A compact railway energy conditioning complex and method of controlling the same

Abstract

The present application relates to a kind of compact railway energy regulation complex and its control method, including the converter unit with the core of medium-frequency transformer, the magnetic field of medium-frequency transformer is to the decoupling inductance of collision and filter capacitor and is constituted the second harmonic filter branch of converter unit DC side, filter each converter unit DC side in single-phase conversion system The second harmonic component is removed.Compact railway energy regulation complex uses double-phase shift control and passive control etc.Control method, can accurately control the power flow distribution of two power supply arms and realize traction transformer primary side three-phase current balance control, and using the linear quadratic regulator LQRI control method based on band integration is carried out energy comprehensive regulation, can effectively suppress the voltage fluctuation of feeder side, improve the comprehensive energy utilization rate and new energy consumption rate of electric railway system.Because of the existence of medium-frequency transformer, compared with the electric energy regulation device with the basic topology of traditional railway power regulator, compact railway energy regulation complex has higher integration.

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] With the rapid development of electrified railways in China, the problems of voltage fluctuation, negative sequence, reactive power and harmonic caused by the load characteristics of electrified railways, traction power supply system and other factors 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] The existing railway energy control equipment, such as railway power conditioner (RPC) and RPC based on modular multilevel converter (MMC), can only deal with power quality problems and 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 in the DC side. The filter inductance used to filter the second harmonic is large in volume and cannot be placed in the converter container, so 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, in a first aspect, the embodiments of the present application provide a compact railway energy control complex, comprising a conversion 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 conversion 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. Two AC ports of the conversion unit are connected to the bus of the traction feeder lines of the α and β phases of the secondary side of the external traction transformer through one filter inductor respectively. The DC output port of the conversion unit is connected to the DC bus in a parallel manner, and the DC bus is connected to the energy storage unit and the photovoltaic unit through the fourth DCDC converter and the fifth DCDC converter respectively.

[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 another voltage stabilizing capacitor to form a back-to-back structure, and the third DCDC converter is connected in parallel with still another 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] In a second aspect, the embodiments of the present application provide a control method of the compact railway energy regulation complex, comprising:

[0011] Step 1: collecting electrical parameters of the system; wherein the electrical parameters include the secondary side voltage, the secondary side current and the 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 of the first DCAC converter and the first DCDC converter, and the DC side voltage of the second DCAC converter and the second DCDC converter;

[0012] Step 2: according to the collected electrical parameters, performing power tracking control on the first DCDC converter, the second DCDC converter and the third DCDC converter by a double phase-shift control method;

[0013] Step 3: according to the collected electrical parameters, taking balancing the three-phase current on the primary side of the traction transformer and stabilizing the DC side voltage of the converter as the control target, and after adjusting the DC side voltage of each conversion unit to be balanced, generating a modulation signal by 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 of the variable current units adopt a carrier phase shift control method; the number of the variable current units is N, and the carrier phase shift of each two adjacent variable current units is set to 1 / N of a period.

[0015] Preferably, the control method further comprises:

[0016] Step 4: controlling the fourth DCDC converter by using an LQRI control strategy 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 according to the collected electrical parameters by using the double phase shift control method comprises:

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

[0019]

[0020] The power transfer values P CLi , P CRi , P CCi of the left port, the right port and the DC side port have the following relationship with the active power P 12i , P 23i , P 31i transferred between the ports:

[0021]

[0022] The phase shift angles and are dynamically adjusted to realize accurate allocation of the active power of each port, and the control signals of the first DCDC converter, the second DCDC converter and the third DCDC converter are generated accordingly to realize tracking control of the active power of the three-port transformer.

