CN113507096A - Oscillating circuit containing parasitic parameters and direct current change-over switch - Google Patents

Oscillating circuit containing parasitic parameters and direct current change-over switch Download PDF

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Publication number
CN113507096A
CN113507096A CN202110782810.7A CN202110782810A CN113507096A CN 113507096 A CN113507096 A CN 113507096A CN 202110782810 A CN202110782810 A CN 202110782810A CN 113507096 A CN113507096 A CN 113507096A
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parasitic
capacitor
circuit
inductance
unit
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蒋紫薇
宁雪峰
刘泽槐
黄漫欣
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Guangdong Power Grid Co Ltd
Dongguan Power Supply Bureau of Guangdong Power Grid Co Ltd
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Guangdong Power Grid Co Ltd
Dongguan Power Supply Bureau of Guangdong Power Grid Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/02—Arrangements for reducing harmonics or ripples
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/20—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising resistance and either capacitance or inductance, e.g. phase-shift oscillator

Abstract

The embodiment of the invention discloses an oscillating circuit containing parasitic parameters and a direct current change-over switch, wherein the oscillating circuit comprises: the capacitor unit comprises a plurality of oscillation branches, and the oscillation branches are connected in parallel; each oscillation branch comprises a plurality of capacitors connected in series, and parasitic parameters contained in each capacitor comprise parasitic inductance and parasitic resistance; the inductor unit, the damping resistance unit and the capacitor unit are connected in series. The technical scheme provided by the embodiment of the invention combines the actual connection mode of the capacitors in the oscillating circuit, provides a combination mode of series-parallel connection of a plurality of capacitors, and improves the problem of unmatched capacitor parameters by considering the influence of parasitic inductance and parasitic resistance contained in the capacitors on the generated oscillating alternating current, thereby improving the on-off success rate of the direct current change-over switch and ensuring the stability of a direct current transmission system.

Description

Oscillating circuit containing parasitic parameters and direct current change-over switch
Technical Field
The embodiment of the invention relates to the technical field of direct current transmission, in particular to an oscillating circuit containing parasitic parameters and a direct current change-over switch.
Background
The direct current change-over switch plays roles of fault isolation, operation mode conversion and the like in a direct current power grid. The change-over switch is mainly composed of three parts, namely a breaking circuit, an energy absorption circuit and an oscillating circuit. The oscillating circuit is used for generating oscillating alternating current which is superposed on direct current to generate a current zero crossing point so as to be used for a circuit breaker of the circuit breaking circuit to break.
In the prior art, the capacitance part in the oscillating circuit has the problem of unmatched capacitance parameters, which causes the failure of the on-off of the extra-high voltage direct current change-over switch and seriously affects the stability of a direct current transmission system.
Disclosure of Invention
The embodiment of the invention provides an oscillating circuit containing parasitic parameters and a direct current change-over switch, which are used for solving the problem of unmatched capacitance parameters, improving the on-off success rate of the direct current change-over switch and ensuring the stability of a direct current transmission system.
In a first aspect, an embodiment of the present invention provides an oscillating circuit with parasitic parameters, including:
the capacitance unit comprises a plurality of oscillation branches, and the oscillation branches are connected in parallel; each oscillation branch comprises a plurality of capacitors connected in series; each capacitor comprises parasitic parameters including parasitic inductance and parasitic resistance;
the inductor unit, the damping resistance unit and the capacitor unit are connected in series.
Optionally, the capacitance unit includes a first oscillation branch, a second oscillation branch, a third oscillation branch, a fourth oscillation branch, a fifth oscillation branch, and a sixth oscillation branch;
the first oscillation branch comprises a first capacitor and a fourth capacitor which are connected in series; the first capacitor comprises parasitic parameters including a first parasitic inductance and a first parasitic resistance; the parasitic parameters contained in the fourth capacitor comprise a fourth parasitic inductance and a fourth parasitic resistance;
the second oscillation branch comprises a second capacitor and a fifth capacitor which are connected in series; the parasitic parameters contained in the second capacitor comprise a second parasitic inductance and a second parasitic resistance; parasitic parameters contained in the fifth capacitor comprise a fifth parasitic inductor and a fifth parasitic resistor;
the third oscillation branch comprises a third capacitor and a sixth capacitor which are connected in series; the parasitic parameters contained in the third capacitor comprise a third parasitic inductance and a third parasitic resistance; parasitic parameters contained in the sixth capacitor comprise a sixth parasitic inductor and a sixth parasitic resistor;
the fourth oscillation branch comprises a seventh capacitor and a tenth capacitor which are connected in series; the parasitic parameters contained in the seventh capacitor comprise a seventh parasitic inductor and a seventh parasitic resistor; the parasitic parameters contained in the tenth capacitor comprise a tenth parasitic inductance and a tenth parasitic resistance;
the fifth oscillation branch comprises an eighth capacitor and an eleventh capacitor which are connected in series; parasitic parameters contained in the eighth capacitor comprise an eighth parasitic inductor and an eighth parasitic resistor; the eleventh capacitor comprises parasitic parameters including an eleventh parasitic inductance and an eleventh parasitic resistance;
the sixth oscillation branch comprises a ninth capacitor and a twelfth capacitor which are connected in series; parasitic parameters contained in the ninth capacitor comprise a ninth parasitic inductor and a ninth parasitic resistor; the twelfth capacitor has parasitic parameters including a twelfth parasitic inductance and a twelfth parasitic resistance.
