JPH10289025A - Power conditioner for solar power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a power conditioner from being destroyed by the excess of the withstand voltage of inner parts by controlling input voltage on solar battery output to be not more than the upper limit value of an operation voltage range and directly inputting input voltage to an inverter circuit without boosting it in a boosting circuit. SOLUTION: This power conditioner 1 is constituted only of a smoothing capacitor C1, a power conditioner control part 2 and the inverter circuit 4 and it does not have the boosting circuit. High input voltage can be supplied to the power conditioner 1 from a solar battery E. The input voltage of the solar battery E, which is smoothed in the smoothing capacitor C1, is given to the inverter circuit 4. Thus, the input voltage of the solar battery E can be made high by controlling input voltage to be not more than the upper limit value of the operation voltage range. Thus, input voltage can directly be inputted to the inverter circuit 4. Then, cost can be reduced by improving power conversion efficiency and reducing the parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a power conditioner in a photovoltaic power generation system.

[0002]

2. Description of the Related Art While a distributed power source and a commercial power source are connected to each other by a photovoltaic power generator, power is supplied to home appliances by the photovoltaic power generator, and excess power is supplied to the power system in reverse.
There is a photovoltaic power generation system that supplies power from the grid when power is insufficient with only photovoltaic power generation. In such a system, a solar cell that converts sunlight energy into electric energy, a junction box including a diode and a switch that prevents output from the solar cell from flowing back to the solar cell side, It has a power converter (inverter circuit) for converting DC power into AC power synchronized with the commercial power supply, and a protection device for detecting abnormality of the commercial power supply. It is called Na.

As shown in FIG. 9, a power conditioner 1 interposed between a solar cell E and a commercial power system P includes a smoothing capacitor C1, a power conditioner control unit 2, a booster circuit 3, and an inverter circuit 4. Have been.
In the photovoltaic power generation system using such a power conditioner 1, in order to draw the output of the solar cell E installed outdoors to the interior of the vehicle via the wiring, the output voltage is set to be equal to or lower than the wiring voltage defined by the indoor wiring regulations. While needing
In order to connect with the commercial power system P, the booster circuit 3 for boosting the wiring voltage to be higher than the wiring voltage for the direct-to-direct power conversion in the power conditioner 1 is an essential element. There is a problem such as an increase in cost. By the way, the above-mentioned indoor wiring regulation is currently scheduled to be revised in a direction in which the voltage of the indoor wiring is increased. It is not necessary to perform the conversion, and the booster circuit 3 may be omitted to eliminate the above problem.

[0004]

However, a problem that arises when the booster circuit 3 is omitted is that the output of the solar cell E is increased by the boosted voltage of the booster circuit 3, so that an abnormality occurs in the system and the solar cell E When the power conditioner is disconnected from the power system and becomes a no-load state, the conventional power conditioner 1 has no means for limiting the output voltage, and the output voltage rises above the withstand voltage of components such as the smoothing capacitor C1 in the power conditioner 1. Therefore, there is a problem that the power conditioner 1 is destroyed.

In view of the above-mentioned revision, the present invention is designed to limit the output of the solar cell to a certain voltage or less when omitting the booster circuit. An object of the present invention is to provide a power conditioner capable of restarting the operation in a stable manner.

[0006]

In a power conditioner according to the present invention, an input voltage related to a solar cell output is controlled to be equal to or less than an upper limit value of an operating voltage range by a power conditioner control unit for controlling an operation of an inverter circuit. The above-mentioned problem is solved by making it possible to increase the input voltage and directly input the input voltage to the inverter circuit without boosting the input voltage by a booster circuit.

[0007]

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

FIG. 1 is a circuit diagram of a transformerless power conditioner in a photovoltaic power generation system according to a first embodiment of the present invention. Referring to FIG. The conditioner 1 includes only a smoothing capacitor C1, a power conditioner control unit 2, and an inverter circuit 4 and does not have a booster circuit. On the other hand, in the power conditioner 1, a high input voltage from the solar cell E is possible. It has been. The input voltage of the solar cell E smoothed by the smoothing capacitor C1 is supplied to the inverter circuit 4.
The power conditioner control unit 2 includes each of the switch elements S2
S5 is turned on and off to switch element S2 and inductor L
3. System power supply P, inductor L2 and switch element S
5, a switch element S4, an inductor L2,
By forming the system power supply P, the inductor L3, and the second path of the switch element S3, the output of the AC load current to the system power supply P is controlled.

