Power controller and power control method

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a power control device and a power control method used in a power generation system using a power conversion device.

【0002】

[Conventional technology]

Due to the recent increase in awareness of the global environment, there are great expectations for power generation systems that use solar cells, which are safe and clean energy sources. However, since the output of a solar cell or the like fluctuates greatly depending on the amount of solar radiation, the temperature, and the operating point voltage, it is required to adjust the load seen from the solar cell and always take out the maximum power. For this purpose, various things have been proposed in the past. For example, using a monitor consisting of auxiliary solar cells or sensors that are used separately from the solar cell array for light intensity detection and temperature detection, the ever-changing weather conditions are grasped and the operating voltage is determined. The method, the so-called indirect method, is described in Japanese Patent Publication No. 61-2206. In addition, the so-called direct method, which determines the operating voltage by slightly fluctuating the operating point voltage and current of the solar cell array without using such an auxiliary sensor and examining the power fluctuation at that time, is specially announced 63-57807. It is described in the Gazette. Conventionally, a power conversion device or the like has been controlled so as to extract the maximum output from the solar cell by using the above method.

【0003】

[Problems to be Solved by the Invention]

However, the above method has the following problems.

【0004】

The indirect method requires a sensor used separately from the solar cell array or a monitor such as solar radiation detection composed of solar cells, and a meteorological condition measured by the monitor or a parameter representing the meteorological condition. It was necessary to fully understand the relationship between the operating point voltage and the power of the solar cell array to be controlled. Accurately grasping this relationship required long-term precise measurements and was very cumbersome. In addition, the area of the solar cell array is usually several square meters or more, whereas the monitor is small, so that a measurement error or the like may occur in the entire solar cell array. For example, when detecting the amount of solar radiation, if the monitor part is covered with shadow for some reason, it will be judged as "dark" even though the entire solar cell array is exposed to solar radiation, and accurate control will be performed. I couldn't do it.

【0005】

In the direct method, since an auxiliary monitor used separately from the solar cell array is not used, the maximum power point of the solar cell array can always be tracked. However, in this method, in order to improve the tracking accuracy, it is necessary to investigate the optimum operating voltage in a wide range in detail. Normally, the operating point voltage for obtaining the maximum power of a solar cell fluctuates by about 10% depending on the weather conditions. For example, in the case of a solar cell array with an output voltage of about 200V, the optimum operating voltage exists in the range of about 180-220V. Therefore, in order to obtain the optimum operating voltage, the above range must be investigated in detail. However, it has always been difficult to scan the entire range instantly. In Japanese Patent Application Laid-Open No. 63-57807 and Japanese Patent Application Laid-Open No. 62-85312, the search range was narrowed by using the voltage differential value of electric power and introducing a marker indicating the direction of change in the operating point voltage. In such a method, when the weather conditions fluctuate, the fluctuation of the operating point is gradually tracked, so that the magnitude of the fluctuation range must be appropriately determined from the balance between the tracking accuracy and the transient response speed. In reality, the optimum fluctuation value differs depending on the installation area, the type of solar cell, etc., so it is difficult to obtain it accurately. Further, while the above-mentioned method is sensitive, it has a problem that it is easily affected by an error of the measurement system and a sudden change in solar radiation because it uses a differential value and the like, and it is easy to overreact. On the other hand, in Japanese Patent Application Laid-Open No. 62-42213, the output of the solar cell is varied, the voltage and current are sampled, and the point where the electric power is maximized is directly found. This method is more stable than the above method, but in order to improve the tracking accuracy, it is necessary to examine a wide range in detail as described above, and the number of samplings must be increased, and the tracking accuracy and response speed must be increased. Could not be satisfied at the same time.

【0006】

An object of the present invention is to provide a novel power control device and method for solving the above-mentioned problems caused by the power control of a conventional battery power source.

【0007】

[Means for solving problems]

The above problems are the battery power supply, the power conversion means for converting the power from the battery power supply and supplying it to the load, the output value detecting means for detecting the output value of the battery power supply, and the output value of the battery power supply. The output is a power control device having an output value setting means for setting and a control means for controlling the power conversion means so that the output value of the battery power source becomes the set value of the output value setting means. The value setting means is a power control device that sets a maximum output value of a polar function approximated from a plurality of output values detected by the output value detecting means, and the battery power source is a solar cell. It is a power system. Further, the output value detecting means is an output voltage detecting means and a power control device which is an output current detecting means, and the output value setting means has m voltage values from the output voltage detecting means and the output current. Obtain m power values from m current values of the detecting means, calculate a polar function formula that approximates the power value and the voltage value from the m voltage values and the m power values, and calculate the polar function formula of the poles. It is a power control device that sets the output voltage value that maximizes the power from the function formula. Further, the similar polar function expression is a power control device which is a quadratic function, a trigonometric function, an exponential function, and a higher-order power function.

