Power system and communication method thereof

Abstract

A power system according to one embodiment of the present invention includes: a first power conversion device; a second power conversion device; a first communication line connecting the first power conversion device and the second power conversion device; and a second communication line connecting the first power conversion device and the second power conversion device. The first power conversion device and the second power conversion device each measure a state value for a monitoring target and exchange the measured state values through the first communication line, and at least one of the first power conversion device or the second power conversion device is capable of performing, through the second communication line, communication for synchronizing the measurement timing of the state values.

Description

Power system and communication method thereof

[0001] This application claims the benefit of Korean Patent Application No. 10-2023-0101504 filed with the Korean Intellectual Property Office on August 3, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a power system and a communication method thereof, and more particularly, to a power system and a communication method thereof capable of minimizing measurement errors between power conversion devices.

[0003] An Energy Storage System (ESS) connects renewable energy sources, batteries that store electricity, and existing grid power. With the recent expansion of smart grids and renewable energy sources, and the emphasis on power system efficiency and safety, demand for energy storage systems is increasing to manage power supply and demand, as well as improve power quality. Depending on the intended use, energy storage systems can vary in output and capacity. Multiple battery systems can be interconnected to form large-capacity energy storage systems.

[0004] Among ESS systems, ESS systems linked to PV (Photovoltaic; solar power generation) systems are transitioning from AC-coupled to DC-coupled systems. In a DC-coupled ESS system, the PV and battery systems operate on DC voltage, while the grid operates on AC voltage. Therefore, a power conversion / conditioning system (PCS) including a DC / AC inverter is installed for each battery section, and a DC / DC converter is installed for the battery system. Here, the PCS controls the power supplied from the grid and the power supplied externally from the battery section, and the output of the DC / DC converter is connected to the PCS to control the DC voltage / current of the battery system.

[0005] When an inverter and converter are operated in conjunction, the inverter and converter independently measure status values ​​(e.g., DC link voltage and current values) for the monitored object and use these measured status values ​​for control and diagnosis. However, if the status values ​​measured by the inverter and converter differ in time, diagnostic accuracy may be reduced or power conversion gain may be compromised.

[0006] Accordingly, an appropriate communication technology is required to improve diagnostic accuracy and minimize power conversion gain loss by synchronizing measurement points between power conversion devices.

[0007] The purpose of the present invention to solve the above problems is to provide a power system capable of minimizing measurement errors between power conversion devices.

[0008] Another object of the present invention to solve the above problems is to provide a communication method for such a power system.

[0009] According to one embodiment of the present invention for achieving the above object, a power system may include: a first power conversion device; a second power conversion device; a first communication line connecting the first power conversion device and the second power conversion device; and a second communication line connecting the first power conversion device and the second power conversion device. Here, the first power conversion device and the second power conversion device each measure a status value for a monitoring target, and exchange the measured status values ​​through the first communication line, and at least one of the first power conversion device and the second power conversion device may perform communication through the second communication line to synchronize the measurement time points of the status values.

[0010] The second communication line may be configured as a separate line from the first communication line.

[0011] Either of the first power conversion device and the second power conversion device may be configured to transmit a first signal requesting initiation of measurement of a state value to the other one via the second communication line.

[0012] Either of the first power conversion device and the second power conversion device may be configured to be predefined as a transmission subject of the first signal.

[0013] The first power conversion device and the second power conversion device may be configured to transmit the first signal to the other when their preset measurement time points arrive.

[0014] One of the devices that transmitted the first signal can measure the state value immediately after transmitting the first signal, and the other device that received the first signal can measure the state value immediately after receiving the first signal. Here, the first power conversion device and the second power conversion device can share the measured state value with each other via the first communication line.

[0015] The first power conversion device and the second power conversion device may be preset so that the measurement cycle of the state value is the same period. Here, one of the first power conversion device and the second power conversion device may be configured to transmit a second signal indicating the arrival of the measurement cycle to the other through the second communication line.

[0016] Among the first power conversion device and the second power conversion device, one of the devices whose measurement cycle arrives first may be configured to transmit the second signal to the other device.

