Power systems and their communication methods

Abstract

A power system according to one embodiment of the present invention 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 state value for a monitoring object and exchange the measured state values ​​via the first communication line, and one or more of the first power conversion device and the second power conversion device can communicate via the second communication line to synchronize the measurement time of the state value.

Description

[[Technical Field]]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2023-0101504 filed with the Korean Intellectual Property Office on August 3, 2023, and the entire contents disclosed in the document of said Korean patent application are incorporated herein.

[0002] The present invention relates to a power system and a communication method therefor, and more specifically, to a power system and a communication method therefor capable of minimizing measurement errors between power converters. [[Background Art]]

[0003] An Energy Storage System (ESS) is a system that interconnects renewable energy, batteries storing electric power, and existing grid power. In recent years, smart grids and renewable energy have been widely popularized. With the increasing emphasis on the efficiency and safety of power systems, demand for energy storage systems is gradually increasing for adjusting power supply and demand and improving power quality. Depending on the purpose of use, the output and capacity of an energy storage system can vary. A plurality of battery systems can be connected to each other to constitute a large-capacity energy storage system.

[0004] Among ESS systems, those connected to PV (Photovoltaic; solar power generation) systems are changing from AC-coupled to DC-coupled systems. In a DC-coupled ESS system, the PV system and battery system are configured with DC voltage, while the grid is configured with AC voltage. Therefore, each battery section is equipped with a Power Conversion / Conditioning System (PCS) including a DC / AC inverter, and the battery system is equipped with a DC / DC converter. Here, the PCS controls the power supplied from the grid and the power supplied from the battery section to the outside, 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 a converter are operated in conjunction, they independently measure state values ​​for the monitored object (e.g., DC link voltage and current values) and use the measured state values ​​for control and diagnosis. However, if the state values ​​measured by the inverter and the converter are measured at different times, the diagnostic accuracy may decrease or power conversion gain may be lost.

[0006] Therefore, appropriate communication technology is needed that can synchronize the measurement timing between power conversion devices, improve diagnostic accuracy, and minimize the loss of power conversion gain. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The objective of the present invention, which aims to solve the above-mentioned problems, is to provide a power system that can minimize measurement errors between power conversion devices.

[0008] Another objective of the present invention, in order to solve the problems described above, is to provide a communication method for such power systems. [Means for solving the problem]

[0009] A power system according to one embodiment of the present invention for achieving the above objectives may include a first power converter; a second power converter; a first communication line connecting the first power converter and the second power converter; and a second communication line connecting the first power converter and the second power converter. Here, the first power converter and the second power converter each measure a state value for a monitoring target, exchange the measured state values ​​via the first communication line, and one or more of the first power converter and the second power converter can communicate via the second communication line to synchronize the measurement timing of the state values.

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

[0011] One of the first power converter and the second power converter may be configured to transmit a first signal to the other via the second communication line requesting the start of measurement of a state value.

[0012] Either the first power converter or the second power converter can be predefined and configured as the transmitting entity of the first signal.

[0013] The first power converter and the second power converter can be configured to transmit the first signal to the other when their respective pre-set measurement times arrive.

[0014] The device that transmitted the first signal can measure the status value immediately after transmitting the first signal, and the device that received the first signal can measure the status value immediately after receiving the first signal. Here, the first power converter and the second power converter can share the measured status value with each other via the first communication line.

[0015] The first power converter and the second power converter can be pre-set to have the same measurement period for state values. Here, one of the first power converter and the second power converter may be configured to transmit a second signal indicating the arrival of the measurement period to the other via the second communication line.

[0016] Of the first power converter and the second power converter, the one whose measurement cycle arrives first can be configured to transmit the second signal to the other.

[0017] The device that transmitted the second signal can measure the status value immediately after transmitting the second signal, and the device that received the second signal can measure the status value immediately after receiving the second signal. Here, the first power converter and the second power converter can share the measured status value with each other via the first communication line.

[0018] The party that transmitted the second signal can check immediately after transmitting the second signal whether the next measurement cycle has arrived through its own time measuring device. The party that received the second signal can initialize its own time measuring device immediately after transmitting the second signal and check whether the next measurement cycle has arrived through its initialized time measuring device.

