A DC circuit breaker based on active control energy dissipation and its control method

Abstract

The present invention provides a DC circuit breaker based on active control energy consumption and a control method. The circuit breaker includes: a main current-carrying branch and an active energy consumption branch connected in parallel; the active energy consumption branch includes a first energy consumption branch, a second energy consumption branch, and an active control branch; the first energy consumption branch is connected in series with the active control branch; the active control branch is connected in parallel with the second energy consumption branch, and the active control branch is used to control whether the second energy consumption branch participates in energy consumption or not. The DC circuit breaker based on active control energy consumption and the control method of the present invention can meet the breaking requirements of the DC circuit breaker and reduce the voltage withstand level requirements of the main current-carrying branch by actively controlling the access devices of the energy consumption branch, thereby realizing a more economical and convenient DC circuit breaker.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and particularly relates to a DC circuit breaker based on active control energy consumption and a control method therefor. Background Art

[0002] In traditional solid-state DC circuit breakers, metal oxide varistors (MOVs) are generally connected in parallel across the circuit breaker as an energy-consuming branch to absorb the system fault energy after the power electronic devices are turned off. However, due to the material characteristics of MOVs, their residual voltage is usually significantly greater than their rated DC voltage, and the circuit breaker requires the rated DC voltage of the energy-consuming MOV branch to be greater than the DC bus voltage. This means that the power electronic devices need to withstand a voltage stress significantly greater than the DC bus voltage when turned off, resulting in a relatively large number of series-connected current-carrying devices and increasing the cost of the current-carrying devices and their heat dissipation devices. Summary of the Invention

[0003] In view of the above problems, the present invention proposes a solid-state DC circuit breaker based on active control energy consumption. By adding turn-off devices, the rated voltage of the energy-consuming MOV is reduced, thereby reducing the number of series-connected current-carrying power electronic devices and effectively reducing the cost and device complexity of the solid-state DC circuit breaker.

[0004] The present invention provides a DC circuit breaker based on active control energy consumption, comprising:

[0005] A main current-carrying branch and an active energy-consuming branch connected in parallel;

[0006] The active energy-consuming branch includes a first energy-consuming branch, a second energy-consuming branch, and an active control branch;

[0007] The first energy-consuming branch is connected in series with the active control branch;

[0008] The active control branch is connected in parallel with the second energy-consuming branch, and the active control branch is used to control whether the second energy-consuming branch participates in energy consumption or not.

[0009] Further, the main current-carrying branch includes a plurality of solid-state switch modules.

[0010] Further, the first energy-consuming branch includes an energy-consuming MOV module;

[0011] The second energy-consuming branch includes a protection MOV module.

[0012] Further,

[0013] The active control branch includes a plurality of active control modules that can be turned on or off;

[0014] The active control branch includes fully controlled power electronic devices.

[0015] Further,

[0016] The residual voltage of the first energy-consuming branch can satisfy being greater than the DC bus voltage;

[0017] The sum of the rated DC voltages of the first energy-consuming branch and the second energy-consuming branch can satisfy being greater than the DC bus voltage.

[0018] Further,

[0019] The withstand voltage value of the main current-carrying branch is greater than the residual voltage of the first energy-consuming branch;

[0020] The withstand voltage value of the active control branch is greater than the residual voltage of the second energy-consuming branch.

[0021] The present invention also provides a control method for a DC circuit breaker based on active control of energy consumption. The DC circuit breaker based on active control of energy consumption includes:

[0022] A main current-carrying branch and an active energy-consuming branch connected in parallel;

[0023] The active energy-consuming branch includes a first energy-consuming branch, a second energy-consuming branch, and an active control branch;

[0024] The first energy-consuming branch is connected in series with the active control branch;

[0025] The active control branch is connected in parallel with the second energy-consuming branch, and the active control branch is used to control whether the second energy-consuming branch participates in energy consumption or not;

[0026] The method includes:

[0027] When the main current-carrying branch is conducting, the main control branch is in a blocking state;

[0028] When the main current-carrying branch is turned off, the active control branch is turned on, and the current transfers from the main current-carrying branch to the active energy-consuming branch, so that the current flowing through the circuit breaker gradually decreases;

[0029] When the current of the active energy-consuming branch drops to the first specified current value, if the current flowing through the circuit breaker no longer decreases, then the active control branch is turned off, and the current transfers to the second energy-consuming branch. The voltage at the circuit breaker terminal is the sum of the voltages of the first energy-consuming branch and the second energy-consuming branch, and the sum of the voltages is greater than the DC bus voltage.