[0017] One of the devices that transmitted the second signal can measure the state value immediately after transmitting the second signal, and the other device that received the second signal can measure the state value immediately after receiving the second signal. Here, the first power conversion device and the second power conversion device can share the measured state value with each other via the first communication line.

[0018] One of the devices that transmitted the second signal can, immediately after transmitting the second signal, check whether the next measurement cycle has arrived through its own time measurement device. Here, the other device that received the second signal can, immediately after transmitting the second signal, initialize its own time measurement device and, using its initialized time measurement device, check whether the next measurement cycle has arrived.

[0019] When a specific signal for synchronizing the measurement time is transmitted and received through the second communication line, each of the first power conversion device and the second power conversion device can measure the state value, update a pre-stored counter value, and exchange the state value and the counter value through the first communication line.

[0020]

[0021] According to one embodiment of the present invention for achieving the above other object, a communication method is provided, which is a communication method of a power system including a first power conversion device and a second power conversion device that are interconnected through a first communication line and a second communication line, the method comprising: a step in which one of the first power conversion device and the second power conversion device transmits a specific signal for synchronizing a time point of measurement of a state value to the other through the second communication line; a step in which the first power conversion device and the second power conversion device each measure a state value for a monitoring target; and a step in which the first power conversion device and the second power conversion device exchange the measured state values ​​through the first communication line.

[0022] The step of transmitting the specific signal to the other may include the step of transmitting a first signal requesting initiation of measurement of a state value to the other through the second communication line.

[0023] The step of transmitting the specific signal to another may include a step of transmitting the first signal to the other, by one of the first power conversion device and the second power conversion device, which is predefined as a transmission subject of the first signal.

[0024] The step of transmitting the specific signal to the other may include a step of transmitting the first signal to the other, by one of the first power conversion device and the second power conversion device, when its preset measurement time point has arrived.

[0025] The step of measuring the status value for each of the monitoring targets may include a step of measuring the status value by one of the first signal transmitters immediately after transmitting the first signal; and a step of measuring the status value by another of the first signal receivers immediately after receiving the first signal.

[0026] The first power conversion device and the second power conversion device may be preset so that the measurement cycle of the state value is the same period. Here, the step of transmitting the specific signal to the other may include the step of transmitting a second signal indicating the arrival of the measurement cycle to the other through the second communication line.

[0027] The step of transmitting the specific signal to the other may include a step of transmitting the second signal to the other among the first power conversion device and the second power conversion device, whichever one of the measurement cycles arrives first.

[0028] The step of measuring the status value for each of the monitoring targets may include a step of measuring the status value by one of the ones that transmitted the second signal immediately after transmitting the second signal; and a step of measuring the status value by another one that received the second signal immediately after receiving the second signal.

[0029] The step of measuring the status value for each of the monitoring objects may further include a step of one of the devices transmitting the second signal checking, immediately after transmitting the second signal, whether the next measurement cycle has arrived through its own time measurement device; and a step of another device receiving the second signal initializing its own time measurement device and checking, immediately after transmitting the second signal, whether the next measurement cycle has arrived through its own initialized time measurement device.

[0030] The step of measuring each status value for the monitoring target may further include a step of updating each pre-stored counter value. Here, the step of exchanging the status values ​​may include a step of exchanging the status values ​​and the counter values ​​via the first communication line.

[0031] According to the above-described embodiment of the present invention, by synchronizing the measurement time points through a communication channel configured separately from the data communication channel and then performing data communication between the power conversion devices, the measurement error between the power conversion devices can be minimized.

[0032] Figure 1 is a block diagram showing the communication connection structure of a typical power system.

[0033] Figure 2 is a block diagram of a power system according to an embodiment of the present invention.

[0034] Figure 3 is an operation flowchart of a communication method of a power system according to the present invention.

[0035] Figure 4 is an operation flowchart of a communication method of a power system according to the first embodiment of the present invention.

[0036] Figure 5 is an operation flowchart of a communication method of a power system according to a second embodiment of the present invention.

[0037] Figure 6 is an operation flowchart of a communication method of a power system according to a third embodiment of the present invention.

[0038] Figure 7 is an operation flowchart of a communication method of a power system according to a fourth embodiment of the present invention.

