JP2548913B2 - Pump device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pump device that, when a pump operated by photovoltaic power generation runs idle due to a drop in water level, detects this idle operation and stops the pump. is there.

[Prior art]

In recent years, a pump device using a solar power generation device has been spotlighted for irrigation in a desert area, for example. In particular, in such a zone, unmanned operation is required due to maintenance reasons, and it is required to operate in an unmanned state for a long time without failure. In a pump operated by such a solar power generation device, when the pump runs idle at high speed due to a decrease in water level, an accident such as burnout of the pump shaft may occur, or the power distributed by the solar cell may be distributed. There are problems such as wasteful consumption.

As a countermeasure against this, there is a conventional method, for example, Japanese Patent Laid-Open No. 57-1793.
As shown in No. 85, there was a pump control device that automatically provided a water level detection means such as a water level sensor to automatically stop the pump when the water level fell below a predetermined level. In some cases, the pump is stopped when the flow rate from the pump falls below a predetermined amount by a flow rate sensor that detects the flow rate from the pump, and the pump is stopped.

[Problems to be solved by the invention]

However, as described above, in a device that detects a pump idle operation using a water level sensor or a flow rate sensor, the water level sensor, flow rate sensor, etc. must be installed in a location where water exists, so not only does the entire device become a large scale. However, there is a problem that maintenance and inspection of these sensors are accompanied by difficult work, and further, since a complicated idling operation detecting means having a structure including a water level sensor, a flow rate sensor, etc. is separately provided, the entire apparatus becomes expensive. There was also.

The present invention has been made in view of the above-mentioned points, and an object thereof is to provide a pump that is operated by an existing photovoltaic power generation facility with an idle operation detection of the pump that has a simple configuration and does not require extensive maintenance and inspection. To provide a pump device.

[Means for solving problems]

In order to solve the above problems, the present invention is a pump device that converts direct-current power generated by a solar cell into alternating-current power through an inverter and operates an alternating-current motor connected to a pump by the alternating-current power. Detects the maximum power tracking means that sends a frequency command signal to the inverter to control the rotation of the AC motor so that the output of the solar cell is maintained at the maximum point, and the direct current supplied from the solar cell to the inverter And an idle operation detecting means for detecting the idle operation of the pump based on both signals of the frequency command signal to the inverter by the maximum power tracking means and the detected current signal from the current sensor. When the detection means detects that the command frequency from the maximum power tracking means has become equal to or higher than a predetermined value with respect to the DC current detected by the current sensor, Characterized by comprising a means for stopping the operation of the electric motor.

[Action]

Since the present invention configures the pump device operated by solar power generation as described above, the pump operated by the existing solar power generation device is provided with a sensor for detecting the direct current supplied from the solar cell to the inverter (the existing In some cases), it is possible to detect the idle operation of the pump simply by providing the pump idle operation detection means of a simple structure that can be installed in a place where there is no water. The operation of the AC motor connected to can be stopped.

Accordingly, it is possible to prevent the AC motor from being damaged due to overheating due to lightening of the load of the AC motor in a state where there is no water and an increase in the rotation speed. Furthermore, since the pump is not wasted during idle operation, it is possible to effectively use energy.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a system configuration of a pump device operated by a photovoltaic power generator according to the present invention. In the figure, 1 is a solar cell, 2 is an inverter that converts direct current from the solar cell 1 into alternating current, and 3 is the inverter 2
A switch 5 for supplying the AC output of the above to the induction motor (AC motor) 4 is a pump driven by the induction motor 4. Reference numeral 7 is a maximum power tracking control device (maximum power tracking means) for performing tracking control so that the output of the solar cell 1 reaches a maximum point, as will be described later in detail, and 8 is a maximum power tracking control device 7 as described later in detail. A pump idle operation detector (idling detection means) for detecting idle operation of the pump 5 from the control frequency of the inverter 2 and the DC current from the solar cell 1, 9 is a relay operated by the output of the pump idle operation detector 8, Reference numeral 10 is a current sensor for detecting a direct current supplied from the solar cell 1 to the inverter 2, 9a is a normally closed contact of the relay 9, 3a is an exciting coil of the switch 3, and 3b is a normal switch of the switch 3. An opening auxiliary contact 11 is a starting switch 11 for starting the induction motor 4 and driving the pump 5.

