JPS6348163A - Controlling apparatus for solar pump system - Google Patents

Abstract

PURPOSE:To prevent of a burning motor due to idle running by detecting an output of solar battery as compared with an operating frequency of variable frequency inverter being less than a given value, so as to stop an operation of the variable frequency inverter. CONSTITUTION:A solar pump system is composed of a solar battery 1, a reverse-current blocking diode 2, a capacitor 3, a variable frequency inverter 4, a pump motor 5 consisting of an AC motor and a pump 6 for said system. Also, a control unit for said solar pump system is composed of a resistance type potential divider 7 for solar battery voltage, a voltage setter 8, a voltage controller 9, a V/F converter 10, a PWM circuit 11, an output voltage instructor 12, an output current sensor 13 and a decision means 17. Said decision means 17 is composed of a function generator 14 outputting a predetermined value for a frequency signal and a comparison and decision device 15 comparing an output current of the solar battery 1 with an output of the function generator 14 for instructing a drive or stop of the inverter, so as to prevent the pump motor 5 from running at an excessive speed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to a solar pump system in which the output of a solar cell is supplied to a pump motor via a variable frequency inverter to drive the pump motor. This invention relates to a control device that automatically prevents idling in the evening.

[Conventional technology]

FIG. 4 is a configuration diagram showing a conventional solar pump system control device disclosed in, for example, Japanese Patent Application Laid-Open No. 56-132174. a reverse current prevention diode connected in series to the battery (1);
(3) is a capacitor, (4) is a variable frequency inverter connected in parallel with this capacitor (3), (5) is a pump motor consisting of an AC motor connected to this variable frequency inverter (4), and (6) is a This pump motor (5)l
The pump operated by this, (7) consists of voltage dividing resistors (7a) and (7b), a resistive voltage divider for detecting the output voltage of the solar cell (1), (8) a voltage setting device, (9 ) is the voltage from this voltage setter (8) and the resistive voltage divider (7
) is input, and the voltage controller (10) controls the detected voltage to be equal to the set voltage f.
9) for generating a control signal that determines the operating frequency of the variable frequency inverter (4) in response to the output of the converter (H); (H) generates pulses that determine the conduction period and frequency of the variable frequency inverter (4); PWM circuit, (
tZ) is the output of the voltage wJ controller (9), that is, depending on the operating frequency of the variable frequency inverter (4), the pump motor body)
This is an output voltage command device that generates the optimal inverter output voltage for the

FIG. 5 shows the relationship between the voltage of the solar cell (1) and the output (P) using solar radiation (Ll) to (L5) as parameters ζ.

The conventional solar pump system control device is configured as described above, and its operation will be explained below. In FIG. 4, first, the operating frequency of the variable frequency inverter (4) is changed so that the output voltage of the solar cell (1) becomes equal to the voltage preset by the voltage setting device (8), and the operating frequency of the variable frequency inverter (4) is The rotational speed, that is, the power consumption is adjusted. As a result, the solar cell (1) is always connected to the voltage setting device (
8), and the output at that time is supplied to the pump motor (5) via the variable frequency inverter (4). In this case, the solar radiation changes as shown in Figure 5. However, since the maximum output operating point voltage is small, this value t
With this setting, the solar cell will be operated near the optimum point.

[Problem that the invention seeks to solve]

Since the conventional solar pump system control device is configured as described above, for example, when the water level drops due to a drought, the pump may run idly. In this case, when the solar radiation is high, the motor reaches an abnormal rotation speed, and when the solar radiation is low, even if the rotation speed is not abnormal, there is a problem that the motor burns to B4 due to cooling.

For this reason, in the conventional solar pump system shown in FIG. 4, it was necessary to separately provide a water level sensor and take measures to stop the variable frequency inverter when the water level drops.

In this case, there were also problems with reliability, such as maintenance of the water level sensor.

This invention was made to solve the above-mentioned problems, and its purpose is to provide a control device for a solar pump system that can prevent motor damage due to idling without the need for a special external sensor. do.

[Means for solving problems]

The control device for a solar pump system according to the present invention has a determination means for determining whether the output level of the solar cell has become equal to or less than a predetermined value at the output frequency of the variable frequency inverter at that time, This configuration is designed to stop the frequency inverter.

