Control method and device of power electronic transformer, transformer, equipment and medium

Abstract

The invention discloses a power electronic transformer control method and device, a transformer, equipment and a medium, and the method comprises the steps: obtaining a bus voltage value of an intermediate high-frequency bus of a power electronic transformer when the power electronic transformer is determined to be in a light load state; if the bus voltage value is smaller than a preset first voltage value, controlling a circuit at any end of the power electronic transformer to charge an intermediate high-frequency bus of the power electronic transformer; and if the bus voltage value is greater than a preset first voltage value, the bus voltage value is smaller than a preset second voltage value, and the power electronic transformer continuously sends a high-level signal, controlling a circuit at any end of the power electronic transformer to charge an intermediate high-frequency bus of the power electronic transformer. By charging the middle high-frequency bus, the power of the middle high-frequency bus can be improved, so that relatively high backflow power can be avoided, the loss of a switch and a magnetic core can be reduced, and the current access efficiency can be improved.

Description

Background Art

[0002] One of the common AC power grids is an AC / DC distribution network based on power electronic transformers. When the AC power grid is connected, DC and AC are generally connected through power electronic transformers. In this way, multiple traditional grid connection points will convert AC power into DC power. DC power is not only highly stable, but also has low losses, which can ensure high-efficiency operation of the system.

[0003] Since the use of power electronic transformers affects the use of the system, in order to ensure that the system can operate stably, the currently commonly used power electronic transformer control method is: adopt a topology with soft switching conditions, such as a dual active bridge circuit, and control the power electronic transformer through the dual active bridge circuit to perform AC / DC conversion, or use a carrier shift method to control the power electronic transformer for AC / DC conversion.

[0004] However, the commonly used methods currently have the following technical problems: When using the carrier shift method for control, if single-phase shift modulation or double-phase shift modulation is used, a large reflux power will be generated, resulting in a sharp increase in current stress and the effective value of the inductor current, which not only reduces efficiency, but also increases switching and core losses, reducing regulation and access efficiency. Summary of the invention

[0005] The present invention proposes a control method, device, transformer, equipment and medium for a power electronic transformer. The method can charge the circuit at any end of the power electronic transformer to an intermediate high-frequency bus, thereby avoiding the generation of large reflux power, reducing switch and core losses, and improving access efficiency.

[0006] A first aspect of an embodiment of the present invention provides a control method for a power electronic transformer, the method comprising:

[0007] When it is determined that the power electronic transformer is in a light-load state, obtaining a bus voltage value of an intermediate high-frequency bus of the power electronic transformer, wherein the light-load state is a state in which the power electronic transformer is in a real-time power shortage state;

[0008] If the bus voltage value is less than the preset first voltage value, controlling the circuit at any end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer;

[0009] If the bus voltage value is greater than the preset first voltage value, the bus voltage value is less than the preset second voltage value and the power electronic transformer continues to send a high level signal, the circuit at either end of the power electronic transformer is controlled to charge the intermediate high-frequency bus of the power electronic transformer.

[0010] In a possible implementation of the first aspect, the power electronic transformer is respectively arranged in an A-phase circuit, a B-phase circuit, and a C-phase circuit of an AC power grid;

[0011] The power electronic transformer comprises: a plurality of power modules, wherein the first end of the power module is a low-voltage side port, and the second end of the power module is a high-voltage side port;

[0012] The low-voltage side ports of multiple power modules of the same phase are connected in parallel to access low-voltage direct current;

[0013] The high-voltage side ports of multiple power modules of the same phase are connected in series for receiving high-voltage alternating current.

[0014] In a possible implementation of the first aspect, the power module includes: four switching diodes, four high-voltage diodes, four low-voltage diodes, a high-voltage capacitor, a low-voltage capacitor, a transformer, and a resonant inductor;

[0015] The four switch diodes are connected to form a switch full-bridge circuit, the four high-voltage diodes are connected to form a high-voltage full-bridge circuit, and the four low-voltage diodes are connected to form a low-voltage full-bridge circuit;

[0016] The high-voltage full-bridge circuit is connected to the transformer via the resonant inductor, and the transformer is connected to the low-voltage full-bridge circuit;

[0017] The low-voltage full-bridge circuit is connected to the low-voltage capacitor, the switch full-bridge circuit is connected to the high-voltage full-bridge circuit via the high-voltage capacitor, and the high-voltage capacitor is arranged on the intermediate bus of the power electronic transformer.

[0018] In a possible implementation manner of the first aspect, controlling the circuit at any end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer includes:

[0019] During a preset first cycle, the diode at the low-voltage side port of the power electronic transformer is controlled to conduct based on the PWM signal, so that the low-voltage side port charges the resonant inductor of the intermediate high-frequency bus, so that the resonant inductor generates freewheeling current;

[0020] After a preset first cycle duration, the diode at the low-voltage side port of the power electronic transformer is closed based on the PWM signal control, so that the freewheeling current generated by the resonant inductor can be used to charge the high-voltage capacitor of the intermediate high-frequency bus.

