JP5849034B2 - Solar power conditioner and control method thereof - Google Patents

Description

  The present invention relates to a solar power conditioner and a control method thereof.

A transformer insulation type power conditioner and a solar cell module will be described.
In industrial applications and mega-solar photovoltaic power generation systems (systems with an output of 1 MW or more), a solar cell module and a junction box for intermediate connection between them, and this junction box is relayed to convert the DC voltage to an AC voltage. Consists of inverters to convert. A power conditioner that incorporates an insulation transformer is referred to as a transformer insulation type power conditioner.

  The solar cell module has a power generation amount of 180 to 250 W per sheet and a voltage of about 20 to 30 V. Since this is connected in series and parallel to obtain the total capacity, a solar power generation system of 100 kW class requires about 500 sheets when a 200 W panel is used. For example, an example of a general module is one with an open circuit voltage of 33.2V and a maximum output operating voltage of 26.6V. This is because the output varies depending on the module temperature even if the amount of solar radiation is the same. Change. Generally, as a characteristic of the solar cell module, the open voltage is lowered when the temperature is high, and the open voltage is increased when the temperature is low. For this reason, an opening of about 10% occurs in the output voltage depending on whether the temperature range at startup is 0 ° C. or higher or −20 ° C. or higher.

  Further, as a recent trend, the capacity of the solar cell module is increased, the W (watt) number of one module is increased, and the DC voltage control range tends to be larger than 600V. However, since this tendency increases only the upper limit, the power transmission efficiency increases. However, since the lower limit control range does not widen, only the conversion efficiency of the power conditioner does not increase.

  FIG. 5 shows a configuration of a conventional transformer-insulated power conditioner. In FIG. 5, 1 is a solar cell module, 7 is a system power supply, and 2 is a power conditioner. The power conditioner 2 includes a DC / AC converter 3, a filter reactor 4, a filter capacitor 5, and an insulating transformer 6. The power conditioner 2 controls the voltage / current generated by the solar cell module 1 so as to output a constant alternating voltage regardless of the voltage. For this reason, the input voltage range from the solar cell module 1 is prescribed | regulated so that the power conditioner 2 can be controlled to a fixed alternating voltage.

  Here, widening the input voltage range from the solar cell module 1 can be realized by increasing the voltage between the DC / AC converter 3 side of the isolation transformer 6 and the system power supply 7. However, increasing the step-up ratio increases the output current of the DC / AC converter 3 because the output capacity does not change. When the output current increases, the loss increases in the filter reactor 4 and the DC / AC converter 3, and the conversion efficiency of the transformer-insulated power conditioner 2 decreases.

  The power conditioner has a maximum power point tracking (MPPT) control function for efficiently extracting power from the output voltage and current of the solar cell module depending on the amount of solar radiation and temperature. Further, when converting a DC voltage into an AC voltage, the power conditioner is generally more efficient when the output AC voltage is higher and the current is lower. However, in order to increase the output AC voltage, the DC voltage for outputting the output AC voltage at a high waveform ratio must also be increased proportionally, and the control range of the solar cell module is biased toward the high voltage side and the control range Becomes narrow and power generation efficiency is lowered.

  Patent Document 1 includes a power conversion unit that converts a DC voltage of a solar cell into an AC voltage by PWM control, and a transformer that obtains a secondary voltage transformed using the AC voltage as a primary voltage. In an apparatus for obtaining AC power, a power conversion apparatus is provided in which a tap for changing a transformation ratio is provided in the transformer, and determination means for determining the tap of the transformer is determined from the correlation between the DC voltage and the AC output voltage. ing.

JP-A-4-355668

However, since the power converter of Patent Document 1 has a small capacity of the solar cell, it is basically configured to switch the tap of the transformer only by the magnitude of the DC voltage of the solar cell, and has recently been increased in capacity. It is not suitable for controlling solar cell modules. In addition, seasonal temperature changes, daily temperature changes, solar panel temperature changes, solar radiation changes, etc. are not considered.
That is, in the recent large-capacity solar cells, the range of the DC output voltage is expanded especially by expanding the upper limit. Therefore, a wide range from the upper limit of the DC voltage to the lower limit (low voltage stop) can be achieved by the power conditioner. If converted, conversion efficiency deteriorates. Further, in recent solar cells with a large capacity, the open-circuit voltage varies greatly depending on the temperature and the amount of solar radiation, and thus control that focuses on the temperature and the amount of solar radiation is required.