In a solar power generation system provided with such a power conditioner 1, a solar cell E shown in FIG.
In the IV curve (current-voltage characteristic), when the maximum power point voltage Vpmax is, for example, about 350 V DC, the open-circuit voltage Vop becomes a high voltage of about 530 to 700 V DC, so that the power conditioner 1 such as the smoothing capacitor C1 is used. The problem that the breakdown voltage of the component is exceeded occurs. Note that, here, the PV curve is a power-voltage characteristic and is shown in plurals, but shows a case where the illuminance on the solar cell E decreases from the beginning. PV curve is solar cell E among other PV curves
Illuminance is the lowest and the open-circuit voltage Vop is DC420V
On the other hand, all of the other PV curves have the same open-circuit voltage Vop. Although there is an IV curve for each of these PV curves, only one IV curve is shown in the figure. Therefore, the power conditioner controller 2 sets the maximum voltage to, for example,
In the operating voltage range with the upper limit DC4
The operation of the inverter circuit 4 can be controlled so as to limit the voltage to 20 V or less. As this control, the power conditioner control unit 2 detects whether the input voltage of the solar cell E has reached the upper limit value of DC 420 V, and if the input voltage has reached the upper limit value of DC 420 V, the inverter circuit 4
The switch elements S2 and S3 are turned on at the same time, and a load current flows through the switch elements S2 and S3 to control the maximum voltage to an upper limit value of 420 V DC or less so that the components can be protected. Note that, in the normal operation state, the operation is controlled near the maximum power voltage in the PV curve. Therefore, this protection function operation is performed when the main unit has an abnormality and the normal operation cannot be performed, or when there is a system abnormality and the normal operation cannot be performed. And so on. Therefore, in the first embodiment, when outputting 200 V AC to the grid side, the input voltage of the solar cell E is changed to, for example, D by the power conditioner control unit 2 that controls the operation of the inverter circuit 4.
By increasing the voltage to C350V, the booster circuit 3 becomes unnecessary, and its input voltage is reduced to the upper limit value DC42 of the operating voltage range.
By controlling the voltage to 0 V or less, the input voltage of the solar cell E can be increased, and the input voltage can be directly input to the inverter circuit without being boosted by the booster circuit. The cost can be reduced by improving the conversion efficiency and reducing the number of parts.

Second Embodiment A second embodiment of the present invention will be described with reference to FIG. 3. In the first embodiment, the protection function operation is performed by a software operation of the power conditioner control unit 2. However, the protection function operation is possible even with a hardware circuit configuration like the circuit configuration of the second embodiment shown in FIG.

That is, in the power conditioner 1 of the second embodiment, the voltage at the connection of the resistors R1 and R2 connected in series between both ends of the smoothing capacitor C1 is input to the inverting terminal-of the comparator CP. , The voltage at its reverse terminal-is connected to a reference power source E1 connected to its forward terminal +.
, The gate circuit GT is connected from the comparator CP, and the output of the comparator CP is connected to the gate circuit G.
T, and both output portions of the gate circuit GT are connected to the switch elements S2 and S3 in the inverter circuit 4, respectively. When the input voltage of the solar cell E reaches the upper limit value DC420V of the operating voltage range, the comparator CP opens the gate circuit GT, whereby the power conditioner control unit 2 turns on the switching elements S2 and S3 to turn on the load current I To control the maximum value of the input voltage of the solar cell E to the upper limit value DC420V or less. As a result, the same operation and effect as in the first embodiment can be obtained in the second embodiment.

Third Embodiment Referring to FIG. 4, the third embodiment of the present invention will be described. The protection function operation also includes a resistor R3 and a switch connected in parallel between both ends of a smoothing capacitor C1 as shown in FIG. A protection circuit formed by connecting the element S1 in series is connected, and when the power conditioner control unit 2 detects that the input voltage of the solar cell E has reached the upper limit value DC420V of the operating voltage range, the switching element S1 is turned on. As a result, the load current flows through this protection circuit to control the maximum value of the input voltage of the solar cell E to be equal to or less than the upper limit value of DC 420 V. As a result, the same functions and effects as those of the first embodiment can be obtained in the third embodiment.

Fourth Embodiment A fourth embodiment of the present invention will be described with reference to FIG. 5. The protection function operation also includes a switching element S1 'connected in parallel across a smoothing capacitor C1 as shown in FIG. And a protection circuit formed by connecting the storage battery E2 in series,
When the power conditioner control unit 2 detects that the input voltage of the solar cell E has reached the upper limit value DC420V of the operating voltage range, the power conditioner control unit 2 drives the switch element S1 ′ to turn on, thereby flowing the load current to this protection circuit and causing The maximum value of the input voltage of the battery E is controlled to DC 420 V or less. As a result, the same functions and effects as those of the first embodiment can be obtained in the fourth embodiment.

