JP6883729B2 - Electrical equipment - Google Patents

Description

The present invention supplies this output to a conversion circuit that converts the output of a plurality of solar cell strings configured by connecting a plurality of solar cell panels into a single output and then converts it into AC power that can be connected to the grid. It is about the electrical equipment that makes it possible.

The system that converts the power generated by the solar cell into AC power is such that at least the solar cell string composed of a plurality of solar cell panels connected in series and parallel and the generated power of this solar cell string are maximized. A DC / DC conversion circuit whose boost ratio is controlled and this DC /
It is configured to include a DC / AC conversion circuit that converts the output of the DC conversion circuit into AC power that can be connected to the system.
Since the power generated by a solar cell depends on the amount of solar cell radiation, it is better to divide the solar cell into multiple solar cell strings than to connect all the solar cells in series and parallel to form a single solar cell string. It is known that the decrease in generated power due to changes in the power generation (mainly in the shade) is small.
In such a system, a DC / DC conversion circuit is associated with each solar cell string, and the power generated by each solar cell string is controlled to be maximized. On the other hand, in consideration of cost performance, a system that omits some DC / DC conversion circuits is also considered.

If a semiconductor switching element is used in the DC / DC conversion circuit, the rated output is set due to the capacitance of the switching element. Patent Document 1 describes a protective device that operates so that the generated power of the solar cell string does not exceed this rated output.

Japanese Unexamined Patent Publication No. 2003-284355

The one described in Patent Document 1 monitors the input current value to an inverter (a device that converts a DC output output by a solar cell into an AC output), and the output current value of the solar cell is based on the rated input current value of the inverter. When it became large, it provided protection such as stopping power generation.
At this time, in order to omit the input current sensor that monitors the input current value, it is used that the output power calculated from the output voltage and the output current of the inverter is equal to the input power of the inverter (generated power of the solar cell). This output power was divided by the input voltage of the inverter to obtain the input current.

Considering that the power generation output of the solar cell decreases when the amount of solar radiation decreases, overloading is performed by increasing the number of solar cell panels so that the power generation output becomes larger than the rated output of the inverter. In such a case, when the amount of solar radiation fluctuates rapidly, the protection device described in Patent Document 1 may not be able to respond in time for the protection operation due to the increase in the calculation process. Also, when trying to increase the response speed by directly using the output voltage and output current of the DC / DC conversion circuit, the response speed is slowed down by the smoothing capacitor used in the DC / DC conversion circuit. It did not lead to improvement.
On the other hand, when the output voltage stabilized by the smoothing capacitor is measured, the response speed of the measurement to the fluctuation of the output voltage may be slow. T. A general-purpose measuring instrument such as (current transformer) can be used, but since the response speed is slow as described above, it has been used to detect state information that slowly shifts to an abnormal state.

In addition, when a plurality of solar cell strings are used, when the protection operation of the plurality of DC / DC conversion circuits is performed by the output voltage of the DC / DC conversion circuit (input voltage of the DC / AC conversion circuit), all of them are abnormal. The DC / DC converter circuit of the above has reached a protective operation, and the power output of the solar cell cannot be effectively utilized.

The electric device of the present invention is provided with a plurality of solar cell strings and a DC / DC conversion circuit for boosting the DC power generated by the solar cell for each of the plurality of solar cell strings, or is generated by the solar cell. A plurality of DC / DC conversion circuits for boosting DC power are provided in some of the plurality of solar cell strings, and the outputs of the plurality of DC / DC conversion circuits are output to a single DC line and output to the DC line. In an electric device configured to output the output of a DC / DC conversion circuit to an external power conversion device via a connection terminal in order to use the output of the DC / DC conversion circuit for conversion to AC power, a solar cell string of a plurality of DC / DC conversion circuits. Boost operation of a plurality of DC / DC conversion circuits corresponding to the input information when at least one of the plurality of electrical input information on the side exceeds a predetermined value for each input information. At least one of the plurality of electrical output information caused by the output of the plurality of DC / DC conversion circuits to the DC line exceeds a predetermined value for each output information. It is characterized by including a control unit that stops the boosting operation of all DC / DC conversion circuits in such a case.

The electrical device of the present invention corresponds to the corresponding D based on the electrical information before and after the DC / DC conversion circuit.
It protects the C / DC conversion circuit or all DC / DC conversion circuits, and can maintain the output of the electrical equipment according to the information.

