Compact railway energy regulation and control complex and control method thereof

Abstract

The invention relates to a compact railway energy regulation and control complex and a control method thereof, the compact railway energy regulation and control complex comprises a converter unit with an intermediate frequency transformer as a core, and a magnetic field hedging decoupling inductor of the intermediate frequency transformer and a filter capacitor form a secondary harmonic filter branch on the direct current side of the converter unit. And second harmonic components at the direct current side of each current conversion unit in the single-phase current conversion system are filtered out. The compact railway energy regulation and control complex uses control methods such as double-phase displacement control and passive control, can accurately control power flow distribution of two power supply arms, realizes primary side three-phase current balance control of a traction transformer, and uses a control method based on an integral linear secondary regulator LQRI to carry out comprehensive regulation and control of energy. The voltage fluctuation of the feeder line side can be effectively inhibited, and the comprehensive energy utilization rate and the new energy consumption rate of the electric railway system are improved. Due to the existence of the intermediate frequency transformer, compared with an electric energy regulation and control device taking a traditional railway power regulator as a basic topology, the compact railway energy regulation and control complex has higher integration level.

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] With the rapid development of electrified railways in my country, power quality issues such as voltage fluctuation, negative sequence, reactive power and harmonics caused by factors such as load characteristics of electrified railways and traction power supply systems have become increasingly prominent. These problems may have adverse effects 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, in a first aspect, 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, a fifth DCDC converter, an energy storage unit and a photovoltaic unit;

[0006] The converter unit includes 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 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 respectively connected to the energy storage unit and the photovoltaic unit through the fourth DCDC converter and the fifth 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 another voltage-stabilizing capacitor to form a back-to-back structure, and the third DCDC converter is connected in parallel with another 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] In a second aspect, an embodiment of the present invention provides a control method for a compact railway energy control complex, including:

[0011] Step 1: Collecting electrical parameters of the system; wherein the electrical parameters include the secondary side voltage, secondary side current and load side current of the traction transformer, the output current of the fourth DCDC converter, the output current of the fifth DCDC converter, the voltage of the DC bus, the DC side voltage between the first DCAC converter and the first DCDC converter, and the DC side voltage between the second DCAC converter and the second DCDC converter;

[0012] Step 2: According to the collected electrical parameters, power tracking control is performed on the first DCDC converter, the second DCDC converter and the third DCDC converter by a dual phase shift control method;

[0013] Step 3: Based on the collected electrical parameters, the three-phase current on the primary side of the traction transformer and the stabilization of the DC side voltage of the converter are taken as control targets, and after the DC side voltage of each converter unit is adjusted for equalization, a modulation signal is generated through a passive control method to control the first DCAC converter and the second DCAC converter;

[0014] The first DCAC converter and the second DCAC converter in each converter unit adopt a carrier phase shift control method; the number of converter units is N, and the carrier phase offset of every two adjacent converters is set to 1 / N period.

[0015] Preferably, the control method further includes:

[0016] Step 4: Use the LQRI control strategy to control the fourth DCDC converter to keep the voltage of the DC bus stable; wherein LQRI is a linear quadratic control algorithm with integral control.

[0017] Preferably, in step 2, the power tracking control of the first DCDC converter, the second DCDC converter and the third DCDC converter is performed by a dual phase shift control method according to the collected electrical parameters, including:

[0018] The port voltages corresponding to the first DCDC converter, the second DCDC converter and the third DCDC converter are u dcLi 、u dcRi and u dc , the equivalent inductance between the ports is L 12i , L 23i , L 31i ; Use a square wave with an angular frequency of ω and a duty cycle of D for double phase shift control, and the active power P transmitted between ports 12i , P 23i , P 31i Phase shift angle The following relationship exists:

[0019]

[0020] Power transfer value P of the left port, right port and DC side port CLi , P CRi , P CCi The active power P transmitted between ports 12i , P 23i , P 31i There are the following relationships:

[0021]

[0022] By dynamically adjusting the phase shift angle and In order to achieve accurate distribution of active power at each port, control signals of the first DCDC converter, the second DCDC converter, and the third DCDC converter are generated accordingly to achieve tracking control of the active power of the three-port transformer.

