KR20240044074A - Digital grid power router and control method thereof - Google Patents

Abstract

The present invention relates to a digital grid power relay device, and includes a processor that determines a control mode of the digital grid power relay (DGPR) in consideration of the status of distributed power and load linked to the distribution system, wherein the processor , check the normal operation status of the distribution system, check whether the voltage and frequency of the distribution system are operating within the normal range, check whether the total power generation from new and renewable sources exceeds the total consumption, and check whether the total power generation from new and renewable sources exceeds the total consumption. When the total consumption exceeds the total consumption, if an energy storage device exists in the distribution system, the energy storage device is operated in maximum charging mode, and the excess power from renewable sources is calculated by comparing the sum of the load and charge amount with the renewable source power generation. By setting and comparing the excess power with the adjacent system, the control mode of the digital grid power relay (DGPR) is determined as one of the first to fourth control modes.

Description

Digital grid power relay device and its control method {DIGITAL GRID POWER ROUTER AND CONTROL METHOD THEREOF}

The present invention relates to a digital grid power relay device and a control method thereof. More specifically, the present invention relates to a digital grid power relay device (DGPR: Digital Grid Power Router) control mode considering the situation of distributed power and loads linked to the distribution system. It relates to a digital grid power relay device and its control method that allows determining .

In general, renewable energy power is concentrated in the distribution system, and in particular, with the implementation of the distributed power generation (DER) access guarantee system of 1 MW or less in 2016, the demand for access to distributed power in the distribution system is rapidly increasing.

In Korea, the proportion of self-consumption distributed power generation (DER) facilities is low and the number of power sales-type facilities is high, resulting in a large amount of power flowing into the distribution network. Accordingly, the plan to build 332 new distribution lines to connect renewable energy has been approved, and as of December 2019, construction of 118 lines has been completed. However, the burden of reinforcing the distribution network for connection to distributed power is still high, and the wait for connection to distributed power is long. There is a situation.

Meanwhile, as distributed power generation is connected to the power system and the amount of power generation increases, the thermal limitations and impedance components of the distribution line limit the distributed power connection capacity of the distribution line.

At this time, the maximum installed capacity of distributed power that can stably operate the power system is called the DER Hosting Capacity. The DER Hosting Capacity is calculated based on a specific situation. It is not something that can be determined, but various indicators such as voltage maintenance range, voltage fluctuation, frequency fluctuation, line overload, power quality, and protection coordination issues must be considered in various situations.

Meanwhile, the distribution system connection of new and renewable distributed power sources is largely divided into the firm interconnection method (see (a) in Figure 1) and the flexible interconnection method (see (b) in Figure 1).

Here, the confirmed connection method is a method that allows connection based on the rated capacity of distributed power for each distribution line. It is highly reliable because connection problems do not occur even at the maximum power generation of distributed power regardless of the operating conditions of the distribution system. Excluding peak output periods, there is an inefficiency problem in which there is a lot of capacity left over in distribution lines. Conversely, the flexible connection method is a method of connecting distributed power by signing a contract under the condition that the output of the distributed power can be temporarily limited in case of grid congestion due to peak output of the distributed power.

Meanwhile, the standards for connecting the distributed power to the distribution system were designed according to the line capacity, but even if the connection standard capacity is satisfied, overvoltage problems may occur depending on the configuration of the distribution system (e.g., length of distribution line, installation location of distributed power, etc.). there is.

In addition, in the event of a line failure, if the distribution line section where distributed power is installed due to line transfer is connected to a nearby line, the distributed power capacity may be exceeded, so a device that monitors and actively manages the distribution system is needed.

The background technology of the present invention is disclosed in Republic of Korea Patent Publication No. 10-2022-0034387 (published on March 18, 2022, digital grid power relay device and operating method).

The above background technology is an invention filed by the same inventor of the present invention, and is a power relay device that configures a digital grid in the form of a sub-grid and is linked to the end of the distribution line for power integration between multi-terminal distribution lines in a distribution system with mixed distributed power sources. A digital grid power relay device and its operation method that perform power integration and current control through two-way power conversion are disclosed, but a method for determining the digital grid power relay (DGPR) control mode is not disclosed. .

