JPS6155719A - Starting method of solar light power generating system - Google Patents

Abstract

PURPOSE:To monitor an electromotive force and to start a power converter by operating intermittently a switch at the stop of a solar light power generating system so as to use a charge current to a capacitor provided to the input of the electric power converter. CONSTITUTION:While the solar light power generating system is stopped, an AC switch 34 is opened, an inverter circuit 33 is turned off to isolate it from an AC power system 14. Then a DC switch 35 is turned on, a capacitor 32 is charged from a solar light generator 11 in a closed circuit formed with a reactor 31 and a current detector 41. The charging current is detected by the detector 41 and the level of the signal is detected by a current detection circuit 42. A timer circuit 43 detects that the level detection output signal 421 is outputted for a prescribed time and when it is discriminated that an electromotive force of the solar light generator 11 reaches a value sufficiently to start the power converter 13, the signal 431 is activated. A control circuit 44 is started by the signal 431, the gate signal 441 starts the inverter 33 and when the value reaches a prescribed value, a switch 34 is operated to connect the system 14.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a solar power generation system that converts direct current from a solar cell into predetermined power, and in particular appropriately monitors the electromotive force of a solar cell and starts a power conversion device. 0 [Technical Background of the Invention] A solar cell plate that generates electricity by receiving sunlight irradiation (as shown in Figure 4) When the temperature is kept constant, when the output current V increases above a certain value, the output voltage V@ decreases rapidly and becomes zero. Electric power Pm
ax occurs when the output current is Iop, and the power value is Io
A solar cell panel, which is given by the product of p and the output voltage Top at this time, is constructed by connecting a plurality of 40 to 50 solar cell plates in series or in parallel to one panel. For example, the configuration of a solar panel is as shown in Figure 5. 1 in Figure 5 is a solar panel, and when it is irradiated with sunlight, a positive polarity is generated at terminal 3 and a negative polarity is generated at terminal 4. Generate power and get output 5.

The solar cell panel 2 having the configuration shown in FIG. 5 is isometrically shown in the circuit shown in FIG. 6 in an electromotive state. Here, the symbols shown in FIG. 6 that are the same as those in FIG. 5 indicate the same functions. This solar panel 2 maintains a constant temperature (for example, 300
When the amount of solar radiation is changed as 'K), the relationship curve between the output current Is and the output voltage v8 at K changes as the amount of solar radiation changes as shown in Figure 7, and the maximum output point is on the 8 curve shown by the dotted line in the figure. It changes like this. Therefore, if you are operating a resistor connected to the solar panel 2 as a load that can produce maximum output when the solar radiation is 50 mW/ci, for example, if the solar radiation changes from 50 mW/ci to 1.
When the amount of solar radiation increases to 00 mWlof, the operating point is determined from the intersection point A of the load characteristic curve with the output current vs. output voltage relationship curve when the solar radiation is 50 mW/i.
It moves to the intersection B with the output current vs. output voltage relationship curve at mW/cd, and it is no longer possible to extract the maximum output.

Also, if the amount of solar radiation is from 50 mW/c+J to 10 m
W/c++! When K decreases to , the operating point moves to a point CIC which is significantly away from its maximum output point. In this way, the output of a solar panel group constructed by connecting a plurality of solar panels 2 in series and parallel, whose output fluctuates as the amount of solar radiation changes, is also easily affected by the amount of solar radiation. .

Therefore, as it is, it is not possible to efficiently extract output from the solar panel group, resulting in a low efficiency solar power generation system. Usually, in a solar power generation system, the load is usually AC equipment, or it is necessary to convert DC to AC as it is directly connected to the AC power system. The output of the generator 11 is connected to an AC load or an AC power system 14 via a self-excited power converter I3 (hereinafter referred to as the power converter 13) composed of an inverter. is a solar cell panel group composed of a plurality of solar cell springs/I/2, and 12 is a backflow prevention diode.

