JP2010087010A - Solar power generation apparatus, and method for controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar power generation apparatus suppressing a single operation of a booster, capable of minimizing loss of generated power due to stoppage of the booster and increasing an annual power generation amount of an entire power generation system. <P>SOLUTION: The solar power generation apparatus includes: a first solar cell string formed by connecting a plurality of solar cell modules in series; a second solar cell string including solar cell modules with less number compared to that of the first solar cell string, and a voltage regulating means connected in series to an output side of the solar cell element group, and connected to the first solar cell string in parallel; and a power conversion means provided in output sides of the first solar cell string and the second solar cell string, and having a control section following a maximum output operating point among the solar cell strings. In a single boosting operation of the voltage regulating means in the solar power generation apparatus, an output voltage of the second solar cell string is controlled to be increased or decreased stepwise. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a photovoltaic power generation apparatus and a control method thereof.

  A solar power generation device inputs power generated by a solar cell string in which a plurality of solar cell modules are connected in series to a power conditioner that is a power conversion device, and is supplied with power in an appropriate form to a load. However, under the installation conditions where the installation area is limited, such as a roof of a house, when a plurality of solar cell modules are arranged in a predetermined number, a fraction is often generated in the final row, and the solar cell module is often on the roof. A portion where the battery module is not installed may remain. In this case, not only the aesthetic appearance of the roof is impaired, but also a problem that the amount of generated power to be recovered decreases. Therefore, a booster that electrically boosts the output voltage is connected in series to such a fractional solar cell module, and a method of inputting an output substantially equal to the output power of other solar cell modules to the power conditioner. Is used.

This booster increases the voltage by switching control with a coil called a chopper circuit and a switching element, and even if the number of solar cell modules in series is smaller than the others, the output voltage can be increased to an arbitrary voltage value, Even if the number of series is not secured, the generated power can be supplied to the load side. (Patent Document 1)
JP 2004-146791 A

  By the way, in recent years, a solar power generation apparatus is provided with a mechanism for performing MPPT control (maximum output point tracking control) in a power conditioner or the like from the point of efficiently recovering the amount of power generation, and a solar cell in accordance with changes in solar radiation. The operating voltage point is changed so that the power generation output becomes the maximum power. However, when a booster is provided in a photovoltaic power generation apparatus having such an MPPT control mechanism, if the output voltage forcibly increased by the booster becomes higher than the generation voltage of other solar cell strings, the operating voltage The point can be set to the output voltage from the booster. In this case, the input of electric power to the power conditioner is limited to only from the solar cell string to which the booster is connected, and there is a problem that power generated by other solar cell strings is lost wastefully. In order to avoid such a situation, the booster device is provided with a mechanism that does not perform the boost operation (that is, stops the booster device) while the voltage of the other solar cell strings does not reach a certain value. However, such a mechanism is inherently inefficient because it does not utilize the power generated by the fractional solar cell module during the step-up operation.

  An object of the present invention is to provide a solar power generation device that can reduce the loss of generated power due to the stoppage of the booster as much as possible, can efficiently recover the amount of generated power, and is excellent in annual power generation.

  The solar power generation device of the present invention includes a first solar cell string formed by connecting a plurality of solar cell modules in series, a solar cell module having a smaller number than the first solar cell string, and the solar cell module. A second solar cell string connected in parallel with the first solar cell string, the first solar cell string, and the second solar cell string. Power conversion means provided on the output side of the solar cell string and having a control unit that follows the maximum output operating point of these solar cell strings, and during the single boost operation of the voltage adjustment means, The voltage adjusting means is controlled so that the output voltage of the solar cell string is stepped up or down stepwise.

  In one embodiment, the voltage adjusting means includes a first PWM control unit and a second PWM control unit having a signal frequency lower than that of the first PWM control unit, and the first PWM control unit. The signal of the control unit is stopped by the signal of the second PWM control unit, and the duty ratio of the signal of the second PWM control unit is changed, so that the output voltage of the voltage adjusting unit is stepped up stepwise. Alternatively, control is performed so as to step down the voltage.