  Therefore, in the configuration in which the tap of the transformer is switched by the magnitude of the DC voltage of the solar cell disclosed in Patent Document 1, the upper limit of the DC voltage and the voltage range at the time of tap switching are widened in recent large-capacity solar cells. As described above, the conversion efficiency in the power conditioner is deteriorated.

  In response to changes in the output voltage characteristics due to changes in the temperature of the solar cell module, it is required to convert DC voltage to AC voltage without reducing the overall efficiency of the power conditioner. Although it is necessary to widen, in order to widen the lower limit, it is necessary to lower the output AC voltage of the power conditioner. However, if the output AC voltage is lowered here, the output current increases, so that the loss of the power conditioner increases and the conversion efficiency decreases.

  As a countermeasure to this problem, by changing the AC voltage for each season (estimated ambient temperature), the allowable range of the open voltage range due to the temperature change of the solar cell module can be narrowed, and the conversion efficiency of the power conditioner is lowered. It is conceivable to extend the control range of the inverter without any problems.

  In view of the conventional problems, the present invention provides a transformer-insulated power conditioner with a plurality of taps in the transformer, and switches the above-mentioned taps during cooperative operation in accordance with the season and temperature to switch the output AC voltage. The purpose of the present invention is to provide a power conditioner that widens the input voltage range and increases the overall conversion efficiency.

  In addition, the present invention increases the overall conversion efficiency by switching the AC voltage of the output of the transformer so that the starting voltage range corresponds to the starting use range such as 0 ° C. or higher, or −20 ° C. or higher. The purpose is to provide a power conditioner.

In order to solve the above conventional problems, the present invention generates a DC voltage from a solar cell module by an inverter and generates an AC voltage, and converts the AC voltage converted by the inverter into a primary AC voltage as a secondary voltage. In a solar power conditioner equipped with an insulation transformer for system voltage,
The insulation transformer is provided with a high step-up ratio tap having a high step-up ratio and a low step-up ratio tap having a low step-up ratio, and a changeover switch for switching and connecting the primary AC voltage to one of the two taps.
A calendar having season information and a detector for detecting the temperature of the solar cell module, and a controller for controlling the changeover switch based on the season information of the calendar or the temperature detected by the detector are provided. Features.

  Further, in the solar power conditioner described above, when the detector detects the temperature of the solar cell module lower than a predetermined temperature, the control unit connects the primary AC voltage to a low step-up rate tap, When the detector detects the temperature of the solar cell module higher than a predetermined temperature, the changeover switch is controlled to connect the primary AC voltage to the high step-up rate tap.

  Further, in the solar power conditioner described above, the control unit connects the primary AC voltage to a high step-up rate tap based on the winter season information of the calendar, and season information other than winter of the calendar. The changeover switch is controlled so as to connect the primary AC voltage to the low step-up rate tap.

  Further, in the solar power conditioner described above, when the detector detects a temperature of the solar cell module lower than a predetermined temperature in seasonal information other than winter in the calendar, the primary AC voltage To the low step-up rate tap, and when the detector detects the temperature of the solar cell module higher than a predetermined temperature, the changeover switch is controlled to connect the primary AC voltage to the high step-up rate tap. Features.

  Moreover, in the solar power conditioner described above, when the operation is stopped due to a decrease in the generated voltage during operation in a state where the primary AC voltage is connected to the low step-up rate tap, the primary AC voltage is Is operated by switching the connection from the low boost rate tap to the high boost rate tap.

  Moreover, the solar power conditioner described above is characterized in that the control unit connects the primary AC voltage to the high step-up rate tap when the apparatus is stopped.

In order to solve the above conventional problems, the present invention generates a DC voltage from a solar cell module by an inverter and generates an AC voltage, and converts the AC voltage converted by the inverter into a primary AC voltage as a secondary voltage. In the control method of the solar power conditioner that includes an insulation transformer as a system voltage and is controlled by the control unit,
The insulation transformer is provided with a high step-up rate tap having a high step-up rate and a low step-up rate tap having a low step-up rate, a changeover switch for switching and connecting the primary AC voltage to one of the two taps, a calendar having season information, A detector for detecting the temperature of the solar cell module;
The primary AC voltage is connected to one of the two taps by controlling the changeover switch based on season information of the calendar or temperature detected by the detector by the control unit.

  According to the present invention, the power generation efficiency can be improved and the input voltage range can be expanded by switching the tap of the transformer based on the module temperature of the solar cell and the ambient temperature change.