【0008】

Further, a power control device in which the number of samplings of the voltage and current is m = 3.

【0009】

Further, the battery power supply, the power conversion means for converting the power from the battery power supply and supplying it to the load, the output voltage detecting means for the battery power supply, the output current detecting means for the battery power supply, and the output of the battery power supply. A power control method including an output voltage setting means for setting a voltage and a control means for controlling a power conversion means so that the output voltage of the battery power source becomes a set value of the output voltage setting means. The step of fluctuating the battery output voltage and obtaining m power values from m voltage signals from the voltage detecting means and m current signals from the current detecting means sampled at predetermined intervals, and the above. The process of calculating the polar function formula that approximates the relationship between the m power values and the m voltage, and the voltage that maximizes the power are obtained from the polar function formula, and the voltage value is used as the output voltage set value. It is solved by the power control method having.

【0010】

[Action]

In the control device and method of the present invention, the relationship between the output voltage and the output power of a solar cell or the like (hereinafter, also referred to as a solar cell array) is approximated by a polar function to obtain the voltage at which the power is maximized. Therefore, it is possible to accurately and quickly set the voltage at which the maximum power is obtained with a narrow search range or a small number of samplings, and to extract the maximum power from the solar cell array or the like.

【0011】

FIG. 1 shows an example of a power generation system using the power control method of the present invention. The DC output of the solar cell 1 is input to the power converter 2 and supplied to the load 3.

【0012】

As the solar cell 1, a solar cell 1 using crystalline silicon, an amorphous silicon system, a compound semiconductor, or the like as a photoelectric conversion element can be used. Normally, a plurality of solar cells are combined in series and parallel to form a solar cell array, which is configured to obtain a desired voltage and current.

【0013】

Examples of the power converter 2 include a DC / DC converter using a self-extinguishing switching element such as a power transistor, a power FET, and an IGBT, and a self-excited DC / AC inverter. All of the power conversion devices can control the power flow, input / output voltage, output frequency, etc. by the ON / OFF duty ratio (so-called flow rate) and frequency of the gate pulse.

【0014】

The load 3 includes various loads such as an electric heat load and an electric motor load, but in the case of alternating current, a commercial alternating current system may be used. When the commercial AC system is a load, the system is called a "grid-connected photovoltaic power generation system", and since the power system is a load, there is no limit to the amount of power that can be input, and the maximum amount of power can be input from solar cells, etc. The control method of the present invention is particularly preferable. Similarly, a secondary battery can be used as a DC load, but in that case, it is desirable to sufficiently increase the capacity of the secondary battery and manage the state of charge of the battery. When the load is direct current, a DC / DC converter is used as the power converter 2.

【0015】

The output voltage and output current of the solar cell 1 are detected by the voltage detecting means 4 and the current detecting means 5, and the detection signals are input to the output voltage setting means 6 of the solar cell.

【0016】

The voltage detecting means 4 divides the output voltage of the solar cell by a resistor, performs A / D conversion, converts it into a digital value, and sends it to the output voltage setting means 6 and the control means 7. At this time, in order to avoid mixing of noise, it is desirable to insulate the output circuit of the solar cell and the transmission circuit of the detection signal with a photocoupler or the like that can completely insulate between the input and output. The current detecting means 5 may convert the current into a voltage by a Hall element, a standard resistor, or the like, and send the detection signal as a digital value to the voltage setting means 6 in the same manner as the voltage detecting means 4. The A / D converter used for these detection means preferably has sufficiently high speed and high accuracy, and specifically, a converter having a resolution of 10 bits or more and a sampling rate of 50 KHz or more is preferable. Such an A / D converter can configure a control system having an error of 0.1% or less and a response of 1 second or less.

【0017】

The output voltage setting means 6 performs an calculation based on the above detection signal, determines the output voltage set value, and controls the flow rate of the gate circuit of the power converter so that the solar cell output voltage becomes the set value. To do. The output voltage setting means 6 is embodied as a control microcomputer, and can include a CPU, RAM, ROM, an input / output port, a numerical calculator, and the like.

