JP2015091181A - Measuring unit for use in photovoltaic power generation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an improving technique that, in measuring units for use in photovoltaic power generation each equipped with a measuring unit for monitoring generated electric power, serves to reduce the frequency of measuring unit stops when power needed for driving the measuring unit is supplied from a solar battery and makes available further reliable measurement data.SOLUTION: A measuring unit 5 for use in photovoltaic power generation comprises a measuring unit 8 for measuring the output of a solar battery 1 and a power supply unit 7 that supplies working power to the measuring unit 8 from the output of the solar batteries. The power supply unit 7 has a constant voltage circuit 10 that places the output voltage from the solar battery 1 under PWM control and supplies a prescribed voltage and a starter circuit 11 that supplies starting power to the constant voltage circuit 10. The constant voltage circuit 10 has a first output unit 18 that supplies operating power to the measuring unit 8 and a second output unit 15 that feeds back driving power to the constant voltage circuit.

Description

  The present invention relates to a measurement unit for photovoltaic power generation.

  In a photovoltaic power generation system, a plurality of solar cell modules are connected in series to form a string, and further, a plurality of strings are connected in parallel to form a solar cell, and power is supplied via an inverter that converts the power into a commercial AC power source. Supplying.

  In such a power generation system, a measurement unit that monitors the output of power, voltage, current, and the like in each string is provided in order to grasp the power generation status of the solar cell.

  The measurement unit requires electric power for driving, and a technique (Patent Document 1) using a solar cell in which the measurement unit is installed is disclosed as the power supply means.

  However, in the conventional technology that supplies the output necessary for driving the measurement unit from the solar cell, the voltage output from the string is dropped by the drop circuit, and whether or not the voltage is within the appropriate range is detected as a voltage. If it is judged by the circuit and it is within the appropriate range, the switch is turned on and the power is supplied to the measurement unit via the switching circuit. The power supply of was stopped. For this reason, even when power generation is performed with a string, if the output is less than a predetermined level, measurement of the amount of power generation is stopped, and measurement is frequently stopped depending on weather conditions and the like. Therefore, there is a problem that highly reliable measurement data cannot be obtained.

Japanese Patent No. 4630952

  The purpose of the present invention is to solve the above-mentioned problems and to grasp the power generation status of the solar cell, in the measurement unit for photovoltaic power generation provided with the measurement unit for monitoring the generated power, the power necessary for driving the measurement unit is obtained. When supplying from a solar cell, it is improving the frequency | count of a measurement unit being stopped, and providing the technique which makes available measurement data with higher reliability.

  The measurement unit for photovoltaic power generation of the present invention made to solve the above problems includes a measurement unit that measures the output of a solar cell, and a power supply unit that supplies operating power to the measurement unit from the output of the solar cell. A measurement unit for photovoltaic power generation, wherein the power supply unit includes a constant voltage circuit that supplies a predetermined voltage by PWM control of an output voltage from the solar cell, and a start circuit that supplies a start power to the constant voltage circuit The constant voltage circuit includes a first output unit that supplies operation power to the measurement unit, and a second output unit that feeds back drive power to the constant voltage circuit.

  According to a second aspect of the present invention, in the measurement unit for photovoltaic power generation according to the first aspect, the drive voltage fed back from the second output unit is generated from the voltage output from the starter circuit toward the constant voltage circuit. Is also characterized by a high value.

  The invention described in claim 3 is the measurement unit for photovoltaic power generation according to claim 1, wherein the voltage output from the first output unit and the voltage output from the second output unit are the same voltage. It is a feature.

  In the measurement unit for photovoltaic power generation according to the present invention, the measurement unit for photovoltaic power generation includes a measurement unit that measures the output of the solar cell, and a power supply unit that supplies operation power to the measurement unit from the output of the solar cell. The power supply unit includes a constant voltage circuit that supplies a predetermined voltage by PWM control of an output voltage from the solar cell, and a start circuit that supplies a start power to the constant voltage circuit, and the constant voltage circuit includes the measurement Since a configuration including a first output unit that supplies operation power to the unit and a second output unit that feeds back drive power to the constant voltage circuit is adopted, once the constant voltage circuit is activated , Even when the output from the solar cell decreases during measurement by the measurement unit, the power supply to the startup circuit decreases, and the voltage from the startup circuit to the constant voltage circuit decreases. The constant voltage circuit is switched from the second output section. Since the power supply for operation is fed back toward the chucking element, the measurement is frequently stopped when the output of the string is less than the predetermined level as in Patent Document 1, compared to the conventional technique. Thus, the measurement can be improved so that the frequency of stoppage is reduced, and more reliable measurement data can be obtained.