  In one embodiment, the output voltage of the second solar cell string is stepped up or down stepwise in a range from the starting voltage of the power conversion means to the maximum output voltage of the second solar cell string. Be controlled.

  In one embodiment, control of the second solar cell string is released by matching the output voltage of the second solar cell string with the output voltage of the first solar cell string.

  The control method of the solar power generation device of the present invention includes a first solar cell string formed by connecting a plurality of solar cell elements in series, a solar cell module having a smaller number than the first solar cell string, A second solar cell string composed of voltage adjusting means connected in series to the output side of the solar cell module, the first solar cell string, and the second solar cell string are connected in parallel, and these A method for controlling a photovoltaic power generation apparatus, comprising: a power conversion unit provided on an output side of the solar cell string and having a control unit that follows a maximum output operating point of these solar cell strings, The voltage adjusting means includes a first PWM control unit and a second PWM control unit having a signal frequency lower than that of the first PWM control unit, and the first PW While stopping the control signal of the control unit with the signal of the second PWM control unit and changing the duty ratio of the signal of the second PWM control unit, during the single boost operation of the voltage adjusting means, And a step of controlling the output voltage of the voltage adjusting means to step up or step down.

  According to the solar power generation device of the present invention, since the output voltage of the voltage adjusting means constituting the second solar cell string can be controlled to be stepped down, the voltage adjusting means is in a single boost operation state. In this case, it is possible to avoid the single boosting operation at an early stage without completely stopping the voltage adjusting means, and the output voltage on the first solar cell string side reaches the rated input voltage of the power conditioner. And the maximum output operating point of the inverter can be automatically moved from the output point of the second solar cell string to the output point of the first solar cell string. In addition, when the first solar cell string does not reach the rated input voltage of the power conditioner, the output point of the second solar cell string can be operated as the maximum output operating point. Therefore, the obtained power generation amount can be efficiently recovered, and a solar power generation device having excellent annual power generation amount can be obtained.

  An embodiment of a solar power generation device of the present invention will be described in detail based on the drawings. FIG. 1 is a block diagram showing an embodiment of the photovoltaic power generation apparatus of the present invention, and FIG. 2 is a block diagram showing an embodiment of voltage adjusting means constituting the photovoltaic power generation apparatus shown in FIG. .

  As shown in FIG. 1, the solar power generation device 7 includes a first solar cell string 1a formed by electrically connecting a plurality of solar cell modules in series, and a solar cell module having a smaller number than the first standard string. And a second solar cell string 1b composed of voltage adjusting means connected in series to the output side of the solar cell element group, and outputs of the first and second solar cell strings connected in parallel. From the connection box 3 and the power conditioner 4 that is a power conversion means that converts the DC power collected in the connection box into AC power and supplies / reversely flows the current to the AC load 5 and the commercial power system 6. Become.

  The solar cell string 1a is formed by electrically connecting a plurality of solar cell modules formed by connecting solar cell elements in series and in parallel so that a voltage at which the power conditioner 4 can operate is obtained. For example, since an output voltage of only 24V can be obtained with one solar cell module of 175 W, when the rated input voltage of the power conditioner 4 is 100 V to 350 V, a solar cell string is configured by five series solar cell modules. Can do. On the other hand, when installing a solar cell module on the roof of a house, etc., it is not always possible to install the solar cell module in multiples of five due to limitations on the area of the roof. Therefore, in such a case, the solar cell module group that is less than the necessary number has an output equivalent to the output of other solar cell strings by using voltage adjusting means such as a booster capable of boosting the output. A solar cell string is formed. In the present invention, the one constituted only by the solar cell module is referred to as a first solar cell string, and the one constituted by the solar cell module and the voltage adjusting means is referred to as a second solar cell string. In FIG. 1, the first solar cell string 1a and the second solar cell string 1b composed of the solar cell module and the voltage adjusting means are connected to the respective backflow prevention diodes 31 in the connection box 3, respectively. Current is collected on one cathode side of the plurality of backflow prevention diodes 31 and connected in parallel. The backflow prevention diode 31 prevents the output from the other solar cell strings from flowing back to the output of the solar cell strings connected to each anode side. The collected output is transmitted to the power conditioner 4. The power conditioner 4 converts the DC power generated by the solar cell into AC power and is consumed by being supplied to a TV or refrigerator corresponding to the AC load 5 or by flowing excess power back to the commercial power system 6. Sell power. The power conditioner 4 is equipped with a solar cell maximum output tracking control unit (MPPT control unit) to efficiently input the power generated by the solar cell and convert the power, and this is the amount of solar radiation at that time. The power conditioner 4 follows the maximum output operating point of a plurality of solar cell strings and controls the operating voltage so that the generated power always becomes the maximum even if the generated voltage and generated current of the solar cell string fluctuate due to Is.

