An auxiliary power supply system

Abstract

The application provides an auxiliary power supply system, which comprises a second DC bus for supplying power to a DC600V load; an auxiliary power supply system, which comprises: a first LLC resonant conversion circuit, which converts voltage into a high-frequency rectangular wave, and provides a stable second voltage after isolation conversion and rectification of the high-frequency rectangular wave; an API inversion circuit, which converts the second voltage into a PWM voltage, and outputs an AC380V voltage after filtering; a low-voltage power supply circuit, which outputs a DC110V voltage after DC / DC isolation conversion and filtering of the second voltage; a second LLC resonant conversion circuit, which converts voltage into a high-frequency rectangular wave, and provides a third voltage after isolation conversion and rectification; and an LC filtering circuit, which filters the third voltage, and obtains a DC600V voltage after anti-reverse diode of the filtered third voltage. The application effectively solves the problems of circulating current between DC600V and AC380V generated when the first AC bus is connected to the grid and the second DC bus is connected in parallel, voltage distortion of a remote end during DC600V parallel power supply, and IGBT hard switching leading to thermal failure during LLC full-bridge phase-shift soft start with different HVAC loads.

Description

Technical Field

[0001] This invention relates to the field of auxiliary power supply system technology, and more particularly to an auxiliary power supply system. Background Technology

[0002] Subway vehicle auxiliary power supply systems typically use an AC380V bus to power the vehicle's air conditioning equipment. The air conditioning equipment itself contains rectifier and inverter stages. The rectifier stage converts the AC380V from the auxiliary power supply bus into intermediate DC power, while the inverter stage converts this intermediate DC power into AC power to supply the air conditioning compressor, fan, and other air conditioning loads. Therefore, the power supply from the vehicle's mains (pantograph / third rail) to the air conditioning loads requires multiple power conversions, resulting in low system efficiency. (See below.) Figure 1 As shown, 1 is a DC110V load and 2 is an AC380V load.

[0003] However, the DC 600V load (mainly the vehicle's air conditioning equipment) accounts for the largest proportion of the load in subway vehicles. The DC 600V load cannot be directly output through the auxiliary power supply AC / DC. The DC 600V load and the AC 380V load cannot be connected to the grid for power supply at the same time, which makes the working efficiency of the vehicle's auxiliary power supply system relatively low. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an auxiliary power supply system.

[0005] The technical solution of the present invention is as follows:

[0006] An auxiliary power supply system includes: a first DC bus for supplying power to a DC 110V load; a first AC bus for supplying power to an AC 380V load; the subway train auxiliary power supply system further includes:

[0007] The second DC bus is used to supply power to DC 600V loads;

[0008] An auxiliary power supply system has its input terminal connected to the mains voltage and its output terminal connected to the first DC bus, the first AC bus, and the second DC bus; the auxiliary power supply system includes:

[0009] The first LLC resonant converter circuit is used to convert the voltage into a high-frequency rectangular wave and to provide a stable second voltage after isolating, converting and rectifying the high-frequency rectangular wave.

[0010] The API inverter circuit is connected to the output of the first LLC resonant converter circuit and is used to convert the second voltage into a PWM voltage. The PWM voltage is filtered and then output as AC380V voltage.

[0011] A low-voltage power supply circuit is connected between the first LLC resonant converter circuit and the API inverter circuit, and is used to output DC110V voltage after DC / DC isolation conversion and filtering of the second voltage.

[0012] The second LLC resonant converter circuit is used to convert the voltage into a high-frequency rectangular wave, and to provide a third voltage after isolating, converting and rectifying the high-frequency rectangular wave.

[0013] An LC filter circuit and a reverse protection diode are provided. The LC filter circuit is connected to the output terminal of the second LLC resonant converter circuit and is used to filter the third voltage. The reverse protection diode is connected to the output terminal of the LC filter circuit, and the filtered third voltage is passed through the reverse protection diode to obtain a DC 600V voltage.

