Modular bidirectional converter and method for switching operating modes thereof

Abstract

The embodiment of the application discloses a kind of modular bidirectional converter and its working mode switching method, wherein the bidirectional converter includes multiple power modules, and the working mode switching method includes: the multiple power modules are based on the control frame of working mode switching, working mode is switched from idle to preparation phase, or from preparation phase to running phase;The running phase includes the back feedback phase when train braking and the traction phase when train travels;The preparation phase is small power running state, and the working direction is consistent with the working direction of the running phase;The multiple power modules are under the action of control device, and working mode is switched from the first running mode of the running phase to the second running mode.Such, multiple power modules are based on the switching of working mode of control frame synchronization, there is no uniform condition of working mode, ensure the consistency and accuracy of working mode switching.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of train regenerative braking energy feedback technology, and particularly relates to a modular bidirectional converter and a working mode switching method thereof. BACKGROUND

[0002] A bidirectional converter is a power electronic converter capable of realizing bidirectional energy flow, and can realize bidirectional conversion of energy between direct current and alternating current or between different direct current voltages. The bidirectional converter is widely used in electric vehicles, energy storage systems, distributed power generation and other fields.

[0003] The bidirectional converter is realized by multiple power modules, but in the process of switching the working mode, the working modes of the multiple power modules are inconsistent, which leads to poor performance of the bidirectional converter, and even causes the bidirectional converter to crash. SUMMARY

[0004] Therefore, the embodiments of the present application provide at least a modular bidirectional converter and a working mode switching method thereof.

[0005] The technical scheme of the embodiments of the present application is as follows:

[0006] On the one hand, the embodiments of the present application provide a working mode switching method of a bidirectional converter, the bidirectional converter comprising multiple power modules, the working mode switching method comprising: switching, by the multiple power modules based on a control frame of working mode switching, the working mode from idle to a preparation phase or from the preparation phase to a running phase; the running phase comprising a feedback phase during train braking and a traction phase during train running; the preparation phase being a small-power running state, and the working direction being consistent with the working direction of the running phase; and switching, by the multiple power modules under the action of a control device, the working mode from a first running mode of the running phase to a second running mode.

[0007] In some embodiments, the switching, by the multiple power modules based on the control frame of working mode switching, of the working mode from idle to the preparation phase or from the preparation phase to the running phase comprises: in a case where the control frame is a first control frame of train braking, switching, by the multiple power modules, the working mode from idle to a feedback preparation phase at a time of occurrence of a next interrupt after a receiving time of the first control frame; the first control frame being triggered when a traction network voltage reaches a feedback preparation value; the preparation phase comprising the feedback preparation phase; and in a case where the control frame is a second control frame of train braking, switching, by the multiple power modules, the working mode from the feedback preparation phase to the feedback phase at a time of occurrence of a next interrupt after a receiving time of the second control frame; the second control frame being triggered when the traction network voltage reaches a feedback start value.

[0008] In some embodiments, the multiple power modules switch the working mode from the idle mode to the preparation phase or from the preparation phase to the running phase based on the control frame of the working mode switching, including: in the case that the control frame is a third control frame of the train starting, the multiple power modules switch the working mode from the idle mode to the traction preparation phase at the occurrence time of the next interrupt after the receiving time of the third control frame; the third control frame is triggered when the traction network voltage reaches the traction preparation value; the preparation phase includes the traction preparation phase; in the case that the control frame is a fourth control frame of the train starting, the multiple power modules switch the working mode from the traction preparation phase to the traction phase at the occurrence time of the next interrupt after the receiving time of the fourth control frame; the fourth control frame is triggered when the traction network voltage reaches the traction starting value.

[0009] In some embodiments, the multiple power modules switch the working mode from the first running mode to the second running mode of the running phase under the action of the control device, including: the multiple power modules output the bus current of the current sharing under the action of the control device, and synchronously switch the working mode from the feedback constant voltage mode to the feedback limited power mode of the running phase when the bus current reaches the first current threshold; the first running mode is the feedback constant voltage mode, and the second running mode is the feedback limited power mode.

[0010] In some embodiments, the multiple power modules switch the working mode from the first running mode to the second running mode of the running phase under the action of the control device, including: the multiple power modules output the bus current of the current sharing under the action of the control device, and synchronously switch the working mode from the traction constant voltage mode to the traction limited power mode of the running phase when the bus current reaches the second current threshold; the first running mode is the traction constant voltage mode, and the second running mode is the traction limited power mode.

[0011] In some embodiments, the multiple power modules determine the master weight value based on the power module state value in the bidirectional converter, the bus sampling state value, the host flag state value, the power module online flag state value, the power module address and the weight value corresponding to each state value one by one, and elect the host based on the master weight value; the remaining power modules in the multiple power modules except the host are slaves; the host sends the control frame to the multiple slaves; the host and the multiple slaves synchronously switch the working mode from the idle mode to the preparation phase or from the preparation phase to the running phase at the occurrence time of the interrupt after the receiving time of the control frame.

[0012] In some embodiments, the working mode switching method further includes: the host sends the same control frame to the multiple slaves twice through two network buses, so that the multiple slaves perform synchronous operation based on one of the control frames.

[0013] In some embodiments, the weight of the power module state value, the weight of the bus sampling state value, the weight of the host flag state value, and the weight of the power module online flag state value are sequentially decreased, and the weight of the power module online flag state value is related to the power module address.

[0014] In another aspect, the embodiments of the present application provide a bidirectional converter, which comprises a plurality of power modules; a direct current end of the power module is connected with a direct current traction network, and an alternating current end of the power module is connected with an alternating current network; the plurality of power modules are configured to switch the working mode from idle to a preparation phase or from the preparation phase to a running phase based on a control frame of the working mode switching; the running phase comprises a feedback phase during train braking and a traction phase during train running; the preparation phase is a small power running state, and the working direction is consistent with that of the running phase; the plurality of power modules are switched from a first running mode of the running phase to a second running mode under the action of a control device.

