CN110110486A - A kind of DAB type DC converter high-frequency resistance equivalent modeling method - Google Patents
A kind of DAB type DC converter high-frequency resistance equivalent modeling method Download PDFInfo
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Abstract
The invention belongs to flexible direct current distribution system fault location technology fields, more particularly to a kind of DAB type DC converter high-frequency resistance equivalent modeling method, it include: to analyze the single DAB module in DAB type DC converter, switching device is equivalent to resistive element, and ignores the influence of switching process；Generated step signal analyzes the high-frequency resistance circuit of DC converter after failure, is derived from its high-frequency resistance expression formula as high frequency source when using the system failure.It specifically includes: it is first that the progress of circuit medium/high frequency transformer is equivalent, and parameter is all converted to high-pressure side, establish the relational expression of the voltage and electric current between two coupling coil of transformer；Further according to the structure and parameter of high frequency transformer, each circuit parameter in transformer T-type equivalent circuit is derived, and convert and arrive high-pressure side, obtain its equivalent circuit.The present invention solves power electronic devices and gives system bring nonlinear characteristic, and the model of acquisition has very high precision.
Description
Technical field
The invention belongs to flexible direct current distribution system fault location technology field more particularly to a kind of DAB type DC convertings
Device high-frequency resistance equivalent modeling method.
Background technique
In recent years, the flexible loads such as distributed generation resource, electric car of scale are incorporated to by power electronics converter
Power distribution network has become development trend, and direct-flow distribution system is few with its switch-over unit, structure is simple, high conversion efficiency, radius of electricity supply
And the advantages such as capacity is big, good economy performance, become the hot subject of domestic and international research and development.In flexible direct current distribution system,
DC link shows forceful electric power power electronization feature, and the different topology structure of network, different control strategies all can be to fault signatures
It has an impact, fault current attenuation components are abundant, inconstant fault component, and then lead to the spy after DC link failure
Levy indefinite, fault transient process is relative complex and nonlinear characteristic is stronger, it is difficult to accurately extract and analyze fault signature.
It is less about researching and analysing for DC converter fault characteristic both at home and abroad at present, there is scholar for power electronics transformation
Device DC port intereelectrode short-circuit has carried out Faults Characteristic Analysis, gives the expression formula of failure rear port voltage and short circuit current,
But it is equivalent not carry out model to DC converter.The Fault Locating Method of most of direct current systems is also all by after to failure
Electrical quantity parsed to carry out, really solve DC converter give system bring nonlinear problem.Therefore, have
Necessity studies the fault loop of commutator transformer, influences brought by analysis switching device, occurs in solution system
Nonlinear problem proposes a kind of linear Equivalent Model of DC converter not influenced by switching device state.
Summary of the invention
In view of the above technical problems, the present invention proposes a kind of DAB type DC converter high-frequency resistance equivalent modeling method, packet
It includes:
Step 1: the single DAB module in DAB type DC converter being analyzed, switching device is equivalent to resistance member
Part, and ignore the influence of switching process；
Step 2: generated step signal analyzes DC converter after failure as high frequency source when using the system failure
High-frequency resistance circuit is derived from its high-frequency resistance expression formula.
The step 2 specifically includes:
It is first that the progress of circuit medium/high frequency transformer is equivalent, and parameter is all converted to high-pressure side, establish two coupling of transformer
The relational expression of voltage and electric current between zygonema circle；Further according to the structure and parameter of high frequency transformer, transformer T-type etc. is derived
Each circuit parameter in circuit is imitated, and converts and arrives high-pressure side, obtains its equivalent circuit.
The step 2 further include: using high-frequency electrical tolerance generated after the system failure as source, analyze post-fault system
In high-frequency signal access, the switching device part in access is equivalent at constant resistance, and by circuit transformer use
The T-type circuitry instead that abbreviation comes out obtains the high-frequency equivalent models of single DAB module, obtains the high frequency entered in terms of high-pressure side
Impedance expression.