[Problems with background technology]

In order to monitor whether the electromotive force of the solar power generator 11 is sufficient to start the power conversion device 13 when starting the solar power generation system as described above, conventionally, the solar power generator 11 There is a method in which a monitor circuit for monitoring the electromotive force of the solar power generator 1 is provided close to the solar power generator 1, and when the output of this monitor circuit exceeds a predetermined value, the power conversion device 13 is activated. I'm thinking about it. This monitor circuit (as shown in FIG. 9) was composed of a solar cell panel 2 or a device capable of measuring sunlight irradiation, in addition to a solar power generator 11. However, the configuration shown in FIG. 9 cannot monitor the true electromotive force of all solar power generators. For example, in the figure, if the solar power generation unit 8!1 is blocked by clouds, etc., and the monitor circuit 21 is receiving solar radiation, the output of the monitor circuit 21 will be used to monitor the solar power generation unit 1!
It is incorrectly determined that the electromotive force of No. 1 has enough electromotive force to start the power converter 13, and the start condition is met and a start command is given to the power converter 13. However, the solar power generator 1)
Because it does not have enough electromotive force to start the seventh
Since control is performed that significantly deviates from the operating point shown in the explanation of the figure, there is a drawback that the power converter 13 cannot be operated. The larger the scale of the solar power generator 11, the more likely this drawback will occur and the more difficult it will be to start up and operate the solar power generator 11.

[Purpose of the invention]

Therefore, in view of the above-mentioned points, when the solar power generation system is stopped, the present invention operates nine switches provided between the solar power generator 11 and the power converter 130 intermittently, and connects the switches and the power converter to each other. The electromotive force of solar power generator 1 itself was monitored by the level of charging current to the capacitor installed between It is an object of the present invention to provide a method for starting a solar power generation system that can reliably start the power conversion device 13 later.

[Summary of the invention]

To achieve this object, the present invention provides a solar power generation system in which a solar cell and a power conversion device that converts the DC output of the solar cell into a predetermined DC or AC are connected via a switch. The power conversion device includes a capacitor connected in parallel, a current detection circuit for detecting a charging current of the capacitor, and a current level detection circuit for detecting that an output of the current detection circuit has reached a predetermined value. operating the switch intermittently when the power converter is stopped;
The output signal of the current level detection circuit is used as a starting signal for the power conversion device to start a solar power generation system. [Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to FIG. Explain with reference to.

In FIG. 81, the same symbols as in FIG. 8 have the same functions. However, 14 indicates the case of an AC power system. In the embodiment shown in FIG.
1 shows a case where the inverter circuit 33 is configured to convert direct current to alternating current, and since the operating principle of this inverter circuit 33 for converting direct current to alternating current is well known, a description thereof will be omitted. In particular, the case where the inverter circuit 33 is constituted by a self-excited voltage control type inverter is shown, and the DC reactor 31 and the capacitor 32 form a filter circuit that suppresses voltage and current ripples caused by the operation of the inverter circuit 33. In other words, in the case of a voltage source inverter,
It is common to have a capacitor at its input. In addition, the flywheel diode 36 is a DC switch 35t.
- It is designed to circulate the energy stored in the DC reactor 31 when it is opened.

Comparing FIG. 1 and FIG. 8 and describing the different means, in the conventional FIG. 8, as shown in FIG. 2), the power converter 13 is started based on the detected value, whereas in FIG. 1, when the solar power generation system is stopped, when the DC switch 35 is turned on, the solar power generator 1 is activated as shown in FIG. Since a charging current flows to the capacitor 32 opposite to the electromotive force of , the electromotive force of the solar power generator 11 is monitored by detecting this charging current, and the power conversion device 13 is activated.

That is, in the embodiment shown in FIG. 1, when the solar power generation system is stopped, the AC switch 34 is opened and the inverter circuit 3
3 is turned off by the control circuit 44, and the AC power system 1
Dissociate from 4. Next, the 1 DC switch 35 is turned on to connect the solar power generation 1all and the DC terminals 301 and 302. That is, the solar power generator 1 is a closed circuit formed by the backflow prevention diode 12 - DC switch 35 - DC terminal 301 - DC reactor 3 - capacitor 32 - current detector 4 - DC terminal 302 as shown in FIG. A charging current flows to the capacitor 32 according to a time constant determined by the internal impedance of the solar power generator 11, the DC reactor 31, and the capacitor 32 when the solar radiation amount reaches the amount of solar radiation shown in FIG. A current detector 41 detects the charging current flowing through the aforementioned closed circuit to the capacitor 32, and a current detection circuit 42 detects the level of the current detection signal 411. Here, the current detection circuit 42 may be a well-known comparator, so a detailed explanation will be omitted. This output signal 42 is, for example, a current detection signal 411.
When the current detection circuit 42 detects that the current has reached a predetermined value, the logic level is set to "H#", and when the predetermined value is not reached, the logic level is set to L#, the output signal 421 becomes "H". The timer circuit 43 detects the time when the

