KR20140101207A - Distributed power generation system and control method thereof - Google Patents

Abstract

The present invention relates to a distribution type generation system which allows each of power converters to be in connection with another power converter by outputting the identical phase current waveform in a nonutility power generation process, and a control method for the same. For this, the distribution type generation system of the present invention is preferably configured as follows: When power of a power system is disconnected, preceding generation of a main power converter is instructed after only a self-line switch is closed to supply output waveform, which is generated later from a power converter by nonutility power generation, to a load. When the main power converter generates and outputs output waveform according to the preceding generation instruction, nonutility power generation of a sub-power converter is instructed. The sub-power converter generates and outputs output waveform with the same phase as the phase of the output waveform from the main power converter according to the output waveform output on an AC line which is generated by the nonutility power generation of the main power converter. Accordingly, in the system of the present invention, power converters generate output waveform of the same phase in the nonutility power generation process, and thus bulk power can be supplied by connecting the power converters in parallel.

Description

[0001] DISTRIBUTED POWER GENERATION SYSTEM AND CONTROL METHOD THEREOF [0002]

The present invention relates to a distributed generation system and a control method thereof, and more particularly, to a distributed generation system and a control method thereof, which can output a current waveform of the same phase in each power converter during independent power generation, ≪ / RTI >

FIG. 1 schematically shows the configuration of a distributed power generation system. In the distributed power generation system, several power generation generators 40 are connected in parallel to supply power.

The distributed power generation system may be operated in a grid-connected type in which the generated power is supplied to the power system 10 in conjunction with the power system 10, When the power system 10 is disconnected, the power system 10 may be operated as a self-sustaining power generation system that can be used as an emergency power source.

First, when operated in the grid-connected type, the distributed generation system generates a large amount of electric power by connecting a plurality of small-sized power generation power sources 40 in parallel, and supplies the generated electric power to the connected power system 10 do.

At this time, power converters (PCS) 30 connected to the respective power generation sources 40 constituting the distributed generation system generate current waveforms of the same phase in accordance with the AC voltage waveform of the power system 10 Output.

When the distributed power generation system is connected to the grid, the switch 20 can be added for safety. When the number of the power converters 30 is large or the capacity is large, the power converters 30 are grouped, (20) may be used.

In FIG. 1, a generator 40 is implemented by various methods such as solar power generation, photovoltaic power generation, wind power generation, and fuel cell power generation to generate electric power, and it is possible to directly generate direct current (DC) (AC) power.

When the generating power source 40 generates direct current power, it is directly supplied to the power converter 30. In the case of generating alternating current power, the rectifier may be used to change the direct current power. Depending on the power converter 30, a circuit for converting AC power into DC power may be incorporated in the power converter 30. [ Generally, a photovoltaic system or a fuel cell power generation system generates DC power, and a wind power generation system generates AC power.

On the other hand, when the power system 10 is disconnected from the power system due to interruption, cutting, or the like of the system line 1, the distributed generation system operates in a self-sustaining power generation mode. The power converter 30 is provided with a self-sustaining operation output terminal or a self-sustaining line 4 as shown in FIG. 2 so that the power generated by the power converter 30 can be used as an emergency power source for a load (not shown).

The power converter 30 is connected to the AC line 2 or the load (not shown) connected to the power system 10 by using the AC line disconnection 33 and the self-standing line switch 35 so that self- The power can be connected to only one of the free standing lines 4 and the power of the AC line 2 of the power system 10 is applied to a load (not shown).

In this way, when the power converter 30 is operated in the independent power generation mode, since the AC voltage waveform of the power system 10 does not exist, different output waveforms are generated and output, Can not be connected in parallel with the other power converter (30).

Therefore, when the self-sustaining generation output is to be used, one power converter 30 must supply all of the power required in the load (not shown). Therefore, the self-sustaining generation method is generally provided only in the generation system of 3 KW or more.

As described above, in the conventional distributed power generation system, since the output of one power converter is small, it is difficult to use the self-sustaining generation system. Even if the power is provided by the self-sustaining power generation system, There is a problem that power can not be provided.

