JP2000020149A - Sunshine inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time until when much electric power can be taken out and to lighten the load of calculation of output electric power, etc., by allowing an inverter control circuit to perform constant-voltage control over a solar battery according to a certain initial voltage. SOLUTION: The voltage of the solar battery 1 charges a capacitor C1 and is supplied to an inverter main circuit 2. The AC output of the inverter main circuit 2 is supplied to a load L through an output filter 24 consisting of a reactor 22 and a capacitor 23. At this time, the inverter control circuit 3 performs control with the initial voltage which is lower than an open voltage. When the solar battery 1 is normally used, the initial voltage is set almost to the operation point of maximum output. Here, an initial voltage varying means 31a may be added which optionally varies and stores the initial voltage stored in a voltage comparator 31. Consequently, the device is easily adaptive to variation of characteristics of the solar battery 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for converting a DC power source obtained from a solar cell into an AC power source and connecting the AC power source to a commercial power system.

[0002]

2. Description of the Related Art Conventionally, a solar cell used in a photovoltaic power generator has characteristics as shown in FIG. 5 when the amount of solar radiation incident on the solar cell is used as a parameter. In FIG. 5, a solid line indicates a voltage-power characteristic, and a broken line indicates a voltage-current characteristic.

As shown in FIG. 5, solar cells tend to increase both in power and current as the amount of solar radiation increases. Note that p1, p2, p3,... Indicate the maximum power point, and q1,
.., q2, q3,... indicate operating points at which current and voltage are supplied at the time of maximum power output.

In order to efficiently extract the maximum power from a solar cell having such characteristics, a technique called hill-climbing control is used. This control method operates the solar cell at two different operating points and compares the output powers thereof, so that the operating point of the solar cell becomes the maximum power output point. It is controlled to climb to the top.

[0005] For example, a case where the solar cell has a voltage-power characteristic as shown in FIG. 6 under a constant solar radiation amount will be described. In the conventional hill-climbing control, first, the output voltage reference of the solar cell is reduced from the open-circuit voltage V0 at a predetermined sampling cycle with a constant change width (correction voltage) ΔV. At this time, the output power increases in the direction A in FIG.

When the output power reaches the maximum power output point Pmax
Is exceeded, the output power will decrease in the B direction. In the hill-climbing control, this decrease is detected, and the output voltage reference is increased by the change width ΔV. As a result, the output power is
In the C direction. And again the maximum power output point P
Beyond max, it begins to decrease in the D direction. When this decrease is detected, the output voltage reference is decreased again by the change width ΔV.

By repeating the above operation, the output voltage reference is reciprocated in the vicinity of the maximum power output point Pmax, so that the maximum power output point Pmax of the solar cell always follows. Note that there is also a method in which the tracking in the vicinity of the maximum power output point Pmax is performed more precisely by reducing the variation width ΔV near the maximum power output point Pmax.

[0008]

However, in the inverter device configured as described above, the follow-up control is performed gradually from the open voltage V0 toward the maximum power output point Pmax. There is a problem that it takes a considerable time to reach. In addition, the hill-climbing control has a problem in that calculations such as determining the direction of change of the voltage reference in accordance with the output power are required one after another, which places a burden on an arithmetic unit (CPU) for the calculation. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to shorten the time required to extract a large amount of electric power and to reduce the time. Another object of the present invention is to provide an inverter device in which the burden of calculation of output power and the like is reduced.

[0010]

According to the first aspect of the present invention,
In an inverter device including an inverter main circuit for linking a DC power supply output from a solar cell to a commercial power system and an inverter control circuit for controlling the inverter main circuit, the inverter control circuit uses a constant initial voltage based on a constant initial voltage. The battery is controlled at a constant voltage.

According to a second aspect of the present invention, in the solar inverter device according to the first aspect, the inverter control circuit comprises:
A plurality of initial voltages are stored in advance, and the initial voltage for performing the constant voltage control is changed based on the output level of the solar cell.

According to a third aspect of the present invention, in the solar inverter device according to the first or second aspect, the inverter control circuit includes an initial voltage changing unit that can arbitrarily change a set value of the initial voltage. It is characterized by the following.