  Next, the power adjusting means 2 constituting the second solar cell string of the present invention will be described in detail. As shown in FIG. 2, the power adjustment means 2 protects a circuit from an external surge voltage or static electricity, or suppresses noise. An input EMI (radio noise interference) filter 21, a booster 22, a second solar cell string The power supply unit 23 for obtaining the power source for driving the entire voltage adjusting means from the output power of the solar cell module constituting the power source, detects the voltage state of the input side and the output side, and detects the maximum output operating point of the solar cell string 1b And a PWM (Pulse Width Modulation) control unit 24, a first drive unit 24a and a second drive unit 24b for driving the switching element of the boosting unit 22 by the PWM control unit 24, and an output EMI filter 25. Is done.

  First, the PWM control unit 24 detects the input side and output side voltages, detects the maximum output operating point of the second solar cell string 1b, and inputs the PWM signal to the first drive unit 24a. The one driving unit 24a switches the switching element of the boosting unit 22 based on the given PWM signal (first PWM control). As a result, the input voltage is boosted to the output voltage of the first solar cell string 1 a at a desired boost ratio, and the power collected in the connection box 3 is input to the power conditioner 4. In the present invention, in addition to the first drive unit 24a (first PWM control unit), a PWM signal having a frequency lower than the first frequency which is a PWM signal supplied to the first drive unit 24a. The second drive unit 24b (second PWM control unit) having the first PWM control unit is provided, and the signal of the first PWM control unit is stopped by the signal of the second PWM control unit. By switching from the second driving unit 24b to the boosting unit 22, the switching operation by the first driving unit 24a is controlled to be an intermittent operation, and the output voltage of the second solar cell string is stepped up or stepwise. Step down. Specifically, by changing the duty ratio of the signal of the second drive unit 24b (PWM control unit), control is performed so that the output voltage of the voltage adjusting unit is stepped up or down stepwise. In general, the voltage adjusting means includes the PWM control section 24 only by the first driving section 24a (first PWM control section). In this case, the output voltage forcibly increased by the voltage adjusting means 2 is used. However, when it becomes higher than the power generation voltage of the first solar cell string 1a, the operating voltage point of the power conditioner 4 is set to the output voltage from the voltage adjusting means 2. As a result, there arises a problem of so-called single boosting operation in which power is input to the power conditioner 4 only from the second solar cell string 1b to which the voltage adjusting means 2 is connected. In the present invention, by providing the second drive unit 24b (second PWM control unit), the output voltage of the voltage adjusting unit 2 can be stepped down or stepped up in steps. The single boosting operation of the means can be suppressed.

  Note that the MPPT control of the power conditioner 4 detects the maximum output operating point of the entire collected solar cell string and performs follow-up control regardless of the detection value of the maximum output operating point of the voltage adjusting means 2 described above. .

  Next, the control method of the present invention will be described in more detail using the signal pulse generation diagram of FIG. As shown in FIG. 3, for example, when the voltage starts to rise again after the output of the solar cell string has greatly decreased (when solar radiation gradually increases with sunrise), the output voltage of the first solar cell string 1a It takes a while for (standard output voltage) to reach the starting voltage of the power conditioner 4 (the voltage of the dotted line B in the figure). On the other hand, the output of the second solar cell string 1b is boosted by the booster circuit and has a voltage at point A (boosted output voltage) higher than point B, which is the starting voltage. Only the boosted output power is taken in as power conversion power. On the other hand, the power generation voltage of the first solar cell string 1a rises as solar radiation increases and reaches the voltage of the dotted line B in the figure, but the output voltage of the second solar cell string 1b connected in parallel is higher. Therefore, the generated power cannot be supplied to the power conditioner 4 and a so-called single boost operation state is established.

