Compact railway energy conditioning complex

Abstract

The present application relates to a kind of compact railway energy regulation complex, including the converter unit with the core of medium-frequency transformer, the alternating current port of each converter unit is connected with the bus of V / v traction transformer secondary side α, β phase traction feeder in series mode.Magnetic field of medium-frequency transformer is decoupled inductance and filter capacitor to form the second harmonic filter branch of the DC side of converter unit, filter out the second harmonic component that each converter unit DC side cannot be ignored in single-phase conversion system, and the power winding of medium-frequency transformer is connected with the DC / DC converter in each converter unit inside respectively.Compact railway energy regulation complex can accurately control the power flow distribution of two power supply arms, and carry out the comprehensive regulation of energy with external energy storage and new energy generation system through DC port, can effectively inhibit voltage fluctuation of feeder side, improve the comprehensive energy utilization rate and new energy consumption rate of electric railway system, compensate the power factor of substation high-voltage side and inhibit PCC point voltage unbalance degree.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrified railway energy integration control technology, and particularly relates to a compact railway energy control complex. BACKGROUND

[0002] Voltage fluctuation, negative sequence, reactive power and harmonic and other power quality problems caused by factors such as electrified railway load characteristics and traction power supply system are increasingly prominent. These problems may have adverse effects on the normal operation of various power equipment in the traction power supply system, and bring potential risks to the safe and stable operation of the traction power supply system.

[0003] Existing railway energy control equipment, such as railway power conditioner (RPC) and RPC based on modular multilevel converter (MMC), can only handle power quality problems, but cannot provide renewable energy sources (RESs) access. In addition, the traditional RPC generally needs two large-capacity single-phase multi-winding power frequency transformers to access the traction network, and a certain amount of second harmonic exists at the DC side. The filter inductance used to filter the second harmonic is large in volume and cannot be placed in the converter container, and the overall integration of the equipment is not high. SUMMARY

[0004] Therefore, it is necessary to provide a compact railway energy control complex to solve the above-mentioned defects of the prior art.

[0005] In order to solve the above-mentioned problems, the present application provides a compact railway energy control complex, which comprises a converter unit, two filter inductors, a DC bus, a fourth DCDC converter and an energy storage unit.

[0006] The converter unit comprises an intermediate frequency transformer, a first DCAC converter, a second DCAC converter, a first DCDC converter, a second DCDC converter, a third DCDC converter, two filter capacitors and three voltage stabilizing capacitors. Two AC ports of the converter unit are respectively connected to the bus of the traction feeder of the secondary side alpha and beta phase of the external traction transformer (2) through one filter inductor. The DC output port of the converter unit is connected to the DC bus in a parallel manner, and the DC bus is connected to the energy storage unit through the fourth DCDC converter.

[0007] The first DCAC converter and the first DCDC converter share one voltage stabilizing capacitor to form a back-to-back structure, the second DCAC converter and the second DCDC converter share one voltage stabilizing capacitor to form a back-to-back structure, and the third DCDC converter is connected in parallel with one voltage stabilizing capacitor; the three power windings of the intermediate frequency transformer are connected with the first DCDC converter, the second DCDC converter and the third DCDC converter respectively.

[0008] Preferably, the intermediate frequency transformer comprises two magnetic field counter-shock decoupling inductive windings and three power windings, each magnetic field counter-shock decoupling inductive winding is composed of two common core counter-wound winding strings in series; each magnetic field counter-shock decoupling inductive winding of the intermediate frequency transformer is connected in series with one filter capacitor, to form a second harmonic filter branch on the DC side of the conversion unit, each second harmonic filter branch is connected in parallel with the filter capacitors of the two back-to-back structures; the three power windings of the intermediate frequency transformer are connected with the first DCDC converter, the second DCDC converter and the third DCDC converter respectively.

[0009] Preferably, the two AC ports of the conversion unit are connected with the first DCAC converter and the second DCAC converter respectively; the DC output port of the conversion unit is connected with the third DCDC converter.

[0010] Preferably, the compact railway energy regulation complex further comprises a photovoltaic unit and a fifth DCDC converter.

[0011] The DC bus is connected with the photovoltaic unit through the fifth DCDC converter.

