A high-speed railway regenerative braking energy feedback system and control method thereof

Abstract

This invention discloses a regenerative braking energy feedback system and its control method for high-speed railways. The system structure is as follows: the left power supply arm of the V / x-connected traction transformer T is connected to the primary winding of the multi-winding step-down transformer T1 on the left. The n secondary windings of T1 are respectively connected to the input terminals of n four-quadrant converters on the left. The positive and negative output terminals are connected in parallel to the positive and negative DC buses D1 and D2, respectively. The right side is similar. The positive and negative input terminals of the three-phase grid-connected inverter N, and the two ends of the supporting capacitor C are respectively connected to D1 and D2. The output terminal of N is connected to the primary winding of the grid-connected step-up transformer T3 through an LCL filter F. The secondary winding of T3 is connected to the incoming terminal of the 10kV distribution network. The beneficial effects of this invention are that it effectively utilizes the regenerative braking energy generated by the high-speed train during braking, realizes dynamic energy feedback according to the regenerative braking conditions and load power, provides power to the 10kV distribution network load, improves the utilization rate of regenerative energy, and reduces the pressure on the 10kV distribution network.

Description

Technical Field

[0001] The present invention relates to the field of traction power supply systems, and in particular to a high-speed railway regenerative energy feedback system and a control method thereof. Background Art

[0002] High-speed railways have the advantages of high speed, large capacity and good safety, and have developed rapidly in recent years. During the braking process, high-speed EMUs give priority to regenerative braking, that is, the working mode of the motor is changed from traction power consumption mode to braking power generation mode, and the kinetic energy of the EMU is converted into electrical energy to achieve EMU braking. The regenerative braking method has less mechanical wear and more stable braking, which is especially suitable for non-emergency braking. This braking method will generate electrical energy (regenerative energy). At present, the better way to deal with this part of regenerative energy is: (1) It is used by another EMU in traction condition (non-regenerative condition) on the same power supply arm of the traction system, but the probability of there being another EMU in traction condition on the same power supply arm is not high, and its utilization rate needs to be improved. (2) It is consumed by the braking resistor in the form of heat energy; this method not only wastes energy, but also causes the car body to heat up and reduces the comfort of the ride. (3) It is directly returned to the high-voltage power system through the traction transformer, but it will cause the three-phase imbalance of the power system, generate harmonic current, and lead to a decrease in power quality. (4) Feedback type regenerative braking energy recovery, its approach is to connect a single-phase rectifier and a three-phase inverter to each power supply arm, and the regenerative braking energy on each power supply arm is fed back to the three phases of other voltage levels (10kV, 35kV) distribution network after single-phase rectification and three-phase inverter, solving the problem of three-phase imbalance of feedback power. However, the adjacent power supply arms cannot carry out energy circulation, and each power supply arm requires a set of single-phase rectifier and three-phase inverter. Its structure and control are complex, the cost is high, and it does not help to eliminate the three-phase imbalance and harmonics caused by the locomotive load in the high-voltage power system on the high-voltage side of the traction transformer. Summary of the invention

[0003] The object of the present invention is to provide a high-speed railway regenerative braking energy feedback system and a control method thereof, the system has high utilization rate of the regenerative braking energy of the high-speed railway train, simple structure, easy control, low cost, and is beneficial to the elimination of three-phase imbalance and harmonics caused by the locomotive load in the high-voltage power system on the high-voltage side of the traction transformer, and has high utilization rate of the regenerative braking energy of the high-speed railway train.

[0004] The technical solutions adopted to achieve the purpose of the present invention are as follows:

[0005] A high-speed railway regenerative braking energy feedback system,

[0006] The left power supply arm of the V / x connection traction transformer T is connected to the primary of the multi-winding step-down transformer T1 on the left, and the n secondary windings of T1 are respectively connected to the input ends of the n four-quadrant converters on the left; the positive output ends of the n four-quadrant converters on the left are connected in parallel to the positive DC bus D1, and the negative output ends are connected in parallel to the negative DC bus D2; the right power supply arm of T is connected to the primary of the multi-winding step-down transformer T2 on the right, and the n secondary windings of T2 are respectively connected to the input ends of the n four-quadrant converters on the right; the positive output ends of the n four-quadrant converters on the right are connected in parallel to D1, and the negative output ends are connected in parallel to D2; the positive input end and the negative input end of the three-phase grid-connected inverter N are respectively connected to D1 and D2; the two ends of the supporting capacitor C are respectively connected to D1 and D2; the output end of N is connected to the primary of the grid-connected step-up transformer T3 through the LCL filter F, and the secondary of T3 is connected to the incoming line end of the 10kV distribution network.

