A high-frequency isolated hybrid through-type traction power supply device and its control method

Abstract

A high-frequency isolated hybrid through-type traction power supply device and its control method. The device includes a balanced traction transformer and a high-frequency isolated two-phase - single-phase conversion unit; the high-frequency isolated two-phase - single-phase conversion unit includes two input-side cascaded H-bridges, n three-active-bridge converters, and an output-side cascaded H-bridge; the input end of the balanced traction transformer is connected to the three-phase power grid, the two output ends of the balanced traction transformer are respectively connected to the input ends of the two input-side cascaded H-bridges, the output ends of the single-phase full-bridge modules of each stage of one of the input-side cascaded H-bridges are sequentially connected to one input end of each three-active-bridge converter, the output ends of the single-phase full-bridge modules of each stage of the other input-side cascaded H-bridge are sequentially connected to the other input end of each three-active-bridge converter, the output ends of each three-active-bridge converter are respectively connected to the input ends of the single-phase full-bridge modules of each stage of the output-side cascaded H-bridge, and the output end of the output-side cascaded H-bridge is connected to the traction catenary.

Description

Technical Field

[0001] The present invention relates to the technical field of power control, and particularly to a high-frequency isolated hybrid through traction power supply device and its control method. Background Art

[0002] In China, single-phase industrial frequency AC power supply mode is generally adopted in electrified railways. As a single-phase load with asymmetry, the traction load will inject a large amount of negative sequence current into the power system. To reduce the influence of negative sequence current, the adjacent power supply arms of the traction network are mostly cyclically phase-changed, but the electrical neutral section introduced thereby becomes a break point of the catenary, which will cause problems such as the locomotive passing through the neutral section and discontinuous power supply, affecting the economic and reliable operation of the traction power supply system.

[0003] The through traction power supply system can cancel the electrical neutral section on the traction network while solving the power quality problem, which conforms to the development trend of future electrified railways. At present, the through traction power supply device based on power electronics technology is one of the important ways to realize the traction power supply of electrified railways. At present, the "three-phase - single-phase" structure is a common type of through traction power supply device. For example, Figure 1 the topology structure of the through traction power supply device based on a three-phase - single-phase power electronic transformer shown in the figure can realize through power supply, but it is necessary to replace the existing traction transformer, and the transformation cost of a single substation is increased by about 10 million to 20 million yuan. Therefore, it is only applicable to newly built railways.

[0004] In order to minimize the transformation of traction substations and reduce the investment cost, it has been proposed to make full use of the existing traction transformer and adopt a hybrid through traction power supply device with a "two-phase - single-phase" structure to realize through power supply. According to the switching frequency of the transformer, the topology scheme of the "two-phase - single-phase" structure can be divided into a power frequency isolation type and a high-frequency isolation type. Figure 2 、 Figure 3 shows the existing power frequency isolation type scheme. This scheme requires an additional introduction of two groups of single-phase multi-tap transformers, which has a large floor area and a low power density. Limited by the site of the traction substation, it is difficult to popularize in some practical applications. While for a high-frequency transformer with the same power, the volume is about 1 / 10 of that of a power frequency isolation transformer, which can effectively reduce the equipment volume and facilitate system transformation. Therefore, a through traction power supply device based on a single-phase PET has been proposed, such as Figure 4 shown in the figure, but the number of devices required for this high-frequency isolation type scheme is large, the cost is high, and there are great challenges in practical applications. It is still necessary to further reduce the number of devices and the volume of the equipment and improve the power density of the equipment.

[0005] How to ensure that on the basis of realizing through traction power supply, further reduce the equipment volume, improve the system power density, reduce the transformation cost of the existing traction power supply system, and balance the economy and reliability of system operation is an urgent problem to be solved at present. Summary of the Invention

[0006] In order to reduce the volume of the equipment, improve the power density of the system, and reduce the transformation cost of the existing traction power supply system, the present invention provides a high-frequency isolation type hybrid through-traction power supply equipment and its control method.