Optionally, a common connection end of the second capacitor and the fifth capacitor is electrically connected to a common connection end of the third capacitor and the sixth capacitor;
and the common connection end of the eighth capacitor and the eleventh capacitor is electrically connected with the common connection end of the ninth capacitor and the twelfth capacitor.
Optionally, the capacitors connected in series on the first oscillation branch, the second oscillation branch, the third oscillation branch, the fourth oscillation branch, the fifth oscillation branch and the sixth oscillation branch are all equal.
Optionally, the first parasitic inductance, the second parasitic inductance, the third parasitic inductance, the fourth parasitic inductance, the fifth parasitic inductance, the sixth parasitic inductance, the seventh parasitic inductance, the eighth parasitic inductance, the ninth parasitic inductance, the tenth parasitic inductance, the eleventh parasitic inductance, and the twelfth parasitic inductance are not completely the same;
the first parasitic resistor, the second parasitic resistor, the third parasitic resistor, the fourth parasitic resistor, the fifth parasitic resistor, the sixth parasitic resistor, the seventh parasitic resistor, the eighth parasitic resistor, the ninth parasitic resistor, the tenth parasitic resistor, the eleventh parasitic resistor and the twelfth parasitic resistor are not completely the same.
Optionally, after the capacitor unit, the inductor unit and the damping resistor unit are connected in series, the capacitor unit, the inductor unit and the damping resistor unit are connected in parallel to two ends of a switching-off loop of the dc switch together, so as to be connected in series in the dc power transmission system.
Optionally, when the open-close loop of the dc converter switch is disconnected, the capacitor unit, the inductor unit and the damping resistor unit resonate to generate an oscillating ac power, and the oscillating ac power is determined based on the following:
Figure BDA0003157776050000031
wherein, UC+UL+UR＝U，UCIs the voltage across the capacitor unit, ULIs the voltage across the inductive element, URIs the voltage across the damping resistance unit; u is the total voltage provided for the oscillation circuit when the open circuit of the direct current change-over switch is disconnected;
Z＝Z0+R+sL；Z0the total impedance of each capacitor in the capacitor unit and the parasitic inductance and the parasitic resistance contained in the capacitor unit, R is a damping resistance, sL is the inductive reactance of the inductance under the pull-type transformation, and Z is the total impedance of the oscillating circuit.
In a second aspect, an embodiment of the present invention provides a dc transfer switch, which is disposed in a dc transmission line and is used for controlling the on/off of the dc transmission line; the circuit comprises a breaking circuit, an energy absorption circuit and the oscillating circuit containing the parasitic parameters.
Optionally, the open circuit, the energy absorption circuit and the oscillation circuit are connected in parallel;
the oscillating circuit is used for generating oscillating alternating current and superposing the oscillating alternating current in direct current of the direct current transmission line to generate a current zero crossing point for the on-off circuit to be switched off;
the energy absorption loop is used for absorbing and discharging electric energy in the loop when the voltage at two ends of the capacitor unit in the oscillation loop reaches the rated voltage of the action of the energy absorption loop lightning arrester, so that the current on the direct current transmission line is reduced to zero, and the disconnection of the direct current transmission line is completed.
Optionally, the energy-absorbing circuit includes a lightning arrester, and the open-close circuit includes a circuit breaker connected to the dc transmission line.
The embodiment of the invention provides an oscillating circuit containing parasitic parameters and a direct current change-over switch, wherein the oscillating circuit comprises: the capacitance unit comprises a plurality of oscillation branches, and the oscillation branches are connected in parallel; each oscillation branch comprises a plurality of capacitors connected in series; each capacitor comprises parasitic parameters including parasitic inductance and parasitic resistance; the inductor unit, the damping resistance unit and the capacitor unit are connected in series. The technical scheme provided by the embodiment of the invention combines the actual connection mode of the capacitors in the oscillating circuit, provides a combination mode of series-parallel connection of a plurality of capacitors, and combines the influence of parasitic inductance and parasitic resistance contained in the capacitors on the generated oscillating alternating current, thereby improving the problem of unmatched capacitor parameters, improving the on-off success rate of the direct current change-over switch and ensuring the stability of a direct current transmission system.