[0015] In some embodiments, the power module comprises a control device; the control device comprises a current sharing loop, a power limiting loop, a bus voltage loop, and a modulation device; the current sharing loop is connected to a current sampling point of the power module, the bus voltage loop is connected to a voltage sampling point of the power module, the outputs of the current sharing loop and the bus voltage loop are connected to the input of the power limiting loop, and the output of the power limiting loop is connected to the modulation device.

[0016] In the embodiments of the present application, the control frame of the working mode switching is synchronously sent to the plurality of power modules, and the plurality of power modules receive the control frame at the same time, so that the plurality of power modules can synchronously switch the working mode from idle to the preparation phase or from the preparation phase to the running phase based on the control frame of the working mode switching, and there is no inconsistency in the phases. The preparation phase is a small power running state, and the small power running phase refers to slowly releasing the power to a preparation value so as to quickly enter the running phase; the working direction of the preparation phase is consistent with that of the running phase, which means that, in the case that the running phase comprises the feedback phase during train braking and the traction phase during train running, the preparation phase correspondingly comprises the preparation phase during train braking and the preparation phase during train running; in this way, the plurality of power modules can synchronously switch from the preparation phase during train braking to the feedback phase during train braking based on the control frame, and synchronously switch from the preparation phase during train running to the traction phase during train running based on the control frame. The plurality of power modules can synchronously switch the working mode from the first running mode of the running phase to the second running mode under the action of the control device, and there is no inconsistency in the running modes. Therefore, the synchronization switching of different phases is based on the control frame, and the synchronization switching of different modes in the same phase is based on the control device, so that there is no inconsistency in the working modes in the whole process, and the consistency and accuracy of the switching are ensured.

[0017] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, not limiting the technical solutions of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and serve to explain the technical solutions of the present application, together with the description.

[0019] Figure 1 An implementation flowchart of a working mode switching method of a bidirectional converter provided for an embodiment of the present application Figure 1 ;

[0020] Figure 2 An implementation flowchart of a working mode switching method of a bidirectional converter provided for an embodiment of the present application Figure 2 ;

[0021] Figure 3 An implementation flowchart of a working mode switching method of a bidirectional converter provided for an embodiment of the present application Figure 3 ;

[0022] Figure 4 An implementation flowchart of a working mode switching method of a bidirectional converter provided for an embodiment of the present application Figure 4 ;

[0023] Figure 5 A constituent structure diagram of a bidirectional converter provided for an embodiment of the present application

[0024] Figure 6 A constituent structure diagram of a control device in a bidirectional converter provided for an embodiment of the present application

[0025] Figure 7 A constituent structure diagram of a phase-locked system provided for an embodiment of the present application

[0026] Figure 8 A curve diagram of a bidirectional converter in a feedback mode provided for an embodiment of the present application. DETAILED DESCRIPTION

[0027] In order to make the purposes, technical solutions and advantages of the present application clearer, the technical solutions of the present application are further described in detail below in combination with the drawings and embodiments, and the described embodiments should not be regarded as limiting the present application, and all other embodiments obtained by those skilled in the art without making creative efforts fall within the scope of protection of the present application.

[0028] In the following description, reference is made to "some embodiments", which describe a subset of all possible embodiments, but it is to be understood that "some embodiments" can be the same subset or different subsets as each other and as other subsets of all possible embodiments, and can be combined with each other and with other subsets of all possible embodiments without contradiction.

[0029] The terms "first / second / third" are only to distinguish similar objects, and do not represent a specific order of the objects. It is understood that the "first / second / third" can be interchanged in a specific order or sequence as allowed, so that the embodiments of the application described herein can be implemented in an order other than that illustrated or described herein.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing the present application only and is not intended to be limiting of the present application.

[0031] Currently, the power supply system of rail transit adopts a unidirectional rectifier device to convert electrical energy from three-phase alternating current into direct current to provide a direct current power supply for rail transit vehicles. In order to realize the bidirectional flow of energy between the direct current side and the alternating current side of the rail transit power supply system and provide stable direct current catenary voltage, a regenerative bidirectional traction power supply device is introduced into the rail transit power supply system. The alternating current side of the regenerative bidirectional traction power supply device is connected to an alternating current power grid, and the direct current side is connected to a direct current traction network. When the rail transit vehicle is in a traction state, the power supply device works in a rectification state to convert alternating current from the alternating current power grid into direct current to supply power to the direct current traction network. When the rail transit vehicle is in a braking state, the power supply device works in an inversion state to convert direct current from the direct current traction network into alternating current to feed back to the alternating current power grid.

[0032] The embodiments of the present application provide a working mode switching method of a bidirectional converter, as shown in Figure 1 The method comprises the following steps 101 to 102:

[0033] Step 101, the plurality of power modules switch the working mode from idle to preparation phase or from preparation phase to running phase based on the control frame of working mode switching; the running phase comprises a feedback phase when the train brakes and a traction phase when the train travels; the preparation phase is a small power running state, and the working direction is consistent with the working direction of the running phase.

[0034] The bidirectional converter refers to one example of the above-mentioned feedable bidirectional traction power supply device. Illustratively, when the train is running, the bidirectional converter operates in a rectification mode to absorb power from the AC power grid and rectify it into DC power to provide stable traction power for the train. When the train is braking, the bidirectional converter switches to an inversion mode to invert the regenerative power generated during the braking of the train back to the AC power grid, thereby achieving energy recycling and reuse. The bidirectional converter is used to regulate the power of the power distribution network (AC power grid and DC power grid).

[0035] The bidirectional converter includes a plurality of power modules. The power modules are used to realize bidirectional conversion between AC and DC. Each power module can include a conversion circuit, which can be an active neutral point clamped (ANPC) circuit. Each power module can include a plurality of devices such as switching devices (Sa, Sb, Sc), inductors (L), and flying capacitors (F).

[0036] In some embodiments, the plurality of power modules can communicate through a synchronous controller area network (CAN) bus.

[0037] The control frame is used to indicate that the plurality of power modules synchronously switch the working mode. The working modes of the bidirectional converter include idle, preparation phase, and running phase. The running phase includes constant voltage mode and limited power mode. Since the running phase includes the feedback phase when the train is braking and the traction phase when the train is running, the running phase (feedback phase) also includes feedback constant voltage mode and feedback limited power mode when the train is braking; the running phase (traction phase) also includes traction constant voltage mode and traction limited power mode when the train is running.

