 53, and is not shown, but is based on a control signal from the control circuit 53. A switching element for switching and boosting the DC voltage. The step-up operation by this switching element is well known and will not be described here. However, the step-up ratio of the step-up circuit unit 51 is controlled by the switching of the switching element. The booster circuit unit 51 also includes a diode (not shown) that is used when the boost ratio set by the control circuit 53 is 1 (that is, when the input voltage is output as it is without being boosted). The booster circuit unit 51 also functions as a standard circuit.

  The temperature sensor 52 is temperature detecting means for detecting the temperature of the switching element provided in the booster circuit unit 51, and the temperature detected by the temperature sensor 52 is input to the control circuit 53. . The temperature sensor 52 may be attached to a radiator attached to the switching element, for example, in addition to the one attached directly to the switching element. That is, the temperature sensor 52 may be any sensor that can directly or indirectly detect the temperature of the switching element.

  The control circuit 53 is a control device that controls the boosting ratio in the boosting circuit unit 51 by controlling the switching element. The control circuit 53 is connected to the control circuit 53 of the other boosting circuit 5 in the boosting unit 2. It is configured to be communicable and configured to share control information with other control circuits 53. That is, when the control circuit 53 controls the booster circuit unit 51 of the booster circuit 5 provided with the control circuit 53, the control circuit 53 and the control information (for example, the target output voltage and booster of the booster circuit unit 51). The booster circuit unit 51 is controlled while sharing the input / output voltage of the circuit unit 51).

  Next, the operation of the photovoltaic power generation system configured as described above, in particular, the operation of the boosting unit 2 will be described with reference to FIGS. 3 and 4. FIG. 3 shows a control procedure of the boost unit 2, and FIG. 4 shows a relationship between the output voltage of the boost unit 2 and the temperature of the switching element.

  In the photovoltaic power generation system according to the present invention, each control circuit 53 provided in each booster circuit 5 of the booster unit 2 boosts the DC voltage output from the solar cell circuit 1 in the first boost mode and the second booster. The operation mode has two operation modes, and the boosting operation is performed while switching between these operation modes.

  Specifically, each control circuit 53 of the boost unit 2 starts to operate in the first boost mode when the input of the DC voltage generated by the solar cell circuit 1 to the boost circuit unit 51 is started. It is configured.

  In the first boost mode, each control circuit 53 uses the above-described required input voltage value of the inverter 7 (that is, the voltage Vin max at which the converter 6 stops the boost operation) as the target voltage output from the boost circuit unit 51. In addition, the boosting ratio of the booster circuit unit 51 is set based on the target voltage, and the boosting operation in the booster circuit unit 51 is started.

  As a result, a DC voltage boosted to the required input voltage of the inverter 7 is output from each booster circuit unit 51, so that the converter 6 of the power conditioner 3 stops operating, and only the inverter 7 operates. Therefore, the DC voltage output from the boosting unit 2 is input to the inverter 7 without being boosted by the converter 6, converted into AC power that can be connected to the power system 4 by the inverter 7, and connected to the power system 4. The system is done.

  The boosting operation of each boosting circuit unit 51 in the first boosting mode is set high so that the target voltage can stop the converter 6, so that the boosting ratio of the boosting circuit unit 51 is also high. For this reason, when the generated power in the solar cell circuit 1 is large or when the outside air temperature is high, the loss of the booster circuit unit 51 is increased and the heat generated by the switching element provided in the booster circuit unit 51 is increased. The temperature of the element tends to rise gradually.

  Therefore, each control circuit 53 starts monitoring the temperature (the temperature of the switching element) detected by the corresponding temperature sensor 52 when the boosting operation in the boosting circuit 51 is started in the first boosting mode. (See step S1 in FIG. 3). The temperature monitoring by each control circuit 53 periodically monitors whether or not the switching element is equal to or higher than a predetermined upper limit temperature T1 set in advance as a temperature allowable as heat generation (step S2 in FIG. 3). reference).