[0023] Preferably, in step 3, the balance of the three-phase current of the primary side of the traction transformer and the stability of the DC voltage of the converter are taken as the control targets according to the collected electrical parameters, and the DC voltage of each converter unit is adjusted to be uniform, and then a modulation signal is generated by a passive control method to control the first DCAC converter and the second DCAC converter, comprising:

[0024] According to the collected electrical parameters, the active power P of the left and right power supply arms is calculated L and P R , the transmission power P ES of the DC bus side, and the amplitudes u LM and u RM of the voltages of the two power supply arms are extracted, wherein the secondary side of the traction transformer is electrically connected to the two power supply arms through the alpha phase and beta phase traction feeders; when the three-phase current of the primary side of the traction transformer is balanced, the active power of the two power supply arms should reach:

[0025]

[0026] The amplitudes i LL的 , i LLq and i LRq of the reactive components of the load current are calculated; the amplitudes of the reactive components of the current compensated by the CRER to the two power supply arms have the following relationships with the parameters:

[0027]

[0028] wherein i crefLq and i crefRq are the amplitudes of the command current reactive components of the first DCAC converter and the second DCAC converter respectively;

[0029] In order to maintain the stability of the DC side voltage, the control of the DC voltage is introduced, so that the average value of the DC side voltage of each converter unit tracks the command value; the amplitudes i crefLp of the active components of the command current of the first DCAC converter, the amplitudes i crefRp of the active components of the command current of the second DCAC converter, and the command value u * of the DC side voltage have the following relationships: dcL and u * dcR , and the average values u dcLav and u dcRav of the DC side voltages of the converter units have the following relationships:

[0030]

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

[0032] In step 3, after the DC side voltage of each converter unit is adjusted, 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 formula based on passive control includes:

[0034]

[0035] In the formula, R L and L L are the equivalent inductance and resistance of the first DCAC converter, R N is a virtual resistance, u Lp is the active component amplitude of the secondary side voltage of the traction transformer, i crefLp is the active component amplitude of the command current of the first DCAC converter, i cLp is the active component amplitude of the actual output current of the first DCAC converter, and i crefLq is the reactive component amplitude of the command current of the first DCAC converter, 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 dcLi of the i-th converter unit is subtracted from the voltage average u dcLav , and after PI control, a fine adjustment amount is generated and added to the modulation signal reference value. The fine command current is as follows:

[0038]

[0039] In the formula, △u rdLi is the fine command current, and t is the system running time.

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

[0041] u Lrefi = u Lref +△u Lrefi (9)

[0042] In the formula, u Lrefu Lrefi u

[0043] u Rrefi i Lrefi i Rrefi u

[0044] The compact railway energy regulation complex provided by the present application has the following beneficial effects compared with the prior art:

[0045] 1) The compact railway energy regulation complex provided by the present application adopts modular cascade technology and a magnetic field opposing decoupling inductor winding of a medium-frequency transformer, thereby achieving two-phase electrical isolation, eliminating two large-capacity power-frequency step-down transformers of a traditional RPC and a secondary filter branch reactor outside the converter container, greatly improving the integration of the device, reducing the occupied area, and reducing high-frequency harmonics injected by the modulation system.

[0046] 2) The compact railway energy regulation complex provided by the present application has the ability to cooperate with energy storage and renewable energy systems by introducing an energy storage and renewable energy interface, which is beneficial to improving the comprehensive energy utilization rate and new energy consumption rate of the electric railway system and effectively reducing the peak electricity cost of the traction substation.

[0047] 3) The control method of the compact railway energy regulation complex provided by the present application can realize high-power factor and low-voltage imbalance operation on the high-voltage side of the traction substation, meet the requirements of the national standard, effectively suppress the fluctuation of the voltage on the feeder side, and be beneficial to improving the carrying capacity of the railway system.

[0048] 4) The control method of the compact railway energy regulation complex provided by the present application uses a passive control method to control the DCAC converter of each conversion unit, improves the dissipation characteristics of the virtual energy system represented by the tracking error by introducing a virtual resistance, realizes fast tracking of the current command, and is not sensitive to the waveform of the given command. The LQRI control strategy is used to control the fourth DCDC converter on the energy storage side, which is beneficial to improving the tracking ability of the converter to large signals. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 The compact railway energy regulation complex provided by the present application has the following beneficial effects compared with the prior art:

[0050] Figure 2 The control method flow chart of the compact railway energy regulation complex provided by the present application is shown in the figure.

