KR20160082825A - Inverter System Connected to Power Grid based on Communication and Method for Controlling The Same - Google Patents

Inverter System Connected to Power Grid based on Communication and Method for Controlling The Same Download PDF

Info

Publication number
KR20160082825A
KR20160082825A KR1020140192335A KR20140192335A KR20160082825A KR 20160082825 A KR20160082825 A KR 20160082825A KR 1020140192335 A KR1020140192335 A KR 1020140192335A KR 20140192335 A KR20140192335 A KR 20140192335A KR 20160082825 A KR20160082825 A KR 20160082825A
Authority
KR
South Korea
Prior art keywords
voltage
grid
inverter
phase
transformer
Prior art date
Application number
KR1020140192335A
Other languages
Korean (ko)
Other versions
KR101773237B1 (en
Inventor
오승진
김태형
권병기
Original Assignee
주식회사 포스코아이씨티
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 주식회사 포스코아이씨티 filed Critical 주식회사 포스코아이씨티
Priority to KR1020140192335A priority Critical patent/KR101773237B1/en
Publication of KR20160082825A publication Critical patent/KR20160082825A/en
Application granted granted Critical
Publication of KR101773237B1 publication Critical patent/KR101773237B1/en

Links

Images

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H02J2003/365—Reducing harmonics or oscillations in HVDC
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

A system-based grid inverter system for minimizing an inrush current generated when a grid-connected inverter is connected to a grid, comprising: a first grid-connected inverter for controlling charging and discharging of a DC power source; A transformer for increasing the first output voltage of the first grid-connected inverter or reducing the grid voltage provided from the grid; A tie-breaker (TB) for connecting the transformer to the system; And a system controller for compensating for the phase delay of the grid voltage to synchronize the grid voltage and the first output voltage to couple the transformer to the grid through the grid-connected breaker.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication-based grid-based inverter system and a control method thereof,

The present invention relates to inverters, and more particularly to grid-connected inverters.

With the development of the industry, electric power demand is gradually increasing, and the gap between day and night, season, and day is widening.

In order to solve this problem, a method has been proposed in which surplus power of the system is stored in the battery or the under power of the system is supplied from the battery by linking the inverter with the system.

The configuration of an inverter connected to the system is disclosed in Korean Patent No. 10-130210, Korean Patent No. 10-1338921, etc. (hereinafter referred to as "prior arts").

In the case of the grid-connected inverter system presented in the preceding documents, an electric device such as a transformer is indispensably required to link the inverter to the system.

However, in the case of the conventional grid-connected inverter system, the transformer is instantaneously applied with a system voltage instantaneously connected to the system. As a result, as shown in FIG. 1, there is a problem that an inrush current of four times or more of the rated current is generated.

This inrush current can cause mechanical stress in the transformer, which can degrade the life of the transformer and cause an overcurrent relay (OCR) trip of the grid interrupter to link the transformer to the grid. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is a technical object of the present invention to provide a communication-based grid-connected inverter system and a control method thereof that can minimize an inrush current generated when a grid-

Another object of the present invention is to provide a communication-based grid-connected inverter system capable of transmitting sensed information of the grid voltage through a communication system and a control method thereof.

It is another object of the present invention to provide a communication-based grid-connected inverter system and a control method thereof that can compensate for an error caused by a communication delay occurring in the transmission of system voltage information.

Another object of the present invention is to provide a grid-connected inverter system and a control method thereof that can minimize the circulation current generated between a plurality of grid-connected inverters and a grid-connected inverter in grid-connected.

According to an aspect of the present invention, there is provided a system-based grid-inverter system comprising: a first grid-connected inverter for controlling charging / discharging of a DC power source; A transformer for increasing the first output voltage of the first grid-connected inverter or reducing the grid voltage provided from the grid; A tie-breaker (TB) for connecting the transformer to the system; And a system controller for compensating for the phase delay of the grid voltage to synchronize the grid voltage and the first output voltage to couple the transformer to the grid through the grid-connected breaker.

According to another aspect of the present invention, there is provided a method of controlling a grid-connected inverter system based on a communication, the method comprising: inputting a first inverter output breaker included in a first grid- ; Transmitting information on the grid voltage to the first grid link inverter through CAN communication if the grid voltage provided from the grid and the first output voltage of the first grid link inverter are not synchronized; Compensating a phase delay of the system voltage generated according to a delay time of the CAN communication; And adjusting the first output voltage so that the phase delay is synchronized with the compensated system voltage.

According to the present invention, since the transformer is connected to the system after the output voltage and the system voltage of the grid-connected inverter are synchronized, the system can be protected by minimizing the inrush current caused by the instantaneous application of the system voltage .