[0019] When a specific signal for synchronizing the measurement time is transmitted or received via the second communication line described above, the first power converter and the second power converter can each measure the status value, update a pre-stored counter value, and exchange the status value and the counter value via the first communication line.

[0020] A communication method according to one embodiment of the present invention for achieving the above-mentioned other objective is a communication method for a power system including a first power converter and a second power converter interconnected via a first communication line and a second communication line, the method including: one of the first power converter and the second power converter transmits a specific signal to the other via the second communication line to synchronize the timing of measurement of a state value; the first power converter and the second power converter each measure a state value for a monitoring target; and the first power converter and the second power converter exchange the measured state values ​​via the first communication line.

[0021] The step of transmitting the above-mentioned specific signal to the other party may include the step of transmitting a first signal to the other party via the second communication line requesting the start of measurement of a state value.

[0022] The step of transmitting the above-mentioned specific signal to the other party may include the step of the first power converter and the second power converter, which are predefined as the transmitting entity of the first signal, transmitting the first signal to the other party.

[0023] The step of transmitting the above-mentioned specific signal to the other party may include the step of the first power converter and the second power converter, when their predetermined measurement time has arrived, transmitting the first signal to the other party.

[0024] The steps of measuring the status values ​​for each of the monitoring targets may include: one of the parties that transmitted the first signal measures the status value immediately after transmitting the first signal; and the other party that received the first signal measures the status value immediately after receiving the first signal.

[0025] The first power conversion device and the second power conversion device can be preset with the same measurement period for state values. Here, the step of transmitting the specific signal to the other party may include a step of transmitting a second signal indicating the arrival of the measurement period to the other party via the second communication line.

[0026] The step of transmitting the specific signal to the other party may include a step in which, of the first power conversion device and the second power conversion device, the one whose measurement period arrives first transmits the second signal to the other party.

[0027] The step of respectively measuring the state values for the monitoring object may include: a step of measuring the state value immediately after the one that transmitted the second signal transmits the second signal; and a step of measuring the state value immediately after the other party that received the second signal receives the second signal.

[0028] The step of respectively measuring the state values for the monitoring object may further include: a step of, immediately after the one that transmitted the second signal transmits the second signal, checking whether the next measurement period has arrived via its own time measurement device; and a step of, immediately after the other party that received the second signal receives the second signal, initializing its own time measurement device and checking whether the next measurement period has arrived via the initialized own time measurement device.

[0029] The step of respectively measuring the state values for the monitoring object may further include a step of respectively updating pre-stored counter values. Here, the step of exchanging the state values may include a step of exchanging the state values and the counter values via the first communication line. Effects of the Invention

[0030] According to the embodiments of the present invention described above, by synchronizing the measurement timing through a communication channel configured separately from the data communication channel, and then performing data communication between power converters, measurement errors between power converters can be minimized. [Brief explanation of the drawing]

[0031] [Figure 1] This is a block diagram showing the communication connection structure of a typical power system. [Figure 2] This is a block diagram of a power system according to an embodiment of the present invention. [Figure 3] This is an operational flowchart of the communication method for a power system according to the present invention. [Figure 4] This is an operation flowchart of the communication method for a power system according to the first embodiment of the present invention. [Figure 5] This is an operation flowchart of a communication method for a power system according to a second embodiment of the present invention. [Figure 6] This is an operation flowchart of a communication method for a power system according to a third embodiment of the present invention. [Figure 7] This is an operation flowchart of the communication method for a power system according to a fourth embodiment of the present invention. [Modes for carrying out the invention]

[0032] The present invention can be modified in various ways and has many embodiments; therefore, specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this should be understood not as limiting the present invention to specific embodiments, but rather as including all modifications, equivalents, or substitutes that fall within the spirit and technical scope of the present invention. Similar reference numerals are used for similar components in the description of each drawing.