It is a block diagram which shows the outline of a solar power generation system. It is a block diagram explaining the structure of a measurement unit. It is a block diagram explaining the structure of a measurement part. It is a block diagram explaining the structure of a constant voltage circuit.

  Preferred embodiments of the present invention are shown below.

As shown in FIG. 1, the photovoltaic power generation system of the present embodiment includes a connection box 2 to which a plurality of strings 1 constituting a solar cell are connected.
Each string 1 outputs, for example, a maximum voltage of 750 V and is collected in the current collection box 3 via the connection box 2 and then sent to the power conditioner 4 to perform power conversion from direct current to alternating current. Is called.

  Inside the connection box 2 is provided a measurement unit 5 that monitors the power, current, and voltage that are output from the connected string 1.

  As shown in FIG. 2, the electric power generated by the string 1 is sent to the power conditioner 4 through the main electric circuit 6. The measurement unit 5 uses the output of the string 1 as an operating power source.

  As shown in FIG. 2, the measurement unit 5 is connected to a power supply unit 7 that supplies power to the current detection unit 9, a current detection unit 9 that measures the current in the main electrical path 6, and a voltage detection unit 27 that detects the voltage. It has a measuring unit 8.

  As shown in FIG. 2, the measurement unit 8 includes a microcomputer 21 that processes the measurement results of the current detection unit 9 and the voltage detection unit 27 and calculates power, and a communication device 22 that outputs the measurement results to a remote place by communication. It has.

  As shown in FIG. 3, the current detection unit 9 includes a Hall element 20 that measures the current in the main electric circuit 6. The current measuring means is not limited to the Hall element, and may be a magnetoresistive element, for example.

  As shown in FIG. 2, the power supply unit 7 converts the output of the string 1 into an optimum voltage as an operation power supply for the measurement unit 8 including the current detection unit 9 and the voltage detection unit 27, and the measurement unit 8 The constant voltage circuit 10 that supplies power to the power source, and the output voltage of the string 1 is converted into a voltage that is optimal for the activation of the constant voltage circuit 10, and the switching element 12 of the constant voltage circuit 10 that will be described later is supplied with power and activated An activation circuit 11 is provided.

In the starting circuit 11, the output voltage of the string is converted into a constant value by a voltage dividing circuit made up of a resistor. In the present embodiment, for example, when the output voltage of the string is 120 to 750 V, the start circuit 11 is adjusted so that a predetermined DC voltage is output.
The predetermined DC voltage is a voltage necessary for the switching element 12 provided in the constant voltage circuit 10 to operate stably. When the output voltage of the string is less than 120V, the predetermined DC voltage is not output.

  As shown in FIG. 4, the constant voltage circuit 10 includes a switching element 12 and a transformer 13.

  An output from the starting circuit 11 or an output from the second output unit 15 described later is supplied as a driving power source for the switching element 12 provided in the constant voltage circuit 10 and connected to the same terminal of the constant voltage circuit 10. Yes.

  The input unit 14 receives the output from the string 1, drives the switching element 12, performs PWM control with the switching element 12, and generates a rectangular wave. This rectangular wave is rectified by the secondary-side diode 16 via the transformer 13, and further, a DC voltage smoothed by the secondary-side electrolytic capacitor 17 is output from the first output unit 18.

Here, feedback control is performed by the adjustment circuit 19 so that the output voltage output from the first output unit 18 is kept constant.
Specifically, when the current is converted into a high-frequency pulse by switching of the switching element 12 and input to the input unit 14 of the transformer 13, the time between the ON state and the OFF state is determined according to the voltage output to the output unit 15. PMW control is performed to stabilize the output voltage by adjusting the ratio (duty ratio) and controlling the pulse width.