[0030] The present invention also provides a method for actively controlling the energy consumption of a DC circuit breaker. The DC circuit breaker includes a main current-carrying branch and an energy-consuming branch connected in parallel. The method includes:

[0031] In the first stage of the circuit breaker turning-off process, control the energy-consuming device connected to the energy-consuming branch such that: the breakdown voltage of the main current-carrying branch is greater than the terminal voltage of the energy-consuming branch, and the residual voltage of the energy-consuming branch is greater than the DC bus voltage;

[0032] In the second stage of the circuit breaker turning-off process, control the energy-consuming device connected to the energy-consuming branch such that: the value of the terminal voltage of the energy-consuming branch is greater than the DC bus voltage;

[0033] Wherein, the rated DC voltage of the energy-consuming device connected in the second stage is greater than the rated DC voltage of the energy-consuming device connected in the first stage.

[0034] Furthermore, in the first stage: perform the turning-off of the main current-carrying branch, control to connect the first energy-consuming branch to the energy-consuming branch, and transfer the current of the main current-carrying branch to the energy-consuming branch;

[0035] In the second stage: when it is determined that the current flowing through the circuit breaker no longer decreases, control to connect both the first energy-consuming branch and the second energy-consuming branch to the energy-consuming branch.

[0036] Furthermore, the first energy-consuming branch and the second energy-consuming branch are connected in series, and the connection of the second energy-consuming branch to the energy-consuming branch is controlled through an active control branch connected in parallel at both ends of the second energy-consuming branch.

[0037] A DC circuit breaker and control method based on active control of energy consumption according to the present invention can meet the turning-off requirements of the DC circuit breaker and reduce the requirement for the withstand voltage level of the main current-carrying branch by actively controlling the access branch (device) of the energy-consuming branch, thereby enabling a more economical and convenient DC circuit breaker.

[0038] Other features and advantages of the present invention will be described in the subsequent specification, and, in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structures pointed out in the specification, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following-described drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0040] Figure 1 Shows a schematic structural diagram of a DC circuit breaker based on active control of energy consumption according to an embodiment of the present invention;

[0041] Figure 2Shows the MOV volt-ampere characteristic curve according to an embodiment of the present invention. Detailed implementation manners

[0042] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0043] An embodiment of the present invention provides a DC circuit breaker based on active control energy consumption, specifically a solid-state DC circuit breaker based on active control energy consumption. As Figure 1 shown, the DC circuit breaker includes a main current-carrying branch and an energy-consuming branch connected in parallel. Among them, the main current-carrying branch and the active energy-consuming branch are connected in parallel, and the energy-consuming branch is an active energy-consuming branch.

[0044] The main current-carrying branch includes a plurality of series-connected solid-state switch modules, and the multiple solid-state switch modules are connected in series or in parallel or in a combination of series and parallel.

[0045] The active energy-consuming branch includes a first energy-consuming branch, a second energy-consuming branch and an active control branch. The first energy-consuming branch is connected in series with the active control branch; the active control branch is connected in parallel with the second energy-consuming branch, and the active control branch is used to control whether the second energy-consuming branch participates in energy consumption or not. The first energy-consuming branch always participates in energy consumption when the energy-consuming branch is conducting, and the second energy-consuming branch selectively participates in energy consumption according to the state of the active control branch.

[0046] The first energy-consuming branch includes an energy-consuming MOV module, and the energy-consuming MOV module includes an MOV. The second energy-consuming branch includes a protection MOV module, and the protection MOV module includes an MOV. The MOV is a metal oxide varistor.

[0047] The active control branch includes a plurality of active control modules, and the active control modules can be turned on or off.