Therefore, a separate self-sustaining output line can be added to the power converter 30 to provide self-sustaining power generation in a small capacity power generation system. However, a method of adding a separate self-supporting output line increases the installation and production cost of the power converter 30, which is a cause of hindering downsizing of the power converter 30. [

Korean Patent Publication No. 2012-134875

SUMMARY OF THE INVENTION The present invention has been conceived to solve the above-described problems, and it is an object of the present invention to provide a power converter in which a power converter set as a main power converter first generates an output waveform through independent power generation, And a plurality of power converters connected in parallel to each other so as to provide a large amount of electric power, and a control method therefor The present invention has been made in view of the above problems.

It is another object of the present invention to provide a power supply system which is capable of providing a power supply from a power supply to a power converter when power system power is disconnected, To a controller that selectively connects to a line, and a control method thereof.

According to an aspect of the present invention, there is provided a distributed generation system including a plurality of power generation sources connected in parallel, the distributed generation system including a plurality of power converters A main power converter comprising any one of; A sub-power converter comprising a power converter other than the main power converter; And a controller for selectively connecting an output waveform generated by the plurality of power converters to one of a system line connected to the power system and an independent line connected to the load, wherein the main power converter comprises: And the sub-power converter generates an output waveform having the same phase on the basis of the output waveform generated in the main power converter, in accordance with the self-sustaining generation instruction of the controller, It is preferable to generate and output it.

Meanwhile, a method of controlling a distributed generation system according to an embodiment of the present invention includes the steps of: closing a grid line switch only in a controller when a power source of the power system is alive, and instructing grid-connected power generation to each power converter; Closing the self-standing line switch only in the controller when the power supply of the power system is disconnected, and instructing the main power converter to perform power generation; Generating and outputting an output waveform according to a power generation instruction in the main power converter; Generating an output waveform from the main power converter and outputting the generated output waveform to the main power converter; And generating and outputting an output waveform having the same phase according to an output waveform generated in the main power converter according to a self-sustaining generation instruction in the sub-power converter.

According to the distributed power generation system and the control method therefor of the present invention, even when the power system power source is disconnected and the distributed power generation system develops independently, each power converter generates an output waveform having the same phase, Thereby providing a large capacity of power. In particular, parallel power generation systems using a micro power converter can provide a large-capacity independent power generation output.

Therefore, even if the power system is cut off due to interruption or cutting of the system line, the power generated by each power converter can be used as the emergency power source of the load by switching to the independent power generation.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing a configuration of a general distributed generation system; Fig.
2 is a schematic view showing a configuration of a general power converter;
3 schematically shows the configuration of a distributed generation system according to an embodiment of the present invention.
4 is a schematic view showing an internal configuration of a controller applied to the present invention.
5 is a process chart for explaining a distributed power generation system control method according to an embodiment of the present invention;

Hereinafter, a distributed power generation system and a control method thereof according to preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a diagram schematically showing a configuration of a distributed power generation system according to an embodiment of the present invention. The power generator 400 includes a switch 200, a controller 300, a power converter 400 (400-1, 400-2, ..., 400 -n, and a generating power source 500.

In this configuration, the switch 200 is installed between the power system 100 and the controller 300 to cut off the connection between the distributed generation system and the power system 100.

The controller 300 outputs the output waveforms generated from the plurality of power converters 400 to 400 through 400 to the system line 101 connected to the power system 100 and the load 400-2, ..., 400-n when the power of the power system 100 is alive. The power converter 100 is connected to the power line 100, 400-2,..., 400-N when the power system 100 is disconnected from the power line 100, n to an independent line 104 connected to a load (not shown).

In more detail, when the power of the power system 100 is alive, the controller 300 converts the output waveforms generated by the power converters 400 (400-1, 400-2, ..., 400-n) (400-1, 400-2,..., 400-n) to the grid lines 101 connected to the grid 100 and instructs the power converters 400: 400-1, 400-2,.

Each of the power converters 400 (400: 400-1, 400-2, ..., 400-n) instructed by the controller 300 to generate grid-connected power is connected to each of the power converters 400 (The voltage waveform of the power system) placed on the AC line 102 connected in parallel to the AC line 102, ..., and 400-n, Generate and output a waveform.

At this time, each of the power converters 400 (400-1, 400-2, ..., 400-n) preferably performs a maximum power point tracking (MPPT) operation to produce the maximum power.

Each of the power converters 400 (400: 400-1, 400-2, ..., 400-n) operating as described above supplies a voltage to the AC line 102 without an instruction (grid- It is preferable to perform the grid-connected power generation after a predetermined time (for example, 30 seconds).