【0018】

The control means 7 of the power conversion device is a so-called gate drive circuit, and generates a gate pulse by an instantaneous value current comparison, a sine wave / triangular wave comparison method, or the like. As a result, the fluxion of the power conversion device 2 is controlled so that the output voltage of the solar cell matches the output of the output voltage setting means 6. This control means 7 can be configured with either an analog circuit or a digital circuit, but most of them have been digitized recently, and are equipped with a CPU and a DSP (Degital Signal Processor) which is a high-speed CPU.

【0019】

The digitalized control means 7 has a configuration similar to that of the output voltage setting means 6 described above, and both can be used in combination.

【0020】

Next, how the control device and method search for the operating voltage to obtain the maximum power will be described.

【0021】

The operation flowchart of the present invention is shown in FIG. In carrying out the present invention, it is advisable to first determine in advance the initial operating voltage, the voltage fluctuation range at the time of searching, the function formula used for approximation, and the number of voltage / power samplings, and store them in the ROM. The initial operating voltage is determined by the configuration of the solar cell array. For example, if 10 USSC solar cell modules UPM880 are used in series, it can be seen that the rated voltage listed in the catalog should be around 160V. Since the rated voltage is displayed for any solar cell, the initial operating voltage may be determined accordingly. The voltage fluctuation range should be 10% or less of the initial operating voltage. In the present invention, it is desirable to set it to 2% or more. If the fluctuation range is too small, the accuracy of the function approximation deteriorates due to the error of the measuring instrument, which may cause an error in the optimum operating voltage. Further, in the present invention, the tracking accuracy can be maintained higher than that of the conventional method even if a large fluctuation range is given.

【0022】

The function expression used in the present invention must be a polar function with an extremum. Examples of such a function include a power function having a degree of quadratic or higher, a trigonometric function, and the like. The number of samples must be a number that can determine the required parameters. For example, in the case of a quadratic function, three parameters are required to describe the function, and at least three points of sampling are required. The quadratic function has only one extremum and is easy to solve, so it is extremely suitable for realizing the present invention.

【0023】

Further, trigonometric functions and exponential functions also have a feature that a curve can be described with a small number of parameters, and a higher-order power function has a feature that the fit of a curve is high.

【0024】

The actual operation can be performed as follows. (1st step) Create m voltages to be sampled near the current operating voltage V. This is stored in the RAM of the voltage setting means 6. (Second step) The m voltages generated by the first step are output to the control means 7, and the power converter is actually operated. At the same time, the voltage and current detection signals are input from the input / output ports, and the voltage and current and the power calculated by the numerical calculator are stored in the RAM. (Third step) Based on the voltage and power obtained in the second step, the coefficient of the functional expression stored in the ROM in advance is obtained. (Perform function approximation) (Fourth step) Find the voltage that maximizes the power using the functional expression determined in the previous step. This is the operating point voltage for obtaining the maximum output voltage. (Fifth step) The optimum operating voltage thus obtained is output to the control means 7 of the power converter through the input / output port. Then go back to the first step.

【0025】

As described above, the present invention controls the power converter while continuously searching for the optimum operating point voltage.

【0026】

[Example]

Hereinafter, specific examples of the present invention will be described in more detail.

【0027】

(Example 1) Ten amorphous solar cell modules (trade name UPM880 manufactured by USSC) are used in series as a solar cell, and an IGBT (Insulated Gate Bipolar Transistor), which is a self-extinguishing switching element, is used as a power conversion device 2. A full bridge inverter was configured. The IGBT is a high-voltage, high-speed switching element, and is preferably used for inverters in the class of several hundred watts to several tens of kW.

【0028】

The AC output of the converter was set to 100V using a transformer and connected to a commercial AC system, which is a load.

【0029】

In addition, the voltage detecting means divides the output voltage of the solar cell array into 20: 1 resistance and digitizes it using an A / D converter with 10V full-scale 12-bit resolution, and 8 bits for the voltage setting means 6 and the control means 7. It was configured to be sent by the parallel bus of. As the current detection means, a standard resistor of 10 milliohms is inserted in series in the solar cell array circuit, the voltage across the voltage is amplified 500 times by an operational amplifier, and then an A / D converter similar to the voltage detection means is used. After converting to a 12-bit digital value, it is configured to be sent to the voltage setting means 6 by an 8-bit parallel bus.

