JP2003009572A - Rotating apparatus control device using solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a rotating apparatus to reach the maximum power point and converge in a shorter time with less overshoot to rotation speed for reaching the maximum power point. SOLUTION: A rotating apparatus control device controls the rotation speed of the rotating apparatus by pursuing or searching for the maximum power point where the input power from a solar cell becomes maximum. The maximum power point is pursued or searched for by determining the increase or decrease of the operating frequency based on the operating frequency of the apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for controlling the rotation speed of a rotating device such as a pump when the rotating device is rotated by using the solar battery as a stand-alone power source, and particularly from a solar battery. The present invention relates to a rotating device control device having a maximum power point tracking control function for controlling the rotation speed of a rotating device such as a pump so that the input power of the device becomes maximum.

[0002]

2. Description of the Related Art For example, in a ranch in an area where power supply is poor, a rotating device such as a submersible motor pump for a deep well is variably operated by a solar battery to control a control device such as an inverter, and the May be pumped to an elevated water tank, and the water may be stored and used as drinking water for livestock. In such a device, the operating frequency of the pump is automatically adjusted by an inverter so that the pump (rotating device) operates efficiently according to the amount of solar radiation. That is, the so-called maximum power point tracking control is performed, in which the input power from the solar cell is measured, the change in the input power is detected while changing the rotation speed of the pump, and the operation is performed at the point where the input power becomes maximum.

Conventionally, in this type of control, it is general to keep the increase / decrease value ΔF of the operating frequency of the pump (rotating device) constant. FIG. 6 is a characteristic diagram of a solar cell at a certain temperature and a certain amount of solar radiation. As shown in FIG. 6, when the pump is not in operation, no current flows, so that the voltage is, for example, point A (current 0). Then, when it is detected that the solar radiation becomes strong and the input voltage from the solar cell becomes equal to or higher than the voltage at which the pump can be operated, the pump operation is started and the operating frequency is gradually increased. That is, the operating frequency F of the pump is increased by a constant increase value ΔF. Since a current flows when the operation is started, the electric power changes from point A to point B on the characteristic diagram shown in FIG. The dotted line shows the electric power obtained from the current / voltage. In order to operate at the maximum power point, the rotational speed of the pump may be increased so as to reach point C, which is the maximum power point. Further, if the power does not increase even if the operating frequency F is gradually increased, the operating frequency F is gradually decreased by a constant decrease value ΔF.

[0004]

However, if the inverter catches a change in the electric power while increasing the rotation speed of the pump (rotating device) and continues to accelerate the electric power even if the electric power is accelerated, the acceleration is excessive and the solar cell is increased. In some cases, the power supplied from the power supply abruptly decreases and reaches the point B shown in FIG. 6, for example, so that the rotation speed cannot be maintained and the pump stops. In order to avoid this, it is necessary to prevent a sudden load change from occurring when the pump changes its rotation speed. The pump load (shaft power) usually increases / decreases as the rotational speed of the pump increases or decreases, that is, in proportion to the cube of the rotational speed of the pump. Therefore, it is necessary to set the increase / decrease value ΔF of the operating frequency of the pump small so that the rate of change of the load with time at the maximum rotation speed falls within the allowable range. However, if the increase / decrease value ΔF of the operating frequency F is set small, there is a problem that the arrival at the maximum power point is delayed.

That is, as shown in FIG. 3, when the rotational speed of the pump is controlled by keeping the rate of change of the operating frequency constant, the pump shaft power increases or decreases with respect to the operating frequency increase / decrease value ΔF in the low operating frequency region. However, in the high operating frequency range, the operating frequency greatly changes with respect to the increase / decrease value ΔF. Therefore, when the rotation speed is increased constantly, the electric power fluctuates rapidly at high rotation speeds. Therefore, if the increase / decrease value ΔF of the operating frequency is set to a large value, the overshoot with respect to the maximum power point C (see FIG. 6) becomes large and the operation cannot be maintained. Conversely, if the increase / decrease value ΔF of the operating frequency is set small, the time required to reach the vicinity of the maximum power point C becomes long. Considering that the gradient of the axial power change at the target reaching point should be a controllable gradient, it is necessary to lengthen the acceleration time in accordance with the case where the solar cell reaches the maximum output. Therefore, the acceleration time must be long even in the region where the change in the axial power of the pump is small.
In this way, if the acceleration time is lengthened, the output of the solar cell changes under the influence of the weather, etc., so that effective use of solar energy cannot be achieved.

