Compact railway energy regulation and control complex

Abstract

The invention relates to a compact railway energy regulation and control complex which comprises a converter unit with an intermediate frequency transformer as a core, and an alternating current port of each converter unit is connected with buses of alpha and beta phase traction feeder lines on the secondary side of a V / v traction transformer in series. A magnetic field hedging decoupling inductor and a filter capacitor of the medium-frequency transformer form a secondary harmonic filter branch on the direct current side of each converter unit, non-negligible secondary harmonic components on the direct current side of each converter unit in the single-phase converter system are filtered out, and a power winding of the medium-frequency transformer is connected with a DC / DC converter on the inner side of each converter unit. The compact railway energy regulation and control complex can accurately control the tidal current distribution of the two power supply arms, carries out comprehensive energy regulation and control through a direct current port and an external energy storage and new energy power generation system, can effectively inhibit the voltage fluctuation of a feeder line side, improves the comprehensive energy utilization rate and the new energy consumption rate of an electric railway system, and improves the energy utilization rate of the electric railway system. Compensating the power factor of the high-voltage side of the transformer substation and inhibiting the voltage unbalance degree of the PCC point.

Description

Technical Field

[0001] The invention relates to the technical field of integrated energy control of electrified railways, and in particular to a compact railway energy control complex. Background Art

[0002] Power quality issues such as voltage fluctuation, negative sequence, reactive power and harmonics caused by factors such as the load characteristics of electrified railways and traction power supply systems are becoming increasingly prominent. These issues may have an adverse impact on the normal operation of various power equipment in the traction power supply system, bringing potential risks to the safe and stable operation of the traction power supply system.

[0003] Existing railway energy control equipment, such as Railway Rower Ronditioner (RPC) and RPC based on Modular Multilevel Converter (MMC), can only deal with power quality issues, but cannot provide access to renewable energy sources (RESs). In addition, traditional RPC generally requires two large-capacity single-phase multi-winding power frequency transformers to access the traction network, and there is a certain amount of second harmonics on the DC side. The filter inductor used to filter out the second harmonics is large in size and cannot be placed in the converter container, so the overall integration of the equipment is not high. Summary of the invention

[0004] In view of this, 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 problems, an embodiment of the present invention provides a compact railway energy control complex, including a converter unit, two filter inductors, a DC bus, a fourth DCDC converter and an energy storage unit;

[0006] The converter unit comprises a medium 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; the two AC ports of the converter unit are respectively connected to the busbars of the α-phase and β-phase traction feeder lines on the secondary side of the external traction transformer (2) through a filter inductor; the DC output port of the converter unit is connected to the DC busbar in parallel, and the DC busbar is connected to the energy storage unit through a fourth DCDC converter;

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

[0008] Preferably, the intermediate frequency transformer includes two magnetic field hedging decoupling inductor windings and three power windings, each magnetic field hedging decoupling inductor winding is composed of two windings with a common iron core and reversely wound in series; each magnetic field hedging decoupling inductor winding of the intermediate frequency transformer is respectively connected in series with a filter capacitor to form a second harmonic filter branch on the DC side of the converter unit, and each second harmonic filter branch is respectively connected in parallel with the filter capacitors of back-to-back structures on both sides; the three power windings of the intermediate frequency transformer are respectively connected to the first DCDC converter, the second DCDC converter and the third DCDC converter.

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

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

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

[0012] The beneficial effects of the present invention are:

[0013] (1) The compact railway energy control complex provided by the present invention can save the two high-power industrial frequency step-down transformers of the traditional RPC and the secondary filter branch reactor placed outside the converter container, which will greatly improve the "integration" of the device and reduce the floor space.

[0014] (2) In the compact railway energy control complex provided by the present invention, the magnetic field hedging decoupling inductor of the medium frequency transformer and the filter capacitor form a filter branch, which can effectively filter out the second harmonics on the DC side of the two-phase converter.

[0015] (3) The present invention connects the α-phase and β-phase of the traction network through a multifunctional-multi-body medium frequency transformer, thereby achieving electrical isolation of the α-phase and β-phase power supply networks.

[0016] (4) The compact railway energy control complex provided by the present invention reduces the DC voltage borne by the energy storage device through a modular design. The carrier phase shift control of each converter unit with a low switching frequency can obtain a higher equivalent switching frequency of the complex, reduce the switching loss of the device, reduce the harmonic distortion rate, and improve the operating efficiency of the device.

