CN109800381A - The direct-current short circuit current calculation method and system of modularization multi-level converter - Google Patents
The direct-current short circuit current calculation method and system of modularization multi-level converter Download PDFInfo
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Abstract
The invention discloses the direct-current short circuit current calculation methods and system of a kind of modularization multi-level converter, wherein this method comprises: obtaining faulty circuit in the DC current and DC voltage of fault moment；Multiple bridge arm reference voltages and the DC reference voltage of faulty circuit are obtained to calculate HVDC Modulation ratio；The time-varying parameter that multiple circuit parameters are obtained to calculate the preset parameter of faulty circuit, according to the preset parameter of faulty circuit and HVDC Modulation than calculating faulty circuit；The state of faulty circuit is judged than the time-varying parameter of the, preset parameter of faulty circuit and faulty circuit according to DC current, DC voltage, HVDC Modulation, and calculates the direct-current short circuit electric current of faulty circuit.The influence of converter Control behavior can be considered in this method, embodies faulty circuit structure with the change of converter Control Behavioral change, and correspondingly provide the exact expression of direct-current short circuit electric current.
Description
Technical field
The present invention relates to high-voltage large-capacity power electronics inverter analysis technical field, in particular to how electric a kind of modularization is
The direct-current short circuit current calculation method and system of flat inverter.
Background technique
MMC (Modular Multilevel Converter, modularization multi-level converter) belongs to voltage source type electric power
Electronic inverter can be steadily based on the full control power electronic devices such as insulated gate bipolar transistor and pulse modulation technology
Control active power and reactive power are transmitted between ac and dc systems.Consideration converter Control behavior representative at present
MMC direct-current short circuit calculation method mainly includes three kinds.The first considers that inverter has carried out locking control after DC Line Fault generation
System, the pulse of all submodules are blocked, and submodule capacitor discharge process is completely blocked, and direct-current short circuit circuit has become three
Phase uncontrollable rectifier circuit, direct-current short circuit electric current is mainly generated by alternating short-circuit current by freewheeling diode, based on not controlling
Rectification correlation theory can be derived by the analytical expression of direct-current short circuit electric current.Second of consideration inverter is sent out in DC Line Fault
Bypass Control is carried out after life, all submodules are bypassed, and DC Line Fault is converted for three-phase alternating current short trouble, are avoided
The uncontrollable rectifier effect of freewheeling diode, direct-current short circuit electric current can decline naturally due to losing DC Line Fault voltage source
Subtract, the analytical expression of direct-current short circuit electric current can be derived by according to single order OSCILLATORY CIRCUIT ANALYSIS theory.The third consideration is changed
Stream device run without interruption after DC Line Fault generation but is not actively engaged in direct current protecting, is only forced to bear short circuit current,
Since converter Control still uses steady-state algorithm, the control of submodule capacitor switching has similar place with charge and discharge process with stable state,
The analytical expression of direct-current short circuit electric current can be derived by based on order Oscillating Theory of Circuit Analysis.Above-mentioned three kinds of calculation methods
Although more accurately direct-current short circuit electric current can be provided to calculate as a result, still both for a certain specific controlling behavior,
The case where various control behavior can not be generally generalized to.However, controlling behavior is more when MMC is actively engaged in direct current protecting
For complexity, for example, can active limiting short-circuit current the rate of climb etc..Therefore, existing calculation method still cannot be examined uniformly
Consider the accurate calculation method that converter Control behavior provides direct-current short circuit electric current.
Summary of the invention
The present invention is directed to solve at least some of the technical problems in related technologies.
For this purpose, an object of the present invention is to provide a kind of calculating of the direct-current short circuit electric current of modularization multi-level converter
The influence of converter Control behavior can be considered in method, this method, embodies faulty circuit structure as converter Control behavior becomes
The change of change, and correspondingly provide the exact expression of direct-current short circuit electric current.
It is another object of the present invention to the direct-current short circuit electric currents for proposing a kind of modularization multi-level converter to calculate system
System.
