KR102624161B1 - Method for controlling droop in dc microgrid and a device performing the same - Google Patents

Abstract

A droop control method in a DC microgrid and a device for performing the same are disclosed. The droop control device that controls the output of the converter connected one to one in the DC microgrid includes a receiver that receives a first junction temperature signal for the first junction temperature of the power semiconductor included in the converter from a temperature sensor included in the converter. and a control module that determines a droop coefficient based on the first junction temperature signal and controls the output of the converter based on the droop coefficient.

Description

Droop control method in DC microgrid and device for performing the same {METHOD FOR CONTROLLING DROOP IN DC MICROGRID AND A DEVICE PERFORMING THE SAME}

The disclosure below relates to a droop control method in a DC microgrid and a device for performing the same.

Smart grid is a fusion of information and communication technology with the existing power grid and is a core technology for low-carbon, green growth. An intelligent power grid in the concept of a small area that can be self-sufficient in energy by using distributed power and storage devices is called a microgrid, and can be divided into DC microgrid and AC microgrid depending on the distribution method. In a microgrid where multiple power sources are connected, it is necessary to control the output of each power source, and a commonly used method to control the output is the droop control method.

As a related prior art, there is Korean Patent Publication No. 10-1431047 (title of the invention: Cooperative droop control device and method for stand-alone DC microgrid)

The background technology described above is possessed or acquired by the inventor in the process of deriving the disclosure of the present application, and cannot necessarily be said to be known technology disclosed to the general public before this application.

Various embodiments can prevent deterioration of a power semiconductor by controlling the droop coefficient based on the temperature of the power semiconductor.

Various embodiments can have high reliability by directly transmitting and receiving the temperature of the power semiconductor between non-centralized droop control devices.

However, technical challenges are not limited to the above-mentioned technical challenges, and other technical challenges may exist.

According to various embodiments, a droop control device that controls the output of a one-to-one connected converter in a DC microgrid determines the first junction temperature of the power semiconductor included in the converter from the temperature sensor included in the converter. It may include a receiver that receives a signal and a control module that determines a droop coefficient based on the first junction temperature signal and controls the output of the converter based on the droop coefficient.

The device transmits the first junction temperature signal to a droop control device different from the droop control device, and transmits a second junction temperature signal from the other droop control device for a second junction temperature of a power semiconductor different from the power semiconductor. It may further include a communication module that receives a junction temperature signal.

The control module may determine the droop coefficient based on the first junction temperature signal and the second junction temperature signal, and control the output of the converter based on the droop coefficient.

According to various embodiments, a droop control method of a droop control device that controls the output of a one-to-one connected converter in a DC microgrid includes measuring the first junction temperature of the power semiconductor included in the converter from the temperature sensor included in the converter. The method may include receiving a first junction temperature signal, determining a droop coefficient based on the first junction temperature signal, and controlling the output of the converter based on the droop coefficient.

The method includes transmitting the first junction temperature signal to a droop control device different from the droop control device and transmitting a second junction temperature signal of a power semiconductor different from the power semiconductor from the other droop control device. It further includes the operation of receiving a two-junction temperature signal, wherein the controlling operation includes determining the droop coefficient based on the first junction temperature signal and the second junction temperature signal, and determining the droop coefficient of the converter based on the droop coefficient. It may be controlling the output.

Figure 1 shows an example of a DC microgrid.
Figure 2 is to explain an example of a control method for the output of a converter within a DC microgrid.
Figure 3 is a diagram for explaining the switching operation of a power semiconductor (eg, IGBT) included in the converter.
Figure 4 is a diagram to explain an example of converter failure due to deterioration of power semiconductors.
Figure 5 is a diagram for explaining a droop control method according to various embodiments.
Figure 6 is a block diagram of the structure of a droop control device according to various embodiments.
Figure 7 shows an example of the output current of the converter when using a droop control method, according to various embodiments.
Figure 8 shows an example of the temperature of a power semiconductor when using a droop control method according to various embodiments.
9 shows another example of a schematic block diagram of a droop control device according to various embodiments.

Specific structural or functional descriptions of the embodiments are disclosed for illustrative purposes only and may be changed and implemented in various forms. Accordingly, the actual implementation form is not limited to the specific disclosed embodiments, and the scope of the present specification includes changes, equivalents, or substitutes included in the technical idea described in the embodiments.