According to one aspect of the present invention, the present invention was created to solve the above problems, and determines the digital grid power relay (DGPR) control mode in consideration of the situation of distributed power and load linked to the distribution system. The purpose is to provide a digital grid power relay device and its control method that enables

The digital grid power relay device according to one aspect of the present invention includes a processor that determines a control mode of the digital grid power relay (DGPR) in consideration of the status of the distributed power and load linked to the distribution system. The processor checks the normal operation status of the distribution system, checks whether the voltage and frequency of the distribution system are operating within the normal range, checks whether the total power generation from renewable sources exceeds the total consumption, and also checks whether the total renewable source power generation exceeds the total consumption. When the power generation exceeds the total consumption, and if an energy storage device exists in the distribution system, the energy storage device is operated in maximum charging mode, and the sum of the load and charging amount is compared with the renewable source power generation to exceed the renewable source. It is characterized by setting the power, comparing the excess power with the adjacent system, and determining the control mode of the digital grid power relay (DGPR) as one of the first to fourth control modes.

In the present invention, the processor checks the normal operation status of the distribution system, collects power generation and load data when the renewable source operates at maximum power generation, and checks whether the voltage and frequency of the distribution system are operated within the normal range. Therefore, if the voltage and frequency of the distribution system are not within the normal range and a temporary problem occurs in the system due to a failure of some equipment, the fault is immediately cleared, and for long-term failures, the digital grid power relay device is switched to the fourth control mode (CVCF). It is characterized by operating as an emergency power generation operation.

In the present invention, if the voltage and frequency of the distribution system are operating within a normal range, the processor checks whether the total power generation from renewable sources exceeds the total consumption, and ensures that the total power generation from renewable sources does not exceed the total consumption. When operating within a normal range, the digital grid power relay (DGPR) is characterized in that it operates in a third control mode (ACCP) to accommodate surplus power of the adjacent system.

In the present invention, if the voltage and frequency of the distribution system are operating within a normal range and the total power generation from renewable sources exceeds the total consumption, the processor checks whether an energy storage device exists in the distribution system, Operate the energy storage device in maximum charging mode, compare the sum of the load and charge amount with the renewable source power generation, set the renewable source excess power if the renewable source power generation is greater, and compare the excess power with the adjacent system. Therefore, when the excess power is smaller than that of the adjacent system, the digital grid power relay (DGPR) is operated in the second control mode (DCCP).

In the present invention, the processor compares the excess power with an adjacent system and, when the excess power is larger than the adjacent system, operates the digital grid power relay (DGPR) in the first control mode (DCCV). It is characterized by

In the present invention, the first control mode (DCCV) is a mode for controlling the voltage of the digital grid, the second control mode (DCCP) is a mode for supplying system power to the digital grid, and the third The control mode (ACCP) is a mode for supplying DC link power to the grid, and the fourth control mode (CVCF) is a mode for controlling the voltage and frequency of the grid.

The control method of the digital grid power relay device according to another aspect of the present invention includes a processor that determines the control mode of the digital grid power relay (DGPR) in consideration of the status of distributed power and load linked to the distribution system. In the control method of the digital grid power relay device, the processor checks the normal operation state of the distribution system, checks whether the voltage and frequency of the distribution system are operated within the normal range, and determines whether the total power generation from renewable sources is Check whether the consumption exceeds the total consumption, and when the total power generation from new and renewable sources exceeds the total consumption, and if an energy storage device exists in the distribution system, the energy storage device is operated in maximum charging mode, and the sum of the load and the charging amount is calculated. By comparing the generation amount of new and renewable sources, the excess power of new and renewable sources is set, and the excess power is compared with the adjacent system, and the control mode of the digital grid power relay (DGPR) is set to one of the first to fourth control modes. It is characterized by determining .

In the present invention, in order to determine one of the first to fourth control modes, the processor checks the normal operation state of the distribution system, collects power generation and load data when the renewable source operates at maximum power generation, and , check whether the voltage and frequency of the distribution system are operating within the normal range, and if the voltage and frequency of the distribution system are not within the normal range, or if a temporary problem occurs in the system due to a breakdown of some equipment, immediately eliminate the fault; For long-term failures, the digital grid power relay device operates in the fourth control mode (CVCF) and performs emergency power generation operation.

In the present invention, in order to determine one of the first to fourth control modes, the processor determines that if the voltage and frequency of the distribution system are operated within a normal range, the total power generation from renewable sources is equal to the total consumption. If the total power generation from renewable sources does not exceed the total consumption and is operating within the normal range, the digital grid power relay (DGPR) is set to a third control mode to accommodate the surplus power of the adjacent system. It is characterized by operating as (ACCP).