[0014] In some implementations, the auxiliary power supply system further includes:

[0015] The pre-charging circuit is connected to the mains voltage.

[0016] An input filter circuit, connected to the pre-charging circuit, is used to filter the mains voltage;

[0017] The Boost / Buck circuit, connected to the input filter circuit, is used to convert the filtered grid voltage into a first voltage and output it to the first LLC resonant converter circuit and the second LLC resonant converter circuit.

[0018] In some implementations, both the first LLC resonant converter circuit and the second LLC resonant converter circuit employ a full-bridge LLC resonant converter circuit.

[0019] In some implementations, the full-bridge LLC resonant converter circuit includes: a full-bridge IGBT circuit, a high-frequency transformer whose input terminal is connected to the full-bridge IGBT circuit, and a full-bridge uncontrolled rectifier circuit connected to the output terminal of the high-frequency transformer.

[0020] In some implementations, the DC600V load includes an air conditioning unit, which uses a DC / AC converter module to convert the DC600V voltage into AC voltage to supply power to the air conditioning unit.

[0021] In some implementations, the auxiliary power supply system further includes an EMI circuit, the input of which is connected to the negative terminal of the anti-reverse diode, and the output of the EMI circuit outputs a DC 600V voltage.

[0022] In some implementations, the output of the EMI circuit is connected to a contactor that conducts when the DC voltage of its branch reaches DC600V, so that the DC600V voltage is applied to a DC600V load.

[0023] In some implementations, the auxiliary power supply system is a subway train auxiliary power supply system.

[0024] In some implementations, the low-voltage power supply circuit includes a DC-DC converter circuit and an output filter circuit connected to its downstream end.

[0025] In some implementations, the API inverter circuit includes an IGBT inverter circuit and a three-phase AC output filter circuit connected to its downstream end.

[0026] Compared with the prior art, one or more embodiments of the present invention can bring at least the following beneficial effects:

[0027] This invention employs a single-channel LLC resonant converter circuit and a reverse protection diode. Due to the reverse cutoff of the reverse protection diode and the electrical isolation characteristics of the high-frequency transformer, the circulating current problem between DC600V and AC380V generated when the first AC bus is connected to the grid and the second DC bus is connected in parallel can be effectively solved. Due to the LC filter circuit, the problem of voltage distortion at the far end when DC600V is connected in parallel can be effectively solved. Due to the DC600V output contactor, the problem of thermal failure caused by the hard switching of IGBT when performing LLC full-bridge phase-shift soft start with different HVAC loads can be effectively solved. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope.

[0029] Figure 1 This is a diagram of the vehicle auxiliary power supply system architecture in related technologies;

[0030] Figure 2 This is a schematic diagram of an auxiliary power supply system architecture provided in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of an auxiliary power supply system provided in an embodiment of the present invention;

[0032] Figure 4 This is the full-bridge LLC resonant converter circuit provided in the embodiments of the present invention;

[0033] Figure 5 This is a schematic diagram of an air conditioning equipment solution provided in an embodiment of the present invention;

[0034] Among them, 1-DC110V load, 2-AC380V load; 3-DC600V load. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0036] The relevant technology uses an AC380V bus to power the vehicle's air conditioning equipment. The air conditioning equipment internally incorporates a rectifier and an inverter. The rectifier converts the AC380V auxiliary power supply bus into intermediate DC power, while the inverter converts this intermediate DC power into AC power to supply the air conditioning compressor, fan, and other equipment. Therefore, the power from the vehicle's power grid (pantograph / third rail) to the air conditioning equipment requires multiple power conversions, resulting in low system efficiency. Figure 1 As shown.

