JPH05157330A - Control circuit for output power from solar cell - Google Patents

Abstract

PURPOSE:To utilize natural energy effectively by supplying an air conditioner with the maximum power of a solar cell from the solar cell and supplying a shortage power from a commercial system power supply when the power consumption of the air conditioner is larger than output power from the solar cell. CONSTITUTION:A power control circuit 1 converts DC power into voltage and currents regarding an output from a solar cell 2. The AC power of a commercial power supply 6 is transmitted over a VVVF inverter 7 through a voltage doubler rectifier circuit 4 in an inverter air conditioner 3, and a compressor 8 is driven in response to power from each circuit 1, 4 by the inverter 7. The power control circuit 1 has a followup value control section 21 for following the maximum point of output voltage from the solar cell, changes over an FET bridge 12 by a pulse signal at a duty ratio corresponding to an output from the followup value control section 21, when output voltage from the solar cell is smaller than the power consumption of the air conditioner, and increases output voltage from the power control circuit 1 up to a value corresponding to the maximum output power of the solar cell. When power consumption is larger than the maximum power of the solar cell, a shortage section is supplied from the commercial system power supply.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell output power control circuit, and more particularly to a solar cell output power control circuit for use in a commercial power combined air conditioner using a solar cell.

[0002]

2. Description of the Related Art A commercial power combined air conditioner using a solar cell is a combination of a solar cell and an inverter air conditioner, and the output from the solar cell is a DC circuit which is the latter stage of a voltage doubler rectifier circuit of the inverter air conditioner. Connect to the
The electric power from the solar cell and the electric power from the commercial system power supply are used together and supplied to the VVVF inverter of the inverter air conditioner. It should be noted that the power from the solar cell will not flow back to the commercial power supply by the voltage doubler rectifier circuit of the air conditioner. In these devices, conventionally, a method has been proposed in which the number of solar cells connected in series is determined so that the output voltage value matches the voltage of the DC circuit section of the air conditioner, and the output of the solar cell is directly connected to the DC circuit section of the air conditioner. Has been done.

However, as is well known, the output power of a solar cell greatly changes depending on its operating voltage value, and the maximum power can be output only at an arbitrary one voltage value. Moreover, the voltage value changes depending on weather conditions such as the amount of solar radiation and temperature. In the above-described method, the solar cell operating voltage fluctuates at an unpredictable voltage value due to the constantly changing load characteristics of the air conditioner or the voltage fluctuation of the commercial system power source, so the output of the solar cell is effectively extracted for the above reason. This is impossible, and as a result, an excessive solar cell capacity is required, resulting in high cost.

On the other hand, a DC-DC converter is provided between the DC circuit section of the inverter air conditioner and the solar cell output, and the output voltage of the converter is adjusted to the voltage of the DC circuit section of the air conditioner, and its input voltage, that is, the solar voltage. It employs a method of controlling the output voltage from the battery to a preset constant voltage value. The feature of this method is that the operating voltage at which the maximum electric power of the solar cell can be extracted varies from moment to moment depending on the weather conditions (solar radiation, element temperature), but it is almost independent of the solar radiation and element temperature. This is a point where it is attempted to operate artificially at the maximum output point of the solar cell, assuming that it can be approximated to an arbitrary constant voltage.

From the above, it is naturally expected that the above-mentioned system performs open-loop control in terms of control, and the voltage value predicted in advance does not match the operating voltage value at which the actual maximum output can be obtained. In this case, it operates at a point deviating from the optimum operating point, and therefore, due to the characteristics of the solar cell, even if the operating point deviates even a little, especially when the amount of solar radiation becomes high to some extent, a large amount of power is wasted. .. Moreover, since the above-mentioned optimum operating point changes depending on the season, considering heating in winter and dehumidification during rainy seasons throughout the year, this method requires complicated changes such as frequent change of a preset voltage value. Without operation, a large amount of solar cell output power will be wasted throughout the year, which is inefficient and not very useful.