[0007] To solve the above technical problems, the present invention adopts the following technical method: a high-frequency isolation type hybrid through-traction power supply equipment and its control method, including a balanced traction transformer, and further including a high-frequency isolation type two-phase-to-single-phase conversion unit; the high-frequency isolation type two-phase-to-single-phase conversion unit includes two input-side cascaded H-bridges, n three-active-bridge converters, and an output-side cascaded H-bridge; the input-side cascaded H-bridge and the output-side cascaded H-bridge are respectively composed of n single-phase full-bridge modules in cascade;

[0008] The input end of the balanced traction transformer is connected to the three-phase power grid, the two output ends of the balanced traction transformer are respectively connected to the input ends of the two input-side cascaded H-bridges, the output ends of the single-phase full-bridge modules of one input-side cascaded H-bridge are sequentially connected to one input end of each three-active-bridge converter, the output ends of the single-phase full-bridge modules of the other input-side cascaded H-bridge are sequentially connected to the other input end of each three-active-bridge converter, the output ends of each three-active-bridge converter are respectively connected to the input ends of the single-phase full-bridge modules of the output-side cascaded H-bridge, and the output end of the output-side cascaded H-bridge is connected to the traction catenary.

[0009] Further, an input inductor is connected in series between the input end of the input-side cascaded H-bridge and the output end of the balanced traction transformer, and a capacitor is connected in parallel between the output end of each single-phase full-bridge module of the input-side cascaded H-bridge and the input end of the three-active-bridge converter.

[0010] Still further, the three-active-bridge converter adopts a turns ratio of 1:1:1, and auxiliary inductors are connected to each port L TAB .

[0011] Even further, the output end of the output-side cascaded H-bridge is connected to the traction catenary electrically after being connected in series with an output inductor.

[0012] Still further, the power electronic devices used in the single-phase full-bridge modules in the three-active-bridge converter, as well as the single-phase full-bridge modules in the input-side cascaded H-bridge and the output-side cascaded H-bridge, are all IGBTs or MOSFETs or made of SiC or GaN materials.

[0013] As another aspect of the present invention, a control method for a high-frequency isolated hybrid through-traction power supply device controls the input-side cascaded H-bridge, the three-active-bridge converter, and the output-side cascaded H-bridge respectively. Among them, the input-side cascaded H-bridge is controlled for the stability control of the DC-side capacitor voltage. The control of the three-active-bridge converter includes achieving the power equalization control of each single-phase full-bridge module of the two input-side cascaded H-bridges and the cancellation control of the second-order ripple transfer of the DC-side capacitor voltage. The output-side cascaded H-bridge is controlled for the stability control of the output-side voltage and frequency.

[0014] Furthermore, the control method for the high-frequency isolated hybrid through-traction power supply device provided by the present invention further includes the electrical isolation control of the three-phase power grid. The balance traction transformer converts the three-phase voltage from the power grid into a two-phase voltage, which is input to the three-active-bridge converter through the input-side cascaded H-bridge, and the electrical isolation is achieved by the high-frequency isolation transformer of the three-active-bridge converter.

[0015] Preferably, when controlling the three-active-bridge converter, the following steps are included:

[0016] S1, collect and determine the operating parameters of the high-frequency isolated two-phase-to-single-phase conversion unit: detect in real time the DC-side capacitor voltages at the output ends of each single-phase full-bridge module of the two input-side cascaded H-bridges 、 , the DC-side currents 、 , the voltage and current at the output port of the three-active-bridge converter, and determine the auxiliary inductor value of the three-active-bridge converter and the voltage reference value at the output end;

[0017] S2, obtain the remaining components excluding the second-order ripple of the DC-side capacitor voltage 、 : input the DC-side capacitor voltages 、 obtained in step S1 into a low-pass filter to obtain the remaining components 、 excluding the second-order ripple of the DC-side capacitor voltage;

[0018] S3, calculate the powers 、 and P o of each port of the three-active-bridge converter: multiply the DC-side capacitor voltage obtained in step S1 by the DC-side current to obtain the power of the α port of the three-active-bridge converter, and multiply the DC-side capacitor voltage by the DC-side current Multiply to obtain the power of the β port of the three-active-bridge converter , multiply the voltage by the current to obtain the power of the output port of the three-active-bridge converter P o ;