  A determination period is provided to cancel such a single boost operation state. During this determination period, the PWM signal for boosting is changed to control the voltage at point A stepwise down to the voltage at point B, and the point of coincidence with the standard output voltage equal to or higher than the starting voltage (point C) It is a period to detect. In this way, by gradually reducing the voltage, the loss of generated power is minimized, and the MPPT control target of the power conditioner 4 in the case of sudden change in solar radiation frequently causes the boosted output voltage and the standard output voltage to be reduced. Even when the interval is switched, the change width of the control voltage can be reduced, which is efficient. This determination period can be set periodically, and the above control is performed in the case of a single boost operation.

  Further, if a limiter that sets the lowering range of the rated input voltage (starting voltage) of the power conditioner 4 as the lower limit of the rated input voltage (starting voltage) of the power conditioner 4 is set as the power conditioner, the voltage range of the second solar cell string 1b (voltage adjusting means 2) is lowered. 4 does not stop and the loss of generated power can be reduced. In this case, the output voltage of the second solar cell string is controlled so as to be stepped up or down stepwise in a range from the starting voltage of the power conversion means to the maximum output voltage of the second solar cell string. Specifically, the control of the determination period is as follows. First, as described above, the output voltage of the second solar cell string 1b is lowered by ΔV by causing the voltage adjusting means 2 to operate intermittently by the second drive unit 24b. Furthermore, the ON time of the duty ratio of the PWM signal by the frequency of the second drive unit 24b (the duty ratio is represented by duty ratio = Ton / T, where ON time is Ton and frequency time is T) is gradually increased. The supply power is reduced stepwise by shortening the output voltage, and the output voltage of the second solar cell string 1b is lowered step by step by ΔV. As a result, at a certain point, the output voltage of the first solar cell string 1a becomes higher than the output voltage of the second solar cell string 1b, and the operating voltage point of the power conditioner 4 is changed from the first solar cell string 1a. Output voltage. Such a phenomenon confirms that the voltage of the first solar cell string (standard solar cell string) is measured by eliminating the voltage change amount ΔV of the output voltage in the PWM control unit 24. The PWM control unit 24 determines that it is normal when ΔV is no longer detected, and stops the PWM signal from the PWM control unit 24 to the second drive unit 24b.

  FIG. 4 is a flowchart of the above control. A PWM signal from the PWM control unit 24 is input to the first drive unit 24a, and the first drive unit 24a performs the switching operation of the switching element of the boosting unit 22 based on the given PWM signal. During this switching operation, step a0 shown in FIG. 4 is started, and the process proceeds to step a1.

  In step a1, the output voltage of the voltage adjusting means 2 is detected, fed back to the PWM control unit 24, and stored as V1.

  In step a2, the PWM signal from the PWM control unit 24 is input to the second drive unit 24b, and the second drive unit 24b performs intermittent operation by switching the booster unit 22 at a low frequency based on the given PWM signal. To start. Then, the PWM control unit 24 changes the duty ratio of the PWM signal given to the second drive unit 24b to set it to a desired voltage.

  In step a3, the output voltage of the voltage adjusting means 2 is detected, fed back to the PWM control unit 24, and stored as V2.

  In step a4, V1 stored in step a1 is compared with V2 stored in step a3. If V2 <V1, the process returns to step a1 and a1 to a4 are repeated. If V2 ≧ V1, the process proceeds to step a5, the control is canceled and the process is terminated.

  When a deviation (ΔV) in which the output voltage of the voltage adjusting means 2 decreases due to the control steps as described above, the PWM control unit 24 determines that the single boost operation is being performed. Then, this control step is repeated, and the PWM control unit 24 determines whether or not the step-up operation is performed step by step, and the control is canceled when there is no deviation in which the output voltage of the voltage adjusting unit 2 decreases. To do.