[0038] The preparation phase is a small power running state and the working direction is consistent with the working direction of the running phase. This means that when the train is braking, the preparation phase is the feedback preparation phase and the running phase is the feedback phase; when the train is running, the preparation phase is the traction preparation phase and the running phase is the traction phase.

[0039] The bidirectional converter is idle, indicating that the bidirectional converter is not performing energy conversion or transmission. The bidirectional converter is in the preparation phase, indicating that the bidirectional converter enters a small power running state, at which time the power is slowly released to the preparation value in order to quickly enter the running phase. The bidirectional converter is in the running phase, indicating that the bidirectional converter enters a large power running state, at which time the power is slowly released to the limited power and runs at the limited power.

[0040] In some embodiments, the plurality of power modules can receive the control frame for switching the working mode through the synchronous CAN bus.

[0041] In some embodiments, the control frame can be sent by any of the plurality of power modules, can be sent by a master selected from the plurality of power modules, or can be sent by a control module other than the plurality of power modules, and the embodiments of the present application do not limit this.

[0042] In some embodiments, the control frame is sent when a switching condition is met.

[0043] In some embodiments, the switching condition can include a switching condition of a preparation phase and a switching condition of a running phase. In this case, when the switching condition of the preparation phase is met, a control frame for indicating entering the preparation phase is sent to the plurality of power modules; and when the switching condition of the running phase is met, a control frame for indicating entering the running phase is sent to the plurality of power modules.

[0044] In some embodiments, the preparation phase includes a feedback preparation phase and a traction preparation phase, and then the switching condition of the preparation phase includes a switching condition of the feedback preparation phase and a switching condition of the traction preparation phase. In this case, when the switching condition of the feedback preparation phase is met, a control frame for indicating entering the feedback preparation phase is sent to the plurality of power modules; and when the switching condition of the traction preparation phase is met, a control frame for indicating entering the traction preparation phase is sent to the plurality of power modules.

[0045] In some embodiments, the running phase includes a feedback constant voltage mode, a feedback limited power mode, a traction constant voltage mode and a traction limited power mode, and then the switching condition of the running phase includes a switching condition of the feedback constant voltage mode, a switching condition of the feedback limited power mode, a switching condition of the traction constant voltage mode and a switching condition of the traction limited power mode. In this case, when the switching condition of the feedback constant voltage mode is met, a control frame for indicating entering the feedback constant voltage mode is sent to the plurality of power modules; when the switching condition of the feedback limited power mode is met, a control frame for indicating entering the feedback limited power mode is sent to the plurality of power modules; when the switching condition of the traction constant voltage mode is met, a control frame for indicating entering the traction constant voltage mode is sent to the plurality of power modules; and when the switching condition of the traction limited power mode is met, a control frame for indicating entering the traction limited power mode is sent to the plurality of power modules.

[0046] In some embodiments, the plurality of power modules can switch the working mode from the idle to the preparation phase or from the preparation phase to the running phase at the occurrence time of the i th interrupt after the time of the control frame, where i is a positive integer. For example, i can be 1, i.e., the working mode is switched at the occurrence time of the first interrupt after the time of the control frame, i.e., the working mode is switched at the occurrence time of the next interrupt after the time of the control frame.

[0047] Step 102, the plurality of power modules, under the action of the control device, switch the working mode from the first operation mode of the operation stage to the second operation mode.

[0048] The control device is used to control the plurality of power modules to synchronously switch different modes of the same stage. Exemplarily, the control device can be a control loop.

[0049] In some embodiments, if the operation stage is a feedback stage, the first operation mode can be a feedback constant voltage mode, and the second operation mode can be a feedback limited power stage; at this time, the plurality of power modules, under the action of the control device, switch the working mode from the feedback constant voltage mode of the feedback stage to the feedback limited power mode. Alternatively, the first operation mode can be a feedback limited power mode, and the second operation mode can be a feedback constant voltage stage; at this time, the plurality of power modules, under the action of the control device, switch the working mode from the feedback limited power mode of the feedback stage to the feedback constant voltage mode.

[0050] In some embodiments, if the operation stage is a traction stage, the first operation mode can be a traction constant voltage mode, and the second operation mode can be a traction limited power stage; at this time, the plurality of power modules, under the action of the control device, switch the working mode from the traction constant voltage mode of the traction stage to the traction limited power mode. Alternatively, the first operation mode can be a traction limited power mode, and the second operation mode can be a traction constant voltage stage; at this time, the plurality of power modules, under the action of the control device, switch the working mode from the traction limited power mode of the traction stage to the traction constant voltage mode.

[0051] In the embodiments of the present application, the control frame for switching the working mode is synchronously sent to the plurality of power modules, and the plurality of power modules receive the control frame at the same time. Therefore, the plurality of power modules can synchronously switch the working mode from the idle mode to the preparation phase or from the preparation phase to the running phase based on the control frame for switching the working mode, and there is no inconsistent phase. The preparation phase is a small power running state, and the small power running phase refers to slowly releasing the power to the preparation value so as to quickly enter the running phase. The working direction of the preparation phase is consistent with the working direction of the running phase, which means that the preparation phase corresponds to the preparation phase during train braking and the preparation phase during train running in the case that the running phase includes the feedback phase during train braking and the traction phase during train running. In this way, the plurality of power modules can synchronously switch from the preparation phase during train braking to the feedback phase during train braking based on the control frame during train braking, and the plurality of power modules can synchronously switch from the preparation phase during train running to the traction phase during train running based on the control frame during train running. The plurality of power modules can synchronously switch the working mode from the first running mode of the running phase to the second running mode of the running phase under the action of the control device, and there is no inconsistent running mode. Therefore, the different phases are synchronously switched based on the control frame, and the different modes in the same phase are synchronously switched based on the control device, and there is no inconsistent working mode in the whole process, which ensures the consistency and accuracy of the switching.