[0019] S4. Calculate the common phase-shift duty ratio : Subtract the voltage reference value from the voltage obtained in step S1 to get the voltage error Δ . Input it into the PI regulator to obtain the common phase-shift duty ratio u， to control the voltage at the output end of the three-active-bridge converter;

[0020] S5. Calculate the correction amount of the phase-shift duty ratio of the secondary ripple transfer cancellation control loop of the three-active-bridge converter and : Subtract the remaining components excluding the secondary ripple of the DC-side capacitor voltage obtained in step S2 、 from the DC-side capacitor voltages 、 obtained in step S1 respectively to get the voltage deviation . Input them into the PR controller respectively to obtain the correction amount of the phase-shift duty ratio of the secondary ripple transfer cancellation control loop and ;

[0021] S6. Calculate the correction amount of the phase-shift duty ratio of the power equalization control loop of the three-active-bridge converter 、 : Subtract the value obtained by multiplying the power 、 obtained in step S3 by the coefficient 1 / 2 from the power P o respectively, and then input them into the PI regulator to obtain the correction amount of the phase-shift duty ratio of the power equalization control loop 、 ;

[0022] S7. Calculate the final phase-shift duty ratios of the α port and β port of the three-active-bridge converter 、 : Subtract the correction amount of the phase-shift duty ratio of the secondary ripple transfer cancellation control loop obtained in step S5 from the common phase-shift duty ratio and , and then subtract the correction amount of the phase-shift duty ratio of the power equalization control loop of the three-active-bridge converter 、 , obtain the final phase-shift duty ratio of the α port of the three-active-bridge converter and the final phase-shift duty ratio of the β port ;

[0023] S8. Calculate the PWM control signal PWMo of the output port of the three-active-bridge converter: Subtract half of the amplitude of the modulation signal from the modulation signal, input it into the PWM modulator, and output the PWM control signal PWMo of the output port of the three-active-bridge converter;

[0024] S9. Calculate the PWM control signals of the α port and the β port of the three-active-bridge converter and : Input the final phase-shift duty ratio of the α port of the three-active-bridge converter and the final phase-shift duty ratio of the β port calculated in S7 into the PWM modulator, and output the control signal of the α port and the control signal of the β port

[0025] Compared with the prior art, the advantages of the present invention are as follows:

[0026] The high-frequency isolation hybrid through-traction power supply equipment involved in the present invention, on the basis of making full use of the balance traction transformer of the existing traction substation, introduces a three-active-bridge converter, realizing a relatively small degree of transformation of the existing traction substation. This not only reduces the number of used devices, decreases the occupied volume of the equipment, improves the system power density, but also reduces the transformation investment cost of the traditional traction system.

[0027] (2) The control method of the high-frequency isolation hybrid through-traction power supply equipment involved in the present invention proposes a control strategy for secondary ripple transfer cancellation and power sharing, which can effectively achieve power sharing on the input side and cancellation of secondary ripple transfer of the DC-side capacitor voltage, effectively reduce the DC-side capacitor value, solve the negative-sequence power quality problem on the common power grid side, further optimize the equipment volume, and reduce the equipment cost. Description of the Drawings

[0028] Figure 1 is the topological structure diagram of the existing three-phase-to-single-phase power electronic transformer through-traction power supply equipment;

[0029] Figure 2 is the topological structure diagram of the existing single-phase-to-single-phase module through-traction power supply equipment;

[0030] Figure 3 is the topological structure diagram of the existing single-phase back-to-back module through-traction power supply equipment;

[0031] Figure 4 is the topological structure diagram of the existing through-traction power supply equipment based on two groups of single-phase PETs;

[0032] Figure 5 is the topological structure diagram of the high-frequency isolated hybrid through traction power supply equipment involved in the present invention;

[0033] Figure 6 is the block diagram for controlling the three-active-bridge converter in the control method of the high-frequency isolated hybrid through traction power supply equipment involved in the present invention;

[0034] Figure 7 is the waveform diagram of the DC-side capacitor voltages at the three ports of the three-active-bridge converter of the high-frequency isolated hybrid through traction power supply equipment in the normal working condition before and after adding control in the embodiment of the present invention; among them, (a) is the 1 waveform diagram of the DC-side capacitor voltage at the α port; (b) is the 1 waveform diagram of the DC-side capacitor voltage at the β port; (c) is the waveform diagram of the DC-side capacitor voltage at the output port;