In the present invention, in order to determine one of the first to fourth control modes, the processor determines that the voltage and frequency of the distribution system are operating within a normal range and that the total power generation from renewable sources is equal to the total consumption. If it exceeds, check whether an energy storage device exists in the distribution system, operate the energy storage device in maximum charging mode, and compare the sum of the load and charge amount with the renewable source power generation to determine if the renewable source power generation is greater. If it is large, set the excess power of the renewable source, compare the excess power with the adjacent system, and if the excess power is smaller than the adjacent system, operate the digital grid power relay (DGPR) in the second control mode (DCCP). It is characterized by:

In the present invention, in order to determine one of the first to fourth control modes, the processor compares the excess power with an adjacent system and, when the excess power is larger than the adjacent system, the digital It is characterized in that the grid power relay (DGPR) operates in the first control mode (DCCV).

In the present invention, the first control mode (DCCV) is a mode for controlling the voltage of the digital grid, the second control mode (DCCP) is a mode for supplying system power to the digital grid, and the third The control mode (ACCP) is a mode for supplying DC link power to the grid, and the fourth control mode (CVCF) is a mode for controlling the voltage and frequency of the grid.

According to one aspect of the present invention, the present invention allows the digital grid power relay (DGPR) control mode to be determined by considering the status of distributed power sources and loads connected to the distribution system.

Figure 1 is an example graph showing the characteristics of a general distributed power source for comparing the characteristics of a definite connection method and a flexible connection method.
Figure 2 is an exemplary diagram showing the configuration of a digital grid power relay system according to an embodiment of the present invention.
Figure 3 is a flowchart for explaining a control method of a digital grid power relay device according to an embodiment of the present invention.
FIG. 4 is an example diagram showing the actual measurement result waveform in the first control mode (DCCV) for controlling the voltage of the digital grid in FIG. 3.
Figure 5 is an example diagram showing the actual measurement result waveform in the second control mode (DCCP) for supplying system power to the digital grid in Figure 3.
FIG. 6 is an example diagram showing the actual measurement result waveform in the third control mode (ACCP) for supplying DC link power to the system in FIG. 3.
Figure 7 is an example diagram showing the actual measurement result waveform in the fourth control mode (CVCF) for controlling the voltage and frequency of the system in Figure 3.

Hereinafter, an embodiment of a digital grid power relay device and a control method thereof according to the present invention will be described with reference to the attached drawings.

In this process, the thickness of lines or sizes of components shown in the drawing may be exaggerated for clarity and convenience of explanation. In addition, the terms described below are terms defined in consideration of functions in the present invention, and may vary depending on the intention or custom of the user or operator. Therefore, definitions of these terms should be made based on the content throughout this specification.

The present invention, which will be described below with reference to FIGS. 2 to 7, determines the digital grid power relay (DGPR) control mode in consideration of the situation of distributed power and load connected to the distribution system, and determines the control mode of the distribution system and the voltage of the distribution system. A digital grid power relay device that checks whether the frequency is operating within the normal range, checks whether the distributed power generation amount exceeds the limit range, and also compares the excess power with the adjacent system when the distributed power generation amount exceeds the limit range. It is about determining the control mode of (DGPR).

As described above, a microgrid composed of distributed power sources is a small-scale power supply network and has the function of being connected to the power system or separated from the system and operating independently.

Recently, with the expansion of new and renewable distributed power sources and various energy prosumer policies, various operation methods are expected to become possible in microgrids, and it will be possible to have more than one grid connection point, and in particular, direct power to other nearby microgrids without going through the distribution system. can also be flexible. At this time, when connecting the microgrids using general distribution lines, etc., voltage and frequency are shared between the microgrids, so a frequency and voltage control technique that can jointly respond to various disturbances occurring in the power system is needed.

In addition, the traditional distribution system generally consists of a radial system for system protection cooperation that quickly detects line failures and operates protection devices. In the radial system, a unidirectional current generally flows from the main transformer to the end of the distribution line, When a fault occurs, the fault section is separated from the system, so a power outage occurs in the downstream system below the fault point. Accordingly, in order to minimize power outages in the event of a breakdown, the distribution system is divided into several sections and connected to nearby distribution lines (3 divisions, 3 connections). At this time, the connection point with the neighboring line is normally open (NOP: Normally Open Point) and is connected through a switch operation only when a failure occurs.

