JPH09131067A - Power feeder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the number of inverters being operated according to the insolation intensity with high reliability by controlling the operation and suspension of a power conversion means with the signal of the detection means which detects the input resultant power, etc., of the power conversion means. SOLUTION: A time of low insolation state where a converter 2-1 is operable, a switch 4-1 is closed, and the converter 2-1 is operates, but the close signal S from a switch control circuit 5-1 is not outputted, and the switch 4-2 connected to the converter 2-2 is kept closed. Therefore, the power generated by a solar battery 1-1 is converted with only the converter 2-1. When the insolation intensity increases, a close signal SH1 is outputted from the switch control circuit 5-1, receiving the output of a detection means 3-1, and the converter 2-2 operates. Furthermore, when insolation intensity increases, a close signal SH2 is outputted from the control circuit 5-2, receiving the output of the detection means 3-2, and the switch 4-2 is closed, and the converter 2-3 operates.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can always maintain a high conversion efficiency of power conversion means such as an inverter and / or a converter connected in parallel to a DC power generation means such as a solar cell or a fuel cell having large output fluctuation. Power supply device.

[0002]

2. Description of the Related Art Conventionally, for example, in a solar power generation system configured to convert direct-current power generated by a solar cell into alternating current by an inverter to supply power to an alternating current load, expected maximum solar radiation is expected. In many cases, an inverter having a capacity capable of converting the maximum generated power of the solar cell in strength is prepared, and the capacity of the solar cell and the rated capacity of the inverter are used in correspondence with each other.

For this reason, the inverter is usually operated at a load factor lower than its rated capacity, and particularly at a low load factor in a situation where the solar radiation intensity is low such as morning / evening, cloudy weather, and rainy weather. Will be.

In general, as the load factor of an inverter decreases, the conversion efficiency of converting direct current into alternating current also decreases, but especially when the load factor becomes lower than 20%, the conversion efficiency also remarkably decreases. And in the conventional solar power generation system,
In a situation where the intensity of solar radiation is low, the conversion efficiency is greatly reduced, which may make it impossible to operate the inverter itself or wastefully consume the power generated by the solar cell.

Therefore, in order to prevent the reduction of conversion efficiency due to the reduction of the load factor of such an inverter as much as possible, a system including a DC power source such as a solar cell and a plurality of inverters maintains the power conversion efficiency at an appropriate value. Then, a method for controlling parallel operation has been proposed (see, for example, Japanese Patent Laid-Open No. 7-67346).

According to this method, the sum of output power of a plurality of inverters is compared with a program set value derived and set from each inverter capacity in advance, an inverter to be operated is selected, and chattering is prevented when the operating state is changed. By providing a timer mechanism for this, a certain state confirmation time is set.

However, unless all the rated capacities and the maximum power generation capacities of the components of the system consisting of a plurality of inverters and a DC power source such as a solar cell have been determined, a rational operating program cannot be set.

That is, in order to appropriately add a unit consisting of a small-capacity standardized solar cell and an inverter, or to cope with various system capacities, a switch control circuit for performing switching control of operation and suspension of the inverter. Need to be changed or the program needs to be changed, resulting in problems such as poor versatility and complicated control.

Further, although chattering for a very short time can be prevented by setting a constant state confirmation time when changing the operating state, if the operation continues near the operating state changing condition, it will frequently occur at regular intervals. There is no change in the switching of the switch, and it is hard to say that this can avoid the situation where the inverter is frequently activated and stopped.

Further, there is a possibility that the intensity of solar radiation will suddenly increase within the state confirmation time and the capacity of the inverter will be exceeded, or it may cause a failure of the inverter.

It should be noted that instead of the inverter, a converter that controls the operating point so that the power generated by the solar cell is maximized (for example, MPPT (maximum power point
It is easily understood that the same problem as described above occurs even in the case of the tracker)), and the description thereof will be omitted.

Therefore, an object of the present invention is to provide a power supply device which can easily and reliably control the number of inverters to be operated according to the intensity of solar radiation.