In order to achieve the above objectives, one aspect of the present invention embodiment propose a kind of modularization multi-level converter direct current it is short
Road current calculation method, comprising: obtain faulty circuit in the DC current and DC voltage of fault moment；Obtain the failure electricity
Multiple bridge arm reference voltages and DC reference voltage on road calculate HVDC Modulation ratio；It is described to calculate to obtain multiple circuit parameters
The preset parameter of faulty circuit, according to the preset parameter of the faulty circuit and the HVDC Modulation than calculating the faulty circuit
Time-varying parameter；According to the DC current, the DC voltage, the HVDC Modulation than, the faulty circuit fixed ginseng
Several and the faulty circuit time-varying parameter judges the state of the faulty circuit, and calculates the direct-current short circuit of the faulty circuit
Electric current.
The direct-current short circuit current calculation method of the modularization multi-level converter of the embodiment of the present invention, by introducing direct current tune
The different controlling behaviors for integrating and embodying inverter during DC Line Fault are made than parameter, according to HVDC Modulation ratio and fault loop
The relationship of parameter judges the state of fault loop, correspondingly provides the calculation method of direct-current short circuit electric current.
In addition, the direct-current short circuit current calculation method of modularization multi-level converter according to the above embodiment of the present invention is also
It can have following additional technical characteristic:
Further, in one embodiment of the invention, the calculation formula of the HVDC Modulation ratio D are as follows:
Wherein, D is HVDC Modulation ratio, uap *For bridge arm reference voltage in a phase, uan *For a phase lower bridge arm reference voltage, ubp *
For bridge arm reference voltage in b phase, ubn *For b phase lower bridge arm reference voltage, ucp *For bridge arm reference voltage in c phase, ucn *For under c phase
Bridge arm reference voltage, Udc *For DC reference voltage.
Further, in one embodiment of the invention, described to obtain multiple circuit parameters to calculate the failure electricity
The preset parameter on road, specifically includes:
The preset parameter of the faulty circuit includes: equivalent reactance Le, equivalent resistance ReWith equivalent capacity Ce, calculation formula
Are as follows:
Wherein, LeFor equivalent reactance, ReFor equivalent resistance, CeFor equivalent capacity, N indicates bridge arm submodule number, CdIt indicates
The capacitor of each submodule, LsIndicate bridge arm inductance, LdcIndicate DC line inductance, RsIndicate arm resistance, RfIndicate failure electricity
Resistance.
Further, in one embodiment of the invention, the preset parameter according to the faulty circuit and described
Time-varying parameter of the HVDC Modulation than calculating the faulty circuit, specifically includes:
The time-varying parameter of the faulty circuit includes: attenuation coefficient δ, resonance angular frequency ω0, oscillation angular frequencyrAnd oscillation
Angle γ,
Calculation formula are as follows:
Wherein, δ is attenuation coefficient, ω0For resonance angular frequency, ωrTo vibrate angular frequency, γ is hunting angle, and D is direct current tune
Ratio processed.
Further, in one embodiment of the invention, described according to the DC current, the DC voltage, institute
The time-varying parameter that HVDC Modulation is stated than, the preset parameter of the faulty circuit and the faulty circuit judges the faulty circuit
State, and the direct-current short circuit electric current of the faulty circuit is calculated, it specifically includes:
WhenWhen, the faulty circuit is in underdamping state, the direct-current short circuit electric current IdcMeter
Calculate formula are as follows:
Idc(t)=Ae-δtsin(ωrt+β)
Wherein, Idc0For DC current, Udc0For DC voltage；
WhenWhen, the faulty circuit is in Critical damping state, the direct-current short circuit electric current Idc's
Calculation formula are as follows:
Idc(t)=(A3+A4t)e-δt
WhenWhen, the faulty circuit is in overdamping state, it is specifically divided into:
As D > 0, the faulty circuit is in overdamp second order loop state, direct-current short circuit electric current IdcCalculation formula
Are as follows:
Wherein, p1For p1=-δ+ωr, p2For p2=-δ-ωr；
As D=0, the faulty circuit is in overdamp single order loop state, the direct-current short circuit electric current IdcCalculating
Formula are as follows:
Idc(t)=Idc0e-2δt。
In order to achieve the above objectives, another aspect of the present invention embodiment proposes a kind of direct current of modularization multi-level converter
Calculation of short-circuit current system, comprising:
First obtains module, for obtaining faulty circuit in the DC current and DC voltage of fault moment；
Second obtains module, based on multiple bridge arm reference voltages and DC reference voltage by obtaining the faulty circuit come
Calculate HVDC Modulation ratio；
Third obtains module, the preset parameter of the faulty circuit is calculated for obtaining multiple circuit parameters, according to institute
State the time-varying parameter of preset parameter and the HVDC Modulation than calculating the faulty circuit of faulty circuit；
Computing module, for according to the DC current, the DC voltage, HVDC Modulation ratio, failure electricity
The preset parameter on road and the time-varying parameter of the faulty circuit judge the state of the faulty circuit, and calculate the faulty circuit
Direct-current short circuit electric current.