Terms such as first or second may be used to describe various components, but these terms should be interpreted only for the purpose of distinguishing one component from another component. For example, a first component may be named a second component, and similarly, the second component may also be named a first component.

When a component is referred to as being “connected” to another component, it should be understood that it may be directly connected or connected to the other component, but that other components may exist in between.

Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as “comprise” or “have” are intended to designate the presence of the described features, numbers, steps, operations, components, parts, or combinations thereof, and are intended to indicate the presence of one or more other features or numbers, It should be understood that this does not exclude in advance the possibility of the presence or addition of steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art. Terms as defined in commonly used dictionaries should be interpreted as having meanings consistent with the meanings they have in the context of the related technology, and unless clearly defined in this specification, should not be interpreted in an idealized or overly formal sense. No.

Hereinafter, embodiments will be described in detail with reference to the attached drawings. In the description with reference to the accompanying drawings, identical components will be assigned the same reference numerals regardless of the reference numerals, and overlapping descriptions thereof will be omitted.

Figure 1 shows an example of a DC microgrid.

Referring to Figure 1, a DC microgrid may include multiple power sources (e.g. Photovoltaic, Fuel Cell, etc.). Multiple power sources can be connected by a DC bus within the DC microgrid. Within a DC microgrid, each power source is connected one-to-one to a converter, and control of the output of each converter may be required.

FIG. 2 may be used to explain an example of a control method for the output of a converter within a DC microgrid.

Referring to Figure 2, a droop control method that determines the droop coefficient based on the output current of the converter can be used, and can be expressed as Equation 1 below.

[Equation 1]

At this time, V _ref and V _ref * are reference voltages, R _d may be a virtual resistance, and i _o may be the output current of the converter, and the role played by the virtual resistance (R _d ) can be understood as playing the same role as the droop coefficient. there is. The droop control method based on the output current of the converter is not only used for power distribution of different power sources in a DC microgrid, but can also be used when multiple converters are connected in parallel to the same power source. At this time, the output current of each converter can be determined as in Equation 2 below.

[Equation 2]

Here, the virtual resistance (R _d1, R _d2 ) can be understood as playing the same role as the droop coefficient, and the virtual resistance ((R _d1, R _d2 ) means that the output current (I _o1, I _o2 ) of each converter is uniform. It may be decided to distribute it accordingly.

Below, with reference to FIGS. 3 and 4 , the deterioration of the power semiconductor that may occur when the droop coefficient (e.g., virtual resistance) is determined based on the output current of the converter will be described.

Figure 3 is a diagram for explaining the switching operation of a power semiconductor (eg, IGBT) included in the converter.

Referring to Figure 3, a power semiconductor (eg, IGBT) may have a gate, a collector, and an emitter terminal. When a voltage higher than the driving voltage is applied to the gate of a power semiconductor (e.g. IGBT), a channel is formed between the collector and emitter, which can play a switching role in the circuit in the converter.

Figure 4 is a diagram to explain an example of a converter failure due to deterioration of a power semiconductor.

Referring to Figure 4, the junction temperature of power semiconductors may increase due to continuous switching operations or excessive current. The junction temperature (T _j ) of the power semiconductor can be expressed as Equation 3 below.

[Equation 3]

At this time, T _a is the ambient temperature, R _th is the thermal resistance from the surroundings to the junction, and P _loss may be the power loss. Power loss (P _loss ) can be determined as the sum of conduction loss (P _cond ) and switching loss (P _sw ), and conduction loss (P _cond ) and switching loss (P _sw ) can be expressed as Equation 4 below. .

[Equation 4]

,

Power semiconductors can have junction temperature limits (e.g., about 150°C for IGBTs) by using silicon as a base material. If the heat dissipation design or specifications of each converter are different, a difference in junction temperature of power semiconductors may occur between converters, and in converters with relatively high junction temperatures, failures such as destruction of emitter bonding wires may occur due to deterioration of power semiconductors. there is. This can increase the output current of the remaining converters and the temperature of the power semiconductors and shorten the lifespan of the converters in the DC microgrid.