It is explanatory drawing of the power conditioner structure of this invention Example. It is explanatory drawing of the temperature characteristic example of a solar panel. It is an operation | movement flowchart of the power conditioner of this invention Example. It is a characteristic view of the electric power generation amount with respect to time of this invention, and panel temperature. It is explanatory drawing of the power conditioner structure of the conventional transformer insulation system.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram of the configuration of a power conditioner according to an embodiment of the present invention. Reference numeral 1 denotes a solar cell module, 7 denotes a system power supply, and 2 denotes a transformer insulation type power conditioner. The power conditioner 2 includes a DC / AC converter (inverter) 3, a filter reactor 4, a filter capacitor 5, and an insulating transformer 6. The DC voltage from the solar cell module 1 is converted into an AC voltage by the inverter 3, and the converted AC voltage is supplied as a primary AC voltage to the primary coil of the insulating transformer 6 via the reactor 4 and the capacitor 5. A secondary voltage obtained by transforming the primary AC voltage is generated in the secondary side coil of the insulating transformer 6, and this secondary voltage is supplied to the system power supply 7 as a system voltage.

  The power conditioner 2 controls the voltage / current generated by the solar cell module 1 to be a constant AC voltage regardless of the voltage. Here, an input voltage range from the solar cell module 1 is defined so that the power conditioner 2 can control a constant AC voltage.

  For example, in the case of a solar cell module having the characteristics as shown in FIG. The maximum output operating voltage is about 32 × 15 = 480 V at −20 ° C., 30 × 15 = 450 V at 0 ° C., 22 × 15 = 330 V at 60 ° C., and 19 × 15 = 285 V at 80 ° C. In addition, when the open circuit voltage is −20 ° C., 38 × 15 = 570 V, and when 0 ° C., 36 × 15 = 540 V, and in order to make the input voltage range from −20 to 80 ° C., DC285 to 570 V is used as the operating region. There is a need to.

  As described above, in order to widen the input voltage range, it can be realized by boosting the voltage between the inverter 3 side of the isolation transformer 6 and the system power supply 7. However, if the boost ratio is increased, the output current of the inverter 3 increases. As a result, the loss of the filter reactor 4 and the inverter 3 is increased, and the conversion efficiency of the power conditioner 2 is decreased.

  In this embodiment, the primary coil of the insulating transformer 6 (the coil on the inverter 3 side of the insulating transformer 6) has a high boosting rate tap 11 (130V tap) with a high boosting rate and a low boosting rate tap 10 (180V tap) with a low boosting rate. ). The taps 10 and 11 are respectively provided in primary coils of a three-phase UVW, and one ends of changeover switches 8 and 9 for switching and connecting the primary AC voltage of each phase converted by the inverter 3 are connected to each tap. Has been. One end of the changeover switch 9 is connected to the high step-up rate tap 11, and one end of the changeover switch 10 is connected to the low step-up rate tap 10.

  Reference numeral 12 denotes a control unit including a calendar 14 having season information and a detector 13 for detecting the temperature (panel temperature) of the solar cell module 1, and winter season information of the calendar 14 and season information other than winter. Alternatively, the changeover switches 8 and 9 are controlled to open and close based on the temperature of the solar cell module 1 detected by the detector 13. The control unit 12 controls the opening and closing of the changeover switch so that the other is opened when one of the changeover switches 8 and 9 is closed so that the other is not opened simultaneously.

  In addition to detecting the temperature of the solar cell module 1, the detector 13 detects the input voltage from the solar cell module 1 to the power conditioner 2 and the amount of solar radiation, and the control unit 12 detects these detected values. Each predetermined reference value (temperature, amount of solar radiation, input voltage) to be compared is stored, and control is performed based on a comparison between the detected value and each reference value.

  In the above configuration, the operation of the power conditioner 2 will be described with reference to the operation flowchart of FIG. In step (S) 100, the control unit 12 confirms the input voltage from the solar cell module 1 as a start-up preparation. If this value exceeds a predetermined reference value, the season information from the calendar 14 is read in S101. When the read information is seasonal information other than winter, the intensity of solar radiation is determined in S102. When the amount of solar radiation is weaker than the reference value, the temperature (panel temperature) of the solar cell module 1 is determined in S103. When the panel temperature is lower than the reference value, it is determined that the amount of power generation is large. In S104, the changeover switch 8 is closed and the changeover switch 9 is opened, and the primary AC voltage of each phase converted by the inverter 3 is converted into the low boost rate tap 10 Connect to supply (180V tap).