[0039] 100: First power conversion device

[0040] 200: Second power conversion device

[0041] 300: Monitoring target

[0042] The present invention is susceptible to various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention. Throughout the description of each drawing, similar reference numerals have been used to designate similar components.

[0043] Terms such as "first," "second," "A," and "B" may be used to describe various components, but these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present invention, the first component could be referred to as the "second component," and similarly, the second component could also be referred to as the "first component." The term "and / or" includes any combination of multiple related items listed or any one of multiple related items listed.

[0044] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0045] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0046] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0047]

[0048] Figure 1 is a block diagram showing the communication connection structure of a typical power system.

[0049] Referring to FIG. 1, a power system may be configured to include an inverter (10) and a converter (20). Here, the inverter (10) may be a DC / AC inverter and the converter (20) may be a DC / DC converter.

[0050] The inverter (10) and the converter (20) can be connected to the link capacitor (30) via a status measurement line. Here, the inverter (10) and the converter (20) can collect status values ​​including voltage values ​​and current values ​​of the link capacitor (30) via the status measurement line.

[0051] The inverter (10) and the converter (20) can be connected via a communication line and configured to mutually transmit and receive data. Here, the inverter (10) and the converter (20) can exchange the status value of the link capacitor (30) via the communication line and share it with each other.

[0052] The inverter (10) and converter (20) can perform predefined control logic and diagnostic logic using shared state values. However, if there is an error in the measurement timing of the shared state values, diagnostic accuracy may be reduced or a loss in power conversion gain may occur. To prevent such problems, predefined compensation logic may be additionally applied. However, this imposes a burden on system operation due to the complex data processing process.

[0053] The present invention relates to a technology for solving such problems, a structure of a power system capable of minimizing measurement point errors between power conversion devices without applying complex compensation logic, and a communication method of such a power system.

[0054] Hereinafter, a preferred embodiment according to the present invention will be described in detail with reference to the attached drawings.

[0055]

[0056] Figure 2 is a block diagram of a power system according to an embodiment of the present invention.

[0057] Referring to FIG. 2, a power system according to an embodiment of the present invention may include a first power conversion device (100) and a second power conversion device (200).

[0058] The first power conversion device (100) and the second power conversion device (200) may correspond to converters or inverters. For example, the first power conversion device (100) may be a DC / AC inverter and the second power conversion device (200) may be a DC / DC converter.

[0059] The first power conversion device (100) and the second power conversion device (200) may include a control device and a communication module. Here, the communication module may be configured to transmit and receive data through a communication line, and the control device may be configured to perform a predefined control process or diagnostic process using the transmitted and received data.

[0060] The first power conversion device (100) and the second power conversion device (200) can be connected to a monitoring target (300) via a status measurement line. Here, the monitoring target (300) may correspond to a link capacitor, but the monitoring target in the present invention is not limited to a specific object.

[0061] The first power conversion device (100) and the second power conversion device (200) can each measure the status value of the monitoring target (300) through the status measurement line. For example, the first power conversion device (100) and the second power conversion device (200) can collect status values ​​including the voltage value and current value of the link capacitor through the status measurement line.

[0062] The power system may include a first communication line (L1) connecting a first power conversion device (100) and a second power conversion device (200).

[0063] Additionally, the power system may include a second communication line (L2) connecting the first power conversion device (100) and the second power conversion device (200). Here, the second communication line (L2) may be configured as a separate line from the first communication line (L1).

[0064] The first communication line (L1) may be configured to perform communication for data transmission and reception. For example, the first power conversion device (100) and the second power conversion device (200) may mutually transmit and receive status values ​​of the monitoring target (300) via the first communication line (L1).

[0065] The second communication line (L2) may be configured to perform communication for synchronizing the measurement time of the state value. Here, at least one of the first power conversion device (100) and the second power conversion device (200) may transmit a specific signal for synchronizing the measurement time of the state value through the second communication line (L2).

[0066] A synchronization signal for matching the measurement time of the state value may include at least one of a first signal requesting the start of measurement of the state value; and a second signal indicating the arrival of a preset measurement period.