FIG. 1 is an explanatory diagram of an electric device showing an embodiment of the present invention. FIG. 2 is an explanatory diagram showing an example of a DC / DC conversion circuit. FIG. 3 is an explanatory diagram showing an example of a DC / AC conversion circuit.

FIG. 1 is an explanatory diagram showing an embodiment of the present invention. In this figure, a plurality of solar cell panels (composed of a plurality of solar cell cells) are connected in series and parallel to form one solar cell string 1, and a plurality of solar cell strings 2 to 4 are similarly formed. It constitutes a solar cell string. Reference numeral 5 denotes an electric device, which is a DC / DC conversion circuit 6 and DC / D that boost the generated power mainly generated by the solar cell, for example, the generated power generated by the solar cell string.
It has a C conversion circuit 7, an open / close switch 8 to an open / close switch 11, and a control unit 12.

The input side of the DC / DC conversion circuit 6 is connected to the solar cell string 1 via the open / close switch 8 and the connection terminal, and the generated power of the solar cell string 1 is supplied to the DC / DC conversion circuit 6. There is. A voltage sensor 13 that detects the output voltage of the solar cell string 1 (input voltage of the DC / DC conversion circuit 6) and an output current of the solar cell string 1 ( A current sensor 14 for detecting the input current of the DC / DC conversion circuit 6) is provided. The current sensor 14 is not limited to a method using a voltage drop due to a resistor, or a general-purpose method such as a Hall type method using a Hall element or the like in consideration of the loss due to the voltage drop.

The DC / DC conversion circuit 7 is also connected to the solar cell string 2 via an open / close switch 9 and a connection terminal, and similarly includes a voltage sensor 15 and a current sensor 16. The outputs of the DC / DC conversion circuit 6 and the DC / DC conversion circuit 7 are output to a single (common) DC lines 23a and 23b.

The power generation output of the solar cell string 3 is the DC lines 23a, 23 via the open / close switch 10.
It is output to b. This generated power is similarly detected by the voltage sensor 17 and the current sensor 18.
The diode 19 is for preventing backflow of generated power.
Similarly, the solar cell string 4 is connected to the DC lines 23a and 23b via the open / close switch 11 and the diode 22, and also includes the voltage sensor 20 and the current sensor 21.
Two DC / DC conversion circuits 6 corresponding to the solar cell string 1 and the solar cell string 2
, DC / DC conversion circuit 7 is provided, but the number of DC / DC conversion circuits is not limited to this, and DC / DC conversion circuits are provided corresponding to all of the solar cell strings 1 to 4. You may. Further, a DC / DC conversion circuit may be provided corresponding only to the solar cell string 1, and DC / D corresponding to the solar cell string 1 to the solar cell string 3 may be provided.
A C conversion circuit may be provided. The generated power of the solar cell string to which the DC / DC conversion circuit is not provided corresponds to the DC line 23a via the open / close switch and the diode.
Connected to 23b.

Similar voltage sensors 24 and current sensors 25 are provided on the DC lines 23a and 23b, and D.
Output of C / DC conversion circuit 6 (power generated by solar cell string 1), DC / DC conversion circuit 7
(Power generated by the solar cell string 2), power generated by the solar cell string 3, and power generated by the solar cell string 4 are output, and these outputs are combined on the DC lines 23a and 23b. is there.

Reference numeral 26 denotes a power conversion device, in which the DC power of the DC lines 23a and 23b of the electric device 5 is supplied via the connection terminal and can be connected to the system 29 by the DC / DC conversion circuit 27 and the DC / AC conversion circuit 28. After being converted to AC power, it is output to system 29.

In the embodiment shown in FIG. 1, a DC / DC conversion circuit 6 and a DC / DC conversion circuit 7 are provided in the solar cell string 1 and the solar cell string 2 of the plurality of solar cell strings 1 to 4 and DC /. The outputs of the DC conversion circuit 6 and the DC / DC conversion circuit 7 are output to a single DC line 23a, 23b, and the DC / D output to the DC lines 23a, 23b.
The outputs of the C conversion circuit 6 and the DC / DC conversion circuit 7 are output to the power conversion device 26 so as to be used for conversion to AC power.

