JPH08182192A - System interconnection system for private DC power generation equipment - Google Patents

Abstract

(57) [Summary] [Purpose] When switching the power supply system between the power system and the customer's private DC power generation equipment, the power supply is not temporarily interrupted, and the load capacity on the customer premises is not affected. To provide a system interconnection system for private DC power generation equipment that can have its own private power generation capacity without having to control the amount of power generation. A DC converter for converting AC power of a power system into DC power, and a first DC power converted by the DC converter and a second DC power from a private DC power generation facility to the second DC power. And an inverse conversion device that reversely converts the above into the AC power by giving priority to the first DC power, and the AC power output from the inverse conversion device is supplied to the load in the customer premises.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system interconnection system for connecting a private DC power generation facility to an electric power system.

[0002]

2. Description of the Related Art Conventionally, many factories, buildings, schools, hospitals, various facilities, etc. are equipped with private power generation facilities to prepare for an emergency such as a power outage. The private power generation facilities include AC power generation facilities that generate alternating current power using rotating machines such as diesel engines, gas engines, gas turbines, and alternating current generators, and direct current power generation that generates direct current power such as solar cells and fuel cells. There is equipment, and in a broad sense, there is also one that converts the AC output of the generator by wind power generation into DC power with a DC converter, and one that converts AC power from the above AC generator into DC power with a DC converter. Included in DC power generation equipment.

By the way, as a recent tendency, a rotating machine such as a diesel engine, a gas engine, a gas turbine and an AC generator are used to generate necessary electric power, and
So-called cogeneration equipment that uses heat generated at the same time, which is used in combination with electric heat, is drawing attention from the viewpoint of effective use of energy. It is being introduced. When such a cogeneration type private power generation facility is operated by a so-called thermal main power subordinate operation with a thermal load as the main component, if it is a large-scale private power generation facility, the quality of the generated power is excellent and the maintenance and operation of the facility is reliable Therefore, a so-called reverse flow that allows surplus power to flow to the power system is permitted under specified conditions.

On the other hand, the reverse flow of the electric power obtained by converting the DC power generated by the private power generation equipment using the DC power generation equipment such as the solar cell and the fuel cell into the AC power using the inverse conversion device is of a certain scale or more. Has recently been recognized.

However, in a small-scale cogeneration type private power generation facility for household use, the quality of generated power is slightly inferior to that of a large-scale private power generation facility due to cost constraints, and the reliability of maintenance operation is high. Since it has to be somewhat low, it is said that it is not preferable to connect the power system to the power system under the same conditions as a large-scale cogeneration type private power generation facility, and it is not currently accepted. .

However, even in a small-scale cogeneration-type private power generation facility, surplus power is generated if the thermal main power slave operation is performed, and in the case of a customer equipped with a non-cogeneration-type private power generation facility, power is generated. In some cases, it may be advantageous in terms of operating economy to use the electric power generated by the private power generation equipment rather than purchasing electricity from the grid.

Therefore, in the case of such a case, a customer conventionally equipped with a private DC power generation facility (for example, a combination of a gas engine, an AC generator and a DC converter) in which system interconnection is not recognized is shown in FIG. As shown in the figure, the contact of the switching device 1 provided in the middle of the power supply line is switched from a to b, and the power used is changed from the power system up to that point to the private DC power generation facility 2
The method of switching to is adopted. Reference numeral 3 is an inverse conversion device such as an inverter that converts the DC power generated by the private DC power generation facility 2 into AC power having the same frequency and phase as the power system.

[0008]

However, in such a method, since the power supply to the load 8 in the customer premises is temporarily cut off when the power supply is switched from the power system to the private DC power generation equipment 2, the power supply is stopped. There is a problem when the inside load is OA equipment or video equipment. Also, once the power source is switched, the private DC power generation equipment 2 must supply power to the load 8 on the customer premises at all, so the private DC power generation equipment 2 can generate the power consumption of the load 8 on the customer premises. Must be equipped with. Furthermore, even if the power generation capacity of the power generation equipment is sufficient, it is necessary to control the amount of generated power so as to match the power consumption of the load 8. Therefore, a circuit and equipment for that purpose are required, and a small scale. There is a problem that private power generation equipment cannot meet the demand.

The present invention has been made in view of the above points, in which the power supply is not temporarily interrupted when the power supply system is switched, and a unique private power generation capacity is provided regardless of the load capacity in the customer premises. An object of the present invention is to provide a system interconnection system for private DC power generation equipment that can be owned and does not need to control the amount of generated power.