[0023] Preferably, in step 3, the control target is to balance the three-phase current on the primary side of the traction transformer and stabilize the DC side voltage of the converter according to the collected electrical parameters, and after the DC side voltage of each converter unit is adjusted for equalization, a modulation signal is generated by a passive control method to control the first DCAC converter and the second DCAC converter, including:

[0024] According to the collected electrical parameters, calculate the active power P of the left and right power supply arms L and P R , DC bus side transmission power P ES , and extract the voltage amplitude u of the two power supply arms LM and u RM , where the secondary side of the traction transformer is electrically connected to the two power supply arms of the electrified railway through the α-phase and β-phase traction feeders; when the three-phase current on the primary side of the traction transformer is balanced, the active power that the two power supply arms should reach is:

[0025]

[0026] Calculate the load current i LL的 The magnitude of the reactive component i LLq and i LRq The current reactive component amplitude of the compact railway energy control complex CRER compensated to the two power supply arms has the following relationship with various parameters:

[0027]

[0028] In the formula, i crefLq and i crefRq are respectively the amplitude of the reactive component of the command current of the first DCAC converter and the amplitude of the reactive component of the command current of the second DCAC converter;

[0029] In order to maintain the DC side voltage stability, the DC voltage control is introduced to make the DC side voltage average value of each converter unit track the upper command value. The active component amplitude i of the first DCAC converter command current crefLp , the active component amplitude of the command current of the second DCAC converter i crefRp , and the DC side voltage command value u * dcL and u * dcR , and the average voltage u of each converter unit DC side dcLav 、u dcRav There is the following relationship:

[0030]

[0031] Where KP and KI are the parameters of PI control;

[0032] In step 3, after the DC side voltages of each converter unit are adjusted for voltage balancing, a modulation signal is generated by a passive control method to control the first DCAC converter and the second DCAC converter, including:

[0033] For the control of the first DCAC converter, the converter design equation based on passive control includes:

[0034]

[0035] In the formula, R L and L L is the equivalent inductance and resistance of the first DCAC converter, R N is the virtual resistance, u Lp is the amplitude of the active component of the secondary voltage of the traction transformer, i crefLp is the active component amplitude of the first DCAC converter command current, i cLp is the active component amplitude of the actual output current of the first DCAC converter, i crefLq is the reactive component amplitude of the first DCAC converter command current, i cLq is the reactive component amplitude of the actual output current of the first DCAC converter. In order to obtain the PWM signal, the above formula (6) needs to be transformed accordingly:

[0036] u Lref =[cosωt sinωt][u cLp u cLq ] T (7)

[0037] The DC side voltage u of the i-th converter unit dcLi With the voltage mean u dcLav After PI control, the fine-tuning amount is generated and added to the modulation signal reference value. The fine-tuning command current is as follows:

[0038]

[0039] In the formula, △u rdLi is the fine-tuning command current, t is the system operation time;

[0040] After voltage balancing control, the command signal u of the conversion unit i is generated Lrefi To control the first DCAC converter:

[0041] u Lrefi =u Lref +Δu Lrefi (9)

[0042] In the formula, u Lrefis the command signal to be fine-tuned for controlling the first DCAC converter of each converter unit, △u Lrefi is a fine-tuned command signal for controlling the first DCAC converter of the i-th converter unit.

[0043] For the control of the second DCAC converter, the command signal u for controlling the second DCAC converter is generated in the same way. Rrefi ; The command signal u of each conversion unit Lrefi with u Rrefi The PWM signal is converted into a PWM signal to control the first DCAC converter and the second DCAC converter.

[0044] Compared with the prior art, the compact railway energy control complex and control method thereof provided by the present invention have the following beneficial effects:

[0045] 1) The compact railway energy control complex provided by the present invention adopts modular cascade technology and magnetic field hedging decoupling inductor winding of the medium frequency transformer. While realizing two-phase electrical isolation, it can save two large-capacity industrial frequency step-down transformers of the traditional RPC and the secondary filter branch reactor placed outside the converter container, greatly improving the "integration" of the device, reducing the footprint, and reducing the high-frequency harmonics injected into the system due to modulation.