In view of the above, the present invention provides a solar cell that has less overshoot with respect to the rotation speed that reaches the maximum power point and that allows rotating equipment to reach the maximum power point and converge in a shorter time. It is an object of the present invention to provide a control device for a rotating machine used.

[0007]

According to a first aspect of the present invention, the rotating device controls the rotation speed of the rotating device by tracking or searching for the maximum power point at which the input power from the solar cell is maximum. The control device for a rotating device using a solar cell is characterized in that the increase / decrease value of the operating frequency is determined based on the operating frequency of the rotating device to trace or search for the maximum power point.

Thus, the increase / decrease value of the operating frequency (rotational speed) of the rotating device is appropriately changed according to the operating frequency of the rotating device so that the rate of change of the load of the rotating device with time is constant. The input power from the solar cell can be linearly changed with respect to the elapsed time regardless of the operating frequency of the rotating device.

According to a second aspect of the present invention, the rotating device is a device having a square reduction torque characteristic, and the increase / decrease value of the operating frequency is determined in proportion to the square of the operating frequency of the rotating device. The control device for a rotating device using the solar cell according to claim 1. As a result, the gradient of increase or decrease in the shaft power of the rotating device can be made constant regardless of the operating frequency, and the control can be significantly stabilized.

According to a third aspect of the present invention, the increase / decrease value of the operating frequency of the rotating device is not fixed below the predetermined operating frequency, and is determined based on the operating frequency when the operating frequency is exceeded. A control device for a rotating device using the solar cell according to claim 1 or 2.

Thus, the operating frequency is theoretically infinite when the operating frequency is 0 by keeping the increase / decrease value of the operating frequency constant until the operating frequency becomes 0 to a relatively low operating frequency. It is possible to prevent that.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a system configuration diagram of the present invention applied to a water pumping apparatus. This water pumping apparatus is driven by a solar cell 1 for converting solar energy into electric energy, an inverter 2 for converting DC power output from the solar cell 1 into AC power, and AC power converted by the inverter 2. And a motor pump 3 that operates. The inverter 2 has a system control program built in an internal microcomputer to control the rotation speed of the motor pump 3.

The motor pump 3 is a deep well submersible motor pump in which a pump and a DC brushless scanned motor are integrated, and the well water inside the well 6 through a discharge pipe 4 into a water tank 5 installed on the ground. Pump water. The water stored in the water tank 5 is supplied to the required area through the supply pipe 8 by opening the valve 7.

[0014] Here, when the solar radiation becomes strong and the input voltage from the solar cell 1 rises to a voltage judged to be sufficient for the operation of the motor pump 3, the motor pump 3 is started, and The input voltage from the solar cell 1 drops due to the shadows, the insolation being insufficient due to sunset, etc.
When reaching the set input voltage or less, the inverter 2 stops the motor pump 3. Further, during operation of the motor pump 3, this operating frequency is adjusted by the maximum power point tracking control so that the input power from the solar cell 1 becomes maximum.

FIG. 2 shows a block diagram of maximum power point tracking control. As shown in FIG. 2, the input current I and the input voltage V are input to the input voltage calculation unit 10, and the input voltage calculation unit 10 is input.
The input voltage P is calculated by. Then, this input voltage P is input to the power comparison unit 12, the power comparison unit 12 compares the input power P with the previous input power P ', and the next rotation speed is output based on the comparison result. . That is, the motor pump 3
The rotation speed of the motor pump 3 is controlled as shown in Table 1 below by the change in the input power P, and the motor pump 3 is operated at the rotation speed that maximizes the input power.

[Table 1]

In the present invention, when the rotational speed of the motor pump 3 is accelerated and decelerated, the load change rate during the acceleration / deceleration time is controlled to be constant as follows. this is,
Since the output power of the solar cell 1 at a constant temperature and a constant amount of solar radiation changes depending on the output power of the inverter 2, that is, the fluctuation of the pump shaft power (load), it can be controlled by controlling the fluctuation of the pump shaft power. is there. In this way, in the maximum power point tracking control, the load change rate is controlled to be constant, and the time change rate of the pump load is made as constant as possible, so that the maximum power point C from the start of operation (see FIG. 6). The time to reach can be shortened.

This control method is as follows using the current value F of the operating frequency of the motor pump 3 as a parameter. For O ≦ _F ≦ F ₁ frequency increase rate command value ^{_{= 1000 × K 3 × F 1}} -2 (Hz
/ S) frequency reduction rate command value _{= -1 × C × 1000 × K} 3 × F
₁ ⁻² (Hz / s) F ≧ F ₁ Frequency increase rate command value = 1000 × K ₃ × F ⁻² (Hz /
s) Frequency decrease rate command value _{= -1 × C × 1000 × K} 3 × F
^-2 (Hz / s) Here, the above-mentioned F ₁ , C and K ₃ are defined and set as shown in Table 2 below.