[0007] The control method of the high-speed railway regenerative braking energy feedback system comprises the steps of:

[0008] a. Collect the instantaneous voltage and current of the left power supply arm and the right power supply arm to obtain the instantaneous power P of the left power supply arm. L and the instantaneous power P of the right power supply arm R , and then the sum of the power of the left and right power supply arms P = P L +P R ; Collect the instantaneous voltage and current at the outlet of the 10kV distribution network to obtain the instantaneous power P of the 10kV load LOAD ; Collect the instantaneous voltage of the primary of the grid-connected step-up transformer T3, and obtain the d-axis voltage component u of the instantaneous voltage in the dq0 coordinate system through abc / dq0 coordinate system transformation d and the q-axis voltage component u q ; Collect the instantaneous current at the output end of the three-phase grid-connected inverter N, and obtain the d-axis current component i of the instantaneous current in the dq0 coordinate system through abc / dq0 coordinate system transformation d and the q-axis current component i q ;

[0009] b. By P and P LOAD , the reference feedback power P is obtained by the following formula: F ,

[0010]

[0011] Where P FM is the set maximum feedback power;

[0012] c. By P F 、u d and u q, calculate the d-axis current reference value component i of the output terminal of the three-phase grid-connected inverter N in the dq0 coordinate system d * and the q-axis current reference value component i q * ,

[0013]

[0014]

[0015] In the formula, i cd 、i cq is the component of the capacitive current of the LCL filter F in the dq0 coordinate system;

[0016] d. d * with i d Subtract the difference between the d-axis components and convert i q * with i q Subtract the q-axis component difference to obtain the q-axis component difference; after PI modulation of the d-axis component difference and the q-axis component difference, the d-axis modulation signal component U of the modulation signal of the three-phase grid-connected inverter N in the dq0 coordinate system is obtained. d and the q-axis modulation signal component U q ;

[0017] e. Through dq0 / αβ0 coordinate transformation, U d and U q The modulation signal of the three-phase grid-connected inverter N is transformed into the α-axis modulation signal component U in the αβ0 coordinate system. α and the β-axis modulation signal component U β ; for U α and U β Space vector pulse width modulation is performed to obtain 6 switch signals of the three-phase grid-connected inverter N, and the three-phase grid-connected inverter N is controlled.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The regenerative braking energy on the two power supply arms is balanced through a four-quadrant converter. After being utilized by the EMU in traction operation, the remaining regenerative energy is fed back to the incoming line end of the 10kV distribution network through the DC bus according to the designed scheme, thereby improving the utilization efficiency of regenerative braking energy.

[0020] (2) The two power supply arms share a feedback device, which has a simple structure, easy control and low cost;

[0021] (3) By designing a feedback scheme, accurate feedback can be achieved according to the regenerated power and the 10kV load power according to load demand, with little impact on the 10kV distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a topological diagram of the high-speed railway regenerative braking energy feedback system under the V / x connected traction transformer;

[0023] Figure 2 This is the control principle diagram of the high-speed railway regenerative braking energy feedback system;

[0024] Figure 3 Schematic diagram of system energy flow under four typical operating conditions. DETAILED DESCRIPTION

[0025] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings.

[0026] Figure 1 This is a schematic diagram of the topological structure of the high-speed railway regenerative braking energy feedback system under the V / x limit traction transformer.

[0027] The feedback device includes: multiple four-quadrant converters (B), three-phase grid-connected inverters (N) and LCL filters (F), each of which is installed in a container. Among them, the multiple four-quadrant converter (B) uses multiple groups of four-quadrant converters in parallel to increase the output power; the three-phase grid-connected inverter (N) uses the 10kV distribution network voltage as the standard to convert the input DC power into the output three-phase AC power to achieve DC power unit power factor inversion; the LCL filter (F) is located between the three-phase grid-connected inverter (N) and the grid-connected step-up transformer (T3) to filter out the harmonics of the output current of the three-phase grid-connected inverter (N).