Drawings
Fig. 1 is a circuit diagram of a dc converter switch provided in the prior art;
fig. 2 is a circuit diagram of an oscillation circuit in a dc converter switch provided in the prior art;
fig. 3 is a block diagram of an oscillating circuit with parasitic parameters according to an embodiment of the present invention;
FIG. 4 is a circuit diagram of an oscillating circuit with parasitic parameters according to an embodiment of the present invention;
fig. 5 is a circuit diagram of a dc converter switch according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
The ultra-high voltage direct current transmission has the advantages of long distance, small loss, good stability, large transmission capacity, capability of connecting two power grids with different frequencies and the like, is an important component in a strong power grid in China, and is widely applied in the world. In recent years, China has made a rapid development in the research and application of high-voltage direct-current transmission technology, and direct-current transmission becomes an important component of a strong power grid in China. In the direct current transmission project, the direct current change-over switch mainly has the functions of changing the operation mode of the direct current transmission system, timely clearing faults occurring in a line and isolating fault equipment, and can also be used for forming a radial, ring network, radiation and other multi-terminal direct current transmission system, and the direct current change-over switch is a primary electrical main device which ensures safe, reliable and economic operation of the direct current project.
Fig. 1 is a circuit diagram of a dc converter switch provided in the prior art, and referring to fig. 1, the dc converter switch mainly includes three parts, namely, a breaking circuit, an energy absorption circuit, and an oscillation circuit. The energy absorption loop comprises a lightning arrester ZnO, and the breaking loop comprises a circuit breaker CB connected to the direct current transmission line I. The oscillation-containing loop comprises a capacitor C, and an inductor L and a damping resistor R which are connected with the capacitor C in series. The on-off process of the direct current change-over switch is mainly divided into three parts: forced zero-crossing current stage, fracture medium recovery stage and lightning arrester actionAnd (5) an energy absorption stage. Referring to fig. 1, taking a passive dc converter as an example, after the dc converter receives a command to turn on/off the current, the switch S of the oscillating circuit1Closing, connecting an oscillating circuit in parallel at two ends of the open circuit, then, firstly, carrying out arc discharge on direct current by a breaker CB of the open circuit, rapidly charging a capacitor C in the oscillating circuit by arc voltage, generating oscillating alternating current by a back-and-forth charging and discharging process between the arc and the capacitor because the arc is unstable and has jumping property, the arc voltage cannot be kept at a fixed value, and generating oscillation alternating current to be superposed on the direct current to create a current zero crossing point and extinguish the arc because of resonance of an inductor L, the capacitor C and a damping resistor R in the oscillating circuit, so that the first stage, namely a current zero crossing forcing stage, is completed. After the electric arc is extinguished, the two ends of the CB contact of the circuit breaker enter a medium recovery stage, and at the moment, the energy generated in the arc burning process is not released, so that the energy can be converted into recovery voltage to be applied to the two ends of the capacitor C, and the electric arc can not be reignited only when the medium recovery voltage speed of the gap between the CB contacts of the circuit breaker is greater than the recovery voltage speed of the electric arc, which is a second stage-fracture medium recovery stage. When the voltage at two ends of the capacitor in the oscillation circuit reaches the rated voltage of the energy absorption circuit arrester ZnO, the arrester ZnO acts to absorb and discharge huge energy in the circuit, the voltage at two ends of the CB contact of the circuit breaker is limited within a controllable range, the current is rapidly reduced to zero, the disconnection is completed, and the ZnO energy absorption action stage of the arrester is the stage of the energy absorption action of the arrester ZnO.
The important thing in the whole process is the first stage, namely the current zero crossing forcing stage, in which the switch of the oscillating circuit is closed, the oscillating circuit is connected in parallel with two ends of the open circuit, then the breaker of the open circuit firstly draws the direct current to carry out arc, the electric arc voltage rapidly charges the capacitor C in the oscillating circuit, the electric arc voltage can not be kept at a fixed value due to the instability and jumping of the electric arc, and a reciprocating charge-discharge process can be generated between the electric arc and the capacitor C due to the resonance of the inductor, the capacitor and the resistor in the oscillating circuit, the oscillating alternating current can be generated in the process and is superposed on the direct current to create a current zero crossing point, the electric arc is extinguished, and the current is transferred from the open circuit to the oscillating circuit. It is critical at this stage that the tank circuit generates an oscillating alternating current.
If the direct current change-over switch can not be successfully switched on or off, the power transmission mode of direct current power transmission can not be normally changed, and the stable operation of direct current power transmission is threatened. The oscillating circuit is composed of a capacitor, an inductor and a resistor, wherein only the capacitor is composed of an actual capacitor, and the inductor and the resistor are composed of the surrounding environment and stray parameters at the lead wires, so that whether the capacitor can be in a normal state or not is greatly influenced by the normal operation of the oscillating circuit and even the direct current change-over switch. In the prior art, most of oscillating circuits in a direct current transfer switch are subjected to simple capacitor and inductor series modeling, so that the influence of converter circuit parameters in a direct current breaker is analyzed.