If a DC / DC conversion circuit is provided so as to correspond to the solar cell string 3 and the solar cell string 4, a plurality of solar cell strings 1 can be provided with a DC / DC conversion circuit for boosting the DC power generated by the solar cell. To, each of the solar cell strings 4 is provided. In such a case, the outputs of the DC / DC conversion circuit 6, the DC / DC conversion circuit 7, and the additional DC / DC conversion circuit are output to a single DC line 23a, 23b, and the DC lines 23a, 23.
The output of the DC / DC conversion circuit 6, the DC / DC conversion circuit 7, and the additional DC / DC conversion circuit output to b will be output to the power conversion device 26 so as to be used for conversion to AC power. ..

The DC / DC conversion circuit 6 changes the boost ratio so that the generated power generated by the solar cell string 1 becomes the maximum value or the target value. The step-up circuit method is not limited, for example, a non-insulated chopping method mainly using a reactor, a switching element, a diode, and a smoothing capacitor, and mainly a switching element, an isolation transformer, and a rectifier circuit.
There is an insulated forward type that uses a capacitor. Further, a charge pump type, a flyback type, a resonance type and the like can be used. The boost ratio is controlled based on the control signal from the control unit 12. FIG. 2 is an explanatory diagram showing an example of the DC / DC conversion circuit 6. The reactor LD, the switching element DT, the diode DD, and the capacitor DC are connected so as to form a chopper type booster circuit. L / C is a noise filter circuit.

Therefore, the on-duty of the switching element DT is variably controlled by the control signal from the control unit 12, and the DC output of the DC / DC conversion circuit 6, that is, the generated power of the solar cell string 1 is set to be equal to or less than the maximum generated power corresponding to the amount of solar radiation. It can be changed arbitrarily. In addition, D
Since the C / DC conversion circuit 7 can be configured in the same manner, the description thereof will be omitted.

The DC / AC conversion circuit 28 shown in FIG. 1 transmits DC power to a predetermined frequency (for example, a frequency synchronized with the system 29 when connected to the system 29, or a frequency of 50 Hz / 60 Hz when performing independent operation. ) Is a power conversion circuit that converts to AC power. For example, PWM (Pulse)
Based on the Wide Modulation method, a pseudo sine wave is generated by repeating on and off switching of a plurality of switching elements (semiconductors, etc.), and then high frequency components are removed or attenuated by a filter circuit to generate AC power. ..

The DC / AC conversion circuit 28 shown in FIG. 1 includes the noise filter circuit L / C, but may be described separately. Further, the configuration of the conversion circuit is not limited to such a PWM method, and an inverter based on the NPC (Neutral Point Clamped) method, a gradation control type inverter, or one in which the output side or the input side of the inverter bridge circuit is clamped is used. However, the DC / AC conversion method is not limited.

The DC / AC conversion circuit 28 may at least output AC power and control the frequency, peak voltage (which may be an effective value), and phase difference between the voltage and current of the AC power. The DC / AC conversion circuit 28 controls the on-duty of the switching element based on the control signal from the control unit of the power conversion device 26.
Therefore, the DC / AC conversion circuit 28 of the power conversion device 26 converts the DC power supplied from the DC lines 23a and 23b into AC power and supplies it to the system 29, and the conversion amount of the AC power is the DC line. It can be changed by the voltage of 23a and 23b and the on-duty of the switching element.

FIG. 3 is an explanatory diagram showing an example of the DC / AC conversion circuit 28. Four switching elements T1 to T4 (six in the case of forming three-phase AC power) are connected in a single-phase bridge shape (in the case of three-phase AC power, a three-phase bridge shape). On this output side, a filter circuit composed of a reactor LA and a capacitor C1 and an output clamp circuit using two switching elements T5 and a switching element T6 in series to short-circuit the regenerative current by the reactor L1 are configured. There is.

The DC / AC conversion circuit 6 uses the switching element T1 when converting DC power into AC power.
Or the switching element T4 is turned on / off by the PWM method and the switching element T5
, T6 is turned on / off according to the regenerative current from the reactor LA.

That is, the DC / AC conversion circuit 6 converts the DC power of the DC power line 4 into AC power that can be connected to the system 5 (or 50 Hz / 60 Hz AC power for independent operation).

As the configuration of the control unit 12, one using one / a plurality of microprocessors (general microcomputers), one mainly composed of a DSP (Digital Signal Processor), or the like can be used, and the configuration is limited. is not it. The control unit 12 mainly includes a part that controls the entire operation and a part that controls the operation of the DC / DC conversion circuits 6 and 7. Each of these control parts does not have to be configured independently, as long as it is configured as a collection of subroutines on the software.

