JP2003018859A - Power conditioner for solar power generation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conditioner for solar power generation enabling full utilization of power which can be generated by a solar battery not only in a linked operation but also in a self-generating operation. SOLUTION: In a linked operation, a pair of switching devices of an N-phase arm of an inverter 13 are stopped, and power is supplied to a load 21 connected with a power system 14 from U-phase and V-phase arms. In a self-generating operation, the pair of switching devices of the N-phase arm are driven, and the inverter 13 is made to operate as a single-phase three-wire output inverter supplying powers to antidisaster apparatuses 16 connected between the N-phase arm and the U-phase and V-phase arms respectively. With such a constitution, even in the self-generating operation, the powers can be supplied to the antidisaster apparatuses 16 with a load voltage of AC 100 V while the line voltages of the U-phase and V-phase arms are maintained to be the same output voltage (for instance 200 V) between phases of the power system 14, so that the power which can be generated by a solar battery 12 can be fully utilized as well as in the linked operation.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a power conditioner for photovoltaic power generation.

[0002]

2. Description of the Related Art PV inverters
The DC power generated by the solar cell is extracted to the maximum and converted into AC power, and by connecting to a power system such as a commercial power source, a load connected to the power system (for example, a television,
This is a device for stable power supply to load groups such as air conditioners and refrigerators. For this kind of equipment, in order to enable stable power supply to disaster prevention loads, for example, even in the event of a power system power failure, disconnect the connection with the power system and supply power to disaster prevention loads etc. Some have functions. More specifically, as shown in FIG. 3, the power conditioner 1 for photovoltaic power generation includes, for example, a single-phase two-wire output inverter 3 that converts the output from the solar cell 2 into AC power, and the output side of the inverter 3. Switch 5 for connecting the U-phase and the V-phase, for example, on the side of the single-phase three-wire power system 4
A second switch 7 that connects the output side of the inverter 3 to the disaster prevention load 6 side, a power failure detector 8 that detects a power failure of the power system 4, a DC component control circuit 9, the inverter 3, the first and second Control means 10 (U for driving and controlling the second switches 5 and 7)
Phase drive circuit, V phase drive circuit, control circuit).

Normally, the second switch is opened and only the first switch is closed, and the two output lines of the inverter 3 are connected to the power system 4.
U-phase and V-phase of the
The interconnection operation is performed in which electric power is supplied to the single-phase three-wire type load connected between the phase and the V phase. On the other hand, when the power system 4 has a power failure, a detection signal is given from the power failure detector 8 to the control circuit of the control means 10, and the first switch 5 is opened and the second switch is closed to make the output side of the inverter 3 a disaster prevention load. A self-sustaining operation is performed in which the inverter 3 is connected so as to supply electric power to the disaster prevention load 6.

[0004]

By the way, in the power conditioner 1 for photovoltaic power generation, in order to maximize the generated power from the solar cell 2 driven with a predetermined output voltage (for example, DC300V) and effectively use it, For example, it is necessary to measure the current / voltage of the input line from the solar cell 2 and control the current of the inverter 3 so that the product of the current / voltage from the solar cell 2 is maximized. Also, during interconnection operation,
In order to connect with the power system 4, the output voltage of the inverter 3 is AC20 which is the same as the U-phase and V-phase line voltages of the power system 4.
It is necessary to set it to 0V (effective value). However, the disaster prevention load 6 and the like generally have a load voltage of AC100V. Therefore, during self-sustaining operation, the output voltage of the inverter 3 is the same as the load voltage of the disaster prevention load 6 of AC100V.
It becomes necessary to control the voltage so that With this, the output voltage of the inverter is suppressed to 1/2,
There is a problem that only half of the rated output of the inverter can be supplied to the disaster prevention load 6.

Therefore, the load voltage AC100 is maintained while the inverter 3 is operated at the output voltage AC200V even in the self-sustaining operation.
As a configuration capable of supplying electric power to the V disaster prevention load 6, it is conceivable that the AC 200V output voltage of the inverter 3 is converted to AC 100V by a voltage conversion transformer and applied to the disaster prevention load 6. However, this configuration is not practical because the voltage conversion transformer is expensive.

