CN114421462A - Stable operation control method of flexible traction power supply system - Google Patents
Stable operation control method of flexible traction power supply system Download PDFInfo
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- 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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60M—POWER SUPPLY LINES, AND DEVICES ALONG RAILS, FOR ELECTRICALLY- PROPELLED VEHICLES
- B60M3/00—Feeding power to supply lines in contact with collector on vehicles; Arrangements for consuming regenerative power
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- 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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
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- 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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/40—Synchronising a generator for connection to a network or to another generator
- H02J3/44—Synchronising a generator for connection to a network or to another generator with means for ensuring correct phase sequence
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Abstract
The invention introduces a stable operation control method of a flexible traction power supply system, which comprises the following steps: s1, firstly, selecting a flexible traction transformer as a main station and connecting the flexible traction transformer to a traction network; s2, selecting other flexible traction transformers as slaves, and realizing phase synchronization tracking of the slave traction network side through a phase synchronization module to ensure that the slave traction networks can be stably connected to the traction network; s3, setting a power control module, and acquiring a voltage reference value usref(ii) a S4, controlling the flexible traction transformer to output stably; and S5, setting a power coordination control module to realize that the network voltage at the traction network side is properly increased or reduced along with the running condition of the train. The invention ensures the flexible traction transformerThe output voltage is controllable, the through power supply requirement of the flexible traction power supply system is met, and the full-line through traction power supply is realized; meanwhile, the loss of the flexible traction power supply system on the traction network side is kept at a small level, and the stable operation of the flexible traction power supply system after any flexible traction transformer is disconnected is ensured.
Description
Technical Field
The invention belongs to the field of power supply control, and particularly relates to a stable operation control method of a flexible traction power supply system.
Background
At present, the current railway traction power supply system of various countries in the world widely adopts a three-phase-two-phase power supply mode. The traction substation gets electricity from a three-phase power grid, and the electricity is output by two power supply arms after being subjected to voltage reduction through a traction transformer to supply power for the traction grid. However, because the voltage phase, amplitude and frequency between the two power supply arms and between the power substations are difficult to be completely consistent, the two power supply arms and between the power substations must be provided with electric phase splitting, and the power supply is divided into zones.
The subarea power supply has the problem of parasitic which is difficult to solve, and has serious restrictions on the speed and the load capacity of the electric locomotive. Under the system structure, a close electromagnetic coupling relation exists between the traction power supply system and the traction network as well as between the traction load, so that the unbalance and impact of the traction load can be fed back to the three-phase power grid side through the traction substation, the power quality of the three-phase power grid is seriously influenced, and the power quality of the three-phase power grid is directly related to the normal operation of the traction power supply system and the traction load. The strong coupling relation in the traditional power supply mode seriously reduces the operation efficiency and quality of a traction power supply system, increases the treatment difficulty of the power quality in a three-phase power grid, and threatens the safe, stable and reliable operation of the electric locomotive and the traction power supply system.
Chinese patent CN113224762A discloses a long-distance through flexible traction power supply system and an optimization control method thereof, wherein the long-distance through flexible traction power supply system comprises a plurality of groups of power supply subsystems, the groups of power supply subsystems are electrically connected in a split-phase manner, each group of most power supply subsystems comprise a three-phase power grid, a plurality of traction substations, a plurality of circuit breakers and a traction network, the output ends of the plurality of traction substations are connected with the input ends of the plurality of circuit breakers in a one-to-one correspondence manner, the input ends of the plurality of traction substations are connected with the three-phase power grid, the output ends of the circuit breakers are connected with the traction network, and the traction network is used for supplying power to trains. The long-distance through flexible traction power supply system and the optimization control method thereof can realize long-distance electrification of the traction network and simultaneously keep the voltage of the traction network in the power supply area of the traction substation stable.
