CN116683381B - Electric heating ice melting prevention method of flexible traction power supply system - Google Patents
Electric heating ice melting prevention method of flexible traction power supply system Download PDFInfo
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Abstract
The invention discloses an electrothermal ice melting prevention method of a flexible traction power supply system, which is designed according to the ice coating states of contact networks with different degrees: when the ice coating degree is the most serious, the locomotive leaves the network, and the cascade inverters of the two substations are utilized to output low voltages with opposite phases, so that a large current flows on the contact network to melt ice; when the icing degree is light, adding a self-adaptive virtual impedance ring in voltage-current double closed-loop control of the inverter, and changing two output powers to realize light anti-icing; when the icing degree is heavy, the frequency-doubling voltage with opposite phases is output through the power frequency voltage output by the two transformers, so that the frequency-doubling current flows through the contact network and is overlapped with the fundamental frequency current for locomotive operation, and heavy anti-icing is realized. The problems that the traditional electric heating ice melting prevention method is limited by a traction power supply system structure, additional power electronic devices are added, and ice melting prevention under different environmental conditions and traction network ice covering degree is lacking are solved.
Description
Technical Field
The invention relates to the field of traction power supply, in particular to an electrothermal ice melting prevention method of a flexible traction power supply system.
Background
At present, the existing railway traction power supply system in China mostly adopts a three-phase and two-phase traction power supply mode, and the adopted partition power supply mode has a plurality of problems which are difficult to solve and mainly comprises the following steps: (1) electric energy quality problem: electromagnetic coupling exists among the traction power supply system, the locomotive and the three-phase power system, and the quality problems of reactive power, harmonic waves and other electric energy generated by the locomotive can be transmitted into the traction power supply system through the electromagnetic coupling relation, so that the normal operation of the system is endangered; (2) phase transition problem: the electric split phase structure is complex, the reliability is poor, the locomotive over-current split phase needs to run at a reduced speed, and particularly, the locomotive is often caused to stop under severe environmental conditions and long ramp intervals, so that inconvenience is brought to railway operation planning; (3) Power supply capability problem: the existence of the electric split phase causes great difficulty in cross-region power supply, and a main traction transformer and a standby traction transformer arranged in the substation form great capacity waste. Besides, the railway traction network ice coating threatens the safe operation of a railway traction power supply system and traction load thereof, and some sudden ice disasters and icing events lead the railway traction network ice melting method to be more urgent.
However, the electrothermal ice melting prevention method of the traditional traction power supply system is limited by the structure of the traditional traction power supply system, and an additional power electronic device is added, so that the ice melting prevention problem under different environmental conditions and the ice covering degree of the traction network is not solved, and the electrothermal ice melting prevention method is only suitable for a single ice covering degree and can influence the long-distance stable operation of traction load.
Disclosure of Invention
Aiming at the defects in the prior art, the electrothermal ice melting prevention method of the flexible traction power supply system solves the problems that the traditional electrothermal ice melting prevention method is limited by a traction power supply system structure, additional power electronic devices are added, and ice melting prevention under different environmental conditions and traction network ice coverage degrees is lacking, and meanwhile, the traditional electrothermal ice melting prevention method is only suitable for a single ice coverage degree and affects long-distance stable operation of traction load.
In order to achieve the aim of the invention, the invention adopts the following technical scheme: the utility model provides a flexible power supply system that pulls, includes flexible traction substation and traction network, flexible traction substation includes multi-winding step-down transformer and three-phase-single-phase converter, traction network includes contact net, rail and return line, the contact net includes ascending contact net and descending contact net, the rail includes ascending rail and descending rail, multi-winding step-down transformer's primary side is connected with the three-phase power grid, and its secondary is connected with the input side of three-phase-single-phase converter, the single-phase inverter port output of three-phase-single-phase converter cascades, and the single-phase power frequency alternating current of cascade output inserts the traction network.
The beneficial effect of above-mentioned scheme is: through the technical scheme, the traction power supply system is provided, and based on the traction power supply system, the invention designs a coordinated operation control method of the traction power supply system, so that stable operation of the traction power supply system is realized.