[0006] In addition, for example, in the case of medical equipment or the like, there is a load that is not convenient even if the power supply is stopped for a moment when switching from the interconnection operation to the independent operation. However, in the configuration of the conventional power conditioner for photovoltaic power generation described above, the AC20 is adjusted according to the line voltage of the power system during the interconnected operation of the inverter.
Since it is necessary to control with 0V output and 100V AC output according to the load voltage of the load during self-sustaining operation, there is no instantaneous interruption and self-sustaining operation without stopping the power supply to the load. It is not possible to adopt a configuration that shifts to.

The present invention has been made in view of the above circumstances. A first object of the present invention is to make the most effective use of the electric power that can be generated by a solar cell even in a self-sustaining operation as in the interconnection operation. The second purpose is to provide a power conditioner for photovoltaic power generation, and the second purpose is for photovoltaic power generation that can switch from interconnected operation to independent operation without interruption to the load. It is in the area of providing inverters.

[0008]

In order to achieve the above object, a power conditioner for photovoltaic power generation according to the invention of claim 1 is an inverter for converting output power from a solar cell into AC power, and an output of the inverter. Switching means that can be selectively connected to the power system or a self-sustaining load, a power failure detection circuit that detects a power failure in the power system, and the output side of the inverter is always connected to the power system to provide power to the power system. When the power failure detection signal from the power failure detection circuit is detected from the power failure detection circuit, the output side of the inverter is switched and connected to the self-sustaining load. In a power conditioner for photovoltaic power generation, which includes a control unit that performs an independent operation that controls an inverter so as to supply power to the self-sustaining load, the inverter is A single-phase three-wire output inverter including a neutral-phase generating switching element, wherein the control means stops the neutral-phase generating switching element of the inverter during interconnection operation, and the neutral-phase generating switching The inverter is controlled to supply power to the power system from the remaining two output lines other than the neutral phase output line connected to the element, and the neutral phase generation switching element is driven during self-sustaining operation to load the self-sustaining load. It is characterized by controlling the inverter so as to supply electric power to the.

According to a second aspect of the present invention, there is provided a power conditioner for photovoltaic power generation in which an inverter converts output power from a solar cell into AC power and supplies the AC power to a load side, and a power supply line between the inverter and the load. And a power system that can be connected to the power system, a power failure detection circuit that detects a power failure in the power system, and the inverter is controlled to always close the switch and supply power to the load in cooperation with the power system. When the power failure detection signal from the power failure detection circuit is received from the power failure detection circuit, the switching means is opened to control the inverter so as to supply power to the load. A power conditioner for photovoltaic power generation, comprising an inverter for a single-phase three-wire output equipped with a switching element for generating a neutral phase, and an inverter for load. The control means stops the neutral phase generation switching element of the inverter during the interconnection operation, and the remaining two output lines other than the neutral phase output line connected to the neutral phase generation switching element. Therefore, the inverter is controlled so as to supply electric power to the load side, and the inverter is controlled so as to drive the neutral phase generating switching element during self-sustaining operation to supply electric power to the load.

[0010]

<Advantages and Effects of the Invention><Invention of Claim 1> According to the configuration of Claim 1, the switching element for generating the neutral phase of the single-phase three-wire output inverter is stopped during the interconnection operation. The inverter is controlled so that power is supplied from the remaining two output lines other than the output line to the load connected to the power system. Since the switching element for neutral phase generation is stopped, the switching loss during interconnected operation does not increase compared to the conventional PV power conditioner equipped with a single-phase 2-wire output inverter. It becomes possible to supply the maximum electric power that the solar cell can generate to the load connected to the electric power system. Moreover, since the switching element for generating the neutral phase is provided as described above, there is a concern that the DC component contained in the AC output current may flow between the V phase and the neutral phase. Since the operation of the switching element is stopped, only one DC component suppression circuit is required,
The circuit configuration becomes simple.

Next, when the electric power system fails, the output side of the inverter is connected from the electric power system to the self-sustaining load by the switching means to start the self-sustaining operation. During this self-sustaining operation, the switching element for neutral phase regeneration is also driven to control the inverter as a single-phase three-wire output inverter, and the neutral phase output line and the remaining two output lines are connected to each other. Power to the isolated load. That is, even during the self-sustaining operation, while maintaining the line voltage of the remaining two output lines other than the neutral output line at the same output voltage as the line voltage of the power system (for example, AC200V), It is possible to supply electric power to a self-sustaining load such as an AC100V disaster prevention load, so that even in the self-sustaining operation, the electric power that can be generated by the solar cell is effectively utilized as in the case of the interconnection operation. The purpose of can be achieved.