The direct-current short circuit electric current computing system of the modularization multi-level converter of the embodiment of the present invention, by introducing direct current tune
The different controlling behaviors for integrating and embodying inverter during DC Line Fault are made than parameter, according to HVDC Modulation ratio and fault loop
The relationship of parameter judges the state of fault loop, correspondingly provides the calculation method of direct-current short circuit electric current.
In addition, the direct-current short circuit electric current computing system of modularization multi-level converter according to the above embodiment of the present invention is also
It can have following additional technical characteristic:
Further, in one embodiment of the invention, the calculation formula of the HVDC Modulation ratio D are as follows:
Wherein, D is HVDC Modulation ratio, uap *For bridge arm reference voltage in a phase, uan *For a phase lower bridge arm reference voltage, ubp *
For bridge arm reference voltage in b phase, ubn *For b phase lower bridge arm reference voltage, ucp *For bridge arm reference voltage in c phase, ucn *For under c phase
Bridge arm reference voltage, Udc *For DC reference voltage.
Further, in one embodiment of the invention, described to obtain multiple circuit parameters to calculate the failure electricity
The preset parameter on road, specifically includes:
The preset parameter of the faulty circuit includes: equivalent reactance Le, equivalent resistance ReWith equivalent capacity Ce, calculation formula
Are as follows:
Wherein, LeFor equivalent reactance, ReFor equivalent resistance, CeFor equivalent capacity, N indicates bridge arm submodule number, CdIt indicates
The capacitor of each submodule, LsIndicate bridge arm inductance, LdcIndicate DC line inductance, RsIndicate arm resistance, RfIndicate failure electricity
Resistance.
Further, in one embodiment of the invention, the preset parameter according to the faulty circuit and described
Time-varying parameter of the HVDC Modulation than calculating the faulty circuit, specifically includes:
The time-varying parameter of the faulty circuit includes: attenuation coefficient δ, resonance angular frequency ω0, oscillation angular frequencyrAnd oscillation
Angle γ,
Calculation formula are as follows:
Wherein, δ is attenuation coefficient, ω0For resonance angular frequency, ωrTo vibrate angular frequency, γ is hunting angle, and D is direct current tune
Ratio processed.
Further, in one embodiment of the invention, the computing module, is specifically used for,
WhenWhen, the faulty circuit is in underdamping state, the direct-current short circuit electric current IdcMeter
Calculate formula are as follows:
Idc(t)=Ae-δtsin(ωrt+β)
Wherein, Idc0For DC current, Udc0For DC voltage；
WhenWhen, the faulty circuit is in Critical damping state, the direct-current short circuit electric current Idc's
Calculation formula are as follows:
Idc(t)=(A3+A4t)e-δt
WhenWhen, the faulty circuit is in overdamping state, it is specifically divided into:
As D > 0, the faulty circuit is in overdamp second order loop state, direct-current short circuit electric current IdcCalculation formula
Are as follows:
Wherein, p1For p1=-δ+ωr, p2For p2=-δ-ωr；
As D=0, the faulty circuit is in overdamp single order loop state, the direct-current short circuit electric current IdcCalculating
Formula are as follows:
Idc(t)=Idc0e-2δt。
The additional aspect of the present invention and advantage will be set forth in part in the description, and will partially become from the following description
Obviously, or practice through the invention is recognized.
Detailed description of the invention
Above-mentioned and/or additional aspect and advantage of the invention will become from the following description of the accompanying drawings of embodiments
Obviously and it is readily appreciated that, in which:
Fig. 1 is the circuit diagram according to the MMC of one embodiment of the invention；
Fig. 2 is the direct-current short circuit current calculation method stream according to the modularization multi-level converter of one embodiment of the invention
Cheng Tu；
Fig. 3 is the direct-current short circuit current calculation method according to the modularization multi-level converter of another embodiment of the present invention
Flow chart；
Fig. 4 is the direct-current short circuit electric current computing system knot according to the modularization multi-level converter of one embodiment of the invention
Structure schematic diagram.