In addition, the invention adopts the following technical scheme: an electrothermal ice melting prevention method of a flexible traction power supply system comprises the following steps:
s1: the output of the multi-module single-phase inverter is equivalent to a single-phase inverter after being cascaded, and the output of the single-phase inverter is controlled by adopting a voltage-current double closed-loop control method and a PI controller;
s2: collecting output voltage u of single-phase inverter o And output inductor current i L Obtaining voltage and current quantity under dq coordinate system through coordinate transformation;
s3: the voltage and the current under the dq coordinate system are input into a PI controller to obtain a modulation signal u of the single-phase inverter sdq Stable control of output voltage of the single-phase inverter is realized;
s4: based on stable control of the output voltage of the single-phase inverter, the output voltage signal and the output current signal are transmitted to the integrated controller of the other flexible traction substation by using the integrated controller in the flexible traction substation, so that coordination control of the output power of the two flexible traction substations is realized;
s5: based on the coordinated control of the output power of the two flexible traction power substations, an anti-icing method suitable for different contact net icing degrees is designed, the anti-icing method is adopted when the locomotive is separated from the traction net, and the mild anti-icing method and the severe anti-icing method are respectively adopted for different situations when the locomotive runs online, so that the electrothermal anti-icing of the flexible traction power supply system is realized.
The beneficial effect of above-mentioned scheme is: according to the technical scheme, the light anti-icing method and the heavy anti-icing method are adopted when the train runs online, the ice melting method is adopted when the train runs off the net due to the severe traction net ice coating, so that the stable running of the flexible traction power supply system and the anti-ice melting of the railway overhead line system under different ice coating degrees are realized, the problems that the traditional electric heating anti-ice melting method is limited by the traction power supply system structure, additional power electronic devices are added, and the anti-ice melting under different environmental conditions and the traction net ice coating degrees are lacked are solved, and meanwhile, the problem that the traditional electric heating anti-ice melting method is only suitable for a single ice coating degree is solved, and the long-distance stable running of traction load is facilitated.
Further, the different contact net icing degrees in S5 specifically include the following cases:
(1) When 0A is less than or equal to the current I required by ice melting prevention h <458A, the icing degree is light, and a light anti-icing method is adopted;
(2) When 458A is less than or equal to the current I required for preventing ice melting h <700A, the icing degree is heavier, and a heavy anti-icing method is adopted;
(3) When 700A is less than or equal to the current I required for preventing ice melting h <Maximum allowable continuous current I of traction network max The ice coating degree is the most serious, and an ice melting method is adopted.
The beneficial effects of the above-mentioned further scheme are: by the technical scheme, the ice-covering degree is judged to be light or heavy according to the section of the current required by ice-melting prevention, so that the method is determined, and the ice-melting prevention problem under different environmental conditions and the ice-covering degree of the traction net is solved.
Further, the light anti-icing method comprises the following sub-steps:
a1: defining critical anti-icing current as a current minimum value for enabling the overhead line system of the anti-icing section not to cover ice;
a2: the virtual impedance loop is utilized to improve the voltage-current double closed-loop control, the dq component of the output current of the substation is coupled into the dq component of the reference voltage in the voltage-current double closed-loop control, and the formula is
Wherein, the liquid crystal display device comprises a liquid crystal display device,and->For the reference voltage value in the voltage loop control, +.>And->I is the voltage reference value in the virtual impedance loop Ld And i Lq For the output current of the substation, r x And l x Is a virtual impedance, ω is the angular frequency of the output voltage;
a3: based on the virtual impedance loop and the power transmission relation, the PI controller is utilized to process the difference value between the effective value of the output current of the substation and the defined critical anti-icing current, so as to realize the self-adaptive change of the virtual impedance and enable the output current of the substation to reach the critical anti-icing current, and the power transmission relation is that
Wherein P is 1 Active power output by traction substation in front of train R g1 And L g1 R is the line impedance of the anti-icing zone x1 And L x1 Is the virtual impedance of the anti-icing zone.
The beneficial effects of the above-mentioned further scheme are: according to the technical scheme, the mild anti-icing method is provided, a virtual impedance ring is added on the basis of voltage-current double closed-loop control, the dq component of the current output by the substation is coupled to the dq component of the reference voltage in the voltage-current double closed-loop control, and meanwhile, the PI controller is utilized to realize self-adaptive change of the virtual impedance.