[0067] When one of the first power conversion device (100) and the second power conversion device (200) transmits a synchronization signal to the other through the second communication line (L2), the first power conversion device (100) and the second power conversion device (200) can measure a status value for the monitoring target (300) immediately after transmission and reception of the synchronization signal, and exchange the status value through the first communication line (L1) to share it with each other.

[0068] According to the present invention, after synchronizing the measurement time points through a communication channel (L2) configured separately from a data communication channel (L1), the power conversion devices measure the state values ​​and exchange data, so that no measurement error occurs between the power conversion devices.

[0069]

[0070] Figure 3 is an operation flowchart of a communication method of a power system according to the present invention.

[0071] Either the first power conversion device or the second power conversion device may transmit a synchronization signal for synchronizing the measurement time of the state value via the second communication line (S310). Here, the synchronization signal may include at least one of a first signal requesting the start of measurement of the state value; and a second signal indicating the arrival of a preset measurement cycle.

[0072] The transmitter of the synchronization signal can be predefined.

[0073] For example, a first power conversion device may be preset as the transmission entity, or a second power conversion device may be preset as the transmission entity.

[0074] For another example, if a measurement point or measurement cycle is predefined for each of the first power conversion device and the second power conversion device, the device that has reached its measurement point or measurement cycle can be preset to transmit a synchronization signal to the other device.

[0075] After a synchronization signal is transmitted by the transmission subject, the first power conversion device and the second power conversion device can each measure a status value for the monitoring target (S320).

[0076] Specifically, when a power conversion device (transmitting entity) that has transmitted a synchronization signal transmits a synchronization signal to another power conversion device (receiving entity), the transmitting entity can measure a state value immediately after transmitting the synchronization signal, and the receiving entity can measure the state value immediately after receiving the synchronization signal. In other words, the first power conversion device and the second power conversion device can each measure the state value of the monitoring target immediately after transmitting and receiving the synchronization signal.

[0077] Thereafter, the first power conversion device and the second power conversion device can exchange the state values ​​measured in S320 with each other through the first communication line (S330).

[0078] The first power conversion device and the second power conversion device can perform a predefined control process or diagnostic process using a shared state value. Here, the shared state value is a value measured at the same time, so that a decrease in diagnostic accuracy or a loss of power conversion gain can be prevented.

[0079]

[0080] Figure 4 is an operation flowchart of a communication method of a power system according to the first embodiment of the present invention.

[0081] The communication method of the power system illustrated in FIG. 4 is an embodiment in which the transmission subject of the synchronization signal is set to the first power conversion device, and the synchronization signal is defined as the first signal which is a measurement start request signal.

[0082] The first power conversion device set as the transmission subject can transmit a first signal, which is a signal requesting the start of measurement of a status value, to the second power conversion device through the second communication line when its preset measurement time point or measurement cycle arrives (S410).

[0083] The first power conversion device can measure the status value of the monitoring target immediately after transmitting the first signal (S421), and the second power conversion device can measure the status value of the monitoring target immediately after receiving the first signal (S422).

[0084] The first power conversion device and the second power conversion device can exchange individually measured status values ​​with each other through the first communication line (S430).

[0085] Afterwards, the first power conversion device can check whether its own measurement point or measurement cycle has arrived.

[0086]

[0087] When the corresponding measurement point or measurement cycle arrives, the first power conversion device can transmit the first signal to the second power conversion device through the second communication line (S440).

[0088] The first power conversion device can measure the status value of the monitoring target immediately after transmitting the first signal (S451), and the second power conversion device can measure the status value of the monitoring target immediately after receiving the first signal (S452).

[0089] The first power conversion device and the second power conversion device can exchange individually measured status values ​​with each other through the first communication line (S460).

[0090] The first power conversion device and the second power conversion device can communicate with each other by repeatedly performing S410 to S430 until the power system is switched to a stop mode.

[0091]

[0092] Figure 5 is an operation flowchart of a communication method of a power system according to a second embodiment of the present invention.

[0093] The communication method of the power system illustrated in Fig. 5 is an embodiment in which a step of sharing a counter value is added to the communication method of Fig. 4.

[0094] The first power conversion device set as a transmission subject can transmit a first signal, which is a signal requesting the start of measurement of a status value, to the second power conversion device through the second communication line when its preset measurement time point or measurement cycle arrives (S510).