[0046] 2) The compact railway energy control complex provided by the present invention, by introducing energy storage and renewable energy interfaces, enables the device to have the ability to operate in coordination with 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, and can effectively reduce the peak electricity charges of traction substations.

[0047] 3) The control method of the compact railway energy control complex provided by the present invention can realize high power factor and low voltage imbalance operation on the high-voltage side of the traction substation, so that it meets the national standard requirements, and can effectively suppress the voltage fluctuation on the feeder side, which is beneficial to improving the transportation capacity of the railway system.

[0048] 4) The control method of the compact railway energy control complex provided by the present invention uses a passive control method to realize the control of the DCAC converter of each converter unit. By introducing a virtual resistor, the dissipation characteristics of the virtual energy system shown by the tracking error are improved, and the rapid tracking of the current command can be realized, and it is insensitive to the waveform of the given type command. The fourth DCDC converter on the energy storage side is controlled by the LQRI control strategy, which is conducive to improving the converter's tracking ability for large signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A schematic structural diagram of the compact railway energy control complex provided by the present invention.

[0050] Figure 2 A flow chart of a control method for a compact railway energy control complex provided by the present invention;

[0051] Figure 3 It is a schematic diagram of the overall control framework of the system provided by the present invention.

[0052] Figure 4 It is a schematic diagram of power transmission of the dual phase shift control method provided by the present invention.

[0053] Figure 5 It is a schematic diagram of voltage waveforms of each port in the dual phase shift control provided by the present invention.

[0054] Figure 6 It is a control block diagram of the dual phase shift control provided by the present invention.

[0055] Figure 7 It is a control block diagram of the command current reactive component signal of the first DCAC converter and the second DCAC converter provided by the present invention.

[0056] Figure 8 It is a control block diagram of the command current active component signal and the voltage-sharing fine-tuning command signal of the first DCAC converter and the second DCAC converter provided by the present invention.

[0057] Fig. 9 It is a schematic diagram of the voltage and current control effect of the primary and secondary sides of the three-phase V / v traction transformer provided by the present invention.

[0058] Fig.10 It is a control block diagram of the passive control method provided by the present invention.

[0059] Fig.11 It is a LQRI control block diagram of the fourth DCDC converter on the energy storage side provided by the present invention.

[0060] 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

[0061] The preferred embodiments of the present invention are 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.

[0062] 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.

[0063] 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.

[0064] In view of this, in order to realize the integrated energy control of "source-grid-storage-vehicle" of electrified railway, the present invention provides a compact railway energy control complex (Compacted Railway Energy Router, CRER) and its control method, using a passive control method to realize the control of the DCAC converter of each converter unit, and by introducing a virtual resistor, the dissipation characteristics of the virtual energy system shown by the tracking error are improved, and the rapid tracking of the current command can be realized, and it is insensitive to the waveform of the given type command. The following will be explained and introduced through multiple embodiments.

[0065] Figure 1 This is a 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;

[0066] 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 feeders on the secondary side of the external traction transformer 2 through a filter inductor 10. The present invention connects the α and β phases of the traction network through a multi-functional-multi-body medium frequency transformer, which can achieve electrical isolation of the α and β phase power supply networks. Among them, the traction transformer 2 can adopt a three-phase V / v traction transformer, refer to Figure 1The primary side of the traction transformer 2 is connected to the three-phase 110 kV power grid 1, the secondary side of the traction transformer is connected to the electric locomotive 3 and the converter unit 13, and the load side of the traction transformer is connected to the electric locomotive 3. Figure 1 It can be understood that the secondary side of the traction transformer refers to the side of the transformer that outputs the voltage, also known as the secondary side. The load side refers to the device that is connected to the secondary side of the transformer and actually consumes electrical energy. In this embodiment, the electric locomotive serves as the load device.

[0067] 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;

[0068] 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.

[0069] 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 of the back-to-back structure 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. In the compact railway energy control complex provided by the present invention, the magnetic field hedging decoupling inductor of the intermediate frequency transformer and the filter capacitor constitute a filter branch, which can effectively filter out the second harmonics on the DC side of the two-phase converter.

[0070] 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.

[0071] 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.

[0072] 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. 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.