Further, in a device in which a load other than an air conditioner is combined with a solar cell, the output power of the solar cell is actually detected, and the solar cell is output along the output characteristic curve of the solar cell so that the output becomes maximum. Closed-loop control is also performed in which the maximum output point is found by changing the operating point, and operation is performed at that point. However, these conventional methods are not always excellent in control characteristics, and the voltage swing is large near the operating voltage at which the maximum power can be taken out, and moreover, it is operated only near the maximum point. No attempt has been made to control the solar cell output according to the load power consumption.

[0007]

A major feature of solar cells is that their output greatly depends on weather conditions.
It is not possible to always supply power from a solar cell according to the load power consumption such as an air conditioner that constantly changes depending on the set temperature set by the user and the outside air temperature. That is, there is always a magnitude relationship between the solar cell output power and the load power consumption, which causes a shortage of power required by the load and surplus power not required by the load.

Therefore, the main object of the present invention is to make up for the solar cell maximum output point tracking control and the solar cell operating voltage, which are excellent in control performance, by compensating for the drawbacks in the conventional solar cell utilizing air conditioner. It is an object of the present invention to provide a solar cell output power control circuit capable of controlling increase and decrease of battery output power.

[0009]

The invention according to claim 1 is a power control circuit which is inserted between a solar cell and an inverter air conditioner and which supplies output power from the solar cell to a DC circuit portion of the inverter air conditioner. The additional value control means for tracking the maximum point of the voltage output from the solar cell, the constant value control means for keeping the output voltage of the power control circuit constant, and the duty ratio according to the additional value control means output. Pulse signal generating means for generating a second pulse signal having a duty ratio according to the output of the first pulse signal and constant value control means, and switching means for switching and outputting the first and second pulse signals, Switching means for switching the output power from the solar cell and supplying it to the DC circuit portion in accordance with the first or second pulse signal output from the switching means, and the DC circuit portion It is connected, and an output capacitor for temporarily storing the excess power from the solar cell.

In the invention according to claim 2, the additional value control means of the invention according to claim 1 obtains the output power according to the output voltage and the output power of the power control circuit, and determines the control voltage at which the output power becomes maximum. The pulse signal generating means includes a calculating means for calculating, and generates the first pulse signal having a duty ratio according to the control voltage output from the calculation state.

In the invention according to claim 3, the constant value control means of claim 1 includes error voltage detection means for detecting an error voltage with respect to the output voltage of the reference voltage power control circuit, and the pulse signal generation means includes the error voltage detection means. The duty ratio of the second pulse signal is increased in response to the large error voltage output from.

[0012]

The solar cell output power control circuit according to the present invention is
When the power consumption of the air conditioner is larger than the output power of the solar cell, the solar cell supplies the maximum power that can be output to the air conditioner at that time, and controls the shortage to be supplied from the commercial system power supply. Therefore, when the output power of the solar cell is smaller than the power consumption of the air conditioner, a pulse signal with a duty ratio corresponding to the control voltage output of the tracking value control means for tracking the maximum point of the output power of the solar cell is generated. Switching the switching means to match the input voltage of the power control circuit with the operating voltage of the solar cell that can output the maximum power at that time, and at the same time, set the output voltage of the power control circuit to a value commensurate with the maximum output power of the solar cell. To raise.

When the output power of the solar cell is larger than the power consumption of the air conditioner, the solar cell output power changes according to the operating voltage as shown in the operating voltage-output power characteristic of the solar cell of FIG. A pulse signal with a duty ratio according to the control voltage output of the control means is generated, and constant value control is performed to keep the output voltage of the power control circuit constant according to the pulse signal. Along the top, the output voltage is moved to the open voltage so that the output of the solar cell and the power consumption of the air conditioner are controlled to be equal.

[0014]

1 is a block diagram of an embodiment of the present invention. Referring to FIG. 1, power control circuit 1 is connected between solar cell 2 and inverter air conditioner 3, and power control circuit 1
Is connected to the DC circuit section 5 at the subsequent stage of the voltage doubler rectifier circuit 4 included in the inverter air conditioner 3. The power control circuit 1 converts the DC power output from the solar cell 2 into voltage and current. On the other hand, AC power is applied from the commercial power supply 6 to the outlet 9, and the AC power is AC-DC converted by the voltage doubler rectifier circuit 4 and applied from the DC circuit unit 5 to the VVVF inverter 7. The VVVF inverter 7 supplies DC-AC converted power to the compressor 8 of the inverter air conditioner 3 which is a load in accordance with the power supplied from the power control circuit 1 or the DC power converted by the voltage doubler rectifier circuit 4 into DC. To do.