According to a fourth aspect of the present invention, in the solar inverter device according to any one of the first to third aspects, the inverter control circuit includes an initial voltage until the output level of the solar cell exceeds a predetermined constant voltage control level. Control based on
After the constant voltage control level is exceeded, hill-climbing control for increasing or decreasing the correction voltage with respect to the initial voltage is performed so that the output of the solar cell becomes maximum.

According to a fifth aspect of the present invention, in the solar inverter device according to the fourth aspect, the solar cell outputs the maximum power at the constant voltage control level with respect to the initial voltage when switching from the constant voltage control to the hill-climbing control. It is characterized in that a value higher than the voltage value is set as the initial voltage.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a solar inverter according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2, and a solar inverter according to a second embodiment will be described with reference to FIGS. 4 will be described in detail. [First Embodiment] FIG. 1 is a schematic configuration diagram of a solar inverter device. FIG. 2 is a graph showing voltage-power characteristics of the solar cell at each solar radiation.

As shown in FIG. 1, the inverter device comprises a solar cell 1, an inverter main circuit 2, and an inverter control circuit 3, and the inverter main circuit 2 is connected to a commercial power system 5.

The inverter main circuit 2 includes a switching element 21 including semiconductor switching elements Q1 to Q4 and diodes D1 to D4, an output filter 24 including a reactor 22 and a capacitor 23. The switching element 21 converts DC power from the solar cell 1 into commercial AC power having a desired voltage by switching the DC power from the solar cell 1 according to a PWM (pulse width modulation) command given from the inverter control circuit 3. The output filter 24 removes high-frequency components generated by switching and outputs only commercial frequency components.

The inverter control circuit 3 issues a PWM command to the switching element 21 based on a current signal from a current detector 25 provided in the inverter main circuit 2 and a voltage signal of an output terminal voltage at both ends of the load L. To perform current control. The inverter control circuit 3 includes a voltage comparator 31 that compares a predetermined initial voltage V1 and an output voltage of the solar cell 1, and a current command value that calculates an amplitude value of the current command value according to the output of the voltage comparator 31. Amplitude calculator 32, current command value phase calculator 33 for calculating the phase of the current command value from commercial power system 5, and current command value calculator for calculating the current command value to be given next from the calculated amplitude value and phase 34
For performing PWM control from the output current and the current command value
And an M controller 35.

Next, the operation of the inverter device according to the present embodiment will be described. In FIG. 1, the voltage of the solar cell 1 charges a capacitor C1 and is supplied to an inverter main circuit 2. The AC output of the inverter main circuit 2 is supplied to the load L via an output filter 24 including a reactor 22 and a capacitor 23.

At this time, as shown in FIG. 2, the inverter control circuit 3 controls at an initial voltage V1 which is lower than the open-circuit voltage V0. In the inverter device of the present embodiment, in a state where the solar cell 1 is normally used, the initial voltage V1 is set near the operating point at which the maximum power is output.

As a result, unlike the conventional case, the calculation or the like in the hill-climbing control is not required, so that it is possible to output approximately the maximum power with good response without the burden and time required for the calculation.

In view of the fact that the operating point for outputting the maximum power differs depending on the characteristics of the solar cell 1, the voltage comparator 3
1 to arbitrarily change the stored initial voltage V1 /
An initial voltage changing means 31a to be stored may be added. This makes it possible to easily respond to changes in the characteristics of the solar cell 1.

A constant voltage control level is set in advance, and control is performed based on the initial voltage V1 until the output level of the solar cell 1 exceeds the constant voltage control level. After the level is exceeded, the above-described hill-climbing control may be performed. At this time, solar cell 1
When the output power is used as the output level of the solar cell 1
The output power is calculated from the output voltage and the output power, or is calculated using a DC power meter.

Thus, when the voltage exceeds the constant voltage control level, the hill-climbing control is performed from the initial voltage V1, so that the time required to reach the maximum power output point Pmax can be reduced. Accordingly, it is possible to output a large amount of power from the solar cell 1 when the amount of solar radiation is large, and it is possible to avoid performing useless calculations when the amount of solar radiation is slightly small.

