JP2010232586A - Photovoltaic power generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photovoltaic power generation system, making MPPT control of low power consumption through a simple structure by requiring no CPU control. <P>SOLUTION: The photovoltaic power generation system has a first solar cell and a second solar cell having same characteristics, and stores power generated using the first solar cell to a secondary battery, through a MPPT control circuit for maximizing generated power of the first cell. The MPPT control circuit has: a reference voltage setting means for setting an output voltage of the second solar cell to a power maximum point voltage, based on proportional information indicative of a proportion of the power maximum point voltage, in which generated power becomes maximum, to an open end voltage, in the first and second solar cells, and the open end voltage and the proportional information of the second solar cell; and a charging voltage regulating means for regulating the output voltage of the first solar cell to the power maximum point voltage, by comparing the power maximum point voltage of the second solar cell set by the reference voltage setting means, with the output voltage of the first solar cell. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solar power generation system that uses a solar battery to store electric power in a secondary battery, and more particularly to MPPT (Maximum Power Point Tracking) control of the solar power generation system.

  In recent years, solar power generation systems using solar cells have been widely used due to consideration of the global environment and ease of charging. The problem with such a solar power generation system is that the output power is not constant in the solar cell because the environment surrounding the solar cell changes from moment to moment. For example, the output power of the solar cell varies depending on the amount of light incident on the solar cell (sunshine amount), the operating temperature of the solar cell itself, and the like.

  Therefore, MPPT (Maximum Power Point Tracking) control that operates near the maximum power point where the generated power of the solar cell is maximized is devised so that the output energy of the solar cell can be efficiently extracted even if the environmental conditions change. ing.

  There are two main methods for MPPT control. One is a method called a hill-climbing method, which measures the voltage and current of a solar cell and tracks the maximum power point (see, for example, Patent Documents 1 and 2). In the case of the hill-climbing method, the circuit becomes complicated, and it is necessary to multiply the current and voltage for calculating the power, so that there is a problem that the CPU load increases and the power consumption increases.

  The other is a method called a voltage tracking method, in which a voltage of about 80% (in the case of a silicon solar cell) of the open voltage (maximum voltage) of the solar cell is tracked. This is because it is known that the maximum power value of a solar cell can be obtained at a substantially constant voltage value regardless of changes in the environment (for example, regardless of changes in the amount of sunlight). It is a method using. For example, in the case of a silicon solar cell, a voltage of about 80% of the open-circuit voltage (maximum voltage) is the maximum power point, and in the case of an amorphous solar cell, a voltage of about 68% of the open-circuit voltage is It is known to be the maximum power point. The voltage tracking method has a problem that it is a little less efficient than the hill-climbing method, but has the advantage that the circuit is simple and the control is simple. As a result, there is also an advantage that power consumption is small compared with the hill-climbing method.

JP-A-10-117440 Japanese Patent Laid-Open No. 7-225624

  However, when the voltage tracking method is performed using a circuit that performs conventional voltage tracking, for example, a PIC (Peripheral Interface Controller) confirms the voltage of a solar cell and performs PWM (Pulse Width Modulation) control, There is a problem that the open circuit voltage of the solar cell must be measured again. From such a viewpoint, also in the voltage follow-up method, a simpler configuration that does not require CPU control and a further reduction in power consumption are desired.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solar power generation system capable of realizing MPPT control with low power consumption with a simpler configuration that does not require CPU control. .

  In order to achieve the above object, a photovoltaic power generation system according to one aspect of the present invention includes a first solar cell and a second solar cell having the same characteristics, and generates electric power using the first solar cell. Is stored in the secondary battery via the MPPT control circuit for maximizing the generated power of the first battery, and the MPPT control circuit includes the first and second solar power generation systems. In the battery, based on the ratio information indicating the ratio of the maximum power point voltage, which is the voltage at which the generated power is maximum, to the open-end voltage, and the open-end voltage of the second solar cell and the ratio information, the second Reference voltage setting means for setting the output voltage of the solar cell to the power maximum point voltage, the power maximum point voltage of the second solar cell set by the reference voltage setting means, and the first solar cell Compare output voltage Te, characterized in that it and a charging voltage adjusting means for adjusting the output voltage of the first solar cell to the maximum power point voltage.