[0021] In a possible implementation manner of the first aspect, controlling the circuit at any end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer includes:

[0022] During a preset first cycle, the diode at the high-voltage side port of the power electronic transformer is controlled to be turned on based on the PWM signal, so that the high-voltage side port charges the resonant inductor of the intermediate high-frequency bus, so that the resonant inductor generates freewheeling current;

[0023] After a preset first cycle time, the diode at the high-voltage side port of the power electronic transformer is closed based on the PWM signal control, so that the freewheeling current generated by the resonant inductor can be used to charge the high-voltage capacitor of the intermediate high-frequency bus.

[0024] In a possible implementation manner of the first aspect, after the step of obtaining the bus voltage value of the intermediate high-frequency bus of the power electronic transformer, the method further includes:

[0025] If the bus voltage value is greater than the preset first voltage value and the power electronic transformer is in a state of non-continuously sending a high level signal, the electronic components of the power electronic transformer are controlled to be locked.

[0026] In a possible implementation manner of the first aspect, after the step of obtaining the bus voltage value of the intermediate high-frequency bus of the power electronic transformer, the method further includes:

[0027] If the bus voltage value is greater than the preset first voltage value, the bus voltage value is greater than the preset second voltage value and the power electronic transformer continues to send a high level signal, the electronic device of the power electronic transformer is controlled to lock, and the power electronic transformer is controlled to continue to send a low level signal.

[0028] In a possible implementation manner of the first aspect, determining that the power electronic transformer is in a light load state includes:

[0029] Acquire a real-time power value of the power electronic transformer, where the real-time power value is the whole machine power of the power electronic transformer in normal operation;

[0030] If the real-time power value is less than the preset power value, it is determined that the power electronic transformer is in a light-load state;

[0031] If the real-time power value is greater than the preset power value, it is determined that the power electronic transformer is in a non-light load state.

[0032] In a possible implementation manner of the first aspect, after the step of determining that the power electronic transformer is in a non-light load state, the method further includes:

[0033] Control the power electronic transformer to perform single phase shift modulation or double phase shift modulation.

[0034] A second aspect of an embodiment of the present invention provides a control device for a power electronic transformer, the device comprising:

[0035] A voltage acquisition module is used to acquire a bus voltage value of an intermediate high-frequency bus of the power electronic transformer when it is determined that the power electronic transformer is in a light-load state, wherein the light-load state is a state in which the power electronic transformer is in a real-time power shortage state;

[0036] A first charging module, configured to control a circuit at any end of the power electronic transformer to charge an intermediate high-frequency bus of the power electronic transformer if the bus voltage value is less than a preset first voltage value;

[0037] The second charging module is used to control the circuit at either end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer if the bus voltage value is greater than the preset first voltage value, the bus voltage value is less than the preset second voltage value and the power electronic transformer continues to send a high-level signal.

[0038] In a possible implementation manner of the second aspect, controlling the circuit at any end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer includes:

[0039] During a preset first cycle, the diode at the low-voltage side port of the power electronic transformer is controlled to conduct based on the PWM signal, so that the low-voltage side port charges the resonant inductor of the intermediate high-frequency bus, so that the resonant inductor generates freewheeling current;

[0040] After a preset first cycle duration, the diode at the low-voltage side port of the power electronic transformer is closed based on the PWM signal control, so that the freewheeling current generated by the resonant inductor can be used to charge the high-voltage capacitor of the intermediate high-frequency bus.

[0041] In a possible implementation manner of the second aspect, controlling the circuit at any end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer includes:

[0042] During a preset first cycle, the diode at the high-voltage side port of the power electronic transformer is controlled to be turned on based on the PWM signal, so that the high-voltage side port charges the resonant inductor of the intermediate high-frequency bus, so that the resonant inductor generates freewheeling current;

[0043] After a preset first cycle time, the diode at the high-voltage side port of the power electronic transformer is closed based on the PWM signal control, so that the freewheeling current generated by the resonant inductor can be used to charge the high-voltage capacitor of the intermediate high-frequency bus.

[0044] In a possible implementation manner of the second aspect, the apparatus further includes:

[0045] The locking module is used to control the electronic components of the power electronic transformer to lock if the bus voltage value is greater than a preset first voltage value and the power electronic transformer is in a state of non-continuously sending a high-level signal.

[0046] In a possible implementation manner of the second aspect, the apparatus further includes:

[0047] The low-level module is used to control the electronic components of the power electronic transformer to be locked and control the power electronic transformer to continuously send a low-level signal if the bus voltage value is greater than a preset first voltage value, the bus voltage value is greater than a preset second voltage value and the power electronic transformer continues to send a high-level signal.

[0048] In a possible implementation manner of the second aspect, determining that the power electronic transformer is in a light load state includes:

[0049] Acquire a real-time power value of the power electronic transformer, where the real-time power value is the whole machine power of the power electronic transformer in normal operation;

[0050] If the real-time power value is less than the preset power value, it is determined that the power electronic transformer is in a light-load state;

[0051] If the real-time power value is greater than the preset power value, it is determined that the power electronic transformer is in a non-light load state.

[0052] In a possible implementation manner of the second aspect, the apparatus further includes:

[0053] The modulation module is used to control the power electronic transformer to perform single phase shift modulation or double phase shift modulation.