[Second Embodiment] FIG. 3 is a schematic configuration diagram of a solar inverter device. FIG. 4 is a graph showing voltage-power characteristics of the solar cell at each solar radiation.

The inverter device of this embodiment shown in FIG. 3 is different from the inverter device described with reference to FIG. 1 in the following structure.

That is, the configuration of the inverter control circuit 3 is different, and the value of the initial voltage can be appropriately changed based on the output power supplied from the solar cell 1.

The inverter control circuit 3 includes a voltage comparator 31 ′ for comparing the initial voltage set based on the output power with the output voltage of the solar cell 1, and a voltage comparator 31 ′ and a power comparator 37 described later. A current command value amplitude calculator 32 ′ for calculating the amplitude value of the current command value from the output result, a current command value phase calculator 33, a current command value calculator 34,
A controller 35, an output power calculator 36 for calculating output power from a voltage value and a current value output from the solar cell 1, a power comparator 37 for comparing the output power with two or more predetermined powers. It is composed of

Next, the operation of the inverter device according to the present embodiment will be described. As shown in FIG. 4, the inverter control circuit 3 performs control at initial voltages V2 and V3 that are lower than the open-circuit voltage V0. Note that the number of places for setting the initial voltage is not limited to two, and may be more than two.

The initial voltage V2 is set near the maximum power output operation point of the solar cell during low solar radiation, and the initial voltage V3 is set near the maximum power output operation point of the solar cell during higher solar radiation. When the output power is smaller than p2, control is performed at the initial voltage V2, and when the output power is p2 or more, control is performed at the initial voltage V3. It should be noted that which initial voltage is used when the output power indicates which value is arbitrarily set, but it is desirable that the lower the output power of the solar cell 1, the lower the initial voltage. Further, as described above, when the output power becomes p3 or more, the maximum power output point Pmax may be made to follow the conventional hill-climbing control.

As a result, unlike the related art, since the calculation or the like in the hill-climbing control is not required at least until the output power reaches p2, the load and time required for the calculation are not required, and the number of places where the initial voltage is set is increased. This allows the solar cell 1 to output as much power as possible. Also, in the case where the conventional hill-climbing method is used together, by performing hill-climbing control from the initial voltage V3, the calculation or the like conventionally performed until the voltage reaches the initial voltage V3 from the open voltage V0 becomes unnecessary. As a result, the time required to reach the maximum power output point Pmax is shortened, and the load on the arithmetic unit for performing the calculation can be reduced.

In view of the fact that the operating point for outputting the maximum power differs depending on the characteristics of the solar cell 1, the voltage comparator 3
An initial voltage changing means 31'a for arbitrarily changing / storing the initial voltages V2 and V3 stored in 1 'may be added. This makes it possible to easily respond to changes in the characteristics of the solar cell 1. When two or more initial voltages are set, it is needless to say that each of them can be changed / stored by the initial voltage changing means 31 '.

Note that the voltage-power characteristics of the solar cell 1 are different at the maximum power output point Pmax, and the maximum power is higher than when the operating point is changed from the side higher than the output voltage with respect to the maximum power output point Pmax. When the operating point is changed from the side lower than the output voltage with respect to the output point Pmax, the amount of power change with respect to the fixed change width ΔV becomes small. Therefore,
At the time of switching to the control following the maximum power output point Pmax, as shown in FIG. 4, when the output power becomes equal to or more than p3, a value V3 slightly higher than V3max which gives the maximum power operating point is used. If the initial voltage is set, it is possible to prevent the output voltage from greatly changing in response to a change in the output current of the solar cell 1.
As a result, even if noise is mixed in the output of the solar cell 1, the effect can be reduced.

[0034]

As described above, according to the first aspect of the present invention, an inverter main circuit for connecting a DC power supply output from a solar cell to a commercial power system, and an inverter control for controlling the inverter main circuit. In the inverter device including the circuit, the inverter control circuit controls the solar cell at a constant voltage based on a constant initial voltage, so there is no need to calculate the initial voltage. Inverter device that does not require time to reach the power output operating point, so that it is possible to shorten the time until it is possible to extract a large amount of power and to reduce the burden of calculating output power and the like. Is provided.