[0073] In a preferred embodiment of the present invention, the working principle of the compact railway energy control complex is described in detail.

[0074] 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 3.42mF. 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 5mF. The inductance value L2 and the capacitance value C2 of the second harmonic filter branch must satisfy the relationship L2C2n 2 ω 2 =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 second harmonic filter branch has the following relationship: C2 =U dcmax +I dc2 / (2πf c C2), 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 C2 is not less than 5.53mF, so C2=6mF. According to the relationship L2C2n 2 ω 2 =1, the calculated inductance value L2 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.

[0075] 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.

[0076] Figure 2 A flow chart of a control method for a compact railway energy control complex provided by the present invention; Figure 3 This is a schematic diagram of the overall control framework of the system provided by the present invention. Figure 1 to Figure 3 , an embodiment of the present invention provides a control method for a compact railway energy control complex, the method comprising:

[0077] Step 1: Collect the electrical parameters of the system; wherein the electrical parameters include the secondary side voltage u of the traction transformer L 、u R , traction transformer secondary current i L 、i R , load side current i LL 、i LR , the output current i of the fourth DCDC converter SC , the output current i of the fifth DCDC converter NE , DC bus voltage u dc , the DC side voltage u between the first DCAC converter and the first DCDC converter dcLi , and the DC side voltage u between the second DCAC converter and the second DCDC converter dcRi ;

[0078] Step 2: According to the collected electrical parameters, power tracking control is performed on the first DCDC converter, the second DCDC converter and the third DCDC converter by a dual phase shift control method;

[0079] Step 3: Based on the collected electrical parameters, the three-phase current on the primary side of the traction transformer and the stabilization of the DC side voltage of the converter are taken as control targets, and after the DC side voltage of each converter unit is adjusted for equalization, a modulation signal is generated through a passive control method to control the first DCAC converter and the second DCAC converter;

[0080] The first DCAC converter and the second DCAC converter in each converter unit adopt a carrier phase shift control method; the number of converter units is N, and the carrier phase offset of every two adjacent converters is set to 1 / N period.

[0081] Step 4: Use the LQRI control strategy to control the fourth DCDC converter to keep the voltage of the DC bus stable; wherein LQRI is a linear quadratic control algorithm with integral control.

[0082] Figure 4 is a schematic diagram of power transmission of the dual phase shift control method provided by the present invention, Figure 5 is a schematic diagram of voltage waveforms at each port in the dual phase shift control provided by the present invention, Figure 6 It is a control block diagram of the dual phase shift control provided by the present invention. In the drawings of the specification, DC / AC1 and DC / AC2 refer to the first DCAC converter and the second DCAC converter in the present application respectively. DC / DC1, DC / DC2, DC / DC3 and DC / DC4 refer to the first DCDC converter, the second DCDC converter, the third DCDC converter and the fourth DCDC converter in the present application respectively.

[0083] In a preferred embodiment of the present invention, referring to Figure 2 , Figure 4-6 In step 2, the power tracking control of the first DCDC converter, the second DCDC converter and the third DCDC converter is performed by a dual phase shift control method according to the collected electrical parameters, specifically including:

[0084] According to the electrical parameters collected in step 1, the port voltages corresponding to the first DCDC converter, the second DCDC converter and the third DCDC converter are u dcLi 、u dcRi and u dc , refer to Figure 1 , the voltage at the left port of the first DCDC converter is u dcLi , the voltage at the right port of the second DCDC converter is u dcRi , the voltage at the DC side port of the third DCDC converter is u dcLi The equivalent inductances between the ports are L 12i , L 23i , L 31i; Double phase shift control is performed using a square wave with an angular frequency of ω and a duty cycle of D. Dual phase shift control is a control strategy used in power electronic converters, especially in DC-DC converters, inverters, etc. It optimizes converter performance by introducing phase shift angles in different parts of the converter (such as the input side and the output side). In this embodiment, the active power P transmitted between ports is 12i , P 23i , P 31i Phase shift angle The following relationship exists:

[0085]

[0086] Power transfer value P of the left port, right port and DC side port CLi , P CRi , P CCi The active power P transmitted between ports 12i , P 23i , P 31i There are the following relationships:

[0087]

[0088] In this embodiment, the duty cycle D is 0.5, the angular frequency ω of the intermediate frequency transformer is 2000π, and the phase shift angle is adjusted dynamically. and The active power of each port can be accurately distributed, and control signals of converter DC / DC1, converter DC / DC2 and converter DC / DC3 can be generated accordingly, so that tracking control of the active power of the three-port transformer can be achieved.