[0012] The present application has the following advantages:

[0013] (1) The compact railway energy regulation complex provided by the present application can save two high-power power frequency step-down transformers and secondary filter branch reactors arranged outside the converter container of the traditional RPC, thereby greatly improving the integration degree of the device and reducing the occupied area.

[0014] (2) The compact railway energy regulation complex provided by the present application, the magnetic field counter-shock decoupling inductor of the intermediate frequency transformer and the filter capacitor form a filter branch, which can effectively filter out the second harmonic on the DC side of the two-phase converter.

[0015] (3) The present application connects the alpha phase and the beta phase of the traction network through the multi-functional multi-subject intermediate frequency transformer, and can realize electrical isolation of the alpha and beta power supply networks.

[0016] (4) The compact railway energy regulation complex provided by the application can reduce the direct current voltage borne by the energy storage device through modular design, and the carrier phase shift control of each variable current unit with low switching frequency can obtain a high equivalent switching frequency of the complex, reduce switching loss of the device, reduce harmonic distortion rate, and improve operation efficiency of the device.

[0017] (5) The compact railway energy regulation complex provided by the application can make the device have the ability to cooperate with the energy storage and renewable energy system through the introduction of the energy storage and renewable energy interface, which is beneficial to improve the comprehensive energy utilization rate and new energy consumption rate of the electric railway system. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The structure diagram of the compact railway energy regulation complex provided by the application.

[0019] In the figure, 1 is a three-phase 110kV power grid, 2 is a traction transformer, 3 is an electric locomotive, 4 is a first DCAC converter, 5 is a second DCAC converter, 6 is a direct current bus, 7 is an energy storage unit, 8 is a photovoltaic unit, 9 is a filter capacitor, 10 is a filter inductor, 11 is a medium-frequency transformer, 12 is a second harmonic filter branch, 13 is a variable current unit, 14 is a first DCDC converter, 15 is a second DCDC converter, 16 is a third DCDC converter, 17 is a fourth DCDC converter, 18 is a fifth DCDC converter, and 19 is a voltage stabilizing capacitor. DETAILED DESCRIPTION

[0020] The preferred embodiments of the application will be described in detail below with reference to the accompanying drawings, wherein the accompanying drawings form a part of the present application and are used to explain the principles of the embodiments of the application, but are not used to limit the scope of the application.

[0021] In this document, reference to“an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase“in an embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. It is expressly understood that any of the embodiments described herein can be combined with any of the other embodiments unless specifically noted otherwise.

[0022] The existing railway energy regulation devices, such as railway power regulators and RPCs based on modular multi-level converters, can only deal with power quality problems and cannot provide renewable energy access. In addition, the traditional RPC generally needs two large-capacity single-phase multi-winding power frequency transformers to access the traction network, and a certain amount of second harmonic exists at the direct current side. The filter inductor used to filter the second harmonic is relatively large in volume and cannot be placed in the converter container, so the overall integration of the device is not high.

[0023] In view of this, in order to realize the "source-grid-storage-car" energy integrated regulation of electrified railway, the application provides a compact railway energy router (CRER), which omits the two high-power power frequency step-down transformers of the traditional RPC and the secondary filter branch reactor outside the converter container, thereby greatly improving the "integration degree" of the device and reducing the floor area. The following will be described and introduced through multiple embodiments.

[0024] Figure 1 The structure diagram of the compact railway energy router provided by the application is shown in the figure. Figure 1 As shown in the figure, the compact railway energy router includes a conversion unit 13, two filter inductors 10, a DC bus 6, a fourth DCDC converter 17, a fifth DCDC converter, an energy storage unit 7 and a photovoltaic unit 8.

[0025] The conversion unit 13 includes an intermediate frequency transformer 11, a first DCAC converter 4, a second DCAC converter 5, a first DCDC converter 14, a second DCDC converter 15, a third DCDC converter 16, two filter capacitors 9 and three voltage stabilizing capacitors 19. The two AC ports of the conversion unit 13 are respectively connected to the bus of the α, β phase traction feeder of the secondary side of the external traction transformer 2 through one filter inductor 10. The traction transformer 2 can adopt a three-phase V / v traction transformer, and the traction transformer 2 is connected to the three-phase 110kV power grid 1 at one end and the electric locomotive 3 at the other end. Figure 1

[0026] The DC output port of the conversion unit 13 is connected to the DC bus 6 in a parallel manner, and the DC bus 6 is connected to the energy storage unit 7 and the photovoltaic unit 8 through the fourth DCDC converter 17 and the fifth DCDC converter 18 respectively.