In order to improve the reliability of the DC microgrid, it is necessary to control the rise in the junction temperature of the power semiconductor by individually controlling the output current of each converter, and the signal for the junction temperature of the power semiconductor is drooped in a distributed manner rather than centralized. There may be a need to transmit and receive data between control devices.

Figure 5 is a diagram for explaining a droop control method according to various embodiments.

Referring to Figure 5, the DC microgrid 500 includes one or more power sources (e.g., DC power sources) (501, 503), one or more droop control devices (511, 513), and one or more converters (e.g., DC/ DC converter) (521, 523), and DC Bus.

Each power source (501, 503) is connected to a converter (521, 523), and the output of each converter (521, 523) can be controlled by the droop control devices (511, 513). The output lines of the converters 521 and 523 are connected to the DC Bus, and loads that require DC power (e.g., electric vehicles) can receive power through the DC Bus.

In order to supply stable power to the DC microgrid 500 and prevent deterioration of the power semiconductors included in the converters 521 and 523, the converters 521 and 523 are controlled through a droop control method based on the temperature of the power semiconductors. There may be a need to control the output current. The converters 521 and 523 may send signals 531 and 533 about the junction temperature of the power semiconductors contained within the converters 521 and 523 to the droop control devices 511 and 513 connected one to one. Each of the droop control devices 511 and 513 may transmit and receive signals 531 and 533 for the received contact temperature of the power semiconductor between the droop control devices 511 and 513. A method of determining the droop coefficient based on the junction temperature of a power semiconductor will be described in detail below, taking any one of the droop control devices 511 and 513 (eg, 511) as an example.

The droop control device 511 calculates the droop coefficient based on the signal 531 for the power semiconductor junction temperature included in the converter 521 and the signal 543 for the power semiconductor junction temperature included in the converter 523. It is possible to determine and control the output current of the converter (e.g. 521) based on the droop coefficient. The droop coefficient based on the junction temperature of the power semiconductor can be determined as shown in Equation 5 below.

[Equation 5]

At this time, k _d1 and k _d2 are the droop coefficients of the converters 521 and 523, T _j1 and T _j2 are the power semiconductor junction temperatures of the converters 521 and 523, and k may be an arbitrary value determined by the user.

Figure 6 is a block diagram of the structure of a droop control device according to various embodiments.

Referring to FIG. 6, the droop control device 600 (e.g., the droop control devices 511 and 513 of FIG. 5) may include a receiver 610, a control module 620, and a communication module 630.

The receiver 610 may receive a signal about the junction temperature of the power semiconductor from a temperature sensor included in the converter 640 (e.g., converters 521 and 523 in FIG. 5). The communication module 630 can transmit and receive a signal about the junction temperature of the power semiconductor received by the receiver 610 between the droop control device 600 (e.g., the droop control devices 511 and 513 in FIG. 5). The control module 620 determines the droop coefficient based on the signal about the junction temperature of the power semiconductor received by the receiver 610 and the communication module 630, and converts the converter 640 (e.g., The output current of the converters 521 and 523 in Figure 5 can be controlled.

Figure 7 shows an example of the converter output current when using a droop control method according to various embodiments, and Figure 8 shows an example of the temperature of a power semiconductor when using a droop control method according to various embodiments. indicates.

Referring to Figures 7 and 8, when using the droop control method based on the temperature of the power semiconductor, the output current of each converter is individually controlled compared to when using the droop control method based on the output current of the converter, so that each converter Instead of a difference in output current between the converters, it can be seen that the temperature difference between the power semiconductors of each converter decreases.

9 shows another example of a schematic block diagram of a droop control device according to various embodiments.

Referring to FIG. 9 , the droop control device 900 may be substantially the same as the droop control devices 511 , 513 , and 600 described with reference to FIGS. 1 to 8 . The droop control device 900 may include a memory 910 and a processor 930.

According to various embodiments, the memory 910 may store instructions (eg, programs) executable by the processor 930. For example, the instructions may include instructions for executing the operation of the processor 930 and/or the operation of each component of the processor 930.