[0052] The embodiments of the present application provide a working mode switching method of a bidirectional converter, which can be executed during train braking, as shown in the following formula (1): Figure 2 The method includes the following steps 201 to 203.

[0053] In step 201, in the case that the control frame is a first control frame for train braking, the plurality of power modules switch the working mode from the idle mode to the feedback preparation phase at the occurrence time of the next interrupt after the receiving time of the first control frame. The first control frame is triggered when the traction network voltage reaches a feedback preparation value. The preparation phase includes the feedback preparation phase.

[0054] The first control frame is a control frame for indicating the entry into the feedback preparation phase. The feedback preparation value is used to determine the timing of the entry into the feedback preparation phase. At this time, the condition for the entry into the feedback preparation phase is that the traction network voltage reaches the feedback preparation value. Exemplarily, the feedback preparation value can be set to 1695V (volt), but is not limited thereto, and can be set to other values, which can be set according to actual business requirements.

[0055] In some embodiments, the host sends the first control frame to the plurality of power modules when the traction network voltage reaches the feedback preparation value, and the plurality of power modules switch the working mode from the idle mode to the feedback preparation phase at the occurrence time of the next interrupt after receiving the first control frame.

[0056] Step 202, in the case that the control frame is a second control frame for train braking, the plurality of power modules switch the working mode from the feedback preparation phase to a feedback phase at the occurrence time of the next interrupt after the receiving time of the second control frame; the second control frame is triggered when the traction network voltage reaches a feedback start value.

[0057] Here, the above steps 201 to 202 correspond to the aforementioned step 101, and in implementation, the specific embodiments of the aforementioned step 101 can be referred to.

[0058] The second control frame is a control frame for indicating entering the feedback phase. The feedback start value is used to determine the timing of entering the feedback phase, and at this time, the condition for entering the feedback phase is that the traction network voltage reaches the feedback start value. Exemplarily, the feedback start value can be set to 1730V, but is not limited thereto, and can also be set to other values, which can be set according to actual business needs.

[0059] In some embodiments, the host sends the second control frame to the plurality of power modules when the traction network voltage reaches the feedback start value, and the plurality of power modules switch the working mode from the feedback preparation phase to a first operating mode of the feedback phase at the occurrence time of the next interrupt after receiving the second control frame.

[0060] Step 203, under the action of the control device, the plurality of power modules output a current-sharing bus current, and when the bus current reaches a first current threshold, the working mode is synchronously switched from the feedback constant voltage mode of the operating phase to the feedback limited power mode; the first operating mode is the feedback constant voltage mode, and the second operating mode is the feedback limited power mode.

[0061] The feedback constant voltage phase refers to when the train decelerates or brakes, the traction motor operates as a generator to convert the kinetic energy of the train into electrical energy, and feeds back this part of electrical energy to the DC traction network at a constant voltage. The feedback limited power phase refers to when the power of the traction network approaches the maximum value, the electrical energy is fed back at a constant power to avoid overvoltage of the power supply network.

[0062] The first current threshold is used to determine the timing of entering the feedback limited power phase. Since the plurality of power modules all switch the working mode from the feedback constant voltage mode to the feedback limited power mode when the bus current reaches the first current threshold, even without a control frame, the plurality of power modules can also be synchronized to switch from the feedback constant voltage mode to the feedback limited power mode.

[0063] Since the bus voltage output by the plurality of power modules is consistent, power = current x voltage, therefore, according to the switching timing of different modes of the feedback stage determined by the bus current after current sharing, it is equivalent to determining the switching timing of different modes of the feedback stage according to the power output by the plurality of power modules. The bus current reaching the first current threshold value is equivalent to the bus power reaching the first power threshold value.

[0064] In the embodiments of the present application, the first control frame is triggered when the traction network voltage reaches the feedback preparation value, so that the plurality of power modules synchronously switch the working mode from idle to the feedback preparation stage at the occurrence time of the next interrupt after the receiving time of the first control frame; the second control frame is triggered when the traction network voltage reaches the feedback start value, so that the plurality of power modules synchronously switch the working mode from the feedback preparation stage to the feedback constant voltage mode of the feedback stage at the occurrence time of the next interrupt after the receiving time of the second control frame, and synchronously switch the working mode from the feedback constant voltage stage to the feedback power limiting stage when the bus current reaches the first current threshold value. In this way, the plurality of power modules synchronously switch different stages at the occurrence time of the next interrupt after the receiving time of the first control frame or the second control frame, and synchronously switch different modes of the same stage under the action of the control device when the bus current reaches the first current threshold value. During the entire braking process, there is no situation that the working mode is not uniform, ensuring the consistency and accuracy of the switching.

[0065] The embodiments of the present application provide a working mode switching method of a bidirectional converter, which can be executed when the train is running, as shown in Figure 3 The method comprises the following steps 301 to 303:

[0066] In step 301, in the case that the control frame is a third control frame for train starting, the plurality of power modules switch the working mode from idle to the traction preparation stage at the occurrence time of the next interrupt after the receiving time of the third control frame; the third control frame is triggered when the traction network voltage reaches a traction preparation value; and the preparation stage comprises the traction preparation stage.

[0067] The third control frame is a control frame for indicating entering the traction preparation stage. The traction preparation value is used to determine the timing of entering the traction mode, and at this time, the condition for entering the traction mode is that the traction network voltage reaches the traction preparation value. Exemplarily, the traction preparation value can be set to 1600V, but is not limited thereto, and can be set to other values, which can be set according to actual business requirements.

[0068] In some embodiments, the host sends the third control frame to the plurality of power modules when the traction network voltage reaches the traction preparation value, and the plurality of power modules switch the working mode from idle to the traction preparation stage at the occurrence time of the next interrupt after receiving the third control frame.

[0069] Step 302, in the case that the control frame is a fourth control frame for train starting, the plurality of power modules switch the working mode from the traction preparation phase to a traction phase at the occurrence time of the next interrupt after the receiving time of the fourth control frame; the fourth control frame is triggered when the traction network voltage reaches a traction starting value.