[0027] The first DCAC converter 4 and the first DCDC converter 14 share one voltage stabilizing capacitor 19 to form a back-to-back structure, the second DCAC converter 5 and the second DCDC converter 15 share one voltage stabilizing capacitor 19 to form a back-to-back structure, and the third DCDC converter 16 is connected to one voltage stabilizing capacitor 19 in parallel. Figure 1 The two AC ports of the conversion unit 13 are respectively connected to the first DCAC converter 4 and the second DCAC converter 5, and the DC output port of the conversion unit 13 is connected to the third DCDC converter 16.

[0028] ​The medium-frequency transformer 11 comprises two magnetic field butt-joint decoupling inductance windings and three power windings, each of the two magnetic field butt-joint decoupling inductance windings is composed of two common-iron-core counter-wound winding strings in series; each of the magnetic field butt-joint decoupling inductance windings of the medium-frequency transformer 11 is connected with a filter capacitor 9 in series to form a second harmonic filter branch 12 on the DC side of the variable current unit, each of the second harmonic filter branches 12 is connected with two filter capacitors 9 in a back-to-back structure in parallel; the three power windings of the medium-frequency transformer 11 are connected with a first DC / DC converter 14, a second DC / DC converter 15 and a third DC / DC converter 16 respectively.

[0029] Specifically, the application discloses a compact railway energy regulation complex. The compact railway energy regulation complex is composed of a plurality of variable current units 13. The AC ports of each variable current unit are connected with the bus of the traction feeder line of the secondary side alpha and beta phase of the traction transformer 2 in series, the DC output ports of the variable current units 13 are connected with the DC bus in parallel, and the DC bus is connected with the energy storage unit 7 and the photovoltaic unit 8 through the fourth DC / DC converter 17 and the fifth DC / DC converter 18. The magnetic field butt-joint decoupling inductance of the medium-frequency transformer and the filter capacitor form a second harmonic filter branch on the DC side of the variable current unit, filter out the second harmonic component on the DC side of each variable current unit in the single-phase variable current system, and the power windings of the medium-frequency transformer are connected with the DC / DC converters inside each variable current unit. The compact railway energy regulation complex CRER can accurately control the power flow distribution of the two power supply arms, comprehensively regulate the energy through the DC port and the external energy storage and new energy generation system, effectively suppress the voltage fluctuation on the feeder side, improve the comprehensive energy utilization rate and new energy consumption rate of the electric railway system, compensate the power factor on the high-voltage side of the transformer substation and suppress the voltage unbalance degree of the PCC point. Compared with the electric energy regulation device based on the basic topology of the traditional railway power regulator, the CRER has higher integration degree due to the existence of the multi-functional and multi-subject medium-frequency transformer.

[0030] As known from the above embodiment, the compact railway energy regulation complex is a highly integrated railway system energy management device, which aims to realize the integrated regulation of the “source-grid-storage-car” energy of the electrified railway. The compact railway energy regulation complex can improve the energy efficiency, stability and reliability of the electrified railway.

[0031] In a preferred embodiment of the application, the working principle of the compact railway energy regulation complex is described in detail.