Fig. 2 is a circuit diagram of an oscillating circuit in a dc transfer switch provided in the prior art, referring to fig. 2, wherein a current i is an oscillating alternating current; u represents the arc voltage, i.e., the voltage across the dc transfer switch, which is a variable; C. l, R denotes the capacitance, inductance and resistance of the tank circuit, respectively; u. ofC、uL、uRRespectively representing the real-time voltage values across the capacitor, the inductor and the resistor. Then according to kirchhoff's law, the relationship satisfied between them is:
U＝uR+uL+uC (1.1)
wherein:
uR＝Ri (1.2)
Figure BDA0003157776050000071
substituting the formula (1.1) to obtain:
Figure BDA0003157776050000072
the time t is derived from equation (1.4):
Figure BDA0003157776050000081
the equation (1.5) is a second-order constant coefficient linear differential equation, the solution of the current i can be divided into a special solution and a general solution, and the characteristic equation is as follows:
LCs2+RCs+1＝0 (1.6)
the two characteristic solutions of equation (1.6) are:
Figure BDA0003157776050000082
Figure BDA0003157776050000083
as can be seen from the above equations (1.7) and (1.8), the solution of equation (1.6) is independent of the state of the system, and is only dependent on the values of the capacitance, inductance, and resistance parameters inside the system. From circuit analysis of the second-order oscillation loop, it can be known that the values of different parameters correspond to three different states of the circuit: over-damping (δ > ω), under-damping (δ < ω), and critical oscillation (δ ═ ω).
I.e. the attenuation coefficient δ is:
Figure BDA0003157776050000084
the oscillation angular frequency ω is:
Figure BDA0003157776050000085
the oscillation frequency f is:
Figure BDA0003157776050000086
the expression for the generated oscillating alternating current i can be written as:
Figure BDA0003157776050000091
wherein, I1Is a general solution of the equation; i is2Is a special solution of the equation and is related to the first derivative of the voltage U; θ is an adjustment angle measure introduced in consideration of the influence of nonlinear inductance and capacitance on the angle; m is a variable related to the first derivative of the voltage U, i.e., the solution.
The formula (1.12) can find that the oscillating alternating current generated by the oscillating circuit of the passive direct current transfer switch is an amount of which the amplitude is continuously increased along with the increase of the time t, so that the artificially created 'current zero-crossing point' can occur after the alternating current oscillates for a certain time, namely the amplitude of the oscillating alternating current reaches the amplitude of the direct current for a certain time, instead of the artificially created 'current zero-crossing point' occurring in the first period of oscillation in the switching-off process of the active direct current transfer switch.
In the prior art, most of oscillating circuits in a direct current transfer switch are subjected to simple capacitor and inductor series modeling, so that the influence of converter circuit parameters in a direct current breaker is analyzed; in practice, a capacitor is a sum comprising a plurality of capacitors. In addition, in the prior art, the parasitic inductance and the parasitic resistance of each capacitor are not analyzed, so that the problem of unmatched capacitor parameters is caused, the on-off failure of the extra-high voltage direct current transfer switch is caused, and the stability of a direct current transmission system is seriously influenced.
In view of the above, firstly, an embodiment of the present invention provides an oscillating circuit with parasitic parameters, fig. 3 is a block diagram of a structure of an oscillating circuit with parasitic parameters provided in an embodiment of the present invention, and referring to fig. 3, the oscillating circuit includes:
the capacitor unit 10 comprises a plurality of oscillation branches, and the oscillation branches are connected in parallel; each oscillation branch comprises a plurality of capacitors 11 connected in series; each capacitor 11 has parasitic parameters including parasitic inductance and parasitic resistance;
the inductance unit 20 and the damping resistance unit 30, and the inductance unit 20, the damping resistance unit 30 and the capacitance unit 10 are connected in series.
Specifically, the tank circuit including the parasitic parameter includes a capacitor unit 10, an inductor unit 20, and a damping resistor unit 30. The inductance unit 20, the damping resistance unit 30, and the capacitance unit 10 are connected in series. The capacitor unit 10 includes a plurality of oscillation branches, and the oscillation branches are connected in parallel. Each oscillation branch comprises a plurality of capacitors 11 connected in series; each capacitor 11 contains parasitic parameters including parasitic inductance and parasitic resistance. Parasitic inductance and parasitic resistance are some lead wires and media involved inside each capacitor, so some small resistance and small inductance influence is also involved inside the capacitor, namely the influence of the parasitic resistance and parasitic inductance. The technical scheme provided by the embodiment of the invention provides a combination form of series-parallel connection of a plurality of capacitors by combining with an actual connection mode of the capacitors in the oscillating circuit, and the influence of parasitic parameters, parasitic inductance and parasitic capacitance contained in the capacitors on the generated oscillating alternating current is considered, so that the problem of unmatched capacitor parameters is solved, the on-off success rate of the direct current change-over switch is improved, and the stability of a direct current transmission system is ensured.