An example of this timer circuit 43 is shown in FIG. 3. In FIG. 3, when the output signal 421 of the current detection circuit 42 becomes "H#", the output of the first stage monostable multivibrator 432 changes from "H" to "H" for a predetermined period of time. When it goes to L' and goes to "H#" again, that is, when the input of the second stage monostable multipipe lake 433 goes from "L" to "H", the output goes to "L#" for a predetermined time and goes to "H" again. become. The time up to this point is timer circuit 4
3, and if the output signal 421 becomes "L#" within this setting value, the output signal 431 becomes "H#" for a predetermined period of time.
become.

When the amount of solar radiation increases and the electromotive force of the solar power generator 1 increases, the current that can flow increases as shown in the seventh factor, so the charging current to the capacitor 32 flows through the current detector 4 in FIG. 1, and the capacitor 32 charging time is reduced. The current detection signal 411 of the current detector 4 is detected by the current detection circuit 42, and the timer circuit 43 detects that the output signal 42 is being output for a predetermined period of time, thereby starting the solar power generator 11. When it is determined that the power is sufficient to start the power conversion device 13, the output signal 43 is activated. This output signal 4
31 is given as a starting command to the control circuit 44, a gate signal 441 is given to the inverter circuit 33, and the inverter circuit 33 starts, and when the output voltage of the inverter circuit 33 reaches a predetermined value, the AC switch is activated. 34 is operated to connect the power conversion device 13 and the AC power system 14, and predetermined control is performed. The above operation is shown in the time chart of FIG. Adding an explanation of the operation of the present invention using FIG. 2,
When the DC switch 35 is turned on and the current detection signal 411 does not reach the set value of the current detection circuit 42, the DC switch 35 is turned on.
is turned off after a predetermined time T1, and a gate signal 44 is applied to the inverter circuit 3 after a predetermined time T2 after the DC switch 35 is turned off in order to discharge the charge in the capacitor f32.
3 is operated and after a predetermined time T3, the inverter circuit 33 is stopped. This time setting of 3 may be a fixed time, or may be determined by detecting that the charge in the capacitor 32 has been discharged. Further, after a predetermined time T4, the direct book closing device 3S is turned on again. Here, if the current detection signal 41 does not reach the predetermined value, or even if the current detection signal 411 reaches the predetermined value, the timer circuit 4
When the output signal 43 of No. 3 is not output, that is, when the relationship between the time T5 during which the current detection signal 411 is equal to or greater than the predetermined value and the time TX set by the timer circuit 43 is 5)'rX, that is, when If the electromotive force of the solar power generator 1 does not reach a sufficient value to start the power conversion device 113, repeat the time chart described above. Continuing the explanation of the operation of the present invention, the DC switch 35 is turned on, and if the current detection signal 411 reaches a predetermined value and the time T5 is less than or equal to the predetermined value, the DC switch 35 remains on and the predetermined value is reached. After 6 hours, the gate signal 441 is applied to operate the inverter circuit 73, and after the output voltage of the inverter reaches a predetermined value, the AC switch 34 is turned on after a predetermined time T7 to connect to the AC power system 14.

Here, all the means for setting the predetermined times T1 to T7 can be easily inferred from the above explanation, so they will not be described here. Since the electromotive force of the solar power generator 11 is directly monitored and the power conversion device J3 is activated based on the detected level, there is no difference between the detected value of the monitor circuit and the electromotive force of the solar power generator 11 as in the conventional method, and the target can be easily monitored. It is possible to perform a start-up. In addition, unlike the conventional system, there is no need for a solar panel 2 or a more expensive monitor circuit that can measure sunlight irradiation, and it can be realized using an inexpensive and simple circuit.