[Effect]

FaIJ11 of the solar pump system based on this invention
In the device, the output of the solar cells changes depending on the amount of solar radiation, but by changing the frequency of the variable frequency inverter, that is, changing the rotation speed of the pump motor, the amount of load can be adjusted to a value commensurate with the output of the solar cells. It is KIIJI.

In the above-mentioned state, when the water runs out and the pump motor idles, the load suddenly becomes lighter, and for the same power, the frequency of the variable frequency inverter increases rapidly. For this reason, idling is detected when the output of the solar cells relative to the operating frequency of the variable frequency inverter falls below a predetermined value.
This stops the operation of the variable frequency inverter.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram showing a control device for a solar pump system according to the present invention. In the figure, (1) is a solar cell, and (2) is a backflow prevention diode connected in series to the solar cell (1). , (6) is a capacitor, (4) is a variable frequency inverter connected in parallel with this capacitor (6),
(5) is a pump motor consisting of an AC motor connected to this variable frequency inverter (4), (6) is a pump operated by this pump motor (5), (7) is a voltage dividing resistor (7a) and ( 7b) is a resistive voltage divider for detecting the output voltage of the solar cell (1), (8) is a voltage setting device, and (9) is a voltage setting device (8) for detecting the output voltage of the solar cell (1). A voltage controller (10) receives the divided voltage from (7) and controls the detected voltage equal to the set voltage, and (10) adjusts the operating frequency of the variable frequency inverter (4) in response to the output of the voltage controller (9). (11) is a PWM circuit that generates pulses that determine the conduction period and frequency of the variable frequency inverter (4), (12) is the output of the voltage controller (9), i.e. , is an output voltage command device that generates an optimal inverter output voltage for the pump motor (5) according to the operating frequency of the variable frequency inverter (4). (13) is the output current detector of the solar cell (1), (14) is a function generator that receives the inverter operating frequency signal and outputs a predetermined value for that value, and (15) is the output current It is a comparison/judgment device that compares the output current of the solar cell (1) detected by the detector (16) with the output of the function generator (1) and instructs the inverter to drive or stop. (14) and the comparison/determination device (15) constitute a determination means (17).

The control device for a solar pump system according to the present invention is configured as described above, and its operation will be explained below. Needless to say, the power required for the load of the pump (6) varies depending on the system depending on the output frequency of the variable frequency inverter (4), that is, the rotation speed of the pump motor (5), but in most cases it is as shown in Figure 2. ■~2~ of rotation speed as shown in @
It exhibits a characteristic proportional to the sixth power. On the other hand, in the embodiment shown in FIG. 1, under normal conditions, as in the conventional embodiment shown in FIG.
Since the frequency of the variable frequency inverter (4) is controlled so that the output voltage of the solar cell (1) is constant (for example, Vop shown in Figure 5), the amount of solar radiation is Ll as shown in Figure 5.
If it changes from Pl to Ll, the output of the solar cell will change from Pl to P2
Changes to Now, assuming that the pump load characteristics are as shown in FIG. 2, the inverter frequency changes from fl to 2 at this time, and the power generated by the solar cell (1) and the power consumed by the pump are balanced.

In this state, if idling occurs, the load suddenly becomes lighter and the characteristic shifts to (2) in FIG. As a result, the inverter frequency goes out of control and reaches fl2, leading to a situation where the pump motor and the like may be damaged. Also, as shown in Figure 5, if the inverter idles when the amount of solar radiation is low (L5), the output of the solar cell will be as low as P5, and the inverter frequency will change from f5 to fz5. Although it may be within the operating frequency range, since it is water, the cooling capacity of the pump motor (5) is low and this state cannot be maintained. However, in the embodiment of the present invention, if the actual output current of the solar cell (1) is detected by the current detector (15), the output voltage is constant, so the output current can be regarded as electric power. . On the other hand, in the function generator (14),
For the inverter frequency at that time, the value shown by the characteristic ■ in Figure 2 is output, so in the comparison/judgment unit (15), the output (current) of the solar cell (1) described above is determined by the function generator (
If the output is less than 1, it is determined that the motor is idling, and an inverter stop signal (15a) is generated to stop the inverter drive firing pulse (11a) from the PWM circuit (11). As a result, the variable frequency inverter (4) stops and
The rotation speed of the pump motor (5) can be stopped without running out of control, and damage or burnout due to idling can be prevented.