[0028] The specific connection method of the system is:

[0029] The left power supply arm of the V / x connection traction transformer (T) is connected to the primary of the left multi-winding step-down transformer (T1), and the secondary winding of the left multi-winding step-down transformer (T1) is connected to the corresponding left four-quadrant converter (B) in the left multi-quadrant converter (B). i ) input terminal; all the positive output terminals (B) of the left four-quadrant converter are connected in parallel to the positive DC bus (D1), and all the negative output terminals (B) of the left four-quadrant converter are connected in parallel to the negative DC bus (D2);

[0030] The right power supply arm of the V / x connection traction transformer (T) is connected to the primary of the right multi-winding step-down transformer (T2), and the secondary winding of the right multi-winding step-down transformer (T2) is connected to the corresponding right four-quadrant converter (B) in the right multi-quadrant converter (B i) input terminal; all the positive output terminals (B) of the right four-quadrant converter are connected in parallel to the positive DC bus (D1), and all the negative output terminals (B) of the right four-quadrant converter are connected in parallel to the negative DC bus (D2);

[0031] The positive DC bus (D1) and the negative DC bus (D2) are respectively connected to the positive input terminal and the negative input terminal of the three-phase grid-connected inverter (N), and a support capacitor (C) is connected between the positive DC bus (D1) and the negative DC bus (D2); the output terminal of the three-phase grid-connected inverter (N) is connected to the primary terminal of the grid-connected boost transformer (T3) through an LCL filter (F), and the secondary terminal of the boost transformer (T3) is connected to the incoming line terminal of the 10kV distribution network.

[0032] The control method of the high-speed railway regenerative braking energy feedback system is shown in the control block diagram. Figure 2 shown.

[0033] a. Collect the instantaneous electrical quantities required by the control method and perform calculation or transformation processing. The specific process is as follows:

[0034] The instantaneous electrical quantities to be collected include: the voltage and current of the left and right power supply arms, the voltage and current of the 10kV distribution network outlet, the voltage of the grid-connected step-up transformer inlet, and the LCL filter capacitor current;

[0035] The calculation process includes: calculating the left power supply arm power P from the instantaneous voltage and current of the left power supply arm and the right power supply arm L , right power supply arm power P R , and then get the power of the left and right power supply arms and P, P = P L +P R , the 10kV load power P is calculated from the voltage and current at the outlet of the 10kV distribution network. LOAD ;

[0036] The transformation process includes: the voltage at the inlet end of the grid-connected step-up transformer is transformed into the d-axis voltage component u of the inlet end voltage of the grid-connected step-up transformer in the dq0 coordinate system through the abc-dq0 coordinate system d , q-axis voltage component u q The output side current of the three-phase grid-connected inverter is transformed into the d-axis current component i of the output side current of the three-phase grid-connected inverter in the dq0 coordinate system by abc / dq0 coordinate system transformation. d , q-axis current component i q ; The LCL filter capacitor current is transformed into the abc-dq0 coordinate system to obtain the d-axis voltage component i of the LCL filter capacitor current in the dq0 coordinate system cd , q-axis voltage component i cq ;

[0037] b. Determine the system operating conditions and obtain the reference feedback power under the operating conditions. The specific process is as follows:

[0038] The reference quantities required to determine the system operating conditions include: the sum of the power of the left and right power supply arms P, the instantaneous power of the 10kV load P LOAD and the maximum feedback power P FM , where P FM Given according to the actual equipment installation situation.