In addition, according to the present invention, there is an effect that a separate initial charging device for preventing an inrush current is not required, thereby reducing the manufacturing cost of the system.

In addition, according to the present invention, information on the system voltage can be transmitted through CAN communication, thereby simplifying the circuit configuration and facilitating system maintenance and maintenance.

In addition, there is an effect that a control error due to a communication delay can be eliminated by compensating an error due to a communication delay when transmitting grid voltage information as phase information at the time of coordinate conversion.

In addition, according to the present invention, since each of the grid voltage inverters is connected to the system controller through the CAN communication scheme, connection between the grid-connected inverters of different types is facilitated, thereby maximizing the scalability of the system.

In addition, according to the present invention, when a plurality of grid-connected inverters is connected to a grid, after the grid-connected grid of a specific grid-connected inverter is completed, the remaining grid-connected inverters are sequentially connected to the grid to minimize the circulation current generated between the grid- There is an effect that can be done.

1 is a graph showing the generation of an inrush current in the grid-connected inverter system according to the related art.
FIG. 2 is a schematic view illustrating a configuration of a communication-based grid-connected inverter system according to a first embodiment of the present invention.
FIG. 3 is a block diagram schematically showing the configuration of the inverter controller shown in FIG. 2. FIG.
4 is a graph showing the delay phase of the system voltage generated according to the delay time of the CAN communication.
5 is a graph showing coordinate axes for stop coordinate conversion.
6 is a graph showing a coordinate axis for rotating coordinate conversion.
7 is a graph showing a process in which the output voltage of the grid-connected inverter is synchronized with the grid voltage.
FIG. 8 is a block diagram schematically showing the configuration of the system controller shown in FIG. 2. FIG.
9 is a graph conceptually showing the synchronization between the output voltage of the grid-connected inverter and the grid voltage.
10 is a diagram schematically showing a configuration of a communication-based grid-connected inverter system according to a second embodiment of the present invention.
11 is a flowchart illustrating a method of controlling a grid-based inverter system based on communication according to the present invention.

The meaning of the terms described herein should be understood as follows.

The word " first, "" second," and the like, used to distinguish one element from another, are to be understood to include plural representations unless the context clearly dictates otherwise. The scope of the right should not be limited by these terms.

It should be understood that the terms "comprises" or "having" does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

It should be understood that the term "at least one" includes all possible combinations from one or more related items. For example, the meaning of "at least one of the first item, the second item and the third item" means not only the first item, the second item or the third item, but also the second item and the second item among the first item, Means any combination of items that can be presented from more than one.

Hereinafter, the same components will be denoted by the same reference numerals for convenience of description.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a schematic view illustrating a configuration of a communication-based grid-connected inverter system according to a first embodiment of the present invention. The grid-connected inverter system 200 shown in FIG. 2 includes a tie-breaker (TB) 210, a transformer 220, a grid-connected inverter 230, a DC power source 240, a system controller 250 ), And a sensing unit 260.

The grid interconnect breaker 210 couples the transformer 220 to the system 270 or isolates the transformer 220 from the system 270. That is, the grid interrupter 210 is turned on in response to an input command transmitted from the system controller 250 to connect the transformer 220 to the system 270, and is interrupted according to the shutdown command transmitted from the system controller 250 Isolating the transformer 220 from the system 270.

The transformer 220 reduces the grid voltage supplied from the grid 270 according to a predetermined voltage ratio and supplies the grid voltage to the grid inverter 230 when the grid grid interrupter 210 is turned on, And provides the output voltage to the system 270 according to the voltage ratio.

The primary side of the transformer 220 is connected to one end of the grid interrupter 210 and the secondary side of the transformer 220 is connected to one end of the grid interconnection inverter 230.

The grid-connected inverter 230 controls the charging and discharging of the DC power source 240 under the control of the system controller 250. In one embodiment, grid interconnect inverter 230 includes an inverter output breaker 232, a power conversion module 234, and an inverter controller 236, as shown in FIG.

An inverter output breaker (CB, 232) is connected to one end of the power conversion module 234 and to the secondary side of the transformer 120. The inverter output breaker 232 couples the power converter module 234 to the transformer 220 so that the grid inverter 230 is coupled to the system 270 or the power converter module 234 is disconnected from the transformer 220 Thereby disconnecting the grid interconnect inverter 230 from the system 270.

In other words, the inverter output breaker 232 is turned on in response to a closing command transmitted from the inverter controller 236 to connect the power conversion module 234 to the secondary side of the transformer 220, Command to disconnect the power conversion module 234 from the transformer 220.

