Distributed cooperative absorption method for braking energy of urban rail transit
阅读说明：本技术 一种城市轨道交通制动能量分布式协同吸收方法 (Distributed cooperative absorption method for braking energy of urban rail transit ) 是由 白锡彬 郭戈 吴松 刘贺江 邓九鹏 张泽 于 2019-11-07 设计创作，主要内容包括：本发明公开了一种城市轨道交通制动能量分布式协同吸收方法,通过控制牵引变电所制动能量利用装置的吸收电压,从而触发相邻站制动能量利用装置投入工作,使得列车进站时的再生制动峰值功率能被多个相邻站的能量利用装置共同吸收,减小对单个站的功率冲击,有利于再生制动能量在地铁系统内部更好的被利用,降低电能反送城市电网的概率。(The invention discloses a distributed cooperative absorption method for urban rail transit braking energy, which triggers adjacent station braking energy utilization devices to work by controlling the absorption voltage of a traction substation braking energy utilization device, so that the regenerative braking peak power of a train entering a station can be jointly absorbed by the energy utilization devices of a plurality of adjacent stations, the power impact on a single station is reduced, the regenerative braking energy can be better utilized in a subway system, and the probability of electric energy back-transmission to an urban power grid is reduced.)
1. A distributed cooperative absorption method for urban rail transit braking energy is characterized in that according to the position of a train in a traction power supply system, when two traction substations are arranged on one side of the train at an instant position and no traction substation is arranged on the other side, a square sum criterion of current difference is expressed as follows:
wherein U is traction network pressure at the train position, i1、i2Respectively two traction substations S1、S2Loop current of the loop in which it is located, ItrainIs the braking current, U, of the train1And U2Respectively two traction substations S1、S2The voltage of (2) and the power supply network impedance between the train instant position and the two traction substations are respectively R1、R2；
The available constraints are as follows:
control U1＝U2When the formula (1) has the minimum value, two traction substations S can be obtained1、S2Virtual impedance r of1、r2The following relationship should be satisfied:
r2＝R1+r1(3)；
by controlling the virtual impedance of the two traction substations to satisfy the relation of the formula (3), the balance of train braking current absorbed by the two traction substations can be realized.
2. The urban rail transit braking energy distributed cooperative absorption method according to claim 1, wherein a power supply network impedance R between the train instant position and two traction substations is obtained through line impedance and instant position information calculation by specifically acquiring the instant position of the train, then calculating the relative position between the train instant position and each traction substation, and finally calculating the line impedance and the instant position information1、R2。
3. A distributed cooperative absorption method for urban rail transit braking energy is characterized in that according to the position of a train in a traction power supply system, when two traction substations are arranged on one side and one traction substation is arranged on the other side of the train at the instant position, the square sum criterion of current difference is expressed as follows:
u is traction network pressure at the train position, i1、i2、i3Respectively three traction substations S1、S2、S3Loop current of the loop in which it is located, ItrainIs the braking current, U, of the train1、U2、U3Respectively three traction substations S1、S2、S3The voltage of (2) and the power supply network impedance between the train instant position and the three traction substations are respectively R1、R2、R3；
The available constraints are as follows:
control U1＝U2＝U3When the formula (4) has the minimum value, the available traction substation S1、S2、S3Virtual impedance r of1、r2、r3The following relationship should be satisfied:
by controlling the virtual impedances of the three traction substations to satisfy the relation of the formula (6), the balance of train braking currents absorbed by the three traction substations can be realized.