[0032] Firstly, the number of the converter units is determined according to the device capacity of the compact railway energy regulation complex and the specifications of the power devices used. For a 2x5MVA device, the unilateral capacity is 5MVA. The converter in each converter unit adopts a single-phase two-level H full-bridge structure, and the bridge arm of the full-bridge structure is composed of an upper and lower insulated gate bipolar transistor (IGBT) and a diode connected in anti-parallel with the IGBT. Because the device eliminates two power frequency step-down transformers connected with the two-phase feeder, multiple converter units 13 jointly bear the feeder voltage, in order to reduce the number of converter units that need to be connected in series, the IGBT device FZ200R65KF2 (6500V / 200A) with higher withstand voltage is selected. In order to ensure the service life of the IGBT, the reverse voltage borne by the IGBT during operation is usually half of the DC voltage (not higher than 80% of the withstand voltage), that is, the DC voltage U dc of the two-side converters is 3200V. Considering a 5% voltage fluctuation of the DC side voltage, when SPWM modulation is used and the modulation ratio is 0.8, the rated voltage of the single H-bridge AC side is 3200Vx0.95x0.8 / 1.414≈1720V, the rated capacity of the single H-bridge converter is 1.72kVx0.2kA=0.344MVA, and the number N of the converter unit 13 modules should be not less than 5MVA / 0.344MVA≈15. Considering that the highest voltage of the traction bus is 1.1 times the rated voltage, that is, the highest voltage is 1.1x27.5kV=30.25kV, the output voltage of the device should be slightly greater than this value, and considering comprehensively, the number N of the basic converter units 13 is 18, at this time the rated voltage of the AC side of the device is 18x1.72kV=30.96kV. The selection of the filter inductance 10 needs to meet the requirement that the device can operate in four quadrants. At the same time, considering that a larger filter inductance can reduce the harmonic distortion rate of the output current and limit the current rise rate, in the embodiment, the filter inductance 10 is 11mH. Considering the lower rated voltage of the DC bus 6, the reliability reduction caused by the large number of components connected in series for voltage boosting in the energy storage unit 7 and the photovoltaic unit 8 device can be avoided, in the embodiment, the rated voltage of the DC bus 6 is 320V. Considering the lower switching loss, the phase difference φ between the voltages of the two power windings in the medium-frequency transformer is selected as 0.3π. Considering the design difficulty of the transformer, the short-circuit impedance per unit of the three power windings U k % can be 0.1, the transformation ratio is 3200V:3200V:320V, and the three power windings are connected with the first DC / DC converter 14, the second DC / DC converter 15 and the third DC / DC converter 16 of the converter respectively. Considering the rated frequency f sFor 1000 Hz, the capacity of a single H-bridge inverter is at least 5 MVA / 18 = 0.278 MVA, and considering the 1.25 times overload capacity of the inverter, the rated capacity of the intermediate frequency transformer is taken as 1.1 MVA, and the rated capacity ratio of the three power windings is 1:1:1. Through the above intermediate frequency transformer selection parameters, the power winding of the transformer 3.2 kV side can be calculated as 2.9 mH. Since the secondary filter circuit is set, the capacitance value of the voltage stabilizing capacitor 19 mainly considers the reactive power, transient current support and DC side filtering of the load. The capacitance value of the voltage stabilizing capacitor 19 is related to: C d ≥ 10P N / (kωU2 dc ), P N is 1.1 MVA, k is the input voltage phase number, which is 1, ω is the system angular frequency, which is 2π×50, U dc is the DC voltage, which is 3200V, and C d is calculated to be 3.42 mF, and considering that a larger value can achieve better voltage stabilization effect, the three voltage stabilizing capacitors 19 in this embodiment are all taken as 5 mF. The inductance value L2 and the capacitance value C2 of the secondary harmonic filter branch should satisfy the relationship L2C2n2ω2=1, where n is the harmonic number to be filtered out, which is 2, and ω is the system angular frequency, which is 100π. The capacitance value C2 of the secondary harmonic filter branch satisfies the following relationship: U C2 =U dcmax +I dc2 / (2πf c C2), where the rated voltage of the capacitor U C2 is 3500V, the maximum voltage fluctuation of the DC side U dcmax is not more than 105%×3200V, the filter branch current I dc2max = P N / U dc = 486.13A, the resonance frequency f c is 2×50Hz, and the calculated filter capacitance 9 capacitance value C2 is not less than 5.53 mF, which can be taken as C2=6 mF. According to the relationship L2C2n2ω2=1, the inductance value L2 is calculated as 0.422 mH, so the inductance value of each of the two common-iron-core counter-wound windings of the multifunctional-multi-subject intermediate frequency transformer 11 is taken as 0.211 mH.

[0033] The first DCDC converter 14 and the second DCDC converter 15 receive active regulation instructions from the power distribution layer, and the fourth DCDC converter 17 and the fifth DCDC converter 18 receive the "storage" and "source" regulation instructions calculated by the GOB. The regulation instructions of the first DCAC converter 4, the second DCAC converter 5 and the third DCDC converter 16 of the compact railway energy regulation complex are taken as the control target (external control loop) to maintain the stability of the DC side voltage. The internal control loop of the first DCAC converter 4, the second DCAC converter 5, the fourth DCDC converter 17 and the fifth DCDC converter 18 is taken as a slave control unit, and the output of the respective external control loop is taken as a reference current to realize current tracking, thereby shortening the regulation time of the control target. The PI controller is used to divide the total DC voltage reference value by the number of basic converter units to obtain the DC voltage reference value of each converter unit, thereby realizing the stable control of the total DC voltage of the compact railway energy regulation complex, and realizing the current sharing of the basic converter units through the current control loop.