The power conversion module 234 is connected to one end of the inverter output breaker 232 and one end of the DC power source 240. The power conversion module 234 converts the grid voltage to a DC voltage to charge the DC power source 240 and converts the DC voltage discharged from the DC power source 240 to an AC voltage, Voltage is generated. The output voltage generated by the power conversion module 234 is boosted by the transformer 220 and then supplied to the system 270.

The inverter controller 236 turns on the inverter output breaker 232 according to the input instruction of the inverter output breaker 232 transmitted from the system operator or the system controller 250 to connect the power conversion module 234 to the transformer 220 Or disconnects the power conversion module 234 from the transformer 220 by turning off the inverter output breaker 232 according to a command to cut off the inverter output breaker 232.

The configuration of the inverter controller 236 according to the present invention will be described in more detail with reference to FIG.

3 is a block diagram schematically illustrating the configuration of an inverter controller according to an embodiment of the present invention.

As shown in FIG. 3, the inverter controller 236 includes a first CAN communication unit 310, a delay compensation unit 320, and a voltage control unit 330.

The first CAN communication unit 310 receives system voltage information from the system controller 250 through CAN (Controller Area Network) communication.

The delay compensation unit 320 compensates for the phase delay of the system voltage received via the CAN communication. In the present case, the drive controller 236, the phase delay according to the information of the grid voltage on the delay (t delay) of the CAN communication as shown in, so to receive from the system controller 250, Fig. 4 through the CAN communication There is no other way. Accordingly, the delay compensator 320 compensates for the phase delay of the grid voltage generated due to the delay time of the CAN communication. 3, the delay compensation unit 320 includes a stationary coordinate transformation unit 322, an operation unit 324, and a rotation coordinate transformation unit 326. [

The stationary coordinate conversion unit 322 converts the three-phase system voltage received through the first CAN communication unit 310 into a two-phase alternating-current voltage through a stationary reference frame. That is, the stationary coordinate converter 322 converts the system voltages of three phases (V a , V b , and V c ) into two phases (V d s , V q s ).

Figure pat00001

The calculating unit 324 calculates the compensating phase angle? C by adding the delay phase angle? D matching the delay time t delay of the CAN communication with the phase angle? I of the system voltage.

The rotation coordinate conversion unit 326 converts the two-phase alternating voltage output from the stationary coordinate conversion unit 322 based on the compensation phase angle calculated by the calculation unit 324 into a two-phase direct-current voltage through rotational coordinate conversion. 6, the rotation coordinate transforming unit 326 rotates the coordinate axes of the two-phase (V d s , V q s ) AC voltage by the compensation phase angle? C at the same speed as the rotational angular velocity, (V d e , V q e ) into a direct current voltage.

Figure pat00002

The delay compensation unit 320 according to the present invention converts the system voltage, which is a three-phase alternating voltage, into the two-phase direct-current voltage through the stationary coordinate transforming unit 322 and the rotating coordinate transforming unit 324, Control of the output of the grid-connected inverter 230 by directly using the grid voltage of the grid-connected inverter 230 is complicated because the complex control variable is required.

3, the voltage control unit 330 turns on the inverter output breaker 232 before the system interrupter 210 is turned on by the system controller 250 to switch the power conversion module 234 to the transformer 220 ).

In addition, the voltage control unit 330 adjusts the output voltage so that the output voltage generated by the power conversion module 234 is synchronized with the system voltage for which the phase delay is compensated, for inputting the grid interrupter 210. That is, the voltage controller 330 adjusts the output voltage so that the output voltage is synchronized with the two-phase DC voltage output from the delay compensator 320.

In one embodiment, the voltage controller 330 increases the output voltage in the form of a ramp having a predetermined time constant such that the output voltage is synchronized with the system voltage, as shown in FIG.

According to this embodiment, the time constant of the output voltage is adjusted by a set time. Since the set time is proportional to the capacity and the winding current of the transformer 220 as shown in Equation (3) below, The time constant of the transformer 220 is also determined to be proportional to the capacity and the winding current of the transformer 220.

Figure pat00003

In Equation (3), Capacity represents the capacity of the transformer 220, and Ns represents the winding of the transformer 220.

Referring again to FIG. 2, the grid link inverter 230 may further include a filter 238. One end of the filter 238 is connected to the inverter output breaker 232 and the other end of the filter 238 is connected to the power conversion module 234 to filter the output voltage generated by the power conversion module 234, Lt; RTI ID = 0.0 > 234 < / RTI > In one embodiment, the filter 238 may be comprised of an LC filter.