[0017] (5) The compact railway energy control complex provided by the present invention, by introducing an energy storage and renewable energy interface, enables the device to have the ability to operate in coordination with the energy storage and renewable energy systems, which is beneficial to improving the comprehensive energy utilization rate and new energy consumption rate of the electric railway system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic structural diagram of the compact railway energy control complex provided by the present invention.

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

[0020] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0021] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0022] Existing railway energy control equipment, such as railway power conditioners and RPCs based on modular multilevel converters, can only handle power quality issues, but cannot provide access to renewable energy. In addition, traditional RPCs generally require two large-capacity single-phase multi-winding power frequency transformers to access the traction network, and there is a certain amount of second harmonics on the DC side. The filter inductor used to filter out the second harmonics is large and cannot be placed in the converter container, so the overall integration of the equipment is not high.

[0023] In view of this, in order to realize the integrated energy control of "source-grid-storage-vehicle" of electrified railways, the present invention provides a compact railway energy control complex (Compacted Railway Energy Router, CRER), which eliminates the two high-power power frequency step-down transformers of the traditional RPC and the secondary filter branch reactor placed outside the converter container, which will greatly improve the "integration" of the device and reduce the floor space. The following will be explained and introduced through multiple embodiments.

[0024] Figure 1 The schematic diagram of the structure of the compact railway energy control complex provided by the present invention. Figure 1 As shown, the compact railway energy control complex includes a converter 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 converter unit 13 includes a medium 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 converter unit 13 are respectively connected to the busbars of the α and β phase traction feeder lines on the secondary side of the external traction transformer 2 through a filter inductor 10; wherein the traction transformer 2 can be a three-phase V / v traction transformer, refer to Figure 1 One end of the traction transformer 2 is connected to the three-phase 110kV power grid 1, and the other end is connected to the electric locomotive 3.

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

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

[0028] The intermediate frequency transformer 11 includes two magnetic field hedging decoupling inductor windings and three power windings, each of which is composed of two windings with a common iron core and reversely wound in series; each magnetic field hedging decoupling inductor winding of the intermediate frequency transformer 11 is respectively connected in series with a filter capacitor 9 to form a second harmonic filter branch 12 on the DC side of the converter unit, and each second harmonic filter branch 12 is respectively connected in parallel with the filter capacitors 9 with back-to-back structures on both sides; 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.

[0029] Specifically, the present invention discloses a compact railway energy control complex. The compact railway energy control complex is composed of a plurality of converter units 13. The AC port of each converter unit is connected in series to the busbars of the α and β phase traction feeders on the secondary side of the traction transformer 2, and the DC output port of the converter unit 13 is connected in parallel to the DC busbar, which is respectively connected to the energy storage unit 7 and the photovoltaic unit 8 through the fourth DCDC converter 17 and the fifth DCDC converter 18. The magnetic field hedging decoupling inductor and the filter capacitor of the medium frequency transformer constitute the secondary harmonic filter branch on the DC side of the converter unit, filtering out the non-negligible secondary harmonic components on the DC side of each converter unit in the single-phase converter system, and the power winding of the medium frequency transformer is respectively connected to the DC / DC converter inside each converter unit. The compact railway energy control complex CRER can accurately control the power flow distribution of the two power supply arms, and conduct comprehensive energy control with external energy storage and new energy power generation systems through the DC port. It can effectively suppress voltage fluctuations on the feeder side, improve the comprehensive energy utilization rate and new energy consumption rate of the electric railway system, compensate for the power factor on the high-voltage side of the substation and suppress the voltage imbalance at the PCC point. Due to the presence of the multi-functional and multi-subject medium-frequency transformer, CRER has a higher "integration" compared with the power control device with the traditional railway power conditioner as the basic topology.

[0030] From the above embodiments, it can be seen that the compact railway energy control complex is a highly integrated railway system energy management device, which is designed to achieve the integrated control of "source-grid-storage-vehicle" energy of electrified railways, and can improve the energy efficiency, stability and reliability of electrified railways.