[0095] The first power conversion device can measure the status value of the monitoring target immediately after transmitting the first signal (S521), and the second power conversion device can measure the status value of the monitoring target immediately after receiving the first signal (S522).

[0096] In addition, the first power conversion device can update the pre-stored counter value immediately after transmitting the first signal (S523), and the second power conversion device can update the pre-stored counter value immediately after receiving the first signal (S524). Here, the counter value is stored in the storage devices of each of the first power conversion device and the second power conversion device, and can have the same value.

[0097] For example, when a first signal is transmitted and received, the first power conversion device can update (n+1) the counter value (n) stored in its storage device by increasing it by 1, and the second power conversion device can also update (n+1) the counter value (n) stored in its storage device by increasing it by 1.

[0098] The first power conversion device and the second power conversion device can exchange individually measured status values ​​and counter values ​​with each other through the first communication line (S530).

[0099] Afterwards, the first power conversion device can check whether its own measurement point or measurement cycle has arrived.

[0100] When the corresponding measurement point or measurement cycle arrives, the first power conversion device can transmit the first signal to the second power conversion device through the second communication line (S540).

[0101] The first power conversion device can measure the status value of the monitoring target immediately after transmitting the first signal (S551) and update its own counter value (S553), and the second power conversion device can measure the status value of the monitoring target immediately after receiving the first signal (S552) and update its own counter value (S554).

[0102] The first power conversion device and the second power conversion device can exchange individually measured status values ​​and counter values ​​with each other through the first communication line (S560).

[0103] The first power conversion device and the second power conversion device can communicate with each other by repeatedly performing S510 to S530 until the power system is switched to a stop mode.

[0104] According to the present embodiment, the first power conversion device and the second power conversion device share a counter value managed with the same value as the state value measured at the same point in time, thereby preventing the measurement order of the shared state value from being misaligned or pushed back.

[0105]

[0106] Figure 6 is an operation flowchart of a communication method of a power system according to a third embodiment of the present invention.

[0107] The communication method of the power system illustrated in FIG. 6 is an embodiment in which the state value measurement cycles of the first and second power conversion devices are preset to the same period, the transmission subject of the synchronization signal is preset to the device whose measurement cycle arrives first, and the synchronization signal is defined as a second signal that is a signal notifying the arrival of the measurement cycle.

[0108] The first power conversion device and the second power conversion device can each check whether the measurement cycle has arrived through their own time measuring devices (e.g., timers).

[0109] If the measurement cycle of the first power conversion device arrives first (S610), the first power conversion device can transmit a second signal, which is a signal notifying the arrival of the measurement cycle, to the second power conversion device through the second communication line (S620).

[0110] The first power conversion device can measure the status value of the monitoring target immediately after transmitting the second signal (S631), and the second power conversion device can measure the status value of the monitoring target immediately after receiving the second signal (S632).

[0111] Here, the second power conversion device that received the second signal can initialize its own time measurement device (S633) so as to synchronize with the time measurement device of the first power conversion device. Thereafter, the first power conversion device and the second power conversion device can each check whether the next measurement cycle has arrived through their own time measurement devices.

[0112] The first power conversion device and the second power conversion device can exchange individually measured status values ​​with each other through the first communication line (S640).

[0113] Thereafter, if the measurement cycle of the second power conversion device arrives first (S650), the second power conversion device can transmit a second signal, which is a signal notifying the arrival of the measurement cycle, to the first power conversion device through the second communication line (S660).

[0114] The second power conversion device can measure the status value of the monitoring target immediately after transmitting the second signal (S672), and the first power conversion device can measure the status value of the monitoring target immediately after receiving the second signal (S671).

[0115] Here, the first power conversion device that has received the second signal can initialize its own time measurement device (S673) so as to synchronize with the time measurement device of the second power conversion device. Thereafter, the first power conversion device and the second power conversion device can each check whether the next measurement cycle has arrived through their own time measurement devices.

[0116] The first power conversion device and the second power conversion device can exchange individually measured status values ​​with each other through the first communication line (S680).

[0117] The first power conversion device and the second power conversion device can communicate with each other by repeatedly performing S610 to S640 until the power system is switched to a stop mode.