[0054] A third aspect of an embodiment of the present invention provides a control device for a power electronic transformer, the device comprising: the power electronic transformer comprising: a plurality of power modules, a first end of the power module being a low-voltage side port, and a second end of the power module being a high-voltage side port;

[0055] The low-voltage side ports of multiple power modules of the same phase are connected in parallel to access low-voltage direct current;

[0056] The high-voltage side ports of multiple power modules of the same phase are connected in series for receiving high-voltage alternating current.

[0057] In a possible implementation of the third aspect, the power module includes: four switching diodes, four high-voltage diodes, four low-voltage diodes, a high-voltage capacitor, a low-voltage capacitor, a transformer, and a resonant inductor;

[0058] The four switch diodes are connected to form a switch full-bridge circuit, the four high-voltage diodes are connected to form a high-voltage full-bridge circuit, and the four low-voltage diodes are connected to form a low-voltage full-bridge circuit;

[0059] The high-voltage full-bridge circuit is connected to the transformer via the resonant inductor, and the transformer is connected to the low-voltage full-bridge circuit;

[0060] The low-voltage full-bridge circuit is connected to the low-voltage capacitor, the switch full-bridge circuit is connected to the high-voltage full-bridge circuit via the high-voltage capacitor, and the high-voltage capacitor is arranged on the intermediate bus of the power electronic transformer.

[0061] Compared with the prior art, the control method, device, transformer, equipment and medium of a power electronic transformer provided by the embodiment of the present invention have the beneficial effects that: the present invention can obtain the bus voltage value of the intermediate high-frequency bus of the power electronic transformer when it is determined that the power electronic transformer is in a light-load state; when the bus voltage value is less than a preset first voltage value or the bus voltage value is greater than the preset first voltage value, the bus voltage value is less than a preset second voltage value and the power electronic transformer continues to send a high-level signal, the circuit at either end of the power electronic transformer is controlled to charge the intermediate high-frequency bus of the power electronic transformer; through the charging process, the power of the intermediate high-frequency bus is increased, thereby avoiding the generation of a large reflux power, thereby reducing the switch and core losses, and improving the efficiency of the access current. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a flow chart of a control method of a power electronic transformer provided by an embodiment of the present invention;

[0063] Figure 2 is an operation flow chart of a control method for a conventional working mode of a power electronic transformer provided by an embodiment of the present invention;

[0064] Figure 3 is an operation flow chart of a control method for a power electronic transformer provided by an embodiment of the present invention;

[0065] Figure 4 It is an operation schematic diagram of a control method for a power electronic transformer provided by an embodiment of the present invention;

[0066] Figure 5 It is a structural schematic diagram of a control device for a power electronic transformer provided by one embodiment of the present invention;

[0067] Figure 6 It is a structural schematic diagram of a power electronic transformer provided by one embodiment of the present invention;

[0068] Figure 7 is a circuit schematic diagram of a power module provided by an embodiment of the present invention;

[0069] Figure 8 It is a schematic diagram of pulse wave generation of a power module provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0070] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0071] One of the common AC power grids is an AC / DC distribution network based on power electronic transformers. When the AC power grid is connected, DC and AC are generally connected through power electronic transformers. In this way, multiple traditional grid connection points will convert AC power into DC power. DC power is not only highly stable, but also has low losses, which can ensure high-efficiency operation of the system.

[0072] Since the use of power electronic transformers affects the use of the system, in order to ensure that the system can operate stably, the currently commonly used power electronic transformer control method is: adopt a topology with soft switching conditions, such as a dual active bridge circuit, and control the power electronic transformer through the dual active bridge circuit to perform AC / DC conversion, or use a carrier shift method to control the power electronic transformer for AC / DC conversion.

[0073] However, the commonly used methods currently have the following technical problems: When using the carrier shift method for control, if single-phase shift modulation or double-phase shift modulation is used, a large reflux power will be generated, resulting in a sharp increase in current stress and the effective value of the inductor current, which not only reduces efficiency, but also increases switching and core losses, reducing regulation and access efficiency.

[0074] In order to solve the above problems, a control method, device, transformer, equipment and medium of a power electronic transformer provided in an embodiment of the present application will be introduced and explained in detail through the following specific embodiments.

[0075] Reference Figure 1 , which shows a flow chart of a control method for a power electronic transformer provided by an embodiment of the present invention.

[0076] In one embodiment, the method is applicable to a management system or control system of an AC power grid, which can communicate with a power electronic transformer of the AC power grid and adjust voltage and current by controlling the on / off states of various components of the power electronic transformer.

[0077] Wherein, as an example, the control method of the power electronic transformer may include:

[0078] S11. When it is determined that the power electronic transformer is in a light-load state, a bus voltage value of an intermediate high-frequency bus of the power electronic transformer is obtained, wherein the light-load state is a state in which the power electronic transformer is in a real-time power shortage state.

[0079] In one embodiment, the power electronic transformer may be in a light load state or in a normal working state, wherein the light load state may be a state where the power electronic transformer is in a state of insufficient real-time power.

