JP2024081359A - Semi-independent photovoltaic power generation self-consumption system - Google Patents

Abstract

[Problem] Based on a hybrid inverter that is inexpensive and widely available overseas, we have devised a way to make it usable in Japan while taking advantage of the cost advantages. [Solution] The hybrid inverter is connected to a photovoltaic panel, and a step-down transformer section is provided in the electric circuit between the inverter and the load, with the load side adjusted for single-phase three-wire output, and an automatic switch between the inverter output voltage and the system voltage. In the case of On-grid, the automatic converter is composed of an inverter, and the system is connected to the inverter's in as a 200V D-type input. Also, D-type batteries are output from the out, but the inverter output voltage is supplied "always" and the system voltage is supplied "when there is a shortage". Because there is a voltage difference, the transformer adjusts the tap voltage according to the type of voltage on the input side, and whether the D-type battery output is the inverter output voltage or the system voltage, the AA output from the transformer is set to match the normal rated voltage. [Selected drawing] Figure 3

Description

The present invention relates to a photovoltaic power generation self-consumption system that is based on the combined use of photovoltaic power generation and a storage battery.

Recently, with the end of FIT, the selling price of solar power generation has been falling, while the purchasing price of electricity from the grid, i.e., electricity bills, has been rising.
Under these circumstances, there has been a movement to combine solar power generation with storage batteries to improve electricity usage costs through self-consumption of solar power generation, and an apparatus such as that described in Patent Document 1 has been proposed.
However, if one were to try to create a practical semi-independent type that could supply power from the grid in the event of a power shortage, the costs of building the system would be extremely high if all of the equipment needed to build the system were to be domestically produced.
Meanwhile, hybrid inverters capable of controlling both solar power generation and storage batteries are becoming available at low cost overseas.

Patent No. 6888898

The present invention has been made with a focus on the above-mentioned problems in the conventional technology, and its object is to provide a new and useful semi-independent solar power generation self-consumption system that is designed to be used effectively in Japan while retaining the cost advantages by using a hybrid inverter that is popular overseas and available at low cost, in combination with other devices to overcome issues such as voltage differences between overseas and Japan.
Another object of the present invention is to provide a semi-independent solar power generation self-consumption system that shares a common basic idea, but is specified in terms of systems that can be introduced immediately at present and systems that are expected to be introduced in the future in relation to the Electrical Appliance and Material Safety Act and obtaining grid connection certification.

The present invention has been made to solve the above problems, and is a semi-independent photovoltaic power generation self-consumption system that includes a hybrid inverter that is connected to a photovoltaic panel and outputs voltage in a single-phase two-wire system, a transformer unit that is provided in an electrical circuit between the hybrid inverter and a load and whose load side is adjusted for single-phase three-wire output, and an automatic switch between the inverter output voltage and the system voltage, the automatic switch being provided between the transformer and the load, or being configured with the hybrid inverter connected to the system.

In the off-grid type, an automatic switch is provided between the transformer and the load, and a power conditioner connected to the grid may also be provided.

The on-grid type is composed of a hybrid inverter connected to the grid including an automatic switch, and the transformer is made into a tap-changing transformer. By working in cooperation with a switch function unit capable of passing power current, the tap is switched according to the inverter output voltage and the grid voltage, so that a constant voltage is supplied to the load side regardless of which voltage is output.
If the neutral point side is also configured for switching in cooperation with the switch function unit, the transformer can be configured as a single-phase autotransformer.

The hybrid inverter may also be connected to a storage battery. In that case, charging can be performed using a single-phase two-wire system via a charger.

The input section of the hybrid inverter can be configured to selectively connect to a single-phase three-wire power source, including a grid, and a single-phase two-wire power source by linking it with a switch function section that can pass a power current.

The semi-independent solar power generation self-consumption system of the present invention can be constructed by combining and using other devices, primarily a hybrid inverter that is widely available at low cost overseas.

FIG. 1 is a single-line diagram of a quasi-independent photovoltaic power generation self-consumption system according to a first embodiment of the present invention. FIG. 2 is a double line diagram of the main part of FIG. 1; FIG. 11 is a single-line diagram of a quasi-independent photovoltaic power generation self-consumption system according to a second embodiment of the present invention. FIG. 4 is a double line diagram of the main part of FIG. 3 . FIG. 11 is a cross-sectional diagram of a main part of a semi-independent photovoltaic power generation self-consumption system according to a third embodiment of the present invention. FIG. 13 is a cross-sectional diagram of a main part of a quasi-independent photovoltaic power generation self-consumption system according to a fourth embodiment of the present invention. FIG. 13 is a cross-sectional diagram of a main part of a quasi-independent photovoltaic power generation self-consumption system according to a fifth embodiment of the present invention. FIG. 13 is a cross-sectional diagram of a main part of a quasi-independent photovoltaic power generation self-consumption system according to a sixth embodiment of the present invention.