[0013]

In order to solve the above-mentioned problems, a power supply apparatus of the present invention comprises a DC power generation means and n (n ≧ 2) power conversion means connected in parallel to the DC power generation means. And the input combined power or output combined power, or the input combined current or output combined current of the kth (k = 1, ..., N-1) to nth power conversion means, respectively. (m = k) detecting means, and control means for controlling the operation / pause of the (k + 1) th power converting means by the detection signal from the mth detecting means.

Here, in particular, when m = k = 1, the first
When the detection value of the detection means exceeds the high level set value, both of the first and second power conversion means are activated, and then the detection value of the detection means is lower than the low level set value lower than the high level set value. If the second power conversion means is stopped when the above condition occurs, the operation / stop of the second power conversion means is not repeated (chattering) at the set value of the first detection means.

The DC power generation means, at least first and second power conversion means connected in parallel to the DC power generation means, detection means for detecting the generated power or generated current of the DC power generation means, and the detection When the detected value of the means becomes higher than the high level set value, the first and second power conversion means are operated, and then the detected value of the detection means becomes lower than the low level set value lower than the high level set value. When the second
The power supply device may include a control unit that suspends the power conversion unit.

Further, it may be characterized in that all the power conversion means are once put into operation when the power supply device is activated.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail with reference to the drawings. [Embodiment 1] As shown in FIG.
Each of the DC-DC converters (hereinafter referred to as converters) 2-1, 2-2, 2-3, which are the first to third power conversion means having the rated capacity C, are added to the solar cell 1-1 having the maximum power generation capacity 3C. The first to third switches 4-1, 4-2, 4-3
Connected in parallel via each of the above, and further, the power generation amount of the solar cell 1-1, that is, the combined power to the converter (or the combined current, hereinafter, only the power is described for simplicity).
First and second detecting means 3-1 and 3-2 for detecting
It is provided with first and second switch control circuits 5-1 and 5-2 for controlling the opening and closing of the first to third switches 4-1, 4-2 and 4-3 by the detection signals from these detecting means. , And power is supplied to a load (not shown) connected to the first and second output terminals 6-1 and 6-3. Here, D1 and D2 are the first and second branch points, respectively,
J1 is the confluence. Since the output voltages of the converters 2-1 and 2-2 are the same, the converging point J1 is provided and the output terminal 6 is provided.
-1, and the output voltage of the converter 2-3 is different from that of the converters 2-1 and 2-2, so that the output terminal 6-3 is separately provided. It should be noted that a load that requires more electric power may be connected to the output terminal 6-1 and a load that does not require electric power may be connected to the output terminal 6-3. Examples of such loads include storage batteries, DC motors, heaters, incandescent lamps,
Inverter, etc.

Here, in the switch 4-1 provided in the preceding stage of the converter 2-1, whether the solar cell 1-1 is not generating power by the converter 2-1 or the converter 2-
When 1 is in an inoperable low power (low solar radiation) state, it is a switch that is detected by a sensor provided inside the converter 2-1 and is opened by this detection signal.

The switches 4-2 and 4-3 are normally open switches, and the switch 4-2 is the switch control circuit 5-.
When the detection means 3-1 detects more power than the set capacity (C) of 1, the output signal S of the switch control circuit 5-1.
When the switch 4-3 is closed by H1, and the detection means 3-2 detects more electric power than the set capacity (C) of the switch control circuit 5-2, the switch control circuit 5-2.
Is closed by the output signal SH2.

When all the switches 4-1, 4-2 and 4-3 are closed, the detecting means 3-1 detects the solar cell 1-.
1 and the first branch point D1 and is provided with a detecting means 3-2.
Is provided between the first branch point D1 and the second branch point D2, the converter 2-1 and 2-
2 and 2-3 will detect the value which added the electric power which carries out electric power conversion, and the detection means 3-2 will detect the value which added the electric power which carries out electric power conversion by the converters 2-2 and 2-3.

The operation of the power supply device E1 according to the change in the average solar radiation intensity for one day will be described below. First, in the early morning, when the converter 2-1 is operable in a low solar radiation state, the switch 4-1 is closed and the converter 2-
1 operates, but the power detection value S1 by the detection means 3-1
Is still small, the set value (C) of the switch control circuit 5-1
Therefore, the closed signal SH1 from the switch control circuit 5-1 is not output, and the switch 4-2 connected to the converter 2-2 remains open. Similarly converter 2
The switch 4-3 connected to -3 also remains open, so the converter 2-2 and the converter 2-3 remain dormant.