[0080] In this state, in order to detect whether charging is needed to adjust the power of the power electronic transformer, the bus voltage value of the power electronic transformer can be obtained, and the bus voltage value can be the real-time voltage value of the intermediate high-frequency bus of the power electronic transformer. Subsequently, it can be determined whether charging and power adjustment are performed according to the size of the bus voltage value.

[0081] In one embodiment, the mainstream topology of the power electronic transformer is a dual active bridge circuit (DAB for short).

[0082] In one embodiment, the power electronic transformers are respectively arranged in the A-phase circuit, the B-phase circuit and the C-phase circuit of the AC power grid.

[0083] Specifically, two ends of the power electronic transformer are respectively connected to phase A, phase B and phase C of the AC power grid.

[0084] Wherein, the power electronic transformer comprises: a plurality of power modules, the first end of the power module is a low-voltage side port, and the second end of the power module is a high-voltage side port;

[0085] The low-voltage side ports of multiple power modules of the same phase are connected in parallel to access low-voltage direct current;

[0086] The high-voltage side ports of multiple power modules of the same phase are connected in series for receiving high-voltage alternating current.

[0087] In an actual operation mode, the power module includes: four switching diodes, four high-voltage diodes, four low-voltage diodes, a high-voltage capacitor, a low-voltage capacitor, a transformer and a resonant inductor;

[0088] The four switch diodes are connected to form a switch full-bridge circuit, the four high-voltage diodes are connected to form a high-voltage full-bridge circuit, and the four low-voltage diodes are connected to form a low-voltage full-bridge circuit;

[0089] The high-voltage full-bridge circuit is connected to the transformer via the resonant inductor, and the transformer is connected to the low-voltage full-bridge circuit;

[0090] The low-voltage full-bridge circuit is connected to the low-voltage capacitor, the switch full-bridge circuit is connected to the high-voltage full-bridge circuit via the high-voltage capacitor, and the high-voltage capacitor is arranged on the intermediate bus of the power electronic transformer.

[0091] In actual operation, the direction of current flow can be controlled by controlling the conduction and disconnection of each diode, thereby achieving charging through the current and realizing power adjustment so that the real-time power of the power electronic transformer can meet the requirements.

[0092] In order to determine whether the power electronic transformer is in a light-load state, as an example, the determination that the power electronic transformer is in a light-load state may include the following sub-steps:

[0093] S111. Acquire a real-time power value of the power electronic transformer, where the real-time power value is the whole machine power of the power electronic transformer in normal operation.

[0094] S112: If the real-time power value is less than the preset power value, it is determined that the power electronic transformer is in a light load state.

[0095] S113: If the real-time power value is greater than the preset power value, it is determined that the power electronic transformer is in a non-light load state.

[0096] Specifically, power detection can be performed when the power electronic transformer operates normally to obtain a real-time power value, and the real-time power value can be the whole machine power of the power electronic transformer.

[0097] If the real-time power value is less than the preset power value, it means that the power of the power electronic transformer is insufficient. It can be determined that the power electronic transformer is in a light load state. The power electronic transformer can be placed in a pulse wave control mode to control the power electronic transformer for power adjustment.

[0098] On the contrary, if the real-time power value is greater than the preset power value, it means that the power electronic transformer is working normally, and the power electronic transformer can be controlled to work according to the traditional working mode.

[0099] It should be noted that the size of the preset power value depends on different circuit designs. The preset power value is often distributed below 30% load when the core loss occupies a large proportion, and the preset power value needs to be smaller than the power generated by the pulse wave of the power electronic transformer.

[0100] In order to make the power electronic transformer work in the conventional working mode, as an example, after the step of determining that the power electronic transformer is in a non-light load state, the method may include the following steps:

[0101] S114. Control the power electronic transformer to perform single phase shift modulation or double phase shift modulation.

[0102] The traditional working mode can be the traditional phase shift modulation strategy, refer to Figure 2 , shows an operation flow chart of a control method for a conventional working mode of a power electronic transformer provided by an embodiment of the present invention.

[0103] Specifically, Figure 2 As shown, the traditional working mode can be a current and voltage dual closed-loop control strategy. Under this control strategy, AC / DC is used to realize the control of the low-voltage side voltage. By performing voltage loop control on the C1 voltage, and based on the reactive power requirements of the power electronic transformer, it can be used to generate a reference current for the grid-side current of the power electronic transformer. By performing current closed-loop control with the grid-side current, it can be used to generate a modulation signal for the AC / DC circuit. Among them, Vc1-ref is the reference value of the low-voltage side voltage, and Vc1 is the actual value of the low-voltage side voltage. Ig-ref is the reference value of the grid-side current, and Ig is the actual value of the grid-side current. For DC / DC control, the modulation of the dual active bridge circuit adopts a carrier shift modulation strategy, which is mature and reliable as a whole. Figure 2 The modulation strategy has been introduced in detail in the patent, so this patent will not repeat it. In general, DAB controls the intermediate bus voltage of AC / DC and DC / DC circuits, and realizes stable control of the bus through a single voltage loop. Among them, Vc2-ref is the reference value of the intermediate bus voltage, and Vc2 is the real-time value of the intermediate bus voltage. This control strategy is an effective control method for power electronic transformers at present, which can meet the balance in multi-module systems and stable grid connection.