<Invention of Claim 2> According to the configuration of Claim 2, at the time of the interconnection operation, the switching means is closed and the switching element for generating the neutral phase of the inverter is stopped so that a part other than the neutral phase output line is disconnected. From the remaining two output lines, the inverter is controlled so as to supply power to the load in cooperation with the power system. During the self-sustaining operation, the switching means is opened and the neutral phase generating switching element is also driven. The inverter is controlled as a single-phase three-wire output inverter to supply electric power to the load connected between each of the neutral output line and the remaining two output lines. That is, even during self-sustaining operation, the line voltage of the remaining two output lines other than the neutral output line is maintained at the same output voltage as the line voltage of the power system (for example, AC200V), In addition to the effect of claim 1, the second object of being able to supply electric power to the load without interruption is achieved in addition to the effect of claim 1 described above. be able to.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment> A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram of a photovoltaic power generation system including a power conditioner 11 according to this embodiment. The power conditioner 11 connects an inverter 13 that converts output power from the solar cell 12 into AC power, and an output side of the inverter 13 to a single-phase three-wire power system 14 (for example, a commercial power supply of AC200V). The first switch 15 and the output side of the inverter 13 are connected to the disaster prevention load 16 (for example, the load voltage A
The second switch 17 connected to the (C100V) side, the power failure detector 18 for detecting a power failure of the power system 14, the DC component control circuit 19, the inverter 13, the first and second switches 15, 17 And a control means 20 for controlling driving.

Of these, the inverter 13 is a single-phase three-wire output inverter 13 having a neutral phase generating switching element 13a. More specifically, the inverter 13
Is composed of, for example, a smoothing capacitor connected in parallel to the output terminal of the solar cell 12 and a pair of switching elements connected in series with each other, and each input side of the three-phase connected to the output terminal of the solar cell 12 in parallel. It has a well-known configuration including a bridge circuit including arms and an output filter circuit connected to the output end of each arm and including a reactor and a capacitor. The switching element pair of each of these arms is ON / OFF controlled by the control means 20 described later, and thus functions as an inverter 13 for a single-phase three-wire output or a single-phase two-wire output. Of these three-phase arms, two arms (hereinafter, "U-phase arm" and "V-phase arm") other than the arm including the neutral phase generating switching element 13a (hereinafter, "N-phase arm"). Say)
The output end of U is connected to U of the power system 14 via the first switch 15.
Phase and V phase, respectively. On the other hand, as will be described later, at the time of power failure of the power system 14, the first switch 15 is opened and the second switch 17 is closed based on the control signal from the control circuit, and the disaster prevention load 16 makes the U-phase and N-phase of the inverter 13 It is connected between the phase arms and between the V-phase and N-phase arms. That is, the first and second switches 15 and 17 correspond to the “switching means” of the invention of claim 1.

The power failure detector 18 is configured to detect the U-phase voltage and the V-phase voltage of the power system 14, for example, and detect the power failure state of the power system 14 based on this. The DC component control circuit 19 detects the DC component superimposed on the AC output current based on the DC amplitude change of the connection line between the U-phase arm of the inverter 13 and the U-phase of the power system 14, and controls the detection signal. Give to 20 side. Then, the control means 20 performs switching control so as to suppress the direct current component.

Subsequently, the control means 20 controls the inverter 13
U-phase drive circuit 20a, N-phase drive circuit 20b, and V-phase drive circuit 20 for driving the switching element pair of each arm
c, and a control circuit 20d for supplying a drive signal to those drive circuits 20a, 20b, 20c. Also, N
The phase drive circuit 20b and the control circuit 20d are the power failure detector 1
Control circuit 20 only when receiving a power failure detection signal from 8
AND which gives the drive signal from d to the N-phase drive circuit 20b
It is connected through the circuit 20e. The inverter 13 control system of the present embodiment is a PMW control system, and the control circuit 20d supplies the sine wave voltage signals having a phase difference of 180 degrees to the U-phase and V-phase drive circuits and the signal level is zero. A voltage signal is applied to the N-phase drive circuit 20b, and a carrier signal is applied to each drive circuit 20a, 20b, 20c. Then, each drive circuit 20a, 20b, 20
c is ON / OF by applying a drive signal to the switching element pair of each arm based on the comparison between the voltage signal and the carrier signal.
F control. This allows the inverter 13 to function as the single-phase three-wire output inverter 13.

