JP2000270592A - Rotation controller of ac motor using solar cell as power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller which causes an AC motor which uses a solar cell as a power supply for rotation to rotate with maximum energy efficiency, without using a battery which is normally used for the stabilization of power. SOLUTION: A controller for an AC motor which uses a solar cell as a power supply for rotation supplies a DC power generated by the solar cell to the AC motor via an inverter 20, which is a DC/AC converting means. Furthermore, when an AC frequency control signal is supplied to the inverter 20 from the controller by using a relation that the load value of the AC motor as the load of the solar cell is changed by the change of the frequency of the driving power supply, the AC frequency control signal which makes the generated power of the solar cell maximum is supplied to make the AC motor always rotate with maximum efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for obtaining an energy-saving effect by most efficiently using power generated by a solar cell during a fine daytime as a power source of an AC motor.

[0002]

2. Description of the Related Art When an AC motor is rotated using a solar cell as a power source, it is possible to rotate the AC motor by converting the power generated by the solar cell into AC and using it. There is a characteristic that the generated power fluctuates drastically due to a change in the altitude of the sun or a change in the weather, and is not suitable as a power source of an AC motor requiring a constant power supply. In order to solve this, a method of stabilizing the power by temporarily charging the storage battery with the power generated by the solar cell and supplying the power to the AC motor has been generally used. There is a problem that a large-capacity storage battery is required, and maintenance and maintenance of the storage battery require a great deal of labor and cost.

[0003] More specifically, although it varies depending on the load, the rotation speed of the AC motor and the load amount are generally related, and for example, the output of the AC motor that rotates the pump or the screw is proportional to the cube of the input frequency. is there. FIG.
Is an example of a graph showing a relationship between an AC input frequency and an output when a liquid diffuser (also referred to as an impeller) is rotated in water by an AC motor, and the output of the AC motor has a value proportional to the cube of the frequency. Become. That is, the output of the AC motor is uniquely determined for the set AC input frequency, and the minimum input power required to obtain the output is naturally determined. For this reason, when a solar cell is used as the power source of the AC motor, if the generated power of the solar cell does not reach the minimum required amount due to insufficient sunlight, the AC motor cannot continue to rotate stably. Will stop. Specifically, although it depends on the characteristics of the AC motor and the inverter, the AC motor stops when the power is insufficient by several percent to 10 percent of the required amount. This is very disadvantageous in practical use of the electric motor. Further, during this time, although a certain amount of power is generated, all the generated power is discarded, which is a waste of energy. Conversely, even when the solar cell generates more power than necessary when the weather is fine, all the power above the minimum required amount is discarded, which is also a waste of energy. In order to solve these problems, it has been general to use a power stabilization method using a storage battery as described above.

[0004]

The present invention relates to a facility for rotating an AC motor using a solar cell as a power source,
The object of the present invention is to overcome the above-mentioned problems by eliminating the need for a storage battery, and to reduce the size and cost of equipment, as compared with the conventional power stabilization method using a storage battery.

[0005]

Means for Solving the Problems In order to solve the above problems, the present invention is configured as follows. (1) A control device using a solar cell 18 as a power source for rotating the AC motor 10, wherein the DC power generated by the solar cell is converted to an AC power through an inverter 20 as an inverter. The AC motor, which is a load of the solar cell, is configured to supply the AC frequency control signal to the inverter from the controller 24 by changing the frequency of the driving AC power supply. The AC motor is always rotated at the maximum efficiency by supplying an AC frequency control signal that maximizes the power generated by the solar cell in relation to the change in the load amount. (Part 2) A control device using a solar cell 18 as a power source for rotating the AC motor 10, wherein the DC power generated by the solar cell is converted to an AC power through an inverter 20 as an inverter. The AC motor, which is a load of the solar cell, is configured to supply the AC frequency control signal to the inverter from the controller 24 by changing the frequency of the driving AC power supply. In the relationship in which the amount of load changes, the power generated by the solar cell is configured to supply an AC frequency control signal such that the power becomes the maximum power, so that the AC motor always rotates at the maximum efficiency. In addition, the AC motor rotates at the required rotation speed when it is necessary to secure a certain rotation speed or more in practical use of the motor. Power is set in the controller, and when the illuminance falls below this set value, the switch 40 is opened by a signal from the controller, and power is supplied from the commercial power supply 30. When the output of the illuminometer exceeds the set value, the switch is closed by a signal from the controller, and power is supplied from the solar cell, so that the AC motor is always constant. It is configured to secure the above rotation speed.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention controls the rotation of an AC motor 10 using electric power generated by a solar cell 18 as a power source. As a specific control method, by utilizing the characteristics of the solar cell as described later, the fluctuation of the generated power of the solar cell, that is, the fluctuation of the input power of the AC motor, This is to automatically control the AC frequency of the inverter 20 so as to rotate with efficiency. In that case, the power generated by the solar cell is directly converted to AC without the intervention of a storage battery,
Supply to AC motor.