[0051] Figure 3 The system overall control framework schematic diagram provided by the present application is shown in the figure.

[0052] Figure 4 The power transmission schematic diagram of the double phase-shifting control method provided by the present application is shown in the figure.

[0053] Figure 5 The port voltage waveform schematic diagram in the double phase-shifting control provided by the present application is shown in the figure.

[0054] Figure 6 The control block diagram of the double phase-shifting control provided by the present application is shown in the figure.

[0055] Figure 7 The instruction current reactive component signal control block diagram of the first DCAC converter and the second DCAC converter provided by the present application is shown in the figure.

[0056] Figure 8 The instruction current active component signal and voltage equalization fine-tuning instruction signal control block diagram of the first DCAC converter and the second DCAC converter provided by the present application is shown in the figure.

[0057] Figure 9 The primary and secondary side voltage and current control effect schematic diagram of the three-phase V / v traction transformer provided by the present application is shown in the figure.

[0058] Figure 10 The control block diagram of the passive control method provided by the present application is shown in the figure.

[0059] Figure 11 The LQRI control block diagram of the fourth DCDC converter on the energy storage side provided by the present application is shown in the figure.

[0060] 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 DC 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 conversion 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

[0061] The preferred embodiments of the present 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 present application, but are not used to limit the scope of the present application.

[0062] Reference to an "embodiment" in this document 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 various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. As will be apparent to those of ordinary skill in the art, embodiments described herein can be combined with other embodiments.

[0063] The existing railway energy regulation device, such as a railway power regulator and an RPC based on a modular multi-level converter, 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 DC side. A large volume of filter inductors is used to filter out the second harmonic, which cannot be put into the converter container, and the overall integration of the device is not high.

[0064] Therefore, in order to realize the "source-grid-storage-train" energy integrated regulation of electrified railway, the application provides a compact railway energy regulation complex (CRER) and a control method thereof. A passive control method is used to control the DCAC converter of each conversion unit. By introducing a virtual resistance, the dissipation characteristics of the virtual energy system represented by the tracking error are improved, the current command can be quickly tracked, and the waveform of the given type command is not sensitive. The following will be described and introduced through multiple embodiments.

[0065] Figure 1 The structure diagram of the compact railway energy regulation complex provided by the application is shown in the figure. As shown in the figure, Figure 1 The compact railway energy regulation complex 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.

[0066] 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 alpha and beta phase traction feeder of the secondary side of the external traction transformer 2 through one filter inductor 10. The application connects the alpha and beta phases of the traction network through the multifunctional multi-subject intermediate frequency transformer, which can realize the electrical isolation of the alpha and beta power supply networks. Among them, the traction transformer 2 can adopt a three-phase V / v traction transformer, and the connection mode is shown in the figure. Figure 1, the primary side of the traction transformer 2 is connected to the three-phase 110kV power grid 1, the secondary side of the traction transformer is connected to the electric locomotive 3 and the converter unit 13 respectively, and the load side of the traction transformer is connected to the electric locomotive 3. Referring to Figure 1 It can be understood that the secondary side of the traction transformer refers to the side of the output voltage in the transformer, also known as the secondary side or the secondary side. The load side refers to the device connected to the secondary side of the transformer and actually consuming electric energy. In the 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 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;

[0068] 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. Referring to Figure 1 The two AC ports of the converter unit 13 are connected to the first DCAC converter 4 and the second DCAC converter 5 respectively; and the DC output port of the converter unit 13 is connected to the third DCDC converter 16.

[0069] The medium-frequency transformer 11 includes two magnetic field counter-attack decoupling inductance windings and three power windings, each magnetic field counter-attack decoupling inductance winding is composed of two common-iron-core counter-wound winding strings in series; each magnetic field counter-attack decoupling inductance winding of the medium-frequency transformer 11 is connected to one filter capacitor 9 in series to form a second harmonic filter branch 12 on the DC side of the converter unit, each second harmonic filter branch 12 is connected to the filter capacitors 9 on both sides of the back-to-back structure in parallel; the three power windings of the medium-frequency transformer 11 are connected to the first DCDC converter 14, the second DCDC converter 15 and the third DCDC converter 16 respectively. The compact railway energy regulation complex provided by the application can effectively filter out the second harmonic on the DC side of the two-phase converter by forming a filter branch with the magnetic field counter-attack decoupling inductance of the medium-frequency transformer and the filter capacitor.