Chinese patent CN110931222A discloses a four-winding traction transformer device of a flexible traction power supply system, wherein a transformer TM4 includes four windings T1, T2, T3 and T4; the T1 winding is used as a high-voltage side of a transformer TM4, connected to a bus at the 35kV side of the traction substation in a three-phase delta-shaped connection mode; the winding of T2 is used as one of the low-voltage sides of a transformer TM4, adopts three-phase Y-shaped connection and is connected to the primary side of a rectifier device RN of the traction substation; the T3 winding is used as one of the low-voltage sides of the transformer TM4, connected to the primary side of a rectifier device RN of the traction substation by adopting three-phase delta connection; the winding of T4 is used as one of the low voltage sides of the TM4 transformer, and is connected to the primary side of a PCS bidirectional converter device of the traction substation by adopting a three-phase Y-shaped connection. The traction power supply system for the urban rail transit can realize that one transformer is used by the traction power supply system for the urban rail transit and can simultaneously supply power for the rectifier unit and the bidirectional converter device; the investment of transformer equipment can be saved, and the occupied area of the transformer in traction is reduced.
Although the scheme provides a power supply system optimization scheme, the problem of the electric energy quality of a traction power supply system is not completely solved, so that the problems of the electric energy quality of the traction power supply system, reduction and even elimination of an electric phase splitting device, realization of through type trans-regional power supply and solving of the problems of negative sequence, reactive power, harmonic wave and the like of the existing power supply system become more important.
Disclosure of Invention
In order to solve the problems, the existing grid-connected control strategy is improved, the flexible traction transformer can provide stable voltage for the traction network side, the voltage of the whole network is kept consistent, and the aim of communication is fulfilled; meanwhile, each flexible traction transformer can be stably connected and disconnected; the reasonable distribution of load power of different flexible traction transformers can be realized, the side loss of a traction network is kept small, and the efficient operation of a system is ensured; and further, the problem of the electric energy quality of a traction power supply system is solved, and an electric phase splitting device is reduced or even eliminated.
In order to achieve the effect, the invention designs a stable operation control method of the flexible traction power supply system.
A stable operation control method of a flexible traction power supply system comprises the following steps:
s1, firstly, selecting a flexible traction transformer as a main station, providing a standard reference voltage of 27.5kV/50Hz, and connecting the standard reference voltage to a traction network;
s2, selecting other flexible traction transformers as slaves, and realizing phase synchronization tracking of the slave traction network side through a phase synchronization module to ensure that the slave traction networks can be stably connected to the traction network;
s3, setting a power control module, and acquiring a voltage reference value usref；
S4, controlling the flexible traction transformer to output stably;
and S5, setting a power coordination control module to realize that the network voltage at the traction network side is properly increased or reduced along with the running condition of the train.
Preferably, the phase synchronization module in step S2 is completed by a single-phase-locked loop and a single-phase voltage coordinate system transformation module, and mainly includes:
s21, constructing virtual alpha and beta phases by using a single-phase voltage coordinate system transformation module, and acquiring alpha phase voltage and beta phase voltage;
s22 phase position omega of traction network side voltage obtained through single-phase-locked loopgt；
S23, and using the traction network side voltage phase obtained in S2Bit omegagt is used for carrying out Park conversion on the alpha and beta phase voltages of S21 to obtain usq。
Preferably, the single-phase voltage coordinate system transformation module in the step S21 adopts a 1/4 period delay algorithm to construct a virtual beta phase, that is, equation 1 is used, where equation 1 is
The angular frequency ω 02 pi f, f 50Hz, voltage Us＝27.5kV；usα，usβRespectively constructing virtual alpha phase voltage and virtual beta phase voltage, and j is an imaginary number sign.
Preferably, the phase ω of the traction network side obtained in the step S23 through the single-phase-locked loopgAfter t, converting the formula 1 into a dq coordinate system through Park, namely using a formula 2, wherein the formula 2 is:
said u issdAnd usqObtaining u as the voltage value under dq coordinate systemsqThe deviation from 0 is realized by a PI controllerg＝ω0And the synchronous tracking of the output phase of the flexible traction transformer to the network voltage phase at the side of the traction network is met.