Specific embodiment
The embodiment of the present invention is described below in detail, examples of the embodiments are shown in the accompanying drawings, wherein from beginning to end
Same or similar label indicates same or similar element or element with the same or similar functions.Below with reference to attached
The embodiment of figure description is exemplary, it is intended to is used to explain the present invention, and is not considered as limiting the invention.
MMC (Modular Multilevel Converter, modularization multi-level converter) belongs to voltage source type electric power
Electronic inverter can be steadily based on the full control power electronic devices such as insulated gate bipolar transistor and pulse modulation technology
Control active power and reactive power are transmitted between ac and dc systems.The circuit theory of MMC is as shown in Figure 1, MMC includes a, b, c
Three phase elements, each phase element include two bridge arms, i.e., upper bridge arm and lower bridge arm, a total of six bridge arm.Three phase elements are simultaneously
It is associated between direct-flow positive pole and direct current cathode, the upper bridge arm of three phase elements and the intermediate point of lower bridge arm couple three-phase alternating current system
System.Each bridge arm is composed in series by N number of submodule.Each submodule is by two insulated gate bipolar transistor S1、S2, two afterflows
Diode D1、D2An and DC capacitor CdIt constitutes.MMC has many technical advantages, such as modular structure, easily reaches
Voltage levels；The working method of more level is conducive to promote efficiency of transmission；The output voltage waveforms of high quality do not need to install
Alternating current filter etc., makes it play a significant role in DC grid, in scenes such as regional power grid interconnection, renewable energy accesses
Under it is in widespread attention.
Direct-current short circuit failure is the critical issue that MMC safe and reliable operation needs to solve.Due to the direct current system of DC grid
System impedance very little, after direct-current short circuit occurs, direct-current short circuit electric current has rises to high horizontal feature in a very short period of time.
Breakdown judge and fault clearance can rapidly be realized by not requiring nothing more than direct current protecting, and require the related member of the primary equipment of MMC
Part can bear direct-current short circuit current stress without being burned out during troubleshooting.Direct-current short circuit electric current is quantitatively calculated, is
The basis of direct current protecting conceptual design and MMC primary equipment type selecting.Further, since MMC itself has very strong current control energy
Power, the direct current protecting for having MMC to be actively engaged in have become the new technique route that DC grid solves direct-current short circuit failure.So
And controlling behavior of the MMC during direct-current short circuit failure would necessarily affect direct-current short circuit current characteristics, so direct-current short circuit is electric
The calculating of stream has to the controlling behavior in view of MMC.Therefore, the MMC direct-current short circuit electricity for considering converter Control behavior is established
Flow calculation methodologies, the direct-current short circuit current values being accurately given under the influence of different converter Controls not only can be direct current
Protection scheme design and primary equipment type selecting provide utility, and the Novel DC protection technique being actively engaged in for MMC mentions
Theory support is supplied.
The direct-current short circuit electricity of the modularization multi-level converter proposed according to embodiments of the present invention is described with reference to the accompanying drawings
Flow calculation methodologies and system.
The direct-current short circuit of the modularization multi-level converter proposed according to embodiments of the present invention is described with reference to the accompanying drawings first
Current calculation method.
Fig. 2 is the direct-current short circuit current calculation method stream according to the modularization multi-level converter of one embodiment of the invention
Cheng Tu.
As shown in Fig. 2, the direct-current short circuit current calculation method the following steps are included:
In step s101, faulty circuit is obtained in the latch DC current of fault moment and latches DC voltage.
Specifically, at the time of circuit malfunctions, the DC current I of latch fault circuitdc0With DC voltage Udc0, make
For fault moment initial value.
In step s 102, multiple bridge arm reference voltages and the DC reference voltage of faulty circuit are obtained to calculate direct current tune
Ratio processed.
Specifically, in the present embodiment, six bridge arm reference voltage u are obtainedap *、uan *、ubp *、ubn *、ucp *、ucn *And direct current
Reference voltage Udc *, calculate HVDC Modulation ratio D, calculation formula are as follows:
Wherein, D is HVDC Modulation ratio, uap *For bridge arm reference voltage in a phase, uan *For a phase lower bridge arm reference voltage, ubp *
For bridge arm reference voltage in b phase, ubn *For b phase lower bridge arm reference voltage, ucp *For bridge arm reference voltage in c phase, ucn *For under c phase
Bridge arm reference voltage, Udc *For DC reference voltage.