[0118] According to this embodiment, even when power conversion devices are set to the same measurement cycle, it is possible to prevent minute measurement point errors that may occur due to time measurement devices.

[0119]

[0120] Figure 7 is an operation flowchart of a communication method of a power system according to a fourth embodiment of the present invention.

[0121] The communication method of the power system illustrated in Fig. 7 is an embodiment in which a step of sharing a counter value is added to the communication method of Fig. 6.

[0122] The first power conversion device and the second power conversion device can each check whether the measurement cycle has arrived through their own time measuring devices (e.g., timers).

[0123] If the measurement cycle of the first power conversion device arrives first (S710), the first power conversion device can transmit a second signal, which is a signal notifying the arrival of the measurement cycle, to the second power conversion device through the second communication line (S720).

[0124] The first power conversion device can measure the status value of the monitoring target immediately after transmitting the second signal (S731), and the second power conversion device can measure the status value of the monitoring target immediately after receiving the second signal (S732).

[0125] Additionally, the first power conversion device can update the pre-stored counter value immediately after transmitting the second signal (S733), and the second power conversion device can update the pre-stored counter value immediately after receiving the second signal (S734).

[0126] Here, the second power conversion device that received the second signal can initialize its own time measurement device (S735) so as to synchronize with the time measurement device of the first power conversion device. Thereafter, the first power conversion device and the second power conversion device can each check whether the next measurement cycle has arrived through their own time measurement devices.

[0127] The first power conversion device and the second power conversion device can exchange individually measured status values ​​and counter values ​​with each other through the first communication line (S740).

[0128] Thereafter, if the measurement cycle of the second power conversion device arrives first (S750), the second power conversion device can transmit a second signal to the first power conversion device through the second communication line (S760).

[0129] The second power conversion device can measure the status value of the monitoring target immediately after transmitting the second signal (S772) and update its own counter value (S774), and the first power conversion device can measure the status value of the monitoring target immediately after receiving the second signal (S771) and update its own counter value (S773).

[0130] Here, the first power conversion device that received the second signal can initialize its own time measurement device (S775).

[0131] The first power conversion device and the second power conversion device can exchange individually measured status values ​​and counter values ​​with each other through the first communication line (S780).

[0132] The first power conversion device and the second power conversion device can communicate with each other by repeatedly performing S710 to S740 until the power system is switched to a stop mode.

[0133]

[0134] The operations of the method according to an embodiment of the present invention can be implemented as a computer-readable program or code on a computer-readable recording medium. A computer-readable recording medium includes any type of recording device that stores data readable by a computer system. Furthermore, a computer-readable recording medium can be distributed across network-connected computer systems, allowing the computer-readable program or code to be stored and executed in a distributed manner.

[0135] While some aspects of the present invention have been described in the context of a device, they may also represent a description of a corresponding method, wherein a block or device corresponds to a method step or a feature of a method step. Similarly, aspects described in the context of a method may also be described as a corresponding block or item or a feature of a corresponding device. Some or all of the method steps may be performed by (or using) a hardware device, such as, for example, a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, one or more of the most significant method steps may be performed by such a device.

[0136] Although the present invention has been described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims

1. First power conversion device; Second power conversion device; A first communication line connecting the first power conversion device and the second power conversion device; and A second communication line connecting the first power conversion device and the second power conversion device is included, The first power conversion device and the second power conversion device, Measure the status values ​​for each monitoring target, and exchange the measured status values ​​through the first communication line, At least one of the first power conversion device and the second power conversion device, A power system that performs communication to synchronize the measurement time of the state value through the second communication line.

2. In claim 1, The above second communication line, A power system comprising a line separate from the first communication line.

3. In claim 1, Either one of the first power conversion device and the second power conversion device, A power system configured to transmit a first signal requesting the initiation of measurement of a state value to another one through the second communication line.

4. In claim 3, A power system, wherein either the first power conversion device or the second power conversion device is configured to be predefined as a transmission subject of the first signal.

5. In claim 3, The first power conversion device and the second power conversion device, A power system configured to transmit said first signal to another when its preset measurement point arrives.