4. The urban rail transit braking energy distributed cooperative absorption method according to claim 3, wherein power supply network impedance R between the train instant position and three traction substations is obtained through line impedance and instant position information calculation by specifically acquiring the instant position of the train, then calculating the relative position between the train instant position and each traction substation, and1、R2、R3。
5. a distributed cooperative absorption method for urban rail transit braking energy is characterized in that according to the position of a train in a traction power supply system, when two traction substations are arranged on two sides of the instant position of the train, the square sum criterion of the current difference is specifically expressed as follows:
the available constraints are as follows:
wherein U is traction network pressure at the train position, i1、i2、i3、i4Respectively four traction substations S1、S2、S3、S4Loop current of the loop in which it is located, ItrainIs the braking current, U, of the train1、U2、U3、U4Respectively four traction substations S1、S2、S3、S4The voltage of (1) and the power supply network impedance between the train instant position and the four traction substations are respectively R1、R2、R3、R4；
Control U1＝U2＝U3＝U4When the formula (7) has the minimum value, the available traction substation S1、S2、S3、S4Virtual impedance r of1、r2、r3、r4The following relationship should be satisfied:
by controlling the virtual impedances of the four traction substations to satisfy the relation of the formula (9), the balance of train braking currents absorbed by the four traction substations can be realized.
6. The urban rail transit braking energy distributed cooperative absorption method according to claim 1, wherein power supply network impedance R between the train instant position and four traction substations is obtained through line impedance and instant position information calculation by specifically acquiring the instant position of the train, then calculating the relative position between the train instant position and each traction substation, and calculating1、R2、R3、R4。
Technical Field
The invention relates to the technical field of urban rail transit, in particular to a distributed cooperative absorption method for braking energy of urban rail transit.
Background
At present, a traction power supply system of urban rail transit mainly comprises a
In the subway common braking mode, the braking mode can be divided into electric braking and mechanical braking. Electric braking is classified into regenerative braking and resistance braking. When the subway train is in regenerative braking, the motor is in a power generation state, a constant-voltage absorption method is mostly adopted in the current regenerative braking energy utilization device of the rail transit train, when the direct-current voltage exceeds a specified value due to regenerative braking of the train, the bidirectional converter is started and absorbs current from the direct-current bus, and the regenerative electric energy is converted into power-frequency alternating current to be fed back to the alternating-current equipment bus of the traction substation or stored in the energy storage device of the traction substation.
The problems currently exist as follows: 1. the train is intensively entered into the station, so that the short-time feedback current is large, and a single station needs to completely absorb the energy and needs to be provided with a braking energy utilization device with corresponding power, so that the cost of the device is increased; 2. when the train is emergently braked, after the braking energy utilization device is started to absorb energy, the direct current network voltage still rises to exceed the safety limit value due to the existence of a contact line or a third rail impedance, at the moment, the train needs to start an appliance to brake to cooperate with parking, and the energy is worn and consumed by the brake shoe and is not effectively recycled; 3. the braking energy utilization device adopts the current energy absorption mode, the energy of a single station is concentrated and returned in a short time, so that the network voltage of the medium-voltage ring network is raised, part of the energy is not absorbed in the subway system and directly returns to other user ends of the power system, no direct economic benefit is brought to subway companies, and the subway operation unit also provides improvement requirements.
According to the energy processing mode, the braking energy utilization device comprises a storage type, an energy consumption type and an energy feedback type, and currently, a medium-voltage energy feedback device and a super-capacitor energy storage device are widely applied and are collectively called as a braking energy utilization device.
The medium-voltage energy feeding device is a conversion device which absorbs energy generated by regenerative braking of a vehicle and converts the energy into alternating-current energy. The inversion absorption device can be arranged in a traction substation or a step-down substation, the inversion absorption device mainly adopts a power electronic device high-power thyristor to form a three-phase inverter, the direct current side of the inverter is connected with a direct current switch cabinet bus in the traction substation, and the alternating current side of the inverter is connected to a subway medium-voltage network through a transformer. When the vehicle regeneratively brakes to enable the direct-current voltage to exceed the specified value, the inverter is started and absorbs current from the direct-current bus, and regenerated direct-current electric energy is inverted into power-frequency alternating current to be fed back to the alternating-current equipment bus of the traction substation.