[0089] In a preferred embodiment of the present invention, in step 3, the control target is to balance the three-phase current on the primary side of the traction transformer and stabilize the DC side voltage of the converter according to the collected electrical parameters, and after the DC side voltage of each converter unit is adjusted for equalization, a modulation signal is generated by a passive control method to control the first DCAC converter and the second DCAC converter, including:

[0090] by Figure 1 Taking the two-arm traction system shown in the figure as an example, in order to achieve the three-phase balance of the primary current of the traction transformer, it is first necessary to collect the electrical parameters of the system and calculate the active power P of the left and right power supply arms. L and P R , DC bus side transmission power P ES , and extract the amplitude u of the voltage of the two power supply arms LM and u RM, where the secondary side of the traction transformer is electrically connected to the two power supply arms of the electrified railway through the α-phase and β-phase traction feeders; when the three-phase current on the primary side of the traction transformer is balanced, the active power that the two power supply arms should reach is:

[0091]

[0092] Figure 7 : is a control block diagram of the command current reactive component signal of the first DCAC converter and the second DCAC converter provided by the present invention. LL Take the reactive component as an example, the amplitude of the reactive component is calculated as follows: First, extract u through the phase-locked loop PLL L ωt L , we get cosωt L , and then with i LL Multiply them, pass the product through the low-pass filter LPF and multiply it by 2 to get the amplitude of the reactive component i LLq .i LRq The calculation is similar; the current reactive component amplitude compensated by the compact railway energy control complex CRER to the two power supply arms has the following relationship with each parameter:

[0093]

[0094] In the formula, i crefLq and i crefRq They are respectively the reactive component amplitude of the command current of the first DCAC converter and the reactive component amplitude of the command current of the second DCAC converter.

[0095] In order to maintain the DC side voltage stability, the DC voltage control is introduced to make the DC side voltage average value of each converter unit track the upper command value. The active component amplitude i of the first DCAC converter command current crefLp , the active component amplitude of the command current of the second DCAC converter i crefRp , and the DC side voltage command value u * dcL and u * dcR , and the average voltage u of each converter unit DC side dcLav 、u dcRav There is the following relationship:

[0096]

[0097] Where KP and KI are the parameters of PI (Proportional-Integral) control;

[0098] In step 3, after the DC side voltages of each converter unit are adjusted for voltage balancing, a modulation signal is generated by a passive control method to control the first DCAC converter and the second DCAC converter, including:

[0099] In order to achieve a fast and stable control effect, the present invention adopts a passive control strategy to control the first DCAC converter and the second DCAC converter. Fig.10 This is a control block diagram of the passive control method provided by the present invention. In order to speed up the energy dissipation of the system, a virtual damping R is introduced. N , which will significantly improve the current tracking convergence speed.

[0100] For the control of the first DCAC converter, the converter design equation based on passive control includes:

[0101]

[0102] In the formula, R L and L L is the equivalent inductance and resistance of the first DCAC converter, R N is the virtual resistance, u Lp is the amplitude of the active component of the secondary voltage of the traction transformer, i crefLp is the active component amplitude of the first DCAC converter command current, i cLp is the active component amplitude of the actual output current of the first DCAC converter, i crefLq is the reactive component amplitude of the first DCAC converter command current, i cLq is the reactive component amplitude of the actual output current of the first DCAC converter. In order to obtain the PWM signal, the above formula (6) needs to be transformed accordingly:

[0103] u Lref =[cosωt sinωt][u cLp u cLq ] T (7)