【0030】

As the voltage setting means 6, a one-board microcomputer (Intel 8086) was used for the CPU. The board is equipped with a general-purpose parallel input / output port, a memory, a numerical calculation coprocessor for enhancing real number calculation, a serial interface, and the like, and has a configuration suitable for carrying out the present invention.

【0031】

As the control means 7, a known triangular wave comparison method PWM (pulse width modulation) was used. The carrier frequency was set to 2KHz. The control means 7 of the present invention compares the command voltage from the output voltage setting means 6 with the output voltage of the solar cell array, and the duty of the gate pulse (ON time / (ON time / (ON time /) so as to match the command voltage with the output voltage of the solar cell array. ON time + OFF time)) is changed.

【0032】

Next, the operation of searching for the operating point of this embodiment will be described.

【0033】

The solar cell array 1 was installed outdoors, and the output of the output voltage setting means 6 was set to 150V. At this time, the array output of the solar cell had a voltage of 150V, a current of 0.87A, and a power of 131W. The amount of solar radiation is about 75mW / cm²Met. This initial value may be appropriately selected from the input voltage range of the power converter, the array configuration of the solar cells to be used, and the type of solar cells.

【0034】

Next, the output of the output voltage setting means 6 was changed from 145V to 160V in 5V increments over 4 points, and the voltage, current, and power at that time were stored in the memory of the one-board microcomputer. The values at this time are shown in Table 1.

【0035】

[table 1]

<img file="JPH06348352A_D0001.tif" />【0036】

Next, the power P is expressed as a cubic expression of the voltage V as follows. It is necessary to define the number of samples and the relational expression between power and voltage in advance.

【0037】

P = aV³+ bV²+ cV + d ... (1) Next, the set of voltage and power in the above table is substituted into the above equation (1) to obtain the following quaternary simultaneous equations.

【0038】

133 = 3048625a + 21025b + 145c + d 131 = 3375000a + 22500b + 150c + d 127 = 3723875a + 24025b + 155c + d 122 = 4096000a + 25600b + 160c + d From these, the coefficients a, b, c, and d are as follows.

【0039】

a = 1.33684 × 10^-3b = -0.641615 c = 101.614 d = -5186.67 Next, find the power V that maximizes the power P from Eq. (1). Since this is the voltage V at which dp / dv = 0, it becomes as follows.

【0040】

[Outside 1]

<img file="JPH06348352A_D0002.tif" />Substitute a numerical value into Eq. (2) to obtain the voltage that takes the extreme value.

【0041】

Vmp = 143or-176V Here, since the third-order coefficient a&gt; 0, the maximum voltage is calculated to be 143V.

【0042】

In this way, the output voltage set value is determined, and the voltage set value is sent to the control means 6.

【0043】

In the next search, the voltage is changed by 5V around this value over 4 points, and the search is performed again.

【0044】

The optimum operating point voltage measured by the IV tracer immediately before the operation check of this embodiment is about 142V, and it can be seen that the present invention finds the optimum operating point with high accuracy. Further, in the present invention, as described above, even if the optimum operating point voltage is outside the search range, they can be obtained immediately. This is shown in Fig. 3.

【0045】

Furthermore, even if the optimum operating point voltage is searched discretely, such as every 5V, the optimum operating voltage value can be obtained in the same way as when sweeping continuously. In this embodiment, the relational expression between voltage and electric power is described by a cubic expression, but a more complicated one can be used. However, in that case, it is necessary to devise a method for obtaining the voltage that maximizes the power, the number of parameters in the relational expression, and a method for determining the voltage. The above calculation is performed by the microcomputer of the output voltage setting means 6 and the numerical calculation processor. As a matter of course, these operation sequences and the relational expression between voltage and power need to be stored in advance in the output voltage setting means 6 as a program.

【0046】

In this example, the tracking accuracy when continuously operated was 99.96%. The tracking accuracy was 99.90% when the search was performed with the same voltage fluctuation range as in this example using the method of JP-A-62-85312, which has the highest tracking accuracy among the conventional methods.

【0047】

The tracking accuracy is a relative value of the output voltage amount in each method when the output voltage amount in the case of continuous operation at the optimum operating point voltage is 100.

【0048】

(Example 2) Five amorphous solar cell modules (manufactured by USSC, trade name UPM880) were used in series as the solar cell, and a full bridge inverter using MOSFET was configured as the power conversion device 2. MOSFETs are high-speed switching elements and are used in inverters that convert relatively low-voltage direct current into alternating current. The AC output of the converter was set to 100V using a transformer and connected to a commercial AC system, which is a load.