[0104] The above operation method is to take the low-voltage capacitor voltage and the grid-side reactive power as the control targets, and convert the two as reference signals into two-phase rotation through coordinate transformation and adjust and control through the voltage and current double closed loop. The final generated signal is coupled into an AC modulation signal through coordinate transformation, and then a switching signal is generated through PWM modulation and input into the switching device to achieve the purpose of overall regulation.

[0105] S12: If the bus voltage value is less than a preset first voltage value, control the circuit at any end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer.

[0106] S13. If the bus voltage value is greater than the preset first voltage value, the bus voltage value is less than the preset second voltage value and the power electronic transformer continues to send a high-level signal, control the circuit at either end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer.

[0107] In one embodiment, if the bus voltage value is less than the preset first voltage value, it means that the voltage of the power electronic transformer is low and needs to be adjusted. The circuit at any end of the power electronic transformer can be controlled to charge the intermediate high-frequency bus of the power electronic transformer.

[0108] Similarly, if the bus voltage value is greater than the preset first voltage value but less than the preset second voltage value, and the power electronic transformer continues to send a high-level signal, the circuit at either end of the power electronic transformer can also be controlled to charge the intermediate high-frequency bus of the power electronic transformer.

[0109] Specifically, after determining that the power electronic transformer is in a light load state, the light load operation mode can be entered. First, the bus voltage value is obtained. If the bus voltage value (Vc2) is less than the preset first voltage value (Vset1), the power electronic transformer can work in a pulse wave state. Working in the pulse working mode can ensure that the bus voltage value (Vc2) is charged. Because when the power is set, the power of the pulse operation is guaranteed to be greater than the power electronic transformer, thereby ensuring that the bus voltage value (Vc2) will continue to rise.

[0110] In order to achieve voltage hysteresis control for the state where the power electronic transformer continuously sends a high-level signal, thereby avoiding the problem of frequent switching, the value of the preset first voltage value (Vset1) is often lower than the rated voltage, but will not trigger the undervoltage protection of the power module. In actual engineering, it can be considered to be set at 90% of the rated voltage.

[0111] If the bus voltage value is greater than the preset first voltage value (Vset1) and the power electronic transformer continues to send a high-level signal, it indicates that the whole needs to work in the pulse wave mode. In this state, it is determined whether the bus voltage value is greater than the preset second voltage value (Vset2). If the bus voltage value is less than the preset second voltage value, it means that the voltage is still insufficient and needs to be charged to increase its power.

[0112] It should be noted that the preset second voltage value (Vset2) often needs to be set to exceed the rated operating voltage, but Vset2 cannot exceed the overvoltage threshold of the power module.

[0113] In general, through the control strategy of this patent, the bus voltage value (Vc2) will be fixed between the preset first voltage value (Vset1) and the preset second voltage value (Vset2), thereby ensuring power transmission under light load and indirectly ensuring power balance between modules. And the power electronic transformer works between the pulse wave mode and the locked state, which can further reduce the core loss and switching loss of the circuit.

[0114] According to the above analysis, the first end of the power electronic transformer is a low-voltage side port, and the second end of the power electronic transformer is a high-voltage side port. In an optional embodiment, current can be transmitted from the low-voltage side port to charge the intermediate high-frequency bus of the power electronic transformer, so that the voltage of the intermediate high-frequency bus of the power electronic transformer is increased to meet the power requirement.

[0115] Wherein, as an example, the circuit at any end of the power electronic transformer is controlled to charge the intermediate high-frequency bus of the power electronic transformer, which may include the following sub-steps:

[0116] S21. Within a preset first cycle duration, based on the PWM signal, control the diode at the low-voltage side port of the power electronic transformer to conduct, so that the low-voltage side port charges the resonant inductor of the intermediate high-frequency bus to generate freewheeling current for the resonant inductor.

[0117] S22. After a preset first cycle duration, the diode at the low-voltage side port of the power electronic transformer is controlled to be closed based on the PWM signal, so that the freewheeling current generated by the resonant inductor can be used to charge the high-voltage capacitor of the intermediate high-frequency bus.

[0118] Specifically, within a preset first cycle duration (e.g., T1), the diode at the low-voltage side port of the power electronic transformer can be controlled to conduct based on a PWM signal, so that the low-voltage side port charges the resonant inductor of the intermediate high-frequency bus for the resonant inductor to generate freewheeling current.

[0119] After T1 time, the diode at the low-voltage side port of the power electronic transformer is closed based on the PWM signal control. Since the inductor current cannot change suddenly, the current will continue to flow through the diode. Its freewheeling loop is the resonant inductor. During the freewheeling process, the current of the resonant inductor continues to charge the capacitor until the current drops to zero.

[0120] In this process, since the current at the low-voltage side port continuously provides power to the intermediate high-frequency bus, the power is related to the T1 time. In actual design, different power outputs can be achieved by adjusting the length of T1.