[0033] Terms such as First, Second, A, B, etc., may be used to describe various components, but the components should not be limited by such terms. The terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the First component may be named the Second component, and similarly, the Second component may be named the First component. The terms "and / or" include combinations of multiple related items or one of multiple related items.

[0034] When it is stated that one component is "combined" or "connected" to another component, it should be understood that this may mean that it is directly combined or connected to the other component, but that another component may exist in between. Conversely, when it is stated that one component is "directly combined" or "directly connected" to another component, it should be understood that there is no other component in between.

[0035] The terms used in this application are used solely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless they are clearly different in context. In this application, terms such as “includes” or “having” are intended to specify the presence of features, figures, steps, actions, components, parts, or combinations thereof as described in the specification, and should not be understood to preemptively exclude the presence or possibility of adding one or more other features, figures, steps, actions, components, parts, or combinations thereof.

[0036] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as those generally understood by a person of ordinary skill in the art to which this invention pertains. Terms as defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meaning in the context of the relevant art, and not as ideal or overly formal unless explicitly defined herein.

[0037] Figure 1 is a block diagram showing the communication connection structure of a typical power system.

[0038] Referring to Figure 1, the power system can 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.

[0039] The inverter 10 and converter 20 can be connected to the link capacitor 30 via a state measurement line. Here, the inverter 10 and converter 20 can collect state values, including the voltage and current values ​​of the link capacitor 30, via the state measurement line.

[0040] The inverter 10 and the converter 20 can be connected via a communication line and configured to send and receive data to each other. Here, the inverter 10 and the converter 20 can exchange and share the state value of the link capacitor 30 via the communication line.

[0041] The inverter 10 and converter 20 can execute predefined control and diagnostic logic using shared state values. However, if there is an error in the measurement timing of the shared state values, the diagnostic accuracy may decrease or a loss may occur in the power conversion gain. To prevent such problems, predefined compensation logic can be added, but in this case, the complex data processing process will burden the system operation.

[0042] The present invention relates to a technology for solving such problems, and to a power system structure and a communication method for such a power system that can minimize measurement time errors between power converters without applying complex compensation logic.

[0043] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0044] Figure 2 is a block diagram of a power system according to an embodiment of the present invention.

[0045] Referring to Figure 2, the power system according to an embodiment of the present invention may include a first power converter 100 and a second power converter 200.

[0046] The first power converter 100 and the second power converter 200 may be converters or inverters. For example, the first power converter 100 may be a DC / AC inverter, and the second power converter 200 may be a DC / DC converter.

[0047] The first power converter 100 and the second power converter 200 may include a control device and a communication module. Here, the communication module may be configured to send and receive data via a communication line, and the control device may be configured to execute a predefined control process or diagnostic process using the sent and received data.

[0048] The first power converter 100 and the second power converter 200 can be connected to the monitoring target 300 via a state measurement line. Here, the monitoring target 300 may be a link capacitor, but in the present invention, the monitoring target is not limited to a specific individual.

[0049] The first power converter 100 and the second power converter 200 can each measure the state values ​​of the monitored device 300 via a state measurement line. For example, the first power converter 100 and the second power converter 200 can collect state values ​​including the voltage and current values ​​of the link capacitor via the state measurement line.

[0050] The power system may include a first communication line L1 connecting a first power converter 100 and a second power converter 200.

[0051] Furthermore, the power system may include a second communication line L2 connecting the first power converter 100 and the second power converter 200. Here, the second communication line L2 can be configured as a separate line from the first communication line L1.

[0052] The first communication line L1 can be configured to perform communication for data transmission and reception. For example, the first power converter 100 and the second power converter 200 can mutually transmit and receive status values ​​of the monitored device 300 via the first communication line L1.

[0053] The second communication line L2 can be configured to communicate for synchronizing the timing of state value measurements. Here, one or more of the first power converter 100 and the second power converter 200 can transmit a specific signal via the second communication line L2 to synchronize the timing of state value measurements.

[0054] A synchronization signal for matching the measurement times of state values ​​may include one or more of the following: a first signal requesting the start of state value measurement; and a second signal indicating the arrival of a preset measurement cycle.