The ground super-capacitor energy storage system is arranged in the traction substation and connected with the direct-current traction network in parallel, and energy interaction between the ground super-capacitor energy storage system and a train is realized by controlling the bidirectional DC/DC converter in actual work. The super capacitor is a capacitor with the capacitance value of thousands of farads, has incomparable advantages with other energy storage devices, has no energy conversion in the charge-discharge process, directly stores in the form of potential energy, and has high efficiency. With the invention of the double-electric-layer capacitor, the high-surface-area electrode and the double-electric-layer structure greatly increase the energy density of capacitance energy storage, so that the capacitor can have wider application space. Although the energy density of the super capacitor is smaller than that of the other two energy storage modes, due to the factors of high power density, long cycle life, relatively mature technology and the like, the super capacitor can bear the instantaneous peak power fluctuation when the subway is started and braked under the working condition of frequent braking of the subway, and is more suitable for the regeneration energy recovery of urban rail transit.
At present, how to efficiently and fully recycle regenerative braking energy becomes a problem to be solved urgently in modern city subways.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a distributed cooperative absorption method for urban rail transit braking energy, which allows the absorption voltage of the braking energy utilization devices of each substation to be linearly increased within a certain range according to the characteristics of virtual resistors along with the increase of braking power when a train is braked, balances the absorption current of adjacent station devices and reduces the impact of the braking current on a traction network.
In order to achieve the purpose, the invention adopts the following technical scheme:
a distributed cooperative absorption method for urban rail transit braking energy comprises the following steps:
according to the position of the train in the traction power supply system, when one side of the train at the instant position is provided with two traction substations and the other side is not provided with the traction substations, the square sum criterion of the current difference is expressed as:
wherein U is traction network pressure at the train position, i1、i2Respectively two traction substations S1、S2Loop current of the loop in which it is located, ItrainIs the braking current, U, of the train1And U2Respectively two traction substations S1、S2The voltage of (2) and the power supply network impedance between the train instant position and the two traction substations are respectively R1、R2；
The available constraints are as follows:
control U1＝U2When the formula (1) has the minimum value, two traction substations S can be obtained1、S2Virtual impedance r of1、r2The following relationship should be satisfied:
r2＝R1+r1(3)；
by controlling the virtual impedance of the two traction substations to satisfy the relation of the formula (3), the balance of train braking current absorbed by the two traction substations can be realized.
Further, in the technical scheme, the instant position of the train is calculated by specifically acquiring the instant position of the trainCalculating the relative position of each traction substation and the power supply network impedance R between the train instant position and the two traction substations according to the line impedance and the instant position information1、R2。
As another technical solution, the invention also provides a distributed cooperative absorption method of urban rail transit braking energy, which comprises the following steps:
according to the position of the train in the traction power supply system, when two traction substations are arranged on one side and one traction substation is arranged on the other side of the train at the instant position, the square sum criterion of the current difference is expressed as follows:
u is traction network pressure at the train position, i1、i2、i3Respectively three traction substations S1、S2、S3Loop current of the loop in which it is located, ItrainIs the braking current, U, of the train1、U2、U3Respectively three traction substations S1、S2、S3The voltage of (2) and the power supply network impedance between the train instant position and the three traction substations are respectively R1、R2、R3；
The available constraints are as follows:
control U1＝U2＝U3When the formula (4) has the minimum value, the available traction substation S1、S2、S3Virtual impedance r of1、r2、r3The following relationship should be satisfied:
by controlling the virtual impedances of the three traction substations to satisfy the relation of the formula (6), the balance of train braking currents absorbed by the three traction substations can be realized.
