CN210380245U

CN210380245U - Direct current energy consumption system and electric power system

Info

Publication number: CN210380245U
Application number: CN201920726984.XU
Authority: CN
Inventors: 许超群; 曾嵘; 余占清; 赵彪; 张翔宇
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2019-05-21
Filing date: 2019-05-21
Publication date: 2020-04-21
Anticipated expiration: 2029-05-21

Abstract

The present disclosure relates to a direct current energy consumption system and an electric power system. Provided is a direct current energy consumption system, including: an energy consuming part comprising an energy consuming device; and a switching section connected in series with the energy consuming section, the switching section including at least one switching module, the switching module including: a first node and a second node; a switching branch and a snubber branch connected in parallel between the first and second nodes, wherein the switching branch comprises a power electronic switch and the snubber branch comprises at least a capacitor; and a protection module configured to protect the power electronic switch from overvoltage and/or overcurrent.

Description

Direct current energy consumption system and electric power system

Technical Field

The present disclosure relates to a direct current energy consumption system and an electric power system.

Background

In recent years, high-voltage direct-current transmission technology has been developed at a high speed. On the other hand, the demand for clean energy is increasing. Wind farms (also called wind farms) grid-connected flexible direct current transmission systems (VSC-HVDC, high voltage direct current transmission based on voltage source converters) are finding more and more widespread application.

When the VSC-HVDC normally operates, the energy generated when the wind generation set is connected in an isolated island mode keeps balance with the energy consumed by the receiving end alternating current power grid. When the receiving end alternating current power grid fails, the energy consumed by the receiving end alternating current power grid is reduced, and the capacity of receiving power is limited. And the voltage and the frequency of the sending-end wind power plant cannot be changed in a short time because the frequency and the voltage information of the alternating current power grid cannot be directly obtained. This results in energy being accumulated on the dc line and surplus power flows into the Modular Multilevel Converter (MMC), thereby causing converter sub-module capacitors to be charged, voltage rise, indirectly resulting in dc line voltage rise. If the control of the receiving end converter station on the direct current line fails, the line can be tripped in serious conditions.

Accordingly, there is a need for improved dc power consuming systems and power systems.

SUMMERY OF THE UTILITY MODEL

According to an aspect of the present disclosure, there is provided a direct current energy consumption system, including: an energy consuming part comprising an energy consuming device; and a switching section connected in series with the energy consuming section, the switching section including at least one switching module, the switching module including: a first node and a second node; a switching branch and a snubber branch connected in parallel between the first and second nodes, wherein the switching branch comprises a power electronic switch and the snubber branch comprises at least a capacitor; and a protection module configured to protect the power electronic switch from overvoltage and/or overcurrent.

According to an aspect of the present disclosure, there is provided a direct current energy consumption system, including: an energy consuming part comprising an energy consuming device; and a switching section connected in series with the energy consuming section, the switching section including at least one switching module, the switching module including: a first node and a second node; a switching leg connected between the first node and a second node, the switching leg including a power electronic switch; a protection module configured to protect the power electronic switch from overvoltage and/or overcurrent; and a reverse current protection branch connected between the first node and the second node in anti-parallel with the switching branch to prevent a reverse current from flowing through the switching branch.

In some embodiments, the at least one switch module comprises a plurality of the switch modules connected in series with each other.

In some embodiments, the snubber branch is configured to snubber the voltage across the switch on or in the switch branch and not pass a dc current through the snubber branch.

In some embodiments, an end of the switching section remote from the energy consuming section is adapted to be connected to a dc transmission line, and the energy consuming section is configured to receive power from the dc transmission line via the switching section.

In some embodiments, the protection module is connected between the first node and the second node in parallel with the switching leg.

In some embodiments, the protection module comprises a metal oxide arrester (MOV).

In some embodiments, in the plurality of switch modules, the second node of an upstream switch module is coupled to the first node of a downstream switch module immediately adjacent thereto.

In some embodiments, the energy consuming device is a centralized resistive energy consuming device, the energy consuming portion being configured to be remote from the switching portion such that heat generated by the energy consuming portion does not affect the switching portion.

In some embodiments, the power electronic switch comprises a fully-controlled power electronic switch.

In some embodiments, the power electronic switch comprises any one or more of: IGBT, IGET, IGCT.

In some embodiments, each switch module further comprises: a reverse current protection branch connected between the first node and the second node in anti-parallel with the switching branch to prevent reverse current from flowing through the switching branch.

In some embodiments, each switch module further comprises: a bypass branch in parallel with the switch branch, the bypass branch including a bypass switch, the bypass branch configured to pass current therethrough without passing through the switch branch when the bypass switch is turned on.