[0048] Both the solid-state switch modules and the active control modules include fully-controlled power electronic devices. The fully-controlled power electronic devices can be insulated gate bipolar transistors (IGBTs), integrated gate-commutated thyristors (IGCTs), gate-injected enhanced transistors (IEGTs), gate turn-off thyristors (GTOs), etc., and the structure can adopt a unidirectional or bidirectional current-carrying structure. In some embodiments, the solid-state switch modules or the active control modules further include corresponding snubber circuits and protection circuits.

[0049] The parameter design of the DC circuit breaker is introduced below.

[0050] 1. The residual voltage of the first energy-consuming branch can satisfy being greater than the DC bus voltage. The residual voltage of the first energy-consuming branch is the residual voltage (sum) of the energy-consuming MOV module(s) in the first branch. The residual voltage of the energy-consuming MOV module (the module terminal voltage under the rated steep wave impulse current) is greater than the DC bus voltage and has a certain margin (such as 1.2 times the DC bus voltage); the rated DC voltage of the energy-consuming MOV module (the module terminal voltage when the leakage current is at the mA level) can be calculated according to the residual voltage ratio (the residual voltage ratio is usually about 1.6).

[0051] 2. The sum of the rated DC voltages of the first energy-consuming branch and the second energy-consuming branch can satisfy being greater than the DC bus voltage. Exemplarily, the sum of the rated DC voltages of the protection MOV module and the energy-consuming MOV module should be greater than the DC bus voltage and have a certain margin.

[0052] 3. Calculate the first specified current value Ith according to the volt-ampere characteristic of the energy-consuming MOV module. Ith is the current at both ends when the voltage across the first energy-consuming branch is equal to the DC bus voltage.

[0053] 4. The withstand voltage value of the main current-carrying branch is greater than the residual voltage of the first energy-consuming branch. Specifically, the total withstand voltage of the series solid-state switch module is greater than the residual voltage of the energy-consuming MOV module and has a certain margin to avoid breakdown when the solid-state switch module turns off;

[0054] The total withstand voltage of the main current-carrying branch should also be greater than the sum of the terminal voltages of the protection MOV and the energy-consuming MOV modules under the impact current of the magnitude of Ith to avoid breakdown when the active control module turns off.

[0055] 5. The withstand voltage value of the active control branch is greater than the residual voltage of the second energy-consuming branch. Specifically, the total withstand voltage of the active control module should be greater than the voltage of the protection MOV under the steep wave impulse current of the magnitude of Ith and have a certain margin to prevent breakdown when the active control module turns off.

[0056] Through the above parameter design, the number of series-connected solid-state switch modules in the main current-carrying branch can be reduced compared with the traditional topology where the energy-consuming MOV is directly connected in parallel with the main current-carrying branch, thereby reducing the cost of the solid-state DC circuit breaker and the complexity of the heat dissipation device.

[0057] The embodiment of the present invention also provides a control method for a DC circuit breaker based on active control energy consumption, which can cut off the fault current of the DC bus (the DC bus is the power grid line where the circuit breaker is connected) by controlling the DC circuit breaker based on active control energy consumption in any of the above embodiments.

[0058] The method includes: when the main current-carrying branch is conducting, the main control branch is in a blocking state; when the main current-carrying branch is turned off, the main control branch is turned on, and the current transfers from the main current-carrying branch to the active energy-consuming branch, causing the current flowing through the circuit breaker to gradually decrease; when the current in the active energy-consuming branch drops to a certain value Ith, according to the DC fault model, if the current flowing through the circuit breaker rises again, the active control branch is turned off, and the current transfers to the second energy-consuming branch. The voltage at the circuit breaker terminal is the sum of the voltages of the first energy-consuming branch and the second energy-consuming branch, and the sum of the voltages is greater than the DC bus voltage.

[0059] Specifically, it includes the following steps:

[0060] 1. When the solid-state DC circuit breaker is in the conducting state, the power electronic devices in the solid-state switch module are conducting, and the power electronic devices in the active control module are all in the blocking state.

[0061] 2. When the solid-state DC circuit breaker performs an opening operation, that is, when the devices in the solid-state switch module are turned off, the devices in the active control module are turned on (it can be turned on before turning off the solid-state switch module). The current quickly transfers from the main current-carrying branch to the active energy-consuming branch. At this time, the voltage at the circuit breaker terminal is approximately equal to the residual voltage of the energy-consuming MOV module, and this value is greater than the DC bus voltage, causing the current flowing through the circuit breaker to gradually decrease.