Next, the operation of the power conditioner 11 according to this embodiment will be described. <During interconnection operation> When the power system 14 is not out of power, the first switch 15 is closed and the control means 20
AND circuit 20e does not receive a power failure detection signal from power failure detector 18. Therefore, a drive signal is not given to the N-phase drive circuit 20b from the control circuit 20d, the switching elements of the N-phase arm are stopped, and only the switching element pairs of the U-phase and V-phase arms are turned ON / OFF. Will be controlled. From the U-phase and V-phase arms, 1
There is a phase difference of 80 degrees, and the voltage between the lines (U-V) is AC2.
AC power of 00V (effective value) will be output,
Therefore, it becomes possible to supply power to the load 21 connected to the power system 14 while synchronizing with the U phase and the V phase of the power system 14. Further, in order to extract the generated electric power from the solar cell 12 driven by a predetermined output voltage (for example, DC300V) to the maximum and effectively use it, for example, a current / voltage sensor (not shown) is provided on the input line from the solar cell 12. The signal from the current / voltage sensor is given to the control circuit 20d, and the operation of each switching element pair of the inverter 13 is controlled so that the product of the current / voltage from the solar cell 12 is maximized.

<During self-sustaining operation> When the power failure detector 18 detects the power failure state of the power system 14, the power failure detector 18 gives a power failure detection signal to the control circuit 20d and the AND circuit 20e. Then, the first switch 15 is opened and the second switch 17 is closed by the control signal from the control circuit 20d, and the drive signal from the control circuit 20d is transferred to the AND circuit 20d.
It is also given to the N-phase drive circuit 20b via e, and the switching element pair of the N-phase arm is turned ON / OFF.
Start operation. As a result, the inverter 13 functions as a single-phase three-wire output inverter 13. Then, power is supplied to the disaster prevention load 16 connected between the U-phase and N-phase arms of the inverter 13 and between the V-phase and N-phase arms.

As described above, during the interconnection operation, the switching element pair of the N-phase arm of the inverter 13 is stopped, and power is supplied from the U-phase and V-phase arms to the load 21 connected to the power system 14. Therefore, as compared with the conventional PV power conditioner including the single-phase two-wire output inverter 13, the load 21 connected to the power grid 14 can be connected to the load 21 without increasing switching loss during grid-connected operation. It becomes possible to supply the maximum electric power that the solar cell 12 can generate.

On the other hand, during the self-sustaining operation, the inverter 1 which outputs the single-phase three-wire output by driving the switching element pair of the N-phase arm.
3, the power is supplied to the disaster prevention load 16 connected between the N-phase arm and the U-phase and V-phase arms. As a result, the line voltages of the U-phase arm and the V-phase arm are maintained at the same output voltage as the line voltage of the power system 14 (for example, AC200V) even during self-sustaining operation.
Electric power can be supplied to the disaster prevention load 16 having a load voltage of AC100V, and thus the maximum electric power that can be generated by the solar cell 12 can be effectively used as in the interconnection operation.

<Second Embodiment> FIG. 2 shows a second embodiment (corresponding to the invention of claim 2). The power conditioner 30 according to the present embodiment shifts to a self-sustaining operation without interruption for a load 31 (for example, load voltage AC100V) connected to the output side of the inverter even when the power system fails. It enables continuous supply of electric power. The difference from the above-described embodiment is that instead of the first and second switches 15 and 17, an opening / closing means 32 capable of connecting a power supply line between the inverter 13 and the load 31 and the power system is provided. The other points are the same as those in the first embodiment. Therefore, the same reference numerals as those of the first embodiment are given, duplicated explanations are omitted, and only different points will be explained next.

As shown in FIG. 2, a load 31 is connected between each of the N-phase arm of the inverter 13 and the U-phase and V-phase arms. Then, for example, a pair of semiconductor switches (for example, triac) 32a, 32b are provided in the middle of the power supply line between each arm and the load.
The power system 14 is connected via the opening / closing means 32 having More specifically, the U phase of the power system 14 is connected to the power supply line connected to the U phase arm of the inverter 13 via the semiconductor switch 32a, and the V phase of the power system 14 is connected to the power supply line connected to the V phase arm. The neutral point of the power system 14 is connected to the power supply line connected to the N-phase arm via the semiconductor switch 32b.