[0035] Figure 8 is the power waveform diagram at the three ports of the three-active-bridge converter of the high-frequency isolated hybrid through traction power supply equipment in the normal working condition in the embodiment of the present invention; among them, (a) is the input power waveform diagram at the α 1 port; (b) is the input power waveform diagram at the β 1 port; (c) is the power waveform diagram at the output port;

[0036] Figure 9 is the positive and negative sequence current waveform diagram of the high-frequency isolated hybrid through traction power supply equipment in the normal working condition in the embodiment of the present invention;

[0037] Figure 10 is the three-phase current diagram of the grid side of the high-frequency isolated hybrid through traction power supply equipment in the normal working condition before and after adding control in the embodiment of the present invention. Detailed implementation mode

[0038] For the convenience of those skilled in the art to understand, the present invention will be further described below in conjunction with embodiments and drawings. The content mentioned in the implementation mode does not limit the present invention.

[0039] As Figure 5 shown, a high-frequency isolated hybrid through traction power supply equipment includes a balanced traction transformer and a high-frequency isolated two-phase-to-single-phase conversion unit. The high-frequency isolated two-phase-to-single-phase conversion unit is jointly composed of two input-side cascaded H-bridges, n three-active-bridge converters, and an output-side cascaded H-bridge. The three-active-bridge converter is composed of three single-phase full-bridge modules connected through a three-winding transformer. The turns ratio of the three-winding transformer is 1:1:1. Auxiliary inductors are also respectively connected to the α port, β port, and output port of the three-active-bridge converter The input - side cascaded H - bridge and the output - side cascaded H - bridge are respectively composed of n single - phase full - bridge modules in cascade. The specific value of n is determined according to the type of power electronic devices in actual engineering. In this embodiment, n = 20. The power electronic devices used in the single - phase full - bridge modules of the input - side cascaded H - bridge, the three - active - bridge converter, and the output - side cascaded H - bridge are all IGBT devices, MOSFET devices, or made of SiC or GaN materials.

[0040] As Figure 5 shown, the balance traction transformer adopts the YNvd wiring method, with its input end electrically connected to the 220kV / 110kV common three - phase power grid. The output ends of the α - phase (27.5kV) and β - phase (27.5kV) of the balance traction transformer are respectively electrically connected to the input ends of the two input - side cascaded H - bridges. This device is electrically isolated through the three - active - bridge converter, and input inductors are respectively connected in series between the two input - side cascaded H - bridges and the balance traction transformer. Since n = 20, the effective value of the input voltage of each single - phase full - bridge module of the two input - side cascaded H - bridges , the amplitude of the output voltage , and the voltage of the DC - side capacitor . In the two input - side cascaded H - bridges, the output ends of each single - phase full - bridge module of one input - side cascaded H - bridge are respectively connected to the α - ports of the 1st to 20th three - active - bridge converters through filter capacitors . The output ends of each single - phase full - bridge module of the other input - side cascaded H - bridge are respectively connected to the β - ports of the 1st to 20th three - active - bridge converters through filter capacitors . The output ends of the 1st to 20th three - active - bridge converters are respectively connected to filter capacitors and then connected to the input ends of each single - phase full - bridge module of the output - side cascaded H - bridge. The output ends of the output - side cascaded H - bridge are connected in series with an output inductor and then connected to the traction catenary to supply power to the traction load.

[0041] The control method of the aforementioned high - frequency isolation hybrid through - type traction power supply equipment mainly includes the control of the input - side cascaded H - bridge, the three - active - bridge converter, and the output - side cascaded H - bridge. The balance traction transformer converts the three - phase voltage from the power grid into two - phase voltage, which is input into the three - active - bridge converter through the input - side cascaded H - bridge, and electrical isolation is achieved by the high - frequency isolation transformer of the three - active - bridge converter; the input - side cascaded H - bridge control is used to stabilize the voltage of the DC - side capacitor. The control of the three - active - bridge converter includes achieving power equalization control of each single - phase full - bridge module of the two input - side cascaded H - bridges and canceling the control of the secondary ripple transfer of the DC - side capacitor voltage. The control of the output - side cascaded H - bridge is used to stabilize the output - side voltage and frequency. At present, the control of the input - side and output - side cascaded H - bridges is very mature, so no specific description will be made here. Next, the present invention will introduce the control of the three - active - bridge converter in detail.