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

[0032] First, the number of converter units is determined according to the device capacity of the compact railway energy control complex and the specifications of the power devices used. For a 2×5MVA device, its single-side 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 two upper and lower insulated gate bipolar transistors IGBT and a diode connected in anti-parallel with the IGBT. Because the device omits two power-frequency step-down transformers connected to the two-phase feeder lines, 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, an IGBT device FZ200R65KF2 (6500V / 200A) with a higher withstand voltage is selected. In order to ensure the service life of the IGBT, the reverse voltage that the IGBT bears during operation is usually half of the DC voltage (not exceeding 80% of the withstand voltage), that is, the DC voltage U of the converters on both sides is taken. dc 3200V. Considering the voltage fluctuation of 5% on the DC side, when SPWM modulation is adopted and the modulation ratio is 0.8, the rated voltage on the AC side of a single H-bridge is 3200V×0.95×0.8 / 1.414≈1720V, the rated capacity of a single H-bridge converter is 1.72kV×0.2kA=0.344MVA, and the number of converter units 13 modules N should be no less than 5MVA / 0.344MVA≈15. Considering that the maximum voltage of the traction bus is 1.1 times the rated voltage, that is, when the maximum voltage is 1.1×27.5kV=30.25kV, the output voltage of the device should be slightly greater than this value. After comprehensive consideration, the number of basic converter units 13 N is 18, and the rated voltage on the AC side of the device is 18×1.72kV=30.96kV. The selection of the filter inductor 10 must meet the requirement that the device can operate in the four quadrants. At the same time, considering that a larger filter inductor can reduce the output current harmonic distortion rate and limit the current rise rate, the filter inductor 10 in this embodiment is 11mH. Considering the lower rated voltage of the DC bus 6, the reliability reduction caused by the series voltage boost of a large number of components in the energy storage unit 7 and the photovoltaic unit 8 can be avoided. In this embodiment, the rated voltage of the DC bus 6 is 320V. Considering the lower switching loss, the voltage phase difference φ between the two power windings in the medium frequency transformer is selected to be 0.3π. Considering the difficulty of transformer design, the short-circuit impedance per unit value U of the three power windings is k % can be taken as 0.1, the transformation ratio is 3200V:3200V:320V, and the three power windings are respectively connected to the first DCDC converter 14, the second DCDC converter 15 and the third DCDC converter 16. Considering the rated frequency f of the medium frequency transformer sThe frequency is 1000Hz, considering that the capacity of a single H-bridge converter is at least 5MVA / 18=0.278MVA, and considering the converter's 1.25 times overload capacity, the rated capacity of the medium-frequency transformer is 1.1MVA, and the rated capacity ratio of the three power windings is 1:1:1. Through the above medium-frequency transformer selection parameters, it can be calculated that the power frequency leakage inductance of the power winding on the 3.2kV ​​side of the transformer is 2.9mH. Since a secondary filtering circuit is set up, the capacitance of the voltage-stabilizing capacitor 19 mainly considers the reactive power of the load, instantaneous current support and DC side filtering. The capacitance relationship of the voltage-stabilizing capacitor 19 is: C d ≥10P N / (kωU2 dc ), P N The rated capacity is 1.1MVA, k is the number of input voltage phases, 1, ω is the system angular frequency, 2π×50, U dc Take 3200V as the DC voltage and calculate C d The minimum value is 3.42 mF. Considering that a larger value can achieve a better voltage stabilization effect, the values ​​of the three voltage stabilization capacitors 19 in this embodiment are all 5 mF. 2 and capacitance C 2 To satisfy the relation L 2 C 2 n2ω2=1, where n is the harmonic order to be filtered out, which is 2, and ω is the system angular frequency, which is 100π. The capacitance value of the second harmonic filter branch C 2 There is the following relationship: U C2 =U dcmax +I dc2 / (2πf c C 2 ), where the capacitor rated voltage U C2 The maximum voltage fluctuation on the DC side is 3500V. dcmax Not more than 105%×3200V, filter branch current I dc2max =P N / U dc =486.13A, resonant frequency f c Take 2×50Hz and calculate the capacitance value of filter capacitor 9 C 2 Not less than 5.53mF, C is acceptable 2 =6mF, according to the relationship L 2 C 2 n2ω2=1, the inductance value L is calculated 2 It is 0.422mH, so the inductance values ​​of the two common core reversely wound windings of the multi-function-multi-body medium frequency transformer 11 are each 0.211mH.