Optionally, fig. 4 is a circuit diagram of an oscillation circuit with parasitic parameters according to an embodiment of the present invention, and referring to fig. 4, the capacitance unit includes a first oscillation branch, a second oscillation branch, a third oscillation branch, a fourth oscillation branch, a fifth oscillation branch, and a sixth oscillation branch;
wherein the first oscillation branch comprises a first capacitor C connected in series1And a fourth capacitance C4(ii) a A first capacitor C1The parasitic parameters include a first parasitic inductance L1And a first parasitic resistance R1(ii) a Fourth capacitor C4The parasitic parameters include the fourth parasitic inductance L4And a fourth parasitic resistance R4；
The second oscillation branch comprises a second capacitor C connected in series2And a fifth capacitance C5(ii) a Second capacitor C2The parasitic parameters include a second parasitic inductance L2And a second parasitic resistance R2(ii) a Fifth capacitor C5Including parasitic parameters including fifth parasiticInductor L5And a fifth parasitic resistance R5；
The third oscillation branch comprises a third capacitor C connected in series3And a sixth capacitance C6(ii) a Third capacitor C3Including a parasitic parameter including a third parasitic inductance L3And a third parasitic resistance R3(ii) a Sixth capacitor C6The parasitic parameters include the sixth parasitic inductance L6And a sixth parasitic resistance R6；
The fourth oscillation branch comprises a seventh capacitor C connected in series7And a tenth capacitance C10(ii) a Seventh capacitance C7The parasitic parameters include a seventh parasitic inductance L7And a seventh parasitic resistance R7(ii) a A tenth capacitor C10The parasitic parameters include the tenth parasitic inductance L10And a tenth parasitic resistance R10；
The fifth oscillation branch comprises an eighth capacitor C connected in series8And an eleventh capacitance C11(ii) a Eighth capacitor C8The parasitic parameters include the eighth parasitic inductance L8And an eighth parasitic resistance R8(ii) a Eleventh capacitor C11The parasitic parameters include the eleventh parasitic inductance L11And an eleventh parasitic resistance R11；
The sixth oscillation branch comprises a ninth capacitor C connected in series9And a twelfth capacitor C12(ii) a Ninth capacitor C9The parasitic parameters include the ninth parasitic inductance L9And a ninth parasitic resistance R9(ii) a A twelfth capacitor C12Including parasitic parameters including the twelfth parasitic inductance L12And a twelfth parasitic resistance R12。
Wherein the second capacitor C2And the common connection of the fifth capacitor C5 may be connected to the third capacitor C3And a sixth capacitance C6Is electrically connected;
eighth capacitor C8And an eleventh capacitance C11Can be connected with a ninth capacitor C9And a twelfth capacitor C112Are electrically connected.
Specifically, the embodiments of the present invention provideThe oscillating circuit containing the parasitic parameters is connected in parallel with two ends of the cut-off circuit, and the capacitor unit is charged by the arc voltage. The oscillating circuit containing the parasitic parameters adopts a two-string four-parallel structure. Wherein the first capacitor C1A second capacitor C2A third capacitor C3A fourth capacitor C4A fifth capacitor C5A sixth capacitor C6A seventh capacitor C7An eighth capacitor C8A ninth capacitor C9A tenth capacitor C10An eleventh capacitor C11And a twelfth capacitor C12The twelve capacitors can be the same, that is, the capacitors connected in series on the first oscillation branch, the second oscillation branch, the third oscillation branch, the fourth oscillation branch, the fifth oscillation branch and the sixth oscillation branch are all equal.
The impedance in the equivalent model of the capacitive element with parasitic parameters is defined as shown in equation (1):
Figure BDA0003157776050000121
wherein Z is1～Z12Respectively represent a first capacitance C1Twelfth capacitor C12Including impedance after parasitic parameters. L is1、L2、L3、L4、L5、L6、L7、L8……L12The twelve inductors are stray inductances carried by twelve capacitors respectively and are also called parasitic inductance parameters, and the inductance values of the twelve inductors are not completely equal. R1、R2、R3、R4、R5、R6、R7、R8……R12The twelve resistors are stray resistors carried by twelve capacitors respectively and are also called parasitic resistance parameters, and the resistance values of the twelve resistors are not completely equal. The impedance Z corresponding to the capacitor unit in the oscillating circuit0Is shown in the following equation (2):
Z0＝(Z1+Z4)//((Z2//Z3)+(Z5//Z6))//(Z7+Z10)//((Z8//Z9)+(Z11//Z12)) (2)
wherein at an impedance value Z0The parameters in the expression of (a) are expressed as follows:
Figure BDA0003157776050000122
Figure BDA0003157776050000123
Figure BDA0003157776050000124
Figure BDA0003157776050000125
Figure BDA0003157776050000126
Figure BDA0003157776050000131
one capacitor in the centralized capacitor model is changed into a plurality of capacitors, resistors and inductors in series-parallel connection, the number of elements is increased, the analysis of the model is correspondingly complicated, special conditions when one or more elements in the model fail are more prone to occur, and specific analysis on element relations in the oscillating circuit can be achieved. In addition, the influence of parasitic parameters, parasitic inductance and parasitic resistance contained in the capacitor on the generated oscillation alternating current is considered, the problem of unmatched capacitor parameters is solved, the on-off success rate of the direct current change-over switch is improved, and the stability of a direct current transmission system is ensured.