  On the other hand, when it is detected that the output voltage of the voltage adjusting unit 2 does not decrease as described above, the duty ratio of the PWM signal according to the frequency of the second drive unit 24b is then increased so as to increase the voltage. If the output voltage of the voltage adjusting means 2 does not further increase, the maximum output follow-up control of the power conditioner 4 is at the operating voltage on the first solar cell string (standard solar cell string) side. The operation of the PWM control by the unit 24b is stopped. Then, by performing the same operation periodically, it becomes possible to avoid the single boost operation by the second solar cell string, and the output on the first solar cell string side without completely stopping the boost operation. Whether or not the voltage has reached the rated input voltage of the power conditioner 4 can be detected, and at the same time, the operating point with the maximum output can be automatically moved to the first solar cell string side. In addition, since the power generation voltage of the solar cell changes due to solar radiation, it is desirable to check whether it is temporary or not. If the output voltage has a deviation ΔV again, the second solar cell string 1b Control is performed to lower the voltage of the (voltage adjusting means 2).

  In the series of controls as described above, since the voltage adjusting means 2 can continue to operate, the power generated by the second solar cell string 1b can be supplied even during the control, and the power conditioner 4 is also continuously operated. Can do. Therefore, it is possible to omit the power loss that stops the power conditioner 4 and the power loss that occurs when starting and stopping.

It is a block diagram which shows one Embodiment of the solar power generation device of this invention. It is a block diagram which shows one Embodiment of the voltage adjustment means which comprises the solar power generation device of FIG. It is a signal pulse generation figure for demonstrating the control method of the solar power generation device of this invention. It is a flowchart which shows the pressure | voltage rise control operation | movement of a control part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a: 1st solar cell string 1b: 2nd solar cell string 2: Voltage adjustment means 3: Connection box 4: Power conditioner 5: AC load 6: Commercial power system 7: Solar power generation device 8: Solar cell module 31: Backflow prevention diode 21: Input EMI filter 22: Boosting unit 23: Power supply unit 24: PWM control unit 24a: First driving unit 24b: Second driving unit 25: Output EMI filter

Claims (5)

A first solar cell string formed by connecting a plurality of solar cell modules in series;
The first solar cell string includes a solar cell module having a smaller number than the first solar cell string, and voltage adjusting means connected in series to the output side of the solar cell module, and is connected in parallel to the first solar cell string. Two solar cell strings;
A solar power source comprising: a power conversion means provided on an output side of the first solar cell string and the second solar cell string and having a control unit that follows a maximum output operating point of the solar cell strings. A photovoltaic device,
A photovoltaic power generation apparatus that is controlled so that the output voltage of the second solar cell string is stepped up or stepped down during the single step-up operation of the voltage adjusting means. The voltage adjusting means includes a first PWM control unit and a second PWM control unit whose signal frequency is lower than that of the first PWM control unit,
While stopping the signal of the first PWM control unit with the signal of the second PWM control unit,
2. The sun according to claim 1, wherein the output voltage of the voltage adjusting unit is controlled to be stepped up or stepped down by changing a duty ratio of a signal of the second PWM control unit. Photovoltaic generator.   The output voltage of the second solar cell string is controlled so as to be stepped up or down stepwise in a range from the starting voltage of the power conversion means to the maximum output voltage of the second solar cell string. The solar power generation device according to 1 or 2.   The control of the second solar cell string is released by matching the output voltage of the second solar cell string with the output voltage of the first solar cell string. The solar power generation device according to the section. A first solar cell string formed by connecting a plurality of solar cell elements in series;
A second solar cell string comprising a solar cell module having a smaller number than the first solar cell string, and voltage adjusting means connected in series to the output side of the solar cell module;
The first solar cell string and the second solar cell string are connected in parallel, provided on the output side of these solar cell strings, and the maximum output operating point of these solar cell strings is A control method for a photovoltaic power generation device comprising a power conversion means having a following control unit,
The voltage adjusting means includes a first control unit and a second PWM control unit whose signal frequency is lower than that of the first PWM control unit,
The control signal of the first PWM control unit is stopped by the signal of the second PWM control unit,
By changing the duty ratio of the signal of the second PWM control unit, control is performed so that the output voltage of the second solar cell string is stepped up or stepped down during the single step-up operation of the voltage adjusting unit. The control method of a solar power generation device including the process to do.

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