[0070] Here, the above steps 301 to 302 correspond to the aforementioned step 101, and in implementation, the specific embodiments of the aforementioned step 101 can be referred to, and the specific embodiments of the aforementioned steps 201 to 202 can also be referred to.

[0071] The fourth control frame is a control frame for indicating entering the traction phase. The traction starting value is used to judge the timing of entering the traction phase, and at this time, the condition for entering the traction phase is that the traction network voltage reaches the traction starting value. Exemplarily, the traction starting value can be set to 1580V, but is not limited thereto, and can also be set to other values, which can be set according to actual business needs.

[0072] In some embodiments, the host sends a fourth control frame to the plurality of power modules when the traction network voltage reaches the traction starting value, and the plurality of power modules switch the working mode from the traction preparation phase to a first running mode of the traction phase at the occurrence time of the next interrupt after receiving the fourth control frame.

[0073] Step 303, under the action of the control device, the plurality of power modules output a current-sharing bus current, and synchronously switch the working mode from the traction constant voltage mode of the running phase to a traction limited power mode when the bus current reaches a second current threshold; the first running mode is the traction constant voltage mode, and the second running mode is the traction limited power mode.

[0074] Here, the above step 303 corresponds to the aforementioned step 102, and in implementation, the specific embodiments of the aforementioned step 102 can be referred to, and the specific embodiments of the aforementioned step 203 can also be referred to.

[0075] The traction constant voltage phase refers to that when the train starts from the platform, the traction system enters the constant voltage phase to provide a large traction force to accelerate the train quickly, and at this time, the voltage of the traction motor remains constant to ensure that the motor provides sufficient torque at low speed.

[0076] The traction limited power phase refers to that when the train approaches the target speed, the traction system switches to the limited power phase to limit the traction power within a safe range, and at this time, the power of the traction motor remains constant to avoid overload and reduce energy waste.

[0077] The second current threshold is used to determine the timing of entering the traction limited power stage. Since multiple slaves switch the working mode from the traction constant voltage stage to the traction limited power stage at the same time when the bus current reaches the second current threshold, the multiple slaves can switch from the traction constant voltage stage to the traction limited power stage at the same time even without the control frame.

[0078] Since the bus voltage output by the multiple power modules is consistent, power = current x voltage, according to the bus current after current sharing to determine the switching timing of different modes in the traction stage is equivalent to determining the switching timing of different modes in the traction stage according to the power output by the multiple power modules. The bus current reaching the second current threshold is equivalent to the bus power reaching the second power threshold.

[0079] In the embodiment of the application, the third control frame is triggered when the traction network voltage reaches the traction preparation value, so that the multiple power modules synchronously switch the working mode from idle to the traction preparation stage at the occurrence time of the next interrupt after the receiving time of the third control frame; the tenth control frame is triggered when the traction network voltage reaches the traction start value, so that the multiple power modules synchronously switch the working mode from the traction preparation stage to the traction constant voltage mode of the traction stage at the occurrence time of the next interrupt after the receiving time of the fourth control frame, and synchronously switch the working mode from the traction constant voltage stage to the traction limited power stage when the bus current reaches the second current threshold. In this way, the multiple power modules synchronously switch different stages at the occurrence time of the next interrupt after the receiving time of the third control frame or the fourth control frame, and synchronously switch different modes of the same stage under the action of the control device when the bus current reaches the second current threshold. There is no situation that the working modes are not uniform in the whole driving process, which ensures the consistency and accuracy of the switching.

[0080] The embodiment of the application provides a working mode switching method of a bidirectional converter, as shown in Figure 4 The method comprises the following steps 401 to 403:

[0081] Step 401, the master sends a control frame to multiple slaves.

[0082] In some embodiments, the multiple power modules determine a master weight value based on a power module state value in the bidirectional converter, a bus sampling state value, a master flag state value, a power module online flag state value, a power module address and a weight value corresponding to each state value one by one, and elect a master based on the master weight value; the rest of the power modules in the multiple power modules are slaves except the master.

[0083] The power module state value is used to represent whether the corresponding power module is in shutdown protection. For example, as shown in Table 1 below, if the power module does not have a fault leading to shutdown protection, it is considered to be in normal operation, and the power module state value can be 1; if the power module is in shutdown protection, the power module state value can be 0.

[0084] The bus sampling state value is used to represent whether the bus sampling is abnormal. The working mode control, the midpoint balance ring, and the ripple suppression ring control all involve bus sampling, and are relatively important, so the bus sampling of the host computer needs to be ensured to be normal to ensure the effectiveness of the host computer sampling. For example, as shown in Table 1 below, if the bus sampling is normal, the bus sampling state value can be 1; if the bus sampling is abnormal, the bus sampling state value can be 0.

[0085] The host flag state value is used to represent whether the corresponding power module is a host. For example, as shown in Table 1 below, if the power module is a host, the host flag state value is 1; if the power module is a slave, the host flag state value is 0. It should be noted that in the same state, the host is maintained as much as possible to reduce the host switching.

[0086] The power module online flag state value is used to represent whether the power module is offline. For example, as shown in Table 1, if the power module is online, the power module online flag state value is 1; if the power module is offline, the power module online flag state value is 0. The power module address is used to represent the position of the power module.

[0087] Table 1

[0088]

[0089] In some embodiments, whether the bus sampling is abnormal can be determined based on a size relationship between a difference between the DC bus voltage and the system DC bus voltage median value within the filtering duration and the first voltage threshold.

[0090] In some embodiments, the filtering duration can be 5s (seconds), and the first voltage threshold can be 40V. At this time, if the difference between the DC bus voltage and the system DC bus voltage median value is greater than the first voltage threshold (40V) and the filtering duration reaches 5s, it is determined that the bus sampling is abnormal.

[0091] In some embodiments, whether the bus sampling is normal can be determined based on a size relationship between a difference between the DC bus voltage and the system DC bus voltage median value within the filtering duration and the second voltage threshold.

[0092] In some embodiments, the filtering duration can be 5s (seconds), the first voltage threshold can be 30V, and if the difference between the DC bus voltage and the median value of the system DC bus voltage is less than the second voltage threshold (30V) and the filtering duration reaches 5s, it is determined that the bus sampling is normal.