The DC power source 240 discharges the DC power stored in the DC power source 240 to provide it to the grid link inverter 230 or charges the DC power provided from the grid link inverter 230.

In one embodiment, the DC power source 240 may be implemented as one or more batteries.

The system controller 250 determines whether or not the system voltage and the output voltage sensed by the sensing unit 260 are synchronized. When it is determined that the system voltage and the output voltage are synchronized, the system controller 250 turns on the grid interrupter 210, (220) to the system (270).

The configuration of the system controller 250 will be described in more detail with reference to FIG. FIG. 8 is a block diagram schematically illustrating the configuration of a system controller 250 according to an embodiment of the present invention.

8, the system controller 250 includes a synchronization determination unit 252, a control command generation unit 254, and a second CAN communication unit 256. As shown in FIG.

The synchronization determination unit 252 compares the system voltage sensed by the sensing unit 260 and the output voltage sensed by the sensing unit 260, and determines whether the system voltage and the output voltage are synchronized based on the comparison result.

In one embodiment, the synchronization determination unit 252 determines the magnitude, phase, and frequency of the system voltage sensed by the sensing unit 260 and the magnitude, phase, and frequency of the output voltage sensed by the sensing unit 260 It can be determined that the system voltage and the output voltage are synchronized with each other. An example of the case where the system voltage and the output voltage are synchronized is shown in a graph as shown in FIG.

In the above-described embodiment, the synchronization determination unit 252 compares the system voltage sensed by the sensing unit 260 with the output voltage to determine whether or not to synchronize. However, in a modified embodiment, the synchronization determination unit 252 may determine whether the system voltage and the output voltage are synchronized by comparing the output voltage with the secondary voltage of the transformer 220 calculated based on the system voltage.

To this end, the system controller 250 may further include a conversion unit 258 as shown in FIG.

The converting unit 258 calculates the secondary voltage of the transformer 220 using the system voltage sensed by the sensing unit 260. That is, the converting unit 258 converts the sensed system voltage to the primary voltage of the transformer 220 and reflects the voltage ratio of the transformer 220 to the system voltage, which is the primary voltage of the transformer 220, The secondary side voltage is calculated.

According to this embodiment, when the difference between the magnitude, phase, and frequency of the secondary voltage of the transformer 220 and the magnitude, phase, and frequency of the output voltage is within a predetermined error range, It is determined that the voltage and the output voltage are synchronized.

The control command generator 254 generates a command to turn on the grid interrupter 210 and provides it to the grid interrupter 210 if the synchronization determiner 252 determines that the grid voltage and the output voltage are synchronized. Accordingly, the transformer 220 is connected to the system 270 when the grid interrupter 210 is completely inserted.

If it is determined that the output voltage and the system voltage are not synchronized by the synchronization determination unit 252, the control command generation unit 254 generates a control command And transmits information on the voltage to the grid link inverter 230 through the second CAN communication unit 256.

When the system voltage information is input from the control command generator 254, the second CAN communication unit 256 transmits the inputted system voltage information to the grid link inverter 230 through the CAN communication.

As described above, since the system controller 250 and the grid-connected inverter 230 transmit and receive the grid voltage information through the CAN communication, the grid voltage information is received through the hard-wired wiring The circuit configuration is simplified, and maintenance and maintenance of the system become easy.

Referring again to FIG. 2, the sensing unit 260 senses the grid voltage and the output voltage. The sensing portion 260 may sense the system voltage by sensing the voltage at the first node N1 between the system 270 and the grid interconnect circuit breaker 210 and the filter 238 and The output voltage can be sensed by sensing the voltage at the second node N2 between the inverter output breaker 232. [

As described above, according to the present invention, when the inverter output interrupter 232 of the grid-connected inverter 230 is first turned on and the output voltage is gradually increased in the form of a ramp having a constant time constant and the output voltage is synchronized with the grid voltage, The inrush current of the transformer 220 can be minimized because the grid interrupter 210 is connected to the transformer 220 and the transformer 220 is connected to the system 270.

10 is a diagram schematically showing a configuration of a grid connection inverter system according to a second embodiment of the present invention. 10, the grid-connected inverter system 200 includes a grid-connected circuit breaker 210, a transformer 220, a plurality of grid-connected inverters 230a and 230b, a plurality of DC power sources 240a 240b, a system controller 250, and a sensing unit 260.

The grid-connected inverter system 200 shown in FIG. 10 is different from the grid-connected inverter system 200 shown in FIG. 2 in that a plurality of grid-connected inverters 230a and 230b and DC power sources 240a and 240b are implemented The internal configuration of each of the plurality of grid-connected inverters 230a and 230b is the same as that of the grid-connected inverter 230 shown in FIG. 2, but there are some differences in function. .