[0042] As Figure 6 shown, the control of the three-active-bridge converter includes the following steps:

[0043] S1. Collect and determine the operating parameters of the high-frequency isolation type two-phase to single-phase conversion unit: Detect in real time the DC-side capacitor voltages at the output ends of the single-phase full-bridge modules of each stage of the two cascaded H-bridges on the two input sides , the DC-side current , the voltage and current at the output port of the three-active-bridge converter, and determine the value of the auxiliary inductor of the three-active-bridge converter and the voltage reference value at the output end. Here, it is worth mentioning that the value of the auxiliary inductor of the three-active-bridge converter can be estimated according to the transmitted power.

[0044] S2. Obtain the remaining components excluding the second-order ripple of the DC-side capacitor voltage and : Input the DC-side capacitor voltage obtained in step S1 into a low-pass filter to obtain the remaining components and excluding the second-order ripple of the DC-side capacitor voltage.

[0045] S3. Calculate the powers and of each port of the three-active-bridge converter: Multiply the DC-side capacitor voltage obtained in step S1 by the DC-side current to obtain the power of port α of the three-active-bridge converter, multiply the DC-side capacitor voltage by the DC-side current to obtain the power of port β of the three-active-bridge converter, and multiply the voltage by the current to obtain the power of the output port of the three-active-bridge converter.

[0046] S4. Calculate the common phase-shift duty ratio : Subtract the voltage reference value from the voltage obtained in step S1 to get the voltage error quantity ， , input it into a PI regulator to obtain the common phase-shift duty ratio for controlling the voltage at the output end of the three-active-bridge converter.

[0047] S5. Calculate the correction amount of the phase-shift duty ratio for the secondary ripple transfer cancellation control loop of the three-active-bridge converter : Subtract the DC-side capacitor voltage obtained in step S1 from the remaining components obtained in step S2 after removing the second-order ripple of the DC-side capacitor voltage 、 respectively, to obtain a voltage deviation and input them into a PR controller respectively to obtain the correction amounts of the phase-shifted duty cycle of the second-order ripple transfer cancellation control loop and 。

[0048] S6. Calculate the correction amounts of the phase-shifted duty cycle of the power equalization control loop of the three-active-bridge converter 、 : Subtract the power obtained in step S3 from the value obtained by multiplying the power by the coefficient 1 / 2 respectively, and then input them into a PI regulator respectively to obtain the correction amounts of the phase-shifted duty cycle of the power equalization control loop 、 。

[0049] S7. Calculate the final phase-shifted duty ratios of the α and β ports of the three-active-bridge converter : Subtract the correction amount of the phase-shifted duty cycle of the second-order ripple transfer cancellation control loop and obtained in step S5 from the common phase-shifted duty ratio obtained in step S4, and then subtract the correction amounts of the phase-shifted duty cycle of the power equalization control loop of the three-active-bridge converter 、 obtained in step S6 to obtain the final phase-shifted duty ratio of the α port of the three-active-bridge converter and the final phase-shifted duty ratio of the β port 。

[0050] S8. Calculate the PWM control signal PWMo of the output port of the three-active-bridge converter: Subtract half of the amplitude of the modulation signal from the modulation signal and input it into a PWM modulator to output the PWM control signal PWMo of the output port of the three-active-bridge converter.

[0051] S9. Calculate the PWM control signals of the α and β ports of the three-active-bridge converter 、 : Input the final phase-shifted duty ratio of the α port and the final phase-shifted duty ratio of the β port calculated in S7 into a PWM modulator to output the control signal of the α port and the control signal of the β port.