Although the electric device 5 and the power conversion device 26 have been described separately, they can be integrally configured. In this case, the DC / AC conversion circuit 28 may be controlled by the control unit 12, and the DC / DC conversion circuit 27 may be omitted.

The control unit 12 has a plurality of electrical input information (input voltage by the voltage sensor 13, input current by the current sensor 14, etc.) on the solar cell string 1 side of the DC / DC conversion circuit 6, and DC.
A plurality of electrical input information (voltage sensor 15) on the solar cell string 2 side of the / DC conversion circuit 7.
(Input voltage by current sensor 16, input current by current sensor 16, etc.) is input, and when at least one of these input information exceeds a predetermined value for each input information, the input information is dealt with. The boosting operation of the DC / DC conversion circuit is stopped.
The input voltage by the voltage sensor 17, the input current by the current sensor 18, the input voltage by the voltage sensor 20, the input current by the current sensor 21, and the like are also input at the same time.

In the protection operation of the control unit 12, for example, the voltage detected by the voltage sensor 13 is a predetermined voltage A (DC).
Based on the design of the / DC conversion circuit, the boosting operation of the DC / DC conversion circuit 6 is stopped when the state exceeding (for example, a value between 400V and 500V) is maintained for AA seconds. Further, for example, when the voltage detected by the voltage sensor 13 exceeds a predetermined voltage B (a value between 400 V and 500 V, which is higher than the predetermined voltage A based on the design of the DC / DC conversion circuit), a delay occurs. The boosting operation of the DC / DC conversion circuit 6 is stopped without doing so.

Further, in the protection operation of the control unit 12, for example, the current detected by the current sensor 14 is a predetermined current C.
When the state exceeding (for example, a value between 10A and 13A based on the design of the DC / DC conversion circuit) is maintained for CC seconds, the boosting operation of the DC / DC conversion circuit 6 is stopped. Also, for example
When the current detected by the current sensor 14 exceeds a predetermined voltage D (for example, a value between 10A and 13A and higher than the predetermined current C based on the design of the DC / DC conversion circuit), DC without delay. The boosting operation of the / DC conversion circuit 6 is stopped.

Further, in the protection operation of the control unit 12, for example, the product (power) of the voltage detected by the voltage sensor 13 and the current detected by the current sensor 14 is a predetermined power E (DC / DC conversion circuit design), for example. When it exceeds (a value between 2KW and 3KW), the boosting operation of the DC / DC conversion circuit 6 is controlled to maintain a boosting value reaching a predetermined power F smaller than the predetermined power E, and then this power becomes the predetermined power F. When the power falls below a smaller predetermined power G, the protection operation for suppressing this power is released.

Although the protection operation corresponding to the DC / DC conversion circuit 6 has been described, the same protection operation is performed for the input information of the voltage sensor 15, the current sensor 16 and the like corresponding to the DC / DC conversion circuit 7. ..

Further, the control unit 12 is a DC / DC conversion circuit 6 and a DC line 23 of the DC / DC conversion circuit 7.
A plurality of electrical output information (voltage value detected by the voltage sensor 24, current value detected by the current sensor 25, temperature sensor that detects the temperature inside the electric device 5 (not shown) due to the output to the a and 23b. ) Etc.) When at least one of the output information exceeds a predetermined value for each output information, the function of stopping all the boosting operations of the DC / DC conversion circuit 6 and the DC / conversion circuit 7 is provided. To prepare.

In the protection operation of the control unit 12, for example, the voltage detected by the voltage sensor 24 is a predetermined voltage H (DC).
Based on the design of the / DC conversion circuit, for example, when the value exceeds 400V to 500V), the boosting operation of the DC / DC conversion circuit 6 and the DC / DC conversion circuit 7 is stopped.
This stop is maintained for a predetermined time HH, and after the predetermined time HH elapses, the DC / DC conversion circuit 6 and the DC / DC conversion circuit 7 are restarted, and the boosting operation is restarted.

Further, in the protection operation of the control unit 12, for example, the current detected by the current sensor 25 is a predetermined current I.
When the value exceeds (for example, a value between 40A and 45A based on the design of the DC / DC conversion circuit), the boosting operation of the DC / DC conversion circuit 6 and the DC / DC conversion circuit 7 is stopped. This stop is maintained for a predetermined time II, and after the lapse of the predetermined time II, the DC / DC conversion circuit 6 and the DC / DC conversion circuit 7 are restarted, and the boosting operation is restarted.