10, the grid-connected inverter system 200 includes only the first grid-link inverter 230a and the second grid-link inverter 230b, but this is merely an example, The system 200 may include three or more grid link inverters.

First, the transformer 220 is implemented as a multi-winding transformer 220, unlike the transformer 220 shown in FIG. 2, for linkage with a plurality of grid-connected inverters 230a and 230b.

2, the first grid-connected inverter 230a is connected to the transformer 220 before the grid-connected circuit breaker 210 is turned on, and the first grid-connected inverter 230a is connected to the transformer 220, When the first output voltage of the transformer 230a is synchronized with the system voltage, the grid interrupter 210 is turned on and the transformer 220 is connected to the system 270. [

At this time, since the first system link inverter 230a receives the information of the system voltage through the CAN communication from the system controller 250, the first system link inverter 230a compensates the phase delay of the system voltage generated according to the delay time of the CAN communication, And adjusts the first output voltage such that the first output voltage is synchronized to the system voltage whose phase delay is compensated.

Since only the first grid-link inverter 230a applies the voltage to the transformer 220, the set time proportional to the capacity and the capacity of the transformer 520, as described in the first embodiment, It should be longer than the specified value.

The second grid link inverter 230b is connected to the transformer 220 after the grid link circuit breaker 210 is turned on and the transformer 220 is connected to the system 270. [

More specifically, when the grid interrupter 210 is turned on and the transformer 220 is connected to the grid 270, the system controller 250 transmits the grid voltage information to the second grid link inverter The inverter controller 236b of the second grid link inverter 230b compensates the phase delay of the grid voltage received from the system controller 250 and then transmits the second delay of the second grid link inverter 230b Regulates the second output voltage of power conversion module 234b so that the output voltage is synchronized to the phase voltage delay compensated system voltage.

When it is determined that the second output voltage is synchronized with the system voltage, the second grid link inverter 230b turns on the inverter output breaker 232b of the grid link inverter 230b to connect the second grid link inverter 230b to the transformer 220).

In the system-based grid-inverter system 200 according to the second embodiment, the grid-connected inverters 230a and 230b are successively connected to the grid 270 so that each of the grid-connected inverters 230a and 230b is connected to the grid When the output voltage is synchronized with the system voltage through the voltage control of each of the grid interconnect inverters 230a and 230b and is simultaneously connected to the transformer 20 in a state where the grid interconnect inverters 230a and 230b Because of the difference in the output voltage caused by the sensing error, the delay, or the difference in the precision of the control of the control circuit.

Accordingly, the present invention can be applied to a system-connected inverter-based inverter system 200 according to the second embodiment in which the first grid-link inverter 230a and the second grid-link inverter 230b are not simultaneously turned on, The output voltage difference between the grid-connected inverters 230a and 230b can not be generated by connecting the second grid-linked inverter 230b to the system 270 after first connecting the grid-connected inverter 230a to the grid 270, 230a and 230b can be prevented from being generated.

In addition, when a plurality of grid-connected inverter systems such as those shown in FIG. 10 are connected in parallel to the grid, the above-described method can prevent an inrush current at the time of grid input, .

Therefore, applying this extended grid-connected inverter system to an energy storage system (ESS) to stabilize the output fluctuation by a renewable energy source such as wind power, solar power generation system, It is possible to stably connect the energy storage system to the system.

In addition, even in the case of adding a grid-connected inverter or connecting different types of grid-connected inverters, grid-connected grid-connected inverters can be connected only to maximize system scalability.

Hereinafter, a control method of the grid-connected inverter system according to the present invention will be described with reference to FIG.

11 is a flowchart showing a control method of the grid-connected inverter system according to an embodiment of the present invention.

The control method of the grid-connected inverter system shown in Fig. 11 can be applied to the grid-connected inverter system shown in Fig.

First, the first grid link inverter turns on the first inverter output breaker included in the first grid link inverter to connect the first grid link inverter to the transformer (S1100).

Then, the system controller determines whether the system voltage is synchronized with the first output voltage of the first grid-connected inverter (S1110). In one embodiment, it can be determined that the system voltage and the first output voltage are synchronized when the magnitude, phase, and frequency of the system voltage, and the difference in magnitude, phase, and frequency of the first output voltage are within an error range .

If it is determined that the system voltage is not synchronized with the first output voltage, the system controller transfers the system voltage information to the first system link inverter through the CAN communication (S1120).