[0037] To address the aforementioned problems, this embodiment provides an auxiliary power supply system, such as... Figure 2 As shown, the auxiliary power supply system is a subway train auxiliary power supply system, which includes: a first DC bus for supplying power to DC 110V load 1; a first AC bus for supplying power to AC 380V load 2; the auxiliary power supply system also includes:

[0038] The second DC bus is used to supply power to DC 600V load 3;

[0039] The auxiliary power supply system has its input connected to the mains voltage and its output connected to the first DC bus, the first AC bus, and the second DC bus. The auxiliary power supply system includes:

[0040] The first LLC resonant converter circuit is used to convert the voltage into a high-frequency rectangular wave and to provide a stable second voltage after isolating, converting and rectifying the high-frequency rectangular wave.

[0041] The API inverter circuit is connected to the output of the first LLC resonant converter circuit to convert the second voltage into a PWM voltage. The PWM voltage is filtered and then output as AC380V voltage.

[0042] The low-voltage power supply circuit is connected between the first LLC resonant converter circuit and the API inverter circuit. It is used to output DC110V voltage after DC / DC isolation conversion and filtering of the second voltage.

[0043] The second LLC resonant converter circuit is used to convert the voltage into a high-frequency rectangular wave, and to provide a third voltage after isolating, converting and rectifying the high-frequency rectangular wave.

[0044] An LC filter circuit and a reverse protection diode are used. The LC filter circuit is connected to the output of the second LLC resonant converter circuit to filter the third voltage. The reverse protection diode is connected to the output of the LC filter circuit. The filtered third voltage is then passed through the reverse protection diode to obtain a DC 600V voltage.

[0045] In practical applications, at least one auxiliary power system (APS) is required. The number of auxiliary power systems can be set according to the actual load requirements of the subway car. The auxiliary power system integrates DC 600V, AC 380V, and DC 110V power outputs. The first DC bus (DC 110V) operates in parallel redundant power supply mode, primarily supplying DC 110V loads; the first AC bus (AC 380V) can adopt grid-connected / extended power supply mode, primarily supplying AC 380V loads; the second DC bus (DC 600V) operates in parallel redundant power supply mode, primarily supplying HVAC (Heating, Ventilation, and Air Conditioning) loads and DC 600V loads. The auxiliary power system can refer to an auxiliary power supply box.

[0046] In the auxiliary power supply system of this embodiment, in addition to the traditional AC380V power supply bus (first AC bus) and DC110V power supply bus (first DC bus), a DC600V power supply bus (second DC bus) is added. This bus is specifically used for powering the DC600V load of the subway vehicles (the DC600V load mainly includes air conditioning equipment). The main technical problems it solves include:

[0047] 1) The DC600V load (mainly including air conditioning equipment) constitutes the largest proportion of the load in subway cars. Replacing the original AC380V power supply bus with a DC600V power supply bus to power the DC600V load allows the DC600V load to directly obtain its required DC600V voltage via DC / AC switching. Furthermore, the inverter circuit for this DC600V auxiliary power supply can be simplified, effectively improving the power density of the auxiliary inverter and the efficiency of the vehicle's auxiliary systems. After using the DC600V bus for air conditioning equipment, its internal AC / DC switching circuit can be eliminated, further improving the efficiency of the auxiliary power supply system and effectively saving energy consumed by the auxiliary system.

[0048] 2) If the auxiliary power supply system adopts a scheme that simultaneously supplies power to both the DC600V bus and the AC380V bus, it can effectively solve the problem of intermediate circulating current between DC600V and AC380V. This intermediate circulating current problem can easily lead to the failure of the DC / AC auxiliary power supply inverter support capacitor.

[0049] 3) If the auxiliary power supply system adopts a scheme that simultaneously supplies power to both DC600V and AC380V bus, it can effectively solve the problem of simultaneous grid connection of DC600V and AC380V, and effectively improve the availability of auxiliary power.

[0050] 4) The auxiliary power supply system is equipped with a DC600V bus output contactor, which can match different HVAC loads. It can effectively solve the problem of thermal failure caused by the LLC resonant IGBT working in hard switching state during the DC600V phase shift soft start process. The contactor is closed to connect the air conditioning load after the DC600V phase shift is established, which effectively improves the reliability of the auxiliary power supply.