The step 2 further include: ignore the impedance parameter L in transformer T-type equivalent circuit12Afterwards to single DAB module
High frequency equivalent impedance is further simplified, and finally obtains the entire DC converter after multiple DAB module equivalent circuits are connected in series
High frequency equivalent impedance.
The equivalent circuit is again and high after arm resistance, transformer impedance and low-pressure side Support Capacitor are together in series
Press lateral capacitance in parallel.
Beneficial effects of the present invention:
(1) switch state that analysis obtains bridge arm when by system bipolar short trouble is not occurred for Equivalent Model is influenced；
(2) it solves power electronic devices and gives system bring nonlinear characteristic, the model of system linearization, acquisition is had
There is very high precision, is conducive to the analysis of flexible direct current system fault characteristic and fault location technology.
Detailed description of the invention
Fig. 1 is DAB type DC converter high-frequency resistance modeling method flow chart of the invention；
Fig. 2 is single DAB module topology structural schematic diagram；
Fig. 3 is high-frequency transformer structure figure and its T-type schematic equivalent circuit；
Fig. 4 is that the high-frequency current loop diagram after bipolar short trouble occurs for DAB module DC port；
Fig. 5 is single DAB module high-frequency resistance Equivalent Model；
Fig. 6 is DAB type DC converter topology diagram；
Fig. 7 is DC converter high-frequency resistance calculated value and theoretical value simulation comparison figure.
Specific embodiment
With reference to the accompanying drawing, it elaborates to embodiment.
Fig. 1 is DAB type DC converter high-frequency resistance equivalent modeling method flow chart of the invention, and the invention proposes one
Kind DAB type DC converter high-frequency resistance equivalent modeling method, comprising the following steps:
Step 1: the single DAB module in DAB type DC converter being analyzed, switching device is equivalent to resistance member
Part, and ignore the influence of switching process；
Step 2: generated step signal analyzes DC converter after failure as high frequency source when using the system failure
High-frequency resistance circuit is derived from its high-frequency resistance expression formula.
In the step 1, DAB type DC converter is by multiple DAB modules in low-pressure side parallel connection, and high-pressure side is connected in series
It constitutes, first single DAB module can be analyzed；In DAB module routine, the switching frequency of two sides H bridge is identical,
Diagonal switching tube simultaneously turns on；Based on this, since there are two kinds of directions for the electric current in DAB module, according to the control characteristic of switch
Two kinds of current loops can be obtained, analyze both circuits it is found that regardless of current direction and switch state, in high frequency transformer
Former secondary circuit in can all pass through IGBT or anti-paralleled diode twice, the conducting resistance size of switching device is identical, and opens
Higher frequency signal energy caused by during closing is much smaller than fault transient dash current high frequency, therefore can be equivalent to switching device
Resistive element, and ignore the influence of switching process.
In the step 2 when bipolar short trouble occurs for direct current system, fault point voltage can be reduced to zero in several milliseconds,
A step signal is generated, which is subjected to spectrum analysis, its available full range domain information, and signal frequency is got over
Height, spectral density are bigger；Simultaneously because requirement of the flexible direct current power grid to protection rapidity causes for fault locating analysis
Data window is up to several milliseconds long, and low-frequency information is difficult to accurately extract, and high-frequency signal recognition effect is preferable, therefore utilizes system event
Generated step signal analyzes the high-frequency resistance circuit of DC converter after failure, first by circuit as high frequency source when barrier
Medium/high frequency transformer progress is equivalent, according to the structure and parameter of high frequency transformer, derives each in transformer T-type equivalent circuit
Circuit parameter L1、L2And L12, and convert and arrive high-pressure side, obtain its equivalent circuit.