Further, in the technical scheme, the real-time position of the train is obtained, the relative positions of the real-time position of the train and each traction substation are calculated, and the power supply network impedance R between the real-time position of the train and the three traction substations is obtained through line impedance and real-time position information calculation1、R2、R3。
As another technical solution, the invention also provides a distributed cooperative absorption method of urban rail transit braking energy, which comprises the following steps:
when two traction substations are respectively arranged on two sides of the instant position of the train according to the position of the train in the traction power supply system, the square sum criterion of the current difference is specifically expressed as follows:
the available constraints are as follows:
wherein U is traction network pressure at the train position, i1、i2、i3、i4Respectively four traction substations S1、S2、S3、S4Loop current of the loop in which it is located, ItrainIs the braking current, U, of the train1、U2、U3、U4Respectively four traction substations S1、S2、S3、S4The voltage of (1) and the power supply network impedance between the train instant position and the four traction substations are respectively R1、R2、R3、R4；
Control U1＝U2＝U3＝U4When the formula (7) has the minimum value, the available traction substation S1、S2、S3、S4Virtual impedance r of1、r2、r3、r4The following relationship should be satisfied:
by controlling the virtual impedances of the four traction substations to satisfy the relation of the formula (9), the balance of train braking currents absorbed by the four traction substations can be realized.
Further, in the technical scheme, the real-time position of the train is obtained, the relative position between the real-time position of the train and each traction substation is calculated, and the power supply network impedance R between the real-time position of the train and the four traction substations is obtained through calculation of the line impedance and the real-time position information1、R2、R3、R4。
The invention has the beneficial effects that: according to the method, the absorption voltage of the braking energy utilization device of the traction substation is controlled, so that the braking energy utilization devices of adjacent stations are triggered to work, the regenerative braking peak power of a train entering the station can be jointly absorbed by the energy utilization devices of a plurality of adjacent stations, most of energy absorbed by the substation close to the train can be avoided, the power impact on a single station is further reduced, the regenerative braking energy can be better utilized in a subway system, and the probability of electric energy being transmitted back to an urban power grid is reduced.
Drawings
FIG. 1 is a schematic diagram of a conventional traction power supply system;
FIG. 2 is a system block diagram of a train station;
FIG. 3 is a schematic diagram of the equivalent topology and the related electrical quantities in the case of the 1) in the embodiment of the present invention;
FIG. 4 is a schematic diagram of the equivalent topology and the related electrical quantities in the case of the 2) in the embodiment of the present invention;
fig. 5 is a schematic diagram of the equivalent topology and the related electrical quantities in the case of the 4) in the embodiment of the present invention.
Detailed Description
The present invention will be further described with reference to the accompanying drawings, and it should be noted that the present embodiment is based on the technical solution, and the detailed implementation and the specific operation process are provided, but the protection scope of the present invention is not limited to the present embodiment.
The embodiment provides a distributed cooperative absorption method for urban rail transit braking energy.
In this example, a block diagram of a per-station system is shown in fig. 2. In the process of electric braking of the train, the train can feed back braking energy to the traction substation provided with the braking energy utilization device, and because a contact network between the substation and the substation has impedance, the substations far away from the two sides of the train only absorb little braking energy, and most energy is absorbed by the substations adjacent to the two sides of the train. Therefore, when considering the equivalent topology in braking, only the braking energy absorbed by each of the two traction transformers adjacent to the left and right sides is considered for the moment.
The position design of the traction substation mainly considers factors such as line conditions, power supply distance, vehicle information, cost analysis and the like, the position of the traction substation cannot be changed after the line is built, and a braking energy absorption device is generally built together with the traction substation for convenient construction and installation. Taking the DC1500V as an example, the distance between two adjacent traction substations is 2-3 km, the shortest is 1 km, the longest is 4 km, the distance between the two traction substations is designed according to the conventional 2-3 km, and the braking position of the two adjacent traction substations is about 6 km away from the traction substation farthest when the train is braked.
During the braking process of the train, according to the position of the train in the traction power supply system, the actual working conditions are summarized into the following three equivalent topologies:
1) two traction substations are arranged on one side of the train, and the traction substation is not arranged on the other side of the train;
2) two traction substations are arranged on one side of the train, and one traction substation is arranged on the other side of the train;
3) two traction substations are respectively arranged on two sides of the train.