[0051] In some implementations, the aforementioned auxiliary power supply system also includes:

[0052] The pre-charging circuit is connected to the mains voltage.

[0053] The input filter circuit, connected to the pre-charge circuit, is used to filter the mains voltage;

[0054] The Boost / Buck circuit, connected to the input filter circuit, is used to convert the filtered grid voltage into a first voltage output to the first LLC resonant converter circuit and the second LLC resonant converter circuit.

[0055] The pre-charging circuit includes contactors and resistors, and its main function is to reduce the charging current of the capacitor, thereby reducing the current surge and extending the capacitor's lifespan. For example, the pre-charging circuit may include two contactors, one of which is connected in series with a resistor and then in parallel with the other contactor.

[0056] The input filter circuit includes a second-order filter circuit, which may include a reactor, a capacitor, and a damping resistor. One end of the reactor is connected to the output of the pre-charge circuit, and the other end is connected to the input of the Boost / Buck circuit. One end of the capacitor is connected to the other end of the reactor, and the other end of the capacitor is connected to the damping resistor. The other end of the damping resistor is connected to the negative terminal of the input mains voltage for return current. Its main function is to absorb harmonic voltage at the DC input terminal, suppress high-frequency signals and voltage spikes in the input voltage, and suppress interference from the auxiliary power supply system. The damping resistor also accelerates the attenuation of output voltage ripple when the mains voltage fluctuates.

[0057] The Boost / Buck circuit includes a reactor, an IGBT device, and a capacitor. The reactor is connected in series with a diode. The collector of the IGBT device is connected between the reactor and the positive terminal of the diode. One end of the capacitor is connected to the negative terminal of the diode. The emitter of the IGBT device is connected to the other end of the capacitor, and the gate is connected to the IGBT driver board and controlled by an auxiliary power control unit. Its main function is to convert the filtered mains voltage into a stable first voltage DC_Link1 output, which is then filtered by a capacitor to provide a stable voltage for the subsequent LLC resonant converter circuit.

[0058] In some implementations, both the first and second LLC resonant converter circuits employ a full-bridge LLC resonant converter circuit. For example, using... Figure 4 The diagram shows a full-bridge LLC resonant converter circuit. This circuit includes a full-bridge IGBT circuit, a high-frequency transformer connected to the input of the IGBT circuit, and a full-bridge uncontrolled rectifier circuit connected to the output of the high-frequency transformer. Its main function is to convert the output voltage of the Boost / Buck circuit into a high-frequency rectangular wave, which, after isolation conversion by the high-frequency transformer and full-bridge rectification, provides a stable second voltage, DC_link2, to the subsequent API inverter circuit. Figure 4 In the diagram, V1 to V4 are IGBT devices, D4 to D7 are diode devices, Cr is a resonant capacitor, and L... m For the magnetizing inductor, L r It is a resonant inductor.

[0059] This embodiment employs an LLC resonant converter circuit, which enables zero-voltage turn-on and low-current turn-off, significantly reducing the losses of switching devices. Simultaneously, it increases the operating frequency of the high-frequency transformer, allowing for a high-frequency, miniaturized design. After voltage reduction and isolation by the high-frequency transformer, the high-frequency rectangular wave is converted into a DC 600V voltage via a rectifier circuit. This voltage is then filtered by a downstream filter circuit, diode isolation, and EMI circuitry to output a stable DC 600V supply voltage for powering the vehicle's air conditioning load.