[0052] To verify the economy and effectiveness of this patent, the high-frequency isolated hybrid through-traction power supply equipment involved in the present invention and several existing schemes are compared and analyzed below. Among them, Scheme 1 is a through-traction power supply equipment based on single-phase to single-phase modules, as shown in Figure 2 ; Scheme 2 is a through-traction power supply equipment based on single-phase back-to-back modules, as shown in Figure 3 ; Scheme 3 is a through-traction power supply equipment based on three-phase to single-phase power electronic transformers, as shown in Figure 1 ; Scheme 4 is a through-traction power supply equipment based on two groups of single-phase PETs, as shown in Figure 4 ; The present invention is a high-frequency isolated hybrid through-traction power supply equipment, as shown in Figure 5 .

[0053] For the convenience of comparative discussion, the above schemes are all carried out according to the following conditions: the number of cascaded H-bridges in the input side n = 20, the effective value of the input voltage of each stage ; the amplitude of the output voltage ; the DC-side capacitor voltage ; the power semiconductors all adopt IGBT devices of 3300V 1500A. The comparison of the above schemes is shown in Table 1:

[0054]

[0055] To more intuitively compare the volume of the equipment, the inductors of the equipment are all taken as 5mH, and its volume is about 0.0379dm 3 ; the capacitors are taken as 2mF, and the volume is about 35.4dm 3 . It can be obtained from Table 1 that:

[0056] (1) Compared with Scheme ①, the number of active / passive devices required by the present invention is the same. The difference lies in the switching frequency and number of transformers used. In Scheme ①, three single-phase multi-winding transformers are required at the input end, which seriously increases the system cost and volume.

[0057] (2) Compared with Scheme ②, the number of active / passive devices required by the present invention both increases, but there are still multi-tap power frequency transformers in the topology of Scheme ②. Generally, multiple filter inductors or a large leakage inductance of the transformer are required, and the equipment volume is relatively large, and the requirements for the actual application environment are relatively high.

[0058] (3) Compared with Scheme ③, the number of active devices required by the present invention is reduced by 40.0%, the number of passive devices is reduced by 49.2%, and the number of high-frequency isolation transformers is reduced by 66.7%. The number of devices to be put into use is significantly reduced, the equipment volume is further reduced, and the transformation investment cost is reduced.

[0059] (4) Compared with Solution ④, the number of active devices required by the present invention is reduced by 25.0%. For the required passive devices, the number of inductors increases by 43.2%, the number of capacitors decreases by 25%, and the number of transformers decreases by 50%. From the data, it can be seen that the volume increased due to the number of inductors is less than the volume decreased due to the reduction in the number of capacitors. In addition, at the same switching frequency and withstand voltage level, the power density of the dual-active-bridge converter (DAB) is about 1.92 kW / L, and the power density of the triple-active-bridge converter (TAB) is about 7.45 kW / L, with the power density being increased by 48.5%. Moreover, the control method provided by the present invention can achieve the cancellation of the secondary ripple transfer on the input side, the DC-side capacitor value can be further reduced, the volume of the equipment is decreased, the power density is increased, and the retrofit investment cost is reduced.

[0060] This embodiment also builds a high-frequency isolation hybrid through-traction power supply equipment model on the MATLAB / Simulink simulation platform to verify the feasibility of the control method of the high-frequency isolation hybrid through-traction power supply equipment involved in the present invention. The simulation parameters are shown in Table 2.

[0061]

[0062] Verify the effectiveness of the control method of the high-frequency isolation hybrid through-traction power supply equipment involved in the present invention under normal conditions (the DC-side capacitor voltages of the three ports of the triple-active-bridge converter are all 2.1 kV). Since the control methods and output waveforms of each single-phase full-bridge module and ( i = 1, 2... 20) of the two input-side cascaded H-bridges are the same, the single-phase full-bridge modules α 1 and β 1 are taken as examples for comparative analysis.

[0063] (1) Verification of the secondary ripple transfer cancellation control loop: The DC-side capacitor voltages of the α 1 port, β 1 port, and output port of the triple-active-bridge converter before and after adding the control are shown in Figure 7. Before adding the control loop, as shown in Figures 7(a) and 7(b), the ripple values of the DC-side capacitor voltages of the α 1 port and β 1 port are about ±200 V. After adding the control loop, the ripple values of the DC-side capacitor voltages of the α 1 port and β 1 port are about ±20 V, and the effect of suppressing the secondary ripple is significant.