[0121] Compared with the traditional shift control strategy, the above operation mode significantly reduces the voltage superimposed on the transformer, so the core loss can be greatly reduced, thereby meeting the efficiency optimization requirements of light loads. In addition, power transmission does not depend on the voltage value of the high-voltage side, and the low-voltage side can continuously transfer power to the high-voltage side.

[0122] According to the above analysis, the first end of the power electronic transformer is a low-voltage side port, and the second end of the power electronic transformer is a high-voltage side port. In another optional embodiment, current can be transmitted from the high-voltage side port to charge the intermediate high-frequency bus of the power electronic transformer, so that the voltage of the intermediate high-frequency bus of the power electronic transformer is increased to meet the power requirement.

[0123] Wherein, as an example, the circuit at any end of the power electronic transformer is controlled to charge the intermediate high-frequency bus of the power electronic transformer, which may include the following sub-steps:

[0124] S31. Within a preset first cycle duration, based on a PWM signal, control the diode at the high-voltage side port of the power electronic transformer to conduct, so that the high-voltage side port charges the resonant inductor of the intermediate high-frequency bus, so that the resonant inductor generates freewheeling current.

[0125] S32. After a preset first cycle duration, the diode at the high-voltage side port of the power electronic transformer is controlled to be closed based on the PWM signal, so that the freewheeling current generated by the resonant inductor can be used to charge the high-voltage capacitor of the intermediate high-frequency bus.

[0126] Specifically, within a preset first cycle duration (e.g., T1), the diode at the high-voltage side port of the power electronic transformer can be controlled to conduct based on a PWM signal, so that the high-voltage side port charges the resonant inductor of the intermediate high-frequency bus for the resonant inductor to generate freewheeling current.

[0127] After T1 time, the diode at the high-voltage side port of the power electronic transformer is closed based on the PWM signal control. Since the inductor current cannot change suddenly, the current will continue to flow through the diode. Its freewheeling loop is the resonant inductor. During the freewheeling process, the current of the resonant inductor continues to charge the capacitor until the current drops to zero.

[0128] During charging, the high-voltage side port continuously provides power to the intermediate high-frequency AC bus. The power is related to the T1 time. In actual design, different power outputs can be achieved by adjusting the length of T1.

[0129] Compared with the traditional shift control strategy, the voltage superimposed on the transformer is the same as the heavy load scenario, and the resulting core loss is also the same as the heavy load situation. Since the voltage superimposed on the transformer is significantly reduced, the core loss can be greatly reduced, thereby meeting the efficiency optimization requirements of light load.

[0130] In an optional embodiment, the bus voltage value of the power electronic transformer may be greater than the preset first voltage value due to a fault in the power electronic transformer, and the power electronic transformer continues to send a high-level signal.

[0131] In order to immediately protect each period in the event of a device or circuit failure, the following sub-steps may be included, as an example, after the step of obtaining the bus voltage value of the intermediate high-frequency bus of the power electronic transformer:

[0132] S14: If the bus voltage value is greater than a preset first voltage value and the power electronic transformer is in a state of non-continuously sending a high-level signal, the electronic components of the power electronic transformer are controlled to be locked.

[0133] If the bus voltage value is greater than the preset first voltage value (Vset1), and it is determined whether the power electronic transformer continues to send a high level signal, it can also be determined whether the working state of the power electronic transformer is 1. If it is not 1, the power electronic transformer does not continue to send a high level signal. It is possible that the power electronic transformer sends a high level signal intermittently.

[0134] At this time, the power grid or circuit may have a fault or other situation. The power grid and the power electronic transformer can be locked as a whole by controlling the conduction of the switching device to achieve isolation and protect the entire circuit.

[0135] On the basis of the above, the power electronic transformer may send high-level signals intermittently. In order to modify the state of the power electronic transformer and avoid triggering the ports on both sides to charge the intermediate high-frequency bus, as an example, after the step of obtaining the bus voltage value of the intermediate high-frequency bus of the power electronic transformer, the following sub-steps may be included:

[0136] S15. If the bus voltage value is greater than the preset first voltage value, the bus voltage value is greater than the preset second voltage value and the power electronic transformer continues to send a high level signal, the electronic components of the power electronic transformer are controlled to be locked, and the power electronic transformer is controlled to continue to send a low level signal.

[0137] On the basis of step S14, it is determined whether the bus voltage value is less than the preset second voltage value. If the bus voltage value is greater than the preset second voltage value, the power electronic transformer can enter the locking mode, disconnect all components of the power electronic transformer, and set the working state of the power electronic transformer to 0, that is, let the power electronic transformer continue to send a low-level signal. This state indicates that the bus voltage value has been charged to a higher voltage and needs to be locked to suspend energy transmission. At the same time, all components of the power electronic transformer can also be protected after locking.

[0138] Reference Figure 2 , shows an operation flow chart of a control method for a power electronic transformer provided by an embodiment of the present invention.

[0139] Specifically, the control method of the power electronic transformer may include the following steps:

[0140] The first step is SST power detection to detect the real-time power value of the power electronic transformer.

[0141] In the second step, if the real-time power value is greater than the preset power value, it is determined that the power electronic transformer is in a non-light load state, and the power electronic transformer can be controlled to operate in a traditional operating mode.