Fifth Embodiment Referring to FIG. 6, a fifth embodiment of the present invention will be described. The above-described protection function operation is also performed individually for each solar cell constituting the solar cell E as shown in FIG. The zener diode ZD1 is connected in parallel, and when the solar cell reaches a predetermined voltage and the input voltage of the entire solar cell E reaches the upper limit value DC420V of the operating voltage range, the zener diode ZD1 of each solar cell conducts, A load current flows through the turned-on Zener diode ZD1, and the maximum value of the input voltage of the solar cell E is controlled to DC 420 V or less. Alternatively, as shown in FIG. 6B, a Zener diode ZD2 is connected in parallel to each solar cell module constituting the solar cell E, and the output of the entire solar cell E is DC420V.
, The Zener diode ZD2 conducts, and a load current flows through the Zener diode ZD2 which conducts, thereby controlling the maximum voltage to DC 420 V or less. The IV curve of each solar cell constituting the solar cell E in this case is shown in FIG. FIG. 7 shows that the Zener diode ZD1 has a Zener voltage of 0.6 V DC when the Zener diodes ZD1 are individually connected in parallel to the solar cells. As described above, also in the fifth embodiment, the same operation and effect as in the first embodiment can be obtained.

Sixth Embodiment Referring to FIG. 8, the sixth embodiment of the present invention will be described. The protection function operation also includes a step-down operation between a solar cell E and a smoothing capacitor C1 as shown in FIG. When the chopper type regulator 5 is inserted and connected, and the power conditioner control unit 2 controls the switching element S1 'to turn on and off when the output of the smoothing capacitor C1 reaches the upper limit value DC420V of the operating voltage range, the maximum value of the input voltage of the solar cell E is obtained. To DC42
Control to 0V or less. As described above, also in the sixth embodiment, the same operation and effect as those in the first embodiment can be obtained.

As described above, in each of the above-described embodiments, the maximum value of the input voltage of the solar cell E is set to, for example, DC42.
Since the voltage is controlled to 0 V or less, the maximum working voltage of the indoor wiring in the extension specification is 300 V AC and 450 V DC.
It is possible to cope with what is planned to be V, and it can be considered to be extremely effective.

[0017]

As described above, according to the present invention, even if the input voltage of the solar cell is increased, it is possible to control the input voltage to be equal to or lower than the upper limit of the operating voltage range. This eliminates the need for power conversion efficiency, significantly reducing the number of components, and the cost of the power conditioner. Even if the input voltage is increased, the input voltage is controlled to be equal to or lower than the upper limit value of the operating voltage range, so that the power conditioner is not destroyed due to the withstand voltage of the internal components.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a power conditioner according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an IV curve and a PV curve of a solar cell.

FIG. 3 is a circuit diagram of a power conditioner according to Embodiment 2 of the present invention.

FIG. 4 is a circuit diagram of a power conditioner according to Embodiment 3 of the present invention.

FIG. 5 is a circuit diagram of a power conditioner according to a fourth embodiment of the present invention.

FIG. 6 is a circuit diagram of a power conditioner according to a fifth embodiment of the present invention.

FIG. 7 is a view showing an IV curve of the solar cell of FIG. 6A.

FIG. 8 is a circuit diagram of a power conditioner according to Embodiment 6 of the present invention.

FIG. 9 is a circuit diagram of a conventional power conditioner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power conditioner 2 Power conditioner control part 4 Inverter circuit E Solar cell

Claims (6)

[Claims] A power conditioner control unit for controlling an operation of an inverter circuit controls an input voltage related to a solar cell output to be equal to or lower than an upper limit value of an operation voltage range, thereby making it possible to increase the input voltage. A power conditioner in a photovoltaic power generation system, wherein a voltage can be directly input to the inverter circuit without being boosted by a booster circuit. 2. The power conditioner control section turns on a switch element in an inverter circuit connected in parallel between both ends of the solar cell when the input voltage reaches the upper limit value, and causes a load current to flow through the switch element. The method according to claim 1, wherein the input voltage is controlled to a predetermined value or less.
Power conditioner in solar power generation system. 3. A protection circuit having a resistor and a switch element connected in parallel between both ends of the solar cell, wherein the power conditioner control unit switches the switch element in the protection circuit when the input voltage reaches the upper limit value. The power conditioner in the photovoltaic power generation system according to claim 1, wherein the input voltage is controlled to be equal to or lower than the upper limit value by turning on the switch element to supply a load current to the switch element. 4. A protection circuit having a switching element and a battery connected in parallel between both ends of the solar cell, wherein the power conditioner control section switches the switching element in the protection circuit when an input voltage reaches the upper limit value. The power conditioner in the photovoltaic power generation system according to claim 1, wherein the input voltage is controlled to be equal to or lower than the upper limit value by turning on the switch element to supply a load current to the switch element. 5. A zener diode is connected to each of the solar cells constituting the solar cell or to the entire solar cell, and the Zener diode is turned on when the voltage between both ends of the solar cell reaches the upper limit. The power conditioner in a photovoltaic power generation system according to claim 1, wherein a load current is supplied to a Zener diode to control the input voltage to be equal to or lower than the upper limit value. 6. A step-down chopper-type regulator is connected between the solar cell and the smoothing capacitor, and the regulator has a switch element inserted therein in series between the solar cell and the smoothing capacitor. The power conditioner control unit turns on and off the switch element when the voltage between both ends of the solar cell reaches the upper limit to control the input voltage to be equal to or lower than the upper limit. Power conditioners in photovoltaic systems.