  In one embodiment of the present invention, two solar cells are prepared, the first solar cell is a charging solar cell, the second solar cell is a measurement solar cell, and the output voltage of the second solar cell is the second. By setting the maximum power point voltage at which the generated power of the solar cell is maximum and comparing the set maximum power point voltage with the output voltage of the first solar cell, the output voltage of the first solar cell is Since the adjustment is made to the maximum power point voltage at which the generated power of one solar cell is maximized, low power consumption MPPT control can be realized with a simple circuit configuration.

  In addition, the charging voltage adjusting means includes an operational amplifier and a voltage dividing circuit to which negative feedback is applied, and when the power generation voltages of the first solar cell and the second solar cell are different, the voltage dividing circuit is The output voltage of the first solar cell is divided so as to be the output voltage of the second solar cell, and the operational amplifier has the power of the second solar cell set by the reference voltage setting means. By inputting the maximum point voltage and the output voltage of the first solar cell divided by the voltage dividing circuit, respectively, by controlling the output voltage of the operational amplifier so that the two input voltages are equal, The charging voltage adjusting means may be configured to adjust the output voltage of the first solar cell to the maximum power point voltage.

  In this case, the voltage dividing circuit divides the output voltage of the first solar cell so as to be the output voltage of the second solar cell, and the operational amplifier is divided by the power maximum point voltage of the second solar cell. Since the output voltage of the operational amplifier is controlled so that the two input voltages are equal by inputting the output voltage of the first solar cell, the maximum power point voltage of the first solar cell can be easily followed. Can do. That is, MPPT control with low power consumption can be realized with a circuit configuration that does not require CPU control.

  Further, the charging voltage adjusting means includes an operational amplifier to which negative feedback is applied, and when the power generation voltages of the first solar cell and the second solar cell are the same, the operational amplifier is used for the reference. The power maximum point voltage of the second solar cell set by the voltage setting means and the output voltage of the first solar cell are respectively input, and the output voltage of the operational amplifier so that the two input voltages are equal. By controlling the above, the charging voltage adjusting means may be configured to adjust the output voltage of the first solar cell to the maximum power point voltage.

  In this case, the operational amplifier inputs the maximum power point voltage of the second solar cell and the output voltage of the first solar cell, and controls the output voltage of the operational amplifier so that the two input voltages are equal. Therefore, the power maximum point voltage of the first solar cell can be easily followed. That is, MPPT control with low power consumption can be realized with a circuit configuration that does not require CPU control.

  Further, the reference voltage setting means, in the circuit for measuring the open end voltage of the second solar cell, by dividing the measured open end voltage of the second solar cell based on the ratio information, You may comprise so that the output voltage of a said 2nd solar cell may be set to the said electric power maximum point voltage.

  In this case, the output voltage of the second solar cell can be set to the maximum power point voltage with a simple circuit configuration.

  Further, instead of the second solar cell, an illuminance measuring instrument that measures illuminance, and a voltage conversion circuit that converts the illuminance measured by the illuminance measuring instrument into a voltage, the reference voltage setting means includes: You may comprise so that it may set to the said electric power maximum point voltage from the voltage which the said voltage conversion circuit converted.

  In this case, the power maximum point voltage of the first solar cell can be easily followed by using the illuminance measuring instrument.

  According to the photovoltaic power generation system of the present invention, MPPT control with low power consumption can be realized with a simpler configuration that does not require CPU control.

1 is a schematic configuration diagram of a photovoltaic power generation system according to an embodiment of the present invention. It is an example of the circuit which comprises the electric power control part of FIG. It is another example of the circuit which comprises the electric power control part of FIG. It is an example of another circuit which comprises the dotted line part of FIG.

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

  FIG. 1 is a schematic configuration diagram of a photovoltaic power generation system 1 according to an embodiment of the present invention. A solar power generation system 1 shown in FIG. 1 includes two solar cells having the same characteristics, that is, a charging solar cell 2 and a measurement solar cell 3. The charging solar cell 2 is a solar cell for charging the secondary battery 6, and the electric power generated by the charging solar cell 2 is supplied to the secondary battery 6 via the MPPT control circuit 4 and the charging control circuit 5. Stored in On the other hand, the measurement solar cell 3 is a solar cell used for the MPPT control circuit 4 to maximize the generated power of the charging solar cell 2.