FIG. 6 is a general graph showing a relationship between generated power and load of a solar cell that generates power under a certain constant illuminance. From this figure, for each illuminance, there is a peak of the generated power, and there is a load for generating the peak power, that is, an optimal load, and the connected load is too large or too small. However, it can be seen that the power generation efficiency is reduced. From this, in order to obtain the most efficient power from the solar cell under the illuminance that changes every moment depending on the weather conditions, it is necessary to adjust the load according to the illuminance at that time so that the load becomes the optimal load That is good.

FIG. 4 is a curve showing the relationship between the generated voltage and the current of the solar cell. The description will be made according to this. In general, as a characteristic of a solar cell, when power is generated under a certain amount of sunlight, the load behaves almost as a constant current source when the resistance is low, but when the resistance gradually increases and reaches a certain voltage value The current suddenly decreases, and this time becomes almost a constant voltage source. As the resistance further increases, the current decreases and approaches an open point. Here, the transition point from the constant current to the constant voltage is the product of the current value and the voltage value, that is, the point where the generated power of the solar cell takes the maximum value, and the power value at this point and the voltage are divided by the current. The value, ie, the load, corresponds to the maximum power and the optimum load in FIG. That is, the generated voltage and current of the solar cell are:
If the load is controlled so that the amount of sunshine at that time becomes a value at the transition point, the maximum power can be extracted. A further detailed characteristic of the solar cell is that the voltage value at the transition point is substantially constant regardless of the level of the illuminance.
That is, the solar cell has a unique voltage value from which the maximum power can be extracted. If the value is used as an optimum voltage value while adjusting the load so that the output voltage of the solar cell becomes the optimum voltage value, power can always be obtained most efficiently at any illuminance.

Further, when the AC motor is used as a load of the solar cell, the output of the AC motor has a value proportional to the cube of the AC input frequency, as described in “0003”. That is, when the AC motor is used as the load of the solar cell, the load amount can be adjusted to an arbitrary value by changing the input frequency.

In the present invention, the frequency is adjusted by supplying the AC frequency setting signal 28 from the controller 40 to the inverter 20 that converts the output power of the solar cell into AC. In that case, the optimum voltage value described in the above “0008” is calculated in advance based on the characteristics of the solar cells to be used and the number of combinations thereof, and is set in the controller. Then, when actually performing the control, the controller compares the solar cell power generation voltage 22 with the optimum voltage value, and adjusts the AC frequency setting signal so that the solar cell power generation voltage matches the optimum voltage value. To adjust. The detailed control procedure is as follows. 1. The voltage value of the solar cell when the load is connected (when the AC motor is rotating) is detected. 2. If the voltage value is higher than the optimal voltage value set in the controller, a signal for increasing the AC frequency is output to the inverter to increase the rotation speed of the AC motor, thereby reducing the load (power consumption). To increase. 3. If the voltage value is the optimum voltage value, the frequency is not increased or decreased. 4. If the voltage value is lower than the optimum voltage value, a signal for reducing the AC frequency is output to the inverter. That is, the load (power consumption) is reduced by reducing the rotation speed of the AC motor. (Return to 1.) The above control is performed. In the embodiments described below,
As the optimum voltage value, 330 V, the increase / decrease value of the input frequency per loop was set to 1.0 Hz.

In addition, in the case where it is necessary to always maintain a certain number of rotations or more in actual use of the AC motor, stable control can be performed by using the commercial power supply 30 as a power source together. Can be realized. That is,
When the power generated by the solar cell 18 decreases due to insufficient sunshine and the required rotation speed cannot be maintained, the switch 40 is opened by an output signal from the controller 24, the switch is switched to the commercial power supply, and the sunshine is further increased. Is restored, and when the required number of revolutions can be maintained, the switch is closed again, and control for switching to the solar cell is automatically performed. Further, the illuminometer 34 is used to determine the switching time of the power source. In general, the power that can be extracted from the solar cell at the maximum efficiency is proportional to the illuminance, so that the controller can calculate the power that can be output from the solar cell from the output of the illuminometer. For details on switching power, see “0019” to “0” in the embodiment.
021 ”.