6. In claim 3, One of the first signals transmitted measures the state value immediately after transmitting the first signal, The other one, which has received the first signal, measures the state value immediately after receiving the first signal, The first power conversion device and the second power conversion device, A power system in which measured state values ​​are shared with each other through the first communication line.

7. In claim 1, The first power conversion device and the second power conversion device, The measurement cycle of the status value is preset to the same period, Either one of the first power conversion device and the second power conversion device, A power system configured to transmit a second signal indicating the arrival of the measurement cycle to another one through the second communication line.

8. In claim 7, A power system, wherein among the first power conversion device and the second power conversion device, one of which the measurement cycle arrives first is configured to transmit the second signal to the other.

9. In claim 8, One of the above-mentioned second signals measures the state value immediately after transmitting the second signal, The other one, which has received the second signal, measures the state value immediately after receiving the second signal, The first power conversion device and the second power conversion device, A power system in which measured state values ​​are shared with each other through the first communication line.

10. In claim 8, One of the second signals, which transmitted the second signal, checks whether the next measurement cycle has arrived through its own time measuring device immediately after transmitting the second signal, Another power system that receives the second signal, immediately after transmitting the second signal, initializes its own time measuring device and checks whether the next measurement cycle has arrived through its initialized time measuring device.

11. In claim 1, When a specific signal for synchronizing the measurement time is transmitted and received through the second communication line, Each of the first power conversion device and the second power conversion device, A power system that measures the state value, updates a stored counter value, and exchanges the state value and the counter value through the first communication line.

12. A communication method of a power system, comprising a first power conversion device and a second power conversion device interconnected through a first communication line and a second communication line, A step of transmitting a specific signal for synchronizing the measurement time of the state value to the other one of the first power conversion device and the second power conversion device through the second communication line; A step in which the first power conversion device and the second power conversion device each measure a status value for a monitoring target; and A communication method of a power system, comprising a step of exchanging the measured state value between the first power conversion device and the second power conversion device through the first communication line.

13. In claim 12, The step of transmitting the above specific signal to another one is, A communication method of a power system, comprising the step of transmitting a first signal requesting the initiation of measurement of a state value to another through the second communication line.

14. In claim 13, The step of transmitting the above specific signal to another one is, A communication method of a power system, comprising a step of transmitting the first signal to the other one, wherein one of the first power conversion device and the second power conversion device is predefined as a transmission subject of the first signal.

15. In claim 13, The step of transmitting the above specific signal to another one is, A communication method of a power system, comprising a step of transmitting the first signal to the other one, when one of the first power conversion device and the second power conversion device reaches its preset measurement point in time.

16. In claim 13, The step of measuring each status value for the above monitoring target is: A step of measuring the state value immediately after transmitting the first signal by any one of the first signals; and A communication method of a power system, comprising a step of measuring the state value immediately after receiving the first signal by another one of the first signals.

17. In claim 12, The first power conversion device and the second power conversion device, The measurement cycle of the status value is preset to the same period, The step of transmitting the above specific signal to another one is, A communication method of a power system, comprising the step of transmitting a second signal indicating the arrival of the measurement period to another one through the second communication line.

18. In claim 17, The step of transmitting the above specific signal to another one is, A communication method of a power system, comprising a step of transmitting the second signal to the other one, among the first power conversion device and the second power conversion device, whichever one of the measurement cycles arrives first.

19. In claim 18, The step of measuring each status value for the above monitoring target is: A step of measuring the state value immediately after transmitting the second signal by any one of the above-mentioned second signals; and A communication method of a power system, comprising the step of measuring the state value immediately after receiving the second signal by another one of the second signals.

20. In claim 18, The step of measuring each status value for the above monitoring target is: A step of checking whether the next measurement cycle has arrived through its own time measuring device immediately after transmitting the second signal; and A communication method of a power system, further comprising the step of: immediately after receiving the second signal, the other one initializes its own time measuring device, and checks whether the next measurement cycle has arrived through its initialized time measuring device.

21. In claim 12, The step of measuring each status value for the above monitoring target is: Further comprising a step of updating each of the previously stored counter values, The step of exchanging the above status values ​​is: A communication method of a power system, comprising a step of exchanging the state value and the counter value through the first communication line.

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