The power control circuit 1 includes an input capacitor 11 for suppressing fluctuations in input power from the solar cell 2, an FET bridge 12 composed of one or more power MOSFETs as a switching element, and a high frequency transformer 13.
An output rectifying diode 14, a smoothing capacitor 15 forming an output filter circuit, and an output choke coil 1
6, output capacitor 17, backflow prevention diode 19
And a noise filter 20 connected to the input / output portion to prevent noise generated in the power control circuit 1 from flowing out to the outside, and a control circuit 18. The control circuit 18 includes an additional value control unit 21, a constant value control unit 22, a PWM signal generation / switching unit 23, a soft start control unit 24, and a power supply unit 25.

Next, the operation will be described. As will be described in detail later with reference to FIG. 9, the control circuit unit 18 turns on / off the FET bridge 12 by the duty ratio controlled PWM gate pulse signal,
VV is controlled by controlling the input voltage of the power control circuit 1, that is, the operating voltage of the solar cell 2 and the output voltage of the power control circuit 1.
The output power of the solar cell 2 is supplied to the VF inverter 7.
That is, when the FET bridge 12 is turned on, the voltage of the solar cell 2 is applied to the primary winding N _F of the high frequency transformer 13, and the voltage is induced in the secondary winding N _S. This voltage biases diode 14 in the positive direction, so diode 1
4, a current flows through the path for charging the output choke coil 16 and the smoothing capacitor 15.

Next, when the FET bridge 12 is turned off,
The transmission of power from the primary side of the transformer 13 is stopped, counter electromotive force is generated in the output choke coil 16, and current flows through the choke coil 16, the smoothing capacitor 15, and the diode 14. Here, the average current flowing through the primary side of the transformer of the power control circuit 1 is expressed by the following equation (1).

I _IN = V _IN · T _ON ² / (2 · N ² · L) / T _S (1) where V _IN : solar cell operating voltage T _ON : power MOSFET on time N: transformer winding ratio L: Inductance of choke coil 15 T _S : Switching cycle From the above-mentioned expression (1), the input impedance Z _IN from the solar cell 2 side of the power control circuit 1 can be expressed by the following expression (2).

Z _IN = V _IN / I _IN = 2 · N ² · L · T _S / T _ON ² = 2 · N ² · L / (T _S · D ² ) ... (2) D = T _ON / T _S (D is the duty ratio) where N is the transformer turns ratio, L is the inductance value of the choke coil, T _S is the switching period, and these values are fixed values determined at the time of circuit design. .. Therefore, it can be seen from the formula (2) that the input impedance Z _IN of the power control circuit 1 viewed from the solar cell 2 side changes depending on the duty ratio D.

FIG. 3 is a diagram showing the duty ratio of the power control circuit shown in FIG. 1 and the output characteristics of the solar cell.

As is apparent from the above equation (2), by controlling the duty ratio D, the voltage-current characteristic of the solar cell 2, that is, the voltage-current characteristic curve of the solar cell 2 is shown in FIG. The operating voltage of can be controlled by any voltage. That is, the operating voltage V _IN and the operating current I _IN of the solar cell can be varied by the duty ratio D as follows.

The operating point at the operating voltage V _IN of the solar cell is determined by the duty ratio D of the power control circuit 1 as shown in FIG. That is, the duty ratio is changed from Da to
When Db → Dc (Da <Db <Dc) is changed, the operating point of the solar cell moves from a → b → c, and the operating voltage is V
Move a, Vb, Vc.

On the other hand, the power control circuit 1 outputs its output voltage V
The output of the solar cell 2 is supplied to the VVVF inverter 7 of the inverter air conditioner 3 by giving priority to the system power supply by increasing _OUT . This is a control method using the regulation of the input voltage-current characteristics of the VVVF inverter 7, and the VVVF inverter 7 of the inverter air conditioner 3 is provided with a system power supply (AC100V) and a voltage doubler rectifier circuit 4.
DC voltage (220V to 300VDC) rectified by double voltage
Is being applied.