[0142] In the third step, if the real-time power value is less than the preset power value, it is determined that the power electronic transformer is in a light-load state, and the power electronic transformer can be controlled to enter a light-load operation mode.

[0143] The fourth step is to obtain the bus voltage value (Vc2) of the power electronic transformer. If the bus voltage value (Vc2) is less than the preset first voltage value (Vset1), the power electronic transformer can be controlled to operate in a pulse wave state, and the operating state of the power electronic transformer is controlled to be set to 1, and the power electronic transformer can continue to send a high-level signal.

[0144] In the fifth step, if the bus voltage value (Vc2) is greater than the preset first voltage value (Vset1), and the working state of the power electronic transformer is not set to 1, all components of the power electronic transformer can be controlled to be locked.

[0145] In the sixth step, if the bus voltage value (Vc2) is greater than the preset first voltage value (Vset1), the working state of the power electronic transformer is set to 1, and the bus voltage value (Vc2) is less than the preset first voltage value (Vset2), all the devices of the power electronic transformer can be controlled to be locked, and the working state of the power electronic transformer can be controlled to be set to 0, and the power electronic transformer can continue to send a low-level signal.

[0146] In the seventh step, if the bus voltage value (Vc2) is greater than the preset first voltage value (Vset1), the working state of the power electronic transformer is set to 1, and the bus voltage value (Vc2) is greater than the preset first voltage value (Vset2), the power electronic transformer can be controlled to operate in a pulse wave state.

[0147] Reference Figure 4 , showing an operation schematic diagram of a control method for a power electronic transformer provided by an embodiment of the present invention.

[0148] After adopting the technical solution of the present invention, the initial working state of the power electronic transformer is set to 1, and a high-level signal is continuously sent. Since the transmission power of the pulse wave mode set in the circuit is greater than the actual power of the circuit, the additional power transmitted by the power electronic transformer will be accumulated on the intermediate high-frequency bus, resulting in a gradual increase in the voltage of the bus voltage value (Vc2). When the bus voltage value (Vc2) increases to the preset first voltage value (Vset2), the state switching is triggered, the working state of the power electronic transformer is set to 0, and a low-level signal is continuously sent. All components of the power electronic transformer are locked, resulting in a decrease in the power transmitted to the intermediate high-frequency bus and a gradual decrease in voltage. If the bus voltage value (Vc2) decreases to the preset first voltage value (Vset1), the circuit restarts to work in the pulse mode, and the DAB working state is set to 1.

[0149] The bus voltage value (Vc2) is similar to working within the hysteresis range. The hysteresis control has extremely strong robustness, which can make the bus voltage value (Vc2) always remain within the range of the preset first voltage value (Vset1) and the preset first voltage value (Vset2) when the load is light. The overall control is simple and easy to implement, and the control effect is excellent.

[0150] In this embodiment, the embodiment of the present invention provides a control method for a power electronic transformer, and its beneficial effect is that: the present invention can obtain the bus voltage value of the intermediate high-frequency bus of the power electronic transformer when it is determined that the power electronic transformer is in a light-load state; when the bus voltage value is less than a preset first voltage value or the bus voltage value is greater than the preset first voltage value, the bus voltage value is less than a preset second voltage value and the power electronic transformer continues to send a high-level signal, the circuit at any end of the power electronic transformer is controlled to charge the intermediate high-frequency bus of the power electronic transformer; through the charging process, the power of the intermediate high-frequency bus is increased, thereby avoiding the generation of a large reflux power, thereby reducing the switch and core losses, and improving the efficiency of the access current.

[0151] The present invention also provides a control device for a power electronic transformer. Figure 5 , showing a schematic structural diagram of a control device for a power electronic transformer provided by an embodiment of the present invention.

[0152] Wherein, as an example, the control device of the power electronic transformer may include:

[0153] The voltage acquisition module 201 is used to acquire the bus voltage value of the intermediate high-frequency bus of the power electronic transformer when it is determined that the power electronic transformer is in a light-load state, wherein the light-load state is a state where the power electronic transformer is in a real-time power shortage state;

[0154] The first charging module 202 is used to control the circuit at any end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer if the bus voltage value is less than a preset first voltage value;

[0155] The second charging module 203 is used to control the circuit at any end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer if the bus voltage value is greater than the preset first voltage value, the bus voltage value is less than the preset second voltage value and the power electronic transformer continues to send a high-level signal.

[0156] Optionally, the circuit controlling any one end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer includes:

[0157] During a preset first cycle, the diode at the low-voltage side port of the power electronic transformer is controlled to conduct based on the PWM signal, so that the low-voltage side port charges the resonant inductor of the intermediate high-frequency bus, so that the resonant inductor generates freewheeling current;

[0158] After a preset first cycle duration, the diode at the low-voltage side port of the power electronic transformer is closed based on the PWM signal control, so that the freewheeling current generated by the resonant inductor can be used to charge the high-voltage capacitor of the intermediate high-frequency bus.