Next, another embodiment of the present invention will be described. The DC switch 35 in the embodiment shown in FIG. 1 may be a switch element, or the switch element may be controlled to operate in a constant state. Furthermore, the switch element may also be used as the backflow prevention diode 12.

In addition, in the embodiment shown in FIG. 1, the current detector 41 is provided on the condenser 32 side with respect to the flywheel diode 3G, but it may be provided on the solar power generator 11 side (or alternatively, it may be provided on the positive or negative electrode side of the capacitor 32). In addition, the current detector 41 can also be used as a direct current detector that is generally provided for protecting or controlling the inverter circuit 33.

Furthermore, the inverter circuit 33 can be activated under the condition that the output code 431 is applied to the control circuit 44 as a condition for starting the power converter 13 and an external signal not shown is applied.

Further, in the embodiment shown in FIG. 1, the timer circuit 43 is provided, but the electromotive force of the solar power generator 11 may be determined only by detecting the level of the current detection circuit 42.

Furthermore, the power converter 13 is not limited to the self-excited voltage type inverter shown in the embodiment, but may also be a current type inverter or a separately excited type inverter, and is not limited to an inverter circuit that converts direct current to alternating current; It may be a DC-DC converter that converts direct current into a predetermined direct current, and a similar effect can be obtained by providing a capacitor at its input.

Further, in the embodiment of the present invention, when the current detection circuit 42 does not reach a predetermined value, the inverter circuit 33 is operated to discharge the capacitor 32, but the inverter circuit 33 may not be operated and a discharge resistor etc. may be provided. capacitor 32
It is also possible to perform a discharge.

〔Effect of the invention〕

Thus, according to the present invention, in a photovoltaic power generation system composed of a solar cell having photovoltaic power and a power converter that converts its DC output into a predetermined alternating current, when the system is stopped, the DC switch is turned on and the power conversion is started. The electromotive force of the solar generator can be accurately captured by the charging current to the capacitor installed at the input of the device, and there is no need for an expensive electromotive force monitor circuit to start the power converter. 0 that allows stable startup without causing system malfunction due to differences in electromotive force.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a solar power generation system showing an embodiment of the present invention, Figure 2 is a time chart of Figure 1, Figure 3 is a block diagram of a timer circuit of Figure 1, and Figure 4 is a solar power generation system. A characteristic diagram of the relationship between output current and output voltage of the battery board, Figure 5 is a solar battery panel configuration diagram, Figure 6 is an equivalent circuit diagram of Figure 5, and Figure 7 is a thick @ battery board when the amount of solar radiation changes. The output voltage vs. output current characteristic diagram, tIcB diagram, is a block diagram of a solar power generation system, and FIG. 9 is a configuration diagram of a conventional solar power generation device. 1...Solar cell plate, 2...Solar cell panel, 3゜4
... terminal, 5 ... output, 1 ... solar power generator,
12... Backflow prevention diode, 13... Power converter, 14... AC load or AC power system, 21
...Monitor circuit, 31...DC reactor, 32.
...Capacitor, 33...Inverter circuit, 34...
- AC switch, 35... DC switch, 41... Current detector, 411... Current detection signal, 42... Current detection circuit, 421... Output signal, 44... Control circuit ,
441...Gate signal, 301.302...DC terminal, 43...Timer circuit, 431...Output signal, 3
6...Flywheel diode, 432,433...
・Monostable multivibrator, 434...Positive logic NO
R gate. Figure 1 C Figure 2 Figure 3 Figure 4 Figure 6

Claims (1)

[Claims] In a solar power generation system in which a solar cell having a photovoltaic force and a power conversion device that converts the DC output of the solar cell into a predetermined DC or AC are connected via a switch, the switch and the power conversion device are connected to each other via a switch. A current detection circuit that detects a charging current of a capacitor connected in parallel between the two and a current level detection circuit that detects that the output of the current detection circuit reaches a predetermined value is provided, and when the power converter is stopped, the switch 1. A method for starting a solar power generation system, comprising operating the current level detection circuit intermittently and using an output signal of the current level detection circuit as a starting signal for the power converter.