[0055] When one of the first power converter 100 and the second power converter 200 transmits a synchronization signal to the other via the second communication line L2, the first power converter 100 and the second power converter 200 can measure a status value for the monitored device 300 immediately after the transmission and reception of the synchronization signal, and exchange and share the status value with each other via the first communication line L1.

[0056] According to the present invention, after synchronizing the measurement timing via a communication channel L2 configured separately from the data communication channel L1, the power converter measures the status value and exchanges data, thereby preventing measurement errors between power converters.

[0057] Figure 3 is an operation flowchart of the communication method for a power system according to the present invention.

[0058] One of the first and second power converters may transmit a synchronization signal via a second communication line to synchronize the measurement time of the state value (S310). Here, the synchronization signal may include one or more 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.

[0059] The entity transmitting the synchronization signal can be defined in advance.

[0060] For example, the first power converter may be pre-configured as the transmitting entity, or the second power converter may be pre-configured as the transmitting entity.

[0061] Another example is that, if the first power converter and the second power converter each have predefined measurement times or measurement cycles, the device whose measurement time or measurement cycle has arrived may transmit a synchronization signal to the other device.

[0062] After the transmitting entity transmits a synchronization signal, the first power converter and the second power converter can measure the status values ​​for the monitoring target, respectively (S320).

[0063] Specifically, when a power converter that has transmitted a synchronization signal (transmitter) transmits the same synchronization signal to another power converter (receiver), the transmitter can measure the status value immediately after transmitting the synchronization signal, and the receiver can measure the status value immediately after receiving the synchronization signal. In other words, the first power converter and the second power converter can each measure the status value of the monitored object immediately after transmitting and receiving the synchronization signal.

[0064] Subsequently, the first power converter and the second power converter can exchange the state values ​​measured in S320 with each other via the first communication line (S330).

[0065] The first and second power converters can perform a predefined control or diagnostic process using shared state values. Here, the shared state values ​​are values ​​measured at the same time, which prevents a decrease in diagnostic accuracy or a loss of power conversion gain.

[0066] Figure 4 is an operation flowchart of a communication method for a power system according to the first embodiment of the present invention.

[0067] The communication method for the power system shown in Figure 4 is an embodiment in which the primary transmitter of the synchronization signal is set to the first power converter, and the synchronization signal is defined as a first signal which is a measurement start request signal.

[0068] The first power converter, which is set as the transmitting entity, can transmit a first signal, which is a signal requesting the start of measurement of the status value, to the second power converter via the second communication line when its preset measurement time or measurement cycle arrives (S410).

[0069] The first power converter can measure the status value of the monitored object immediately after transmitting the first signal (S421), and the second power converter can measure the status value of the monitored object immediately after receiving the first signal (S422).

[0070] The first power converter and the second power converter can exchange state values ​​that they have individually measured with each other via the first communication line (S430).

[0071] Subsequently, the first power converter can check whether its measurement time or measurement cycle has arrived.

[0072] When the relevant measurement time or measurement cycle arrives, the first power converter can transmit the first signal to the second power converter via the second communication line (S440).

[0073] The first power converter can measure a status value for the monitoring target immediately after transmitting the first signal (S451), and the second power converter can measure a status value for the monitoring target immediately after receiving the first signal (S452).

[0074] The first power converter and the second power converter can exchange status values ​​that they have individually measured with each other via the first communication line (S460).

[0075] The first power converter and the second power converter can communicate with each other by repeatedly performing steps S410 to S430 until the power system is switched to shutdown mode.

[0076] Figure 5 is an operation flowchart of a communication method for a power system according to a second embodiment of the present invention.

[0077] The communication method for the power system shown in Figure 5 is an embodiment in which a step of sharing counter values ​​is added to the communication method in Figure 4.

[0078] The first power converter, which is set as the transmitting entity, can transmit a first signal, which is a signal requesting the start of measurement of the status value, to the second power converter via the second communication line when its preset measurement time or measurement cycle arrives (S510).

[0079] The first power converter can measure the status value of the monitored object immediately after transmitting the first signal (S521), and the second power converter can measure the status value of the monitored object immediately after receiving the first signal (S522).