FIG. 4 is a diagram showing the regulation characteristic of the VVVF inverter. As is apparent from FIG. 4, the input voltage-current characteristic is such that the input voltage decreases as the input power (load power consumption) increases. Has regulation. Therefore, in the case where the system power supply voltage and the load current are constant, that is, when the VVVF inverter 7 is operated by receiving 100% power from the commercial system power supply 6 at the point A _{0 in} FIG. The input voltage of the inverter is V ₀ ) and the output power of the solar cell 2 is V
In order to supply the VVF inverter 7, the regulation characteristic of the VVVF inverter 7 is used to output the output voltage of the current control circuit 1 from the voltage V ₀ at the point A ₀ as shown in FIG.
By setting the higher voltage V _OUT = V ₁ .
As shown in, the output of the solar cell 2 can be supplied to the VVVF inverter 7 instead of the commercial system power supply 6. The higher the output voltage of the power control circuit 1 is, the more the power supply amount (load sharing rate) from the power control circuit 1 is increased. Further, when the output voltage of the power control circuit 1 becomes equal to the inverter input voltage when V _OUT = V ₂ , that is, when the power supply from the commercial grid power supply 6 is 0 V, all load power is replaced with the commercial grid power supply 6. Will be covered by the output power of the solar cell.

Here, the output voltage V _OUT of the power control circuit 1
Is determined by the following equation (3) using the above-mentioned duty ratio D.

V _OUT = N · V _IN · D (3) V _OUT : Output voltage of power control circuit V _IN : Operating voltage of solar cell 2 N: Transformer winding ratio In the above formula (3), winding Since the line ratio N is a constant value determined when the circuit is designed, it can be seen that the output voltage V _OUT is determined by the duty ratio D and the input voltage V _IN . However, the input voltage V _{IN is} also determined by the duty ratio D, as shown in FIG. Therefore,
The output voltage V _{OUT is} also controlled by the duty ratio D similarly to the operation line in the voltage-current characteristic of the solar cell 2 described above. However, from the equation (3), the output voltage V _OUT rises when the duty ratio D is increased, but conversely, the input voltage V _IN is lowered when the duty D is increased as shown in FIG. Therefore, by making the output voltage V _OUT the highest, the maximum output power of many solar cells 2 is VVV.
In order to determine the duty ratio D that can be supplied to the F inverter 7, feedback control in which an increase / decrease in power due to an increase / decrease in duty ratio D is detected and a duty ratio that can supply more power is determined, that is, a closed loop additional value Need to take control.

This additional value control is realized as follows. That is, the operating points a, b, c of the solar cell 2 in FIG.
When the operating voltage in the power control circuit 1, that is, the input voltage of the power control circuit 1 is Va, Vb, and Vc, respectively, the output voltages Va ′, V of the power control circuit 1 corresponding to this can be calculated from the equation (3).
b'and Vc 'are as follows.

Va '= NDaVa Vb' = NDbVb Vc '= NDcVc Now, when the duty ratio changes from Da to Dc, the duty ratio change amount ΔD is input. Voltage change ΔV _IN
Is small, the duty ratio D increases (Da <Db
Due to <Dc), the output voltage of the power control circuit 1 is also Va ′>
Vb '>Vc' rises.

FIG. 6 is a diagram showing the output voltage and output power characteristic of the power control circuit shown in FIG. 1, FIG. 7 shows the same duty ratio and output power characteristic, and FIG. 8 shows the duty ratio of the power control circuit 1. It is a figure which shows the output characteristic of a solar cell.

As shown in FIG. 6, the power control circuit 1 outputs more power to VVVF by increasing the output voltage V _OUT.
Attempt to supply to the inverter 7. But solar cell 2
Due to the characteristics of the power supply, there is a limit to the power that can be output. That is, there is a relationship shown in FIG. 7 between the duty ratio and the output power of the solar cell 2 (power control circuit output). By increasing the duty ratio Da → Db → Dc, the output of the power control circuit 1 is also increased. There is a duty ratio Dc that increases as Pa <Pb <Pc, but the output power does not increase even if the duty ratio is further increased. That is, when the duty ratio D is increased more than this, the above-mentioned duty ratio D
In the relationship between the input voltage V _IN and the input voltage V _IN , the change amount ΔV _{IN of the} input voltage becomes larger than the change amount ΔD of the duty ratio D. In this case, the duty ratio D
The output voltage V _OUT of the power control circuit 1 decreases with an increase in the output power, and as a result, the output power of the power control circuit 1 also decreases. From this, the output Pc of the power control circuit 1 at the above-mentioned duty ratio Dc becomes the maximum supplyable power of the VVVF inverter 7, and at the same time, the operating point of the solar cell 2 determined by the duty D is the maximum output of the solar cell 2. It becomes a point.