[0033] Among them, the first DCDC converter 14 and the second DCDC converter 15 receive the active control instructions issued by the power distribution layer, and the fourth DCDC converter 17 and the fifth DCDC converter 18 receive the "storage" and "source" control instructions calculated by the GOB. By giving the first DCAC converter 4, the second DCAC converter 5 and the third DCDC converter 16 of the compact railway energy control complex control instructions to maintain the stability of the DC side voltage as the control target (outer control loop). The inner control loops of the first DCAC converter 4, the second DCAC converter 5, the fourth DCDC converter 17 and the fifth DCDC converter 18 are used as subordinate control units, and the output of each outer control loop is used as the parameter current to achieve current tracking, shortening the adjustment time of each control target. Through the PI controller, the result of dividing the total DC voltage reference value by the number of basic converter units is the DC voltage reference value of each converter unit, so as to achieve stable control of the total DC voltage of the compact railway energy control complex, and realize the current sharing of the basic converter units through the current control loop.

[0034] Compared with the prior art, the compact railway energy control complex provided by the present invention has the following beneficial effects:

[0035] (1) The compact railway energy control complex provided by the present invention can save the two high-power industrial frequency step-down transformers of the traditional RPC and the secondary filter branch reactor placed outside the converter container, which will greatly improve the "integration" of the device and reduce the floor space.

[0036] (2) In the compact railway energy control complex provided by the present invention, the magnetic field hedging decoupling inductor of the medium frequency transformer and the filter capacitor form a filter branch, which can effectively filter out the second harmonics on the DC side of the two-phase converter.

[0037] (3) The present invention connects the α-phase and β-phase of the traction network through a multifunctional-multi-body medium frequency transformer, thereby achieving electrical isolation of the α-phase and β-phase power supply networks.

[0038] (4) The compact railway energy control complex provided by the present invention reduces the DC voltage borne by the energy storage device through a modular design. The carrier phase shift control of each converter unit with a low switching frequency can obtain a higher equivalent switching frequency of the complex, reduce the switching loss of the device, reduce the harmonic distortion rate, and improve the operating efficiency of the device.

[0039] (5) The compact railway energy control complex provided by the present invention, by introducing an energy storage and renewable energy interface, enables the device to have the ability to operate in coordination with the energy storage and renewable energy systems, which is beneficial to improving the comprehensive energy utilization rate and new energy consumption rate of the electric railway system.

[0040] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A compact railway energy control complex, characterized in that: It comprises a current conversion unit (13), two filter inductors (10), a DC bus (6), a fourth DCDC converter (17) and an energy storage unit (7); The converter unit (13) comprises a medium 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 converter unit (13) are respectively connected to the busbars of the α-phase and β-phase traction feeder lines on the secondary side of the external traction transformer (2) through a filter inductor (10); the DC output port of the converter unit (13) is connected to the DC busbar (6) in parallel, and the DC busbar (6) is connected to the energy storage unit (7) through a fourth DCDC converter (17); The first DCAC converter (4) and the first DCDC converter (14) share a voltage stabilizing capacitor (19) to form a back-to-back structure; the second DCAC converter (5) and the second DCDC converter (15) share a voltage stabilizing capacitor (19) to form a back-to-back structure; the third DCDC converter (16) is connected in parallel to a voltage stabilizing capacitor (19); and 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 control complex according to claim 1 is characterized in that: The intermediate frequency transformer (11) comprises two magnetic field hedging decoupling inductor windings and three power windings, each magnetic field hedging decoupling inductor winding being composed of two windings with a common iron core and reversely wound in series; each magnetic field hedging decoupling inductor winding of the intermediate frequency transformer (11) is respectively connected in series with a filter capacitor (9) to form a second harmonic filter branch (12) on the DC side of the converter unit, and each second harmonic filter branch (12) is respectively connected in parallel with the filter capacitors (9) of the back-to-back structure on both sides; the three power windings of the intermediate frequency transformer (11) are respectively connected to a first DCDC converter (14), a second DCDC converter (15) and a third DCDC converter (16).

3. The compact railway energy control complex according to claim 1 is characterized in that: 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).

4. The compact railway energy control complex according to claim 1 is characterized in that: The compact railway energy control complex also includes a photovoltaic unit (8) and a fifth DCDC converter; The DC bus (5) is connected to the photovoltaic unit (8) via a fifth DCDC converter (18).

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