A quasi-independent photovoltaic power generation self-consumption system 1 according to a first embodiment of the present invention will be described with reference to Figs.
The main component is a hybrid inverter 3. A PV panel (photovoltaic power generation panel) 5 is connected to the hybrid inverter 3 via a junction box 7, and a Batt (storage battery) 9 is also connected, both of which can be controlled. In addition, the inverter has a single-phase two-wire in (input section) and out (output section).
The DC voltage generated by the PV panel 5 or discharged from the Batt 9 is converted into an AC voltage, and is output as the inverter output voltage from a circuit connected to this out (output section).

This hybrid inverter 3 is an overseas specification, and the inverter output voltage is high at 220-240V, so it is passed through a transformer 11 to step down to the same 200V as the grid so that it can be similarly drawn into an indoor environment with specifications suitable for the grid. The output from the hybrid inverter 3 is limited to a certain voltage (for example, 240V), so the tap is fixed. In addition, since electricity is normally distributed from the grid in a single-phase three-wire system, the load side of the transformer 11 has a single-phase three-wire winding accordingly, and, as in the case of an AA output connected to the grid, 100V can be used using the middle neutral wire and the upper or lower voltage wire, and 200V can be used using the upper and lower voltage wires among the three wires.
This transformer 11 is composed of a single-phase compound transformer, but since this semi-independent solar power generation self-consumption system 1 is constructed off-grid and there is no risk of an earth loop occurring between the system and the grid, the transformer 11 may be composed of a low-cost, lightweight single-phase auto-transformer.

The circuit of the inverter output voltage converted to single-phase three-wire through the transformer 11 and the circuit of the system voltage supplied from the system are both connected to an automatic switch 13. Due to a priority setting function utilizing the built-in voltage monitoring of this automatic switch 13, the inverter output voltage is supplied preferentially to the load "at all times" and the system voltage is supplied "when there is a shortage."
In other words, the load side continues to receive a stable voltage just like an on-grid. Even during a power outage, the inverter output voltage continues to be supplied in "always" mode as long as Batt 9 is not empty.

The PV panel 5 may be connected to an electrical circuit between the grid and the automatic switch 13 via a PV-PCS (power conditioner) 15. By connecting in this way, any power exceeding the capacity can be sent to the grid.

The semi-independent photovoltaic power generation self-consumption system 1 is configured as described above, and while taking advantage of the cost benefits associated with building the system by using the hybrid inverter 3 and transformer 11, the system is also built off-grid, so electricity generated by photovoltaic power generation will not flow back into the grid during a power outage, except when connected to the PV-PCS 15. In addition, by using a commercially available product that has already been certified as the automatic switch 13, the system can be built without connecting an uncertified product to the grid.

In addition, an emergency power source such as a generator can be connected by using the in (input section) for single-phase/double-wire input of the hybrid inverter 3. If the voltage is 200-240V and the system is single-phase/double-wire type, the generator can be directly input with single-phase/double-wire input and stored in the Batt 9.
In this way, by making it possible to include input power sources other than solar power generation, the electricity stored in Batt 9 can be actively utilized not only at night, but also as a power source in emergencies such as disasters.
A USB (device) may be connected to the electric path between the Batt 9 and the hybrid inverter 3 via a Conv (USB converter) 17. If the Conv 17 is connected, a typical USB (device) such as a mobile phone can be directly charged even during a power outage.
This semi-independent photovoltaic power generation self-consumption system 1 is currently the most recommended type, as it is easy to introduce into an average household.

A quasi-independent photovoltaic power generation self-consumption system 19 according to a second embodiment of the present invention will be described with reference to Figs.
This semi-independent photovoltaic power generation self-consumption system 19 also mainly includes a hybrid inverter 3. However, the system is connected to the grid and constructed as an on-grid system, and the wiring configuration is different accordingly. In the operation mode of the hybrid inverter 3, the output priority is PV panel 5 → Batt 9 → grid.
A single-phase three-wire system is connected to the in (input section) of the hybrid inverter 3 in the form of a 200V D/A input using the upper and lower voltage lines. Also, a D/A voltage is output from the circuit connected to the out (output section), and this voltage has two types: the inverter output voltage and the system voltage. Due to the priority setting function built into the hybrid inverter 3, the inverter output voltage is supplied preferentially "at all times," and the system voltage is supplied "when there is a shortage."