Therefore, as an example of a method for controlling the duty ratio D to the above-mentioned duty Dc, in the power control circuit 1 of the embodiment of the present invention, the output of the solar cell 2 (solar cell voltage-current characteristic) is In consideration of the fact that the output voltage and output current of the circuit are significantly changed, the output power is obtained by taking into account the fact that the output voltage and the output current of the circuit greatly vary, and feedback control is performed to determine the duty ratio D so that the output power is always maximized. There is.

Specifically, the duty ratio D is slightly changed by ΔD in an increasing direction or a decreasing direction. as a result,
If the output power increases, the duty ratio D is further decreased by ΔD in the same direction. On the contrary, if it decreases, it changes by ΔD in the opposite direction. In this way, the control is made to follow the duty ratio D at which the output power becomes maximum.
In this example, the control is realized by the additional value control unit 21 shown in FIG. 1 using a microcomputer. Through the series of operations described above, the power control circuit 1 increases the circuit output voltage by controlling the duty ratio, and supplies the VVVF inverter 7 with the maximum output that can be taken out from the solar cell 2 while tracking the maximum output point of the solar cell 2. be able to.

On the other hand, when the former is smaller than the latter due to the relationship between the maximum output power of the solar cell 2 and the load power, surplus power is generated when the maximum point tracking of the solar cell 2 is performed. Therefore, this time, by moving the operating voltage of the solar cell 2 from the voltage value at which the maximum output is obtained to the open voltage side,
It is necessary to reduce the output power and control it so that it becomes equal to the load power at that time. The control method will be described below. In FIG. 5 described above, consider a state in which the output voltage of the power control circuit 1 rises to V _OUT = V ₂ and all the load power is supplied by the output power of the solar cell 2 instead of the commercial system power supply 6. Then, in this state, the maximum output power of the solar cell 2 is balanced with the load power. If the amount of solar radiation increases even a little from this state and the output of the solar cell 2 increases accordingly, the output of the solar cell 2 becomes larger than the load power if the maximum output point is being tracked as it is.

Here, the output of the solar cell 2 is directly connected to the load, and the surplus power has no other place to go. For this reason,
The load power consumption (operating power of the air conditioner) varies depending on the output of the solar cell 2. Abnormal voltage is generated, which adversely affects circuit components. This causes various problems and problems. Therefore, in order to solve these problems, the output power of the solar cell 2 is controlled so that the output of the solar cell 2 becomes equal to the load power by moving its operating point.

In FIG. 5, the output voltage of the power control circuit 1 rises to V _OUT = V ₂ , and instead of the commercial system power source 6,
When the output of the solar cell 2 further increases from the state where all the load power is supplied by the output power of the solar cell 2, the excess power is charged in the output capacitor 17.
The output voltage is V depending on the charging voltage of the output capacitor 17.
Trying to rise further than ₂ . Output voltage is V _CONST
When the voltage rises up to, the output voltage constant control is switched to the constant control with this voltage V _CONST . This control controls the duty ratio D so that the output voltage is kept constant.

That is, when the output of the solar cell 2 becomes large or the load power becomes small, the surplus power is temporarily charged in the output capacitor 17 provided as a buffer. Then, the output voltage tends to rise due to this charging voltage. However, the output voltage is kept constant by controlling the output voltage to a constant value so that the duty ratio D is reduced so as to prevent the output voltage from rising. Here, when the output voltage is constant according to the equation (2), which is an expression of the relationship between the output voltage, the input voltage, and the duty ratio, when the duty ratio D is decreased, the input voltage V _IN increases and the operation of the solar cell 2 increases. The point moves along the voltage-current characteristic curve to the open-circuit voltage side until the output power of the solar cell 2 and the load power become equal.