[0070] Specifically, the application discloses a compact railway energy regulation complex. The compact railway energy regulation complex is composed of a plurality of conversion units 13. The AC ports of each conversion unit are connected to the bus of the traction feeder line of the secondary side alpha and beta phase of the traction transformer 2 in a series mode, the DC output ports of the conversion unit 13 are connected to the DC bus in a parallel mode, and the DC bus is connected to 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 of the intermediate frequency transformer is connected to the decoupling inductance and the filter capacitor to form the second harmonic filter branch on the DC side of the conversion unit, and the second harmonic component on the DC side of each conversion unit in the single-phase conversion system is filtered out. The power winding of the intermediate frequency transformer is connected to the DC / DC converter inside each conversion unit. The compact railway energy regulation complex CRER can accurately control the power flow distribution of two power supply arms, and can comprehensively regulate the energy through the DC port and the external energy storage and new energy generation system, can effectively suppress the voltage fluctuation of the feeder line side, can improve the comprehensive energy utilization rate and the new energy consumption rate of the electric railway system, can compensate the power factor of 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 multifunctional and multi-subject intermediate frequency transformer.

[0071] As can be seen from the above embodiment, the compact railway energy regulation complex is a highly integrated railway system energy management device, and aims to realize the energy integrated regulation of the electrified railway "source-network-storage-car". The compact railway energy regulation complex can improve the energy efficiency, stability and reliability of the electrified railway.

[0072] The compact railway energy regulation complex provided by the application can reduce the DC voltage borne by the energy storage device through the modular design, can obtain a higher equivalent switching frequency of the complex through the carrier phase shift control of each conversion unit with a low switching frequency, can reduce the switching loss of the device, can reduce the harmonic distortion rate, and can improve the operation efficiency of the device.

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

[0074] 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 is taken as 3200V. Considering a 5% voltage fluctuation on the DC side, when SPWM modulation is used and the modulation ratio is taken as 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 comprehensively considering, the number N of the basic converter units 13 is taken as 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 taken as 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 taken as 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 taken as 0.1, the transformation ratio is taken as 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 taken as 1, ω is the system angular frequency taken as 2π×50, U dc is the DC voltage taken as 3200V, and C d is calculated to be 3.42 mF. Considering that taking a larger value can achieve better voltage stabilization effect, the values of the three voltage stabilizing capacitors 19 in the embodiment are all taken as 5 mF. The inductance value L2 and the capacitance value C2 of the secondary harmonic filter branch need to satisfy the relationship L2C2n 2 ω 2 =1, where n is the harmonic number to be filtered taken as 2, and ω is the system angular frequency taken as 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 taken as 2×50Hz, and the calculated filter capacitance 9 capacitance value C2 is not less than 5.53 mF, and C2=6 mF can be taken. According to the relationship L2C2n 2 ω 2 =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.

[0075] In this system, the first DC-DC converter 14 and the second DC-DC converter 15 receive active power control commands from the power distribution layer, while the fourth DC-DC converter 17 and the fifth DC-DC converter 18 receive "storage" and "source" control commands calculated from GOB. The first DC-DC converter 4, the second DC-DC converter 5, and the third DC-DC converter 16 of the compact railway energy control complex are given control commands to maintain the stability of the DC-side voltage as the control objective (outer control loop). The inner control loops of the first DC-DC converter 4, the second DC-DC converter 5, the fourth DC-DC converter 17, and the fifth DC-DC converter 18 are used as subordinate control units, and current tracking is achieved using the output of their respective outer control loops as the parameter current, thus shortening the adjustment time of each control objective. The PI controller divides the total DC voltage reference value by the number of basic converter units to obtain the DC voltage reference value for each converter unit, achieving stable control of the total DC voltage of the compact railway energy control complex. Current sharing among the basic converter units is achieved through the current control loop.