[0093] In some embodiments, the weight of the power module state value can be 256, the weight of the bus sampling state value can be 128, the weight of the host flag state value can be 64, and the weight of the power module online flag state value can be 32-power module address. At this time, the calculation formula of the power module master weight value can be: power module master weight value = [power module state value * 256 + bus sampling state value * 128 + host flag state value * 64 + (32-power module address)] * power module online flag state value.

[0094] In some embodiments, the weight of the power module state value, the weight of the bus sampling state value, the weight of the host flag state value, and the weight of the power module online flag state value are sequentially decreased, and the weight of the power module online flag state value is related to the power module address.

[0095] For example, the power module state value has the highest priority, and its weight can be set to 256. The bus sampling state value has the second highest priority, and its weight can be set to 128. The host flag state value has the third highest priority, and its weight can be set to 64. The power module online flag state value has the lowest priority, and its weight can be set to 32-power module address.

[0096] In some embodiments, the weight of the power module online flag state value is negatively related to the address of the power module, and when the states of the plurality of power modules are consistent and there is no host, the power module with the smallest address becomes the host.

[0097] It should be noted that there is no host at the beginning, and the host is generated through master competition after the power module is powered on. When the states of all power modules are consistent and there is no host, the master weight value of the power module with the smallest address is the largest under the action of (32-power module address), and it will become the host. The data used by the master weight value (data in Table 1) can be shared through the CAN bus.

[0098] In some embodiments, the master sends the same control frame to the plurality of slaves twice through two network buses, so that the plurality of slaves perform synchronous operations based on one of the control frames.

[0099] In some embodiments, the network bus can be a CAN bus, and the host sends the same control frame to the plurality of slaves twice in the same clock cycle through two CAN buses in succession, so that the plurality of slaves operate synchronously based on one of the control frames.

[0100] It should be noted that the transmission of the control frame through two parallel CAN buses can ensure that the system will not produce abnormality due to loop current when a single CAN bus fails, and the error at the same time is avoided through the staggered control (sending in succession in the same clock cycle), and the synchronization accuracy is improved.

[0101] Step 402, the host and the plurality of slaves switch the working mode from idle to preparation phase or from preparation phase to running phase at the occurrence time of the interrupt after the arrival of the receiving time of the control frame.

[0102] Here, step 402 corresponds to the aforementioned steps 101, steps 201 to 202, steps 301 to 302, and in implementation, the specific embodiments of the aforementioned steps 101, steps 201 to 202, steps 301 to 302 can be referred to.

[0103] Step 403, the host and the plurality of slaves switch the working mode from the first running mode of the running phase to the second running mode under the action of the control device.

[0104] Here, step 403 corresponds to the aforementioned steps 102, step 203, step 303, and in implementation, the specific embodiments of the aforementioned steps 101, step 203, step 303 can be referred to.

[0105] In this embodiment, a master power module is selected from multiple power modules, and the remaining power modules are designated as slave power modules. The master power module sends control frames to the slave power modules, enabling the master and slave power modules to synchronously switch their operating modes from idle to preparation phase or from preparation phase to operation phase at the time of the next interruption following the reception time of the control frame, thus avoiding any inconsistency in the phases. Since the preparation phase is a low-power operation state and its operating direction is consistent with that of the operation phase, the operation phase includes a feedback phase during train braking and a traction phase during train travel. Therefore, the master and slave power modules can synchronously enter the feedback phase or traction phase based on the control frame. Similarly, since the preparation phase is a low-power operation state and its operating direction is consistent with that of the operation phase, the master and slave power modules can synchronously switch from the preparation phase during train braking to the feedback phase or from the preparation phase during train travel to the traction phase based on the control frame. Under the control of the control device, the master and slave power modules can synchronously switch their operating modes from the first operation mode to the second operation mode of the operation phase, avoiding any inconsistency in the operating modes. Thus, by using control frames to synchronously switch between different stages and control devices to synchronously switch between different modes within the same stage, there will be no inconsistency in the working modes throughout the process, ensuring the consistency and accuracy of the switching.

[0106] This application provides a bidirectional converter, which includes multiple power modules; the DC terminal of each power module is connected to a DC traction network, and the AC terminal of each power module is connected to an AC power grid.

[0107] The plurality of power modules are configured to switch the operating mode from idle to preparation stage or from preparation stage to operation stage based on the control frame of the operating mode switching; the operation stage includes the feedback stage when the train brakes and the traction stage when the train is moving; the preparation stage is a low-power operation state and the working direction is the same as the working direction of the operation stage.

[0108] Under the control of the control device, the multiple power modules switch their operating modes from the first operating mode to the second operating mode during the operation phase.

[0109] like Figure 5 As shown, the bidirectional converter can be connected between the DC traction network and the AC power grid, and a transformer can be connected between the bidirectional converter and the AC power grid. The bidirectional converter can include multiple power modules; only power modules 51 and 52 are shown in the figure for illustration, but in practice, multiple power modules can be compatible. The system needs to generate a master unit through a contention process to achieve parallel operation functions such as carrier synchronization, phase synchronization, current synchronization sampling, midpoint balancing loop control, ripple suppression loop control, and operating mode control.

[0110] In some embodiments, the bidirectional converter includes a control device; such as Figure 6 As shown, the control device includes a current sharing loop, a power limiting loop, a bus voltage loop, and a modulation device; the current sharing loop is connected to the current sampling point of the power module, the bus voltage loop is connected to the voltage sampling point of the power module, the output terminals of the current sharing loop and the bus voltage loop are connected to the input terminal of the power limiting loop, and the output terminal of the power limiting loop is connected to the modulation device.

[0111] For example, see Figure 6 The output current of multiple power modules is shared using a current sharing loop to obtain the shared bus current. Bus voltage is obtained through the bus voltage loop. The system determines whether the bus power (bus current * bus voltage) has reached a power threshold using a power limiting loop, and outputs a signal to multiple power modules via a modulation device. Specifically, if the bus power reaches the first power threshold, a signal is output to control multiple power modules to synchronously enter the feedback power limiting stage; if the bus power reaches the second power threshold, a signal is output to control multiple power modules to synchronously enter the traction power limiting stage.