In the pump device having the above configuration, the start switch 11 is turned on.
Then, an operating current flows through the exciting coil 3a of the switch 3 to close the switch 3. As a result, the DC power generated by the solar cell 1 is converted into AC power having a predetermined frequency by the inverter 2 and supplied to the induction motor 4, the induction motor 4 is started, and the pump 5 is driven. At this time, the maximum power tracking control device 7 controls the frequency of the inverter 2 so that the output of the solar cell 1 reaches the maximum point and controls the rotation speed of the induction motor 4 as will be described later. That is, when the output of the solar cell 1 is high, the frequency of the AC output of the inverter 2 is increased, the rotation speed of the induction motor 4 is increased, the pump 5 is rotated at high speed to increase the flow rate, and conversely, the output of the solar cell 1 is increased. Is small, the AC output frequency of the inverter 2 is lowered, the rotation speed of the induction motor 4 is lowered, the pump 5 is rotated at a low speed, the flow rate is reduced, and the output of the solar cell 1 is maintained at the maximum output point.

Therefore, when the water level is lowered and the pump is in an idle state, the maximum power tracking control device 7 tries to consume a large amount of power generated by the solar cell 1 and rotates the pump 5 at a high speed so that the inverter 2
Try to raise the control frequency of. However, as shown in FIG. 2, the output of the solar cell 1 changes depending on the amount of sunlight LQ1, LQ2, LQ3, LQ4 ,. Cannot detect the idling state of. That is, when the amount of sunlight is large and the amount of power generated by the solar cell 1 is large even in the same idle operation state, the pump 5 needs to be rotated at high speed in order to consume the generated power, but when the amount of power generation is small. The pump 5 does not rotate so fast. Therefore, not only the inverter control frequency f of the maximum power tracking control device 7 but also the output I of the sensor 10 that detects the DC current supplied from the solar cell 1 to the inverter 2 is input to the pump idle operation detector 8. The pump idle operation detector 8 stores in advance the inverter control frequency f for the output current I of the solar cell 1 when the pump 5 is in the idle operation, and the inverter control frequency f for the output current I becomes higher than that. At this time, the pump idle operation detector 8 outputs an output to the relay 9. Relay 9
Is activated, the normally closed contact 9a is opened, the exciting current to the exciting coil 3a of the switch 3 is cut off, the switch 3 is opened, and the induction motor 4 and the pump 5 are stopped.

There are various types of the maximum power tracking control device 7, for example, the one described in JP-A-56-132174 or the applicant of the present invention previously applied for an inverter using a solar cell {Japanese Patent Application No. 56-167680 (JP-A-58-69469). The details are described in the above-mentioned publications, but the portions related to the present application are cited from JP-A-58-69469.

FIG. 3 is a block diagram showing a system configuration of an inverter using the above solar cell. In the figure, the solar cell 21
Thus, the main inverter 22 is driven, and the AC output of the main inverter 22 drives the AC motor 23 that is a load. The auxiliary inverter 24 generates control electric power necessary to operate the main inverter 22. The capacity control circuit unit 25 is a solar cell.
The output voltage V and the output current I of the solar cell 21 are detected.
Is the main inverter so that it operates at the point Pmax where the output power of the voltage V-current I characteristic of the solar cell shown in FIG.
It controls 22 outputs, namely frequency and voltage. Reference numeral 26 denotes a current sensor.

When the above capacity control circuit 25 is used as the maximum power tracking control device 7 in FIG. 1, the solar cell 1 is always operated at the maximum output point Pmax.

The relationship between the total head of the pump 5 and the flow rate is as shown in FIG. 5, and the relationship between the output of the induction motor 4 and the flow rate of the pump 5 is as shown in FIG. That is, FIG. 5 shows that the longer the total head is, the higher the frequency of the induction motor 4 that drives the pump 5 is required. Further, as the solar radiation increases, the output of the solar cell 1 increases, and the output of the induction motor 4 increases, the pump rotates at a higher speed, that is, a higher frequency, as shown in FIG.