[0010]

According to a first aspect of the present invention, in order to achieve the above object, a DC converter for converting AC power of a power system into DC power, and a DC converter are provided. An inverse conversion device for inversely converting the converted first DC power and the second DC power from the private DC power generation facility into AC power, and prioritizing the second DC power over the first DC power The reverse converter is supplied with power, and the AC power output from the reverse converter is supplied to the load on the customer premises.

According to the second aspect of the present invention, the first private power generation facility capable of grid interconnection with the power of the power grid and the second private DC power generation facility not capable of grid interconnection are powered. In a grid interconnection system that is grid-connected to a grid, a DC converter that converts the power of the power grid and the first AC power obtained from the first private power generation facility to DC power, and the DC converter And a reverse converter for reversely converting the converted first DC power and the second DC power from the second private DC power generation facility into AC power.
Power of the AC power is prioritized over the power of the power system to supply power to the DC conversion device, and the second DC power is prioritized over the first DC power to supply power to the inverse conversion device. The second AC power output from the power supply unit is configured to supply the load on the customer premises.

[0012]

According to the present invention, the electric power of the electric power system is once converted into the DC power by the DC converter, and is combined with the DC power by the private DC power generation equipment at this stage, and then the AC power is again converted by the inverse converter. It is converted back to electric power and supplied to the load on the customer premises. Since the power of the power system is once converted into DC power by the DC converter, the quality of the power on the DC power side does not affect the power system.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit configuration of an embodiment of a system interconnection system according to the present invention. In the figure, reference numeral 2 denotes a private DC power generation facility provided in a consumer, which is composed of, for example, a gas engine, an AC generator, and a DC converter. Reference numeral 4 is a DC converter for converting AC power of the power system into DC power, and 5 is reverse conversion for reversely converting DC power generated by the private DC power generation facility 2 and DC power converted by the DC converter 4 into AC power. A device, 6 is a switchgear connected in the middle of a power supply line to a load on the customer premises, 7 is a switchgear that is closed in the event of an abnormality such as a failure, and 8 is a load on the customer premises.

In normal times, the opening / closing device 6 is closed and the opening / closing device 7 is closed.
Keep it open. In this state, the AC power from the power system is once converted into DC power by the DC converter 4, and is converted back into AC power by the inverse converter 5, and is transferred to the load 8 in the customer premises via the switchgear 6. Power is supplied. At this time, if the private DC generator 2 is also operating and DC power is generated, the output terminal voltage of the private DC generator 2 under no load is set to be slightly higher than the output terminal voltage of the DC converter 4. If this is done, the load on the customer premises 8
The power generated by the private DC power generation facility 2 is supplied to the power source in preference to the power of the power grid. If the terminal voltage of the private DC power generation equipment 2 is made to decrease with an increase in the output current, the power is preferentially supplied to the load 8 until it matches the output terminal voltage of the DC converter 4. So
There is no need to intentionally switch the power supply source to the load 8 from the power system to the private DC power generation facility 2. When the power consumption of the load 8 exceeds the amount at which the output terminal voltage of the private DC generator 2 matches the output terminal voltage of the DC converter 4, the shortage is covered by the power from the DC converter 4. Be seen. Therefore, the power generation capacity of the private DC power generation facility 2 can be set to an electric power amount close to the frequency of use by the consumer, and it is not necessary to control it according to the electric power consumption amount of the load 8.

When any one of the DC converter 4, the reverse converter 5 and the private DC generator 2 fails, the switchgear 6 is opened and the switchgear 7 is closed so that the load 8 on the customer premises is Power is directly supplied from the power system via the power supply circuit 9.

FIG. 2 shows a circuit configuration of another embodiment of the system interconnection system according to the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same components, and the description thereof will be omitted.

In this embodiment, reference numeral 10 denotes a private power generation equipment composed of a DC power generator such as a solar cell and an inverse converter for reversely converting the DC generated power into AC power. Electric power has a high enough quality to be connected to the power grid. 8a is a load on the customer's premises that consumes high-quality AC power of the power system or private power generation facility 10, and 8b consumes DC power from the private DC power generation facility 2 converted to AC power by the reverse converter 5. This is the load on the customer premises.