According to various embodiments, the memory 910 may be implemented as a volatile memory device or a non-volatile memory device. Volatile memory devices may be implemented as dynamic random access memory (DRAM), static random access memory (SRAM), thyristor RAM (T-RAM), zero capacitor RAM (Z-RAM), or twin transistor RAM (TTRAM). Non-volatile memory devices include EEPROM (Electrically Erasable Programmable Read-Only Memory), flash memory, MRAM (Magnetic RAM), Spin-Transfer Torque (STT)-MRAM (MRAM), and Conductive Bridging RAM (CBRAM). , FeRAM (Ferroelectric RAM), PRAM (Phase change RAM), Resistive RAM (RRAM), Nanotube RRAM (Nanotube RRAM), Polymer RAM (PoRAM), Nano Floating Gate Memory (NFGM), holographic memory, molecular electronic memory device, and/or insulation resistance change memory.

According to various embodiments, the processor 930 may execute computer-readable code (eg, software) stored in the memory 910 and instructions triggered by the processor 930. The processor 930 may be a data processing device implemented in hardware that has a circuit with a physical structure for executing desired operations. The intended operations may include, for example, code or instructions included in the program. Data processing devices implemented in hardware include, for example, a microprocessor, central processing unit, processor core, multi-core processor, and multiprocessor. , ASIC (Application-Specific Integrated Circuit), and FPGA (Field Programmable Gate Array).

According to various embodiments, operations performed by the processor 930 are substantially the same as operations of the droop control devices 511, 513, and 600 described with reference to FIGS. 1 to 8. Accordingly, detailed description will be omitted.

The embodiments described above may be implemented with hardware components, software components, and/or a combination of hardware components and software components. For example, the devices, methods, and components described in the embodiments may include, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, and a field programmable gate (FPGA). It may be implemented using a general-purpose computer or a special-purpose computer, such as an array, programmable logic unit (PLU), microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and software applications running on the operating system. Additionally, a processing device may access, store, manipulate, process, and generate data in response to the execution of software. For ease of understanding, a single processing device may be described as being used; however, those skilled in the art will understand that a processing device includes multiple processing elements and/or multiple types of processing elements. It can be seen that it may include. For example, a processing device may include multiple processors or one processor and one controller. Additionally, other processing configurations, such as parallel processors, are possible.

Software may include a computer program, code, instructions, or a combination of one or more of these, which may configure a processing unit to operate as desired, or may be processed independently or collectively. You can command the device. Software and/or data may be used on any type of machine, component, physical device, virtual equipment, computer storage medium or device to be interpreted by or to provide instructions or data to a processing device. , or may be permanently or temporarily embodied in a transmitted signal wave. Software may be distributed over networked computer systems and stored or executed in a distributed manner. Software and data may be stored on a computer-readable recording medium.

The method according to the embodiment may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer-readable medium. A computer-readable medium may store program instructions, data files, data structures, etc., singly or in combination, and the program instructions recorded on the medium may be specially designed and constructed for the embodiment or may be known and available to those skilled in the art of computer software. there is. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, and magnetic media such as floptical disks. -Includes optical media (magneto-optical media) and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, etc. Examples of program instructions include machine language code, such as that produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc.

The hardware devices described above may be configured to operate as one or multiple software modules to perform the operations of the embodiments, and vice versa.

As described above, although the embodiments have been described with limited drawings, those skilled in the art can apply various technical modifications and variations based on this. For example, the described techniques are performed in a different order than the described method, and/or components of the described system, structure, device, circuit, etc. are combined or combined in a different form than the described method, or other components are used. Alternatively, appropriate results may be achieved even if substituted or substituted by an equivalent.

Therefore, other implementations, other embodiments, and equivalents of the claims also fall within the scope of the claims described below.

Claims (5)

In a device for controlling the output of a converter in a DC microgrid,
memory containing instructions; and
a processor operatively coupled to the memory and configured to execute the instructions;
When the instructions are executed by the processor, the processor:
Determining a droop coefficient based on the difference between a first junction temperature of a power semiconductor included in the converter and a second junction temperature of a power semiconductor included in another converter in the DC microgrid,
Apparatus for controlling the output of the converter based on the droop coefficient.
According to paragraph 1,
Communication module for transmitting the first junction temperature and receiving the second junction temperature
A device further comprising:
delete In a method for controlling the output of a converter in a DC microgrid,
determining a droop coefficient based on a difference between a first junction temperature of a power semiconductor included in the converter and a second junction temperature of a power semiconductor included in another converter in the DC microgrid; and
Operation of controlling the output of the converter based on the droop coefficient
Method, including.
delete