[0112] It should be noted that multiple power modules can correspond to the same control device, or each of the multiple power modules can correspond to a control device.

[0113] In some embodiments, the control device is configured to control multiple power modules to simultaneously switch their operating modes from the feedback constant voltage mode of the operation phase to the feedback power limiting mode when the bus current reaches a first current threshold; and to control multiple power modules to simultaneously switch their operating modes from the traction constant voltage mode of the operation phase to the traction power limiting mode when the bus current reaches a second current threshold.

[0114] Furthermore, the modular bidirectional converter and its working mode switching method provided in this application embodiment are not only applicable to rail transit traction scenarios, but also to other scenarios with bidirectional working conditions.

[0115] The following describes the application of the bidirectional converter operating mode switching method provided in this application embodiment in a real-world scenario.

[0116] like Figure 7 As shown in the figure, this application provides a phase-locked loop (PLL) system. The PLL system includes a monitoring host, a system control card, and multiple power control cards. The monitoring host can detect the operating status of the system control card and the multiple power control cards via a monitoring CAN bus. The system control card can achieve synchronous control of the multiple power control cards via a synchronization CAN bus, and the multiple power module control cards can achieve data interaction between power modules via a current-sharing CAN bus.

[0117] In some embodiments, the monitoring host can be connected to a 10-inch touch screen so that the user can know the running status of the device. The monitoring host can also be connected to the line network traction power monitoring system and the power supervisory control and data acquisition (PSCADA). The power supervisory control and data acquisition (PSCADA) is an automatic system for real-time monitoring and control of the operation of the power system. The power supervisory control and data acquisition (PSCADA) realizes centralized monitoring, automatic control and data analysis of the power system by collecting the operation data and state information of the power equipment, analyzing and processing these data, thereby improving the operation efficiency, reliability and safety of the power system. The line network traction power monitoring system is an automatic monitoring system specially used for the traction power supply system of railways and urban rail transit.

[0118] The system control card includes multiple interfaces with different functions. For example, the system control card can include ADC, CANB, GPIO, SCIB, SPIA, EMIF, PWM, GPIO, SPIB, CANA, etc. Among them, the analog-to-digital converter (ADC) is used to convert analog signals into digital signals. The controller area network B (CANB) is used to collect the status of each control card. The general purpose input / output (GPIO) is used for simple digital signal control and state detection, and is also used to connect the short-circuit power module. The serial communication interface B (SCIB) is used for communication with the debugging platform. The serial peripheral interface A (SPIA) is used to connect the external flash memory. The external memory interface (EMIF) is used to connect the external static random access memory (SRAM). The pulse width modulation (PWM) is used to connect the slow-start power module. The serial peripheral interface B (SPIB) is used to balance the current of multiple power control cards. The controller area network A (CANA) is used to synchronize multiple power control cards. Similarly, the power control card can also include ADC, CANB, GPIO, SCIB, SPIA, EMIF, PWM, GPIO, SPIB, CANA, etc.

[0119] As shown in Figure 5 The bidirectional converter can be connected between the DC bus and the power grid, and a transformer can be connected between the bidirectional converter and the power grid. The bidirectional converter can include multiple power modules, and only two power modules are shown in the figure as an example, and multiple power modules can be actually compatible. The system needs to generate a master through master competition to realize functions such as carrier synchronization, phase synchronization, current synchronous sampling, midpoint balance ring control, ripple suppression ring control, and working mode control.

[0120] Among them, the master competition formula is as follows: power module master value = [power module state value * 256 + bus sampling state value * 128 + master flag state value * 64 + (32-power module address)] * power module online flag state value.

[0121] When the working mode switching occurs, the working mode control information (corresponding to the control frame) sent by the host on the synchronous CAN bus changes; in order to ensure that all power modules start to release the power limit at the same time, all power modules uniformly start to switch the mode and release the power limit at the next time of entering the interruption (the interruption is configured in the program, and the interruption is entered once in a fixed period (for example, 3 kHz)). Since all power modules follow the working mode control information of the host, they only work together in the feedback or traction phase, and the working mode of the power modules is inconsistent.

[0122] Taking the switching from the standby to the feedback phase as an example, the starting moment diagram is shown in FIG. 1, which includes a small-power feedback phase (corresponding to the feedback preparation phase) and a large-power feedback phase (corresponding to the feedback phase). Figure 8

[0123] (1) At the next interruption of receiving the control frame 1 by the slave, all power modules are switched to the small-power feedback state together. In the small-power feedback state, the power limit is slowly released, and then works in the small-power limit state, at which time all power modules work in the power limit state, and there is no need to control the current sharing.

[0124] (2) At the next interruption of receiving the control frame 2 by the slave, all power modules are switched to the large-power feedback state together. At the beginning of the large-power feedback state, the power limit is slowly released, and all power modules work in the power limit state; when the power limit value exceeds the train braking power, all power modules enter the constant voltage control state, at which time the current sharing ring starts to work.

[0125] It should be understood that the "one embodiment" or "an embodiment" mentioned throughout the specification means that the specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present application. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily mean the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in various embodiments of the present application, the size of the sequence number of each step / process does not mean the order of execution, and the execution order of each step / process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application. The sequence number of the above embodiments of the present application is only for description, not representing the advantages and disadvantages of the embodiments.

[0126] ​It should be noted that, in the present document, the terms "comprising", "comprises" or any other variant thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element preceded by "comprises a" does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0127] In several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The above-described device embodiments are merely illustrative. For example, the division of the units is merely a logical functional division. In actual implementation, another division manner can be used, such as: a plurality of units or components can be combined, or can be integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the displayed or discussed components can be indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0128] The units described above as separate components can or can not be physically separate, and the components shown as units can or can not be physical units; they can be located in one place or distributed on multiple network units; and some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment. In addition, each functional unit in each embodiment of the present application can be integrated into a processing unit, or each unit can be a separate unit, or two or more units can be integrated into one unit; the integrated unit can be realized in the form of hardware or in the form of hardware plus software functional unit.