[0076] Figure 2 A flowchart of the control method for the compact railway energy regulation complex provided by the present invention; Figure 3 This is a schematic diagram of the overall system control framework provided by the present invention. (Refer to...) Figures 1-3 This invention provides a control method for a compact railway energy regulation complex, the method comprising:

[0077] Step 1: Collect the electrical parameters of the system; wherein, the electrical parameters include the secondary 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 DC-DC converter SC The output current i of the fifth DC-DC converter NE DC bus voltage u dc The DC-side voltage u of the first DCAC converter and the first DC-DC converter dcLi And the DC-side voltage u of the second DCAC converter and the second DC-DC converter dcRi ;

[0078] Step 2: Based on the collected electrical parameters, power point tracking control is performed on the first DC-DC converter, the second DC-DC converter, and the third DC-DC converter using a dual phase-shift control method;

[0079] Step 3: According to the collected electrical parameters, the balanced three-phase current of the primary side of the traction transformer and the stable voltage of the DC side of the converter are taken as the control targets, and the DC side voltage of each converter unit is adjusted to balance, and then the modulation signal is generated by the passive control method to control the first DCAC converter and the second DCAC converter;

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

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

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

[0083] In one preferred embodiment of the application, with reference to Figure 2 , Figures 4-6 , in step 2, the first DCDC converter, the second DCDC converter and the third DCDC converter are controlled by the double 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 respectively u dcLi , u dcRi and u dc , with reference to Figure 1 , the voltage of the left port corresponding to the first DCDC converter is u dcLi , the voltage of the right port corresponding to the second DCDC converter is u dcRi , and the voltage of the DC side port corresponding to the third DCDC converter is u dcLi . The equivalent inductance between the ports is L 12i , L 23i , L 31i; using a square wave with angular frequency ω and duty ratio D for double phase-shift control. Among them, double phase-shift control is a control strategy applied in power electronic converters, especially in DC-DC converters, inverters and other occasions. It realizes the optimization of the performance of the converter 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 12i , P 23i , P 31i between the phase shift angle

[0085]

[0086] The power transfer values P CLi , P CRi , P CCi of the left side port, the right side port and the DC side port have the following relationship with the active power P 12i , P 23i , P 31i

[0087]

[0088] In this embodiment, the duty ratio D is 0.5, and the intermediate frequency transformer angular frequency ω is 2000π. By dynamically adjusting the phase shift angles and , the accurate allocation of the active power of each port can be realized, and the control signals of the converter DC / DC1, the converter DC / DC2 and the converter DC / DC3 can be generated accordingly, so as to realize the tracking control of the active power of the three-port transformer.

[0089] In a preferred embodiment of the present application, in step 3, according to the collected electrical parameters, the three-phase current balance of the primary side of the traction transformer and the stable voltage of the DC side of the converter are taken as the control targets, and the DC side voltage of each variable unit is adjusted to balance, then the modulation signal is generated by the passive control method to control the first DCAC converter and the second DCAC converter, comprising:

[0090] Taking the two-arm traction system shown in Figure 1 as an example, in order to realize the three-phase current balance of the primary side of the traction transformer, the electrical parameters of the system need to be collected first, the active power P L and P R of the left and right power supply arms, the transmission power P ES of the DC bus side, and the amplitude u LM and u RM of the voltage of the two power supply arms are extracted.​Wherein, the secondary side of the traction transformer is electrically connected with two power supply arms of the electrified railway through the alpha phase and the beta phase traction feeder; when the three-phase current of the primary side of the traction transformer is balanced, the active power reached by the two power supply arms is:

[0091]

[0092] Figure 7 The figure is a control block diagram of the reactive component signal of the first DCAC converter and the second DCAC converter provided by the application. LL For example, the amplitude of the reactive component of i L is calculated as follows: first, the ωt L of u L is extracted through a phase-locked loop (PLL) to obtain cosωt LL , then i LL is multiplied by cosωt LL , and the product is processed through a low-pass filter (LPF) and multiplied by 2 to obtain the amplitude i LLq of the reactive component. LRq The calculation of i LRq is the same; the amplitude of the current reactive component compensated by the compact railway energy regulation complex (CRER) to the two power supply arms has the following relationship with the parameters:

[0093]

[0094] In the formula, i crefLq and i crefRq are 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, respectively.