Then, the first system link inverter compensates the phase delay of the system voltage generated according to the delay time of the CAN communication (S1130). In one embodiment, the first grid-connected inverter converts the grid voltage received in step S1120 into a two-phase alternating voltage through stationary coordinate transformation and adds the phase angle of the grid voltage to the delay phase Phase AC voltage can be converted into a system voltage of a two-phase DC voltage by rotational-coordinate conversion of the two-phase AC voltage based on the compensation phase angle.

Thereafter, the first grid-connected inverter performs voltage control of the first grid-connected inverter until the first output voltage is synchronized with the system voltage whose phase delay is compensated (S1140). In one embodiment, the first grid-coupled inverter may increase the first output voltage in the form of a ramp having a predetermined time constant until the first output voltage is synchronized to the grid voltage. At this time, the predetermined time constant is determined to be proportional to the capacity and the winding current of the transformer.

If it is determined in step S1110 that the system voltage and the first output voltage are synchronized, the system controller turns on the grid interrupter to connect the transformer to the system (S1150).

Although not shown in FIG. 11, the sensing unit may further include a step of sensing the system voltage and the first output voltage in order to determine whether or not to synchronize in step S1110.

In the above-described embodiment, the system voltage is compared with the first output voltage to determine whether to synchronize. However, in a modified embodiment, the system controller calculates the secondary voltage of the transformer based on the grid voltage and compares the secondary voltage of the transformer with the first output voltage to determine whether the grid voltage and the first output voltage are synchronized .

To this end, the system controller calculates the secondary voltage of the transformer by making the grid voltage the primary voltage of the transformer and reflecting the voltage ratio of the transformer to the grid voltage, which is the primary voltage of the transformer.

In accordance with such an embodiment, the system controller is configured such that when the magnitude, phase, and frequency of the secondary voltage of the transformer and the magnitude, phase, and frequency of the first output voltage are within a predetermined error range, It is determined that the voltage is synchronized.

Then, when the grid connection of the transformer is completed, the system controller transmits information on the grid voltage to the second grid link inverter connected in parallel to the first grid link inverter through the CAN communication (S1160).

Thereafter, the second system link inverter compensates for the phase delay of the system voltage generated according to the delay time of the CAN communication (S1170), and then determines whether or not the system voltage compensated for the second output voltage and the phase delay is synchronized (S1180). If it is determined that the second output voltage and the compensated system voltage have not been synchronized with each other, the second grid-link inverter outputs the second output voltage until the second output voltage is synchronized to the system voltage whose phase delay is compensated. Voltage control is performed (S1190). If it is determined in step S1180 that the second output voltage and the system voltage compensated for the phase delay are synchronized, the second system link inverter turns on the second inverter output circuit breaker to connect the second system link inverter to the transformer (S1200).

11, the control method of the grid-connected inverter system including a plurality of grid-connected inverters has been described. However, the grid-connected inverter system may be configured to include only one grid-connected inverter. In the case of the grid-connected inverter system including one grid-connected inverter, the grid-connected inverter can be linked to the grid through the process from S1100 to S1150 in FIG.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

200: grid connection inverter system 210: grid connection circuit breaker
220: Transformer 230: Grid-connected inverter
240: DC power source 250: System controller
260: sensing part

Claims (15)