  Therefore, the upper limit temperature T1 set in this temperature monitoring is appropriately set within a range in which the switching element does not cause thermal destruction. Specifically, the characteristics of the switching element decrease as the temperature rises, and the loss in the booster circuit unit 51 increases. Therefore, the upper limit temperature T1 is a temperature at which the characteristics of the switching element do not excessively decrease ( For example, it is set to about 100 ° C.

  Then, when the determination in step S2 of FIG. 3 is affirmative, that is, as a result of temperature monitoring, if any of the control circuits 53 determines that the detected temperature of the temperature sensor 52 is equal to or higher than the upper limit temperature T1, Shifts to the second boost mode in order to lower the temperature of the switching element.

  In the second boost mode, each control circuit 53 changes the setting of the target voltage of the boost circuit unit 51 to a voltage value lower than the target voltage set in the first boost mode, and based on the new target voltage. Thus, the boosting ratio of the boosting circuit unit 51 is set, and the boosting operation in the boosting circuit unit 51 is performed (see step S3 in FIG. 3). The reason why the target voltage newly set in the second boost mode is set lower than the target voltage in the first mode is to suppress the heat generation of the switching element by lowering the boost ratio of the boost circuit unit 51. Therefore, an object is to reduce the temperature of the switching element by suppressing the heat generation of the switching element.

  In the present embodiment, the voltage value of the highest input voltage (input maximum voltage) among the input voltages of each booster circuit unit 51 is employed as a new target voltage set by each control circuit 53 in the second booster mode. Is done. This input maximum voltage is the voltage value of the highest output voltage in the solar cell circuit 1 connected to the boosting unit 2. Therefore, under this second boosting mode, the boosting circuit unit 51 to which the maximum input voltage is input has a boosting ratio of 1, and only the circuit 51 functions as a standard circuit that does not perform boosting. In 51, the boost ratio is set based on the new target voltage, and the boost operation is performed. That is, the boosting operation of the boosting unit 2 in the second boosting mode is the same boosting operation as that of the conventional boosting unit including the standard circuit and the boosting circuit.

  In the present embodiment, in controlling the boosting operation of each booster circuit unit 51 in the second boosting mode, each control circuit 53 (except the control circuit of the booster circuit 5 functioning as a standard circuit) is a booster circuit. The output voltage reduction rate of the output voltage of the unit 51 is fixed to a constant value, and the output voltage is gradually lowered. That is, each control circuit 53 avoids sudden fluctuations in the output voltage of the booster circuit section 51 by setting the output reduction rate gently. In addition, by controlling the boosting operation so as to avoid the sudden fluctuation of the output voltage of the boosting circuit unit 51 in this way, the sudden fluctuation of the output voltage from the boosting unit 2 is suppressed, and the malfunction of the power conditioner 3 is suppressed. Is also prevented.

  Thus, in the second boost mode, the output voltage from the boost unit 2 gradually decreases, and accordingly, the input voltage to the power conditioner 3 (that is, the input voltage Vin of the converter 6) also gradually decreases. Will be reduced. In other words, in the second boosting mode, the input voltage Vin of the converter 6 decreases from the voltage Vin max at which the converter 6 stops the boosting operation to the above input maximum voltage (see FIG. 4).

  Therefore, under this second boost mode, when the input voltage Vin of the power conditioner 3 starts to decrease, the converter 6 of the power conditioner starts the boost operation, and the output voltage Vout of the converter 6 is the required input of the inverter 7. It will operate to maintain the voltage. That is, even in the second boost mode, predetermined AC power is output from the inverter 7 of the power conditioner 3.

  In the second boost mode, each control circuit 53 is configured to periodically monitor the temperature detected by the corresponding temperature sensor 52, and the temperature sensor 52 that previously detected the upper limit temperature T1. When the detected temperature falls below the predetermined lower limit temperature T3 (see step S4 in FIG. 3), each control circuit 53 cancels the second boost mode and returns to the first boost mode (see FIG. 4).