In step s 103, multiple circuit parameters are obtained to calculate the preset parameter of faulty circuit, according to faulty circuit
The time-varying parameter of preset parameter and HVDC Modulation than calculating faulty circuit.
Further, the preset parameter of faulty circuit includes: equivalent reactance Le, equivalent resistance ReWith equivalent capacity Ce。
Specifically, multiple circuit parameters are obtained, such as circuit bridge arm submodule number N, the capacitor C of each submoduled, bridge
Arm inductance Ls, DC line inductance Ldc, arm resistance RsWith fault resstance RfDeng passing through above-mentioned parameter and calculate faulty circuit and consolidate
Parameter is determined, such as equivalent reactance Le, equivalent resistance ReWith equivalent capacity Ce。
Wherein, calculation formula are as follows:
Wherein, LeFor equivalent reactance, ReFor equivalent resistance, CeFor equivalent capacity, N indicates bridge arm submodule number, CdIt indicates
The capacitor of each submodule, LsIndicate bridge arm inductance, LdcIndicate DC line inductance, RsIndicate arm resistance, RfIndicate failure electricity
Resistance.
After calculating multiple preset parameters of faulty circuit, according to the preset parameter of faulty circuit and HVDC Modulation D ratio
Calculate the time-varying parameter of faulty circuit.
Wherein, the time-varying parameter of faulty circuit includes: attenuation coefficient δ, resonance angular frequency ω0, oscillation angular frequencyrAnd vibration
Swing angle γ, calculation formula are as follows:
Wherein, δ is attenuation coefficient, ω0For resonance angular frequency, ωrTo vibrate angular frequency, γ is hunting angle, and D is direct current tune
Ratio processed.
In step S104, according to latch DC current, latch DC voltage, HVDC Modulation than, faulty circuit fixation
The time-varying parameter of parameter and faulty circuit judges the state of faulty circuit, and calculates the direct-current short circuit electric current of faulty circuit.
It is to be understood that judging the shape of faulty circuit according to calculated parameter after calculating above-mentioned multiple parameters
State, and direct-current short circuit electric current is calculated, detailed process is as follows:
(1) whenWhen, illustrate that faulty circuit is in underdamping state, direct-current short circuit electric current IdcMeter
Calculate formula are as follows:
Idc(t)=Ae-δtsin(ωrt+β)
Wherein, the calculation formula of parameter A and β are as follows:
Wherein, Idc0For DC current, Udc0For DC voltage, the initial value deposited in the event of a failure by circuit.
(2) whenWhen, illustrate that faulty circuit is in Critical damping state, direct-current short circuit electric current Idc's
Calculation formula are as follows:
Idc(t)=(A3+A4t)e-δt
Wherein, parameter A3And A4Calculation formula are as follows:
(3) whenWhen, illustrate that faulty circuit is in overdamping state, wherein according to HVDC Modulation ratio
D can be divided into two kinds of situations:
(3-1) as D > 0, faulty circuit is in overdamp second order loop state, direct-current short circuit electric current IdcCalculation formula
Are as follows:
Wherein, p1For p1=-δ+ωr, p2For p2=-δ-ωr；
Parameter A1And A2Calculation formula are as follows:
(3-2) illustrates that faulty circuit is in overdamp single order loop state, direct-current short circuit electric current I as D=0dcCalculating
Formula are as follows:
Idc(t)=Idc0e-2δt。
As shown in figure 3, illustrating the overall flow of direct-current short circuit current calculation method, inverter control can be uniformly considered
The influence of behavior processed can embody faulty circuit structure with the change of converter Control Behavioral change, and correspondingly provide straight
The exact expression of flow short-circuit electric current.Not only utility can be provided for direct current protecting conceptual design and primary equipment type selecting,
And the Novel DC protection technique being actively engaged in for MMC provides theory support.
The direct-current short circuit current calculation method of the modularization multi-level converter proposed according to embodiments of the present invention, by drawing
Enter HVDC Modulation than parameter to integrate the different controlling behaviors for embodying inverter during DC Line Fault, according to HVDC Modulation ratio with
The relationship of fault loop parameter judges the state of fault loop, correspondingly provides the calculation method of direct-current short circuit electric current.