Recently, active Soft Open Point (SOP) technology, which installs power converters at these always-open points to diversify the necessary power between distribution lines and prevent the propagation of failures, has been attracting attention.

In order to implement the active SOP (Soft Open Point), a back-to-back (BTB) type inverter is used, such as the Digital Grid Power Router (DGPR) developed by the Korea Electric Power Research Institute, and a flexible energy/transmission system is used between distribution systems. Reactive power can be controlled to a desired value or the connected bus voltage and current at both ends can be controlled.

In addition, the digital grid power relay (DGPR) is especially designed to control the voltage and current of the distribution system by connecting to the end of the distribution line where a large number of new and renewable distributed power sources are connected to improve the acceptance rate of distributed power in the distribution system and compensate for terminal voltage. It can be used as In addition, the active SOP (Soft Open Point) can connect distribution lines connected not only to the same substation but also to different substations, and also enables flexibility of power between different distribution voltages. In addition, two or more distribution lines can be connected in the form of a multi-terminal, and it has the feature of being expandable in various ways, such as installing an energy storage device in the DC terminal or linking with the DC distribution system.

When installing the digital grid power relay (DGPR), which has various features as described above, on multiple distribution lines, there are the following advantages.

For example, when installing a digital grid power relay (DGPR) on multiple distribution lines, 1) precise control of flexible power (i.e., current control in SOP for power supply to distribution line loads can be performed precisely at the desired value) ), 2) Improving the distributed power acceptance capacity of the distribution system (i.e., depending on the connection of distributed power, overvoltage may occur in the distribution system and a current that reaches the thermal limit of the line may occur, and overvoltage and overcurrent tolerance limits may reduce the acceptance rate of distributed power. This is the main determining factor. Through voltage and current control at both ends of the SOP, problems in the distribution system due to the connection of distributed power can be alleviated and the acceptance rate of distributed power can be improved accordingly.) 3) Improvement of voltage in the terminal load concentration section (i.e., mountainous areas in Gangwon are generally vulnerable to fires caused by trees, and the load is concentrated at the terminal. In order to prevent fire, low voltage is used over long distances rather than the special high-voltage distribution method) Low-voltage failures of the load occur frequently as the power supply is supplied. Voltage can be improved by using DGPR in such power supply vulnerable areas), 4) Excellent switch operation characteristics (i.e., SOP implemented with power electronic technology is similar to mechanical switches) operation speed performance is superior to that of the NOP implemented as an operating system), 5) excellent failure propagation prevention performance (i.e., the fault current limiting function of the SOP converter can alleviate the problem of increased fault current due to parallel operation of distribution lines. Also, in the event of a fault) FRT (Fault-Ride Through) and LVRT (Low-Voltage Ride Through) functions can be applied), 5) Distribution system power quality improvement (i.e., if SOP can be controlled for each phase, distribution system line imbalance, etc. Compensation is possible. In addition, control such as power factor control and voltage control can be performed at all times for the connected systems at both ends of the SOP.

In addition to the above advantages, the digital grid power relay (DGPR) can manage large-scale power systems by dividing them into small-scale systems at the regional level through the digital grid, so it can connect with other regions through DGPR and distribute power through digital technology. By being flexible, power supply and demand can be stabilized. Additionally, it can prevent large-scale power outages due to the spread of faults that occur in specific areas, thereby increasing the reliability of the power system. In addition, control by linking new and renewable energy power sources can be managed at the regional level, and the volatility of power supply and demand can be compensated for through control through the digital grid, thereby increasing the acceptability of new and renewable energy power sources. In addition, as the power grid becomes parallelized and complicated, the problem of increased fault current occurs. When dividing the power system through a digital grid and linking DGPR, the fault current in each region is limited by the inverter output limiting function, which may lead to short circuits due to the expansion of the power system. It has the advantage of mitigating an increase in fault current by preventing an increase in SCR (Short Circuit Ratio).

In addition, the current distribution system is in a state where the distributed power linkage capacity of some lines has been exceeded due to the inflow of distributed power into the distribution system, and research is being conducted on improving distributed power linkage capacity and energy storage (ESS) technology to make the most of existing distribution lines. has been in progress for a long time, and this research reaches the problem of not being able to fully accommodate the distribution system connection of the gradually developing large-capacity, high-efficiency new and renewable energy, and in this case, the digital grid power relay (DGPR) provides flexible expansion. Due to this, it can be connected to multiple lines without depending on the supply capacity of the distribution line. In particular, it reduces development costs by using adjacent systems as a utilization source by replacing batteries, which account for a large portion of the ESS (Energy Storage System) development cost. It can be significantly reduced, and since the digital grid power relay (DGPR) can secure economic feasibility compared to other technologies, it can be applied in various fields of the distribution system and is expected to have great marketability when commercialized.