Alternatively, referring to fig. 3, after the capacitor unit 10, the inductor unit 20 and the damping resistor unit 30 are connected in series, they are connected in parallel to two ends of the open circuit of the dc switch, so as to be connected in series in the dc power transmission system.
Specifically, the circuit formed by connecting the inductance unit 20 and the damping resistance unit 30 in series may further include a control switch S, and after the dc transfer switch receives the on-off current command, the oscillation circuit is closed by the control switch S, so that the oscillation circuit is connected in parallel to two ends of the on-off circuit. When the open circuit of the dc converter switch is opened, the oscillating circuit voltage is supplied, and the capacitor unit 10, the inductor unit 20 and the damping resistor unit 30 resonate to generate an oscillating ac power. The circuit in which the inductance unit 20 and the damping resistance unit 30 are connected in series may not be provided with the control switch S, and the control switch S may be directly connected in parallel to both ends of the open circuit of the dc switch to be connected in series in the dc power transmission system, so that the open circuit of the dc switch is disconnected to supply the voltage to the oscillation circuit, and the capacitance unit 10, the inductance unit 20, and the damping resistance unit 30 may also resonate to generate the oscillating ac power. According to fig. 4, in combination with kirchhoff's law, the corresponding theoretical derivation formula is shown in equation (3):
Figure BDA0003157776050000141
wherein u isC1、uC2、uC3、uC7、uC8、uC9Respectively represent capacitances C1、C2、C3、C7、C8、C9The voltage across; i represents the current through each parallel branch; u shapeCThe voltage at two ends of a capacitor bank formed by the whole small capacitor, the stray small inductor and the small resistor in series-parallel connection is represented; i denotes the oscillating alternating current flowing through the tank. Wherein, UC+UL+UR＝U，ULRepresenting the voltage across the inductance L, URRepresenting the voltage across the damping resistor R and U representing the voltage supplied by the circuit breaker. General formula UC+UL+URThe following computational expression (4) - (7) can be obtained by integrating the calculation of the above formula (3) with U;
Figure BDA0003157776050000142
Figure BDA0003157776050000143
obtained by the formula (5):
Figure BDA0003157776050000151
Figure BDA0003157776050000152
the equation of the above formula (7) represents the expression of the oscillation current in the oscillation circuit after the improved capacitance model is added. Because the equation has more related variables, is more complex and is difficult to resolve, the embodiment of the application can change the parameters in the formula (7) into a complex frequency domain and operate by using kirchhoff's law, and then convert the obtained result into an expression in a time domain range. The impedance Z of the tank can be determined by combining the inductance of the inductance element L and the damping resistance of the damping resistance element R in the tank according to equation (2):
Z＝Z0+R+sL (8)
and then converting the expression of the impedance Z of the complex frequency domain into a time domain expression to obtain the impedance value of a part formed by combining twelve small capacitors. Thus, the impedance value of the whole oscillation circuit is obtained, and then the expression of the oscillation alternating current is obtained by using a current calculation method in a complex frequency domain:
Figure BDA0003157776050000153
and according to the impedance Z expression and the current I expression in the complex frequency domain, the current and the impedance expression in the time domain can be obtained by utilizing the pull type inverse transformation. According to the expression in the time domain, characteristics corresponding to the capacitance unit containing the parasitic parameters and key characteristics of the oscillation current with respect to period, attenuation coefficient and amplitude can be analyzed. The technical scheme provided by the embodiment of the invention provides a combination form of series-parallel connection of a plurality of capacitors, and the influence of parasitic parameters, parasitic inductance and parasitic resistance, contained in the capacitors on the generated oscillating alternating current is considered, so that the problem of unmatched capacitor parameters is solved, the on-off success rate of the direct current change-over switch is improved, and the stability of a direct current transmission system is ensured.
The embodiment of the invention also provides a direct current change-over switch which is arranged in the direct current transmission line and used for controlling the opening and closing of the direct current transmission line; fig. 5 is a circuit diagram of a dc converter switch according to an embodiment of the present invention, and referring to fig. 5, the dc converter switch includes a breaking circuit, an energy absorption circuit, and an oscillation circuit with parasitic parameters according to any of the above embodiments.