Referring next to the direct-current short circuit electricity for the modularization multi-level converter that attached drawing description proposes according to embodiments of the present invention
Stream calculation system.
Fig. 4 is the direct-current short circuit electric current computing system knot according to the modularization multi-level converter of one embodiment of the invention
Structure schematic diagram.
As shown in figure 4, the direct-current short circuit electric current computing system include: the first acquisition module 100, first obtain module 200,
First obtains module 300 and computing module 400.
Wherein, the first acquisition module 100 is for obtaining faulty circuit in the DC current and DC voltage of fault moment.
Second acquisition module 200 is used to obtain multiple bridge arm reference voltages and the DC reference voltage of faulty circuit to calculate
HVDC Modulation ratio.
Third obtains module 300 for obtaining multiple circuit parameters to calculate the preset parameter of faulty circuit, according to failure
Time-varying parameter of the preset parameter and HVDC Modulation of circuit than calculating faulty circuit.
Computing module 400 be used for according to DC current, DC voltage, HVDC Modulation than, faulty circuit preset parameter and
The time-varying parameter of faulty circuit judges the state of faulty circuit, and calculates the direct-current short circuit electric current of faulty circuit.
The direct-current short circuit electric current computing system, it may be considered that the influence of converter Control behavior embodies faulty circuit structure
With the change of converter Control Behavioral change, and correspondingly provide the exact expression of direct-current short circuit electric current.
Further, in one embodiment of the invention, the calculation formula of HVDC Modulation ratio D are as follows:
Wherein, D is HVDC Modulation ratio, uap *For bridge arm reference voltage in a phase, uan *For a phase lower bridge arm reference voltage, ubp *
For bridge arm reference voltage in b phase, ubn *For b phase lower bridge arm reference voltage, ucp *For bridge arm reference voltage in c phase, ucn *For under c phase
Bridge arm reference voltage, Udc *For DC reference voltage.
Further, in one embodiment of the invention, multiple circuit parameters are obtained to calculate the fixation of faulty circuit
Parameter specifically includes:
The preset parameter of faulty circuit includes: equivalent reactance Le, equivalent resistance ReWith equivalent capacity Ce, calculation formula are as follows:
Wherein, LeFor equivalent reactance, ReFor equivalent resistance, CeFor equivalent capacity, N indicates bridge arm submodule number, CdIt indicates
The capacitor of each submodule, LsIndicate bridge arm inductance, LdcIndicate DC line inductance, RsIndicate arm resistance, RfIndicate failure electricity
Resistance.
Further, in one embodiment of the invention, according to the preset parameter of faulty circuit and HVDC Modulation than meter
The time-varying parameter for calculating faulty circuit, specifically includes:
The time-varying parameter of faulty circuit includes: attenuation coefficient δ, resonance angular frequency ω0, oscillation angular frequencyrAnd hunting angle
γ,
Calculation formula are as follows:
Wherein, δ is attenuation coefficient, ω0For resonance angular frequency, ωrTo vibrate angular frequency, γ is hunting angle, and D is direct current tune
Ratio processed.
Further, in one embodiment of the invention, computing module is specifically used for,
WhenWhen, faulty circuit is in underdamping state, direct-current short circuit electric current IdcCalculation formula
Are as follows:
Idc(t)=Ae-δtsin(ωrt+β)
Wherein, Idc0For DC current, Udc0For DC voltage；
WhenWhen, faulty circuit is in Critical damping state, direct-current short circuit electric current IdcCalculation formula
Are as follows:
Idc(t)=(A3+A4t)e-δt
WhenWhen, faulty circuit is in overdamping state, it is specifically divided into:
As D > 0, faulty circuit is in overdamp second order loop state, direct-current short circuit electric current IdcCalculation formula are as follows:
Wherein, p1For p1=-δ+ωr, p2For p2=-δ-ωr；
As D=0, faulty circuit is in overdamp single order loop state, direct-current short circuit electric current IdcCalculation formula are as follows:
Idc(t)=Idc0e-2δt。
It should be noted that the solution of the aforementioned direct-current short circuit current calculation method embodiment to modularization multi-level converter
The system that explanation is also applied for the embodiment is released, details are not described herein again.