  Here, the lower limit temperature T3 is appropriately set to a value lower than the upper limit temperature T1, but if the lower limit temperature T3 is too close to the upper limit temperature T1, the first boost mode and the second boost mode are intermittently repeated. Therefore, it is set to a temperature at which such a situation does not occur (for example, about 80 ° C.).

  When returning from the second boost mode to the first boost mode, each control circuit 53 sets the necessary input voltage value of the inverter 7 again as the target voltage of the output voltage. Also in the operation control of 51, the output increase rate of the output voltage of the booster circuit unit 51 is fixed to a constant value so that the output voltage rises gently, and sudden fluctuation of the output voltage is avoided. Yes.

  When the output voltage from boost unit 2 reaches the required input voltage of inverter 7, converter 6 of power conditioner 3 stops its operation.

  As described above, in the photovoltaic power generation system according to the present invention, the control circuit 53 uses the two control modes of the first boost mode and the second boost mode to control each boost circuit unit 51 in the boost unit 2. In the boost mode, since the required input voltage of the inverter 7 that is the boost target of the converter 6 of the power conditioner 3 is used as the target voltage of the output voltage of each booster circuit section 51, the power conditioner is used in the first boost mode. 3 can be stopped, and the efficiency of the entire system can be improved. On the other hand, when the temperature of the switching element of the boosting circuit unit 51 rises in the first boosting mode, the operation proceeds to the second boosting mode and the output voltage of the boosting circuit unit 51 is lowered. Heat damage is prevented. Therefore, a heat radiation measure can be taken at low cost without increasing the size of the radiator for the switching element.

Embodiment 2
Next, a second embodiment of the present invention will be described based on FIG. 5 and FIG.
The photovoltaic power generation system shown in the second embodiment is obtained by modifying the control content of the control circuit 53 of each booster circuit 5 in the booster unit 2 of the first embodiment described above. Specifically, the setting of the output reduction rate of each booster circuit unit 51 when shifting from the first boost mode to the second boost mode is modified. Since other configurations are the same as those in the first embodiment, the same reference numerals are given to portions having the same configurations, and the description thereof is omitted.

  The photovoltaic power generation system shown in the present embodiment is configured such that the output reduction rate of the booster circuit unit 51 in the second boosting mode is changed based on the temperature detected by the temperature sensor 52.

  FIG. 6 shows the control procedure of the booster unit 2 shown in the present embodiment. As shown in FIG. 6, each control circuit 53 is also connected to the solar cell circuit 1 in the solar power generation system shown in the present embodiment. When the input to the booster circuit unit 51 of the DC voltage generated at is started, each booster circuit unit 51 sets the necessary input voltage value of the inverter 7 as the target voltage value and starts the operation in the first boost mode. .

  Each control circuit 53 monitors the temperature detected by the corresponding temperature sensor 52 (see step S1 in FIG. 6), and determines whether the detected temperature is equal to or higher than a predetermined upper limit temperature T1 (FIG. 6). Step S2). If any control circuit 53 determines that the temperature detected by the temperature sensor 52 is equal to or higher than the upper limit temperature T1, each control circuit 53 shifts to the second boost mode.

  In the second boosting mode, in the boosting unit 2 of the present embodiment, the control circuit 53 that has detected the upper limit temperature T1 periodically detects the temperature detected by the temperature sensor 52, and the boosting circuit is based on the detected temperature. The output reduction rate of the unit 51 is changed. Specifically, the control circuit 53 determines whether or not the maximum value of the detected temperature of the temperature sensor 52 that has detected the upper limit temperature T1 has been updated (whether or not the temperature has increased from the previous time) (step S4 in FIG. 6). If the maximum value has been updated (Yes in step S4 in FIG. 6), the reduction rate is set higher than the output reduction rate set in the control circuit 53 in accordance with the update amount (that is, the initially set output). The output reduction rate is reset (see step S6 in FIG. 6) so that the reduction coefficient is multiplied by a predetermined coefficient α (where α> 1) to speed up the output reduction).