[0012]

Embodiment In the present embodiment, the present invention is used for controlling the rotation of an AC motor used in a liquid diffusion device. As a form of the liquid diffusion device, the liquid diffusion device includes a liquid diffuser 12 installed in water driven by the rotational force of an AC motor 10, and disperses the liquid in the upper layer near the water surface and the water in the lower layer near the bottom surface. A liquid diffuser for reducing the temperature difference between the water in the upper layer and the water in the lower layer by suctioning the liquid with each of the liquid diffusers, wherein the rotating blades of the liquid diffuser rotate. Thereby, water is sucked from the lower suction port 14 of the liquid diffusion device and water is also sucked from the upper suction port 16 of the liquid diffusion device, and the water is discharged from the liquid diffuser in a substantially horizontal direction. It is mainly used for the purpose of red tide prevention and water purification in fish farming facilities and the like.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but this is, of course, for explanation, and the present invention is not limited to this embodiment. FIG. 1 is a flowchart of a preferred embodiment of the present invention. In the figure, an AC motor 10 is for driving the liquid diffusion device, and is a three-phase AC, 15 kW,
The one with 800 rpm / 60 Hz was used.

The solar cell 18 used in the present embodiment includes
When the power generation capacity per unit is 25 ° C. ambient temperature and 1 kW / square meter of sunlight, the normal operating voltage is 22 V.
(Open voltage 27.3 V), normal operation current 3.36 A (short circuit current 3.75 A), and maximum output 74 W were used.

In the present embodiment, 15 units of this solar cell are connected in series to form one block, and 11 blocks are further connected in parallel to use a total of 165 units of solar cells as one set. did. The maximum output that can be generated by the solar cell thus configured is 22 V
× 15 = 330V, 3.36A × 11 = 37A, that is, the total power generation is about 12.2 kW.

The inverter 20 has a rated output of three phases 20.
A rated output of 15 kW at 0 V and an AC frequency of 60 Hz was used.

A CPU was used as an arithmetic element for the controller 24. Therefore, the instruction of the set value to the control unit and the like are all performed by the program software. In this embodiment, a commercially available sequence controller is used as the controller 24.

Here, FIG. 1 will be described in more detail as follows. The power generated by solar cells is
It is input to the DC input of the inverter via the diode 32 and the switch 40. The controller 24 calculates the difference between the output voltage of the solar cell and the optimal voltage, and from the result, generates a signal that increases the frequency if the voltage is higher than the optimal voltage,
If the voltage is low, a signal that reduces the frequency is input to the inverter. Although the optimum voltage is determined by the characteristics and combination of the solar cells used, it is set to 330 V in this embodiment.

In this embodiment, it is necessary to secure a certain value or more as the rotation speed of the AC motor. This is because a sufficient red tide prevention effect cannot be obtained if the discharge rate is less than about 1.4 tons per second in the water area where the liquid diffusion device is installed. In the present embodiment, when the frequency of the AC motor that ensures the impeller discharge rate of 1.4 tons per second cannot be maintained due to the lack of sunlight, the power is supplied from the commercial power supply 30 to always maintain a constant level or more. The discharge amount can be secured.

A commercial power supply 30 (three-phase AC 200 V), which is an AC power supply, is rectified by a diode 32 ′
283 V and supplied to the inverter 20. Here, the diode 32 and the diode 32 'constitute a non-contact switch in which both of these diodes constitute one set, and one of the voltages applied to both is higher than any one of the voltages. Only the diode can be energized, and the switching is performed instantaneously. The power is switched by controlling the applied voltages of these diodes. At this time, a voltage difference is generated between the voltages applied to both diodes by opening and closing the switch 40 controlled by an output signal from the controller. First, when the operation using the solar cell 18 is performed, the switch is closed. During operation with the solar cell, the output voltage of the solar cell is controlled so as to be in the vicinity of DC 330 V. Therefore, power is not supplied from the DC 283 V commercial power supply, and operation using only the solar cell as a power source is performed. . Next, when operating with commercial power, the switch is opened to cut off the power supply from the solar cell. This allows
The voltage on the diode 32 side becomes 0 V, and power is supplied from the commercial power supply of DC 283 V.

[0021] The rotation speed of the impeller, that is, the input frequency of the AC motor, for ensuring a discharge rate of 1.4 tons per second is calculated in advance from the characteristics of the impeller. (In this embodiment, about 50 Hz, AC motor output about 7 kW) From the power generation characteristics of the solar cell, the required illuminance, that is, the discharge rate of 1.4 per second.
The illuminance for securing the tons is calculated and set in advance in the controller as the power source switching illuminance. (In this embodiment, 0.
(6 kW / square meter) During operation of the present apparatus, the output from the illuminometer 34 is constantly referred to by the controller 24. At this time, when the illuminance becomes less than the above-described power source switching illuminance, the power source is switched to the commercial power supply 30 by opening the switch 40 by an output signal from the controller. Next, when the illuminance rises and recovers to the power switching illuminance,
The switch is closed, and operation with the solar cell 18 is performed.