In some embodiments, an end of the switch portion away from the energy consumption portion is adapted to be connected to a high-potential dc transmission line of dc transmission lines, an end of the energy consumption portion away from the switch portion is adapted to be connected to a low-potential dc transmission line of the dc transmission lines, the dc transmission lines are adapted to be connected to an ac power system, and the dc energy consumption system further includes a control portion configured to generate a control signal for a switch branch of each of the switch modules based on a voltage on the dc transmission line to control the on of the switch branch of each of the switch modules, so that current passes through the energy consumption device to consume energy.

In some embodiments, the at least one switching module comprises a plurality of said switching modules connected in series with each other, and the dc energy consuming system further comprises a further energy consuming device configured in parallel with one or more of said plurality of said switching modules.

In some embodiments, the additional energy consuming device comprises a metal oxide arrester.

In some embodiments, the switch module further comprises a power consuming branch connected between the first node and the second node, the power consuming branch comprising a power consuming device and a power electronic switch in series with each other.

According to an aspect of the present disclosure, there is provided a power system including: a DC subsystem comprising a DC transmission line; and the direct current energy consumption system according to any embodiment, which is connected to the direct current transmission lines, wherein one end of the switch portion, which is far away from the energy consumption portion, is connected to a high potential transmission line of the direct current transmission lines, and one end of the energy consumption portion, which is far away from the switch portion, is connected to a low potential transmission line of the direct current transmission lines.

In some embodiments, the power system further comprises: an AC subsystem receiving power from the DC transmission line and converting to AC power, the AC subsystem including a DC-to-AC conversion device.

In some embodiments, the power system further comprises: a power generation or conversion system configured to provide DC power to the DC link.

In some embodiments, the power generation or conversion system comprises one of: a direct current power generation system; and an AC power generation system and an AC-DC conversion device connected between the AC power generation system and the DC transmission line.

In some embodiments, the ac power generation system comprises a wind farm.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the disclosure and together with the description, serve to explain the principles of the disclosure, in which:

FIG. 1 shows a schematic diagram of a power system;

FIG. 2 is a schematic diagram illustrating power flow and a fault condition of the power system shown in FIG. 1;

FIG. 3 shows a schematic diagram of an energy consuming system and an electrical power system incorporating the energy consuming system, according to one embodiment of the present disclosure;

FIG. 4 illustrates a schematic diagram of a specific implementation of an energy consuming system according to one embodiment of the present disclosure;

FIG. 5 shows a flow diagram of an energy consuming method for a power system according to one embodiment of the present disclosure;

FIG. 6 illustrates a specific example of the steps of generating a control signal of an energy consuming method according to one embodiment of the present disclosure;

fig. 7 illustrates a schematic diagram of a control part for an energy consuming system or an electric power system including the energy consuming system and a control process thereof according to an embodiment of the present disclosure; and

fig. 8-12 illustrate some variations of modules of a switch according to embodiments of the present disclosure.

Detailed Description

Specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be understood that the description of the embodiments is illustrative only and is not intended to limit the claimed invention in any way. Unless specifically stated otherwise or the context or principles thereof indicate or imply, the relative arrangement of components and steps, expressions and values, etc. in the exemplary embodiments are not intended to limit the invention claimed herein.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. In addition, references to "coupled/connected" in this application include both direct and indirect couplings; in other words, "a is coupled/connected to B" or "a is coupled/connected to B" includes that a is directly coupled/connected to B, and that a and B are indirectly coupled/connected and that other intermediate elements may be present between a and B.

Semiconductor-based power switching devices are also referred to herein as power electronic switching devices or power switching devices (or power devices).

Fig. 1 shows a schematic diagram of a power system. As shown in fig. 1, the power system 100 may include a wind farm (or wind power plant) 101. The ac power generated by the wind farm 101 is converted into dc power (e.g., high voltage dc power) by an inverter 105(MMC1) and transmitted to the receiving end through a dc transmission line 107. At the receiving end, the dc power is converted to ac power by an inverter 109(MMC2) and provided to a subsequent ac grid 113.

Optionally, the electronic system 100 may further include ac-

ac conversion devices

103 and 111 to convert ac power.

Fig. 2 shows a schematic diagram of the power flow and the situation of a fault of the power system shown in fig. 1. As shown in FIG. 2, the power (e.g., active power) generated by the wind farm 101 is P_wind. Power P generated by a wind farm 101_windConsumed by a transport device such as

MMCs

105 and 109 by a small fraction, e.g., P_MMC1And P_MMC2The remaining power is supplied to the AC network (P)_{ac_rev}) And the power is supplied to an alternating current power grid for consumption. Under normal operation, the energy generated by the wind farm 101 is substantially balanced with the energy consumed by the receiving ac grid.