[0039] The system has four typical working conditions, each of which has its reference feedback power:

[0040] 1) Typical working condition 1: After power balancing, the total power of the two power supply arms P>0, there is no residual regenerative braking energy, so the power required by the 10kV load is all provided by the 10kV distribution network, refer to the feedback power P F = 0, the energy flow diagram under this condition is as follows Figure 3 (a)

[0041] 2) Typical working condition 2: After power balancing, the total power of the two power supply arms is P<0, there is residual regenerative braking energy, and the 10kV load power is within the maximum feedback power range, that is, P LOAD <P FM , and the remaining regenerative braking power meets the total power demand of the 10kV load, that is, P LOAD <-P (or 10kV load power is outside the maximum feedback power range, that is, P LOAD >P FM , and the remaining regenerative braking power does not meet the maximum feedback power requirement, that is, -P <P FM ), so the power required by the 10kV load can be fully provided by the feedback device, refer to the feedback power P F =P LOAD The energy flow diagram under this condition is as follows: Figure 3 (b)

[0042] 3) Typical working condition 3: After power balancing, the total power of the two power supply arms is P<0, there is residual regenerative braking energy, and the 10kV load power is within the maximum feedback power range, that is, P LOAD <P FM , and the remaining regenerative braking power meets the power demand of the 10kV load, that is, P LOAD >-P, so the power required by the 10kV load is provided by the feedback device, refer to the feedback power P F =-P, the energy flow diagram under this condition is as follows Figure 3 (c)

[0043] 4) Typical working condition 4: After power balancing, the total power of the two power supply arms is P<0, there is residual regenerative braking energy, and the 10kV load power is outside the maximum feedback power range, that is, PLOAD >P FM , and the remaining regenerative braking power meets the maximum feedback power requirement, that is, -P>P FM Therefore, the power required by the 10kV load is provided by the feedback device, referring to the feedback power P F =P FM The energy flow diagram under this condition is as follows: Figure 3 (d)

[0044] c. Calculate the d-axis current reference value component i of the output side current reference value of the three-phase grid-connected inverter in the dq0 coordinate system d * and the q-axis current reference value component i q * The specific process is:

[0045] The reference quantities required for calculation include: reference feedback power P F , the d-axis voltage component u of the voltage at the inlet end of the grid-connected step-up transformer in the dq0 coordinate system d and the q-axis voltage component u q , the d-axis voltage component i of the LCL filter capacitor current in the dq0 coordinate system cd and the q-axis voltage component i cq ;

[0046] like Figure 2 As shown in "Reference Current Calculation", the calculation steps include:

[0047] Before introducing capacitor current feedforward, calculate the d-axis current reference value component i of the output side current reference value of the three-phase grid-connected inverter in the dq0 coordinate system d *’ and the q-axis current reference value component i q *’ ,

[0048]

[0049]

[0050] After the capacitor current feedforward is introduced, the d-axis current reference value component i of the output side current reference value of the three-phase grid-connected inverter in the dq0 coordinate system is calculated. d * and the q-axis current reference value component i q * ,

[0051]

[0052]

[0053] d. Calculate the d-axis modulation signal component U of the three-phase grid-connected inverter modulation signal in the dq0 coordinate system d and the q-axis modulation signal component U q , the specific process is as follows;

[0054] The reference quantities required for calculation include: the d-axis current reference value component i of the output side current reference value of the three-phase grid-connected inverter in the dq0 coordinate system d * and the q-axis current reference value component i q * , the d-axis current component i of the output side current of the three-phase grid-connected inverter in the dq0 coordinate system d and the q-axis current component i q ;

[0055] like Figure 2 As shown in the "current loop" in Figure 2, the calculation steps include:

[0056] The d-axis current reference value component i of the output side current reference value of the three-phase grid-connected inverter in the dq0 coordinate system d * The d-axis current component i of the output side current of the three-phase grid-connected inverter in the dq0 coordinate system d Subtract to get the d-axis component difference;

[0057] The q-axis current reference value component i of the output side current reference value of the three-phase grid-connected inverter in the dq0 coordinate system is q * The q-axis current component i of the output side current of the three-phase grid-connected inverter in the dq0 coordinate system q Subtract to get the q-axis component difference;

[0058] The d-axis component difference and the q-axis component difference are used as the input of the PI regulator. After modulation by the PI regulator, the d-axis modulation signal component U of the three-phase grid-connected inverter modulation signal in the dq0 coordinate system is obtained. d and the q-axis modulation signal component U q ;

[0059] e. Use space vector pulse width modulation technology to generate switching signals, thereby controlling the three-phase grid-connected inverter to generate reference feedback power P F The corresponding output current, the specific process is,