Since there is a voltage difference between the inverter output voltage output from the hybrid inverter 3 and the system voltage, a transformer 21 is used to deal with this difference.
It is configured as a single-phase compound transformer, and like the transformer 11, the load side has a three-wire winding.
It is a tap-switching type with multiple taps on the input winding. The tap voltage is adjusted according to the type of voltage on the input side, so that the AA output from the transformer 21 is set to match the normal rated voltage, whether the D output is the inverter output voltage or the system voltage.

The tap switching is performed by utilizing a switch function unit 23 capable of passing a power current.
The voltage of the S/2 output is monitored by a voltage monitoring relay 23a, and a switch 23b is turned ON/OFF by the operation of the relay, and the tap connected by the tap changer 23c is changed.
The switch function unit 23 may be any device that can pass power current and may be constructed from a power semiconductor; however, there is always loss, and increasing the number of switches in an attempt to reduce this loss increases the risk, so a mechanical power relay is used here.
A power meter 25 is also provided to allow visual confirmation of the power supply status.
In addition, since electric vehicles (EVs) have become popular recently, an EV charging outlet 37 with a working voltage of 200-240 V may be connected to the output circuit of the hybrid inverter 3 so as to be used for charging the electric vehicle.

Because this semi-independent photovoltaic power generation self-consumption system 19 is connected to a grid, it cannot currently be introduced immediately in ordinary households in Japan. However, by making maximum use of the functions originally expected of the hybrid inverter 3, it has the advantage that the entire system can be compactly housed in a single housing, making it smart. Therefore, it is expected that connection requirements will be relaxed, such as allowing use if certification is obtained in the EU or USA, paving the way for introduction in ordinary households.

Also, as shown in the figure, a charger 35 may be connected separately to the batt 9 so that a small capacity input can be made possible. The hybrid inverter 3 is equipped with a charger, but this charger is for large capacity input. There are hybrid vehicles equipped with batteries and vehicles equipped with engines for generating electricity, and by passing through this charger 35, charging can be done safely at any time, and the amount of power drawn into the building can be increased even in the event that solar power generation is insufficient during a power outage.
If the voltage is stepped down through a transformer (not shown), it becomes possible to input 200V D-type power to the charger 35. Of course, a charger that uses 200V may also be used.

A quasi-independent photovoltaic power generation self-consumption system 27 according to a third embodiment of the present invention will be described with reference to FIG.
In this semi-independent photovoltaic power generation self-consumption system 27, a transformer 29 is used instead of the transformer 21 of the semi-independent photovoltaic power generation self-consumption system 19. Unlike the transformer 21, this transformer 29 is composed of a low-cost, lightweight single-phase autotransformer, with the primary winding and secondary winding connected. Therefore, in order to prevent the occurrence of an earth loop with the system side, the neutral point of the transformer and the neutral point of the AA input are also selectively switched by the neutral point switching unit 23d of the switch function unit 23.

A quasi-independent photovoltaic power generation self-consumption system 31 according to a fourth embodiment of the present invention will be described with reference to FIG.
From this embodiment onwards, a feature of the configuration is that the number of types of input power sources is increased, allowing them to be actively utilized during a power outage.
This semi-independent photovoltaic power generation self-consumption system 31 is configured so that, on the input power source side using in (input unit) of the semi-independent photovoltaic power generation self-consumption system 27, in addition to the AA input from the grid, a C input can also be selectively connected via a switch function unit 33 having a similar configuration linked to the switch function unit 23. With this wiring configuration, it is possible to switch to the AA input from the grid and also to input a C input from a 200V generator, which is relatively popular in Japan.
When only 200V single-ended input is used, the switch function unit 33 does not need to switch the neutral point, so the power relay may be configured as an SPDT.

A quasi-independent photovoltaic power generation self-consumption system 39 according to a fifth embodiment of the present invention will be described with reference to FIG.
This quasi-independent solar power generation self-consumption system 39 is a quasi-independent solar power generation self-consumption system 31, and on the input power source side using in (input unit), in addition to the power source derived from the grid, a 200V D input and a 100V D input can be used as input power sources, and these can be selectively connected via a single in (input unit).

The electric circuit on the 100V A-2 input side is passed through a transformer 41, where it is boosted to 200V and connected to the electric circuit for the 200V A-2 input. The transformer 41 is, for example, a 3kVA single-phase compound-wound transformer, and there is no need to consider polarity.
By configuring the wiring in this way, it is possible to input a large capacity of 100V.