The breaking circuit, the energy absorption circuit and the oscillation circuit are connected in parallel; the energy absorption loop comprises a lightning arrester ZnO, and the on-off loop comprises a circuit breaker CB connected to the direct current transmission line. The oscillation circuit containing the parasitic parameters comprises a capacitance unit Cx formed by connecting a plurality of capacitors in series and parallel, and an inductance unit L and a damping resistance unit R which are connected with the capacitance unit Cx in series. The oscillation circuit containing the parasitic parameters is used for generating oscillation alternating current, and the oscillation alternating current is superposed in direct current of the direct current transmission line I to generate a current zero crossing point for the disconnection circuit to be disconnected; and the lightning arrester ZnO in the energy absorption loop is used for absorbing and discharging electric energy in the loop when the voltage at two ends of the capacitance unit Cx in the oscillation loop reaches rated voltage, so that the current on the direct current transmission line I is reduced to zero, and the disconnection of the direct current transmission line is completed.
Specifically, the switching-on and switching-off process of the direct current change-over switch is mainly divided into three parts: the current forced zero-crossing stage, the fracture medium recovery stage and the arrester action energy absorption stage. Taking a passive dc transfer switch as an example, after the dc transfer switch receives a command to turn on/off the current, the switch S of the oscillating circuit1The oscillating circuit is connected in parallel at two ends of the open-close circuit, then the circuit breaker CB direct current of the open-close circuit carries out arc discharge, and the arc voltage is applied to the oscillating circuitThe capacitor unit Cx is charged quickly, the arc voltage cannot be kept at a fixed value due to unstable and jumping of the arc, and a back-and-forth charging and discharging process is generated between the arc and the capacitor due to resonance of the inductor, the capacitor and the resistor in the oscillating circuit, the oscillating alternating current is generated in the process and is superposed on the direct current to create a current zero crossing point, the arc is extinguished, and the current is transferred from the open circuit to the oscillating circuit, so that the first stage, namely the current zero crossing forcing stage, is completed. After the electric arc is extinguished, the two ends of the circuit breaker CB enter a medium recovery stage, at the moment, the energy generated in the arc burning process is not released, so that the energy can be converted into recovery voltage to be applied to the two ends of the capacitor, and the electric arc can not be reignited only when the medium recovery voltage speed of the contact gap of the circuit breaker CB is greater than the recovery voltage speed of the electric arc, which is a second stage, namely a fracture medium recovery stage. When the voltage at two ends of the capacitor in the oscillation circuit reaches the rated voltage of the energy absorption circuit arrester ZnO, the arrester ZnO acts to absorb and discharge huge energy in the circuit, the voltage at two ends of the CB contact of the circuit breaker is limited within a controllable range, the current is rapidly reduced to zero, the disconnection is completed, and the ZnO energy absorption action stage of the arrester is the stage of the energy absorption action of the arrester ZnO.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims (10)

1. A tank circuit with parasitic parameters, comprising:
the capacitance unit comprises a plurality of oscillation branches, and the oscillation branches are connected in parallel; each oscillation branch comprises a plurality of capacitors connected in series; each capacitor comprises parasitic parameters including parasitic inductance and parasitic resistance;
the inductor unit, the damping resistance unit and the capacitor unit are connected in series.
2. The tank circuit with parasitic parameters of claim 1, wherein said capacitive unit comprises a first oscillating branch, a second oscillating branch, a third oscillating branch, a fourth oscillating branch, a fifth oscillating branch and a sixth oscillating branch;
the first oscillation branch comprises a first capacitor and a fourth capacitor which are connected in series; the first capacitor comprises parasitic parameters including a first parasitic inductance and a first parasitic resistance; the parasitic parameters contained in the fourth capacitor comprise a fourth parasitic inductance and a fourth parasitic resistance;
the second oscillation branch comprises a second capacitor and a fifth capacitor which are connected in series; the parasitic parameters contained in the second capacitor comprise a second parasitic inductance and a second parasitic resistance; parasitic parameters contained in the fifth capacitor comprise a fifth parasitic inductor and a fifth parasitic resistor;
the third oscillation branch comprises a third capacitor and a sixth capacitor which are connected in series; the parasitic parameters contained in the third capacitor comprise a third parasitic inductance and a third parasitic resistance; parasitic parameters contained in the sixth capacitor comprise a sixth parasitic inductor and a sixth parasitic resistor;
the fourth oscillation branch comprises a seventh capacitor and a tenth capacitor which are connected in series; the parasitic parameters contained in the seventh capacitor comprise a seventh parasitic inductor and a seventh parasitic resistor; the parasitic parameters contained in the tenth capacitor comprise a tenth parasitic inductance and a tenth parasitic resistance;
the fifth oscillation branch comprises an eighth capacitor and an eleventh capacitor which are connected in series; parasitic parameters contained in the eighth capacitor comprise an eighth parasitic inductor and an eighth parasitic resistor; the eleventh capacitor comprises parasitic parameters including an eleventh parasitic inductance and an eleventh parasitic resistance;
the sixth oscillation branch comprises a ninth capacitor and a twelfth capacitor which are connected in series; parasitic parameters contained in the ninth capacitor comprise a ninth parasitic inductor and a ninth parasitic resistor; the twelfth capacitor has parasitic parameters including a twelfth parasitic inductance and a twelfth parasitic resistance.