However, when the receiving ac grid fails (as indicated by reference numeral 201 in fig. 2), the energy that the ac grid can consume is reduced and the ability to accept power is limited. And the voltage and the frequency of the sending-end wind power plant cannot be changed in a short time because the frequency and the voltage information of the alternating current power grid cannot be directly obtained. This results in energy being accumulated on the dc lines and excess power flowing into the modular multilevel converter (MMC1 and/or MMC2) causing the converter sub-module capacitors to be charged and the voltage to rise, indirectly resulting in a rise in the dc line voltage. If the control of the receiving end converter station on the direct current line fails, the line can be tripped in serious conditions.

To avoid the fault, the surplus power is consumed by using the energy consumption of the dc energy consumption device, for example, the consumed power can be controlled by the chopper circuit to achieve power balance.

At present, the direct current energy consumption device mainly has two schemes. One scheme is a modularized distributed resistance type direct current energy consumption device, the modularized design is adopted to reduce current fluctuation, and dynamic and static voltage sharing is well realized; however, this solution requires the use of many high-rated semiconductor devices, and the circuit is costly and bulky. Moreover, for the distributed resistance type direct current energy consumption device, the distributed resistance must be arranged in the module, that is, the distributed resistance must be arranged around the switch device, so that when the direct current energy consumption device operates, the high temperature of the distributed resistance can cause the switch device to work abnormally, and a high-power water cooling system must be used for heat dissipation. This increases the cost and reduces the reliability and lifetime of the switching device.

Another solution is a concentrated resistance chopping energy dissipation device. However, in the scheme, the switch series connection technology is used, so that the dynamic and static voltage sharing of the straight series of the switch devices is difficult to realize, and the performance requirement on the devices is high.

Due to the capacity limitation of a single switching device, in the case of performing high-power conversion, such as direct-current transmission, the direct-current side voltage of the switching device often reaches tens of kV or hundreds of kV. However, the highest voltage class IGBTs and IGCTs currently in commercial use are only 6.5kV, in which case tens or hundreds of switching devices are required in series to share the higher voltage. When the switching devices are directly connected in series for use, because the switching speed of the switching devices is high and is basically completed within microseconds, a part of the switching devices are inevitably turned on or turned off firstly, and a part of the switching devices are turned on or turned off later. This results in a high probability that the voltage experienced by each switching device exceeds its rated voltage, resulting in damage to the switching device.

In view of one or more of the above problems, the inventors of the present application propose novel techniques to provide improved dc power consuming systems, power systems, and related methods, among others.

FIG. 3 shows a schematic diagram of an energy consuming system and a power system incorporating the energy consuming system, according to one embodiment of the present disclosure. FIG. 4 shows a schematic diagram of a specific implementation of an energy consuming system according to an embodiment of the present disclosure. The following description is made with reference to fig. 3 and 4.

As shown in fig. 3, power system 300 may include a dc subsystem. The dc subsystem may include a dc link 107. In some examples, power system 300 may also include a power generation or conversion system. The power generation or conversion system may be configured to provide dc power to the dc link. The power generation or conversion system may include (but is not limited to): a direct current power generation system; and/or ac power generation systems and combinations. For example, the dc power generation system may include a dc power generation device such as a solar farm. For example, the alternator system may include a wind farm (such as an offshore or land-based wind farm), a thermal power plant (such as a geothermal or hot-melt salt power plant, etc.), and the like. The ac-dc conversion device may be configured to be connected between an ac power generation system and a dc transmission line to provide dc power to the dc transmission line.

In the example shown in fig. 3, a wind farm is illustrated and described as an example. In the power system 300 shown in fig. 3, an ac-ac conversion device 103, an MMC 105, and a wind farm 101 may also be included. It should be understood that the present disclosure is not limited to this embodiment, as the dc subsystem may include a dc transmission line, or may include one or more additional components.

Here, in the context of the present application, the term high voltage refers to voltages of 10KV or more, thus also encompassing extra high voltages and extra high voltages. While the techniques disclosed herein are particularly applicable to high voltage power transmission, it should be understood that the present application is not so limited.

Power system 300 may also include an ac subsystem. The ac subsystem may receive power from the dc transmission line and convert to ac power. In some embodiments, the ac subsystem may include a dc-ac conversion device, such as dc-ac conversion device 109(MMC 2). In other embodiments, the ac subsystem may further include an ac-to-ac conversion device 111. The ac subsystem may also include an ac power grid 113. Here, the ac power grid 103 is used to represent any device, apparatus, or facility connected downstream that receives ac power.

As shown in fig. 3, the power system 300 further includes a dc power consuming system connected to the dc transmission line. As shown in fig. 3, the dc energy consumption system may include an energy consumption unit 301 including an energy consumption device (a resistor Ri is schematically illustrated as an energy consumption device in the figure). The dc power consuming system further includes a switching portion 303 connected in series with the power consuming portion 301. In some embodiments, one end of the switch portion 303 is connected to the energy consuming portion 301, and an end of the switch portion away from the energy consuming portion may be connected to one of the dc transmission lines, such as a high potential transmission line. An end of the energy consuming part 301 remote from the switching part may be connected to another one of the dc transmission lines, for example, a low potential transmission line. The energy consuming part 301 may receive power from the dc transmission line via the switching part 303.