Recently, KEPCO Power Research Institute developed a digital grid power router (DGPR) based on a power converter that can distribute power between extra-high voltage distribution systems. The developed DGPR is especially suitable for use with multiple distributed power sources (DER). : Distributed Energy Resource) can be used in a new power supply method that reduces the burden on the distribution system through two-way power integration between multiple distribution lines or multi-microgrids, and controls power flow between distribution lines through the developed DGPR. It is a technology that can effectively manage distribution system utilization and distributed power acceptance rate by effectively responding to distribution line overload or distributed power connection capacity limitations. In addition, the developed DGPR is a technology that can effectively manage distribution system voltage management and distributed power acceptance rate. It is a technology that can innovatively improve distribution system operation and management by reducing losses and enabling effective response to line failures.

Meanwhile, when distributed power is connected to the distribution system, overvoltage and overcurrent in the distribution line may occur. In order to suppress such overvoltage and overcurrent, the connection of distributed power in the distribution system is restricted, which is a direct cause of limiting the acceptance rate of distributed power. , In particular, in the case of radial distribution systems, overvoltage frequently occurs at the end of the line, and there is a high possibility of overcurrent occurring in the secondary line of the distribution transformer, where the output of distributed power is added (generally, the voltage of the distribution system is maintained at around 5% of the rated voltage. must be controlled (the current is limited to a certain value due to the thermal limitations of the line).

Therefore, it is possible to improve the acceptance rate of distributed power by solving the voltage and current problems of the distribution system in which distributed power is saturated through power integration between distribution lines using the DGPR.

The DGPR developed by the KEPCO Power Research Institute mentioned above can flex power between AC systems or between AC/DC systems through AC/DC and DC/AC power conversion, and maintains the DC-Link voltage at a constant level for control purposes. DCCV (DC Constant Voltage) control, DCCP (DC Constant Power) control, which constantly controls the power flowing through the DC-Link, ACCP (AC Constant Power) control, which constantly controls the power flowing through the AC system, and It can perform four control operations of CVCF (Constant Voltage Constant Frequency) to supply power to an AC system independent of the power system.

In addition, the DGPR consists of a stand-alone mode that transfers power between two distribution lines (or microgrids), and a multi-mode, parallel mode, and independent mode that transfers power between three or more distribution lines.

In addition, the DGPR is composed of a back-to-back (BTB) power conversion device for power integration between multiple distribution systems or multiple microgrids, and is equipped with a 500kW switchboard and low-voltage circuit breaker (ACB) to connect the 22.9kV distribution voltage to the DGPR. It is composed.

Figure 2 is an exemplary diagram showing the configuration of a digital grid power relay system according to an embodiment of the present invention.

Each DGPR of the digital grid power relay system is composed of an AC switchboard input/output terminal (i.e., AC input/output terminal) that can be connected to an AC distribution line and a DC bus distribution panel input/output terminal (i.e., DC input/output terminal) that can be connected to a DC system. , the AC input/output terminal is connected to the AC 22.9kV distribution system, and the DC input/output terminal can be designed to enable two-way power flow control by connecting to the DC 750V digital grid.

This embodiment determines the DGPR control mode and at the same time configures a system that enables cooperative operation between devices with commands from a higher-level operating system (EMS, etc.) through a mode selection algorithm according to the operation status of the distribution line.

Here, the DGPR control mode is operated in a total of four control modes (DCCV, DCCP, ACCP, and CVCF), and the description of each control mode is shown in Table 1 below.

control mode Current direction explanation 1st control mode (DCCV) AC to DC - Ability to maintain a constant voltage of the DC link
- Nominal voltage control of DC link
- Performs Master function Second control mode
(DCCP) AC to DC - Function to supply power consistently through DC link
- Supplies surplus power from AC system to DC link
- Perform slave function Third control mode
(ACCP) DC to AC - Ability to supply power consistently to the AC system
- Supply necessary power from DC link to AC system
- Perform slave function Fourth control mode
(CVCF) DC to AC - Function to maintain constant voltage and frequency of AC system
- Supply necessary power from DC link to AC system
- Function used when the AC system loses power or operates independently

By utilizing a total of four control functions of the above DGPR, it is possible to operate in all power relay situations occurring in the distribution system and operate in emergency power generation mode.