Further, the protective operation of the control unit 12 is, for example, a temperature sensor (for example) that detects the temperature inside the electric device 5.
When the temperature detected by (not shown) exceeds a predetermined temperature J (for example, a value between 85 degrees and 95 degrees based on the design of the DC / DC conversion circuit), the DC / DC conversion circuit 6, And DC
The boosting operation of the / DC conversion circuit 7 is stopped. This stop is released after the temperature detected by the temperature sensor drops to a predetermined temperature K lower than the predetermined temperature J, and the DC / DC conversion circuit 6 and the DC / D
The C conversion circuit 7 is restarted. That is, the boosting operation is restarted.

Further, the protection operation of the control unit 12 is an abnormality of the temperature information of the temperature sensor (the temperature cannot be detected,
If a value exceeding the set range is detected), DC / DC conversion circuit 6, DC /
The conversion of the DC conversion circuit 7 is stopped.

The protection operation by the control unit 12 is performed on the DC / DC conversion circuit 6 and the DC / DC conversion circuit 7, and the generated power of the solar cell string 3 and the solar cell string 4 is the open / close switch 3 of each. If the open / close switch 4 is closed, it is supplied to the power converter 26. When the electric device 5 and the power conversion device 26 are integrally configured, the DC / AC conversion circuit 28 may be stopped if necessary.
In this way, sudden changes or abnormalities in the generated power of the solar cell string 1 and the solar cell string 2 are based on electrical input information such as the input voltage and input current of the DC / DC conversion circuit 6 and the DC / DC conversion circuit 7. , The boosting operation of the DC / DC conversion circuit 6 and the DC / DC conversion circuit 7 is quickly stopped. At this time, the DC / DC conversion circuit that does not need to be protected can be operated as it is to maintain the power generation by the solar cell string.
On the other hand, in the case of an abnormality caused in output information such as the output voltage or output current of the DC lines 23a and 23b, an abnormality related to the equipment such as a temperature abnormality in the electric equipment 5 or an abnormality of the temperature sensor, the DC / DC conversion circuit 6 The boosting operation of the DC / DC conversion circuit 7 is stopped.

The electric device of the present invention can be applied to a protective operation of an electric device having a DC / DC conversion circuit for boosting the generated power of a plurality of solar cell strings.

Although one embodiment of the present invention has been described above, the above description is for facilitating the understanding of the present invention and does not limit the present invention. It goes without saying that the present invention can be modified and improved without departing from the spirit thereof, and the present invention includes its equivalents.

1-4 Solar cell strings 6, 7 DC / DC conversion circuit 13, 15 Voltage sensor 12 Control unit 14, 16 Current sensor 23a, 23b DC line 24 Voltage sensor 25 Current sensor 26 Power converter 29 systems

Claims (5)

Multiple solar cell strings and DC / DC that boosts the DC power generated by the solar cells
A conversion circuit is provided for each of the plurality of solar cell strings, or a plurality of DC / DC conversion circuits for boosting the DC power generated by the solar cell are provided in some of the plurality of solar cell strings. The output of the DC / DC conversion circuit is output to a single DC line, and the outputs of the plurality of DC / DC conversion circuits output to the DC line can be used for conversion to AC power via a connection terminal. In electrical equipment configured to output to an external power converter
When at least one of the plurality of electrical input information on the solar cell string side of the plurality of DC / DC conversion circuits exceeds a predetermined value for each input information, the input information At least one of a plurality of electrical output information caused by the output of the plurality of DC / DC conversion circuits to the DC line while stopping the boosting operation of the plurality of DC / DC conversion circuits corresponding to the above. An electric device including a control unit that stops the boosting operation of all the plurality of DC / DC conversion circuits when one output information exceeds a predetermined value for each output information. The first aspect of claim 1, wherein the plurality of electrical input information is at least one of the input voltage of the DC / DC conversion circuit and the input current of the plurality of DC / DC conversion circuits. Electrical equipment. The electric device according to claim 1 or 2, wherein the plurality of electrical output information is at least one of a DC voltage and a temperature of the DC line. The electric device according to claim 3, wherein the control unit stops the boosting operation of all the plurality of DC / DC conversion circuits when an abnormality of the temperature sensor that detects the temperature is detected. The electric device according to claim 4, wherein the output of the solar cell string to which the plurality of DC / DC conversion circuits are not connected is supplied to the DC line.

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