During normal times, the opening / closing device 6 is closed and the opening / closing device 7 is closed.
Keep it open. In this state, the AC power from the power grid is supplied to the load 8a on the customer premises, and
The direct-current converter 4 once converts the direct-current power into the direct-current power, the reverse-converter 5 converts the direct-current back into alternating-current power, and the power is supplied to the load 8b in the customer premises through the switchgear 6. At this time, if the private power generation facility 10 and the private DC power generation facility 2 are also operating and generating power, the output terminal voltage of each without load is determined as the terminal voltage of the power system and the output terminal voltage of the DC converter 4. If it is set slightly higher, the generated power of the private power generation equipment 10 is preferentially supplied to the loads 8a and 8b on the customer premises over the power of the power system, and the load 8b on the customer premises is used for private use. The power generated by the DC power generation facility 2 is preferentially fed over the power converted by the inverse converter 5. Therefore, private power generation equipment 10
As long as the private DC power generation equipment 2 is generating power, the electric power is preferentially supplied to the loads 8a and 8b. Therefore, the power supply source for the loads 8a and 8b is intentionally changed from the power grid to the private power generation equipment 10 or It is not necessary to switch to the private DC power generation facility 2. When the power consumption of the load 8b exceeds the amount at which the output terminal voltage of the private DC power generation equipment 2 matches the output terminal voltage of the inverse conversion device 5, the shortage is first covered by the power from the private power generation equipment 10. If there is still a shortage, the power of the power system from the DC converter 4 is used. Therefore, the power generation capacities of the private DC power generation equipment 10 and the private DC power generation equipment 2 can be set to the amount of electric power that is close to the frequency of use by the consumer, and it is not necessary to control the electric power consumption according to the power consumption of the loads 8a and 8b. Also in this embodiment, when any of the DC converter 4, the inverse converter 5, and the private DC power generation equipment 2 fails, the switchgear 6 is opened and the switchgear 7 is closed to apply the load 8b on the customer premises. Is fed directly from the power system via the feeding circuit 9.

In this embodiment, the same effect as that of the embodiment of FIG. 1 is obtained, and when the private power generation facility 10 has surplus power, the quality of the power is high and therefore reverse power flow to the power system is possible. is there.

[0021]

As described above, according to the invention described in claim 1, since it is not necessary to switch the power supply system from the power system to the private DC power generation equipment, the power supply to the load of the customer is cut off. Never. Therefore, there is no problem even if loads such as OA equipment and video equipment are used. Electric power that cannot be covered by private DC power generation equipment is supplied from the power grid, so it is possible to set the power generation capacity of private DC power generation equipment to the frequency of use by customers, and control according to the power consumption of customers. No need. Further, when the cogeneration system is adopted in the private DC power generation equipment, it is possible to perform the thermal main power subordinate operation in accordance with the heat load of the customer.

According to the third aspect of the invention, the surplus power of the first private power generation facility capable of generating high quality power can be reversely flown to the power system.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of an embodiment of an interconnection system system for a private DC power generation facility according to the present invention.

FIG. 2 is a circuit configuration diagram of another embodiment of the interconnection system system for private DC power generation equipment according to the present invention.

FIG. 3 shows a circuit configuration diagram of an example of a conventional interconnected system of a private DC power generation facility.

[Explanation of symbols]

 2 Private DC power generation equipment 4 DC conversion device 5 Inverse conversion device 6, 7 Switchgear 8, 8a, 8b Load on customer premises 9 Power supply circuit 10 Private power generation equipment

Claims (5)

[Claims] 1. A direct current converter for converting alternating current power of a power system into direct current power, and first direct current power converted by the direct current converter and second direct current power from a private direct current power generation facility are reversed to alternating current power. An inverse conversion device for converting the second direct current power over the first direct current power to supply power to the inverse conversion device, and the alternating current power output from the inverse conversion device is in the customer premises. A system interconnection system for private DC power generation equipment, characterized in that it is connected so as to be fed to a load. 2. The grid interconnection system according to claim 1, further comprising a power feeding circuit that feeds power from the power grid to a load in the customer premises without passing through the DC converter and the inverse converter. 3. A first system capable of system interconnection with power of a power system
In the grid interconnection system in which the private power generation equipment of No. 2 and the second private DC power generation equipment that cannot be grid-connected are grid-connected to the power grid, from the power of the power grid and the first private power generation equipment A DC converter for converting the obtained first AC power into DC power, and the first DC power converted by the DC converter and the second DC power from the second private DC power generation facility to AC power. An inverse conversion device for performing an inverse conversion, prioritizing the first AC power over the power of the power system to supply power to the DC conversion device, and supplying the second DC power to the first DC power.
DC power for private use is supplied to the inverse conversion device in priority to the DC power of the second conversion device, and the second AC power output from the inverse conversion device is connected so as to be supplied to the load in the customer premises. A grid interconnection system for power generation equipment. 4. The grid interconnection system according to claim 3, further comprising a power feeding circuit that feeds power from the power grid to the load in the customer premises without passing through the DC converter and the inverse converter. 5. The grid interconnection system according to claim 3, wherein the grid and the first AC power are connected so as to be fed to a load different from the load in the customer premises.