The direct-current short circuit electric current computing system of the modularization multi-level converter proposed according to embodiments of the present invention, by drawing
Enter HVDC Modulation than parameter to integrate the different controlling behaviors for embodying inverter during DC Line Fault, according to HVDC Modulation ratio with
The relationship of fault loop parameter judges the state of fault loop, correspondingly provides the calculation method of direct-current short circuit electric current.
In addition, term " first ", " second " are used for descriptive purposes only and cannot be understood as indicating or suggesting relative importance
Or implicitly indicate the quantity of indicated technical characteristic.Define " first " as a result, the feature of " second " can be expressed or
Implicitly include at least one this feature.In the description of the present invention, the meaning of " plurality " is at least two, such as two, three
It is a etc., unless otherwise specifically defined.
In the description of this specification, reference term " one embodiment ", " some embodiments ", " example ", " specifically show
The description of example " or " some examples " etc. means specific features, structure, material or spy described in conjunction with this embodiment or example
Point is included at least one embodiment or example of the invention.In the present specification, schematic expression of the above terms are not
It must be directed to identical embodiment or example.Moreover, particular features, structures, materials, or characteristics described can be in office
It can be combined in any suitable manner in one or more embodiment or examples.In addition, without conflicting with each other, the skill of this field
Art personnel can tie the feature of different embodiments or examples described in this specification and different embodiments or examples
It closes and combines.
Although the embodiments of the present invention has been shown and described above, it is to be understood that above-described embodiment is example
Property, it is not considered as limiting the invention, those skilled in the art within the scope of the invention can be to above-mentioned
Embodiment is changed, modifies, replacement and variant.
Claims (10)
1. a kind of direct-current short circuit current calculation method of modularization multi-level converter, which comprises the following steps:
Faulty circuit is obtained in the DC current and DC voltage of fault moment；
Multiple bridge arm reference voltages and the DC reference voltage of the faulty circuit are obtained to calculate HVDC Modulation ratio；
Multiple circuit parameters are obtained to calculate the preset parameter of the faulty circuit, according to the preset parameter of the faulty circuit and
Time-varying parameter of the HVDC Modulation than calculating the faulty circuit；
According to the DC current, the DC voltage, the HVDC Modulation than the preset parameter of the, faulty circuit and described
The time-varying parameter of faulty circuit judges the state of the faulty circuit, and calculates the direct-current short circuit electric current of the faulty circuit.
2. the method according to claim 1, wherein the calculation formula of HVDC Modulation ratio D are as follows:
Wherein, D is HVDC Modulation ratio, uap *For bridge arm reference voltage in a phase, uan *For a phase lower bridge arm reference voltage, ubp *For b phase
Upper bridge arm reference voltage, ubn *For b phase lower bridge arm reference voltage, ucp *For bridge arm reference voltage in c phase, ucn *For c phase lower bridge arm ginseng
Examine voltage, Udc *For DC reference voltage.
3. the method according to claim 1, wherein described obtain multiple circuit parameters to calculate the failure electricity
The preset parameter on road, specifically includes:
The preset parameter of the faulty circuit includes: equivalent reactance Le, equivalent resistance ReWith equivalent capacity Ce, calculation formula are as follows:
Wherein, LeFor equivalent reactance, ReFor equivalent resistance, CeFor equivalent capacity, N indicates bridge arm submodule number, CdIndicate each
The capacitor of submodule, LsIndicate bridge arm inductance, LdcIndicate DC line inductance, RsIndicate arm resistance, RfIndicate fault resstance.
4. according to the method described in claim 3, it is characterized in that, the preset parameter according to the faulty circuit and described
Time-varying parameter of the HVDC Modulation than calculating the faulty circuit, specifically includes:
The time-varying parameter of the faulty circuit includes: attenuation coefficient δ, resonance angular frequency ω0, oscillation angular frequencyrAnd hunting angle
γ,
Calculation formula are as follows:
Wherein, δ is attenuation coefficient, ω0For resonance angular frequency, ωrTo vibrate angular frequency, γ is hunting angle, and D is HVDC Modulation ratio.