Therefore, the generated power of the solar cell 1-1 is converted into power only by the converter 2-1, and the load factor of the converter 2-1 is converters 2-1, 2-2, 2
-3, which is three times as high as that in parallel operation, so that the conversion efficiency of the converter 2-1 can be kept high.

Next, when the solar radiation intensity slightly increases as the sun rises and the detection value S1 by the detecting means 3-1 becomes equal to or higher than the set value (C) of the switch control circuit 5-1, the switch control circuit 5 -1 outputs the close signal SH1, the switch 4-2 is closed, and the converter 2-2 operates.
As a result, the processing power in the converters 2-1 and 2-2 becomes 1/2 C or more, respectively, but since this value is smaller than the set value (C) of the switch control circuit 5-2, the switch control circuit 5- 2 does not output the closing signal SH2, and the switch 4
-3 remains open and converter 2-3 remains dormant.

Next, when the solar radiation intensity further increases and the detected value S2 by the detecting means 3-2 becomes equal to or greater than the set value (C) of the switch control circuit 5-2, the closing signal SH2 is output and the switch 4-3. Is closed and the converter 2-3 is activated. Thereby, the processing power in converters 2-1, 2-2, 2-3 becomes 2 / 3C or more, respectively, and the conversion efficiency is maintained high. At this time, the detection value S2 of the detection means 3-2 increases to 4 / 3C or more, which is the sum of the processing powers of the converters 2-2 and 2-3, so that the switch 4-3 does not cause chattering.

In the high solar radiation state before and after the south central part, the parallel operation state of these converters 2-1, 2-2, 2-3 is maintained, but in the afternoon, the solar radiation intensity slightly decreases, and the detecting means 3
When the detected value S2 of −2 becomes less than the set value (C) of the switch control circuit 5-2, the closing signal SH2 is not output and the switch 4-3 is opened, so that the converter 2-3 is stopped.

Further, the intensity of solar radiation decreases, and the detecting means 3-
When the detected value S1 of 1 is less than the set value (C) of the switch control circuit 5-1, the closing signal SH1 is not output and the switch 4-2 is opened, so that the converter 2-2 is stopped.

As described above, the number of working converters can be automatically adjusted according to the amount of power generated by the solar cell 1-1, and the load factor of the converter can be maintained high, resulting in a decrease in conversion efficiency as in the conventional case. Can be prevented as much as possible.

[Second Embodiment] In the first embodiment, the closing signal SH1 of the second switch 4-2 from the first switch control circuit 5-1 is the detection value S1 of the first detecting means 3-1. Although it is output by comparing the set value (C) of the first switch control circuit 5-1 with the magnitude, the detected value S1 does not change before and after the opening and closing of the second switch 4-2. Power generation is C
The second switch 4-2 may cause chattering in the vicinity of. An example of preventing this chattering will be described based on FIG.

As shown in FIG. 2, in the second embodiment, inverters 7-1 and 7-2 having a rated capacity C are provided in place of the converters 2-1 and 2-2 in FIG. When the detected value S1 is equal to or higher than the high level set value (H: H = C) which is the first set value of the switch control circuit 5-1, the closing signal SH1 is output and the switch 4-2 is closed. It is a thing. Here, the difference from the first embodiment is that the closed signal SH1 is held unless the signal SL1 is output. The other configurations are similar to those of the first embodiment, and thus the description thereof is omitted.

That is, the signal SL1 is output when the detection value S1 by the detection means 3-1 becomes equal to or lower than the low level setting value (L <C) which is the second setting value lower than the first setting value of the switch control circuit 5-1. Then, the signal SH1 is turned off. This prevents the switch 4-2 from chattering when the detection value S1 detected by the detection means 3-1 is held in the vicinity of C.