  Next, in S105, the operation is started with the tap connected. After the start of operation, the input voltage from the solar cell module 1 is monitored in S106, it is determined whether it is below a predetermined reference value (low voltage stop state), and if it is above the reference value, the process returns to S102 and the above operations are repeated.

  When the amount of solar radiation is strong in S102, it is determined that the amount of power generation is large, and the process proceeds directly to S104, and the operations from S104 to S106 are performed.

  The controller 12 reads the winter season information in S101, or determines that the power generation amount is small when the panel temperature is high in S103. In S107, it is determined whether or not the apparatus is stopped. If the apparatus is in operation, the operation is stopped in S108. If the apparatus is in operation, the process proceeds to S109. The changeover switch 8 is opened and the changeover switch 9 is closed. The primary AC voltage of each phase converted in 3 is connected so as to be supplied to the high step-up rate tap 11 (130 V tap).

  Next, in S110, the operation is started in the connected state of the high boosting rate tap. After the start of operation, the input voltage from the solar cell module 1 is monitored in S111, it is determined whether it is below a predetermined reference value (low voltage stop state), and if it is above the reference value, the process returns to S110 and the high boost rate tap Continue connected operation. If it is less than the reference value (low voltage stop state), it waits in S112, then returns to S100 and repeats the above operations.

  The reason why the operation stop process is once performed in S108 is that the operation in the connection state of the low boosting rate tap 10 (180V tap) in S105 may be continued along the route of S106-S102-S103-S170. This is because the switching connection from the low step-up rate tap 10 to the high step-up rate tap 11 is safely performed in the operation stop state.

  When the low voltage stop state is detected in S106, the primary AC voltage of each phase is connected so as to be supplied to the high boost rate tap 11 (130V tap) in S109.

  FIG. 4 is a characteristic diagram of the power generation amount and the panel temperature with respect to the time of one day according to the embodiment of the present invention. The characteristic of the upper half is a figure which shows the state of the electric power generation amount of the day in summer and winter, and the characteristic of the lower half is a figure which shows the state of the panel temperature of the day in summer and winter.

  In the above characteristics, since the amount of power generation is relatively large in the summer season (other than winter), the conversion efficiency of the power conditioner 2 is increased by using the low step-up rate tap 10 (180 V tap) except in the morning and evening (daytime). Since the power generation amount decreases in the morning and evening, the operation is performed to widen the input voltage range as much as possible by using the high step-up rate tap 11 (130 V tap). In the morning and evening, the amount of solar radiation decreases and the power generation amount decreases. However, since the panel temperature decreases and the power generation amount increases, it is necessary to switch taps in consideration of these, and this is performed according to the flow of FIG. Since the amount of power generation is small in the winter season, operation is performed throughout the day to widen the input voltage range as much as possible using the high step-up rate tap 11 (130 V tap).

  As described above, when the rated voltages of the low step-up rate tap 10 and the high step-up rate tap 11 of the isolation transformer 6 are AC 180 V and AC 130 V, respectively, the DC input voltage ranges from the respective solar cell modules 1 can be set as follows. .

Thereby, about the time of winter, it is used by high step-up rate tap 11 (AC130V tap) as temperature -20-60 degreeC and the range of input voltage DC285V-540V. For the summer season, the low voltage step-up rate tap 10 (180 V tap) is used at a temperature of 0 to 80 ° C. and an input voltage range of DC 330 to 570 V. However, as shown in FIG. 4, since the amount of power generation decreases in the morning and evening, the high step-up rate tap 11 (130 V tap) is used.
Winter: Temperature: -20-60 ° C
Switch: 8 off, 9 on, high step-up ratio tap 11 (AC130V tap)
Transformer input voltage: 130V
Input voltage range: DC285-540V
Summer: Temperature: 0-80 ° C
Switch: 8 on, 9 off, low boost ratio tap 10 (AC180V tap)
Transformer input voltage: 180V
Input voltage range: DC330 ~ 570V
Since the season information has a different temperature depending on the region (latitude), the calendar 14 includes information according to the region.

  Depending on the season, temperature, region, etc., it is possible to perform switching while stopped by command control or manual switching from the top by an external calendar function. For example, when the panel temperature of the solar cell module 1 is 0 ° C. or higher and the switch 9 is turned on, and the switch 8 is turned on with the start of −20 ° C., the switch 9 is given priority to the control range and the switch 8 is given priority to conversion efficiency. it can.