[Table 2] The above parameters are rewritable by a setting device or the like, and initial values are adopted if they are not set. With the proper setting of parameters, the pump reaches the maximum power point quickly.

Here, until the operating frequency F becomes 0 to a relatively low operating frequency F ₁ (acceleration / deceleration control switching frequency),
The reason why the increase / decrease value ΔF of the operating frequency is controlled to be constant as in the conventional case is to prevent the increase / decrease value ΔF when the operating frequency is 0 from being theoretically infinite.
Further, since the phenomenon is different when the rotation speed of the motor pump is increased and when it is decreased, adjustment is performed using a constant C for changing the increase / decrease speed between increase and decrease.

FIG. 3 shows a case where the change rate of the pump operating frequency and a change over time of the pump shaft power are controlled at a constant load change rate (embodiment of the present invention) and a constant frequency change rate (conventional example). ) Is a graph showing by comparison with FIG. here,
The horizontal axis shows elapsed time, and the vertical axis shows operating frequency and pump shaft power.

In the case where the load change rate is controlled to be constant (embodiment of the present invention), the slope of the increase / decrease in the power of the pump shaft is constant regardless of the value of the operating frequency, so the control is remarkably stable. . Further, it is possible to always reach the maximum power point stably in the shortest time even with respect to the maximum output of the solar cell which changes under the influence of the weather and the like. That is, in the example shown in FIG. 3, it takes 90 seconds to reach the maximum power point when the change rate of the operating frequency is controlled to be constant (conventional example), whereas the load change rate is controlled to be constant. In this case (embodiment of the present invention), the maximum power point can be reached in 30 seconds.

Also, regarding the setting parameters, if the relationship between the parameters is clear, it is possible to omit setting of certain parameters. Hereinafter, the details of the control method of the pump having the squared torque reduction characteristic, the meaning of the parameters and the determination method will be described.

Pump load time at MPP (maximum power point)
Frequency control method to keep the rate of change constant 1. Basic formula Since the time change of the pump load is constant, P = K₁× t ………… Expression (1) Where P: pump shaft power (w), t: elapsed time
(S), K₁: Load change rate (w / s) Also, since the shaft power of the pump is proportional to the cube of the frequency, P = K_TwoXf^Three  ………… Expression (2) Where f: frequency (Hz), K_Two: Pump torque characteristics
Constant determined by sex (W / Hz^Three) From equations (1) and (2), K₁× t = K_TwoXf^Three  ………… Expression (3) f = (t × K₁/ K_Two)^1/3 Therefore, the time change rate f ′ of the frequency f is     f ′ = df / dt = 1/3 × (K₁/ K_Two)^1/3× t^-2/3………… Formula (4) From equation (3), t = f^Three× K_Two/ K₁ Substituting this into equation (4),     f ′ = 1/3 × (K₁/ K_Two)^1/3X (f^Three× K_Two/ K₁)^-2/3         = 1/3 x K₁/ K_TwoXf^-2  ………… Expression (5)

Therefore, f '(Hz / s) determined by the equation (5) using the current frequency f (Hz) as a parameter
By accelerating at, it is possible to make the time change of the shaft power of the pump constant. However, since f = 0 at the time of starting, f '= ∞ and control cannot be performed. Therefore, from the start to a certain frequency f ₁ , the control is performed with f ′ = f ₁ ′ = constant as usual.

2. Program Specifications In the actual program, K ₃ = (1/3 × K ₁ / K ₂ ) / 1000, and the acceleration / deceleration command value at the current operating frequency f is as follows. When 0 ≦ f <f _{1 During} acceleration: f ′ = f ₁ ′ = 1000 × K ₃ × f
₁ ⁻² (Hz / s) During deceleration: f ′ = f ₁ ′ = −1 × C × 1000 × K ₃ ×
f ₁ ^-2 (Hz / s) when the case of acceleration _{f ≧ f 1: f '=} 1000 × K 3 × f -2 (Hz / s) during deceleration: f' = - 1 × C × 1000 × K 3 × f
^-2 (Hz / s) Here, C is a deceleration coefficient of 1 or more. By providing the deceleration coefficient in this way and making the deceleration rate larger than the acceleration rate, the followability of MPPT control is improved. You can

3. Method of determining parameter value The following four parameter values need to be determined. K ₁ : load change rate (w / s) K ₂ : constant determined by pump torque characteristics (w / H)
z ³ ) f ₁ : Switching frequency (Hz) C: Reduction coefficient

1) Determination of the load change rate K ₁ The load change rate has a maximum value that can be MPPT controlled depending on the inertia of the pump-motor rotating body and the control speed of the inverter. The value is determined by a test.