Until now, typical power conversion devices, such as grid-connected inverters (DC → AC) or load converters (DC → AC), mainly perform control functions for unidirectional operation, but the DGPR freely performs bidirectional operation according to user commands. It can be done.

The DGPR performs real-time control using upper operating system or user commands according to the control algorithm configured inside the local controller, and can change the controller input command value.

Figure 3 is a flowchart for explaining a control method of a digital grid power relay device according to an embodiment of the present invention. The processor 110 of the digital grid power relay device monitors the status of distributed power sources and loads linked to the distribution system. Consider this to determine the digital grid power relay (DGPR) control mode.

Referring to FIG. 3, the processor 110 checks the normal operation state of the distribution system (S101) and, if the distribution system is not in normal operation state (No in S101), operates in the fourth control mode (CVCF), but operates in the fourth control mode (CVCF). In the operating state (example of S101), generation and load data are collected when the renewable source operates at maximum power generation (S102), and the voltage and frequency of the distribution system are checked to see if they are operating within the normal range (S103). If the voltage and frequency of the system are not within the normal range (No in S103), if a temporary problem occurs in the system due to a failure of some equipment, the fault should be immediately eliminated. For long-term problems, the digital grid power relay (DGPR) should be installed as mentioned above. 4 It operates in control mode (CVCF) and operates emergency power generation operation.

Meanwhile, if the voltage and frequency of the distribution system are operating within the normal range (example in S103), it is checked whether the total power generation from new and renewable sources exceeds the total consumption (S104), and the total power generation from new and renewable sources does not exceed the total consumption. In the case (No in S104), the digital grid power relay (DGPR) operates in the third control mode (ACCP) to accommodate surplus power of the adjacent system.

Meanwhile, if the voltage and frequency of the distribution system are operating within the normal range and the total power generation from renewable sources exceeds the total consumption (example in S104), check whether an energy storage device exists in the distribution system (S105), If an energy storage device exists in the distribution system (example in S105), the energy storage device is operated in maximum charging mode (S106), and it is also compared to see if the power generation amount from renewable sources is greater than the sum of the load and charge amount (S107). ), if the renewable source power generation is greater than the sum of the load and charge amount (example in S107), the renewable source excess power is set (S108).

In addition, even if there is no energy storage device in the distribution system (No in S105), the excess power from new and renewable sources is set (S108).

Meanwhile, after setting the excess power of the renewable source (S108), the excess power is compared with the adjacent system, and if the excess power is smaller than the adjacent system (No in S109), the digital grid power relay (DGPR) is used. It operates in the second control mode (DCCP), and when the excess power is larger than that of the adjacent system (example in S109), it operates in the first control mode (DCCV).

Accordingly, for stable operation of the digital grid power relay system, the digital grid power relay (DGPR) connected to the DC link is operated from the first control mode (DCCV) according to the determined control mode, and if the system If there is no required power, the digital grid power relay (DGPR) maintains a standby state.

As described above, this embodiment effectively responds to various situations (e.g. surplus power, insufficient power, insufficient voltage, independent operation) that may occur in the distribution system by operating the digital grid power relay (DGPR) for each control mode. , it can be confirmed that power flow control between feeders and between banks is possible.

For reference, Figure 4 is an example diagram showing the actual measurement result waveform in the first control mode (DCCV) for controlling the voltage of the digital grid in Figure 3, where the voltage of the DC link capacitor and the current of the AC filter inductor are measured. When acquiring and configuring a voltage (Outer) and current (Inner) feedback control loop, in the corresponding control mode, DGPR operates to maintain a stable DC voltage of the DC link, and the control target is the voltage of the DC link capacitor, and the actual measurement Looking at the resulting waveform, you can see that the DC link voltage (green) remains constant as the current of DGPR1 (yellow), current of DGPR2 (pink), and current of DGPR3 (blue) operate.

In addition, Figure 5 is an example diagram showing the actual measurement result waveform in the second control mode (DCCP) for supplying system power to the digital grid in Figure 3, where the current of the AC filter inductor is acquired to establish a current feedback loop. When configured, in the corresponding control mode, DGPR operates to supply the power that can be supplied to the DC link as constant power, and the control target is the current of the AC filter inductor. Looking at the actual measurement result waveform, the operation of DGPR3 (blue) causes DGPR1 It can be seen that the current (yellow) is reduced.