Further, the heavy anti-icing method comprises the following sub-steps:
b1: the voltage control of the mild anti-icing method is used as fundamental frequency voltage control, and the frequency doubling voltage control with self-adaption is added, so that the respective control of the fundamental frequency voltage and the frequency doubling voltage is realized;
b2: based on fundamental frequency voltage control and frequency doubling voltage control, a cascade inverter is utilized to simultaneously output fundamental frequency voltage and frequency doubling voltage, and a modulation wave formula of the cascade inverter is as follows
u odq ＝u' od cosωt+u' oq sinωt+u” od cos2ωt+u” oq sin2ωt
Wherein u is odq Is superposition of fundamental frequency voltage and frequency doubling voltage, u' od And u' oq For fundamental frequency voltage u' od And u' oq The voltage is doubled, and t is time;
b3: and generating a double frequency current on the traction network by using the double frequency voltage, and superposing the double frequency current and the fundamental frequency current to enable the corresponding anti-icing current to flow on the contact network.
The beneficial effects of the above-mentioned further scheme are: according to the technical scheme, the heavy anti-icing method is provided, the frequency doubling voltage control is added on the basis that the light anti-icing method is the fundamental frequency voltage control, the fundamental frequency voltage and the frequency doubling voltage are simultaneously output through the cascade inverter, the frequency doubling current is further obtained, and the frequency doubling current and the fundamental frequency current are overlapped, so that heavy anti-icing is realized.
Further, the ice melting method includes using the flexible traction substation as ice melting equipment, outputting ice melting current to the traction network, and melting ice by using joule heat, and includes the following formula:
the output voltage and current formulas of the two flexible traction power transformers are
Wherein u is A And u B Respectively output voltages of two flexible traction power transformers, U A And U B Respectively the voltage amplitude phi A And phi B Respectively the phase angles of the voltages, the phase angle is the sign of the phase angle, i A And i B The current output by the two flexible traction transformers is respectively,I A and I B The current amplitudes are respectively indicated as the current amplitudes,and->The phase angles of the currents are respectively;
the apparent power output by the two flexible traction transformers is
Wherein S is A And S is B Apparent power, P, respectively output by two flexible traction transformers A And P B Active power respectively output by two flexible traction substations, Q A And Q B And the reactive power output by the two flexible traction transformers is respectively represented by j which is an imaginary unit.
The beneficial effects of the above-mentioned further scheme are: through the technical scheme, the ice melting method is provided, ice melting is realized by outputting ice melting current to the traction network and utilizing generated Joule heat.
Drawings
Fig. 1 is a schematic structural diagram of a flexible traction power supply system.
FIG. 2 is a flow chart of an electrothermal ice-melting prevention method of a flexible traction power supply system.
Fig. 3 is a schematic diagram of single-phase cascaded inverter output voltage control.
Fig. 4 is a simplified control block diagram of a single-phase inverter incorporating virtual impedance in a light anti-icing process.
Fig. 5 is a block diagram of adaptive virtual impedance control in a light anti-icing process.
FIG. 6 is a schematic diagram of the output voltage of the flexible traction substation in the heavy anti-icing method.
FIG. 7 is a simplified circuit diagram of a flexible traction power supply system for fundamental frequency voltage and frequency doubling voltage in a heavy anti-icing method.
FIG. 8 is a control block diagram of superimposed doubling current in the heavy anti-icing method.
Fig. 9 is a schematic diagram of an equivalent circuit of a flexible traction power supply system in the ice melting method.
FIG. 10 is a schematic diagram of the output voltage of the flexible traction substation in the ice melting method.
Fig. 11 is a simulation diagram of a catenary current waveform in the ice melting method.
Detailed Description
The invention will be further described with reference to the drawings and specific examples.