[0104] It is understandable that in actual engineering, since the parameters of each converter unit cannot be completely consistent, using the same command signal to control all converters will cause DC side voltage imbalance. In order to achieve consistent DC side voltages of each converter unit, voltage balancing control needs to be added. Specifically, the DC side voltage u of the i-th converter unit is equalized to dcLi With the voltage mean u dcLav After PI control, the fine-tuning value is added to the modulation signal reference value. Figure 8 It is a control block diagram of the command current active component signal and the voltage-sharing fine-tuning command signal of the first DCAC converter and the second DCAC converter provided by the present invention. Fig. 9This is a schematic diagram of the voltage and current control effect of the primary and secondary sides of the three-phase V / V traction transformer provided by the present invention. The fine-tuning command current is as follows:

[0105]

[0106] In the formula, △u rdLi is the fine-tuning command current, t is the system operation time;

[0107] After voltage balancing control, the command signal u of the conversion unit i is generated Lrefi To control the first DCAC converter:

[0108] u Lrefi =u Lref +Δu Lrefi (9)

[0109] In the formula, u Lref is the command signal to be fine-tuned for controlling the first DCAC converter of each converter unit, △u Lrefi is a fine-tuned command signal for controlling the first DCAC converter of the i-th converter unit.

[0110] For the control of the second DCAC converter, the command signal u for controlling the second DCAC converter is generated in the same way. Rrefi ; The command signal u of each conversion unit Lrefi with u Rrefi The first DCAC converter and the second DCAC converter are modulated by a carrier phase shift control method; the number of converter units is N, and the carrier phase offset of each two adjacent converters is set to 1 / N period.

[0111] Fig.11 This is the LQRI control block diagram of the fourth DCDC converter on the energy storage side provided by the present invention, referring to Fig.11 In a preferred embodiment of the present invention, in step 4, the fourth DCDC converter is controlled by adopting the LQRI control strategy, which can eliminate the steady-state tracking error of the traditional control method and ensure that the voltage of the DC bus 6 is stably maintained at 320V, which specifically includes:

[0112] In the face of parameter disturbances or load fluctuations, in order to solve the problem of steady-state tracking error, the LQRI (Linear Quadratic Regulator with an Integrator) control strategy is selected to design the optimal feedback control of the system, which can improve the response and accuracy of the system. Among them, the LQRI control strategy is a control strategy that combines the linear quadratic regulator (LQR) and integral control (Integrator). This strategy aims to enhance the performance of the LQR controller by introducing an integral term, especially in applications where steady-state errors need to be eliminated. In this embodiment, the output current i of the energy storage converter has been measured. SC , DC bus voltage u dc , the LQRI small signal model is:

[0113]

[0114] In the formula, Δτ e =[Δi SC Δu dc ∫Δu dc ] T ;

[0115] Among them, A e is the state matrix, B e is the control matrix, △τ e is the state variable; △u dc for u dc The increment of △i SC for i SC The increment of , the superscript T represents the transposed matrix; △ν e is the control variable.

[0116]

[0117] Where D SC is the duty cycle of the fourth DCDC converter when it outputs stably, C dc and L dc are the capacitance and inductance of the fourth DCDC converter, R e is the equivalent impedance of the fourth DCDC converter. According to the optimal control theory, the performance index is:

[0118]

[0119] In the formula, Q W is the weight matrix of the state error term, R W is the weight matrix of the control signal term.

[0120] The optimal feedback control rate when the best performance is required, △ν e Needs to be satisfied

[0121]

[0122] Among them, R W =diag[R d ];

[0123] In the formula, diag[…] is a diagonal matrix. For example, diag[ab c] is a 3x3 matrix with a, b, c as the main diagonal and all other elements of the matrix are 0.

[0124] P can be obtained by solving the following equation:

[0125]

[0126] By using MATLAB software to solve the function [K opt P e]=lqr(A e B e Q W R W ) can calculate the optimal feedback gain matrix: K opt =[k 11 k 12 k 13 ];

[0127] Among them, K opt is the optimal feedback gain matrix, k 11 , k 12 and k 13 They are the optimal feedback gain matrix K opt The three elements.

[0128] Based on the above analysis, we can get the control rate of the fourth DCDC converter controlled by LQRI as:

[0129] Δd=-k 11 Δi SC -k 12 Δu dc -k 13 ∫Δu dc (14)

[0130] Wherein, △d is the control rate of the fourth DCDC converter controlled by LQRI.