【0049】

In addition, the voltage detection means divides the output voltage of the array into 10: 1 resistance and digitizes it using an A / D converter with 10V full-scale 12-bit resolution, and 8-bit parallel to the voltage setting means 6 and control means 7. It was configured to be sent by bus. As the current detection means, a standard resistor of 10 milliohms is inserted in series in the array circuit, the voltage across it is amplified 500 times by an operational amplifier, and then 12 bits are used using an A / D converter of the same type as the voltage detection means. After converting to the digital value of, it was configured to be sent to the voltage setting means 6 by an 8-bit parallel bus.

【0050】

As the voltage setting means 6, a one-board microcomputer using Motorola's 68000 was used for the CPU. The board is equipped with a general-purpose parallel input / output port, a memory, a numerical coprocessor, a serial interface, and the like, and has a configuration suitable for carrying out the present invention.

【0051】

As the control means 7, a known instantaneous value current comparison method PWM (pulse width modulation) was used. The carrier frequency was around 8KHz. The control means 7 of the present invention compares the command voltage from the voltage setting means 6 with the output voltage of the array, and changes the duty of the gate pulse so that the command voltage matches the array output voltage.

【0052】

Next, the operation of searching for the operating point of this embodiment will be described.

【0053】

The solar cell array 1 was installed outdoors, and the output of the output voltage setting means 6 was set to 70V. At this time, the array output of the solar cell had a voltage of 70V, a current of 0.95A, and a power of 66.5W. The amount of solar radiation at this time is about 70 mW / cm.²Met.

【0054】

Next, the output of the output voltage setting means 6 was changed from 50V to 70V in 10V increments over three points, and the voltage, current, and power at that time were stored in the memory of the one-board microcomputer. The values at this time are shown in Table 2.

【0055】

[Table 2]

<img file="JPH06348352A_D0003.tif" />【0056】

Next, the power P is expressed as a quadratic expression of the voltage V as follows. It is necessary to define the number of samples and the relational expression between power and voltage in advance.

【0057】

P = aV²+ bV + c ... (3) Next, the set of voltage and power in the above table is substituted into the above equation (3) to obtain the following three-dimensional simultaneous equations.

【0058】

62.4 = 3600a + 60b + c 66.5 = 4900a + 70b + c 60.8 = 6400a + 80b + c From these, the coefficients a, b, and c are as follows.

【0059】

a = -0.049 b = 6.78 c = -168 Next, find the voltage V that maximizes the power P from Eq. (3). Since this is the voltage V at which dp / dv = 0, it becomes as follows.

【0060】

Vmp = -b / 2a ... (4) Substitute a numerical value into Eq. (4) to obtain the voltage that takes the extreme value.

【0061】

Vmp = 69V In this way, the output voltage set value is determined, and the output voltage set value is sent to the control means 6.

【0062】

In the next search, the voltage is changed by 10V around this value over three points, and the search is performed again.

【0063】

In the measurement of the output characteristics of the solar cell array before confirming the operation of this embodiment, the optimum operating point voltage is about 68V, and despite the fact that the method of the present invention performs discrete searches in a very wide range. The optimum operating point can be found with the same accuracy as when sweeping continuously. This is shown in Fig. 4.

【0064】

In this embodiment, since the relational expression between voltage and electric power is described by a quadratic formula, the coefficient calculation and the extreme value calculation of the relational expression are remarkably easy, and the burden on the program of the voltage output setting means 6 can be reduced. Therefore, it is also more advantageous than the previous embodiment in terms of calculation speed.

【0065】

In this example, the tracking accuracy when continuously operated was 99.0%. The tracking accuracy was 96.0% when the search was performed with the same voltage fluctuation range as in this example by the method of JP-A-62-85312. As described above, the present invention can track the optimum operating point with high accuracy even when the voltage fluctuation range for searching is large.

【0066】

(Example 3) Twenty amorphous solar cell modules (manufactured by USSC, trade name UPM880) as solar cells were used in series, and a motor inverter using a power transistor was used as the power conversion device 2. The conversion device has a built-in gate control circuit, and its AC output voltage and frequency can be changed by inputting an analog voltage. The AC output of the converter was connected to a well pump (3-phase 200V, 500VA), which is a load.