[0080] Furthermore, the first power converter can update a pre-stored counter value immediately after transmitting the first signal (S523), and the second power converter can update a pre-stored counter value immediately after receiving the first signal (S524). Here, the counter values ​​are stored in the respective memory devices of the first and second power converters and can have the same value.

[0081] For example, when a first signal is transmitted or received, the first power converter can update its counter value (n) stored in its memory by increasing it by 1 (n+1), and the second power converter can also update its counter value (n) stored in its memory by increasing it by 1 (n+1).

[0082] The first power converter and the second power converter can exchange individually measured state values ​​and counter values ​​via the first communication line (S530).

[0083] Subsequently, the first power converter can check whether its measurement time or measurement cycle has arrived.

[0084] When the relevant measurement time or measurement cycle arrives, the first power converter can transmit the first signal to the second power converter via the second communication line (S540).

[0085] The first power converter can measure the status value of the monitored object (S551) and update its own counter value (S553) immediately after transmitting the first signal, and the second power converter can measure the status value of the monitored object (S552) and update its own counter value (S554) immediately after receiving the first signal.

[0086] The first power converter and the second power converter can exchange individually measured state values ​​and counter values ​​via the first communication line (S560).

[0087] The first power converter and the second power converter can communicate with each other by repeatedly performing steps S510 to S530 until the power system is switched to shutdown mode.

[0088] According to this embodiment, the first power converter and the second power converter share a counter value that is managed to be the same as the state value measured at the same time, thereby preventing the measurement order of the shared state value from shifting or being extended.

[0089] Figure 6 is an operation flowchart of a communication method for a power system according to a third embodiment of the present invention.

[0090] The communication method for the power system shown in Figure 6 is an embodiment in which the state value measurement cycles of the first and second power converters are set to be the same period, the entity transmitting the synchronization signal is set to be the device whose measurement cycle arrives first, and the synchronization signal is defined as a second signal which is a measurement cycle arrival notification signal.

[0091] The first power converter and the second power converter can each check whether or not the measurement cycle has arrived through their own time measuring devices (e.g., timers).

[0092] If the measurement cycle of the first power converter arrives first (S610), the first power converter can transmit a second signal, which is a measurement cycle arrival notification signal, to the second power converter via the second communication line (S620).

[0093] The first power converter can measure the status value of the monitored object immediately after transmitting the second signal (S631), and the second power converter can measure the status value of the monitored object immediately after receiving the second signal (S632).

[0094] Here, the second power converter, having received the second signal, can initialize its own time measuring device (S633) to synchronize it with the time measuring device of the first power converter. Subsequently, the first and second power converters can each check through their own time measuring devices whether or not the next measurement cycle has arrived.

[0095] The first power converter and the second power converter can exchange state values ​​that they have individually measured with each other via the first communication line (S640).

[0096] Subsequently, if the measurement cycle of the second power converter arrives first (S650), the second power converter can transmit a second signal, which is a measurement cycle arrival notification signal, to the first power converter via the second communication line (S660).

[0097] The second power converter can measure the status value of the monitored object immediately after transmitting the second signal (S672), and the first power converter can measure the status value of the monitored object immediately after receiving the second signal (S671).

[0098] Here, the first power converter, upon receiving the second signal, can initialize its own time measuring device (S673) to synchronize it with the time measuring device of the second power converter. Subsequently, the first and second power converters can each check through their own time measuring devices whether or not the next measurement cycle has arrived.

[0099] The first power converter and the second power converter can exchange state values ​​that they have individually measured with each other via the first communication line (S680).

[0100] The first power converter and the second power converter can communicate with each other by repeatedly performing steps S610 to S640 until the power system is switched to shutdown mode.

[0101] According to this embodiment, even when power converters are set to the same measurement cycle, minute measurement timing errors that may occur due to the time measuring device can be prevented.

[0102] Figure 7 is an operation flowchart of a communication method for a power system according to a fourth embodiment of the present invention.