As shown in FIG. 2, the power output from the first output unit 18 is used as a power source for operation of the measurement unit 8 through the voltage conversion unit 25 of the measurement unit 8. The voltage conversion unit 25 further converts the output from the first output unit 18 to 5 V and supplies it as an operating power source for the current detection unit 9, the microcomputer 21, and the communication device 22.
In the present embodiment, as shown in FIG. 2, the first terminal unit 23 that directly outputs the power output from the first output unit 18 to the outside of the measurement unit 5 without passing through the voltage conversion unit 25; A second terminal unit 24 is provided for outputting the output converted to 5 V by the voltage conversion unit 25 to the outside of the measurement unit 5.
These terminal portions can be used as a power source for external devices (relays, storage batteries, wireless devices) installed outside the measurement unit 5 as necessary.
Further, by connecting a storage battery to these terminal portions 23 and 24, it is possible to supply power from the storage battery to the measuring unit 8 even when there is no output from the first output unit 18 and to operate it. .

  In addition to the first output unit 18, the constant voltage circuit 10 includes a second output unit 15 that supplies power as an operation power source for the switching element 12 incorporated therein. The second output unit 15 is set so that the winding ratio of the transformer is equal to the winding ratio of the first output unit 18, and outputs the same voltage as the first output unit 18. Further, the output of the second output unit 15 is smoothed by a diode or a capacitor built in the rectifier circuit 26 and supplied to the switching element 12. As a result, even when an external device is connected to the first terminal 23, it is not affected by load fluctuations, so that fluctuations in the voltage fed back to the switching element 12 can be suppressed.

In the present embodiment, the DC voltage output from the second output unit 15 is set to a higher value than the predetermined DC voltage output from the starter circuit 11, and both are connected to the same terminal of the constant voltage circuit 10. Therefore, after the constant voltage circuit 10 is activated, the power from the second output unit is always supplied to the switching element 12, and the constant voltage circuit 10 can continue to operate even when the output of the string 1 becomes low. .
That is, it is possible to measure the output of the string 1 without being affected by the output fluctuation of the string 1 as compared with the case where the switching element 12 is operated only by the voltage of the starting circuit 11.

  According to the present invention having the above configuration, once the constant voltage circuit 10 is activated, even if the generated power in the solar cell is reduced and the output to the activation circuit 11 is reduced, the constant voltage being driven Since the circuit 10 always feeds back the operation power supply from the second output unit 15 toward the switching element 12 of the circuit 10, the measurement is frequently performed when the power generation amount in the string 1 is less than a predetermined level. Compared to the prior art that has been stopped, measurement can be improved so that the frequency of measurement stoppage is reduced, and more reliable measurement data can be obtained.

1 String (solar cell)
2 Connection box 3 Current collection box 4 Power conditioner 5 Measurement unit 6 Main electric circuit 7 Power supply unit 8 Measurement unit 9 Current detection unit 10 Constant voltage circuit 11 Start-up circuit 12 Switching element 13 Transformer 14 Power supply input unit 15 Second output unit 16 Diode 17 Electrolytic capacitor 18 First output unit 19 Adjustment circuit 20 Hall element 21 Microcomputer 22 Communication device 23 First terminal unit 24 Second terminal unit 25 Voltage conversion unit 26 Rectifier circuit 27 Voltage detection unit

Claims (3)

A measurement unit for measuring the output of the solar cell;
A measurement unit for photovoltaic power generation comprising a power supply unit that supplies operating power to the measurement unit from the output of a solar cell,
The power supply unit PWM-controls the output voltage from the solar cell and supplies a predetermined voltage; and
A starting circuit for supplying a starting power to the constant voltage circuit;
The constant voltage circuit includes a first output unit that supplies operation power to the measurement unit;
A photovoltaic power generation measurement unit comprising: a second output unit that feeds back drive power to the constant voltage circuit. A drive voltage to be fed back from the second output unit,
The measurement unit for photovoltaic power generation according to claim 1, wherein the measurement unit is set to a higher value than a voltage output from the start-up circuit toward the constant voltage circuit. The measurement unit for photovoltaic power generation according to claim 1, wherein the voltage output from the first output unit and the voltage output from the second output unit are the same voltage.

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