On the other hand, if the power source of the power system 100 is disconnected due to power interruption, cutting or breaking of the power line 101, the controller 300 senses the power source alone and outputs power to the power converters 400 (400-1, 400-2,. 400-2, ..., 400-n is blocked from being applied to the power system 100, and a power stop command is transmitted to each of the power converters 400 (400-1, 400-2, ..., 400-n) do.

As described above, the power converters 400 (400: 400-1, 400-2, ..., 400-n), which have received the power generation stop command from the controller 300, immediately stop generating power according to the power generation stop command, (The power converter is operated in a state where the power of the system is disconnected, in which case the power converter and the electric device are damaged) And may cause a safety problem such as an electric shock), thereby stopping the power generation. Accordingly, when the voltage of the AC line 102 drops below the predetermined voltage in the absence of the function of detecting the sole operation, the controller 300 does not necessarily have a function of detecting the sole operation. .

After sending the power down commands to the respective power converters 400: 400-1, 400-2, ..., 400-n, the controller 300, through self-sustained power generation, 400-2,..., 400-n to be applied to a load (not shown), and then controls the connection to the power converter 400-1 set as the main power converter When the main power converter 400-1 generates an output waveform through self-sustained power generation and outputs it, the sub power converters 400-2, ..., 400-n direct the self-sustained power generation.

The power converters 400 to 400-n may be connected to the plurality of power generation sources 500 to supply power supplied from the power generation source 500 to the power system 500 400-1, 400-2, ..., 400-n are connected to one main power converter 400-1 and the remainder of the main power converter 400-1. And sub-power converters 400-2, ..., 400-n.

The main power converter 400-1 generates an output waveform according to a power generation instruction received from the controller 300 when the power of the power system 100 is disconnected and outputs the generated waveform to the AC line 102. [

At this time, when the main power converter 400-1 is instructed to generate power by the controller 300, the main power converter 400-1 starts voltage-following power generation so as to generate a specified voltage (reference voltage) Is not to exceed 50% of the maximum output.

As described above, when the main power converter 400-1 starts the voltage-follow-up power generation according to the power generation instruction of the controller 300, the controller 300 controls the sub power converters 400-2, ..., 400- Power converters 400-2 to 400-n which instruct the self-sustaining generation from the controller 300 and the main power converter 400-1 are connected to the AC line 102 through self- To generate an output waveform having the same phase as the output waveform output from the main power converter 400-1 and to output the output waveform.

As described above, since the sub power converters 400-2, ..., 400-n start to generate self-sustaining power to generate and output an output waveform having the same phase as that of the main power converter 400-1, The voltage is increased.

The power converters 400 (400: 400-1, 400-2, ..., 400-n) may be implemented as a micro-inverter of 1 kW or less.

The main power converters discussed above are not defined as specific power converters and may select any one of a plurality of power converters (400: 400-1, 400-2, ..., 400-n) coupled to a distributed power generation system, Converter 400-1. Accordingly, when the power converter 400-1 designated by the main power converter stops power generation due to a failure or the like, the remaining sub-power converters 400-2, ..., 400-n sense the single operation, The controller 300 checks the failure of the main power converter 400-1 when the self-sustained power generation is stopped due to an abnormal situation of the main power converter 400-1, and then the auxiliary power converters 400-2, ..., , 400-n) to the main power converter 400-2 to resume self-sustained power generation.

On the other hand, when the generated power is larger than the load required by the load (not shown) connected to the self-standing line 104, the voltage across the AC line 102 rises above the reference voltage, The sub-power converters 400-2,..., 400-n decrease the amount of output current so that the voltage of the AC line 102 becomes the reference voltage.

When the load required by a load (not shown) connected to the free-standing line 104 is larger than the generated power, the voltage across the AC line 102 falls below the normal voltage. The AC line 102, The sub-power converters 400-2,..., 400-n increase the output current amount so that the voltage of the AC line 102 becomes the reference voltage. At this time, it is preferable that the sub-power converters 400-2, ..., 400-n do not exceed the specified rated output.

The controller 300 and each of the power converters 400-1 to 400-n perform the communication by being connected by various communication methods. For example, the controller 300 and the power converters 400-1 to 400- Serial communication, wireless communication, PLC (Power Line Communication) or the like can be used.