【0067】

In addition, the voltage detection means divides the output voltage of the array to 40: 1, digitizes it using an A / D converter with 10V full-scale 12-bit resolution, and sends it to voltage setting 6 via an 8-bit parallel bus. And said. As the current detection means, a standard resistor of 10 milliohms is inserted in series in the array circuit, the voltage across it is amplified 500 times by an operational amplifier, and then 12 bits are used using an A / D converter of the same type as the voltage detection means. After converting to the digital value of, it was configured to be sent to the voltage setting means 6 by an 8-bit parallel bus.

【0068】

As the voltage setting means 6, a one-board microcomputer using Motorola's 68000 was used for the CPU. The board is equipped with a general-purpose parallel input / output port, a memory, a numerical coprocessor, a serial interface, a D / A, and the like, and has a configuration suitable for carrying out the present invention.

【0069】

In this embodiment, since the gate control circuit is built in the inverter, the output voltage setting means 6 is also provided with the function of input voltage control. That is, the output frequency of the motor inverter is adjusted so that the input voltage becomes the set value. This command frequency is sent to the motor inverter as an analog voltage using a D / A converter.

【0070】

Next, the operation of searching for the operating point of this embodiment will be described.

【0071】

The solar cell array was installed outdoors, and the output of the output voltage setting means 6 was set to 280V. At this time, the array output of the solar cell had a voltage of 280V, a current of 1.15A, and a power of 322W. In addition, the amount of solar radiation is 94mW / zm²Met.

【0072】

Next, the output of the output voltage setting means 6 was swung from 260V to 300V in 20V increments at three points, and the voltage, current, and power at that time were stored in the memory of the one-board microcomputer. The values at this time are shown in Table 3.

【0073】

[Table 3]

<img file="JPH06348352A_D0004.tif" />【0074】

Next, as in the second embodiment, the electric power P is expressed as a quadratic equation of the voltage V as follows.

【0075】

P = aV²+ bV + c ... (5) Next, the set of voltage and power in the above table is substituted into the above equation (5) to obtain the following three-dimensional simultaneous equations.

【0076】

270 = 67600a + 260b + c 322 = 78400a + 280b + c 288 = 90000a + 300b + c From these, the coefficients a, b, and c are as follows.

【0077】

a = -0.1825 b = 101.15 c = -13692 Next, find the voltage V that maximizes the power P from Eq. (3). Since this is the voltage V at which dp / dv = 0, it becomes as follows.

【0078】

Vmp = -b / 2a ... (4) Substitute a numerical value into Eq. (4) to obtain the voltage that takes the extreme value.

【0079】

Vmp = 277V In this way, the output voltage set value is determined, and the voltage set value is sent to the control means 6.

【0080】

In the next search, the voltage is changed by 20V around this value over three points, and the search is performed again.

【0081】

In the measurement of the output characteristics of the array before this implementation, the optimum operating point voltage is about 276V, and despite the fact that the method of the present invention performs discrete searches over a very wide range, it is accurate and continuous. You can find the optimum operating point as if you swept to.

【0082】

In this way, there is no problem even if this method is applied to a stand-alone power supply. The same applies when a DC / DC converter is used as the power converter.

【0083】

[Effect of the invention]

As described above, the present invention (1) Even if the optimum operating point is outside the search area, the optimum operating point can be found with high accuracy in a single search.

【0084】

(2) Even if the search is performed discretely with a fixed step size, the optimum operating point can be found in the same way as when sweeping continuously.

【0085】

(3) By increasing the search step width, the optimum operating point can be found accurately over a wide range with a small number of sampling points.

【0086】

(4) In particular, if a quadratic function is used as the relational expression between power and voltage, the optimum operating point can be calculated at extremely high speed. Has an effect.

【0087】

The present invention having such excellent features has extremely high industrial utility value, and is particularly useful for a power generation system connected to a commercial system.

[Simple explanation of drawings]

[Figure 1]

This is an example of a photovoltaic power generation system using the control device of the present invention.

[Figure 2]

This is another example of a photovoltaic power generation system using the control device of the present invention.

[Fig. 3]

This is an example of searching for the optimum operating point of the photovoltaic power generation system using the control device of the present invention.

[Fig. 4]

This is another example of searching for the optimum operating point of a photovoltaic power generation system using the control device of the present invention.

[Fig. 5]

This is an example of a flowchart showing the operation of the present invention.

[Explanation of symbols]

1 Solar cell array 2 Power converter 3 load 4 Voltage detection means 5 Current detection means 6 Output voltage setting means 7 Control means V_pv^* Solar cell array output voltage command value f^* Inverter output frequency command value V1, V2, V3, V4 Solar array operating point voltage V_opt Optimal operating point voltage for solar array