Preferably, the power control module in the step S3 includes a reactive power-amplitude control module and an active power-frequency control module.
Preferably, the obtaining of the voltage reference value u in the step S3srefThe specific method comprises the following steps:
s61, collecting output voltage u of flexible traction transformersOutput current is；
S62, calculating to obtain output active power P and reactive power Q;
s63, obtaining a corresponding voltage reference value u by the flexible traction transformer according to the output power of the flexible traction transformer under the actual current taking condition of the trainsref。
Preferably, the step S4, which is to ensure stable output of the flexible traction transformer, is implemented by a voltage-current dual closed-loop control module. Reference value u obtained from S3srefObtaining corresponding reference value U through single-phase dq decouplingsdref、UsqrefThe realization method comprises the following steps:
wherein LPF represents a low pass filter.
Preferably, in the step S4, the output of the flexible traction transformer adopts an LC filter structure to obtain a control equation of the double closed loop of the voltage and the current after dq decoupling.
Preferably, in the step S5, the power coordination control module is specifically configured to adjust the power control module to give the amplitude reference value according to the train operation position.
Preferably, the power coordination control module gives a reference value of magnitude of
The module sets the automatic adjusting parameter va with the given value of the amplitude value
Wherein
C is a constant related to the characteristics of the system, and dist is the average distance between the train and the flexible traction transformer when the train operates.
The application has the advantages and effects as follows:
1. the stable operation control method suitable for the flexible traction power supply system ensures that the output voltage of the flexible traction transformer is controllable, meets the through power supply requirement of the flexible traction power supply system, and realizes full-line through traction power supply.
2. The power coordination control method suitable for the flexible traction power supply system can effectively achieve that the loss of the traction network side of the flexible traction power supply system is kept at a small level, and the system is guaranteed to operate friendly and stable.
3. The phase pre-synchronization control and the power control method are combined and applied to the flexible traction power supply system, synchronous communication among stations is not needed, and safe and stable grid connection and disconnection of the flexible traction transformer can be guaranteed. Meanwhile, the master station is provided with a whole set of control algorithm, so that the master station and the slave station can be randomly converted, and the stable operation of the system of the flexible traction power supply system after any flexible traction transformer is disconnected is ensured.
4. The flexible traction transformer used in the application can keep the output of the flexible traction transformer consistent according to control, so that the input sides of the three-phase power grid are relatively independent.
5. The flexible traction transformer output that this application used can provide the voltage that pulls the net stability, and a plurality of flexible traction transformers can realize getting rid of the purpose of electric split phase because its advantage controllable completely.
The foregoing description is only an overview of the technical solutions of the present application, so that the technical means of the present application can be more clearly understood and the present application can be implemented according to the content of the description, and in order to make the above and other objects, features and advantages of the present application more clearly understood, the following detailed description is made with reference to the preferred embodiments of the present application and the accompanying drawings.
The above and other objects, advantages and features of the present application will become more apparent to those skilled in the art from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.
FIG. 1 is a schematic structural diagram of a flexible traction power supply system according to the present invention;
FIG. 2 is a general schematic diagram of a stability control method according to the present invention;
FIG. 3 is a schematic diagram of a phase pre-synchronization module according to the present invention;
FIG. 4 is a schematic diagram of a voltage-current dual closed-loop control module according to the present invention;
FIG. 5 is a simulation diagram of the voltage on the traction network side when two flexible traction transformers provided by the present invention are operated synchronously;
FIG. 6 is a diagram of the relationship between the output power of two flexible traction transformers and the operation position of a locomotive according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. In the following description, specific details such as specific configurations and components are provided only to help the embodiments of the present application be fully understood. Accordingly, it will be apparent to those skilled in the art that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present application. In addition, descriptions of well-known functions and constructions are omitted in the embodiments for clarity and conciseness.