In the embodiment of the present invention, the controller 300 is implemented as an independent device. However, the controller 300 may be integrated into the power converter 400-1 configured as a main power converter. In this case, it is preferable that the communication between the controller 300 and the main power converter 400-1 uses internal communication such as a serial communication interface (SCI), a serial peripheral interface (SPI), and a universal asynchronous receiver / transmitter (UART) .

4 is a diagram schematically showing the internal structure of a controller according to the present invention. The system includes a line switch 310, a self-standing line switch 320, a controller 330, a main power supply 340, and an auxiliary power supply 350 .

The system line switch 310 is closed under the control of the control unit 330 and outputs the output waveforms generated by the plurality of power converters 400 (400-1, 400-2, ..., 400-n) And to the system line 101 connected to the power system 100.

The self-standing line switch 320 is closed under the control of the control unit 330 and outputs an output waveform generated from the plurality of power converters 400 (400-1, 400-2, ..., 400-n) To the self-standing line 104 connected to the self-supporting line (not shown).

The control unit 330 closes the grid line switch 310 when the power of the power system 100 is active and opens the self-standing line switch 320 to supply power to the plurality of power converters 400: 400-1, 400-2, 400-2, ..., 400-n to be supplied to the power system 100, and then instructs the respective power converters 400 (400-1, 400-2, ..., 400-n) do.

When the power line 100 is disconnected from the power line 100, the line line line switch 310 is opened while the line line line switch 320 is closed, and then the plurality of power converters 400 2,..., 400-n is supplied to a load (not shown), and then instructs the main power converter 400-1 to start power generation and supplies power to the main power converter 400 - 1 starts to generate and output an output waveform through independent power generation, the sub power converters 400 - 2,.

The main power supply unit 340 receives power from the power system 100 and applies the power to the control unit 330. The main power supply unit 340 supplies power from the power system 100 to the main power supply unit 340, And supplies power to the controller 330 through the line 301. [

The auxiliary power unit 350 supplies power to the controller 300 when there is power supplied to the power converters 400 (400-1, 400-2, ..., 400-n) when the power system 100 is powered off The auxiliary power supply unit 350 supplies power from the power supply line 500 to the power converters 400 (400-1, 400-2, ..., 400-n) And supplies power to the controller 330 through the input line 302.

Since each of the power generating sources 500 is independent of each other, the power source line 103 connecting the power generating source 500 and the power converters 400 (400-1, 400-2, ..., 400-n) There are also several. Therefore, it is preferable that the power line 103 connected to the auxiliary power line 302 is connected to the power line 103, which is located closest to the controller 300 or is conveniently connected to the controller 300 .

As described above, when the auxiliary power unit 350 receives power directly from the generator power source 500 and applies the power to the controller 330, the controller 300 operates only when there is an output of the generator power source 500, The output waveforms output from the power converters 400 (400-1, 400-2, ..., 400-n) can be supplied to a load (not shown).

The auxiliary power unit 350 may be supplied with power from at least two power generating units 500. In this case, the power converters 400 (400-1, 400-2, It is preferable that the auxiliary power supply unit 350 uses an isolation type power supply circuit such as a flyback converter in order to prevent malfunction of the power supply units 400, ..., 400-n.

5 is a process chart for explaining a distributed power generation system control method according to an embodiment of the present invention.

First, when the power of the power system 100 is active and the grid-connected power generation has to be performed (S10), the controller 300 closes the grid line switch 310 and opens the self-bridge line switch 320 S12), and instructs grid-connected power generation to each of the power converters 400 (400-1, 400-2, ..., 400-n) (S14).

Each of the power converters 400 (400: 400-1, 400-2, ..., 400-n) instructed to generate grid-connected power from the controller 300 through the above-described process S14 receives the voltage waveform And generates and outputs an output waveform having the same phase as the voltage waveform stored in the AC line 102 in accordance with the current tracking method (S16).

The power converters 400 (400-1, 400-2, and 400-4) which generate and output output waveforms having the same phase to each other in accordance with the voltage waveform (voltage waveform of the power system) carried on the AC line 102 through the above- 2,..., 400-n receives the power generation stop command from the controller 300 or satisfies the power generation stop condition such as detection of the stand alone operation (S18).

