Subway regenerative braking energy double feedback device and method

Abstract

The invention discloses a subway regenerative braking energy dual feedback device and method. The device is characterized in that the positive and negative input ends of a three-phase grid-connected inverter are respectively connected to positive and negative direct current buses; the output end is connected with the wire inlet ends of the low-voltage power distribution system and the medium-voltage looped network through the circuit breaker and the LCL filter respectively; a support capacitor is added between the DC bus and the three-phase grid-connected inverter; the method comprises the following steps: monitoring to obtain traction station voltage and calculating to obtain regenerative braking energy return power; judging whether the circuit breaker acts or not according to the monitored traction station voltage, the regenerative braking energy return power and the state of the circuit breaker at the previous moment; and the internal control module issues a signal to an operating mechanism of the circuit breaker to control the on-off state of the circuit breaker, and judges the operation mode of the regenerative braking energy double-feedback device according to the state of the circuit breaker and the regenerative braking energy return power. Diversified recovery of regenerative braking energy is achieved, and the utilization efficiency of the low-voltage power distribution system on the regenerative braking energy is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of urban rail transit regenerative braking, and in particular relates to a subway regenerative braking energy dual feedback device and method. Background Art

[0002] The distance between urban rail transit stations is short, and trains start and stop frequently. The electric energy generated by train braking accounts for more than 30% of the total traction energy. The research on the utilization method of train braking energy is becoming more and more urgent. The braking process of urban rail trains usually adopts regenerative braking technology, which converts the kinetic energy of the train into electrical energy by changing the working mode of the motor to achieve braking. At present, the power supply system of urban rail transit mainly uses rectifiers to convert three-phase AC power into DC power for supply to trains. However, since the diodes in the rectifier can only transmit energy in one direction, the large amount of regenerative braking energy generated by frequent braking of the train cannot be returned to the upper AC network of the power supply system through the rectifier. If this regenerative energy cannot be absorbed by the adjacent train, it is usually consumed by investing in braking resistors or brake shoes, which will lead to energy waste and cause temperature rise problems in the tunnel.

[0003] In order to effectively utilize the regenerative energy generated by urban rail trains, the main utilization methods currently include the following: (1) In the same power supply section, other trains in traction conditions are used to consume the regenerative energy. This method does not require additional equipment and is low in cost. However, it is not common to have other traction trains in the same section, so the utilization rate needs to be improved. (2) Inverters, step-up transformers and filters are configured in the traction substation to feed back the regenerative energy to the 35kV medium-voltage AC power grid. This method has high feedback power and high utilization efficiency, but the equipment is large and expensive, which may cause impact on the medium-voltage AC power grid and affect the traction power supply. (3) By configuring inverters and filters, the regenerative energy is fed back to the 400V low-voltage AC system to supply station air conditioning, lighting and other auxiliary power equipment in the station. This method has a small equipment size, simple implementation and low cost, but the regenerative braking energy capacity fed back to the low-voltage system is limited and the utilization efficiency is not high. (4) The regenerative energy is stored in the energy storage medium and released back to the traction network when needed. This method has high energy utilization and strong controllability, but the energy storage medium is expensive and has limited storage capacity. Summary of the invention

[0004] In order to maximize the utilization of train regenerative braking energy, the present invention provides a subway regenerative braking energy dual feedback device and method.

[0005] A subway regenerative braking energy dual feedback device of the present invention comprises a set of three-phase grid-connected inverters, two sets of circuit breakers, two sets of LCL filters, a supporting capacitor and an internal control module.

[0006] The positive input terminal and negative input terminal of the three-phase grid-connected inverter are connected to the positive DC bus and the negative DC bus respectively; one end of the output terminal of the three-phase grid-connected inverter is connected to the incoming line terminal of the 400V low-voltage distribution system through circuit breaker 1 and LCL filter, and the other end is connected to the incoming line terminal of the 35kV medium-voltage ring network through circuit breaker 2 and LCL filter; a supporting capacitor is added between the DC bus and the three-phase grid-connected inverter.

[0007] A dual feedback method of a subway regenerative braking energy dual feedback device of the present invention comprises the following steps:

[0008] Step A: monitor and obtain the voltage of the traction station and calculate and obtain the regenerative braking energy return power.