As shown in fig. 4, the switching section may include at least one switching module 410. In the embodiment shown in fig. 4, the switching section may include a plurality of switching modules 410, such as switching modules sm1.. SMn, connected in series with each other.

The switch module may include a first node 401 and a second node 403. The switch module may further comprise a switch leg 411 and a buffer leg 413, both connected in parallel with each other between the first node 401 and the second node 403.

The switching branch 411 is configured to be capable of being turned on or off (opened) according to a control signal. The switching leg 411 may include a power electronic switch T. Preferably the power electronic switch may comprise a fully controlled power electronic switch, for example. In some embodiments, the power electronic switch may comprise any one or more of: IGBT, IGET, IGCT. It should be understood here that, only in the embodiment shown in fig. 4, the switching leg 411 is shown as including only one power electronic switch T, but the present disclosure is not limited thereto. In other embodiments, the switching leg 411 may also include a plurality of power electronic switches or a combination thereof. Incidentally, in the context of the present application, "a plurality" means more than one, that is, may be two or more.

The buffer branch 413 may include at least a capacitor C. A snubber branch is provided to buffer the voltage across the switching branch (or the switch therein) to slow the rate of rise of the voltage. The buffer branch 413 is configured not to pass a direct current. In some embodiments, as shown in fig. 4, the buffer branch 413 may further include a resistor R. The resistor R may be used to limit the charging and discharging current to the capacitance. It should be understood that the configuration of the snubber branch is not limited to the embodiment shown in fig. 4, and may have various forms as long as it enables the buffering of the voltage across the switching branch (or the switch therein).

In this way, the rising speed of the voltage of the switching devices can be slowed down when the switching devices are turned off, so that the dynamic voltage difference among the switching devices is reduced.

In some embodiments, the switch module 410 may further include a protection module (represented by MOV) configured to protect the power electronic switches of the switching legs from overstress, such as overvoltage and/or overcurrent. In some embodiments, the protection module may include an arrester or varistor, etc., such as a metal oxide arrester (MOV). Here, the protection modules are collectively indicated by MOVs. In the embodiment shown in fig. 4, the protection module is implemented as a branch 415 connected between the first node and the second node in parallel with the switching branch; however, the present disclosure is not limited thereto. For example, in other embodiments, a surge arrester (MOV) may also be provided in parallel with the power electronic switch in the switching leg, rather than in parallel with the entire switching leg.

By providing a protection module MOV, the voltage across the switching leg or the switching device therein can be stabilized and overvoltage and overcurrent protection can be provided thereto. When the voltage value reaches the action voltage at two ends of the lightning arrester, the resistance value of the lightning arrester is greatly reduced due to the nonlinear resistance effect, and the lightning arrester can flow electric charges to limit the amplitude of overvoltage and release overvoltage energy; meanwhile, the lightning arrester can cut off follow current. Thus, overvoltage and overcurrent protection is realized. According to the embodiment of the application, the reliability of the switching device can be improved, and the redundancy is increased.

In some embodiments, among the plurality of switch modules, the second node (low potential node) 403 of the switch module located upstream (e.g., on the high potential side, or on the side away from the energy consumer Ri) may be coupled to the first node (high potential node) 401 of the downstream switch module located immediately adjacent thereto.

In an embodiment of the present disclosure, energy consuming devices 303(Ri) may be centralized resistive energy consuming devices. The energy consumption part 303 may be disposed away from the switching part 301. For example, a plurality of resistors or resistive devices for dissipating energy may be relatively concentrated in one location, while the switching portion is remote from the energy dissipating portion. Thus, the switching section can be substantially unaffected by the heat generated by the energy consuming section. And, because the switch portion is separated with the power consumption portion, the heat that both dispel can not superpose. Therefore, the high-power water cooling system is not used for radiating heat of the energy consumption part and the switch part, and only an air cooling system or natural cooling is adopted. Thus, the reliability of the device can be improved, and the cost can be remarkably reduced.

In some embodiments, the switching module may further include a reverse current protection branch 417 connected between the first node and the second node in anti-parallel with the switching branch to prevent reverse current from flowing through the switching branch. In some embodiments, the reverse current protection branch 417 may include a diode D, as shown in fig. 4. The current direction of the diode D is arranged opposite to the current direction in the switching branch.

In some embodiments, the switch module may further include a bypass leg 419 in parallel with the switch leg, which may include a bypass switch S. The bypass branch is configured to pass current therethrough without passing through the switch branch when the bypass switch is on. Thus, a switch module can be bypassed in case of failure.