FIG. 8 is a diagram showing the duty ratio and solar cell output characteristics of the power control circuit according to one embodiment of the present invention.
The above operation will be described with reference to FIG. 8. When the sunshine intensity is E, the solar cell array outputs the maximum output point (Bi
Point), and the power control circuit 1 indicates B in FIG.
At point o (output voltage V ₂ ) (solar cell maximum output) =
It is assumed that the vehicle is operating in the (load power) state. here,
If the intensity of solar radiation increases to E → E ′ (E <E ′), the power control circuit 1 supplies a larger amount of power to the VVVF inverter 7, which is a load, because the power that can be output from the solar cell 2 increases. be able to.

However, the negative of the VVVF inverter 7
Since the load power is affected by the indoor and outdoor temperatures and the set temperature,
Therefore, the increase in solar radiation is
It does not directly affect the load power. Therefore, the surplus electricity
The force is temporarily charged to the output capacitor 17. That
Then, the output voltage of the power control circuit 1 is V due to this charging voltage.
₂To V_CONSTUp steeply to
Try to. Here, the output voltage constant control works and the output voltage is
Suppresses the rise of pressure, V_CONSTDuty to keep constant
In the direction of decreasing the ratio D, like D → D '(D> D')
Control. At this time, the operating point of the solar cell 2 is from the Bi point
Move to the Bi 'point where the following equation (4) holds.
The solar cell 2 moves from the maximum power point to the open-circuit voltage side.
Output power drops to a point where it matches the load power.

V _CONST = N · D · Vb = N · D ′ · Vb ′ (4) Here, D> D ′, Vb <Vb ′ Contrary to the above description, the sun in a state where the amount of solar radiation does not change Similarly, when the load power becomes small when the output of the battery 2 is constant and the relationship between the output of the solar cell 2 and the load power is reversed, the surplus power is temporarily charged in the output capacitor 17 as well. Do the same. When the maximum output of the solar cell array becomes larger than the required power of the inverter by such control operation, the operating point of the solar cell array is shifted from the maximum output point, and the output from the solar cell 2 side and the required inverter power are increased. Are controlled to be equal.

Here, the regulation characteristic of the input voltage-current characteristic of the VVVF inverter 7 shown in FIG. 4 changes in the vertical direction as shown in FIG. 4 due to the voltage fluctuation (90 V to 110 V) of the commercial system power supply 6. .. Therefore, the power control circuit 1 in which V ₀ shown in FIG. 5, that is, all the load power is supplied by the output power of the solar cell 2
Output voltage V _OUT = V ₂ changes according to the voltage fluctuation of the commercial system power supply 6. Therefore, the V _CONST value in the constant output voltage control needs to be set to a value higher than at least the maximum value of the inverter input voltage at the maximum voltage of the system voltage (110 V) (the inverter input voltage at the time of load). By doing so, the above-mentioned control is performed even with respect to the fluctuation of the system voltage, that is, by increasing the output voltage of the power control circuit 1, the solar cell output power is replaced with the commercial system power supply 6, and the VVVF inverter 7 serving as a load. It is possible to realize the control of supplying to.

FIG. 9 is a specific block diagram of the control circuit shown in FIG. The control circuit 18 includes an additional value control unit 21, a constant value control unit 22, a PWM signal generation / signal switching unit 23, and a soft start control unit 24. The additional value control unit 21 is mainly A
/ D converter 43, CPU 44, D / A converter 4
5, the maximum output point of the solar cell 2 is tracked as described above. Therefore, as shown in FIG. 1, the additional value control unit 21 is provided with an output voltage signal (a voltage signal proportional to the output voltage) from one end of the output converter 17, and an output current signal (output) from the shunt. Voltage signal proportional to current)
And are given. These signals are A / D converter 43
The analog signal is converted to a digital signal by the CP
Given to U44. The CPU 44 obtains the output power according to a flow chart shown in FIG. 10 described later, always calculates a control voltage that maximizes the output power, and outputs the control voltage signal a as an analog signal via the D / A converter 45. .