[0095] To maintain the stability of the DC side voltage, the control of the DC voltage is introduced to make the average value of the DC side voltage of each converter unit track the command value; the amplitudes i crefLp of the active component of the command current of the first DCAC converter and i crefRp of the active component of the command current of the second DCAC converter have the following relationship with the command value u * dcL and u * dcR , and the average values u dcLav and u dcRav of the DC side voltage of each converter unit have the following relationship:

[0096]

[0097] In the formula, KP and KI are the parameters of PI (Proportional-Integral) control.

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

[0099] To achieve fast and stable control effect, the passive control strategy is used to control the first DCAC converter and the second DCAC converter. Figure 10 The control block diagram of the passive control method provided by the application is shown in Fig. 1, in order to accelerate the energy dissipation of the system, a virtual damping R N is introduced, which will significantly improve the tracking convergence speed of the current.

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

[0101]

[0102] In the formula, R L and L L are the equivalent inductance and resistance of the first DCAC converter, R N is a virtual resistance, u Lp is the active component amplitude of the secondary side 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 can be understood that in actual engineering, due to the fact that the parameters of each converter unit cannot be completely consistent, using the same command signal to control all converters will cause the imbalance of the DC side voltage. In order to realize the consistency of the DC side voltage of each converter unit, voltage balancing control needs to be added, specifically, the DC side voltage u dcLi of the i-th converter unit is subtracted from the voltage average u dcLav , after PI control, a fine tuning amount is added to the modulation signal reference value, Figure 8 The control block diagram of the active component signal of the command current of the first DCAC converter and the second DCAC converter provided by the application is shown in Fig. 2, Figure 9is a schematic diagram of voltage and current control effect of a three-phase V / v traction transformer provided by the present application. The fine tuning instruction current is as follows:

[0105]

[0106] In the formula, △u rdLi is the fine tuning instruction current, and t is the system running time.

[0107] After the voltage balancing control, the instruction signal u Lrefi is generated for the current conversion unit i

[0108] u Lrefi = u Lref + △u Lrefi (9)

[0109] In the formula, u Lref is the instruction signal for controlling the first DCAC converter of each current conversion unit to be fine tuned, and △u Lrefi is the instruction signal for controlling the first DCAC converter of the i-th current conversion unit after fine tuning.

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

[0111] Figure 11 is an LQRI control block diagram of the fourth DCDC converter on the energy storage side provided by the present application, with reference to Figure 11 In one preferred embodiment of the present application, in step 4, the fourth DCDC converter is controlled by using 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, and specifically includes:

[0112] In the face of parameter perturbation or load fluctuation, 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 combining linear quadratic regulator (LQR) and integrator control (Integrator). This strategy aims to enhance the performance of the LQR controller by introducing an integral term, especially in applications that require the elimination of steady-state error. In this embodiment, the output current i SC , the 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] Where A e is the state matrix, B e is the control matrix, △τ e is the state variable; △u dc is the increment of u dc , △i SC is the increment of i SC , the superscript T represents the transpose matrix; △ν e is the control variable.

[0116]

[0117] In the formula, D SC is the duty ratio when the fourth DCDC converter is stable output, 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 state error term, R W is the weight matrix of control signal term.

[0120] The optimal feedback control rate △ν e needs to meet

[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 the numbers a, b, and c as the main diagonal and all other elements of the matrix being 0.

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

[0125]

[0126] Solve the function [K] using MATLAB software. opt P e]=lqr(A e B e Q W R W The optimal feedback gain matrix can be calculated: K opt =[k 11 k 12 k 13 ];

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

[0128] Based on the above analysis, we can obtain the control rate of the fourth DC-DC converter controlled by LQRI as follows:

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

[0130] In the formula, Δd is the control law of the fourth DC-DC converter controlled by LQRI.