Furthermore, as is clear from Fig. 2, the characteristics (■) provided by the function generator (14) can be easily set because there is usually a large difference between the normal operating characteristics (■~@) and the characteristics (■) during idling. I can do it.

In the above embodiment, the function generator (14) and the comparison/determination device (15) are provided separately, but these can be used to directly generate a stop signal for the variable frequency inverter by calculating a function formula for the frequency using a microcomputer or the like. It goes without saying that it is also possible to generate a signal or to read and judge data stored in memory according to the frequency.

In addition, in the embodiment shown in Fig. 1, the frequency of the variable frequency inverter (4) during normal operation is controlled so that the output voltage of the solar cell (1) is constant t, so that it does not change when the temperature changes. ,
During low solar radiation, the operating point of the solar cell deviates from the maximum output point, so instead of using the voltage setting device (8), the output voltage and current values of the solar cell (1) are used as shown in Figure 3. A configuration using a Pmax control circuit (16) that performs compensation, or a configuration in which the voltage controller (9) is omitted and the Pmax control circuit (16) is used.
The present invention can also be applied to the conventional Pma, xl-racking control system in which the frequency command No. 16 of the variable frequency inverter (4) is directly generated from the frequency command No. 16) due to the similar structural effect. In addition, in this case, the current detector (16
) can be shared and can be applied more easily.

〔Effect of the invention〕

According to the present invention, when the output of a solar cell is supplied to a pump motor via a variable frequency inverter, the output power or current of the solar cell is detected, and the value is set at the inverter station at that time. Since the variable frequency inverter is stopped when the determination means determines that the wave number has fallen below a predetermined value, it is possible to easily and accurately detect the idling of the pump motor without installing an external water level detector ring. Damage and burnout can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a control device for a solar pump system according to an embodiment of the present invention, FIG. 2 is an operational characteristic diagram of the solar pump system, and FIG. 3 is a block diagram showing a control device for a solar pump system according to an embodiment of the present invention. A block diagram showing an embodiment of
FIG. 4 is a block diagram showing a control device for a conventional solar pump system, and FIG. M5 is a diagram showing operating characteristics of a solar cell. (1) is a solar cell, (4) is a variable frequency inverter, (
5) is the pump motor, (6) is the pump, body) is the voltage setting device, (9) is the voltage controller, (15) is the output current detector,
(1 is the function generation part, (15) is the comparison judgment part, (16)
is a PmaX control circuit, and (17) is a determination means. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Rei 1 figure (13) t ↓ Caustic current detection inspection 2 figure 3 figure 3 leakage 1 figure 40 face 5 figure 11 ~ Co-1 L''13'v9 ■ ゛Pmaxill hanging circuit

Claims (6)

[Claims] (1) In a control device for a solar pump system that supplies the output of a solar cell to a pump motor via a variable frequency inverter to drive the pump motor, the output level of the solar cell at that time is determined by the output level of the variable frequency inverter. A control device for a solar pump system, comprising a determining means for determining whether the output frequency has become below a predetermined value, and stopping the variable frequency inverter. (2) The control device for a solar pump system according to claim 1, wherein the output level uses an output current. (3) The determining means includes a function generating section that receives an inverter operating frequency signal and outputs a predetermined value in response to the input, an output from an output current detector that detects the output current of the solar cell, and an output from the output current detector that detects the output current of the solar cell. 3. The control device for a solar pump system according to claim 1, further comprising a comparison/judgment section for comparing the output from the function generation section. (4) The control device for a solar pump system according to claim 3, wherein the function generation section and the comparison/judgment section are integrally constituted by a microcomputer. (5) The function generating section is configured to receive a divided voltage of the output voltage of the solar cell and a voltage from a voltage setting device as set forth in claim 3 or 4. Control device for solar pump system. (6) The frequency command signal of the variable frequency inverter is Pma
5. A control device for a solar pump system according to any one of claims 1 to 4, wherein the control device is configured to obtain the power from an x control circuit.