The constant value control unit 22 is mainly composed of an error amplifier 41 and a reference voltage 42, and the output voltage is the reference voltage from the error signal of the output voltage signal, the reference voltage, and the constant voltage set value V _CONST for the constant output voltage control. The control voltage signal b for controlling so as to match The PWM signal generation / signal switching unit 23 is mainly composed of the ramp waveform circuit 46 and the comparator 4.
7 and 48, an AND gate 49, and a pulse distributor 50.

The PWM signal generating / signal switching unit 23 outputs the control voltage signals a and b output from the additional value control unit 21 and the constant value control unit 22, respectively, from the sawtooth waveform output from the same ramp waveform circuit 46 and the comparator 47. , 48 to generate a PWM signal having a duty ratio proportional to the voltage level of each control voltage signal. These two PWM signals are transferred to the AND gate 49 of the next stage.
The PWM signal with the smaller duty ratio (smaller pulse width) is selected.
It is output from the ND gate 49.

Here, which signal is selected at which time, when the load power is larger than the maximum output of the solar cell 2 and the maximum point tracking control of the solar cell 2 is performed, , The output voltage of the power control circuit 1 is the reference voltage V
_Since it has not reached _CONST , the control voltage signal from the constant value control unit 27 is output at the maximum value, and the pulse width (duty ratio) of the PWM signal also becomes maximum. As a result, in the above-described case, the AND gate 49 selects the PWM signal having the smaller pulse width, that is, the signal from the additional value control unit 21.

On the other hand, when the relationship between the maximum output of the solar cell 2 and the load power is reversed, the control voltage signal from the additional value control unit 21 has a margin in the electric power from the solar cell, so the voltage level is raised to increase the PWM signal. Try to increase the pulse width. On the other hand, since the output voltage reaches the reference voltage V _{CO NST} , the signal from the constant value control unit 22 lowers the voltage level of the control voltage signal in order to prevent the output voltage from becoming higher than the reference voltage, so that the PWM pulse width is reduced. And

As a result, the AND gate 49 selects the signal from the constant value control unit 22. Further, the pulse distributor 50 distributes the PWM signal from the AND gate 49 into two gate pulse signals 1, 2 and outputs them to the FET bridge 12 which alternately switches.

As described above, the PWM signals determined by the additional value control unit 21 and the constant value control unit 22 are automatically switched when the output voltage of the power control circuit 1 reaches the reference voltage _CONST . That is, the solar cell output control by switching the maximum point tracking control and the constant output voltage control described above can be realized using the control circuit 18. The soft start control unit 24 shown in FIG. 9 performs soft start control by gradually increasing the ON time of the PWM signal when the circuit is activated. The gate pulse OFF signal shown in FIG. 9 is an input for externally forcibly stopping the operation of the circuit.

FIG. 10 is a flow chart for explaining the operation of the CPU shown in FIG. Referring to FIG. 10, CPU
The operation of 44 will be described. When the power is turned on, C
The registers and the like in the PU 44 are reset and initialized. After setting the control voltage to the minimum value, the CPU 44 increases the control voltage. The CPU 44 outputs this control voltage as 8-bit data (00H to FFH) to the D / A converter 45, and the D / A converter 45 outputs the data as an analog voltage to the comparator 48. Figure 1
The output voltage signal from the output capacitor 17 and the output current signal from the shunt shown in (4) are converted into digital signals by the A / D converter 43 and taken into the CPU 44. C
The PU 44 multiplies the input voltage and the input current to obtain the input power.

The CPU 44 determines whether or not the input voltage has decreased.
That is, it is determined whether the voltage of the solar cell 2 has dropped,
If the input voltage has not decreased, decrease the control voltage.
The CPU 44 determines whether or not the input power has increased, and if not, lowers the control voltage. Furthermore, CPU4
4 determines whether the control voltage is increasing, and if it is increasing, it is determined whether the control voltage is maximum.
If it is not the maximum value, the control voltage is increased by one unit, and if it is the maximum value, it is decreased by one unit. On the contrary, if the control voltage has not increased, it is determined whether it is the minimum value, and if it is the minimum value, the control voltage is increased by one unit, and if it is not the minimum value, it is decreased by one unit.