Since the load becomes lighter when the water level is lowered and the pump 5 is in the idling state, the maximum power tracking control device 7 tries to maintain the output of the solar cell 1 at the maximum output point Pmax (in order to consume a large amount of generated power), Since the induction motor 4 is rotated at high speed, the control frequency of the inverter 2 becomes high. Since the frequency in this case becomes higher than the frequency shown in FIG. 6, if this state continues, the induction motor 4 may be damaged by heating, and the electric power generated by the solar cell 1 will be wasted.

Therefore, the maximum output point of the solar cell 1 as shown in FIG.
Output current I maintained at Pmax and corresponding pump 5
Frequency in the idle operation state (for example, the flow rate 0 shown in FIG.
(Predetermined value higher than the frequency at the output) is set in advance and described in the pump slip detector 8, and the inverter 2 when the output current I of the solar cell 1 has a certain value as described above.
It is determined whether the control frequency f of 1 exceeds the frequency in the idling state. If the pump is idling, the relay 9 is operated as described above to open the switch 3 and stop the induction motor 4.

In the above embodiment, as a means for stopping the AC motor 4 when the inverter control frequency becomes a predetermined value or more for the DC current detected by the DC sensor 10, the output of the pump idle operation detector 8 operates. Although the contact relay 9 is used to interrupt the current supplied to the exciting coil 3a at its normally closed contact, the present invention is not limited to this. For example, the output of the pump idle operation detector 8 may be used to operate the inverter 2. The circuit may be configured to stop (see the portion indicated by the dotted line S in FIG. 1). In short, when the inverter control frequency of the maximum power tracking control device 7 exceeds a predetermined value with respect to the DC current detected by the DC sensor 10, the AC motor 4 is stopped and the pump 5 is stopped by the output from the pump idle operation detector. As a matter of course, any configuration may be used as long as it is a configuration.

〔The invention's effect〕

As described above, according to the present invention, the pump idle operation detection means is a pump when the inverter control frequency of the maximum power tracking means is a predetermined value or more for the DC current from the solar cell detected by the DC sensor. Since the AC motor is stopped when it is judged that the pump is running idle, maintenance and inspection can be performed easily without the provision of a pump idle running detection means that is difficult to maintain and inspect using a water level sensor, flow rate sensor, etc. as in the past. In addition, it is possible to prevent the pump from running dry with an extremely inexpensive device, and the pump's running idle is determined by considering not only the inverter control frequency, but also the DC current from the solar cell, thus ensuring the pump running dry. The excellent effect of being detectable is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration of a pump device operated by a photovoltaic power generator according to the present invention, and FIG. 2 is a diagram showing a relationship between irradiation sunlight of a solar cell and output current I and voltage V, FIG. FIG. 3 is a block diagram showing a system configuration of an inverter using a solar cell, which the present applicant has previously applied, FIG. 4 is a diagram showing characteristics of voltage V-current I of the solar cell, and FIG. 5 is a total pump head. And FIG. 6 is a diagram showing the relationship between the output of the induction motor and the flow rate of the pump. In the figure, 1 ... Solar cell, 2 ... Inverter, 3 ... Switch, 4 ... Induction motor, 5 ... Pump, 7 ... Maximum power tracking control device, 8 ... Pump running detector, 9 …… Relay, 10 …… Current sensor, 11 …… Start switch.

Continuation of front page (56) References JP-A-58-69469 (JP, A) JP-A-58-122382 (JP, A) JP-A-57-40373 (JP, A)

Claims (1)

(57) [Claims] 1. A pump device for converting direct-current power generated by a solar cell into alternating-current power through an inverter and operating an alternating-current motor connected to the pump by the alternating-current power, wherein a frequency command signal is sent to the inverter. And a maximum power tracking means for controlling the rotation of the AC electric motor to control the output of the solar cell to be maintained at a maximum point, and a current for detecting a direct current supplied from the solar cell to the inverter. A sensor and an idle operation detection means for detecting an idle operation of the pump based on both signals of a frequency command signal to the inverter by the maximum power tracking means and a detected current signal from the current sensor, The command frequency from the maximum power tracking means is equal to or higher than a predetermined value for the direct current detected by the operation detection means by the current sensor. A pump device comprising means for stopping the operation of the alternating-current motor when the above is detected.