In addition, Figure 6 is an exemplary diagram showing the actual measurement result waveform in the third control mode (ACCP) for supplying DC link power to the system in Figure 3, where the active and reactive power required by the system are set as command values. When calculating the current through calculation of the grid voltage and configuring a current feedback control loop, in the corresponding control mode, DGPR operates to supply the power that can be supplied to the grid as constant power, and the control target is the current of the AC filter inductor. It becomes. Looking at the actual measurement result waveform, it can be seen that the current of DGPR1 (yellow) increases due to the operation of DGPR3 (blue).

In addition, Figure 7 is an exemplary diagram showing the actual measurement result waveform in the fourth control mode (CVCF) for controlling the voltage and frequency of the system in Figure 3, which is used to configure a voltage feedback control loop for forming an independent system. In this case, the command value to maintain the grid voltage and frequency is set in the corresponding control mode. At this time, the control target is the voltage of the AC filter capacitor. Looking at the actual measurement result waveform, it can be confirmed that a three-phase voltage waveform is output through independent operation of the DGPR. there is.

As described above, this embodiment develops a power relay device using a power conversion device capable of two-way control, allowing power to be exchanged in real time according to system requirements, and can be used to improve distributed power capacity by utilizing surplus power and sharing peak power. It works.

In addition, this embodiment can be used in active SOP to secure distribution system flexibility and reliability through real-time power flow control and voltage management, and can be applied to secure healthy sections such as fault transfer and bypass by participating in system protection cooperation. .

In addition, this embodiment has the effect of enabling terminal load voltage compensation through connection point connection derived through voltage sensitivity analysis and contributing to system stabilization through power supply in an emergency.

In addition, because this embodiment utilizes power from adjacent systems as a source, it can replace batteries, which account for a large portion of ESS development costs, and has the effect of significantly reducing development costs.

In addition, this embodiment can be connected to multiple lines without depending on the supply capacity of the distribution line due to the flexible expandability of the digital grid power relay device, and can also be used for AC/DC distribution connection.

The present invention has been described with reference to the embodiments shown in the drawings, but these are merely exemplary, and those skilled in the art will recognize that various modifications and other equivalent embodiments are possible therefrom. You will understand. Therefore, the scope of technical protection of the present invention should be determined by the scope of the patent claims below. Implementations described herein may also be implemented as, for example, a method or process, device, software program, data stream, or signal. Although discussed only in the context of a single form of implementation (eg, only as a method), implementations of the features discussed may also be implemented in other forms (eg, devices or programs). The device may be implemented with appropriate hardware, software, firmware, etc. The method may be implemented in a device such as a processor, which generally refers to a processing device including a computer, microprocessor, integrated circuit, or programmable logic device. Processors also include communication devices such as computers, cell phones, portable/personal digital assistants (“PDAs”) and other devices that facilitate communication of information between end-users.

110: processor

Claims (12)