The urban rail transit traction substation is distributed along the line according to the line design, so that the urban rail transit traction substation can be simply understood as being sequentially arranged along one line. If a certain line has a plurality of substations, the train braking position occurs in the middle of the line, and the number of the traction substations on each side of the train is larger than two from near to far (for example, 6 traction substations on the whole line, 3 traction substations on two sides may be used when the train is braked). However, as the traction substation is further away from the train braking position, the absorbable braking electric energy is reduced due to the influence of the line impedance, so that the absorbable braking electric energy is not considered to be continuously extended to a plurality of traction substations.
Therefore, the present embodiment is described for three topologies, respectively.
For the 1) equivalent topology:
the 1) equivalent topology and associated electrical quantities are shown in fig. 3. Wherein U is traction network pressure at the train position, i1、i2Two traction substations S respectively nearest to the train instant position1、S2Loop current of the loop in which it is located, ItrainIs the braking current, U, of the train1And U2Respectively two traction substations S1、S2The voltage of (2) and the power supply network impedance between the train instant position and the two traction substations are respectively R1、R2(ii) a The square sum criterion of the current difference is expressed as:
the constraints available from the system topology are as follows:
in order to realize rapid on-line solution, an engineering simplification method is adopted to control U1＝U2When the formula (1) has the minimum value, two traction substations S can be obtained1、S2Virtual impedance r of1、r2The following relationship should be satisfied:
r2＝R1+r1(3)；
by controlling the virtual impedance of the two traction substations to satisfy the relation of the formula (3), the balance of train braking current absorbed by the two traction substations can be realized.
For the equivalent topology of 2):
in the equivalent topology of the 2) th kind, the equivalent topology and the related electrical quantities are as shown in fig. 4. Wherein U is traction network pressure at the train position, i1、i2、i3Three traction substations S which are respectively nearest to the train instant position1、S2、S3Loop current of the loop in which it is located, ItrainIs the braking current, U, of the train1、U2、U3Respectively three traction substations S1、S2、S3The voltage of (2) and the power supply network impedance between the train instant position and the three traction substations are respectively R1、R2、R3(ii) a The square sum criterion of the current difference is expressed as:
constraints derivable from system topology
In order to realize rapid on-line solution, an engineering simplification method is adopted to control U1＝U2＝U3When the formula (4) has the minimum value, the available traction substation S1、S2、S3Virtual impedance r of1、r2、r3The following relationship should be satisfied:
by controlling the virtual impedances of the three traction substations to satisfy the relation of the formula (6), the balance of train braking currents absorbed by the three traction substations can be realized;
for the equivalent topology of type 3):
the current flow during train braking in the equivalent topology of the 3) is shown in fig. 5. Wherein U is traction network pressure at the train position, i1、i2、i3、i4Four traction substations S nearest to the train instant position respectively1、S2、S3、S4Loop current of the loop in which it is located, ItrainIs the braking current, U, of the train1、U2、U3、U4Respectively four traction substations S1、S2、S3、S4The voltage of (1) and the power supply network impedance between the train instant position and the four traction substations are respectively R1、R2、R3、R4(ii) a The square sum criterion of the current difference is specifically expressed as:
constraints derivable from system topology
In order to realize rapid on-line solution, an engineering simplification method is adopted to control U1＝U2＝U3＝U4When the formula (7) has the minimum value, the available traction substation S1、S2、S3、S4Virtual impedance r of1、r2、r3、r4The following relationship should be satisfied:
by controlling the virtual impedances of the four traction substations to satisfy the relation of the formula (9), the balance of train braking currents absorbed by the four traction substations can be realized.
In the above various situations, the real-time position of the train is obtained through an ATC (automatic train control) system, an AT0 system and the like, then the relative position between the real-time position of the train and each adjacent traction substation is calculated, the power supply network impedance between the real-time position of the train and each adjacent traction substation is obtained through line impedance and position information calculation, and the virtual impedance is changed according to the formula (3), the formula (6) or the formula (9) according to the situations of 1, 2) and 3), so that the brake current is balanced as much as possible.
Various corresponding changes and modifications can be made by those skilled in the art based on the above technical solutions and concepts, and all such changes and modifications should be included in the protection scope of the present invention.