According to some embodiments of the disclosure, the energy consumption system may further include a control portion. The control part can be configured to generate a control signal for the switching branch of each switching module based on the voltage on the dc transmission line to control the on of the switching branch of each switching module, so that current passes through the energy consumption device for energy consumption.

By now it should be appreciated that the present disclosure also provides a power system, which may include: a DC subsystem comprising a DC transmission line; and the direct current energy consumption system according to any embodiment of the present disclosure, which is connected to the direct current transmission lines, wherein one end of the switch portion, which is far away from the energy consumption portion, is connected to one of the direct current transmission lines, and one end of the energy consumption portion, which is far away from the switch portion, is connected to the other of the direct current transmission lines.

In some embodiments, the power system further comprises: an AC subsystem that receives power from the DC transmission line and converts to AC power. The ac subsystem may include a dc-ac conversion device.

In some embodiments, the power system further comprises: a power generation or conversion system configured to provide DC power to the DC link. In some embodiments, the power generation or conversion system comprises one of: a direct current power generation system; and an AC power generation system and an AC-DC conversion device connected between the AC power generation system and the DC transmission line. In some embodiments, the ac power generation system comprises a wind farm.

FIG. 5 shows a flow diagram of a method of consuming energy according to one embodiment of the present disclosure. Fig. 6 shows a specific example of the step of generating a control signal of the energy consuming method according to an embodiment of the present disclosure. Fig. 7 illustrates a schematic diagram of a control portion for an energy consumption system or an electric power system including the energy consumption system and a control process thereof according to one embodiment of the present disclosure. This is explained below with reference to fig. 5-7.

There is also provided, according to some embodiments of the present disclosure, a method of consuming energy of a power system, as shown in fig. 5, which may include the following steps.

In step 501: it is determined whether the voltage on the dc link exceeds a threshold. According to the energy consumption system (and the power system) disclosed by the invention, the direct current line voltage can be monitored in real time during the operation process of the system. When the direct current voltage exceeds a set threshold value, an energy consumption system (also called an unloading circuit) is triggered to work to consume surplus energy.

In step 503, in case the voltage on the dc link exceeds the threshold, a control signal for the switching legs of each switching module is generated based on the power difference between the active power on the dc link and the active power consumed by the ac subsystem.

For example, the difference in power that the dc unloading circuit should consume can be obtained by measuring the active power of the input dc line of the wind farm and the active power consumed by the receiving grid (ac side). The dc input power of the power generation side (or dc grid side) converter station (e.g. 103) may be denoted with Pin _ G and the ac side output power with Pout _ G, as shown in fig. 7. The difference between the two is the power difference which should be consumed by the direct current unloading circuit. The control signals for the switching legs of the respective switching modules can thus be generated on the basis of the power difference.

In some embodiments, the control signal may be generated based on the power difference and based on a comparison between the voltage on the dc link and a threshold, as shown in fig. 7, which will be described in more detail later.

In step 505, the switch branches of each switch module are controlled to be turned on based on the control signal, so that current passes through the energy consumption device to consume energy.

Optionally, the method may further include step 507, in which the switching branches of the respective switching modules are controlled to be turned off based on the control signal. For example, the control signal may be a pulse signal, and the pulse signal may have a duty ratio to control the switching branches of the respective switching modules to be turned on or off to consume surplus power as needed.

In some embodiments, as shown in fig. 6, generating control signals for the switching legs of each switching module includes the following steps.

In step 601, the power difference is scaled based on the parameter of each switch module and the per unit value of the power difference to obtain a scaled power difference. The per unit value may be the ratio of the power difference to the nominal transmission power of the system. The parameters of each switching module may include, for example, parameters of the power electronic switch such as voltage rating, current rating, maximum average current, switching frequency, and the like.

In step 603, the duty cycle of the control signal for the switching branch of each switching module is determined based on the scaled power difference and the comparison between the voltage on the dc link and the threshold.

In step 605, a pulse signal is generated based on the duty cycle as a control signal for the switching legs of each switching module.

In one embodiment, as shown in fig. 7, a control section 700 is also provided. The control part 700 may be configured to generate a control signal for the switching branch of each switching module based on the voltage on the dc transmission line to control the on of the switching branch of each switching module, so that current passes through the energy consuming device for energy consumption. It should be understood that the control portion may be provided in the energy consumption system; or may be provided in an electrical system including an energy consuming system, for example integrated with other control systems of the electrical system.

The control section 700 may comprise a power difference determination module 701 which receives a value Pin _ G of the dc input power and a value Pout _ G of the ac side output power of the power side (or dc network side) converter station (e.g. 103) to determine a power difference. The power determination module 701 may be implemented by, for example, an adder; however, the present disclosure is not limited thereto. Those skilled in the art will appreciate that a subtractor is essentially an adder with a negative coefficient.