[0131] The compact railway energy regulation complex and its control method provided by this invention have the following advantages compared with the prior art:

[0132] 1) The compact railway energy regulation complex provided by this invention adopts modular cascade technology and magnetic field counter-coupling inductor winding of intermediate frequency transformer. While achieving two-phase electrical isolation, it can eliminate the need for two large-capacity power frequency step-down transformers and secondary filter branch reactors placed outside the converter container of traditional RPC, which greatly improves the "integration" of the device, reduces the footprint, and reduces high-frequency harmonics caused by modulation injection system.

[0133] 2) The compact railway energy regulation complex provided by the present invention introduces energy storage and renewable energy interfaces, enabling the device to operate in coordination with energy storage and renewable energy systems. This is beneficial to improving the overall energy utilization rate and new energy absorption rate of the electric railway system, and can effectively reduce the peak electricity cost of traction substations.

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

[0135] 4) The control method for the compact railway energy regulation complex provided by this invention uses a passive control method to control the DCAC converters of each converter unit. By introducing virtual resistance, the dissipation characteristics of the virtual energy system exhibited by the tracking error are improved, enabling rapid tracking of current commands and making it insensitive to the waveform of given commands. Using the LQRI control strategy to control the fourth DC-DC converter on the energy storage side is beneficial to improving the converter's tracking capability for large signals.

[0136] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A compact railway energy conditioning complex, characterized in that, 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; two AC ports of the converter unit are connected to the bus of the traction feeder line of the secondary side alpha and beta phases of the external traction transformer through a filter inductor respectively; the DC output port of the converter unit is connected to the DC bus in parallel, and the DC bus is connected to the energy storage unit and the photovoltaic unit through the fourth DCDC converter and the fifth DCDC converter respectively. 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 another voltage stabilizing capacitor to form a back-to-back structure, and the third DCDC converter is connected to another voltage stabilizing capacitor in parallel; the three power windings of the medium-frequency transformer are connected to the first DCDC converter, the second DCDC converter and the third DCDC converter respectively; the medium-frequency transformer comprises two magnetic field collision decoupling inductor windings and three power windings, each magnetic field collision decoupling inductor winding is composed of two co-iron core counter-wound windings in series; each magnetic field collision decoupling inductor winding of the medium-frequency transformer is connected to a filter capacitor in series to form a second harmonic filter branch on the DC side of the converter unit, and each second harmonic filter branch is connected to the voltage stabilizing capacitors of the back-to-back structures on both sides in parallel; the three power windings of the medium-frequency transformer are connected to the first DCDC converter, the second DCDC converter and the third DCDC converter respectively. 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.

2. The compact railway energy conditioning complex of claim 1, wherein, The method comprises the following steps:

3. The control method of the compact railway energy conditioning complex according to any one of claims 1-2, characterized in that, Step 1: collecting electrical parameters of the system; wherein the electrical parameters comprise the secondary side voltage, the secondary side current and the 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 of the first DCAC converter and the first DCDC converter, and the DC side voltage of the second DCAC converter and the second DCDC converter; Step 2: performing power tracking control on the first DCDC converter, the second DCDC converter and the third DCDC converter through a double-phase-shift control method according to the collected electrical parameters; Step 3: generating a modulation signal through a passive control method to control the first DCAC converter and the second DCAC converter after balancing the three-phase current on the primary side of the traction transformer and stabilizing the DC side voltage of the converter and adjusting the DC side voltage of each converter unit according to the collected electrical parameters. ​ The first DCAC converter and the second DCAC converter in each of the variable current units (13) adopt a carrier phase shift control method; the number of the variable current units (13) is N, and the carrier phase shift of every two adjacent variable current units is set to 1 / N of a period.

4. The control method of the compact railway energy conditioning complex of claim 3, wherein, Also comprising: Step 4: controlling the fourth DCDC converter by using an LQRI control strategy to keep the voltage of the DC bus stable; wherein LQRI is a linear quadratic control algorithm with integral control.