In the meantime, when power supply to the power system 100 is cut off due to interruption or cutting of the grid line 101 (S10), the controller 300 controls the grid line switch 310 to open , The self-standing line switch 320 is closed (S22), and then the main power converter 400-1 instructs the power generation (S24).

In step S24, the main power converter 400-1, which has been instructed to generate power from the controller 300, starts voltage-based power generation to generate a specified voltage (reference voltage) and outputs it to the AC line 102 S26). When the main power converter 400-1 outputs the reference voltage, the controller 300 instructs the remaining sub converters 400-2, ..., 400-n to perform self-sustained power generation (S28).

In the sub-power converters 400-2, ..., 400-n that are instructed to generate the self-sustaining power from the controller 300 through the above-described process S28, the main power converter 400-1 is connected to the AC line 102 The current follow-up power generation is started in accordance with the output voltage waveform, and an output waveform having the same phase as the output waveform output from the main power converter 400-1 is generated and output (S30).

The main power converter 400-1 and the sub-power converters 400-2, ..., 400-n, which generate and output the output waveforms having the same phase through the above-described steps S24 to S30, When the stoppage command is received, or when the power generation stop condition such as single operation is detected (S32), the power generation is immediately stopped (S34).

The distributed power generation system and the control method thereof according to the present invention are not limited to the above-described embodiments but can be variously modified and practiced within the scope of the technical idea of the present invention.

100. Power system, 200. Switch,
300. Controller, 310. Grid line switch,
320. Self-standing line switch, 330. Control,
340. Main power section, 350. Auxiliary power section,
400. Power converter, 500. Power generator

Claims (8)

A distributed power generation system comprising a plurality of power generation power sources connected in parallel,
A main power converter comprising any one of a plurality of power converters connected to the power generation power source;
A sub-power converter comprising a power converter other than the main power converter; And
And a controller for selectively connecting an output waveform generated by the plurality of power converters to one of a system line connected to the power system and an independent line connected to the load,
The main power converter generates and outputs an output waveform according to a power generation instruction received from the controller when the power system is disconnected,
Wherein the sub-power converter generates and outputs an output waveform having the same phase based on an output waveform generated in the main power converter, in accordance with an independent generation instruction of the controller.
2. The apparatus of claim 1,
A system line switch connected to an output line of the plurality of power converters to a power line connected to the power system;
An autonomous line switch connected to an independent line connected to the load, the output waveform being generated by the plurality of power converters;
A controller which closes only the grid line switch when the power of the power system is alive and closes only the self-standing line switch when power of the power system is disconnected;
A main power supply unit for receiving power from the power system and applying the power to the control unit when the power system is live; And
And an auxiliary power unit for receiving the power from the power generation power source connected to the controller and applying the power to the control unit when the power system is disconnected from the power system.
3. The apparatus of claim 2,
When the power of the power system is alive, only the grid line switch is closed, grid-connected power generation is instructed to each power converter,
When the power supply system is disconnected, only the self-standing line switch is closed, and when the main power converter starts generation of an output waveform through independent power generation after instructing the power generation by the main power converter, A distributed generation system that directs self-sustaining development.
2. The apparatus of claim 1,
A distributed generation system that resumes self-sustained power generation by switching any of the sub-power converters to the main power converter when the self-sustained power generation stops due to abnormal conditions of the main power converter during self-sustained development.
The distributed generation system according to claim 1, wherein the maximum power generation amount of the main power converter does not exceed 50% of the maximum power at the time of independent power generation.
The power converter according to claim 1,
Decreases the amount of output current when the voltage of the AC line connected to itself is higher than the reference voltage and increases the amount of output current when the voltage of the AC line is lower than the reference voltage.
The power converter according to claim 1, wherein the main power converter and the sub-
Wherein the power converter is implemented as a micro-inverter of 1 kW or less.
Closing the grid line switch only in the controller when the power system power source is alive, and instructing grid-connected power generation to each power converter;
Closing the self-standing line switch only in the controller when the power supply of the power system is disconnected, and instructing the main power converter to perform power generation;
Generating and outputting an output waveform according to a power generation instruction in the main power converter;
Generating an output waveform from the main power converter and outputting the generated output waveform to the main power converter; And
And generating and outputting an output waveform having the same phase according to an output waveform generated in the main power converter according to a self-sustaining generation instruction in the sub-power converter.

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