[0034] Compared with the prior art, the compact railway energy regulation complex has the following beneficial effects:

[0035] (1) The compact railway energy regulation complex can save two large power frequency step-down transformers of the traditional RPC and the secondary filter branch reactor outside the converter container, thereby greatly improving the "integration" of the device and reducing the floor area.

[0036] (2) The compact railway energy regulation complex can effectively filter out the second harmonic of the DC side of the two-phase converter through the filter branch composed of the magnetic field of the intermediate frequency transformer, the decoupling inductance and the filter capacitor.

[0037] (3) The multifunctional multi-subject intermediate frequency transformer can realize the electrical isolation of the alpha and beta power supply networks.

[0038] (4) The compact railway energy regulation complex can reduce the DC voltage borne by the energy storage device through modular design, and the carrier phase shift control of each converter unit with a low switching frequency can obtain a high equivalent switching frequency of the complex, thereby reducing the switching loss of the device, reducing the harmonic distortion rate and improving the operation efficiency of the device.

[0039] (5) The compact railway energy regulation complex can realize the collaborative operation of the device with the energy storage and renewable energy system through the introduction of the energy storage and renewable energy interface, thereby being beneficial to improving the comprehensive energy utilization rate and new energy consumption rate of the electric railway system.

[0040] The above embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but should not be understood as a limitation on the patent scope of the present application. It should be noted that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

[0041] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A compact railway energy conditioning complex, characterized in that, The converter unit (13) includes an intermediate frequency transformer (11), a first DCAC converter (4), a second DCAC converter (5), a first DCDC converter (14), a second DCDC converter (15), a third DCDC converter (16), two filter capacitors (9), and three voltage stabilizing capacitors (19); two alternating current ports of the converter unit (13) are respectively connected to the bus of the α and β phase traction feeder lines on the secondary side of the external traction transformer (2) through one filter inductor (10); the direct current output port of the converter unit (13) is connected to the direct current bus (6) in a parallel manner, and the direct current bus (6) is connected to the energy storage unit (7) through the fourth DCDC converter (17). The first DCAC converter (4) and the first DCDC converter (14) share one voltage stabilizing capacitor (19) to form a back-to-back structure, the second DCAC converter (5) and the second DCDC converter (15) share one voltage stabilizing capacitor (19) to form a back-to-back structure, and the third DCDC converter (16) is connected to one voltage stabilizing capacitor (19) in parallel; three power windings of the intermediate frequency transformer (11) are respectively connected to the first DCDC converter (14), the second DCDC converter (15), and the third DCDC converter (16); each magnetic field pair collision decoupling inductor winding of the intermediate frequency transformer (11) is connected to one filter capacitor (9) in series, thereby constituting a second harmonic filter branch (12) on the direct current side of the converter unit, and each second harmonic filter branch (12) is connected to the voltage stabilizing capacitors (19) on both sides of the back-to-back structure in parallel. The intermediate frequency transformer (11) includes two magnetic field pair collision decoupling inductor windings and three power windings, and each magnetic field pair collision decoupling inductor winding is composed of two common core reverse-wound windings connected in series; the three power windings of the intermediate frequency transformer (11) are respectively connected to the first DCDC converter (14), the second DCDC converter (15), and the third DCDC converter (16).

2. The compact railway energy conditioning complex of claim 1, wherein, The two alternating current ports of the converter unit (13) are respectively connected to the first DCAC converter (4) and the second DCAC converter (5); and the direct current output port of the converter unit (13) is connected to the third DCDC converter (16).

3. The compact railway energy regulating complex according to claim 1, characterized in that, The compact railway energy regulation complex further includes a photovoltaic unit (8) and a fifth DCDC converter.

4. The compact railway energy regulating complex according to claim 1, characterized in that, The direct current bus (6) is connected to the photovoltaic unit (8) through the fifth DCDC converter (18). ​

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