Using high-frequency electrical tolerance generated after the system failure as source, the high-frequency signal analyzed in post-fault system is logical
Road can have two kinds of high-frequency currents events due to the control mode that DAB module uses diagonal switching tube to simultaneously turn on, after the system failure
Hinder circuit, can be obtained according to the analysis in step 1, the switching process of switching device can be ignored, and both circuits are in the primary side of DAB
Pass through switching device twice with secondary Bian Douhui, the equivalent circuit of current path can regard identical as；By the switch in access
Device portions are equivalent at constant resistance, and the T-type circuitry instead that the transformer in circuit is come out with abbreviation, obtain single
The high-frequency equivalent models of DAB module, the high-frequency resistance entered in terms of high-pressure side are as follows:
In formula, C0For high voltage direct current side outlet capacitor, C1For low-voltage direct lateral capacitance, RlAnd LlRespectively line resistance and
Reactance, r are the conducting resistance of bridge arm switching device, L1、L2And L12For the impedance parameter in transformer T-type equivalent circuit；
Transformer T-type equivalent circuit parameter is it is found that L according to obtained in step 212Calculated value be about L1And L2's
It 500 times, can be by L when carrying out equivalent in order to keep circuit easier12Place branch is ignored, then the high frequency of single DAB module
Equivalent impedance can be further simplified are as follows:
The equivalent circuit be equivalent to arm resistance, transformer impedance and low-pressure side Support Capacitor be together in series after again and
High pressure lateral capacitance is in parallel, and all parameters are converted to high-pressure side；
DAB type DC converter is to be made of multiple DAB modules in low-pressure side parallel connection, high-pressure side series connection, will be single
After the high frequency equivalent circuit of DAB module solves, enter in terms of DC line port, entire DC converter is equivalent to more
A DAB module equivalent circuit is connected in series, and therefore, the high frequency equivalent impedance of DC converter can indicate are as follows:
ZS=NZS_DAB
In formula, ZS_DABIndicate that the high-frequency resistance of single DAB module, N indicate the number of modules of DAB in commutator transformer.
Fig. 2 is single DAB module topology structural schematic diagram.DAB module is by two sides H bridge and common group of high frequency transformer
At the bridge arm of H bridge is made of IGBT and anti-paralleled diode.In the low pressure side and high pressure side of converter, there are two electricity simultaneously
Hold, plays the role of filtering and voltage support.In DAB module routine, the switching frequency of two sides H bridge is identical, diagonally
Switching tube simultaneously turns on.Two kinds of current loops can be obtained according to the control characteristic of switch, both circuits can be used by analysis
The same equivalent circuit replaces, to ignore the influence of switch state and switching process.
Fig. 3 is high-frequency transformer structure figure and its T-type schematic equivalent circuit.What left figure indicated is in high frequency transformer
Two windings to intercouple, L11、L22Indicate the self-induction of two windings, L12Indicate the mutual inductance between winding.According to the original of transformer
Reason, can be reduced to T-type circuit shown in right figure, and parameter is all converted to high-pressure side.
Fig. 4 is that the high-frequency current loop diagram after bipolar short trouble occurs for DAB module DC port.DC side occurs bipolar
After short trouble, fault point step voltage, which decomposites the high frequency content come, can be used as a high frequency source, analyze using it as power supply
High frequency fault circuit.Since the control signal of switching device is complementary square-wave signal, there are two kinds of radio circuits.It is based on
The analysis that above-mentioned switching device influences circuit, it is known that two radio circuits can be equivalent at the same circuit, switch state and
Switching process is negligible.
Fig. 5 is single DAB module high-frequency resistance Equivalent Model.Equivalent and high frequency fault circuit based on high frequency transformer
Analysis, the transformer in circuit is replaced with T-type equivalent circuit, two sides H bridge is replaced with conducting resistance, simultaneously as L12's
Calculated value is about L1And L2500 times, therefore can be by L12Place branch is ignored, and low-pressure side parameter is converted to high-pressure side, similar
The parameter of type merges, and finally obtains equivalent circuit shown in fig. 5.