  In the present embodiment, the solar cell for charging 2 and the solar cell for measurement 3 employ single-crystal silicon solar cells, but the types of solar cell for charging 2 and solar cell for measurement 3 are limited to this. However, other materials may be used as long as the characteristics of the two solar cells are the same. For example, a polycrystalline silicon type or amorphous silicon type solar cell may be used.

  Moreover, in this Embodiment, the solar cell 3 for a measurement is comprised from the solar cell element of 1 cell, and the solar cell 2 for charging connects the solar cell element of N cell (N is a natural number of 2 or more) in series. Although it comprises, the cell structure of the solar cell 2 for a charge and the solar cell 3 for a measurement is not limited to this. For example, the number of cells of the charging solar cell 2 and the measuring solar cell 3 is the same, and, as will be described later, the charging solar cell 2 is composed of one cell solar cell element and the one cell solar cell element. It is good also as the solar cell 3 for measurement.

  In the present embodiment, the solar cell for charging 2 and the solar cell for measurement 3 are arranged so that the sunshine conditions and the operating temperature are the same. For example, they are arranged adjacent to each other in the same module. Of course, the arrangement of the solar cell for charging 2 and the solar cell for measurement 3 may be other than this as long as the same sunshine conditions and operating temperature are ensured. As will be described later, since the voltage value when the power of the solar cell is maximum is constant regardless of the sunshine conditions, the solar cell for charging 2 and the solar cell for measurement 3 do not necessarily have the sunshine condition and operation. It does not have to be arranged so that the temperatures are the same.

  The MPPT control circuit 4 is a circuit for maximizing the generated power of the charging solar cell 2, and in the present embodiment, the output voltage of the charging solar cell 2 is changed to the charging solar cell based on the voltage tracking method. The voltage is adjusted so as to be a predetermined ratio (hereinafter referred to as power maximization ratio) of the open-circuit voltage (maximum voltage) of the battery 2.

  In the present embodiment, as described above, charging solar cell 2 and measurement solar cell 3 are made of single crystal silicon, and therefore the power maximization ratio is about 80%. That is, the MPPT control circuit 4 adjusts the output voltage of the charging solar cell 2 to be 80% of the open-circuit voltage. It is known that this power maximization ratio is substantially constant without being affected by sunshine conditions. Of course, when a solar cell of another material is adopted, the output voltage of the charging solar cell 2 may be adjusted using the power maximization ratio of the adopted solar cell. For example, in the case of an amorphous silicon type solar cell, the voltage of about 68% of the open circuit voltage is the maximum power point.

  Further, in the present embodiment, the output voltage of the solar cell for charging 2 is adjusted to the maximum power point by using the output voltage of the solar cell for measurement 3 as a reference voltage. It will be described later.

  The charging control circuit 5 raises or lowers the voltage output from the MPPT control circuit 4 to a desired constant voltage and outputs the voltage to the secondary battery 6.

  Next, an example of a circuit of the power control unit 7 will be described with reference to FIG. FIG. 2 is a circuit configuration diagram of the power control unit 7 including the charging solar cell 2, the measurement solar cell 3, and the MPPT control circuit 4 of FIG. 1.

  The voltage generated by the measurement solar cell 3 is divided through the variable resistor 9 and input to the inverting input terminal (−) of the operational amplifier 10. In the present embodiment, the maximum resistance value of the variable resistor 9 and the input impedance of the operational amplifier 10 are high enough to be considered infinite. Therefore, when the variable resistor 9 is set to the maximum resistance value, the open-circuit voltage The situation close to is reproduced. Therefore, if the resistance of the variable resistor 9 is set in consideration of the above-described power maximization ratio (specifically, 80%), the maximum power generated by the measurement solar cell 3 is connected to the inverting input terminal of the operational amplifier 10. A point voltage (hereinafter also referred to as a power maximum point voltage. Specifically, a voltage that is 80% of the open-circuit voltage of the solar cell for measurement 3) is input.