2) Constant determined by the torque characteristic of the pump
Number K_TwoDecision The pump operating point is changed at a specific frequency F,
The maximum input Pmax of the inverter is calculated and determined by the following equation. K_Two= Pmax / F^Three Here, Pmax is the location measured by the MPPT control
And the same place as the power. That is, the inverter input is controlled.
Inverter input, motor input if used
When using, set the maximum value of motor input to Pmax.
It

3) Switching frequency f₁Decision Switching frequency f₁Use the following values as a guide. f₁= (1/3)^1/2× (K₁/ K_Two)^1/3 This switching frequency f₁Is the operating frequency, as shown in FIG.
When the rate of change of the number is constant, the power after 1 second from the start is K
₁It is a value determined to be × 1 s. Switching frequency f
₁Is smaller than this value, the MPP arrival time is short.
And the increase in the electric power (P) at the time of starting increases. Reverse
If it is larger than this value, the MPP arrival time is long.
And the increase in the electric power (P) at the start is small.

4) Determination of the deceleration coefficient C The deceleration coefficient is determined by testing so that the MPPT control stability and followability are optimized.

FIG. 5 shows an example of the relationship between the current frequency value and the increase / decrease frequency instruction value. Currently operating frequency is 10Hz
In the following, the increase / decrease frequency instruction value becomes too large and is therefore kept constant. Also, as a method of obtaining the increase / decrease frequency instruction value from the current frequency value, a method of calculating with a mathematical formula was shown, but it is derived from the data table of the increase / decrease frequency instruction value stored corresponding to the current frequency in the digital control. You may do it. At that time, it is needless to say that even if the current frequency decomposition is set to be considerably large and the number of table data is reduced, a certain effect can be expected.

[0031]

As described above, according to the present invention,
Since rotating equipment such as pumps can be quickly made to reach the maximum power point in the limited amount of solar radiation and can be operated, solar energy can be effectively used. It is possible to secure a larger amount of pumping in the amount of solar radiation.

[Brief description of drawings]

FIG. 1 is a system configuration diagram applied to a pumping apparatus of the present invention.

FIG. 2 is a block diagram of maximum power point tracking control.

FIG. 3 shows a case where a load change rate is controlled to be constant (a preferred embodiment of the present invention) and a frequency change rate is controlled to be constant (conventional example) with respect to a change over time of a pump operating frequency and pump shaft power.
It is a graph which compares and shows.

FIG. 4 is a graph attached to an explanation when determining a switching frequency.

FIG. 5 is a graph showing an example of a relationship between an increase / decrease frequency instruction value with respect to a current frequency value.

FIG. 6 is a graph showing solar cell characteristics.

[Explanation of symbols]

1 solar cell 2 inverter 3 motor pump 5 water tank 10 Input voltage calculator 12 Power comparison unit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kaoru Nakajima             11-1 Haneda Asahi-cho, Ota-ku, Tokyo Co., Ltd.             Inside the EBARA CORPORATION F term (reference) 3H020 AA02 AA08 BA01 BA11 BA18                       BA21 CA08 DA04 EA07                 3H045 AA06 AA09 AA13 AA23 AA40                       BA01 BA28 BA31 BA40 BA41                       CA21 DA07 DA45 EA34                 5H420 BB02 BB14 CC03 DD03 DD06                       EB26 EB39 GG03                 5H560 AA10 EB01 GG03 HA10 SS01

Claims (3)

[Claims] 1. A control device for a rotating device, which controls the rotation speed of a rotating device by tracing or searching for a maximum power point at which the input power from a solar cell is maximum, based on an operating frequency of the rotating device. A control device for a rotating device using a solar cell, wherein an increase / decrease value of an operating frequency is determined and a maximum power point is tracked or searched. 2. The rotating device is a device having a square reduction torque characteristic, and the increase / decrease value of the operating frequency is determined in proportion to the square of the operating frequency of the rotating device. A control device for a rotating device using the solar cell according to claim 1. 3. The increase / decrease value of the operating frequency of the rotating device is
The control device for a rotating device using a solar cell according to claim 1 or 2, wherein the control is not constant below a predetermined operating frequency, and is determined based on the operating frequency when the operating frequency is exceeded.