[0062] 3. When the current in the active energy-consuming branch drops to a certain value Ith, according to Figure 2 the MOV volt-ampere characteristic in, the voltage at the circuit breaker terminal drops to the DC bus voltage, and the current flowing through the circuit breaker no longer decreases. Specifically, according to the DC fault model, for an ideal short-circuit fault (the impedance at the short-circuit point is zero), when the voltage at the circuit breaker terminal is equal to the DC bus voltage, the voltage across the inductor in the fault loop is zero, and the rate of change of the fault current is zero. At this time, the fully-controlled power electronic devices in the active control module are turned off. The current will transfer to the protective MOV in parallel with it. After that, the voltage at the circuit breaker terminal is the sum of the voltage of the energy-consuming MOV module and the voltage of the protective MOV. And under the above device parameter design, the sum of the rated DC voltages of the first energy-consuming branch and the second energy-consuming branch can meet the requirement of being greater than the DC bus voltage. Therefore, the current flowing through the circuit breaker will continue to decrease to zero. Under the action of the active energy-consuming branch, the DC circuit breaker completes the opening.

[0063] The embodiment of the present invention also provides a method for actively controlling the energy consumption of a DC circuit breaker. The DC circuit breaker includes a main current-carrying branch and an energy-consuming branch connected in parallel. The method includes:

[0064] In the first stage during the circuit breaker turning-off process, control the energy-consuming devices connected to the energy-consuming branch to meet the following conditions: the breakdown voltage (i.e., the withstand voltage value) of the main current-carrying branch is greater than the voltage at the energy-consuming branch terminal, and the residual voltage of the energy-consuming branch is greater than the DC bus voltage;

[0065] In the second stage of the circuit breaker tripping process, the energy-consuming device connected to the energy-consuming branch is controlled to meet the following conditions: the terminal voltage of the energy-consuming branch is greater than the DC bus voltage; in terms of device parameter performance, the rated DC voltage of the energy-consuming branch is greater than the bus voltage of the branch.

[0066] Among them, the rated DC voltage of the energy-consuming device connected in the second stage is greater than the rated DC voltage of the energy-consuming device connected in the first stage. Specifically, the total rated DC voltage of all the energy-consuming devices connected in the second stage is greater than the rated DC voltage of all the energy-consuming devices connected in the first stage. Without loss of generality, among all the energy-consuming devices connected in the second stage, it includes all the energy-consuming devices connected in the first stage. That is, the energy-consuming devices connected in the first stage are a subset of the energy-consuming devices connected in the second stage.

[0067] The first stage and the second stage are two stages in the circuit breaker tripping process, and the first stage is before the second stage.

[0068] Specifically, the first stage is the main energy-consuming stage. In the first stage: the main current-carrying branch is tripped, and it is controlled to connect the first energy-consuming branch to the energy-consuming branch. The current of the main current-carrying branch is transferred to the energy-consuming branch, and energy is consumed through the first energy-consuming branch, so that the current flowing through the circuit breaker gradually decreases.

[0069] The second stage is the tail energy-consuming stage. In the second stage: when it is judged that the current flowing through the circuit breaker no longer decreases, it is controlled to connect both the first energy-consuming branch and the second energy-consuming branch to the energy-consuming branch, and energy is consumed through the first energy-consuming branch and the second energy-consuming branch. Under the energy-consuming effect, the DC circuit breaker completes the opening.

[0070] Among them, the first energy-consuming branch is in series with the second energy-consuming branch, and the second energy-consuming branch is controlled to be connected to the energy-consuming branch through the active control branch connected in parallel at both ends of the second energy-consuming branch.

[0071] By connecting the second energy-consuming branch in the second stage in the present invention, the energy-consuming devices of the energy-consuming branch are supplemented, so that in the second stage, the DC rated voltage of the energy-consuming branch can easily be greater than the bus DC voltage. For the first energy-consuming branch, it is not required that its rated DC voltage is greater than the bus voltage, thereby reducing the rated DC voltage of the energy-consuming devices of the first energy-consuming branch, and further reducing the voltage withstand requirement for the main current-carrying branch, and the series devices of the main current-carrying branch can be reduced. Among them, the rated DC voltage of the energy-consuming branch refers to the sum of the rated DC voltages of the energy-consuming devices of the energy-consuming branch.