A first grid-connected inverter for controlling charging and discharging of a DC power source;
A transformer for increasing the first output voltage of the first grid-connected inverter or reducing the grid voltage provided from the grid;
A tie-breaker (TB) for connecting the transformer to the system; And
And a system controller for compensating for the phase delay of the system voltage to synchronize the system voltage and the first output voltage to couple the transformer to the system via the system interrupter circuit breaker, . The method according to claim 1,
Wherein the first grid-
A delay compensation unit for compensating a phase delay of the system voltage received via the CAN communication; And
And a voltage controller for controlling the first output voltage so that the first output voltage is synchronized with the system voltage compensated for the phase delay. 3. The method of claim 2,
Wherein the delay compensation unit comprises:
A phase delay of the system voltage is compensated by using a compensating phase angle obtained by converting the system voltage into a 2-phase AC voltage and summing a phase angle of the system voltage with a delay phase angle matched with a delay time of the CAN communication Wherein the system-connected inverter-inverter system is a communication-based system-connected inverter system. 3. The method of claim 2,
Wherein the delay compensation unit comprises:
A stationary coordinate converter for converting the grid voltage into a 2-phase AC voltage through a stationary reference frame;
An operation unit for calculating a compensated phase angle by summing a phase angle of the system voltage and a delay phase angle matched with a delay time of the CAN communication; And
And a rotation coordinate conversion unit for converting the two-phase alternating voltage into a two-phase direct-current voltage by rotating reference frame based on the compensation phase angle,
Wherein the voltage control unit controls the first output voltage so that the first output voltage is synchronized with the two-phase DC voltage. 3. The method of claim 2,
The voltage control unit includes:
Increasing the first output voltage in the form of a ramp having a predetermined time constant such that the first output voltage is synchronized with the system voltage compensated for the phase delay,
Wherein the predetermined time constant is determined to be proportional to the capacity and the winding current of the transformer. 3. The method of claim 2,
A power conversion module converting the grid voltage into a DC voltage to charge the DC power source, converting a DC voltage discharged from the DC power source to an AC voltage to generate the first output voltage; And
Further comprising an inverter output breaker (CB) that couples the power conversion module to the transformer,
Wherein the voltage control unit switches the inverter output breaker to connect the power conversion module to the transformer before the grid interrupter is turned on. The method according to claim 1,
The system controller comprising:
And determines that the system voltage and the first output voltage are synchronized when the magnitude, phase, and frequency of the system voltage, and the difference between the magnitude, phase, and frequency of the first output voltage are within an error range. Communication - based Grid - Linked Inverter System. The method according to claim 1,
The system controller comprising:
Wherein the controller determines that the system voltage and the first output voltage are synchronized when the secondary voltage of the transformer is synchronized with the first output voltage by calculating the secondary voltage of the transformer using the system voltage, Communication - based Grid - Linked Inverter System. The method according to claim 1,
Further comprising at least one second grid-connected inverter connected in parallel to the first grid-linked inverter,
Wherein the first grid-connected inverter is connected to the transformer before the grid-interrupter is switched on, and the second grid-connected inverter is connected to the transformer after the grid-interrupter is switched on. Inverter system. 10. The method of claim 9,
The system controller comprising:
And the second grid-connected inverter synchronizes the second output voltage of the second grid-connected inverter with the grid voltage when the grid-interrupter is turned on and the transformer is connected to the grid, To the second grid-connected inverter through the second grid-
Wherein the second grid-
Compensates the phase delay of the system voltage generated according to the delay time of the CAN communication and controls the second output voltage so that the second output voltage is synchronized with the system voltage compensated for the phase delay, And the second grid-connected inverter is connected to the transformer when the voltage is synchronized to the grid voltage. Connecting the first grid inverter to the transformer by inputting a first inverter output breaker included in the first grid inverter inverter;
Transmitting information on the grid voltage to the first grid link inverter through CAN communication if the grid voltage provided from the grid and the first output voltage of the first grid link inverter are not synchronized;
Compensating a phase delay of the system voltage generated according to a delay time of the CAN communication; And
And adjusting the first output voltage so that the phase delay is synchronized with the compensated system voltage. 12. The method of claim 11,
Wherein the compensating comprises:
Converting the grid voltage into a two-phase alternating voltage through stationary coordinate transformation;
Calculating a compensated phase angle by summing a delay phase angle matched to a phase angle of the system voltage according to a delay time of the CAN communication; And
Converting the two-phase alternating voltage into a two-phase direct-current voltage by rotational-coordinate conversion based on the compensating phase angle,
Wherein the adjusting step adjusts the first output voltage to be synchronized with the two-phase DC voltage. 12. The method of claim 11,
In the adjusting step,
Increasing the first output voltage to a ramp shape having a predetermined time constant such that the first output voltage is synchronized to the system voltage with the phase delay compensated,
Wherein the predetermined time constant is determined to be proportional to the capacity and the winding current of the transformer. 12. The method of claim 11,
Transmitting information on the grid voltage to a second grid link inverter connected in parallel to the first grid link inverter via CAN communication when the transformer is associated with the grid;
Compensating a phase delay of the system voltage generated according to a delay time of the CAN communication; And
When the phase-delay compensated system voltage and the second output voltage of the second grid-link inverter are synchronized, a second inverter output circuit breaker included in the second system-grid inverter is input to the second grid- Further comprising the step of: controlling the power of the grid-connected inverter system. 15. The method of claim 14,
Wherein the second output voltage is a ramp waveform having a predetermined time constant such that the phase delay is synchronized to the compensated system voltage if the second output voltage is not synchronized to the system voltage compensated for the phase delay, The method further comprising the step of increasing the power of the grid-connected inverter system based on the power consumption of the grid.
KR1020140192335A 2014-12-29 2014-12-29 Inverter System Connected to Power Grid based on Communication and Method for Controlling The Same KR101773237B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
KR1020140192335A KR101773237B1 (en) 2014-12-29 2014-12-29 Inverter System Connected to Power Grid based on Communication and Method for Controlling The Same