It should be appreciated that reference throughout this specification to "one embodiment" or "the embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Thus, the appearances of the phrase "one embodiment" or "the present embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
Further, the present application may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
The term "and/or" herein is merely an association describing an associated object, meaning that three relationships may exist, e.g., a and/or B, may mean: a exists alone, B exists alone, and A and B exist at the same time, and the term "/and" is used herein to describe another association object relationship, which means that two relationships may exist, for example, A/and B, may mean: a alone, and both a and B alone, and further, the character "/" in this document generally means that the former and latter associated objects are in an "or" relationship.
The term "at least one" herein is merely an association relationship describing an associated object, and means that there may be three relationships, for example, at least one of a and B, may mean: a exists alone, A and B exist simultaneously, and B exists alone.
It is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion.
Example 1
The embodiment mainly introduces a stable operation control method of a flexible traction power supply system.
A stable operation control method of a flexible traction power supply system comprises the following steps:
s1, firstly, selecting a flexible traction transformer as a main station, providing a standard reference voltage of 27.5kV/50Hz, and connecting the standard reference voltage to a traction network;
s2, selecting other flexible traction transformers as slaves, and realizing phase synchronization tracking of the slave traction network side through a phase synchronization module to ensure that the slave traction networks can be stably connected to the traction network;
s3, setting a power control module, and acquiring a voltage reference value usref；
S4, controlling the flexible traction transformer to output stably;
and S5, setting a power coordination control module to realize that the network voltage at the traction network side is properly increased or reduced along with the running condition of the train.
Further, the phase synchronization module in the step S2 is completed by a single-phase-locked loop and a single-phase voltage coordinate system transformation module, and mainly includes:
s21, constructing virtual alpha and beta phases by using a single-phase voltage coordinate system transformation module, and acquiring alpha phase voltage and beta phase voltage;
s22 phase omega of traction network side obtained through single-phase-locked loopgt；
S23, and traction network side voltage phase omega obtained by using S2gt is used for carrying out Park conversion on the alpha and beta phase voltages of S21 to obtain usq。
Further, in the step S21, the single-phase voltage coordinate system transformation module adopts a 1/4 period delay algorithm to construct a virtual beta phase, that is, equation 1 is used, where equation 1 is
The angular frequency ω 02 pi f, f 50Hz, voltage Us＝27.5kV；usα，usβRespectively constructing virtual alpha phase voltage and virtual beta phase voltage, and j is an imaginary number sign.
Further, after the phase ω gt of the traction network side is obtained through the single-phase-locked loop in the step S23, the formula 1 is transformed into a dq coordinate system through Park, that is, the formula 2 is used, where the formula 2 is:
said u issdAnd usqObtaining u as the voltage value under dq coordinate systemsqThe deviation from 0 is realized by a PI controllerg＝ω0And the synchronous tracking of the output phase of the flexible traction transformer to the network voltage phase at the side of the traction network is met.
Further, the power control module in the step S3 includes a reactive power-amplitude control module and an active power-frequency control module.
Further, the voltage reference value u is obtained in the step S3srefThe specific method comprises the following steps:
s61, collecting output voltage u of flexible traction transformersOutput current is；
S62, calculating to obtain output active power P and reactive power Q;
s63, obtaining a corresponding voltage reference value u by the flexible traction transformer according to the output power of the flexible traction transformer under the actual current taking condition of the trainsrefAnd angular frequency ωsdref。
Further, in the step S4, stable output of the flexible traction transformer is ensured, and the step is realized by a voltage-current double closed-loop control module. Reference value u obtained from S3srefObtaining corresponding reference value U through single-phase dq decouplingsdref、UsqrefThe realization method comprises the following steps:
wherein LPF represents a low pass filter.
Further, in the step S4, the output of the flexible traction transformer adopts an LC filter structure, so as to obtain a control equation of the voltage-current double closed loop after dq decoupling.
Further, in the step S5, the power coordination control module is specifically configured to adjust the power control module to give the amplitude reference value according to the train operation position.