According to the second aspect of the present invention, the first aspect is provided.
In the solar inverter device described above, the inverter control circuit stores a plurality of initial voltages in advance and changes the initial voltage for performing the constant voltage control based on the output level of the solar cell. By changing the initial voltage on the basis of this, it is possible to set an initial voltage value at which a large amount of power can be finely extracted.

In the invention according to claim 3, claim 1 is
Alternatively, in the solar inverter device according to claim 2, since the inverter control circuit includes an initial voltage changing unit that can arbitrarily change a set value of the initial voltage, the initial voltage can be easily set based on the output characteristics of the solar cell. The effect that it becomes possible to change is produced.

In the invention according to claim 4, claim 1 is
4. The solar inverter device according to claim 3, wherein the inverter control circuit performs control based on the initial voltage until the output level of the solar cell exceeds a predetermined constant voltage control level, and exceeds the constant voltage control level. 5. After that, the hill-climbing control is performed to increase or decrease the correction voltage from the initial voltage so that the output of the solar cell becomes maximum, so that the time from the open voltage to reach the maximum power output operation point can be reduced. It has the effect that it becomes possible. In addition, within the range not exceeding the constant voltage control level, it is possible to reduce the burden of the calculation due to the hill-climbing control and to prevent the fluctuation of the operating point.

According to the fifth aspect of the present invention, there is provided the fourth aspect.
In the solar inverter device described above, the initial voltage at the time of switching from the constant voltage control to the hill-climbing control is set to a value higher than the voltage value at which the solar cell outputs the maximum power at the constant voltage control level as the initial voltage. Therefore, since the solar cell can be controlled in a region that is not easily affected by noise, there is an effect that the solar cell can be stably controlled.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a solar inverter device according to a first embodiment.

FIG. 2 is a graph showing voltage-power characteristics of a solar cell at each amount of solar radiation;

FIG. 3 is a schematic configuration diagram of a solar inverter device according to a second embodiment.

FIG. 4 is a graph showing voltage-power characteristics of a solar cell at each solar radiation.

FIG. 5 is a graph showing voltage-current characteristics and voltage-power characteristics of a solar cell.

FIG. 6 is a graph showing voltage-power characteristics of a solar cell at a certain amount of solar radiation;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solar cell 2 Inverter main circuit 3 Inverter control circuit 5 Commercial power system L Load 31, 31 'Voltage comparator 31a, 31'a Initial voltage changing means 32 Current command value amplitude calculator 33 Current command value phase calculator 34 Current command Value calculator 35 PWM controller 36 Output power calculator 37 Power comparator

Continuing on the front page (72) Inventor Hiroaki Koshin 1048, Ojimon Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Works, Ltd. Inventor Hirotada Higashihama 1048 Kadoma Kadoma, Kazuma, Osaka Prefecture F-term in Matsushita Electric Works, Ltd. (reference) FF03 FF04 FF22 FF25 FF26

Claims (5)

[Claims] 1. An inverter device comprising: an inverter main circuit for connecting a DC power supply output from a solar cell to a commercial power system; and an inverter control circuit for controlling the inverter main circuit. A solar inverter device wherein constant voltage control of a solar cell is performed based on a voltage. 2. The solar battery according to claim 1, wherein the inverter control circuit stores a plurality of initial voltages in advance, and changes the initial voltage for performing the constant voltage control based on the output level of the solar cell. Optical inverter device. 3. The solar inverter device according to claim 1, wherein the inverter control circuit includes an initial voltage changing unit that can arbitrarily change a set value of the initial voltage. 4. An inverter control circuit controls the output of the solar cell based on the initial voltage until the output level of the solar cell exceeds a predetermined constant voltage control level. 4. The solar inverter device according to claim 1, wherein hill-climbing control for increasing or decreasing the correction voltage with respect to the initial voltage is performed so as to be maximum. 5. An initial voltage at the time of switching from constant voltage control to hill-climbing control, a value higher than a voltage value at which the solar cell outputs maximum power at the constant voltage control level is set as an initial voltage. The solar inverter device according to claim 4, wherein