Embodiment 1, as shown in fig. 1, a flexible traction power supply system comprises a flexible traction substation and a traction network, wherein the flexible traction substation comprises a multi-winding step-down transformer and a three-phase-single-phase converter, the traction network comprises an overhead contact line, steel rails and a return line, the overhead contact line comprises an uplink overhead contact line and a downlink overhead contact line, the steel rails comprise an uplink steel rail and a downlink steel rail, the primary side of the multi-winding step-down transformer is connected with a three-phase power grid, the secondary side of the multi-winding step-down transformer is connected with the input side of the three-phase-single-phase converter, the output of the port of the single-phase inverter is cascaded, and the single-phase power frequency alternating current of the cascaded output is connected with the traction network.
Embodiment 2, as shown in fig. 2, an electrothermal ice melting prevention method of a flexible traction power supply system is implemented based on the flexible traction power supply system, and includes the following steps:
s1: the output of the multi-module single-phase inverter is equivalent to a single-phase inverter after being cascaded, and the output of the single-phase inverter is controlled by adopting a voltage-current double closed-loop control method and a PI controller;
s2: collecting output voltage u of single-phase inverter o And output inductor current i L Obtaining voltage and current quantity under dq coordinate system through coordinate transformation;
s3: the voltage and the current under the dq coordinate system are input into a PI controller to obtain a modulation signal u of the single-phase inverter sdq Stable control of output voltage of the single-phase inverter is realized;
s4: based on stable control of the output voltage of the single-phase inverter, the output voltage signal and the output current signal are transmitted to the integrated controller of the other flexible traction substation by using the integrated controller in the flexible traction substation, so that coordination control of the output power of the two flexible traction substations is realized;
s5: based on the coordinated control of the output power of the two flexible traction power substations, an anti-icing method suitable for different contact net icing degrees is designed, the anti-icing method is adopted when the locomotive is separated from the traction net, and the mild anti-icing method and the severe anti-icing method are respectively adopted for different situations when the locomotive runs online, so that the electrothermal anti-icing of the flexible traction power supply system is realized.
In one embodiment of the invention, the voltage u output by the inverter is acquired by a sensor o And inductor current i L Then coordinate transformation is carried out to obtain the quantity u under dq coordinate system od 、u oq 、i Ld And i Lq Input to the controller to obtain the modulation signal u of the inverter sdq Stable control of the output voltage of the inverter can be realized, and the control block diagram is shown in fig. 3, in the figure,and->Is the voltage reference value in the voltage loop control, +.>And->For the current reference value in the current loop control, ω represents the angular frequency of the output voltage, L n 、C n The output filter inductance and the output filter capacitance of the single-phase inverter are respectively shown.
The stable operation of the flexible traction power supply system depends on coordination control among power substations. In this embodiment, each substation is provided with a comprehensive controller, and a signal transmission optical fiber and a current source type power line are arranged between the two substations, and the power line can eliminate signal phase offset caused by impedance of a communication line.
The integrated controller can transmit signals of output voltage and inductance current to the integrated controllers of other power substations through a signal transmission line. During normal stable coordination control, the power output of the two flexible traction substations is determined by the position of the locomotive, and the locomotive follows the principle of 'near output', namely, the power output of the substation where the locomotive approaches is larger and the power output is more; in the anti-ice-melting state, the power output by the traction substation is also adjustable and controllable.
The icing degree of different contact networks in S5 specifically comprises the following conditions:
(1) When 0A is less than or equal to the current I required by ice melting prevention h <458A, the icing degree is light, and a light anti-icing method is adopted;
(2) When 458A is less than or equal to the current I required for preventing ice melting h <700A, the icing degree is heavier, and a heavy anti-icing method is adopted;
(3) When 700A is less than or equal to the current I required for preventing ice melting h <Maximum allowable continuous current I of traction network max The ice coating degree is the most serious, and an ice melting method is adopted.