5. The control method of the compact railway energy conditioning complex of claim 3, wherein, In step 2, the first DCDC converter, the second DCDC converter and the third DCDC converter are controlled by using a double phase shift control method according to the collected electrical parameters, and the double phase shift control method comprises: The port voltages corresponding to the first DCDC converter, the second DCDC converter and the third DCDC converter are respectively u dcLi , u dcRi and u dc , the equivalent inductances between the ports are respectively L 12i , L 23i and L 31i ; using a square wave with an angular frequency of ω and a duty ratio of D for double phase-shift control, the active power P 12i , P 23i and P 31i transmitted between the ports and the phase-shift angle exist the following relationships: The power transfer values P of the left port, the right port and the DC side port CLi , P CRi , P CCi The active power P transmitted between the ports 12i , P 23i , P 31i have the following relationships: By dynamically adjusting the phase shift angle And To achieve accurate allocation of active power of each port, and accordingly generate control signals of the converter DC / DC1, the converter DC / DC2, and the converter DC / DC3, to realize tracking control of active power of the three-port transformer.

6. The control method of the compact railway energy conditioning complex of claim 3, wherein, In step 3, the modulation signal is generated by using a passive control method to control the first DCAC converter and the second DCAC converter after balancing the three-phase current of the primary side of the traction transformer and stabilizing the DC voltage of the variable current unit and adjusting the DC voltage of each variable current unit, and the passive control method comprises: Based on 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 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 of the primary side of the traction transformer is balanced, the following relationship holds: In the formula, P' is the active power of the left power supply arm, P" is the active power of the right power supply arm, and P is the active power of the traction transformer. L In the formula, P' is the active power of the left power supply arm, P" is the active power of the right power supply arm, and P is the active power of the traction transformer. R In order to achieve three-phase balance of the traction transformer primary The magnitude of the reactive component of the load current i LL The magnitude of the reactive component of the load current i LLq The magnitude of the reactive component of the load current i LRq The magnitude of the reactive component of the current compensated by the compact railway energy regulation complex CRER to both power supply arms has the following relationship with the parameters: where i crefLq and i crefRq are the first DC AC converter's command current reactive component magnitude and the second DC AC converter's command current reactive component magnitude, respectively; To maintain the stability of the DC side voltage, the control of the DC voltage is introduced, so that the average value of the DC side voltage of each converter unit tracks the command value, the active component amplitude i crefLp of the command current of the first DCAC converter crefRp , the active component amplitude i * of the command current of the second DCAC converter dcL , and the average value of the DC side voltage of each converter unit u * , u dcR have the following relationship: dcLav , u dcRav wherein K P and K I are parameters for PI control. In step 3, the modulation signal is generated by using a passive control method to control the first DCAC converter and the second DCAC converter after balancing the three-phase current of the primary side of the traction transformer and stabilizing the DC voltage of the variable current unit and adjusting the DC voltage of each variable current unit, and the passive control method comprises: For the control of the first DCAC converter, the variable current unit design formula based on passive control comprises: wherein R L and L L are the equivalent inductance and resistance of the first DCAC converter, R N is a virtual resistance, u Lp is the active component amplitude of the voltage at the secondary side 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 first DCAC converter actual output current, i crefLq is the reactive component amplitude of the first DCAC converter command current, i cLq is the reactive component amplitude of the first DCAC converter actual output current, in order to obtain the PWM signal, the above equation (6) needs to be transformed accordingly: u Lref = [cos ωt sin ωt] [u cLp u cLq ] T (7) The DC side voltage u of the i-th converter unit dcLi is subtracted from the voltage average u dcLav The difference is controlled by a PI controller to generate a fine tuning value, which is added to the reference value of the modulation signal, and the following relationship holds: wherein Δu rdLi is the fine tuning of the command current, t is the system running time; After the voltage equalization control, the instruction signal u of the current 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 instruction signal used to control the first DCAC converter of each variable flow unit to be fine-tuned, Δu Lrefi is the fine-tuned instruction signal used to control the first DCAC converter of the i-th variable flow 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 converter unit Lrefi with u Rrefi It is converted into a PWM signal to control the first DCAC converter and the second DCAC converter.

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