[0050]

As described above, according to the present invention, the DC output of the solar cell can be effectively used by connecting to the DC circuit of the inverter air conditioner, and the natural energy of the electric power from the solar cell can be effectively used. When the natural energy is low, it is supplemented with electric power from the commercial grid power supply, and when the natural energy is high, the electric power is appropriately controlled. It is possible to provide usability as before without being aware of the distinction between power from the grid power supply.

In addition, under the weather environment where the air conditioner needs to be operated (during summer daytime), the natural energy from the solar cell can be expected to have a sufficient output.
The air conditioner can be operated without being conscious of energy (electricity bill) waste, and a more comfortable living environment can be provided. Even from the power supply side, the widespread use of the present invention can provide the effect of suppressing the peak power consumption especially during the daytime in summer. Therefore, a great effect can be expected for both a power demander and a supplier, and also a great effect can be expected for the global environment by using environmentally friendly natural energy.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing operating voltage-output power characteristics of a solar cell.

FIG. 3 is a diagram showing a duty ratio and an output characteristic of a solar cell in the power control circuit of the present invention.

FIG. 4 is a diagram showing a regulation characteristic of a VVVF inverter.

FIG. 5 is a diagram showing a current supply sharing characteristic of the current control circuit of the present invention and a commercial system power supply.

FIG. 6 is a diagram showing output voltage and output power characteristics of the power control circuit of the present invention.

FIG. 7 is a diagram showing the duty ratio and output power characteristics of the power control circuit of the present invention.

FIG. 8 is a diagram showing the duty ratio of the power control circuit of the present invention and the output characteristics of the solar cell.

9 is a control block diagram of the power control circuit shown in FIG. 1. FIG.

10 is a flowchart for explaining the operation of the CPU shown in FIG.

[Explanation of symbols]

 1 Power Control Circuit 2 Solar Cell 3 Inverter Air Conditioner 4 Double Voltage Rectifier Circuit 6 Commercial Power Supply 7 VVVF Inverter 11 Input Capacitor 12 FET Bridge 13 High Frequency Transformer 14 Output Rectifying Diode 15 Smoothing Capacitor 16 Output Choke Coil 17 Output Capacitor 18 Control Circuit 21 Additional value control unit 22 Constant value control unit 23 PWM signal generation and signal switching unit 24 Soft start control unit 41 Error amplifier 42 Reference voltage 43 A / D converter 44 CPU 45 D / A converter 46 Ramp waveform circuit 47, 48 Comparator 49 AND gate 50 pulse distributor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsukasa Takebayashi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Co., Ltd. Co., Ltd. (72) Inventor Yoshikazu Kouwa 3-3-22 Nakanoshima, Kita-ku, Osaka City Kansai Electric Power Co., Ltd. (72) Inventor Shigeru Omori 3-3-22 Nakanoshima, Kita-ku, Osaka City Kansai Electric Power Co., Ltd. Within

Claims (3)

[Claims] 1. A power control circuit inserted between a solar cell and an inverter air conditioner for supplying output power from the solar cell to a DC circuit portion of the inverter air conditioner, wherein a voltage output from the solar cell is Additional value control means for tracking the maximum point, constant value control means for making the output voltage of the power control circuit constant, first duty having a duty ratio according to the output of the additional value control means
Pulse signal and a pulse signal generating means for generating a second pulse signal having a duty ratio according to the output of the constant value control means, a switching means for switching and outputting the first and second pulse signals, and the switching means. Switching means for switching the output power from the solar cell and supplying it to the direct current circuit part in response to the first or second pulse signal output from the solar cell, and the solar cell connected to the direct current circuit part. Solar cell output power control circuit equipped with an output capacitor that temporarily stores excess power from the solar cell. 2. The additional value control means includes calculation means for calculating output power according to an output voltage and an output current of the power control circuit, and calculating a control voltage at which the output power is maximum, the pulse signal The solar cell output power control circuit according to claim 1, wherein the generating means includes means for generating a first pulse signal having a duty ratio according to the control voltage output from the computing means. 3. The constant value control means includes error voltage detection means for detecting an error voltage between a reference voltage and an output voltage of the power control circuit, and the pulse signal generation means outputs from the error voltage detection means. The solar cell output power control circuit according to claim 1, further comprising means for changing a duty ratio of the second pulse signal according to the magnitude of the error voltage.