[0009] Step A1: Based on the electrical quantity monitoring system installed in the traction station, real-time monitoring is performed on the voltage at the point where the regenerative braking energy dual feedback device is connected in parallel with the traction station, i.e., the voltage U dc , Regenerative braking energy dual feedback device current I dc , by P re =U dc *I dc Get the regenerative braking energy return power P re .

[0010] Step B: Based on the monitored traction voltage U dc , Regenerative braking energy return power P re The state of circuit breakers 1 and 2 at the previous moment is used to determine whether circuit breakers 1 and 2 are actuated.

[0011] Step B1: The status of circuit breaker 1 and circuit breaker 2 is represented by digital signal S1. The specific meaning of S1 is as follows:

[0012] S1=00, indicating that both circuit breaker 1 and circuit breaker 2 are in the disconnected state.

[0013] S1=10, indicating that circuit breaker 1 is in the closed state and circuit breaker 2 is in the open state.

[0014] S1=11, indicating that both circuit breaker 1 and circuit breaker 2 are in the closed state.

[0015] Step B2: the internal control module uploads the digital signal S1 to the regenerative braking energy dual feedback device with a period of 1 s.

[0016] Step B3: Setting the starting voltage U0 of the dual feedback device for regenerative braking energy and the saturation threshold P of the low-voltage side regenerative braking energy 400 and medium voltage return regenerative braking energy saturation threshold P mid .

[0017] Step B4: The internal control module determines whether circuit breaker 1 and circuit breaker 2 are in operation, wherein S1 a is the circuit breaker status at the previous moment. The specific judgment process is as follows:

[0018] If U dc ≤U0, and S1 a =10 or S1 a =11, then let S1=00.

[0019] If U dc >U0,P re ≤P 400 , and S1 a =00 or S1 a =11, then let S1=10.

[0020] If U dc >U0,P 400 <P re ≤P 400 +P mid , and S1 a =00 or S1 a =10, then let S1=11.

[0021] If U dc >U0,P re >P 400 +P mid , and S1 a =00 or S1 a =10, then let S1=11.

[0022] Step C: The internal control module sends a signal S1 to the operating mechanisms of the circuit breakers 1 and 2, thereby controlling the opening and closing states of the circuit breakers 1 and 2.

[0023] If S1 = 00, the circuit breaker operating mechanism is controlled to disconnect both circuit breaker 1 and circuit breaker 2. At this time, there is no regenerative braking energy feedback.

[0024] If S1 = 10, the circuit breaker operating mechanism is controlled to close circuit breaker 1 and open circuit breaker 2. At this time, the regenerative braking energy is fed back to the low-voltage side.

[0025] If S1=11, the circuit breaker operating mechanism is controlled to close both circuit breaker 1 and circuit breaker 2. At this time, the regenerative braking energy is fed back to the low-voltage power distribution system and the medium-voltage ring network at the same time.

[0026] Step D: According to the status of circuit breakers 1 and 2 and the regenerative braking energy return power P re , determine the operating mode of the regenerative braking energy dual feedback device.

[0027] If S1 = 00, the regenerative braking energy dual feedback device is in idle mode.

[0028] If S1 = 10, the regenerative braking energy dual feedback device enters the low-voltage feedback constant-pressure operation mode.

[0029] If S1=11, and P 400 <P re ≤P 400 +P mid , the regenerative braking energy dual feedback device enters the dual feedback constant pressure operation mode.

[0030] If S1=11, and P re >P 400 +P mid , the regenerative braking energy dual feedback device enters the dual feedback constant power operation mode, and the feedback power of the low-voltage distribution system is P 400 , the medium voltage ring network feedback power is P mid .

[0031] The beneficial technical effects of the present invention are:

[0032] 1. The present invention feeds back regenerative braking energy to the 400V low-voltage power distribution system and the medium-voltage ring network respectively through a dual feedback device for regenerative braking energy, thereby improving the utilization efficiency of the low-voltage power distribution system for regenerative braking energy and alleviating the impact and shock caused by a large amount of regenerative braking energy flowing to the medium-voltage ring network at the same time.

[0033] 2. The present invention mainly adopts a low-cost low-voltage feedback method, supplemented by a small-capacity medium-voltage feedback method, to maximize the utilization of regenerative braking energy while relatively reducing the feedback cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the electrical topology structure of the subway regenerative braking energy dual feedback device of the present invention.