Further, the power coordination control module gives a reference value of the amplitude value
The module sets the automatic adjusting parameter va with the given value of the amplitude value
Wherein
C is a constant related to the characteristics of the system, and dist is the average distance between the train and the flexible traction transformer when the train operates. Please refer to fig. 1-4; FIG. 1 is a schematic structural diagram of a flexible traction power supply system according to the present invention; FIG. 2 is a general schematic diagram of a stability control method according to the present invention; FIG. 3 is a schematic diagram of a phase pre-synchronization module according to the present invention; FIG. 4 is a schematic diagram of a voltage-current dual closed-loop control module according to the present invention.
The stable operation control method suitable for the flexible traction power supply system ensures that the output voltage of the flexible traction transformer is controllable, meets the through power supply requirement of the flexible traction power supply system, and realizes full-line through traction power supply.
The power coordination control method suitable for the flexible traction power supply system can effectively achieve that the loss of the traction network side of the flexible traction power supply system is kept at a small level, and the system is guaranteed to operate friendly and stable.
The phase pre-synchronization control and the power control method are combined and applied to the flexible traction power supply system, synchronous communication among stations is not needed, and safe and stable grid connection and disconnection of the flexible traction transformer can be guaranteed. Meanwhile, the master station is provided with a whole set of control algorithm, so that the master station and the slave station can be randomly converted, and the stable operation of the system of the flexible traction power supply system after any flexible traction transformer is disconnected is ensured.
The flexible traction transformer used in the application can keep the output consistent according to control, so that the input side of the three-phase power grid is relatively independent;
the output of the flexible traction transformer used in the application can provide stable voltage for a traction network, and the multiple flexible traction transformers can achieve the purpose of eliminating electric phase splitting due to the advantage of complete controllability;
example 2
Based on the foregoing embodiment 1, this embodiment mainly introduces a stable operation control method for a flexible traction power supply system.
A stable operation control method of a flexible traction power supply system comprises a phase pre-synchronization module, a power control module, a voltage and current double closed-loop control module and a power coordination control module, wherein the output of a flexible traction transformer is controlled through the modules, so that the stability of the flexible traction power supply system is realized, and the specific steps are as follows:
s1: firstly, selecting one flexible traction transformer as a main station, providing corresponding standard reference voltage of 27.5kV/50Hz to control the output voltage of the flexible traction transformer, connecting the flexible traction transformer to a traction network, and providing corresponding stable traction network voltage.
S2: the other flexible traction transformers are used as slaves, synchronous tracking of phases of the slave traction network side is achieved through a phase synchronization module, stable access to the traction network is guaranteed, and the module is completed by means of single-phase-locked loops and single-phase voltage coordinate system transformation; the single-phase voltage coordinate system transformation module adopts 1/4 cycle delay algorithm to construct virtual beta phase, namely formula 1:
the angular frequency ω 02 pi f, f 50Hz, voltage Us＝27.5kV；usα，usβRespectively constructing virtual alpha phase voltage and virtual beta phase voltage, and j is an imaginary number sign.
Phase omega of traction network side obtained through single-phase-locked loopgAfter t, the formula 1 is transformed into dq coordinate system through Park, that is, the formula 2 is used, and the formula 2 is:
said u issdAnd usqIs the voltage value under dq coordinate system, then u is obtainedsqThe deviation from 0 can be realized by the PI controllerωg＝ω0The synchronous tracking of the output phase of the flexible traction transformer to the network voltage phase of the traction network side is met, and meanwhile, the module does not need inter-station synchronous communication and can greatly reduce the requirement on communication.