According to this structure, the opening / closing means 32 is closed during the interconnection operation, and the power conditioner 30 is
Power is supplied to the load 31 in cooperation with the power system 14 while stopping the switching element pair of the N-phase arm of the inverter 13. Here, when the power failure detector 18 detects the power failure state of the power system 14, the opening / closing means is opened by receiving a signal from the control circuit 20d, the U phase and the V phase of the power system 14 are disconnected, and the inverter is By driving the switching element pair of the N-phase arm, the N-phase arm and U
Load 31 connected between each of the phase and V phase arms
Power to. In this way, even during self-sustaining operation,
The line voltage of the U-phase arm and the V-phase arm is set to the power system 14
The configuration is such that power is supplied to the load 31 connected as a single-phase three-wire system while maintaining the same output voltage as the line voltage (for example, AC200V) of No. It is possible to shift to the self-sustaining operation, and it is possible to continuously supply power to the load 31 without interruption even when the power system fails.

<Other Embodiments> The present invention is not limited to the above-described embodiments, but can be implemented with various modifications without departing from the scope of the invention.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a photovoltaic power generation system including a power conditioner according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a photovoltaic power generation system including a power conditioner according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a photovoltaic power generation system including a conventional power conditioner.

[Explanation of symbols]

11,30 ... Power conditioner 12 ... Solar cell 13 ... Inverter 13a ... Switching element for generating neutral phase 14 ... Power system 15 ... First switch 16… Disaster prevention load (independence load) 17 ... Second switch 18 ... Blackout detector 19 ... DC component control circuit 20 ... Control means 21, 31 ... Load 32 ... Opening / closing means

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masahide Yamaguchi             No. 1 Inobaba-cho, Nishinosho, Kichijoin, Minami-ku, Kyoto-shi               Within Japan Battery Co., Ltd. F-term (reference) 5G066 HA06 HA11 HA30 HB06                 5H007 AA05 AA17 BB07 CA01 CB05                       CC23 DA03 DA06 DB01 DC02                       DC04 DC05 EA02 FA02 GA09                 5H420 BB12 BB14 CC03 DD04 EA11                       EA45 EB09 EB39 FF03 FF04                       FF10 FF25

Claims (2)

[Claims] 1. An inverter for converting output power from a solar cell into AC power, switching means capable of selectively connecting an output side of the inverter to a power system or a self-sustaining load, and detecting a power failure in the power system. And a power failure detection circuit that always connects the output side of the inverter to the power system, and performs an interconnected operation that controls the inverter so as to supply power to the power system. When receiving a power failure detection signal that detects a system power failure, the switching means switches and connects the output side of the inverter to the self-sustaining load, and controls the inverter to supply power to the self-sustaining load. In a power conditioner for photovoltaic power generation, which includes a control unit that performs operation, the inverter includes a single-phase 3 including a switching element for generating a neutral phase. An output inverter, wherein the control means stops the neutral phase generation switching element of the inverter during the interconnection operation, and outputs a neutral phase output line other than the neutral phase output line connected to the neutral phase generation switching element. The inverter is controlled so as to supply electric power to the power system from the remaining two output lines, and the neutral phase generating switching element is driven during the self-sustained operation to supply power to the self-sustained load. A power conditioner for photovoltaic power generation, which controls the inverter as described above. 2. An inverter that converts output power from a solar cell into AC power and supplies the AC power to a load side, and an opening / closing means that can connect a power supply line between the inverter and the load to a power system. A power failure detection circuit for detecting a power failure in the power system, always closing the opening / closing means, performing a grid interconnection operation for controlling the inverter so as to supply power to the load in cooperation with the power system, When a power failure detection signal for detecting a power failure of the power system is received from a power failure detection circuit, the switching means is opened, and a control means for performing a self-sustaining operation for controlling the inverter to supply power to the load is provided. A power conditioner for photovoltaic power generation, wherein the inverter is an inverter for single-phase three-wire output including a switching element for neutral phase generation, and the load is Connected to an inverter, the control means stops the neutral phase generation switching element of the inverter during the interconnection operation, and the remaining parts other than the neutral phase output line connected to the neutral phase generation switching element. The inverter is controlled so that electric power is supplied to the load side from two output lines, and the neutral phase generating switching element is driven to supply electric power to the load during the self-sustaining operation. A power conditioner for photovoltaic power generation, which controls