5. according to the method described in claim 4, it is characterized in that, described according to the DC current, the DC voltage, institute
The time-varying parameter that HVDC Modulation is stated than, the preset parameter of the faulty circuit and the faulty circuit judges the faulty circuit
State, and the direct-current short circuit electric current of the faulty circuit is calculated, it specifically includes:
WhenWhen, the faulty circuit is in underdamping state, the direct-current short circuit electric current IdcCalculating it is public
Formula are as follows:
Idc(t)=Ae-δtsin(ωrt+β)
Wherein, Idc0For DC current, Udc0For DC voltage；
WhenWhen, the faulty circuit is in Critical damping state, the direct-current short circuit electric current IdcCalculating
Formula are as follows:
Idc(t)=(A3+A4t)e-δt
WhenWhen, the faulty circuit is in overdamping state, it is specifically divided into:
As D > 0, the faulty circuit is in overdamp second order loop state, direct-current short circuit electric current IdcCalculation formula are as follows:
Wherein, p1For p1=-δ+ωr, p2For p2=-δ-ωr；
As D=0, the faulty circuit is in overdamp single order loop state, the direct-current short circuit electric current IdcCalculation formula
Are as follows:
Idc(t)=Idc0e-2δt。
6. a kind of direct-current short circuit electric current computing system of modularization multi-level converter characterized by comprising
First obtains module, for obtaining faulty circuit in the DC current and DC voltage of fault moment；
Second obtains module, calculates for obtaining multiple bridge arm reference voltages and the DC reference voltage of the faulty circuit straight
Flow modulation ratio；
Third obtains module, calculates the preset parameter of the faulty circuit for obtaining multiple circuit parameters, according to the event
Hinder the time-varying parameter of preset parameter and the HVDC Modulation than calculating the faulty circuit of circuit；
Computing module, for according to the DC current, the DC voltage, the HVDC Modulation than, the faulty circuit
Preset parameter and the time-varying parameter of the faulty circuit judge the state of the faulty circuit, and calculate the straight of the faulty circuit
Flow short-circuit electric current.
7. system according to claim 6, which is characterized in that the calculation formula of the HVDC Modulation ratio D are as follows:
Wherein, D is HVDC Modulation ratio, uap *For bridge arm reference voltage in a phase, uan *For a phase lower bridge arm reference voltage, ubp *For b phase
Upper bridge arm reference voltage, ubn *For b phase lower bridge arm reference voltage, ucp *For bridge arm reference voltage in c phase, ucn *For c phase lower bridge arm ginseng
Examine voltage, Udc *For DC reference voltage.
8. system according to claim 6, which is characterized in that described to obtain multiple circuit parameters to calculate the failure electricity
The preset parameter on road, specifically includes:
The preset parameter of the faulty circuit includes: equivalent reactance Le, equivalent resistance ReWith equivalent capacity Ce, calculation formula are as follows:
Wherein, LeFor equivalent reactance, ReFor equivalent resistance, CeFor equivalent capacity, N indicates bridge arm submodule number, CdIndicate each
The capacitor of submodule, LsIndicate bridge arm inductance, LdcIndicate DC line inductance, RsIndicate arm resistance, RfIndicate fault resstance.
9. system according to claim 8, which is characterized in that the preset parameter according to the faulty circuit and described
Time-varying parameter of the HVDC Modulation than calculating the faulty circuit, specifically includes:
The time-varying parameter of the faulty circuit includes: attenuation coefficient δ, resonance angular frequency ω0, oscillation angular frequencyrAnd hunting angle
γ,
Calculation formula are as follows:
Wherein, δ is attenuation coefficient, ω0For resonance angular frequency, ωrTo vibrate angular frequency, γ is hunting angle, and D is HVDC Modulation ratio.
10. system according to claim 9, which is characterized in that the computing module is specifically used for,
WhenWhen, the faulty circuit is in underdamping state, the direct-current short circuit electric current IdcCalculating it is public
Formula are as follows:
Idc(t)=Ae-δtsin(ωrt+β)
Wherein, Idc0For DC current, Udc0For DC voltage；
WhenWhen, the faulty circuit is in Critical damping state, the direct-current short circuit electric current IdcCalculating
Formula are as follows:
Idc(t)=(A3+A4t)e-δt
WhenWhen, the faulty circuit is in overdamping state, it is specifically divided into:
As D > 0, the faulty circuit is in overdamp second order loop state, direct-current short circuit electric current IdcCalculation formula are as follows:
Wherein, p1For p1=-δ+ωr, p2For p2=-δ-ωr；
As D=0, the faulty circuit is in overdamp single order loop state, the direct-current short circuit electric current IdcCalculation formula
Are as follows:
Idc(t)=Idc0e-2δt。
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