3. The parasitic parameter included tank of claim 2,
the common connecting end of the second capacitor and the fifth capacitor is electrically connected with the common connecting end of the third capacitor and the sixth capacitor;
and the common connection end of the eighth capacitor and the eleventh capacitor is electrically connected with the common connection end of the ninth capacitor and the twelfth capacitor.
4. The tank circuit with parasitic parameters of claim 2, wherein the first, second, third, fourth, fifth and sixth oscillating branches have equal capacitance in series.
5. The tank circuit with parasitic parameters of claim 2, wherein the first parasitic inductance, the second parasitic inductance, the third parasitic inductance, the fourth parasitic inductance, the fifth parasitic inductance, the sixth parasitic inductance, the seventh parasitic inductance, the eighth parasitic inductance, the ninth parasitic inductance, the tenth parasitic inductance, the eleventh parasitic inductance, and the twelfth parasitic inductance are not completely the same;
the first parasitic resistor, the second parasitic resistor, the third parasitic resistor, the fourth parasitic resistor, the fifth parasitic resistor, the sixth parasitic resistor, the seventh parasitic resistor, the eighth parasitic resistor, the ninth parasitic resistor, the tenth parasitic resistor, the eleventh parasitic resistor and the twelfth parasitic resistor are not completely the same.
6. The tank circuit with parasitic parameters of claim 2, wherein the capacitor unit, the inductor unit and the damping resistor unit are connected in series and then connected in parallel to two ends of the open circuit of the dc switch to be connected in series in the dc power transmission system.
7. The parasitic parameter-containing tank circuit of claim 6, wherein when the open circuit of the dc converter switch is opened, the capacitor unit, the inductor unit and the damping resistor unit resonate to generate an oscillating ac power, and the oscillating ac power is determined based on:
Figure FDA0003157776040000031
wherein, UC+UL+UR＝U，UCIs the voltage across the capacitor unit, ULIs the voltage across the inductive element, URIs the voltage across the damping resistance unit; u is the total voltage provided for the oscillation circuit when the open circuit of the direct current change-over switch is disconnected;
Z＝Z0+R+sL；Z0the total impedance of each capacitor in the capacitor unit and the parasitic inductance and the parasitic resistance contained in the capacitor unit, R is a damping resistance, sL is the inductive reactance of the inductance under the pull-type transformation, and Z is the total impedance of the oscillating circuit.
8. A direct current change-over switch is characterized in that the direct current change-over switch is arranged in a direct current transmission line and used for controlling the opening and closing of the direct current transmission line; comprising a circuit breaker, an energy absorption circuit and a tank circuit according to any of claims 1-7 containing parasitic parameters.
9. The dc transfer switch of claim 8, wherein the open circuit, the energy absorption circuit, and the tank circuit are connected in parallel;
the oscillating circuit is used for generating oscillating alternating current and superposing the oscillating alternating current in direct current of the direct current transmission line to generate a current zero crossing point for the on-off circuit to be switched off;
the energy absorption loop is used for absorbing and discharging electric energy in the loop when the voltage at two ends of the capacitor unit in the oscillation loop reaches the rated voltage of the action of the energy absorption loop lightning arrester, so that the current on the direct current transmission line is reduced to zero, and the disconnection of the direct current transmission line is completed.
10. The dc transfer switch of claim 8, wherein the energy absorption circuit comprises a surge arrester and the disconnect circuit comprises a circuit breaker connected to the dc power line.
CN202110782810.7A 2021-07-12 2021-07-12 Oscillating circuit containing parasitic parameters and direct current change-over switch Pending CN113507096A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114740243A (en) * 2022-04-25 2022-07-12 西南交通大学 Shock wave position and waveform detector based on parallel capacitor array
CN114812791A (en) * 2022-04-25 2022-07-29 西南交通大学 Shock wave position and waveform sensor based on parallel resistor array

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114740243A (en) * 2022-04-25 2022-07-12 西南交通大学 Shock wave position and waveform detector based on parallel capacitor array
CN114812791A (en) * 2022-04-25 2022-07-29 西南交通大学 Shock wave position and waveform sensor based on parallel resistor array
CN114812791B (en) * 2022-04-25 2024-01-30 西南交通大学 Shock wave position and waveform sensor based on parallel resistor array

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