  That is, in the boosting unit 2 of the present embodiment, as shown in FIG. 5B, the control circuit 53 increases as the update range of the maximum value of the detected temperature of the temperature sensor 52 increases (if the temperature rise is large). Is set so as to increase the output reduction rate of the booster circuit section 51 (increase the slope shown in the figure), and prevent the temperature of the switching element from rising.

  On the other hand, if the maximum value of the detected temperature of the temperature sensor 52 that detected the upper limit temperature T1 has not been updated (No in step S4 in FIG. 6), the output reduction rate currently set in the control circuit 53 is maintained ( (See step S5 in FIG. 6).

  When the output voltage of the boosting unit 2 becomes the target voltage in the second boosting mode (Yes in step S7 in FIG. 6), thereafter, the same processing as that of the first embodiment, that is, the control circuit 53 first performs the upper limit temperature T1. It is determined whether or not the detected temperature of the temperature sensor 52 that has detected the temperature is equal to or lower than a predetermined lower limit temperature T3 (see step S8 in FIG. 6). Return to the boost mode (see step S10 in FIG. 6).

  As described above, in the photovoltaic power generation system shown in the present embodiment, the output reduction rate of the booster circuit unit 51 in the second boosting mode is changed based on the detected temperature of the temperature sensor 52, and accordingly, according to the temperature of the switching element. An appropriate output reduction rate can be set, and the temperature of the switching element can be reliably lowered even in a situation where the temperature of the switching element does not decrease when the reduction rate is fixed.

  The above-described embodiments show preferred embodiments of the present invention, and the present invention is not limited to these, and various design changes can be made within the scope of the invention.

DESCRIPTION OF SYMBOLS 1 Solar cell circuit 2 Booster unit 3 Power conditioner 4 Electric power system 5 Booster circuit 51 Booster circuit part 51
52 Temperature sensor (temperature detection means)
53 Control circuit V1 Predetermined voltage T1 Upper limit temperature T3 Lower limit temperature

Claims (5)

A plurality of solar cell circuits and a plurality of booster circuits capable of boosting a DC voltage output from each of the plurality of solar cell circuits are provided, and outputs of the plurality of booster circuits are connected in parallel to output one DC voltage. And a power conditioner having a converter that boosts the DC voltage output from the boost unit to a predetermined voltage, and an inverter that converts the DC voltage boosted by the converter into predetermined AC power. In the solar power generation system,
Each step-up circuit includes a control circuit that controls a step-up ratio by a switching element, and a temperature detection unit that detects the temperature of the switching element,
Each control circuit is configured to share control information with a control circuit of another boost circuit, and a first boost mode for setting a boost ratio using the voltage value of the predetermined voltage as a target voltage, and the temperature detection And a second boosting mode for setting a voltage value lower than the target voltage as a new target voltage and setting a boost ratio based on the new target voltage when the detected temperature of the means reaches a predetermined upper limit temperature or more. A solar power generation system characterized by   2. The photovoltaic power generation system according to claim 1, wherein the new target voltage in the second boost mode is set to a voltage value of the highest input voltage among the input voltages of the boost circuits.   The photovoltaic power generation system according to claim 1 or 2, wherein an output reduction rate of the booster circuit in the second booster mode is fixed to a constant value.   3. The photovoltaic power generation system according to claim 1, wherein an output reduction rate of the booster circuit in the second boosting mode is changed based on a temperature detected by the temperature detecting unit. A boosting unit comprising a plurality of boosting circuits capable of boosting a plurality of DC voltages, and outputting the outputs of the plurality of boosting circuits to a power conditioner as one DC voltage by connecting them in parallel,
The step-up circuit includes a control circuit that controls a step-up ratio by a switching element, and a temperature detection unit that detects the temperature of the switching element,
Each control circuit is configured to share control information with the control circuit of another booster circuit, and a first boost mode for setting a boost ratio using a necessary input voltage value of the inverter of the power conditioner as a target voltage When the detected temperature of the temperature detecting means is equal to or higher than a predetermined upper limit temperature, a voltage value lower than the target voltage is set as a new target voltage, and a step-up ratio is set based on the new target voltage. A boosting unit having a boosting mode.

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