JPS61109120A - Power supply device - Google Patents

Abstract

PURPOSE:To eliminate the unstable state of a control system by detecting the irradiation energy density of the sunbeam with a solar battery for control and controlling the frequency and the voltage of a variable frequency inverter so that the fixed relation is secured between the current of said energy density and the output current of the solar battery. CONSTITUTION:An AC motor 3 is driven by a solar battery 1 via a variable frequency inverter 2, and a pump 4 connected to the motor 3 is operated. Here a solar battery 1a for control is provided for detection of the irradiation energy density together with resistors 14 and 15 which obtain the reference voltage from said energy density for control of the inverter 2, an output current detector 16 and a limiting circuit 17 which delivers no output as long as the output voltage of the battery 1 is higher than a prescribed level. Thus the fixed relation is secured between the irradiation energy density detected by the battery 1a and the input voltage of the inverter 2. Furthermore, the frequency and the output voltage of the inverter 2 are controlled so that the input voltage of the inverter 2 is higher than a fixed level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply device that uses a solar cell as a power source and drives an AC motor in combination with a variable frequency inverter (vrvtvr').

[Conventional technology]

When supplying power to a load using a solar cell as a power source, the solar cell has voltage-current characteristics as shown in Figure 2, so in order to efficiently utilize the irradiation energy of sunlight, the maximum value that changes depending on the irradiation energy must be It must be operated at the power point (Pm) @ For this reason, various types of control have been devised in conventional power supply devices of this type to maximize the output of the solar cells.

FIG. 4 is a circuit diagram showing a conventional power supply device driven by a solar cell, as disclosed in, for example, Japanese Patent Application Laid-Open No. 56-112174. In the figure, III is a solar cell, (2) is a variable frequency inverter, (31 is an AC motor, 141 is a pump connected and driven with the AC motor (3), (51° (6)
is a resistor for detecting the output voltage of solar cell II+, (
7) is the reference power supply, (8) is the reference voltage setting resistor, (9)
is a ratio means for producing a deviation between the reference voltage setting value and the detected value of the output voltage of the solar cell, (1o1 is an amplifier for the deviation, between is a variable frequency inverter (21 is a frequency controller, and concave is a voltage The controller +131 is a pulse generating circuit that causes the variable wave inverter (2) to generate a frequency and voltage output determined by the frequency controller (11) and the voltage controller (2).

In the circuit shown in Figure 4, variable frequency inverter (2)
is a solar cell + regardless of changes in sunlight irradiation energy.
The frequency and voltage of the variable frequency inverter (2) are controlled so that the output voltage of the variable frequency inverter (2) is kept approximately constant.

In this conventional example, as can be seen from the voltage-current characteristics of the solar cell in Fig. 2, the solar cell 11
Focusing on the fact that the change in the maximum output (Pm) t-(l) of the optimum voltage Vop is small, the voltage set by the reference voltage setting resistor (8) is used as a reference, and the solar cell is In order to keep the output voltage of +11 almost constant,
It is characterized by controlling the frequency of the variable opening inverter (2).

In this way, solar power a is independent of changes in irradiation energy.
Although the output voltage of ll+ is controlled to be almost constant, it changes depending on how the reference voltage is set, but it is impossible to control the entire range of irradiation energy to the maximum output, and it is impossible to control the entire range of irradiation energy to the maximum output. Above all, the reference is set and the voltage is controlled so that the maximum output is IAI at the most important chain acid.

[Problem that the invention seeks to solve]

In this case, for irradiation energy densities other than the irradiation energy conflict for which the maximum output is applied, constant voltage control is performed to an approximate value of the commuting voltage, and constant voltage control is performed based on a constant voltage. It is not possible to obtain maximum output over the entire irradiation energy range. Particularly in the singing region where the density of irradiation energy is low, the output of the solar cell (H) tends to decrease rapidly when the reference voltage is higher than the optimum operating voltage.

Moreover, if the l11m deviation occurs in the direction of increasing the voltage, the output of the solar cell will drop even more rapidly, and may even decrease to - several minutes.

This invention attempts to improve such drawbacks of the conventional example.

[Means for solving problems]

This invention detects a current proportional to the irradiation energy density using a control solar cell, and also detects the input voltage of a variable frequency inverter, so that the detected current and the output current of the solar cell have a constant relationship. In addition, the frequency and output voltage of the variable frequency inverter are limited so that the input voltage of the variable frequency inverter exceeds a certain value.

[Effect]

By doing so, the instability of the control system associated with maximum output control can be eliminated, and a highly stable power supply device can be achieved.

[Embodiments of the invention]

FIG. 1 shows a complete circuit diagram of an embodiment of the present invention.

In the figure, (la) is a control solar cell installed to detect the irradiation energy rebate, and +14QIlil is a control solar cell that controls the variable frequency inverter (2) from the irradiation energy density detected by the control solar cell a (la). a resistor for obtaining the reference voltage of the ablation, an output current detection device provided to compare the output current of the αeri solar cell II+ with the reference voltage, f1η is the solar cell Il detected by the detection resistor (6);
A limiter circuit that does not output when the + output voltage exceeds a predetermined value (limiter 1 circuit. Its capacity is +1t~ (I3 indicates the same parts as the conventional system).