[0103] The communication method for the power system shown in Figure 7 is an embodiment in which a step of sharing counter values ​​is added to the communication method in Figure 6.

[0104] The first power converter and the second power converter can each check whether or not the measurement cycle has arrived through their own time measuring devices (e.g., timers).

[0105] If the measurement cycle of the first power converter arrives first (S710), the first power converter can transmit a second signal, which is a measurement cycle arrival notification signal, to the second power converter via the second communication line (S720).

[0106] The first power converter can measure the status value of the monitored object immediately after transmitting the second signal (S731), and the second power converter can measure the status value of the monitored object immediately after receiving the second signal (S732).

[0107] Furthermore, the first power converter can update a pre-stored counter value immediately after transmitting the second signal (S733), and the second power converter can update a pre-stored counter value immediately after receiving the second signal (S734).

[0108] Here, the second power converter, having received the second signal, can initialize its own time measuring device (S735) to synchronize it with the time measuring device of the first power converter. Subsequently, the first and second power converters can each check through their own time measuring devices whether or not the next measurement cycle has arrived.

[0109] The first power converter and the second power converter can exchange status values ​​and counter values ​​that they have individually measured via the first communication line (S740).

[0110] Subsequently, if the measurement cycle of the second power converter arrives first (S750), the second power converter can transmit a second signal to the first power converter via the second communication line (S760).

[0111] The second power converter can measure the status value of the monitored object (S772) and update its own counter value (S774) immediately after transmitting the second signal, and the first power converter can measure the status value of the monitored object (S771) and update its own counter value (S773) immediately after receiving the second signal.

[0112] Here, the first power converter, having received the second signal, can initialize its own time measuring device (S775).

[0113] The first power converter and the second power converter can exchange status values ​​and counter values ​​that they have individually measured via the first communication line (S780).

[0114] The first power converter and the second power converter can communicate with each other by repeatedly performing steps S710 to S740 until the power system is switched to shutdown mode.

[0115] The operation of the method according to an embodiment of the present invention can be embodied as a computer-readable program or code on a computer-readable recording medium. A computer-readable recording medium includes all types of recording devices that store data that can be read by a computer system. Furthermore, computer-readable recording media can be distributed across networked computer systems, allowing computer-readable programs or code to be stored and executed in a distributed manner.

[0116] Some aspects of the present invention have been described in the context of apparatus, but they can also be described by corresponding methods, where a block or apparatus corresponds to a method step or a feature of a method step. Similarly, aspects described in the context of a method can be described by corresponding blocks or items or features of corresponding apparatus. Some or all of the method steps can be carried out by (or using) hardware devices such as, for example, a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, one or more of the most important method steps can be carried out by such devices.

[0117] While preferred embodiments of the present invention have been described above with reference to the present invention, those skilled in the art will understand that the present invention can be modified and altered in various ways without departing from the spirit and scope of the invention as set forth in the following claims. [Explanation of Symbols]

[0118] 100: First power converter 200: Second power converter 300: Monitoring target

Claims

1. First power converter; Second power converter; A first communication line connecting the first power converter and the second power converter; and Includes a second communication line connecting the first power converter and the second power converter, The first power converter and the second power converter are, The status values ​​for each monitoring target are measured, and the measured status values ​​are exchanged via the first communication line. One or more of the first power converter and the second power converter are: A power system that communicates via the second communication line to synchronize the measurement timing of the state value.

2. The second communication line is, The power system according to claim 1, configured as a line separate from the first communication line.

3. One of the first power converter and the second power converter is, The power system according to claim 1, configured to transmit a first signal requesting the start of measurement of a state value to the other via the second communication line.

4. The power system according to claim 3, wherein one of the first power converter and the second power converter is configured to be a transmitting entity of the first signal in advance.

5. The first power converter and the second power converter are The power system according to claim 3, configured to transmit the first signal to the other when a pre-set measurement time for itself arrives.

6. The party that transmitted the first signal measures the state value immediately after transmitting the first signal. The other device that received the first signal measures the state value immediately after receiving the first signal. The first power converter and the second power converter are The power system according to claim 3, wherein measured state values ​​are shared with each other via the first communication line.