  In the circuit shown in FIG. 2, the variable resistor 9 divides the output voltage of the measurement solar cell 3, but the voltage divider 8 described later is used to divide the output voltage of the measurement solar cell 3. May be.

  On the other hand, the voltage generated by the charging solar cell 2 is divided by the voltage divider 8 composed of two resistors and input to the non-inverting input terminal (+) of the operational amplifier 10. Specifically, in the present embodiment, since the power generation voltage of the charging solar cell 2 is N times the power generation voltage of the measurement solar cell 3, the output voltage of the charging solar cell 2 is a voltage divider. The voltage is divided by 1 / N through 8 and input to the non-inverting input terminal of the operational amplifier 10.

  As a result, since the operational amplifier 10 to which negative feedback is applied controls the output voltage of the operational amplifier 10 so that the two input voltages are equal, the divided voltage of the charging solar cell 2 is equal to that of the measurement solar cell 3. It is controlled to be equal to the maximum power point voltage. The output voltage of the operational amplifier 10 controls the gate voltage of the FET (Field effect transistor) 12, so that the current flowing between the source and drain of the FET 12 is adjusted. As a result, the charging solar cell 2 to the diode 13 are adjusted. Thus, the current output to the secondary battery 6 side (charging control circuit 5) is adjusted. That is, the power maximum point voltage of the charging solar cell 2 is output from the charging solar cell 2 to the secondary battery 6 side (charging control circuit 5).

  As mentioned above, according to this Embodiment, the solar cell 3 for a measurement is prepared separately from the solar cell 2 for a charge, the electric power maximum point voltage of this solar cell 3 for a measurement is measured, and the operational amplifier 10 is a solar cell for a charge Since the voltage divided to 1 / N times 2 is adjusted to be equal to the maximum power point voltage of the solar cell for measurement 3, the maximum power point voltage of the solar cell for charging 2 can be easily followed. it can. As a result, according to the photovoltaic power generation system 1 of the present embodiment, MPPT control can be realized with a simple circuit configuration that does not require CPU control.

  Moreover, according to this Embodiment, since the solar power generation system 1 can be operated only with the power consumption of the operational amplifier 10, the further low power consumption can also be implement | achieved. In the present embodiment, the operational amplifier 10 is operated by an external power supply. However, the operational amplifier 10 may be operated by power generation of the charging solar cell 2.

  Furthermore, according to the present embodiment, the operational amplifier 10 is always inputted with the maximum power point voltage of the solar cell 3 for measurement, so that it is quick to follow the maximum power point voltage of the solar cell 2 for charging. effective. That is, in the conventional voltage tracking method, since MPPT control is performed using one solar cell, it is sometimes necessary to measure the open-circuit voltage of the solar cell again, and environmental conditions such as sunshine conditions rapidly decrease. However, in the present embodiment, the maximum power point voltage of the solar cell for charging 2 is changed even if the environmental conditions such as the sunshine conditions are suddenly changed. It is possible to follow quickly.

  FIG. 3 is an example of a circuit configuration diagram of the power control unit 7 in the case where each of the charging solar cell 2 and the measurement solar cell 3 is configured by one solar cell element. In this case, the voltage output from the charging solar cell 2 does not need to be divided, so the voltage divider 8 is not provided. That is, the output voltage of the charging solar cell 2 is directly input to the non-inverting input terminal (+) of the operational amplifier 10. Further, in this case, the voltage output from the measurement solar cell 3 is divided by the voltage divider 14 composed of two resistors instead of the variable resistor 9, and the divided voltage is the inverting input of the operational amplifier 10. The signal is input to the terminal (-).

  Also in this case, the solar cell for measurement 3 is prepared separately from the solar cell for charging 2, the maximum power point voltage of the solar cell for measurement 3 is measured, and the operational amplifier 10 determines the output voltage of the solar cell for charging 2. Since the adjustment is made to be equal to the maximum power point voltage of the solar cell for measurement 3, the maximum power point voltage of the solar cell for charging 2 can be easily followed.