S3: a power control module is provided, which includes a reactive power-amplitude control module and an active power-frequency control module. By collecting the output voltage u of the flexible traction transformersOutput current isCalculating to obtain output active power P and reactive power Q, wherein the part needs to set adjusting parameters according to the system stability control requirement: the power control coefficients Km and Kn are fixed constant values, and the parts can ensure that the flexible traction transformer obtains corresponding voltage reference values u according to the output power of the flexible traction transformer and the actual current taking condition of the trainsrefAnd angular frequency ωsdref。
S4: and controlling the flexible traction transformer to output stably, ensuring that the flexible traction transformer has good stability, and realizing the stable output by a voltage and current double-closed-loop control module. Reference value u obtained from S3srefObtaining corresponding reference value u through single-phase dq decouplingsdref、usqrefFor a reference voltage usrefCan be decomposed into:
equation 3:
usref＝usdrefcos(ωsreft)+usqrefsin(ωsreft)；
equation 4:
therefore, the low pass filter LPF is added, so that the double frequency component in the formula 4 can be filtered, and the formula 5 can be obtained;
equation 5:
where LPF represents a low pass filter, the output remains below the cut-off frequency, which is set to 20 Hz. Particularly, the output of the flexible traction transformer adopts an LC filtering structure, and the control equation of the voltage and current double closed loop after dq decoupling is obtained as follows:
where K is the dielectric constant, L and C are the equivalent inductance and capacitance, and S is the poynting vector.
And obtaining a voltage and current double closed-loop control strategy according to a control equation as shown in figure 4.
S5: particularly, in order to ensure that the system can run efficiently and stably, the power coordination control module adjusts the given amplitude reference value of the power control module according to the running position of the train, and under the standard condition, the amplitude is given
This module sets up the automatically regulated parameter va, and the amplitude given value is: equation 6:
in equation 6, C is a constant related to the characteristics of the system itself, and dist is the average distance between the train and the flexible traction transformer when the train is in operation. The method and the device can realize that the network voltage of the traction network side is properly increased or reduced along with the running condition of the train, ensure the bilateral power supply of the flexible traction power supply system, effectively maintain the network voltage of the traction network side stable and keep the loss of the traction network side at a smaller level; moreover, after a certain flexible traction transformer is disconnected, special fault parameters are set, cross-region power supply of the flexible traction transformer can be guaranteed, and power-down operation of special working condition train loads is guaranteed.
Example 3
Based on the above embodiments 1-2, this embodiment mainly introduces a simulation verification of a stable operation control method of a flexible traction power supply system.
Simulation was performed according to the method of use of the present application, resulting in the simulation diagrams of fig. 5 and 6.
FIG. 5 is a simulation diagram of the voltage on the traction network side when two flexible traction transformers provided by the present invention are operated synchronously;
FIG. 6 is a diagram of the relationship between the output power of two flexible traction transformers and the operation position of a locomotive according to the present invention.
Through the graph 5, it can be obviously judged that the output voltage of the flexible traction transformer shows standard sine wave fluctuation, which indicates that a stable operation control strategy realizes synchronous operation, and can provide stable network voltage for a traction network, thereby achieving the purpose of through power supply.
Considering the "ac-dc-ac" locomotive as the load, the system is mainly providing active power, and the simulation is obtained as shown in fig. 6: the diagram shows that the locomotive runs between two flexible traction transformers, four running positions are arranged, and the relation between the output power of the two flexible traction transformers and the running position of the locomotive is obtained. The active power output by the #1 and the #2 can be obtained, the active power output by the #1 and the #2 is symmetrically distributed, the active power output by the #1 and the #2 can be obviously obtained, the distance of the locomotive can be effectively in negative correlation with the output power of the locomotive, bilateral power supply can be guaranteed, and meanwhile, the loss of the traction network side is kept small.
Therefore, the design of the flexible traction power supply system can realize the random conversion between the master station and the slave station, and the stable operation of the system of the flexible traction power supply system after the network is disconnected from any flexible traction transformer is ensured.
The above description is only a preferred embodiment of the present invention, and it is not intended to limit the scope of the present invention, and various modifications and changes may be made by those skilled in the art. Variations, modifications, substitutions, integrations and parameter changes of the embodiments may be made without departing from the principle and spirit of the invention, which may be within the spirit and principle of the invention, by conventional substitution or may realize the same function.