[0035] Figure 2 It is a schematic diagram of the dual feedback process of the dual feedback device for subway regenerative braking energy of the present invention.

[0036] Figure 3 It is the working characteristic curve of the traction after the intervention of the regenerative braking energy dual feedback device of the present invention.

[0037] Figure 4 It is a diagram showing the division of operation modes and working principle of the dual feedback device for regenerative braking energy of the present invention.

[0038] Figure 5 It is the simulation result of the DC side network voltage variation curve of a traction station that does not use the regenerative braking energy dual feedback device.

[0039] Figure 6 This is the simulation result of the DC side grid voltage change curve after a traction station adopts a regenerative braking energy dual feedback device.

[0040] Figure 7 It is the utilization of train regenerative braking energy after a certain traction station adopts a regenerative braking energy dual feedback device. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below with reference to the accompanying drawings and specific implementation examples.

[0042] The electrical topology of a subway regenerative braking energy dual feedback device of the present invention is as follows Figure 1 As shown, it includes a three-phase grid-connected inverter, two circuit breakers, two LCL filters, a supporting capacitor and an internal control module.

[0043] The positive input terminal and the negative input terminal of the three-phase grid-connected inverter A are connected to the positive DC bus E1 and the negative DC bus E2 respectively; one end of the output terminal of the three-phase grid-connected inverter A is connected to the incoming line terminal of the 400V low-voltage distribution system through circuit breaker 1 and LCL filter B, and the other end is connected to the incoming line terminal of the 35kV medium-voltage ring network through circuit breaker 2 and LCL filter C; a supporting capacitor D is added between the DC bus and the three-phase grid-connected inverter A.

[0044] The overall process of the dual feedback method of the subway regenerative braking energy dual feedback device of the present invention is as follows: Figure 2 As shown, the following steps are included:

[0045] Step A: monitor and obtain the voltage of the traction station and calculate and obtain the regenerative braking energy return power.

[0046] Step A1: Based on the electrical quantity monitoring system installed in the traction station, real-time monitoring is performed on the voltage at the point where the regenerative braking energy dual feedback device is connected in parallel with the traction station, i.e., the voltage U dc , Regenerative braking energy dual feedback device current I dc , by P re =U dc *I dc Get the regenerative braking energy return power P re After the regenerative braking energy dual feedback device is connected to the traction power supply system, the traction station working characteristic curve is as follows: Figure 3 shown.

[0047] Step B: Based on the monitored traction voltage U dc , Regenerative braking energy return power P re The previous state of circuit breakers 1 and 2 is used to determine whether circuit breakers 1 and 2 are actuated.

[0048] Step B1: The status of circuit breaker 1 and circuit breaker 2 is represented by digital signal S1. The specific meaning of S1 is as follows:

[0049] S1=00, indicating that both circuit breaker 1 and circuit breaker 2 are in the disconnected state.

[0050] S1=10, indicating that circuit breaker 1 is in the closed state and circuit breaker 2 is in the open state.

[0051] S1=11, indicating that both circuit breaker 1 and circuit breaker 2 are in the closed state.

[0052] Step B2: the internal control module uploads the digital signal S1 to the regenerative braking energy dual feedback device with a period of 1 s.

[0053] Step B3: Setting the starting voltage U0 of the dual feedback device for regenerative braking energy and the saturation threshold P of the low-voltage side regenerative braking energy 400 and medium voltage return regenerative braking energy saturation threshold P mid .

[0054] Step B4: The internal control module determines whether circuit breaker 1 and circuit breaker 2 are in operation, wherein S1 a is the circuit breaker status at the previous moment. The specific judgment process is as follows:

[0055] If U dc ≤U0, and S1 a =10 or S1 a =11, then let S1=00.

[0056] If U dc >U0,P re ≤P 400 , and S1 a =00 or S1 a =11, then let S1=10.

[0057] If U dc >U0,P 400 <P re ≤P 400 +P mid , and S1 a =00 or S1 a =10, then let S1=11.

[0058] If U dc >U0,P re >P 400 +P mid , and S1 a =00 or S1 a =10, then let S1=11.

[0059] Step C: The internal control module sends a signal S1 to the operating mechanisms of the circuit breakers 1 and 2, thereby controlling the opening and closing states of the circuit breakers 1 and 2.

[0060] If S1 = 00, the circuit breaker operating mechanism is controlled to disconnect both circuit breaker 1 and circuit breaker 2. At this time, there is no regenerative braking energy feedback.