  As described above, according to the present embodiment, the power generation amount is grasped from the calendar seasonal information, the amount of solar radiation, and the panel temperature, and the high boost rate tap 11 (130 V tap) and the low boost rate tap 10 ( 180V tap), the primary AC voltage of each phase can be converted into a secondary voltage via an insulating transformer and supplied to the system power supply 7. Therefore, it is possible to perform an operation for widening the input voltage range by using the high step-up rate tap 11, and it is possible to perform an operation with priority on conversion efficiency by using the low step-up rate tap 10 (180 V tap).

  DESCRIPTION OF SYMBOLS 1 ... Solar cell module, 2 ... Power conditioner, 3 ... Inverter (DC / AC converter), 4 ... Filter reactor, 5 ... Filter capacitor, 6 ... Insulation transformer, 7 ... System power supply, 8, 9 changeover switch, 10 ... Low step-up rate tap, 11 ... high step-up rate tap, 12 ... control unit, 13 ... detector, 14 ... calendar.

Claims (8)

Inverter and solar power conditioners with an isolation transformer to a secondary voltage that is transformer the converted AC voltage by the inverter as the primary AC voltage and system voltage for converting a DC voltage from the solar cell module to ac voltage In na
The insulation transformer is provided with a high step-up ratio tap having a high step-up ratio and a low step-up ratio tap having a low step-up ratio, and a changeover switch for switching and connecting the primary AC voltage to one of the two taps.
A calendar with seasonal information, comprising a detector for detecting the temperature of the solar cell module, a control unit for controlling the changeover switches seasonal information or on the basis of the sensed temperature in the detector of the calendar is provided,
The control unit connects the primary AC voltage to a high step-up rate tap based on the winter season information of the calendar, and sets the primary AC voltage to a low step-up rate tap based on seasonal information other than the winter of the calendar. The solar power conditioner characterized by controlling the said changeover switch so that it may connect to . In the solar power conditioner according to claim 1 ,
In the seasonal information other than winter of the calendar, the control unit connects the primary AC voltage to a low step-up rate tap when the detector detects a temperature of the solar cell module lower than a predetermined temperature, and the detector The solar power conditioner, wherein when the temperature of the solar cell module higher than a predetermined temperature is detected, the changeover switch is controlled so as to connect the primary AC voltage to a high step-up rate tap. In the solar power conditioner according to claim 1 or 2 ,
The control unit connects the primary AC voltage from the low boost rate tap to the high boost rate tap when the operation is stopped due to a decrease in generated voltage during operation with the primary AC voltage connected to the low boost rate tap. A solar power conditioner characterized by switching and operating. In the solar power conditioner of any one of Claims 1-3 ,
The said control part connects in the stop state of an apparatus, when connecting the said primary AC voltage to a high step-up rate tap, The solar power conditioner characterized by the above-mentioned. Comprising an inverter for converting the DC voltage from the solar cell module to ac voltage, an isolation transformer to the transformed secondary voltage system voltage of the converted AC voltage by the inverter as the primary alternating voltage, the operation by the control unit In the control method of the solar power conditioner to be controlled,
The insulation transformer is provided with a high step-up rate tap having a high step-up rate and a low step-up rate tap having a low step-up rate, a changeover switch for switching and connecting the primary AC voltage to one of the two taps, a calendar having season information, A detector for detecting the temperature of the solar cell module;
The control unit connects the primary AC voltage to a high step-up rate tap based on the winter season information of the calendar, and sets the primary AC voltage to a low step-up rate tap based on seasonal information other than the winter of the calendar. The control method of the solar power conditioner characterized by controlling the said changeover switch so that it may connect to . In the solar power conditioner control method according to claim 5 ,
In the seasonal information other than winter of the calendar, the control unit connects the primary AC voltage to a low step-up rate tap when the detector detects a temperature of the solar cell module lower than a predetermined temperature, and the detector When the temperature of the solar cell module higher than a predetermined temperature is detected, the changeover switch is controlled so that the primary AC voltage is connected to a high step-up rate tap. In the control method of the solar power conditioner according to claim 5 or 6 ,
Wherein, when the operation by the lowering of the power generation voltage during operation in a state of connecting the primary AC voltage to a low boost ratio tap stops, connected to a high step-up ratio tapping the primary AC voltage from the low boost factor taps A method for controlling a solar power conditioner, characterized by switching the operation. A method for controlling a solar power conditioner according to any one of claims 5-7,
The said control part connects in the stop state of an apparatus, when connecting the said primary AC voltage to a high step-up rate tap, The control method of the solar power conditioner characterized by the above-mentioned.

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