Claims (10)
1. A stable operation control method of a flexible traction power supply system is characterized by comprising the following steps:
s1, firstly, selecting a flexible traction transformer as a main station, providing a standard reference voltage of 27.5kV/50Hz, and connecting the standard reference voltage to a traction network;
s2, selecting other flexible traction transformers as slaves, and realizing phase synchronization tracking of the slave traction network side through a phase synchronization module to ensure that the slave traction networks can be stably connected to the traction network;
s3, setting a power control module, and acquiring a voltage reference value usref；
S4, controlling the flexible traction transformer to output stably;
and S5, setting a power coordination control module to realize that the network voltage at the traction network side is properly increased or reduced along with the running condition of the train.
2. The method as claimed in claim 1, wherein the phase synchronization module in step S2 is implemented by a single-phase-locked loop and a single-phase voltage coordinate system transformation module, and includes:
s21, constructing virtual alpha and beta phases by using a single-phase voltage coordinate system transformation module, and acquiring alpha phase voltage and beta phase voltage;
s22 phase position omega of traction network side voltage obtained through single-phase-locked loopgt；
S23, and traction network side voltage phase omega obtained by using S2gt is used for carrying out Park conversion on the alpha and beta phase voltages of S21 to obtain usq。
3. The method as claimed in claim 2, wherein the single-phase voltage coordinate system transformation module in the step S21 adopts a 1/4 cycle delay algorithm to construct a virtual beta phase, that is, formula 1 is formula 1
The angular frequency ω02 pi f, f 50Hz, voltage Us＝27.5kV；usα，usβRespectively constructing virtual alpha phase voltage and virtual beta phase voltage, and j is an imaginary number sign.
4. The stable operation control method of the flexible traction power supply system according to claim 2, wherein the phase ω of the traction network side obtained by the single-phase-locked loop in the step S23 is obtainedgAfter t, converting the formula 1 into a dq coordinate system through Park, namely using a formula 2, wherein the formula 2 is:
said u issdAnd usqObtaining u as the voltage value under dq coordinate systemsqThe deviation from 0 is realized by a PI controllerg＝ω0And the synchronous tracking of the output phase of the flexible traction transformer to the network voltage phase at the side of the traction network is met.
5. The method as claimed in claim 1, wherein the power control module in the step S3 includes a reactive power-amplitude control module and an active power-frequency control module.
6. The stable operation control method of the flexible traction power supply system according to claim 5, wherein the step of S3 is implemented by obtaining the voltage reference value usrefThe specific method comprises the following steps:
s61, collecting output voltage u of flexible traction transformersOutput current is；
S62, calculating to obtain output active power P and reactive power Q;
s63, actually getting the trainUnder the condition of current, the flexible traction transformer obtains a corresponding voltage reference value u according to the output power of the flexible traction transformersrefAnd angular frequency ωsdref。
7. The stable operation control method of the flexible traction power supply system according to claim 1, wherein the step S4, which ensures the stable output of the flexible traction transformer, is implemented by a voltage-current double closed-loop control module; reference value u obtained from S3srefObtaining corresponding reference value U through single-phase dq decouplingsdref、UsqrefThe realization method comprises the following steps:
where LPF represents a low pass filter and the output remains below the cut-off frequency, set to 20 Hz.
8. The stable operation control method of the flexible traction power supply system according to claim 7, wherein in the step S4, the output of the flexible traction transformer adopts an LC filter structure to obtain a control equation of a double closed loop of voltage and current after dq decoupling.
9. The stable operation control method of the flexible traction power supply system according to claim 1, wherein in the step S5, the power coordination control module is configured to adjust the given amplitude reference value of the power control module according to the train operation position.
10. The method as claimed in claim 9, wherein the power coordination control module gives the reference value of the amplitude value as
The module sets the automatic adjustment parameter vaGiven value of amplitude
Wherein
C is a constant related to the characteristics of the system, and dist is the average distance between the train and the flexible traction transformer when the train operates.
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