  In the present embodiment, the measurement solar cell 3 is used as a reference voltage, and the power maximum point voltage of the charging solar cell 2 is obtained. However, other devices and devices are used instead of the measurement solar cell 3. The maximum power point voltage of the solar cell for charging 2 may be obtained. For example, instead of the measurement solar cell 3, an illuminance sensor and a voltage conversion circuit that converts the illuminance measured by the illuminance sensor into a voltage may be provided to acquire the reference voltage.

  In this embodiment, the output voltage of the operational amplifier 10 is adjusted using the FET 12, but separately from this, the duty ratio (on / off time ratio) is controlled using PWM control. May be. FIG. 4 shows a circuit example in such a case. FIG. 4 is an example of a circuit corresponding to the portion 15 surrounded by a dotted line in FIG. In this case, there is an effect that power loss in the control element can be further reduced.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made to the embodiments of the present invention without departing from the gist of the present invention. Such modifications and changes can be made, and those accompanying such modifications and changes are also included in the technical scope of the present invention. Further, the actions and effects described in the embodiments of the invention only list the most preferable actions and effects resulting from the present invention, and the actions and effects according to the present invention are described in the embodiments of the present invention. It is not limited to what was done.

DESCRIPTION OF SYMBOLS 1 Photovoltaic power generation system 2 Solar cell for charge 3 Solar cell for measurement 4 MPPT control circuit 5 Charge control circuit 6 Secondary battery 7 Power control part 8, 14 Voltage divider 9 Variable resistor 10 Operational amplifier 12 FET
13 Diode

Claims (5)

An MPPT control circuit comprising a first solar cell and a second solar cell having the same characteristics, wherein the power generated by using the first solar cell is used to maximize the generated power of the first battery. A solar power generation system for storing in a secondary battery,
The MPPT control circuit
In the first and second solar cells, ratio information indicating the ratio of the maximum power point voltage, which is the voltage at which the generated power is maximum, to the open-circuit voltage;
Reference voltage setting means for setting the output voltage of the second solar cell to the maximum power point voltage based on the open end voltage of the second solar cell and the ratio information;
The power maximum point voltage of the second solar cell set by the reference voltage setting means is compared with the output voltage of the first solar cell, and the output voltage of the first solar cell is set to the maximum power. Charging voltage adjusting means for adjusting to a point voltage;
A photovoltaic power generation system comprising: The charging voltage adjusting means includes an operational amplifier and a voltage dividing circuit subjected to negative feedback,
When the generated voltage of the first solar cell and the second solar cell are different,
The voltage dividing circuit divides the output voltage of the first solar cell so as to be the output voltage of the second solar cell,
The operational amplifier inputs the maximum power point voltage of the second solar cell set by the reference voltage setting unit and the output voltage of the first solar cell divided by the voltage dividing circuit, respectively. By adjusting the output voltage of the operational amplifier so that the two input voltages are equal, the charging voltage adjusting means adjusts the output voltage of the first solar cell to the maximum power point voltage. The photovoltaic power generation system according to claim 1, wherein The charging voltage adjusting means includes an operational amplifier to which negative feedback is applied,
When the generated voltage of the first solar cell and the second solar cell are the same,
The operational amplifier inputs the power maximum point voltage of the second solar cell set by the reference voltage setting means and the output voltage of the first solar cell, respectively, and the two input voltages are equal. The solar cell according to claim 1, wherein the charging voltage adjusting means adjusts the output voltage of the first solar cell to the maximum power point voltage by controlling the output voltage of the operational amplifier. Photovoltaic system.   In the circuit capable of measuring the open-circuit voltage of the second solar cell, the reference voltage setting unit divides the measured open-circuit voltage of the second solar cell based on the ratio information. The photovoltaic power generation system according to any one of claims 1 to 3, wherein an output voltage of a second solar cell is set to the maximum power point voltage. Instead of the second solar cell, an illuminance measuring instrument for measuring illuminance,
A voltage conversion circuit that converts the illuminance measured by the illuminance measuring instrument into a voltage,
The reference voltage setting means includes:
The photovoltaic power generation system according to any one of claims 1 to 4, wherein the power maximum point voltage is set from a voltage converted by the voltage conversion circuit.

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