The control section 700 may further include a scaling module 703. The scaling module is configured to scale the power difference. The scaling parameter of the scaling module may be determined by the per unit value of the power difference. Alternatively, the scaling parameters of the scaling module may be designed by a per unit value of the power difference and based on design values of the switching module (e.g., voltage rating, current rating, maximum average current, switching frequency, etc.), and so forth. For example, in some embodiments, the per unit value may be configured as a ratio of the power difference and the system rated transmission power.

In some embodiments, control 700 may further include a comparator 513 to compare the measured voltage Edc on the direct current transmission line (e.g., 107) to a reference voltage Edc _ ref to determine whether the voltage Edc on the direct current transmission line is higher than the reference voltage Edc _ ref. If the output of the comparator is 0, that is, the voltage of the direct current line is less than the reference voltage, the direct current energy consumption device is not started at this time. If the output of the comparator is 1, that is, the voltage of the direct current line is greater than the reference voltage, that is, the direct current line generates power surplus, the direct current energy consumption device is started to consume energy.

The control section 700 may further include a trigger module 705. The triggering module 705 may trigger (or activate) a related process for controlling or activating an energy consuming part (energy consuming device) according to the comparison result of the comparator 705. In some embodiments, the trigger module 705 may include a multiplier 705. Multiplier 705 multiplies the scaled power difference with the output of the comparator. If the output of the comparator is 0, the output of the multiplier is 0, that is, the energy consumption device is not started to consume energy. If the output of the comparator is 1, outputting the power difference of the proportional processing through a multiplier; in this case, the dc energy consuming device is appropriately activated for energy consumption by subsequent processing based on the power difference (and optionally other parameters, such as design values of the switch module, etc.).

In some embodiments, the control section 700 may further optionally include a clipping module 707 to clip the result of the scaling process. In the preceding stage (scaling module), the power difference has been converted into a ratio by a per unit value, which is based on the rated power, whereas in practical applications, it may happen that the wind farm output power exceeds its rated power for a short time. In this case, a value greater than 1 occurs in the ratio. It can therefore be limited between 0-1 by the clipping module to determine the duty cycle of the signal used to control the switching device. The duty ratio 709 of a signal for controlling the switching device is obtained through the amplitude limiting module, and the duty ratio is limited between 0 and 1.

The carrier signal may then be used to generate a pulse signal having a desired duty cycle 709 as said control signal for the switching branch of the switching module (or the switching device thereof). In some implementations, the carrier signal may be a frequency-tunable triangular carrier signal. In the embodiment shown in fig. 7, the control section 700 includes a comparator 711 to generate a pulse signal having a desired duty ratio using a triangular carrier signal whose frequency is adjustable using the comparator 711. Here, those skilled in the art will readily understand that the triangular carrier signal is a carrier signal having a triangular waveform, as shown in fig. 7.

In some embodiments, the bypass branch may be omitted in the switch module. For example, in the embodiment shown in fig. 8, the bypass branch is omitted from the switch module, as compared to the embodiment shown in fig. 4.

The inventors of the present application have also recognized that, in general, a failure of an IGBT of a power device is an open circuit, and a failure of an IGCT or IEGT of a power device is a short circuit. Therefore, when IGCT and IEGT are used for the switch branches, the bypass switch S can be omitted.

In some embodiments, the snubber branch may be omitted from the switch module. For example, in the embodiment shown in fig. 9, the snubber branch (RC snubber branch) is omitted in the switch module, compared to the embodiments shown in fig. 4 or 8.

In some embodiments, the snubber branch may be omitted from the switch module. For example, in contrast to the embodiment shown in fig. 4, in the embodiment shown in fig. 10, the reverse current protection branch (e.g., diode D in anti-parallel with switch T in fig. 8 and 9) may be omitted in the switch module.

Fig. 11 shows a schematic diagram of a dc energy consuming system according to one embodiment of the present disclosure. In this embodiment, all switch modules are divided into groups, e.g., i-groups, where SM₁₁-SM_1nIn one group, SM_i1-SM_inAre grouped. One or more metal oxide arresters MOV can be connected in parallel to each group of switches₁...MOV_i. In this embodiment, in addition to dissipating energy using the centralized energy dissipating resistor Ri, MOV may be used₁...MOV_iConsumes energy. For example, several levels may be set according to the power difference that needs to be absorbed, with the corresponding switches being switched in (i.e., on) or out (i.e., off) in groups, with access to the MOV₁...MOV_iTo dissipate energy. For example, when the power difference to be absorbed needs to be dissipated by an MOV1 in addition to the centralized dissipation resistor Ri, the first set of switches SM is switched out (i.e., turned off)₁₁-SM_1nSwitching in MOV in parallel with the first set of switches₁To consume energy.