Fig. 6 is DAB type DC converter topology diagram.The converter be by multilayer DAB module composition, each module
Low-pressure side is in parallel, and straightening streaming system in the series connection access of high-pressure side, cascaded structure can be divided effectively, improves the pressure resistance of DC converter
It is horizontal.Therefrom straightening streamline road port is seen into, and entire converter is equivalent to all DAB block coupled in series connections, and therefore, direct current becomes
Parallel operation is single DAB module equivalent impedance from the high frequency equivalent impedance value entered in terms of high-pressure side and number of modules in inverter multiplies
Product.
Fig. 7 is DC converter high-frequency resistance calculated value and theoretical value simulation comparison figure.It builds in PSCAD containing DAB
The low-pressure side of the flexible direct current system of type DC converter, each DAB module is connected with photo-voltaic power supply, and high-pressure side is together in series access
Middle straightening streaming system.When bipolar short trouble occurs for DC side, the voltage and electricity at inverter direct current system side outlet are measured
Stream, is carried out wavelet transformation, obtains each frequency domain value of voltage and current, and then acquire the impedance under each frequency, this is calculated
Value is compared with theoretical value, obtains result shown in figure.
Simulation result shows to pass through analytic transformation device switch state when bipolar short trouble occurs for flexible direct current system
Influence to fault loop, using step voltage after failure as power supply, the loopback diagnostic of analysis of high frequency electric current is finally obtained
The high-frequency resistance Equivalent Model of DAB type DC converter, it is generated non-linear in systems which eliminates switching device
Problem, in 800-1600Hz frequency range, equivalent model has very high precision.
This embodiment is merely preferred embodiments of the present invention, but scope of protection of the present invention is not limited thereto,
In the technical scope disclosed by the present invention, any changes or substitutions that can be easily thought of by anyone skilled in the art,
It should be covered by the protection scope of the present invention.Therefore, protection scope of the present invention should be with scope of protection of the claims
Subject to.
Claims (5)
1. a kind of DAB type DC converter high-frequency resistance equivalent modeling method characterized by comprising
Step 1: the single DAB module in DAB type DC converter is analyzed, switching device is equivalent to resistive element,
And ignore the influence of switching process；
Step 2: generated step signal analyzes the high frequency of DC converter after failure as high frequency source when using the system failure
Impedance path is derived from its high-frequency resistance expression formula.
2. method according to claim 1, which is characterized in that the step 2 specifically includes:
It is first that the progress of circuit medium/high frequency transformer is equivalent, and parameter is all converted to high-pressure side, establish two coupling line of transformer
The relational expression of voltage and electric current between circle；Further according to the structure and parameter of high frequency transformer, the equivalent electricity of transformer T-type is derived
Each circuit parameter in road, and convert and arrive high-pressure side, obtain its equivalent circuit.
3. method according to claim 1 or claim 2, which is characterized in that the step 2 further include: using being produced after the system failure
Raw high-frequency electrical tolerance analyzes the high-frequency signal access in post-fault system, by the switching device part etc. in access as source
Constant resistance, and the T-type circuitry instead that the transformer in circuit is come out with abbreviation are imitated into, the height of single DAB module is obtained
Frequency equivalent model obtains the high-frequency resistance expression formula entered in terms of high-pressure side.
4. method according to claim 1 or claim 2, which is characterized in that the step 2 further include: ignore the equivalent electricity of transformer T-type
Impedance parameter L in road12The high frequency equivalent impedance of single DAB module is further simplified afterwards, finally obtains multiple DAB modules etc.
Imitate the entire DC converter high frequency equivalent impedance after circuit is connected in series.
5. method according to claim 2, which is characterized in that the equivalent circuit be arm resistance, transformer impedance and
Low-pressure side Support Capacitor is in parallel with high pressure lateral capacitance again after being together in series.
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| CN114859165A (en) * | 2021-04-15 | 2022-08-05 | 贵州电网有限责任公司 | Direct-current distribution network fault section positioning method based on wide area communication method |
| CN117638804A (en) * | 2023-11-08 | 2024-03-01 | 广东工业大学 | Differential protection method and system for primary side overcurrent faults of train traction transformer |
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