7. The first power converter and the second power converter are The measurement period for the state value is set in advance as the same period. One of the first power converter and the second power converter is, The power system according to claim 1, configured to transmit a second signal indicating the arrival of the measurement cycle to the other via the second communication line.

8. The power system according to claim 7, wherein the first power converter and the second power converter are configured such that the one whose measurement cycle arrives first transmits the second signal to the other.

9. The party that transmitted the second signal measures the status value immediately after transmitting the second signal. The other device that received the second signal measures the state value immediately after receiving the second signal. The first power converter and the second power converter are The power system according to claim 8, wherein measured state values ​​are shared with each other via the first communication line.

10. The party that transmitted the second signal checks, immediately after transmitting the second signal, through its own time measuring device, whether or not the next measurement cycle has arrived. The power system according to claim 8, wherein the other party that receives the second signal initializes its own time measuring device immediately after transmitting the second signal, and checks through its initialized time measuring device whether or not the next measurement cycle has arrived.

11. When a specific signal for synchronizing the measurement time is transmitted or received via the second communication line, Each of the first power converter and the second power converter is: The power system according to claim 1, comprising measuring the state value, updating a pre-stored counter value, and exchanging the state value and the counter value via the first communication line.

12. A communication method for a power system including a first power converter and a second power converter interconnected via a first communication line and a second communication line, One of the first power converter and the second power converter transmits a specific signal to the other via the second communication line for synchronizing the timing of measurement of state values; The first power converter and the second power converter each measure a state value for the object being monitored; and A communication method for a power system, comprising the step of the first power converter and the second power converter exchanging the measured state values ​​via the first communication line.

13. The step of transmitting the aforementioned specific signal to the other party is: A communication method for a power system according to claim 12, comprising the step of transmitting a first signal requesting the start of measurement of a state value to the other party via the second communication line.

14. The step of transmitting the aforementioned specific signal to the other party is: A communication method for a power system according to claim 13, comprising the step of one of the first power converter and the second power converter, which is predefined as the transmitting entity of the first signal, transmitting the first signal to the other.

15. The step of transmitting the aforementioned specific signal to the other party is: A communication method for a power system according to claim 13, comprising the step of one of the first power converter and the second power converter transmitting the first signal to the other when its predetermined measurement time has arrived.

16. The step of measuring the status values ​​for each of the monitoring targets is: A step in which the party that transmitted the first signal measures the state value immediately after transmitting the first signal; and A communication method for a power system according to claim 13, comprising the step of the other party that receives the first signal measuring the state value immediately after receiving the first signal.

17. The first power converter and the second power converter are The measurement period for the state value is set in advance as the same period. The step of transmitting the aforementioned specific signal to the other party is: A communication method for a power system according to claim 12, comprising the step of transmitting a second signal indicating the arrival of the measurement cycle to the other party via the second communication line.

18. The step of transmitting the aforementioned specific signal to the other party is: A communication method for a power system according to claim 17, comprising the step of the first power converter and the second power converter, whichever has the earlier measurement cycle, transmitting the second signal to the other.

19. The step of measuring the status values ​​for each of the monitoring targets is: The step of one party that transmitted the second signal measuring the state value immediately after transmitting the second signal; and A communication method for a power system according to claim 18, comprising the step of the other party that receives the second signal measuring the state value immediately after receiving the second signal.

20. The step of measuring the status values ​​for each of the monitoring targets is: The step of one party that transmitted the second signal checking, immediately after transmitting the second signal, whether the next measurement cycle has arrived through its own time measuring device; and The communication method for a power system according to claim 18, further comprising the step of the other party, which has received the second signal, initializing its own time measuring device immediately after transmitting the second signal, and checking through its initialized time measuring device whether or not the next measurement cycle has arrived.

21. The step of measuring the status values ​​for each of the monitoring targets is: The process further includes the step of updating each of the pre-stored counter values, The step of exchanging the aforementioned state values ​​is: A communication method for a power system according to claim 12, comprising the step of exchanging the state value and the counter value via the first communication line.

Images