[0061] If S1 = 10, the circuit breaker operating mechanism is controlled to close circuit breaker 1 and open circuit breaker 2. At this time, the regenerative braking energy is fed back to the low-voltage side.

[0062] If S1=11, the circuit breaker operating mechanism is controlled to close both circuit breaker 1 and circuit breaker 2. At this time, the regenerative braking energy is fed back to the low-voltage power distribution system and the medium-voltage ring network at the same time.

[0063] Step D: According to the status of circuit breakers 1 and 2 and the regenerative braking energy return power P re , determine the operating mode of the regenerative braking energy dual feedback device. The operating mode division and working principle of the regenerative braking energy dual feedback device are as follows Figure 4 shown.

[0064] If S1 = 00, the regenerative braking energy dual feedback device is in idle mode.

[0065] If S1 = 10, the regenerative braking energy dual feedback device enters the low-voltage feedback constant-pressure operation mode.

[0066] If S1=11, and P 400 <P re ≤P 400 +P mid , the regenerative braking energy dual feedback device enters the dual feedback constant pressure operation mode.

[0067] If S1=11, and P re >P 400 +P mid , the regenerative braking energy dual feedback device enters the dual feedback constant power operation mode, and the feedback power of the low-voltage distribution system is P 400 , the medium voltage ring network feedback power is P mid .

[0068] Example:

[0069] This embodiment is based on the simulation software Matlab to illustrate the dual feedback method of subway regenerative braking energy. The steps of this embodiment are as follows:

[0070] Step 1: Collect and obtain the traction voltage U dc And calculate and obtain the regenerative braking energy return power P re , as input data for the dual feedback device of regenerative braking energy.

[0071] Step 2: Programming is performed in the control system calculation model built by Matlab / Simulink using the software's own programming language to achieve the dual feedback of subway regenerative braking energy described in the present invention.

[0072] Step 3: Update U in real time dc and P re , divide the operation mode of the dual feedback device of regenerative braking energy and count the utilization of regenerative braking energy.

[0073] Based on the control system calculation model built in the above steps, the parameters of the dual feedback device of regenerative braking energy are set as follows: the feedback saturation threshold P of the low-voltage distribution system 400 For 1MW, the medium voltage ring network feedback saturation threshold P mid The starting voltage U0 of the regenerative braking energy dual feedback device is 1MW, and the starting voltage U0 of the regenerative braking energy dual feedback device is 1720V. This case simulates the operation status of 50 trains on a domestic line. There are 25 traction stations along the line. It takes a total of 12923s from the departure of the first train to the arrival of the 50th train. A traction station is selected to monitor and obtain U dc and P re , the traction power supply system after connecting to the regenerative braking energy dual feedback device is simulated and analyzed. The simulation results are as follows Figure 5 , 6 As shown in ,7, the simulation results are analyzed below.

[0074] Figure 5 It is the simulation result of the DC side network voltage change curve of the selected traction station without the dual feedback device of regenerative braking energy (a traction station of the line is randomly selected). At this time, in order to avoid causing a sudden increase in the traction network voltage, an on-board resistor is used to consume the regenerative braking energy, among which the starting voltage of the on-board resistor is 1670V.

[0075] Figure 6 Is to select and Figure 5 The simulation results of the DC side network voltage change curve of the same traction station using a regenerative braking energy dual feedback device. The traction station is equipped with a regenerative braking energy dual feedback device, and the starting voltage of the device is 1720V.

[0076] Figure 7 Is to select and Figure 5 The utilization of regenerative braking energy of trains with the same traction using a dual feedback device for regenerative braking energy is divided into four modes through different levels: traction state, low-voltage feedback mode, dual feedback mode and on-board resistor intervention (in some periods of time, the total amount of regenerative braking energy sent back exceeds the overall capacity saturation threshold, and on-board resistor intervention is used to consume it).

[0077] It can be seen from the simulation results that the dual feedback device and method of subway regenerative braking energy built in this case is simple to implement and has a wide range of applications. When put into use in the subway traction power supply system, it can raise the traction network voltage and maintain stability, realize the diversified recovery of regenerative braking energy, reduce the heat consumption of regenerative braking energy by on-board resistors, and relatively reduce the investment cost.