In the present embodiment, since a commercial power supply was available, a commercial power supply was used as a power supply for the control device. However, in a facility that does not use a commercial power supply, the power generated by the solar battery, which is a power supply, is used. A part of the storage battery 44 is charged via the charger 42, and the power charged in the storage battery is used as a power source for the control device. The charger is
It has a PWM converter inside to reduce the solar cell output voltage to the storage battery voltage. Further, the voltage of the storage battery is constantly monitored, and the duty ratio in the PWM converter is controlled so that the storage battery is not overcharged. In addition, if the power consumption of the control device is sufficiently small compared to the power generated by the solar cell, it is not necessary to interpose a storage battery. Furthermore, even when a storage battery is used, the stabilization of the power described in the above “0002” is compared with a large-capacity storage battery for the purpose.
It has a very small capacity and requires little labor and cost for maintenance.

FIG. 2 is a graph in which the illuminance (kW / square meter), the generated voltage, the generated power, and the discharge amount (ton / second) are recorded at every hour from 4:00 in the morning to 20:00 at night in the present embodiment. is there. (Conducted month: mid-June, weather: sunny)
Of course, the devices, equipment, and the like for taking these data are not shown. The operation and effect of the present invention will be described with reference to the graph of FIG. Until about 8:30 when the illumination is not enough,
Since the operation is performed by the commercial power supply 30, the solar cell 1
Reference numeral 8 denotes a no-load state, in which the voltage becomes an open-circuit voltage, and the power generation voltage of the solar cell rapidly rises from about 5:00, and rises to about 400 V at half past six. At around 8:30 the illuminance is 0.
Since the power reaches 6 kW / sq.m. And the operation is switched to the operation using the solar cell, the generated voltage becomes constant at the optimum voltage value of 330 V until about 15:30. Since the inverter frequency is fixed during operation with commercial power,
Although it is constant at 1.4 tons / sec, when the operation is switched to the operation using the solar cell, the discharge amount also increases as the illuminance increases,
It peaks at about noon and reaches about 1.6 tons / sec. Thereafter, both the illuminance and the discharge amount gradually decrease, and at about 15:30, the illuminance falls below 0.6 kW / sq.m.

[Brief description of the drawings]

FIG. 1 is a flowchart of a preferred embodiment of the present invention.

FIG. 2 is a graph showing data recorded every hour from 4:00 to 20:00 in the present embodiment.

FIG. 3 is a schematic diagram illustrating an outer shape of a liquid diffusion device used in the present embodiment. The floating base and the solar cell are not shown.

FIG. 4 is a graph of a preferred example showing voltage-current characteristics of a general solar cell.

FIG. 5 is a graph of a preferred example showing a relationship between an AC input frequency and an output when an impeller is rotated underwater by an AC motor.

FIG. 6 is a graph of a preferred example showing a relationship between generated power and a load amount of a solar cell that generates power under a certain illuminance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 AC motor 12 Liquid diffuser 14 Lower suction port 16 Upper suction port 18 Solar cell 20 Inverter 22 Solar cell power generation voltage 24 Controller 28 Frequency control signal 30 Commercial power supply 32, 32 'Diode 34 Illuminometer 40 Switch 42 Charger 44 Storage battery 48 Water surface 50 Sea bottom 52 Cooling 54 Anchor

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) LL49 LL60

Claims (2)

[Claims] 1. A control device using a solar cell (18) as a power source for rotating an AC motor (10),
The DC power generated by the solar cell is configured to be supplied to the AC motor via an inverter (20), which is a means for converting to an AC power supply, and an AC frequency control signal is transmitted from a controller (24) to the AC motor. When supplying to the inverter, the AC motor, which is the load of the solar cell, changes the load amount by changing the frequency of the driving AC power supply, so that the power generated by the solar cell becomes the maximum power. A rotation control device characterized in that the AC motor is configured to always rotate at the maximum efficiency by supplying a stable AC frequency control signal. 2. A control device using a solar cell (18) as a power source for rotating an AC motor (10),
The DC power generated by the solar cell is configured to be supplied to the AC motor via an inverter (20), which is a means for converting to an AC power supply, and an AC frequency control signal is transmitted from a controller (24) to the AC motor. When supplying to the inverter, the AC motor, which is the load of the solar cell, changes the load amount by changing the frequency of the driving AC power supply, so that the power generated by the solar cell becomes the maximum power. A rotation control device characterized in that the AC motor always rotates at the maximum efficiency by supplying an AC frequency control signal. If it is necessary to secure, the controller sets the illuminance at which the solar cell can generate power for the AC motor to rotate at the required rotation speed, and the illuminance falls below this set value. In this case, the switch (40) is opened by a signal from the controller, power is supplied from the commercial power supply (30), and if the output of the illuminometer exceeds this set value, the controller (40) is opened. A rotation control device characterized in that the switch is closed by a signal from the controller and power is supplied from the solar cell so that the AC motor always keeps a certain number of rotations or more.