[0060] In some implementations, the API inverter circuit includes an IGBT inverter circuit and a three-phase AC output filter circuit connected to its back end. This inverter circuit primarily converts the second voltage DC_link2 output from the LLC resonant converter circuit into a PWM voltage. After passing through the three-phase AC output filter circuit, a near-sinusoidal AC 380V voltage output with low harmonic content is obtained. The three-phase AC output filter circuit can be an LC filter circuit. The IGBT inverter circuit employs a PWM pulse width modulation control strategy, not limited to two-level or three-level inverter circuits that convert DC voltage into three-phase AC PWM voltage. As an auxiliary power inverter (API), it differs from the internal inverter of the air conditioning system.

[0061] In some implementations, the low-voltage power supply circuit includes a DC-DC converter circuit and an output filter circuit connected to its back end. This output filter circuit may include at least one diode. The main function of the low-voltage power supply circuit is to obtain a stable DC 110V voltage after the second voltage DC_link2 is converted by DC / DC isolation and filtered. The low-voltage power supply circuit (LVPS) functionally integrates vehicle low-voltage power supply and battery charging functions. Figure 3 The diode connected after the DC-DC converter circuit is only an example of an output filter circuit. In practical applications, at least one diode may include two diodes connected in parallel to reduce the voltage drop across the diode and increase the current withstand stress at the diode terminals.

[0062] In some implementations, the auxiliary power supply system also includes an EMI circuit, whose input is connected to the negative terminal of a reverse protection diode, and whose output is a DC 600V voltage. A second LLC resonant converter circuit, an LC filter circuit, a reverse protection diode, and the EMI circuit form a DC 600V output circuit. A third voltage, DC_Link3, is obtained through a separate LLC resonant converter circuit. This third voltage, after passing through an LC filter circuit and a reverse protection diode, is combined with the EMI circuit to obtain a stable DC 600V output voltage.

[0063] In some cases, such as Figure 3 As shown, a contactor is connected to the output of the EMI circuit. The contactor conducts when the DC voltage in its branch reaches DC600V, allowing the DC600V voltage to be applied to the DC600V load. Because of the contactor, the DC voltage can be fully applied only after the start-up reaches DC600V, effectively preventing the LLC resonant converter circuit from operating in a hard-switching state due to load start-up. This avoids excessive switching losses in the switching transistor, abnormally high IGBT junction temperature, and ultimately, IGBT over-temperature failure.

[0064] In some implementations, the auxiliary power system also includes an emergency starting power supply (DBPS). When the vehicle battery fails or is depleted, the train can directly convert the grid voltage to a control voltage (typically DC110V) through the DBPS, enabling the auxiliary power supply to work normally and provide the low-voltage power supply (typically DC110V) required for vehicle activation.

[0065] In some implementations, the DC600V load includes an air conditioning unit (HVAC), which uses a DC / AC converter module to convert the DC600V voltage into AC voltage to power the air conditioning unit.

[0066] HVAC solutions for air conditioning equipment, such as Figure 5 As shown, in related technologies, air conditioning equipment powered by AC380V requires first rectifying the AC power into DC power through a rectifier circuit, and then inverting the DC power into AC voltage suitable for the motor and other loads of the air conditioning equipment. This process involves two stages of circuit conversion, increasing circuit conversion losses and hindering energy conservation. In contrast, the air conditioning equipment in this embodiment is powered by DC600V. After the DC600V voltage is connected, it is directly inverted into AC voltage suitable for the air conditioning equipment load. This process involves only one stage of circuit conversion, effectively reducing losses caused by circuit conversion.

[0067] This embodiment introduces a DC 600V power supply bus, effectively reducing the AC / DC conversion stage of the air conditioning equipment and improving the efficiency of the auxiliary power supply system. By employing a single-channel LLC resonant converter circuit with an integrated high-frequency transformer and anti-reverse diodes, the circulating current problem between DC 600V and AC 380V generated by the first AC bus being connected to the grid and the second DC bus being connected in parallel can be effectively solved. Furthermore, the inclusion of an LC filter circuit in the DC 600V output circuit effectively addresses the problem of voltage distortion at the far end when DC 600V is supplied in parallel.