[Embodiment 3] The power supply device is not always activated from a low solar radiation state. For example, in the case of system interconnection with a commercial power source, the solar cell may be in the maximum power generation capacity state when the system is temporarily stopped by a system power failure and then restarted. An apparatus for appropriately coping with such a high solar radiation state at startup is shown in FIG. 3 as a third embodiment.

As shown in FIG. 3, all the inverters are operated when the power supply device E3 is started, and thereafter, the inverters are automatically suspended and operated in a cascade manner according to the detected power value.

Here, the second to fourth switches 4-2 and 4
-3 and 4-4 are normally closed switches, 3-1 and 3-2.
Reference numerals 3-3 denote first, second and third power detection means, respectively. Other configurations are the same as those in FIG. 2, and thus description thereof will be omitted. In the figure, D1 to D3 are first to third branch points, and J1 to J3 are first to third confluence points. Here, for example, the switch 4-4 is opened by the open signal SL3 that is output when the detection value S3 by the power detection means 3-3 becomes equal to or lower than the low level set value (L = C) of the switch control circuit 5-3. It

In this way, since all the inverter circuits are closed at the time of start-up, the processing power of the inverter does not exceed the rated capacity even in the high solar radiation state. After startup, the number of operating inverters is automatically adjusted according to changes in solar radiation. In order to prevent chattering,
The low level setting value L of the switch control circuit 5-1 is set to L <C, and the detection value S1 of the signal SL1 is the switch control circuit 5-1.
Becomes higher than the high level set value (H = C) of the signal SH1.
May be held until is output.

In each of the above-mentioned embodiments, an example in which a solar cell is used as the DC power generation means has been shown, but other DC power generation means, for example, fuel cells, generated power of hydraulic power, wind power, etc., is converted into DC. DC power generation means may be used. Further, the switch may be constituted by a normally open and normally closed parallel switch, and when the detection means detects a high level, the switch control circuit closes the next normally open switch and the detection means sets the low level. When detected, the normally closed switch to which the switch control circuit belongs may be opened, and appropriate changes and implementations are possible without departing from the scope of the present invention.

[0036]

As described above, according to the power supply device of the present invention, the number of actuations of the power conversion means is automatically and easily increased or decreased according to the power generation amount of the DC power generation means by the extremely simple structure. Therefore, the load factor of the operated power conversion means can be kept extremely high, and the reduction of the power conversion efficiency can be prevented as much as possible.

Further, when the first and second power conversion means are connected in parallel to the DC power generation means, the detection value of the detection means for detecting the generated power or the generated current of the DC power generation means becomes higher than the high level set value. The first and second power conversion means are actuated when it becomes, and when the detection value of the detection means becomes below the low level set value lower than the high level set value, the second
Since the control means for suspending the power conversion means is provided, it is possible to prevent the repeated operation and suspension of the second power conversion means as much as possible, and it is possible to provide a highly reliable power supply device.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing an embodiment according to the present invention.

FIG. 2 is a block circuit diagram showing another embodiment according to the present invention.

FIG. 3 is a block circuit diagram showing another embodiment according to the present invention.

[Explanation of Codes] 1-1, 1-2, 1-n ... Solar cells 2-1, 2-2, 2-3 ... Converters 3-1, 3-2, 3-3 ... Detection means 4-1, 4-2, 4-3 ... Switch 5-1, 5-2, 5-3 ... Switch control circuit 6-1, 6-3 ... Output terminal 7-1 7-2, 7-3, 7-4 ... Inverters E1, E2, E3 ... Power supply device

Claims (2)

[Claims] 1. A direct current power generation means, n (n ≧ 2) power conversion means connected in parallel to the direct current power generation means, and a kth (k)
, 1, ..., N-1) to n-th power conversion means for detecting the input combined power or the output combined power, or the input combined current or the output combined current, respectively.
And a control means for controlling activation / deactivation of the (k + 1) th power conversion means by the detection signal from the mth detection means. 2. DC power generation means, first and second power conversion means connected in parallel to the DC power generation means, detection means for detecting power generated or current generated by the DC power generation means, and the detection means. When the detected value of is above the high level set value, the first and second power conversion means are operated, and then the detected value of the detection means is below the low level set value lower than the high level set value. A power supply device, comprising: control means for suspending the second power conversion means.