[0131] Compared with the prior art, the compact railway energy control complex and control method thereof provided by the present invention have the following beneficial effects:

[0132] 1) The compact railway energy control complex provided by the present invention adopts modular cascade technology and magnetic field hedging decoupling inductor winding of the medium frequency transformer. While realizing two-phase electrical isolation, it can save two large-capacity industrial frequency step-down transformers of the traditional RPC and the secondary filter branch reactor placed outside the converter container, greatly improving the "integration" of the device, reducing the footprint, and reducing the high-frequency harmonics injected into the system due to modulation.

[0133] 2) The compact railway energy control complex provided by the present invention, by introducing energy storage and renewable energy interfaces, enables the device to have the ability to operate in coordination with 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, and can effectively reduce the peak electricity charges of traction substations.

[0134] 3) The control method of the compact railway energy control complex provided by the present invention can realize high power factor and low voltage imbalance operation on the high-voltage side of the traction substation, so that it meets the national standard requirements, and can effectively suppress the voltage fluctuation on the feeder side, which is beneficial to improving the transportation capacity of the railway system.

[0135] 4) The control method of the compact railway energy control complex provided by the present invention uses a passive control method to realize the control of the DCAC converter of each converter unit. By introducing a virtual resistor, the dissipation characteristics of the virtual energy system shown by the tracking error are improved, and the rapid tracking of the current command can be realized, and it is insensitive to the waveform of the given type command. The fourth DCDC converter on the energy storage side is controlled by the LQRI control strategy, which is conducive to improving the converter's tracking ability for large signals.

[0136] 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.

[0137] 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 includes a current conversion unit, two filter inductors, a DC bus, a fourth DCDC converter, a fifth DCDC converter, an energy storage unit and a photovoltaic unit; The converter unit includes 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 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 respectively connected to the energy storage unit and the photovoltaic unit through the fourth DCDC converter and the fifth DCDC converter; 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 another voltage-stabilizing capacitor to form a back-to-back structure, and the third DCDC converter is connected in parallel with another 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.

2. The compact railway energy control complex according to claim 1 is characterized in that: The intermediate frequency transformer 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 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 the back-to-back structure 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.

3. The compact railway energy control complex according to claim 1 is characterized in that: The two AC ports of the converter unit are connected to the first DCAC converter and the second DCAC converter respectively; the DC output port of the converter unit is connected to the third DCDC converter.

4. The control method of the compact railway energy control complex according to any one of claims 1 to 3, characterized in that: include: Step 1: Collecting electrical parameters of the system; wherein the electrical parameters include the secondary side voltage, secondary side current and load side current of the traction transformer, the output current of the fourth DCDC converter, the output current of the fifth DCDC converter, the voltage of the DC bus, the DC side voltage between the first DCAC converter and the first DCDC converter, and the DC side voltage between the second DCAC converter and the second DCDC converter; Step 2: According to the collected electrical parameters, power tracking control is performed on the first DCDC converter, the second DCDC converter and the third DCDC converter by a dual phase shift control method; Step 3: Based on the collected electrical parameters, the three-phase current on the primary side of the traction transformer and the stabilization of the DC side voltage of the converter are taken as control targets, and after the DC side voltage of each converter unit is adjusted for equalization, a modulation signal is generated through a passive control method to control the first DCAC converter and the second DCAC converter; The first DCAC converter and the second DCAC converter in each converter unit (13) adopt a carrier phase shift control method; the number of converter units (13) is N, and the carrier phase offset of every two adjacent converters is set to 1 / N period.

5. The control method of the compact railway energy control complex according to claim 4 is characterized in that: Also includes: Step 4: Use the LQRI control strategy to control the fourth DCDC converter to keep the voltage of the DC bus stable; wherein LQRI is a linear quadratic control algorithm with integral control.