[0064] (2) Verification of the power sharing control loop: The input power of the α 1 port is 0.4382 MW, and the input power of the β 1The input power of the port is 0.4308 MW, and the output port power is 0.8682 MW. The control strategy of the high-frequency isolation hybrid through-traction power supply equipment can evenly distribute the input port power of the three-active-bridge converter and meet the accuracy requirements. The positive and negative sequence currents and three-phase currents on the AC side are measured by Figure 9 , Figure 10 as shown. It can be seen that after the simulation model stabilizes, the negative sequence current approaches 0, effectively solving the problem of negative sequence current on the common grid side.

[0065] As can be seen from the above, based on the full utilization of the existing balanced traction transformer, the high-frequency isolation hybrid through-traction power supply equipment proposed by the present invention adopts a high-frequency isolation two-phase-to-single-phase conversion unit, effectively reducing the equipment volume and increasing the equipment power density, thereby reducing the transformation investment cost. The control method of the high-frequency isolation hybrid through-traction power supply equipment provided by the present invention can achieve the equal distribution of the input power of the α and β phases on the input side, solve the problem of negative sequence current on the common power grid side. In addition, this method can effectively cancel the secondary ripple on the DC side of the α and β phases, reduce the voltage impact while reducing the capacitance value of the DC side capacitor, further increasing the equipment power density, and ensuring the economic and reliable operation of the high-frequency isolation hybrid through-traction power supply equipment. Generally speaking, the high-frequency isolation hybrid through-traction power supply equipment and its control method provided by the present invention have strong engineering practicability, can balance the economy and reliability of system operation, and contribute to the further popularization and application of through-traction power supply equipment.

[0066] The above embodiments are the preferred implementation schemes of the present invention. In addition, the present invention can also be implemented in other ways. Any obvious replacement without departing from the concept of the technical solution of the present invention is within the protection scope of the present invention.

[0067] To make it easier for those of ordinary skill in the art to understand the improvements of the present invention over the prior art, some of the drawings and descriptions of the present invention have been simplified, and for the sake of clarity, some other elements have also been omitted from this application document. Those of ordinary skill in the art should be aware that these omitted elements may also constitute the content of the present invention.

Claims

1. A high-frequency isolated hybrid through-traction power supply device, including a balance traction transformer, Characterized in that: It further includes a high-frequency isolated two-phase-to-single-phase conversion unit; the high-frequency isolated two-phase-to-single-phase conversion unit includes two input-side cascaded H-bridges, n three-active-bridge converters, and an output-side cascaded H-bridge; the input-side cascaded H-bridge and the output-side cascaded H-bridge are respectively cascaded by n single-phase full-bridge modules; The input end of the balance traction transformer is connected to the three-phase power grid, the two output ends of the balance traction transformer are respectively connected to the input ends of the two input-side cascaded H-bridges, the output ends of the single-phase full-bridge modules of each stage of one input-side cascaded H-bridge are sequentially connected to one input end of each three-active-bridge converter, the output ends of the single-phase full-bridge modules of each stage of the other input-side cascaded H-bridge are sequentially connected to the other input end of each three-active-bridge converter, the output ends of each three-active-bridge converter are respectively connected to the input ends of the single-phase full-bridge modules of each stage of the output-side cascaded H-bridge, and the output end of the output-side cascaded H-bridge is connected to the traction catenary; An input inductor is connected in series between the input end of the input-side cascaded H-bridge and the output end of the balance traction transformer, and a capacitor is connected in parallel between the output end of the single-phase full-bridge module of each stage of the input-side cascaded H-bridge and the input end of the three-active-bridge converter; The three-active-bridge converter adopts a turns ratio of 1:1:1, and an auxiliary inductor is connected to each port ; The output end of the output-side cascaded H-bridge is connected to the traction catenary electrically after being connected in series with an output inductor.

2. The high-frequency isolated hybrid through-traction power supply device according to claim 1, Characterized in that: The power electronic devices used in the single-phase full-bridge modules in the three-active-bridge converter and the single-phase full-bridge modules in the input-side cascaded H-bridge and the output-side cascaded H-bridge are all IGBTs or MOSFETs or made of SiC or GaN materials.