The mild anti-icing method comprises the following sub-steps:
a1: defining critical anti-icing current as a current minimum value for enabling the overhead line system of the anti-icing section not to cover ice;
a2: the virtual impedance loop is utilized to improve the voltage-current double closed-loop control, the dq component of the output current of the substation is coupled into the dq component of the reference voltage in the voltage-current double closed-loop control, and the formula is
Wherein, the liquid crystal display device comprises a liquid crystal display device,and->For the reference voltage value in the voltage loop control, +.>And->I is the voltage reference value in the virtual impedance loop Ld And i Lq For the output current of the substation, r x And l x Is a virtual impedance, ω is the angular frequency of the output voltage;
a3: based on the virtual impedance loop and the power transmission relation, the PI controller is utilized to process the difference value between the effective value of the output current of the substation and the defined critical anti-icing current, so as to realize the self-adaptive change of the virtual impedance and enable the output current of the substation to reach the critical anti-icing current, and the power transmission relation is that
Wherein P is 1 Active power output by traction substation in front of train R g1 And L g1 R is the line impedance of the anti-icing zone x1 And L x1 Is the virtual impedance of the anti-icing zone.
The method changes the amplitude and the phase of the output voltage of the substation based on the virtual impedance control method, so that the effective value of the output current of the traction substation in the advancing direction is equal to the critical anti-icing current, and the overhead line in the advancing direction of the locomotive has enough anti-icing current without icing, thereby ensuring the safe advancing of the locomotive.
In one embodiment of the invention, a simplified control block diagram of a single-phase inverter with virtual impedance is shown in FIG. 4, voltage-current double-loop control with inductor current feedforward is adopted, and the line impedance and the virtual impedance jointly determine the power output by the inverter according to a power transmission relation, R g1 And L g1 Because of natural changes with locomotive movement, if the locomotive does not provide locomotive position, the virtual impedance value used to correct the impedance needs to be based on R g1 And L g1 And the change is carried out, so that the goal of distributing the power according to the anti-icing current requirement is achieved. In order to achieve the aim, the method adds a proportional integral link to process the output of the substationThe difference value between the effective value of the current and the given critical anti-icing current is used for realizing the self-adaptive change of the virtual impedance, thereby realizing the aim that the output current of the substation reaches the anti-icing requirement. As shown in fig. 5, a control block diagram of the adaptive virtual impedance control is shown, where i o Is the current output by the power substation, the effective value of which is I orms A representation; i LJ Is critical anti-icing current, determined by environmental factors. k (k) axp Is the proportionality coefficient of the self-adaptive virtual impedance ring, k axi Is the integral coefficient of the adaptive virtual impedance loop, Z axd Adaptive virtual impedance, Z, as the active component axq Is the adaptive virtual impedance of the reactive component.
The heavy anti-icing method comprises the following substeps:
b1: the voltage control of the mild anti-icing method is used as fundamental frequency voltage control, and the frequency doubling voltage control with self-adaption is added, so that the respective control of the fundamental frequency voltage and the frequency doubling voltage is realized;
b2: based on fundamental frequency voltage control and frequency doubling voltage control, a cascade inverter is utilized to simultaneously output fundamental frequency voltage and frequency doubling voltage, and a modulation wave formula of the cascade inverter is as follows
u odq ＝u' od cosωt+u' oq sinωt+u” od cos2ωt+u” oq sin2ωt
Wherein u is odq Is superposition of fundamental frequency voltage and frequency doubling voltage, u' od And u' oq For fundamental frequency voltage u' od And u' oq The voltage is doubled, and t is time;
b3: and generating a double frequency current on the traction network by using the double frequency voltage, and superposing the double frequency current and the fundamental frequency current to enable the corresponding anti-icing current to flow on the contact network.
In one embodiment of the invention, when the locomotive is in an operation state and the meteorological conditions are very bad, but the current required by the locomotive itself to work is smaller than the critical anti-icing current in the light anti-icing method, the heavy anti-icing method is adopted, the cascade inverters of the two power stations are controlled to output fundamental frequency voltage, and simultaneously, the voltage of double frequency is output, the voltage of double frequency generates the current of double frequency on the traction network, and the current of double frequency is overlapped with the current of fundamental frequency, so that enough anti-icing current flows on the contact network, and the schematic diagram is shown in fig. 6.
A simplified circuit model of the flexible traction power supply system of the fundamental frequency voltage and the frequency doubling voltage is shown in fig. 7. U 'in the figure' 1 And u' 1 For fundamental frequency component and frequency doubling component of output voltage of substation 1, u' 2 And u' 2 I 'for fundamental frequency component and frequency doubling component of output voltage of substation 2' 1 And i' 1 I 'for the fundamental frequency component and the frequency doubling component of the output current of the substation 1' 2 And i' 2 The fundamental frequency component and the frequency doubling component of the current are output for the substation 2.