Claims

1. A dual feedback device for subway regenerative braking energy, characterized in that: It includes a three-phase grid-connected inverter (A), two circuit breakers, two LCL filters (B, C), a supporting capacitor (D) and an internal control module; The positive input terminal and the negative input terminal of the three-phase grid-connected inverter (A) are connected to the positive DC bus (E1) and the negative DC bus (E2) respectively; one end of the output terminal of the three-phase grid-connected inverter (A) is connected to the incoming line terminal of the 400V low-voltage power distribution system through the circuit breaker 1 and the LCL filter (B), and the other end is connected to the incoming line terminal of the 35kV medium-voltage ring network through the circuit breaker 2 and the LCL filter (C); a supporting capacitor (D) is added between the DC bus and the three-phase grid-connected inverter (A).

2. The dual feedback method of the subway regenerative braking energy dual feedback device as claimed in claim 1, characterized in that: The following steps are involved: Step A, monitoring and obtaining the voltage of the traction station and calculating and obtaining the regenerative braking energy return power; Step A1: Based on the electrical quantity monitoring system installed in the traction station, real-time monitoring is performed on the voltage at the point where the regenerative braking energy dual feedback device is connected in parallel with the traction station, i.e., the voltage U dc , Regenerative braking energy dual feedback device current I dc , by P re =U dc *I dc Get the regenerative braking energy return power P re ; Step B: Based on the monitored traction voltage U dc , Regenerative braking energy return power P re and the previous state of circuit breakers 1 and 2 to determine whether circuit breakers 1 and 2 are actuated; Step B1: The status of circuit breaker 1 and circuit breaker 2 is represented by digital signal S1. The specific meaning of S1 is as follows: S1=00, indicating that both circuit breaker 1 and circuit breaker 2 are in the disconnected state; S1=10, indicating that circuit breaker 1 is in the closed state and circuit breaker 2 is in the open state; S1=11, indicating that both circuit breaker 1 and circuit breaker 2 are in the closed state; Step B2, the internal control module uploads the digital signal S1 to the regenerative braking energy dual feedback device with a period of 1 s; Step B3: Setting the starting voltage U0 of the dual feedback device for regenerative braking energy and the saturation threshold P of the low-voltage side regenerative braking energy 400 and medium voltage return regenerative braking energy saturation threshold P mid ; Step B4: The internal control module determines whether circuit breaker 1 and circuit breaker 2 are in operation, wherein S1 a is the circuit breaker status at the previous moment. The specific judgment process is as follows: If U dc ≤U0, and S1 a =10 or S1 a =11, then let S1=00; If U dc >U0,P re ≤P 400 , and S1 a =00 or S1 a =11, then let S1=10; If U dc >U0,P 400 <P re ≤P 400 +P mid , and S1 a =00 or S1 a =10, then let S1=11; If U dc >U0,P re >P 400 +P mid , and S1 a =00 or S1 a =10, then let S1=11; Step C: the internal control module sends a signal S1 to the operating mechanisms of the circuit breakers 1 and 2, thereby controlling the opening and closing states of the circuit breakers 1 and 2; If S1 = 00, the circuit breaker operating mechanism is controlled to disconnect both circuit breaker 1 and circuit breaker 2. At this time, there is no regenerative braking energy feedback; If S1 = 10, the circuit breaker operating mechanism is controlled to close circuit breaker 1 and open circuit breaker 2. At this time, the regenerative braking energy is fed back to the low-voltage side; If S1=11, the circuit breaker operating mechanism is controlled to close both circuit breaker 1 and circuit breaker 2. At this time, the regenerative braking energy is fed back to the low-voltage power distribution system and the medium-voltage ring network at the same time; Step D: According to the status of circuit breakers 1 and 2 and the regenerative braking energy return power P re , determine the operation mode of the regenerative braking energy dual feedback device; If S1 = 00, the regenerative braking energy dual feedback device is in idle mode; If S1 = 10, the regenerative braking energy dual feedback device enters the low-voltage feedback constant-pressure operation mode; If S1 = 11, and P 400 <P re ≤P 400 +P mid , the regenerative braking energy dual feedback device enters the dual feedback constant pressure operation mode; If S1 = 11, and P re >P 400 +P mid , the regenerative braking energy dual feedback device enters the dual feedback constant power operation mode, and the feedback power of the low-voltage distribution system is P 400 , the medium voltage ring network feedback power is P mid .

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