FIG. 12 shows a schematic diagram of an energy consuming system according to another embodiment of the present disclosure. In this example, the switch module may further include a power consuming branch connected between the first node and the second node. In the example shown in fig. 12, the energy consuming branch may comprise an energy consuming device Rii and a power electronic switch TR connected in series with each other. The energy consuming branch is configured in parallel with the switching branch. In some implementations, the power electronic switch TR may be a thyristor. The energy dissipation device Rii can be an energy dissipation resistor. One or more dissipation resistors ri can be provided in each switch module. Thus, the dissipation resistance Rii is distributed.

In this example, the Ri lumped dissipation resistors are also connected in parallel with a bypass switch S. Whether Ri is switched in the circuit can be controlled by a bypass switch S.

According to the embodiment, the energy consumption can be shared by Ri centralized energy consumption resistors and Rii distributed energy consumption resistors. And one or more of the distributed energy consumption resistors Rii and/or the centralized energy consumption resistor Ri can be controlled to consume energy by controlling the power device T and the thyristor TR of each switch module according to the power difference to be absorbed.

According to the direct current energy consumption device of the embodiment of the disclosure, the switch part comprises at least one switch module which are connected in series with each other. According to some embodiments of the present disclosure, a parallel snubber circuit (e.g., a resistor-capacitor snubber circuit) is adopted in the switch module to slow the rising speed of the voltage of the switch device during turn-off and reduce the dynamic voltage difference.

According to some embodiments of the present disclosure, an arrester MOV is adopted in the switch module, which can limit the voltage values at two ends of the switch device, thereby effectively limiting overvoltage and ensuring voltage-sharing effect. Therefore, the safety of the switching device can be improved.

In addition, the voltage of each module can be controlled by the composite switch module comprising the MOV, so that the redundancy of the direct current energy consumption device is improved. According to the embodiment of the disclosure, even if a certain switch module or certain switch modules in the switch part have a fault, the system can still work normally.

According to the embodiment of the disclosure, dynamic and static voltage sharing of the switching device can be realized, and the technical problem of series voltage sharing is solved. In addition, according to the embodiment of the disclosure, an expensive high-power water cooling system is not needed, and the occupied area and the cost are low. In addition, the energy consumption system according to the embodiment of the disclosure is simple to control, high in reliability and easy to be incorporated into an existing power system.

Various embodiments of the present disclosure have been described above, but the above description is only exemplary and not exhaustive, and the present invention is not limited to the disclosed various embodiments. The various embodiments and features thereof disclosed herein may be combined in any combination without departing from the spirit and scope of the present invention. Many modifications and variations of this invention may be suggested to one of ordinary skill in the art in light of the teachings herein, and are to be included within the spirit and purview of this invention.

Claims

1. A direct current energy dissipation system, comprising:

an energy consuming part comprising an energy consuming device; and

with power consumption portion series connection's switch portion, switch portion includes at least one switch module, switch module includes:

a first node and a second node;

a switching branch and a snubber branch connected in parallel between the first and second nodes, wherein the switching branch comprises a power electronic switch and the snubber branch comprises at least a capacitor; and

a protection module configured to protect the power electronic switch from overvoltage and/or overcurrent.

2. The dc energy consuming system of claim 1, wherein the at least one switch module comprises a plurality of the switch modules connected in series with each other.

3. The dc energy consuming system of claim 1, wherein the snubber branch is configured to snubber the voltage across the switch on or in the switch branch and not pass dc current through the snubber branch.

4. The dc energy consuming system of claim 1, wherein:

an end of the switching section remote from the energy consuming section is adapted to be connected to a direct current transmission line, and

the energy consuming part is configured to receive power from the direct current transmission line via the switching part.

5. The dc energy consuming system of claim 1, wherein the protection module is connected in parallel with the switching leg between the first node and the second node.

6. The direct current energy consumption system of claim 1, wherein the protection module comprises a metal oxide arrester (MOV).

7. The dc energy consuming system of claim 2, wherein, in the plurality of switch modules, the second node of an upstream switch module is coupled to the first node of a downstream switch module immediately adjacent thereto.

8. The dc energy consuming system of claim 1, wherein:

the energy consuming device is a centralized resistive energy consuming device,

the energy consuming part is configured to be distant from the switching part so that heat generated from the energy consuming part does not affect the switching part.

9. The dc energy consuming system of any one of claims 1-8, wherein the power electronic switch comprises a fully-controlled power electronic switch.

10. The dc energy consuming system of any of claims 1-8, wherein the power electronic switch comprises any one or more of:

IGBT、IGET、IGCT。

11. the dc energy consuming system of any of claims 1-8, wherein each switch module further comprises:

a reverse current protection branch connected between the first node and the second node in anti-parallel with the switching branch to prevent reverse current from flowing through the switching branch.