The influence of higher harmonic on the system is not considered, and the expression of the output voltage of the substation 1 at the traction network side is assumed to be
u 1 (t)＝u′ 1 (t)+u″ 1 (t)＝U′ 1d cosωt+U′ 1q sinωt+U″ 1d cos2ωt+U″ 1q sin2ωt
Wherein U 'is' 1d And U' 1q As fundamental frequency voltage component u' 1 Voltage in dq coordinate system, U' 1d And U' 1q For frequency-doubled voltage component u' 1 Voltage quantity in dq coordinate system.
In order to make the inverter output the fundamental frequency voltage and the frequency doubling voltage simultaneously, the fundamental frequency voltage and the frequency doubling voltage need to be controlled respectively.
The cos omega t is multiplied on both sides of the output voltage at the traction network side, and the following can be obtained:
multiplying sin omega t on both sides of the traction network side output voltage to obtain:
according to the above, the AC component is filtered by a low-pass filter to obtain u 1 On the baseActive and reactive components in the frequency control. Similarly, the grid-side current can be separated using the method described above.
Multiplying cos2 ωt on both sides of the traction network side output voltage, yields:
multiplying both sides of the traction network side output voltage by sin2 ωt to obtain:
the alternating current component is filtered by a low-pass filter to obtain u 2 Active and reactive components in secondary frequency control.
The design of the voltage-current double closed-loop control strategy with feedforward decoupling added under the dq coordinate system can obtain a control block diagram of the heavy anti-icing control strategy as shown in fig. 8. Wherein the frequency in the frequency doubling control loop is 2ω.
The ice melting method comprises the steps of taking a flexible traction substation as ice melting equipment, outputting ice melting current to a traction network, and melting ice by utilizing Joule heat, wherein the ice melting method comprises the following formula:
the output voltage and current formulas of the two flexible traction power transformers are
Wherein u is A And u B Respectively output voltages of two flexible traction power transformers, U A And U B Respectively the voltage amplitude phi A And phi B Respectively the phase angles of the voltages, the phase angle is the sign of the phase angle, i A And i B Two flexible traction partsCurrent output by the power substation, I A And I B The current amplitudes are respectively indicated as the current amplitudes,and->The phase angles of the currents are respectively;
the apparent power output by the two flexible traction transformers is
Wherein S is A And S is B Apparent power, P, respectively output by two flexible traction transformers A And P B Active power respectively output by two flexible traction substations, Q A And Q B And the reactive power output by the two flexible traction transformers is respectively represented by j which is an imaginary unit.
In one embodiment of the invention, when the weather conditions are very severe, the locomotive is off-grid for safe operation. The ice melting method takes the flexible traction substation as ice melting equipment, utilizes the flexible traction substation to inject ice melting current into the traction network, and utilizes the joule heat of the ice melting current to melt ice. In the method, only two transformation houses and a traction net form an ice melting loop, the equivalent circuit is shown in figure 9, wherein u A ，u B Respectively output voltages of two transformers, i A ，i B Respectively, the current output by the two transformers, z l ＝r l +jωL 1 The unit length of the traction network impedance is that omega is the angular frequency of alternating voltage, and L is the length of the traction network between two transformer stations.
In the electrothermal ice melting method of the contact net of the flexible traction power supply system, as shown in fig. 10, two voltages with the same output amplitude and pi phase difference are adopted, and the traction net is used as a load. At the moment, the active power output by the two power substations is equal, and no energy is returned to the respective power grids. Fig. 11 is a current waveform of the overhead contact line in the ice melting method, and it can be seen that the effective value of the current flowing through the overhead contact line between the two posts reaches 750A, so as to meet the ice melting current requirement.