Next, the operation will be explained.

First, in FIG. 2, the current of the solar cell +11 has a constant current characteristic that can be considered to be almost constant for all irradiation energy densities at a voltage of 70% or less of the open weight cell (VOC) of the solar cell Il+. to have,
And the relationship between irradiation energy key density and voltage, current, and output? In Figure 8 shown, the current and output of the solar cell are both proportional to changes in the irradiation energy density. A solar molten pool (la) is provided, and resistors 041 and t151 are connected to it to allow a current to flow. In this case, the resistance value (R) for Taiyo Denya (1a)
For example, when the operating voltage of the solar cell il+ becomes 70% or less of the open circuit voltage (VOC) and the current of the solar cell il+ becomes a constant value,
Select the range shown in the diagram below.

If the electron drop generated in the resistor Q51 under the above conditions is taken as a reference voltage, this reference voltage always changes in proportion to the irradiation energy density, and the reference voltage represents the irradiation energy.

Next, the output current of the solar cell il+ is measured by the output current detection device (1
υ is detected and compared with the reference voltage by the comparison means (9), and if the output voltage of the solar cell fi+ (input voltage of the inverter (21)) detected by the detection resistor (2) also becomes less than a predetermined value. , is output from the limiting circuit fj71 and compared by the comparing means (9).This deviation signal is output from the amplifier (1
It is amplified by α and controls the frequency and output voltage of the variable frequency inverter (2).

That is, when the output voltage is above a predetermined value, the output current is simply controlled to be equal to the reference voltage, and when the output voltage is below the predetermined value, the voltage value is limited by the voltage feedback effect.

By the way, when a solar cell is used to drive an induction motor (AC motor), as mentioned above, the solar cell exhibits almost constant current characteristics at 70% or less of V (, C), so the normal voltage source %, Unlike when driven by a current source, the generated torque characteristics of an electric motor rapidly decrease as the slip increases (indicating the so-called current source drive characteristics). In order to ) has a large deviation output value, and conversely, if it exceeds the steady operating point, the current deviation output value becomes very small. For this reason, if there is an overshoot kf, the slip will increase and there is a possibility that it will even lead to a step-out. However, in this case, the voltage of the solar cell rapidly decreases, and when it exceeds a predetermined value (a value selected slightly lower than V □ p in Figure 2), the Narita signal is output from the limiting circuit 11η. By increasing the degree of increase (gain) to 1, even if the amount of current feedback decreases, an increase in frequency, that is, an increase in slip can be suppressed, and instability such as step-out can be prevented.

In this control method, 111 reference voltage is equal to the irradiation energy density.

(21 The maximum output (Pm) f, # of the solar cell Il+ should always be approximately 90% of the short circuit current (fsc).

Therefore, this control accurately controls the maximum power (Pm) over the entire range of sunlight irradiation energy, and drives the AC pump without instability such as step-out due to the voltage control action.

Therefore, the present invention adds control solar power a (la) to the conventional system.
) A high-performance power supply device that can effectively utilize solar energy for water pumping, etc., as well as low irradiation energy chain acids, which were considered impossible with conventional systems.
-Can be provided.

As another embodiment of this invention, a control solar cell (la
) Can also be used for both irradiation energy detection and control power supply.

〔Effect of the invention〕

As explained above, the present invention includes a control solar cell that detects the irradiation energy density of sunlight, a detector that detects the input voltage of a variable 8-wave inverter, and a current of the control solar cell and an output current of the solar cell. The variable frequency inverter is equipped with means for controlling the frequency and output voltage of the single-wave inverter so that , regardless of the irradiation energy conflict, the effect is that the maximum output sound of the solar cell can always be brought out stably.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a power supply device according to an embodiment of the present invention, and Fig. 2 shows the voltage-current characteristics (
(solid line) and voltage-5 output characteristics (dotted line). Figure 3 shows the irradiation energy density and voltage, current, and
FIG. 4 is a diagram showing the relationship between outputs, and is a configuration diagram of a conventional power supply system; d. In the figure, ■ is a solar cell, (''a) is a control solar cell, (2) is a variable frequency inverter, (9) is a comparison means, 111) is a frequency controller, (mouth is a voltage controller, (14[ 151 resistors, (lυ is an output current detection device, and IIηl-i is a voltage signal limiter circuit. In the drawings, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] In a device that uses a solar cell as a power source to drive an AC motor via a variable frequency inverter, the control solar cell detects the irradiation energy density of sunlight, the detector detects the input voltage of the variable frequency inverter, and the control device The frequency and output voltage of the variable frequency inverter are controlled so that the current of the solar cell and the output current of the solar cell have a constant relationship, and the input voltage of the variable frequency inverter exceeds a certain value. A power supply device characterized by comprising means.