[0072] Without loss of generality, the method for actively controlling the energy consumption of the DC circuit breaker in the embodiments of the present invention can be implemented by the DC circuit breaker based on active control of energy consumption in any embodiment of the present invention. However, it is not limited to the structure described by the DC circuit breaker based on active control of energy consumption.

[0073] Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A DC circuit breaker based on active control energy dissipation, characterized in that Comprising: A main current-carrying branch and an active energy-consuming branch connected in parallel; The main current-carrying branch includes a plurality of solid-state switch modules connected in series or in series-parallel; The active energy-consuming branch includes a first energy-consuming branch, a second energy-consuming branch, and an active control branch; The first energy-consuming branch is connected in series with the active control branch; The active control branch is connected in parallel with the second energy-consuming branch, and the active control branch is used to control whether the second energy-consuming branch participates in energy consumption or not; The residual voltage of the first energy-consuming branch is greater than the DC bus voltage; The sum of the rated DC voltages of the first energy-consuming branch and the second energy-consuming branch is greater than the DC bus voltage; The total withstand voltage of the main current-carrying branch is greater than the sum of the terminal voltages of the first energy-consuming branch and the second energy-consuming branch under the impact of the first specified current value; The withstand voltage value of the active control branch is greater than the residual voltage of the second energy-consuming branch.

2. The DC circuit breaker based on active control energy consumption according to claim 1, characterized in that The first energy-consuming branch includes an energy-consuming MOV module; The second energy-consuming branch includes a protective MOV module.

3. The DC circuit breaker based on active control energy consumption according to claim 1, characterized in that The active control branch includes a plurality of active control modules, and the active control modules can be turned on or off; The active control branch includes fully-controlled power electronic devices.

4. A control method for the DC circuit breaker according to any one of claims 1-3, characterized in that The method includes: When the main current-carrying branch is conducting, the main control branch is in a blocked state; When the main current-carrying branch is turned off, the active control branch is turned on, and the current transfers from the main current-carrying branch to the active energy-consuming branch, so that the current flowing through the circuit breaker gradually decreases; When the current of the active energy-consuming branch drops to the first specified current value, if the current flowing through the circuit breaker no longer decreases, the active control branch is turned off, and the current transfers to the second energy-consuming branch. The terminal voltage of the circuit breaker is the sum of the voltages of the first energy-consuming branch and the second energy-consuming branch, and the sum of the voltages is greater than the DC bus voltage.

5. A method for actively controlling the energy consumption of a DC circuit breaker, applicable to the DC circuit breaker described in any one of claims 1-3, characterized in that, The method includes: In the first stage during the circuit breaker turning-off process, control the energy-consuming devices connected to the energy-consuming branch to satisfy: the breakdown voltage of the main current-carrying branch is greater than the terminal voltage of the energy-consuming branch, and the residual voltage of the energy-consuming branch is greater than the DC bus voltage; In the second stage during the circuit breaker turning-off process, control the energy-consuming devices connected to the energy-consuming branch to satisfy: the terminal voltage value of the energy-consuming branch is greater than the DC bus voltage; Wherein, the rated DC voltage of the energy-consuming devices connected in the second stage is greater than the rated DC voltage of the energy-consuming devices connected in the first stage.

6. The method for actively controlling the energy consumption of a DC circuit breaker according to claim 5, characterized in that In the first stage: execute the turning-off of the main current-carrying branch, control to connect the first energy-consuming branch to the energy-consuming branch, and the current of the main current-carrying branch transfers to the energy-consuming branch; In the second stage: when it is judged that the current flowing through the circuit breaker no longer decreases, control to connect both the first energy-consuming branch and the second energy-consuming branch to the energy-consuming branch.

7. The method for actively controlling the energy consumption of a DC circuit breaker according to claim 6, characterized in that The first energy-consuming branch is connected in series with the second energy-consuming branch, and the second energy-consuming branch is controlled to be connected to the energy-consuming branch through an active control branch connected in parallel across the two ends of the second energy-consuming branch.

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