The invention designs a corresponding ice melting prevention method and an implementation method aiming at three contact net ice coating states with different degrees. When the ice coating degree is the most serious, the locomotive leaves the network, and the cascade inverters of the two substations are utilized to output low voltages with opposite phases, so that a large current flows on the contact network to melt ice; the vehicle runs on line when the icing degree is light, a self-adaptive virtual impedance ring is designed and added in the voltage-current double closed-loop control of the inverter, two output powers are changed, the anti-icing interval is ensured to flow through enough anti-icing current, and light anti-icing is realized; when the icing degree is heavy, the frequency-doubling voltage with opposite phases is output through the power frequency voltage output by the two power transformers, so that the frequency-doubling current flows through the contact network, and the frequency-doubling current is overlapped with the fundamental frequency current for the locomotive to work, so that enough anti-icing current flows through an anti-icing zone to realize heavy anti-icing. The invention realizes the stable operation of the flexible traction power supply system and the ice melting prevention of the railway contact network under different ice coating degrees.
Those of ordinary skill in the art will recognize that the embodiments described herein are for the purpose of aiding the reader in understanding the principles of the present invention and should be understood that the scope of the invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific modifications and combinations from the teachings of the present disclosure without departing from the spirit of the invention, and such modifications and combinations are still within the scope of the invention.
Claims (3)
1. The electric heating ice melting prevention method of the flexible traction power supply system is realized based on the flexible traction power supply system, the flexible traction power supply system comprises a flexible traction substation and a traction network, the flexible traction substation comprises a multi-winding step-down transformer and a three-phase-single-phase converter, the traction network comprises a contact network, a steel rail and a return line, the contact network comprises an uplink contact network and a downlink contact network, the steel rail comprises an uplink steel rail and a downlink steel rail, the primary side of the multi-winding step-down transformer is connected with a three-phase power grid, the secondary side of the multi-winding step-down transformer is connected with the input side of the three-phase-single-phase converter, the output of a port of the single-phase-inverter is cascaded, and single-phase power frequency alternating current output by cascading is connected with the traction network;
the electric heating ice melting prevention method of the flexible traction power supply system is characterized by comprising the following steps of:
s1: the output of the multi-module single-phase inverter is equivalent to a single-phase inverter after being cascaded, and the output of the single-phase inverter is controlled by adopting a voltage-current double closed-loop control method and a PI controller;
s2: collecting output voltage u of single-phase inverter o And output inductor current i L Obtaining voltage and current quantity under dq coordinate system through coordinate transformation;
s3: the voltage and the current under the dq coordinate system are input into a PI controller to obtain a modulation signal u of the single-phase inverter sdq Stable control of output voltage of the single-phase inverter is realized;
s4: based on stable control of the output voltage of the single-phase inverter, the output voltage signal and the output current signal are transmitted to the integrated controller of the other flexible traction substation by using the integrated controller in the flexible traction substation, so that coordination control of the output power of the two flexible traction substations is realized;
s5: based on the coordinated control of the output power of the two flexible traction substations, an anti-icing method applicable to different contact net icing degrees is designed, the anti-icing method is adopted when the locomotive is separated from the traction net, and a mild anti-icing method and a severe anti-icing method are respectively adopted for different situations when the locomotive runs online, so that the electrothermal anti-icing of the flexible traction power supply system is realized;
the different contact net icing degrees in S5 specifically comprise the following conditions:
(1) When 0A is less than or equal to the current I required by ice melting prevention h <458A, the icing degree is light, and a light anti-icing method is adopted;
(2) When 458A is less than or equal to the current I required for preventing ice melting h <700A, the icing degree is heavier, and a heavy anti-icing method is adopted;
(3) When 700A is less than or equal to the current I required for preventing ice melting h <Maximum allowable continuous current I of traction network max ThenThe ice coating degree is the most serious, and an ice melting method is adopted;
the light anti-icing method comprises the following substeps:
a1: defining critical anti-icing current as a current minimum value for enabling the overhead line system of the anti-icing section not to cover ice;
a2: the virtual impedance loop is utilized to improve the voltage-current double closed-loop control, the dq component of the output current of the substation is coupled into the dq component of the reference voltage in the voltage-current double closed-loop control, and the formula is
Wherein, the liquid crystal display device comprises a liquid crystal display device,and->For the reference voltage value in the voltage loop control, +.>And->I is the voltage reference value in the virtual impedance loop Ld And i Lq For the output current of the substation, r x And l x Is a virtual impedance, ω is the angular frequency of the output voltage;
a3: based on the virtual impedance loop and the power transmission relation, the PI controller is utilized to process the difference value between the effective value of the output current of the substation and the defined critical anti-icing current, so as to realize the self-adaptive change of the virtual impedance and enable the output current of the substation to reach the critical anti-icing current, and the power transmission relation is that
Wherein P is 1 Active power output by traction substation in front of train R g1 And L g1 R is the line impedance of the anti-icing zone x1 And L x1 Is the virtual impedance of the anti-icing zone.