[0068] In the several embodiments provided in this invention, it should be understood that the disclosed systems and methods can also be implemented in other ways. The system and method embodiments described above are merely illustrative.

[0069] It should be noted that, in this document, the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0070] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and variations in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection for this invention shall still be determined by the scope defined in the appended claims.

Claims

1. An auxiliary power supply system, comprising: The first DC bus is used to supply power to DC 110V loads; The first AC busbar is used to supply power to AC380V loads; characterized in that the auxiliary power supply system further includes: The second DC bus is used to supply power to DC 600V loads; An auxiliary power supply system has its input terminal connected to the mains voltage and its output terminal connected to the first DC bus, the first AC bus, and the second DC bus; the auxiliary power supply system includes: The first LLC resonant converter circuit is used to convert the voltage into a high-frequency rectangular wave and to provide a stable second voltage after isolating, converting and rectifying the high-frequency rectangular wave. The API inverter circuit is connected to the output of the first LLC resonant converter circuit and is used to convert the second voltage into a PWM voltage. The PWM voltage is filtered and then output as AC380V voltage. A low-voltage power supply circuit is connected between the first LLC resonant converter circuit and the API inverter circuit, and is used to output DC110V voltage after DC / DC isolation conversion and filtering of the second voltage. The second LLC resonant converter circuit is used to convert the voltage into a high-frequency rectangular wave, and to provide a third voltage after isolating, converting and rectifying the high-frequency rectangular wave. An LC filter circuit and a reverse protection diode are provided. The LC filter circuit is connected to the output terminal of the second LLC resonant converter circuit and is used to filter the third voltage. The reverse protection diode is connected to the output terminal of the LC filter circuit, and the filtered third voltage is passed through the reverse protection diode to obtain a DC 600V voltage.

2. The auxiliary power supply system according to claim 1, wherein the auxiliary power supply system further comprises: The pre-charging circuit is connected to the mains voltage. An input filter circuit, connected to the pre-charging circuit, is used to filter the mains voltage; The Boost / Buck circuit, connected to the input filter circuit, is used to convert the filtered grid voltage into a first voltage and output it to the first LLC resonant converter circuit and the second LLC resonant converter circuit.

3. The auxiliary power supply system according to claim 1, characterized in that, Both the first LLC resonant converter circuit and the second LLC resonant converter circuit adopt a full-bridge LLC resonant converter circuit.

4. The auxiliary power supply system according to claim 3, characterized in that, The full-bridge LLC resonant converter circuit includes: a full-bridge IGBT circuit, a high-frequency transformer connected to the input terminal of the full-bridge IGBT circuit, and a full-bridge uncontrolled rectifier circuit connected to the output terminal of the high-frequency transformer.

5. The auxiliary power supply system according to claim 1, characterized in that, The DC600V load includes an air conditioning unit, which uses a DC / AC converter module to convert the DC600V voltage into AC voltage to supply power to the air conditioning unit.

6. The auxiliary power supply system according to claim 1, characterized in that, The auxiliary power supply system also includes an EMI circuit, the input of which is connected to the negative terminal of the anti-reverse diode, and the output of the EMI circuit outputs a DC 600V voltage.

7. The auxiliary power supply system according to claim 6, characterized in that, The output terminal of the EMI circuit is connected to a contactor, which conducts when the DC voltage of its branch reaches DC600V, so that the DC600V voltage is applied to the DC600V load.

8. The auxiliary power supply system according to any one of claims 1 to 7, characterized in that, The auxiliary power supply system is a subway train auxiliary power supply system.

9. The auxiliary power supply system according to claim 1, characterized in that, The low-voltage power supply circuit includes a DC-DC converter circuit and an output filter circuit connected to its back end.

10. The auxiliary power supply system according to claim 1, characterized in that, The API inverter circuit includes an IGBT inverter circuit and a three-phase AC output filter circuit connected to its back end.

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