[0060] like Figure 2 As shown in "Pulse Wave Generation", the calculation steps include:

[0061] Through dq0 / αβ0 coordinate transformation, the d-axis modulation signal component U of the three-phase grid-connected inverter modulation signal in the dq0 coordinate system is converted into d and the q-axis modulation signal component U qThe α-axis modulation signal component U of the three-phase grid-connected inverter modulation signal in the αβ0 coordinate system is obtained by transformation. α and the β-axis modulation signal component U β ;

[0062] The α-axis modulation signal component U of the three-phase grid-connected inverter modulation signal in the αβ0 coordinate system α and the β-axis modulation signal component U β Space vector pulse width modulation is performed to obtain 6 switching signals of the three-phase grid-connected inverter, and then the three-phase grid-connected inverter is controlled to generate corresponding output current.

Claims

1. A high-speed railway regenerative braking energy feedback system, characterized in that: The left power supply arm of the V / x connection traction transformer T is connected to the primary of the multi-winding step-down transformer T1 on the left, and the n secondary windings of T1 are respectively connected to the input ends of the n four-quadrant converters on the left; the positive output ends of the n four-quadrant converters on the left are connected in parallel to the positive DC bus D1, and the negative output ends are connected in parallel to the negative DC bus D2; The right power supply arm of T is connected to the primary of the multi-winding step-down transformer T2 on the right, and the n secondary windings of T2 are respectively connected to the input ends of the n four-quadrant converters on the right; the positive output ends of the n four-quadrant converters on the right are connected in parallel to D1, and the negative output ends are connected in parallel to D2; The positive input terminal and the negative input terminal of the three-phase grid-connected inverter N are connected to D1 and D2 respectively; the two ends of the supporting capacitor C are connected to D1 and D2 respectively; the output terminal of N is connected to the primary of the grid-connected step-up transformer T3 through the LCL filter F, and the secondary of T3 is connected to the incoming line terminal of the 10kV distribution network; The control method of the high-speed railway regenerative braking energy feedback system comprises the steps of: a. Collect the instantaneous voltage and current of the left power supply arm and the right power supply arm to obtain the instantaneous power P of the left power supply arm. L and the instantaneous power P of the right power supply arm R , and then the sum of the power of the left and right power supply arms P = P L +P R ; Collect the instantaneous voltage and current at the outlet of the 10kV distribution network to obtain the instantaneous power P of the 10kV load LOAD ; The instantaneous voltage of the primary of the grid-connected step-up transformer T3 is collected, and the d-axis voltage component u of the instantaneous voltage in the dq0 coordinate system is obtained by abc / dq0 coordinate system transformation. d and the q-axis voltage component u q ; The instantaneous current at the output end of the three-phase grid-connected inverter N is collected, and the d-axis current component i of the instantaneous current in the dq0 coordinate system is obtained by transforming the abc / dq0 coordinate system. d and the q-axis current component i q ; b. By P and P LOAD , the reference feedback power P is obtained by the following formula: F , Where P FM is the set maximum feedback power; c. By P F 、u d and u q , calculate the d-axis current reference value component i of the output terminal of the three-phase grid-connected inverter N in the dq0 coordinate system d * and the q-axis current reference value component i q * , In the formula, i cd 、i cq is the component of the capacitive current of the LCL filter F in the dq0 coordinate system; d. d * with i d Subtract the difference between the d-axis components and convert i q * with i q Subtract to get the q-axis component difference; After PI modulation of the d-axis component difference and the q-axis component difference, the d-axis modulation signal component U of the modulation signal of the three-phase grid-connected inverter N in the dq0 coordinate system is obtained. d and the q-axis modulation signal component U q ; e. Through dq0 / αβ0 coordinate transformation, U d and U q The modulation signal of the three-phase grid-connected inverter N is transformed into the α-axis modulation signal component U in the αβ0 coordinate system. α and the β-axis modulation signal component U β ; To U α and U β Space vector pulse width modulation is performed to obtain 6 switch signals of the three-phase grid-connected inverter N, and the three-phase grid-connected inverter N is controlled.

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