6. The control method of the compact railway energy control complex according to claim 4, characterized in that: In step 2, the power tracking control of the first DCDC converter, the second DCDC converter and the third DCDC converter is performed by a dual phase shift control method according to the collected electrical parameters, including: The port voltages corresponding to the first DCDC converter, the second DCDC converter and the third DCDC converter are u dcLi 、u dcRi and u dc , the equivalent inductance between the ports is L 12i , L 23i , L 31i ; Use a square wave with an angular frequency of ω and a duty cycle of D for double phase shift control, and the active power P transmitted between ports 12i , P 23i , P 31i Phase shift angle The following relationship exists: Power transfer value P of the left port, right port and DC side port CLi , P CRi , P CCi The active power P transmitted between ports 12i , P 23i , P 31i There are the following relationships: By dynamically adjusting the phase shift angle and In order to achieve accurate distribution of active power at each port, control signals of converter DC / DC1, converter DC / DC2 and converter DC / DC3 are generated accordingly to achieve tracking control of active power of the three-port transformer.

7. The control method of the compact railway energy control complex according to claim 4 is characterized in that: In step 3, according to the collected electrical parameters, the three-phase current on the primary side of the traction transformer and the stabilizing DC side voltage of the converter are taken as control targets, and after the DC side voltage of each converter unit is adjusted for voltage balancing, a modulation signal is generated by a passive control method to control the first DCAC converter and the second DCAC converter, including: According to the collected electrical parameters, calculate the active power P of the left and right power supply arms L and P R , DC bus side transmission power P ES , and extract the amplitude u of the voltage of the two power supply arms LM and u RM , where the secondary side of the traction transformer is electrically connected to the two power supply arms of the electrified railway through the α-phase and β-phase traction feeders; when the three-phase current on the primary side of the traction transformer is balanced, the following relationship is obtained: Where P' L For P' R To achieve the three-phase balance of the primary current of the traction transformer, the left and right power supply arms should reach the active power; Calculate the load current i LL The magnitude of the reactive component i LLq and i LRq The current reactive component amplitude of the compact railway energy control complex CRER compensated to the two power supply arms has the following relationship with various parameters: In the formula, i crefLq and i crefRq are respectively the amplitude of the reactive component of the command current of the first DCAC converter and the amplitude of the reactive component of the command current of the second DCAC converter; In order to maintain the DC side voltage stability, the DC voltage control is introduced to make the DC side voltage average value of each converter unit track the upper command value. The active component amplitude i of the first DCAC converter command current crefLp , the active component amplitude of the command current of the second DCAC converter i crefRp , and the DC side voltage command value u * dcL and u * dcR , and the average voltage u of each converter unit DC side dcLav 、u dcRav There is the following relationship: In the formula, K P and K I is the parameter of PI control; In step 3, after the DC side voltages of each converter unit are adjusted for voltage balancing, a modulation signal is generated by a passive control method to control the first DCAC converter and the second DCAC converter, including: For the control of the first DCAC converter, the converter design equation based on passive control includes: In the formula, R L and L L is the equivalent inductance and resistance of the first DCAC converter, R N is the virtual resistance, u Lp is the amplitude of the active component of the secondary voltage of the traction transformer, i crefLp is the active component amplitude of the first DCAC converter command current, i cLp is the active component amplitude of the actual output current of the first DCAC converter, i crefLq is the reactive component amplitude of the first DCAC converter command current, i cLq is the reactive component amplitude of the actual output current of the first DCAC converter. In order to obtain the PWM signal, the above formula (6) needs to be transformed accordingly: u Lref =[cosωt sinωt][u cLp u cLq ] T (7) The DC side voltage u of the i-th converter unit dcLi With the voltage mean u dcLav After PI control, the fine-tuning amount is generated and added to the modulation signal reference value, and the following relationship is obtained: In the formula, △u rdLi is the fine-tuning command current, t is the system operation time; After voltage balancing control, the command signal u of the conversion unit i is generated Lrefi To control the first DCAC converter: u Lrefi =u Lref +Δu Lrefi (9) In the formula, u Lref is the command signal to be fine-tuned for controlling the first DCAC converter of each converter unit, △u Lrefi is a fine-tuned command signal for controlling the first DCAC converter of the i-th converter unit; For the control of the second DCAC converter, the command signal u for controlling the second DCAC converter is generated in the same way. Rrefi ; The command signal u of each conversion unit Lrefi with u Rrefi The PWM signal is converted into a PWM signal to control the first DCAC converter and the second DCAC converter.

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