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
KR1020140192335A KR101773237B1 (en) 2014-12-29 2014-12-29 Inverter System Connected to Power Grid based on Communication and Method for Controlling The Same

Publications (2)

Publication Number Publication Date
KR20160082825A true KR20160082825A (en) 2016-07-11
KR101773237B1 KR101773237B1 (en) 2017-08-31

Family

ID=56499464

Family Applications (1)

Application Number Title Priority Date Filing Date
KR1020140192335A KR101773237B1 (en) 2014-12-29 2014-12-29 Inverter System Connected to Power Grid based on Communication and Method for Controlling The Same

Country Status (1)

Country Link
KR (1) KR101773237B1 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109546874A (en) * 2018-11-21 2019-03-29 中国人民解放军陆军工程大学 The source of the isolated power system of tape pulse load carries decoupling model modelling approach
KR20200055299A (en) * 2018-11-13 2020-05-21 한양대학교 산학협력단 Method and system for controlling distributed energy resource
CN112838971A (en) * 2019-11-22 2021-05-25 恩智浦有限公司 CAN communication under cable breaking condition
KR20230110996A (en) 2022-01-17 2023-07-25 에스케이매직 주식회사 Structure with improved turbulent flow for flowmeter for dishwasher

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20190061310A (en) * 2017-11-27 2019-06-05 주식회사 윌링스 Power conversion system and compensating method for data thereof

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5540666B2 (en) * 2009-11-26 2014-07-02 富士電機株式会社 Self-sustained operation recovery method for interconnection inverter

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20200055299A (en) * 2018-11-13 2020-05-21 한양대학교 산학협력단 Method and system for controlling distributed energy resource
CN109546874A (en) * 2018-11-21 2019-03-29 中国人民解放军陆军工程大学 The source of the isolated power system of tape pulse load carries decoupling model modelling approach
CN112838971A (en) * 2019-11-22 2021-05-25 恩智浦有限公司 CAN communication under cable breaking condition
KR20230110996A (en) 2022-01-17 2023-07-25 에스케이매직 주식회사 Structure with improved turbulent flow for flowmeter for dishwasher

Also Published As

Publication number Publication date
KR101773237B1 (en) 2017-08-31

Similar Documents

Publication Publication Date Title
US10374429B2 (en) Islanding a plurality of grid tied power converters
AU2011204835B2 (en) Photovoltaic inverter system and method of starting same at high open-circuit voltage
US9831678B2 (en) Method for black starting a power station comprising a plurality of inverters connectable to an AC electrical grid
KR101773237B1 (en) Inverter System Connected to Power Grid based on Communication and Method for Controlling The Same
US11299051B2 (en) Electric charging system and method
US6404655B1 (en) Transformerless 3 phase power inverter
US8355265B2 (en) DC-to-DC power conversion
US9099938B2 (en) Bi-directional energy converter with multiple DC sources
US9041257B2 (en) System for distributing electric power to an electrical grid
KR101717825B1 (en) Inverter System Connected to Power Grid and Method for Controlling The Same
US11159011B2 (en) Electric circuits and power systems incorporating the same
CN110690731A (en) Power electronic transformer applicable to hybrid micro-grid and coordination control and mode switching method thereof
WO2011114422A1 (en) Power supply system, power supply method, program, recording medium, and power supply controller
MX2010012456A (en) Method and area electric power system detecting islanding by employing controlled reactive power injection by a number of inverters.
US10581247B1 (en) System and method for reactive power control of wind turbines in a wind farm supported with auxiliary reactive power compensation
JP6011739B1 (en) Control device and power conversion system
Harirchi et al. Designing smart inverter with unified controller and smooth transition between grid-connected and islanding modes for microgrid application
US9923375B2 (en) Method and a system for a fast bus transfer in an electrical power system
KR101196729B1 (en) Apparatus for actively controlling synchronization of microgrid and method thereof
US10027247B2 (en) Inverter, method for operating an inverter and energy supply installation with an inverter
Hamrouni et al. Control approach of a connected PV system under grid faults
JP2006101634A (en) Distributed power supply device
KR100689325B1 (en) H-bridge multi-level inverter
US11923789B2 (en) Power converter
RU2752693C1 (en) Method for remote synchronisation and restoration of normal mode of abnormally divided electrical network with generators

Legal Events

Date Code Title Description
A201 Request for examination
E902 Notification of reason for refusal
E90F Notification of reason for final refusal
E701 Decision to grant or registration of patent right
GRNT Written decision to grant