2. The electrothermal ice-melting prevention method of a flexible traction power supply system of claim 1, wherein the heavy ice-preventing method comprises the sub-steps of:
b1: the voltage control of the mild anti-icing method is used as fundamental frequency voltage control, and the frequency doubling voltage control with self-adaption is added, so that the respective control of the fundamental frequency voltage and the frequency doubling voltage is realized;
b2: based on fundamental frequency voltage control and frequency doubling voltage control, a cascade inverter is utilized to simultaneously output fundamental frequency voltage and frequency doubling voltage, and a modulation wave formula of the cascade inverter is as follows
u odq ＝u′ od cosωt+u′ oq sinωt+u″ od cos2ωt+u″ oq sin2ωt
Wherein u is odq Is superposition of fundamental frequency voltage and frequency doubling voltage, u' od And u' oq Is fundamental frequency voltage, u od And u oq The voltage is doubled, and t is time;
b3: and generating a double frequency current on the traction network by using the double frequency voltage, and superposing the double frequency current and the fundamental frequency current to enable the corresponding anti-icing current to flow on the contact network.
3. The method for preventing ice melting by electric heating of a flexible traction power supply system according to claim 2, wherein the method for melting ice comprises outputting ice melting current to a traction network by using a flexible traction substation as ice melting equipment, and melting ice by using joule heat, comprising the following formula:
the output voltage and current formulas of the two flexible traction power transformers are
Wherein u is A And u B Respectively output voltages of two flexible traction power transformers, U A And U B Respectively the voltage amplitude phi A And phi B Respectively the phase angles of the voltages, the phase angle is the sign of the phase angle, i A And i B Respectively outputting currents of two flexible traction power transformers, I A And I B The current amplitudes are respectively indicated as the current amplitudes,and->The phase angles of the currents are respectively;
the apparent power output by the two flexible traction transformers is
Wherein S is A And S is B Apparent power, P, respectively output by two flexible traction transformers A And P B Active power respectively output by two flexible traction substations, Q A And Q B And the reactive power output by the two flexible traction transformers is respectively represented by j which is an imaginary unit.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102431468A (en) * | 2011-10-25 | 2012-05-02 | 成都交大许继电气有限责任公司 | Icing preventing and ice melting method for high speed railway and system for realizing method |
| RU157607U1 (en) * | 2015-05-28 | 2015-12-10 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Магнитогорский государственный технический университет им. Г.И. Носова" | AC TRACTION ELECTRICITY SUPPLY SYSTEM |
| CN114421462A (en) * | 2022-01-21 | 2022-04-29 | 西南交通大学 | Stable operation control method of flexible traction power supply system |
| CN114498577A (en) * | 2021-12-21 | 2022-05-13 | 西南交通大学 | Through flexible traction substation structure and protection configuration method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102431468A (en) * | 2011-10-25 | 2012-05-02 | 成都交大许继电气有限责任公司 | Icing preventing and ice melting method for high speed railway and system for realizing method |
| RU157607U1 (en) * | 2015-05-28 | 2015-12-10 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Магнитогорский государственный технический университет им. Г.И. Носова" | AC TRACTION ELECTRICITY SUPPLY SYSTEM |
| CN114498577A (en) * | 2021-12-21 | 2022-05-13 | 西南交通大学 | Through flexible traction substation structure and protection configuration method thereof |
| CN114421462A (en) * | 2022-01-21 | 2022-04-29 | 西南交通大学 | Stable operation control method of flexible traction power supply system |
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