It includes a processor that determines the control mode of the digital grid power relay (DGPR) considering the status of distributed power and load connected to the distribution system,
The processor,
Check the normal operation status of the distribution system, check whether the voltage and frequency of the distribution system are operating within the normal range, check whether the total power generation from new and renewable sources exceeds the total consumption, and check whether the total power generation from new and renewable sources exceeds the total consumption. When the consumption amount is exceeded, if an energy storage device exists in the distribution system, the energy storage device is operated in maximum charging mode, and the excess power of the renewable source is set by comparing the sum of the load and charge amount with the renewable source power generation. And, a digital grid power relay device characterized in that one of the first to fourth control modes is determined as the control mode of the digital grid power relay device (DGPR) by comparing the excess power with the adjacent system.
The method of claim 1, wherein the processor:
Check the normal operation status of the distribution system,
Collects generation and load data when renewable sources operate at maximum power generation,
Check whether the voltage and frequency of the distribution system are operating within normal range,
If the voltage and frequency of the distribution system are not within the normal range and a temporary problem occurs in the system due to a failure of some equipment, the fault is immediately cleared, and for long-term failure, the digital grid power relay device is operated in the fourth control mode (CVCF). A digital grid power relay device characterized in that it performs emergency power generation operation.
The method of claim 2, wherein the processor:
If the voltage and frequency of the distribution system are operating within the normal range,
By checking whether the total power generation from renewable sources exceeds the total consumption,
When the total power generation from renewable sources does not exceed the total consumption and is operating within the normal range, the digital grid power relay (DGPR) is operated in the third control mode (ACCP) to accommodate surplus power from adjacent systems. A digital grid power relay device, characterized in that.
The method of claim 3, wherein the processor:
If the voltage and frequency of the distribution system are operating within the normal range and the total power generation from renewable sources exceeds the total consumption,
Check whether an energy storage device exists within the distribution system, operate the energy storage device in maximum charging mode, and compare the sum of the load and charge amount with the renewable source power generation. If the renewable source power generation is greater, the renewable source power generation amount is greater. Setting the excess power, comparing the excess power with the adjacent system, and operating the digital grid power relay (DGPR) in the second control mode (DCCP) when the excess power is smaller than the adjacent system Digital grid power relay device.
The method of claim 4, wherein the processor:
A digital grid power relay device that compares the excess power with an adjacent system and operates the digital grid power relay (DGPR) in the first control mode (DCCV) when the excess power is larger than the adjacent system. .
According to clause 1,
The first control mode (DCCV) is a mode for controlling the voltage of the digital grid,
The second control mode (DCCP) is a mode for supplying system power to the digital grid,
The third control mode (ACCP) is a mode for supplying DC link power to the system,
The fourth control mode (CVCF) is a digital grid power relay device, characterized in that it is a mode for controlling the voltage and frequency of the system.
In the control method of a digital grid power relay device including a processor that determines the control mode of the digital grid power relay (DGPR) considering the status of distributed power and load linked to the distribution system,
The processor checks the normal operation status of the distribution system, checks whether the voltage and frequency of the distribution system are operating within the normal range, checks whether the total power generation from renewable sources exceeds the total consumption, and also checks whether the total renewable source power generation exceeds the total consumption. When the raw power generation exceeds the total consumption, and if an energy storage device exists in the distribution system, the energy storage device is operated in maximum charging mode, and the sum of the load and charging amount is compared with the renewable source power generation. Digital grid power relay, characterized in that setting excess power, comparing the excess power with adjacent systems, and determining the control mode of the digital grid power relay (DGPR) as one of the first to fourth control modes. Control method of the device.
According to clause 7,
To determine one of the first to fourth control modes,
The processor,
Check the normal operation status of the distribution system,
Collects generation and load data when renewable sources operate at maximum power generation,
Check whether the voltage and frequency of the distribution system are operating within normal range,
If the voltage and frequency of the distribution system are not within the normal range and a temporary problem occurs in the system due to a failure of some equipment, the fault is immediately cleared, and for long-term failure, the digital grid power relay device is operated in the fourth control mode (CVCF). A control method of a digital grid power relay device characterized by performing emergency power generation operation.
According to clause 8,
To determine one of the first to fourth control modes,
The processor,
If the voltage and frequency of the distribution system are operating within the normal range,
By checking whether the total power generation from renewable sources exceeds the total consumption,
When the total power generation from renewable sources does not exceed the total consumption and is operating within the normal range, the digital grid power relay (DGPR) is operated in the third control mode (ACCP) to accommodate surplus power from adjacent systems. A control method of a digital grid power relay device, characterized in that.
According to clause 9,
To determine one of the first to fourth control modes,
The processor,
If the voltage and frequency of the distribution system are operating within the normal range and the total power generation from renewable sources exceeds the total consumption,
Check whether an energy storage device exists within the distribution system, operate the energy storage device in maximum charging mode, and compare the sum of the load and charge amount with the renewable source power generation. If the renewable source power generation is greater, the renewable source power generation amount is greater. Setting the excess power, comparing the excess power with the adjacent system, and operating the digital grid power relay (DGPR) in the second control mode (DCCP) when the excess power is smaller than the adjacent system Control method of digital grid power relay device.
According to clause 10,
To determine one of the first to fourth control modes,
The processor,
A digital grid power relay device that compares the excess power with an adjacent system and operates the digital grid power relay (DGPR) in the first control mode (DCCV) when the excess power is larger than the adjacent system. control method.
According to clause 7,
The first control mode (DCCV) is a mode for controlling the voltage of the digital grid,
The second control mode (DCCP) is a mode for supplying system power to the digital grid,
The third control mode (ACCP) is a mode for supplying DC link power to the system,
The fourth control mode (CVCF) is a control method of a digital grid power relay device, characterized in that it is a mode for controlling the voltage and frequency of the system.

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