[0129] The above is only an embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed in the present application, which should be covered within the protection scope of the present application.

Claims

1. A method of switching operating modes of a bidirectional converter, characterized in that, The bidirectional converter comprises a plurality of power modules, and the working mode switching method comprises: The plurality of power modules switch the working mode from idle to the preparation phase or from the preparation phase to the running phase based on a control frame of working mode switching; the running phase comprises a feedback phase during train braking and a traction phase during train running; the preparation phase is a low-power running state, and the working direction is consistent with the working direction in the running phase; The plurality of power modules switch the working mode from the first running mode in the running phase to the second running mode under the action of the control device; The plurality of power modules switch the working mode from idle to the preparation phase or from the preparation phase to the running phase based on a control frame of working mode switching, and at least one of the following conditions is met: In the case that the control frame is a first control frame of train braking, the plurality of power modules switch the working mode from idle to the feedback preparation phase at the occurrence time of the next interrupt after the receiving time of the first control frame; the first control frame is triggered when the traction network voltage reaches the feedback preparation value; the preparation phase comprises the feedback preparation phase; In the case that the control frame is a second control frame of train braking, the plurality of power modules switch the working mode from the feedback preparation phase to the feedback phase at the occurrence time of the next interrupt after the receiving time of the second control frame; the second control frame is triggered when the traction network voltage reaches the feedback start value; In the case that the control frame is a third control frame of train starting, the plurality of power modules switch the working mode from idle to the traction preparation phase at the occurrence time of the next interrupt after the receiving time of the third control frame; the third control frame is triggered when the traction network voltage reaches the traction preparation value; the preparation phase comprises the traction preparation phase; In the case that the control frame is a fourth control frame of train starting, the plurality of power modules switch the working mode from the traction preparation phase to the traction phase at the occurrence time of the next interrupt after the receiving time of the fourth control frame; the fourth control frame is triggered when the traction network voltage reaches the traction start value.

2. The operating mode switching method according to claim 1, characterized by, The plurality of power modules switch the working mode from the first running mode in the running phase to the second running mode under the action of the control device, comprising: The plurality of power modules output a current-sharing bus current under the action of the control device, and synchronously switch the working mode from the feedback constant voltage mode in the running phase to the feedback limited power mode when the bus current reaches a first current threshold; the first running mode is the feedback constant voltage mode, and the second running mode is the feedback limited power mode.

3. The operating mode switching method according to claim 1, wherein The plurality of power modules switch the working mode from the first running mode in the running phase to the second running mode under the action of the control device, comprising: The multiple power modules output bus current in current sharing under the action of the control device, and synchronously switch the working mode from the traction constant voltage mode in the running stage to the traction limited power mode when the bus current reaches a second current threshold; the first running mode is the traction constant voltage mode, and the second running mode is the traction limited power mode.

4. The operating mode switching method according to any one of claims 1 to 3, characterized by, The multiple power modules determine a master weight value based on a power module state value, a bus sampling state value, a master sign state value, a power module online sign state value, a power module address, and a weight value corresponding to each state value in the bidirectional converter, and elect a master based on the master weight value; the rest of the power modules in the multiple power modules are slaves except the master; The master sends a control frame to the multiple slaves; The master and the multiple slaves synchronously switch the working mode from idle to the preparation stage or from the preparation stage to the running stage at the occurrence time of an interrupt after the receiving time of the control frame.

5. The operating mode switching method according to claim 4, wherein The working mode switching method further comprises: The master sends the same control frame to the multiple slaves twice through two network buses, so that the multiple slaves perform synchronous operation based on one of the control frames.

6. The operating mode switching method according to claim 4, wherein The weight of the power module state value, the weight of the bus sampling state value, the weight of the master sign state value, and the weight of the power module online sign state value decrease in turn, and the weight of the power module online sign state value is related to the power module address.

7. A bidirectional converter, characterized by The bidirectional converter comprises multiple power modules; a direct current end of the power module is connected with a direct current traction network, and an alternating current end of the power module is connected with an alternating current network; The multiple power modules are configured to switch the working mode from idle to the preparation stage or from the preparation stage to the running stage based on a control frame of working mode switching; The running stage comprises a feedback stage when the train brakes and a traction stage when the train travels; The preparation stage is a small power running state, and the working direction is consistent with the working direction in the running stage; The multiple power modules switch the working mode from the first running mode in the running stage to the second running mode under the action of the control device; The master sends a control frame to the multiple slaves; In the case that the control frame is a first control frame of train braking, the working mode is switched from idle to feedback preparation stage at the occurrence time of the next interrupt after the receiving time of the first control frame; the first control frame is triggered when the traction network voltage reaches a feedback preparation value; the preparation stage includes the feedback preparation stage; in the case that the control frame is a second control frame of train braking, the working mode is switched from the feedback preparation stage to feedback stage at the occurrence time of the next interrupt after the receiving time of the second control frame; the second control frame is triggered when the traction network voltage reaches a feedback start value; in the case that the control frame is a third control frame of train start, the working mode is switched from idle to traction preparation stage at the occurrence time of the next interrupt after the receiving time of the third control frame; the third control frame is triggered when the traction network voltage reaches a traction preparation value; the preparation stage includes the traction preparation stage; in the case that the control frame is a fourth control frame of train start, the working mode is switched from the traction preparation stage to traction stage at the occurrence time of the next interrupt after the receiving time of the fourth control frame; the fourth control frame is triggered when the traction network voltage reaches a traction start value.

8. A bidirectional converter according to claim 7, characterised in that, The bidirectional converter comprises a control device; the control device comprises a current-sharing loop, a power-limiting loop, a bus voltage loop and a modulation device; The current-sharing loop is connected to a current sampling point of the power module, the bus voltage loop is connected to a voltage sampling point of the power module, and the outputs of the current-sharing loop and the bus voltage loop are connected to the input of the power-limiting loop, and the output of the power-limiting loop is connected to the modulation device.

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