12. The dc energy consuming system of any of claims 1-8, wherein each switch module further comprises:

a bypass branch in parallel with the switch branch, the bypass branch including a bypass switch,

the bypass branch is configured to pass current therethrough without passing through the switch branch when the bypass switch is turned on.

13. The DC energy consuming system according to any one of claims 1 to 8, wherein an end of the switching section remote from the energy consuming section is adapted to be connected to a high potential DC line of DC lines, an end of the energy consuming section remote from the switching section is adapted to be connected to a low potential DC line of the DC lines, the DC lines are adapted to be connected to an AC power system,

the direct current energy consumption system further comprises a control part, wherein the control part is configured to generate a control signal for the switch branch of each switch module based on the voltage on the direct current transmission line so as to control the switch branch of each switch module to be turned on, so that current can pass through the energy consumption device to consume energy.

14. The DC energy consuming system of any one of claims 1 and 3-8, wherein the at least one switch module comprises a plurality of the switch modules connected in series with each other,

the dc energy consuming system further comprises a further energy consuming device configured in parallel with one or more of the plurality of switch modules.

15. The direct current energy consumption system of claim 14, wherein the additional energy consumption device comprises a metal oxide arrester.

16. The DC energy consuming system of any one of claims 1-8, wherein the switch module further comprises an energy consuming branch connected between the first node and a second node,

the energy consumption branch comprises an energy consumption device and a power electronic switch which are connected in series with each other.

17. A direct current energy dissipation system, comprising:

an energy consuming part comprising an energy consuming device; and

a first node and a second node;

a switching leg connected between the first node and a second node, the switching leg including a power electronic switch;

a protection module configured to protect the power electronic switch from overvoltage and/or overcurrent; and

18. The dc energy consuming system of claim 17, wherein the at least one switch module comprises a plurality of the switch modules connected in series with each other.

19. The dc energy consuming system of claim 17, further comprising a snubber branch, wherein the snubber branch is configured to snubber a voltage across the switch branch or a switch in the switch branch and not pass dc current through the snubber branch.

20. The dc energy consuming system of claim 17, wherein:

21. The dc energy consuming system of claim 17, wherein the protection module is connected in parallel with the switching leg between the first node and the second node.

22. The direct current energy consumption system of claim 17, wherein the protection module comprises a metal oxide arrester (MOV).

23. The dc energy consuming system of claim 18, wherein, in the plurality of switch modules, the second node of an upstream switch module is coupled to the first node of a downstream switch module immediately adjacent thereto.

24. The dc energy consuming system of claim 17, wherein:

the energy consuming device is a centralized resistive energy consuming device,

25. The dc energy consuming system of any of claims 17-24, wherein the power electronic switch comprises a fully-controlled power electronic switch.

26. The dc energy consuming system of any of claims 17-24, wherein the power electronic switch comprises any one or more of:

IGBT、IGET、IGCT。

27. the dc energy consuming system of any of claims 17-24, wherein each switch module further comprises:

28. The dc energy consuming system of any of claims 17-24, wherein each switch module further comprises:

29. The DC energy consuming system of any one of claims 17 to 24, wherein an end of the switching section remote from the energy consuming section is adapted to be connected to a high potential DC link of DC links, an end of the energy consuming section remote from the switching section is adapted to be connected to a low potential DC link of the DC links, the DC links are adapted to be connected to an AC power system,

30. The DC energy consuming system of any one of claims 17 and 19-24, wherein the at least one switch module comprises a plurality of the switch modules connected in series with each other,

31. The direct current energy consumption system of claim 30, wherein the additional energy consumption device comprises a metal oxide arrester.

32. The DC energy consuming system of any one of claims 17-24, wherein the switch module further comprises an energy consuming branch connected between the first node and the second node,

33. An electrical power system, comprising:

a DC subsystem comprising a DC transmission line; and

the DC energy consuming system of any of claims 1 to 32, connected to the DC transmission line,

one end of the switch part, which is far away from the energy consumption part, is connected to a high-potential transmission line of the direct-current transmission lines, and one end of the energy consumption part, which is far away from the switch part, is connected to a low-potential transmission line of the direct-current transmission lines.

34. The power system of claim 33, further comprising:

an AC subsystem that receives power from the DC transmission line and converts it to AC power,

the alternating current subsystem comprises a direct current-alternating current conversion device.

35. The power system of claim 33, further comprising:

a power generation or conversion system configured to provide DC power to the DC link.

36. The power system of claim 35, wherein the power generation or conversion system comprises one of:

a direct current power generation system; and

the alternating current power generation system and the alternating current-direct current conversion device are connected between the alternating current power generation system and the direct current transmission line.

37. The power system of claim 36, wherein the ac power generation system comprises a wind farm.