A quasi-independent photovoltaic power generation self-consumption system 43 according to a sixth embodiment of the present invention will be described with reference to FIG.
This semi-independent solar power generation self-consumption system 43 is capable of inputting a large capacity of 100 V, like the semi-independent solar power generation self-consumption system 39, but the transformer 45 used in place of the transformer 41 is composed of a reduced-capacity 1.5 kVA single-phase compound transformer.
In this case, the input is inverted to accommodate a maximum of 3 kVA, so that a short circuit state at the time of inversion is avoided. A switch function unit 47 linked to the switch function unit 33 is provided, which switches between the 100 V D-type input side and the AA input side, and the switch function unit 33 switches between the output side of the switch function unit 47 and the 200 V D-type input side.
By configuring the wiring in this way, it is possible to input a large capacity of 100V using an inexpensive transformer.

Although the embodiment has been described in detail above, the specific configuration is not limited to this embodiment, and the invention also includes design changes within the scope of the present invention without departing from the gist of the present invention.
For example, in each of the above-described embodiments, the wiring configuration compatible with a small capacity of 100V can coexist with the wiring configuration compatible with a large capacity of 100V.
Furthermore, the structure of the automatic changeover switch 13 is not particularly limited, and various products currently on the market can be used.
Furthermore, in the embodiment, the electric circuit between the hybrid inverter and the load is configured with a transformer whose load side is adjusted for single-phase three-wire output, and the transformer is configured with a single transformer whose load side has a single-phase three-wire winding. However, since single-phase three-wire transformers are expensive and difficult to obtain, the electric circuit between the hybrid inverter and the load may be configured with, for example, two single-phase compound-winding transformers.

1...Semi-independent photovoltaic power generation self-consumption system (first embodiment)
3... Hybrid inverter 5... PV panel (photovoltaic power generation panel) 7... Junction box 9... Batt (storage battery) 11... Transformer 13... Automatic switch 15... PV-PCS (power conditioner)
17...Conv (USB converter)
19...Semi-independent photovoltaic power generation self-consumption system (second embodiment)
21: Transformer 23: Switch function unit 23a: Voltage monitoring relay 23b: Switch 23c: Tap changer 23d: Neutral point changer 25: Power meter 27: Semi-independent photovoltaic power generation self-consumption system (third embodiment)
29... Transformer 31... Semi-independent photovoltaic power generation self-consumption system (fourth embodiment)
33: Switch function unit 35: Charger 37: EV outlet 39: Semi-independent solar power generation self-consumption system (fifth embodiment)
41... transformer 43... semi-independent photovoltaic power generation self-consumption system (sixth embodiment)
45...Transformer 47...Switch function section

Claims (7)

A hybrid inverter that is connected to a solar panel and outputs voltage in a single-phase, two-wire system.
a step-down transformer unit provided in an electric path between the hybrid inverter and a load, the step-down transformer unit being adjusted for a single-phase three-wire output on the load side;
Equipped with an automatic switch between the inverter output voltage and the system voltage,
A quasi-independent solar power generation self-consumption system, characterized in that the automatic switch is provided between the transformer and the load, or is configured by the hybrid inverter connected to a grid. The quasi-independent solar power generation self-consumption system according to claim 1,
An automatic switch is provided between the transformer and the load, and
A quasi-independent photovoltaic power generation self-consumption system further comprising a power conditioner connected to a grid. In the semi-independent solar power generation self-consumption system according to claim 1,
The automatic switch is composed of a hybrid inverter connected to the grid, and the transformer is a tap-changing transformer.
A semi-independent solar power generation self-consumption system that switches taps according to the inverter output voltage and the grid voltage in cooperation with a switch function unit capable of passing power current, thereby supplying a constant voltage to the load side regardless of which voltage is output. In the semi-independent photovoltaic power generation self-consumption system according to claim 3,
A semi-independent photovoltaic power generation self-consumption system that also switches the neutral point side in cooperation with a switch function unit. In the semi-independent photovoltaic power generation self-consumption system according to claim 4,
A semi-independent solar power generation self-consumption system, characterized in that the transformer is composed of a single-phase autotransformer. In the semi-independent solar power generation self-consumption system according to claim 1,
A quasi-independent solar power generation self-consumption system, characterized in that the hybrid inverter is further connected to a storage battery, and the storage battery can be charged using a single-phase two-wire system via a charger. In the semi-independent solar power generation self-consumption system according to claim 1,
A semi-independent photovoltaic power generation self-consumption system characterized in that the input section of the hybrid inverter can be selectively connected to a single-phase three-wire power source including a grid and a single-phase two-wire power source by cooperating with a switch function section capable of passing a power current.

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