3. A control method for the high-frequency isolated hybrid through-traction power supply device according to claim 2, Characterized in that: The input-side cascaded H-bridge, the three-active-bridge converter, and the output-side cascaded H-bridge are respectively controlled. Among them, the input-side cascaded H-bridge is controlled for the stability of the DC-side capacitor voltage, the control of the three-active-bridge converter includes achieving the power equalization control of the single-phase full-bridge modules of each stage of the two input-side cascaded H-bridges and the cancellation control of the second-order ripple of the DC-side capacitor voltage, and the output-side cascaded H-bridge is controlled for the stability of the output-side voltage and frequency.

4. The control method for the high-frequency isolated hybrid through-traction power supply device according to claim 3, Characterized in that: It further includes the electrical isolation control of the three-phase power grid. The balance traction transformer converts the three-phase voltage from the power grid into two-phase voltages, which are input to the three-active-bridge converter through the input-side cascaded H-bridge, and the electrical isolation is realized by the high-frequency isolation transformer of the three-active-bridge converter.

5. The control method for the high-frequency isolated hybrid through-traction power supply device according to claim 3 or 4, Characterized in that: When controlling the three-active-bridge converter, it includes the following steps: S1, Collect and determine the operating parameters of the high-frequency isolated two-phase to single-phase conversion unit: Real-time detect the DC-side capacitor voltages at the output terminals of each single-phase full-bridge module in each stage of the two cascaded H-bridges on the two input sides , the DC-side current , the voltage at the output port of the three-active-bridge converter and the current , determine the auxiliary inductor value of the three-active-bridge converter and the voltage reference value at the output terminal ; S2, Obtain the remaining components after removing the second-order ripple of the DC-side capacitor voltage : Input the DC-side capacitor voltage obtained in step S1 into a low-pass filter to obtain the remaining components after removing the second-order ripple of the DC-side capacitor voltage ; S3, Calculate the power of each port of the three-active-bridge converter and : Multiply the DC-side capacitor voltage obtained in step S1 by the DC-side current to get the power of the port of the three-active-bridge converter . Multiply the DC-side capacitor voltage by the DC-side current to get the power of the port of the three-active-bridge converter . Multiply the voltage by the current to get the power of the output port of the three-active-bridge converter ; S4, Calculate the common phase-shift ratio : Subtract the voltage obtained in step S1 from the voltage reference value to obtain the voltage error quantity ， Input it into the PI regulator to obtain the common phase-shift duty cycle to control the voltage at the output terminal of the three-active-bridge converter; S5, calculate the phase-shift duty cycle correction amount of the secondary ripple transfer cancellation control loop of the three-active-bridge converter and : Subtract the DC-side capacitor voltage obtained in step S1 from the remaining components excluding the secondary ripple of the DC-side capacitor voltage obtained in step S2, to obtain the voltage deviation and input them into the PR controller respectively to obtain the phase-shift duty cycle correction amount and ; S6. Calculate the correction amount of the phase-shifted duty cycle of the power sharing control loop of the three-active-bridge converter : Subtract the value obtained by multiplying the power obtained in step S3 by the coefficient 1 / 2 from the power respectively, and then input them into the PI regulator respectively to obtain the correction amount of the phase-shifted duty cycle of the power sharing control loop ; ; S7, Calculate the three-active-bridge converter Port and Final phase-shift ratio of the port : Use the common phase-shift ratio obtained in step S4 Subtract the correction amount of the phase-shift duty ratio of the secondary ripple transfer cancellation control loop obtained in step S5 And , Then subtract the correction amount of the phase-shift duty ratio of the power equalization control loop of the three-active-bridge converter obtained in step S6 , , To obtain the final phase-shift ratio of the port of the three-active-bridge converter And the final phase-shift ratio of the port; S8. Calculate the PWM control signal PWMo at the output port of the three-active-bridge converter: Subtract half of the amplitude of the modulation signal from the modulation signal and input it into the PWM modulator to output the PWM control signal PWMo at the output port of the three-active-bridge converter; S9, Calculate the three-active-bridge converter port and the PWM control signals of the port , : Input the final phase-shift duty ratios of the three-active-bridge converter port calculated in S7 and the final phase-shift duty ratio of the port into the PWM modulator, and output the control signal of the port and the control signal of the .

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