[0159] Optionally, the circuit controlling any one end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer includes:

[0160] During a preset first cycle, the diode at the high-voltage side port of the power electronic transformer is controlled to be turned on based on the PWM signal, so that the high-voltage side port charges the resonant inductor of the intermediate high-frequency bus, so that the resonant inductor generates freewheeling current;

[0161] After a preset first cycle time, the diode at the high-voltage side port of the power electronic transformer is closed based on the PWM signal control, so that the freewheeling current generated by the resonant inductor can be used to charge the high-voltage capacitor of the intermediate high-frequency bus.

[0162] Optionally, the device further comprises:

[0163] The locking module is used to control the electronic components of the power electronic transformer to lock if the bus voltage value is greater than a preset first voltage value and the power electronic transformer is in a state of non-continuously sending a high-level signal.

[0164] Optionally, the device further comprises:

[0165] The low-level module is used to control the electronic components of the power electronic transformer to be locked and control the power electronic transformer to continuously send a low-level signal if the bus voltage value is greater than a preset first voltage value, the bus voltage value is greater than a preset second voltage value and the power electronic transformer continues to send a high-level signal.

[0166] Optionally, determining that the power electronic transformer is in a light load state includes:

[0167] Acquire a real-time power value of the power electronic transformer, where the real-time power value is the whole machine power of the power electronic transformer in normal operation;

[0168] If the real-time power value is less than the preset power value, it is determined that the power electronic transformer is in a light-load state;

[0169] If the real-time power value is greater than the preset power value, it is determined that the power electronic transformer is in a non-light load state.

[0170] Optionally, the device further comprises:

[0171] The modulation module is used to control the power electronic transformer to perform single phase shift modulation or double phase shift modulation.

[0172] The present invention also provides a power electronic transformer. Figure 6 , showing a schematic structural diagram of a power electronic transformer provided by an embodiment of the present invention.

[0173] Wherein, as an example, the power electronic transformer may include: a plurality of power modules, the first end of the power module is a low-voltage side port, and the second end of the power module is a high-voltage side port;

[0174] The low-voltage side ports of multiple power modules of the same phase are connected in parallel to access low-voltage direct current;

[0175] The high-voltage side ports of multiple power modules of the same phase are connected in series for receiving high-voltage alternating current.

[0176] Reference Figure 6 It can be seen that the power electronic transformer is composed of a large number of power modules, which have two ports, the low-voltage side and the high-voltage side. The low-voltage side ports of all power modules are connected in parallel to meet the power collection of the low-voltage side. The high-voltage side adopts a series working mode to achieve the access to the medium-voltage grid, which includes the medium-voltage AC grid and the medium-voltage DC grid. Figure 6As shown, the medium-voltage AC power grid is introduced as an example. The medium-voltage AC power grid consists of three phases ABC. For the access of phase A, N power modules are connected in series for the ports on the high-voltage side. After the series connection, two ports are formed, which are connected to phase A and the neutral point of the power grid respectively. The connection for phases B and C is the same as that for phase A. By connecting in series, the withstand voltage of each module can be reduced in the medium-voltage process, and the power devices inside the module can use common power devices on the market, thereby reducing the production and manufacturing cost of power electronic transformers.

[0177] The topological structure of each power module includes two-level topologies, namely the AC / DC circuit connected to the medium-voltage grid and the isolated DC / DC circuit. The AC / DC realizes the conversion of DC power energy in the module to medium-voltage AC power energy, and the full-bridge circuit can meet the needs of AC / DC conversion. Since the power modules are connected in series, the output waveform phase overlap between modules can be achieved by carrier shifting, thereby optimizing the grid-connected voltage waveform quality and reducing the use of the filtering system. In the carrier shifting mode, the AC / DC circuit can operate at a lower switching frequency, and also ensures a relatively good grid-connected current waveform quality. In this mode, the switching loss caused by AC / DC is greatly reduced. In actual design, the loss caused by the AC / DC circuit is relatively small compared to the loss of the entire power module. The loss of this AC / DC link is not considered in the subsequent loss analysis.

[0178] For isolated DC / DC circuits, high-frequency and high-efficiency operation must be ensured. High frequency can reduce the number of magnetic components, and high efficiency is based on the operation requirements of isolated DC / DC circuits in power electronic transformers. Since isolated DC / DC circuits are relatively complex and have many components, they account for most of the losses of power electronic transformers. Therefore, reasonable circuit design is required to meet efficiency requirements. At present, the mainstream topology for power electronic transformers is the dual active bridge circuit (DAB). The dual active bridge circuit has the characteristics of soft switching operation, low conduction loss, convenient control, and bidirectional energy, and is suitable for AC and DC distribution network scenarios.

[0179] Reference Figure 7 , shows a circuit schematic diagram of a power module provided in one embodiment of the present invention.

[0180] In one embodiment, the power module includes: four switching diodes, four high-voltage diodes, four low-voltage diodes, a high-voltage capacitor C2, a low-voltage capacitor C1, a transformer and a resonant inductor;

[0181] The four switch diodes are connected to form a switch full-bridge circuit, the four high-voltage diodes are connected to form a high-voltage full-bridge circuit, and the four low-voltage diodes are connected to form a low-voltage full-bridge circuit;

[0182] The high-voltage full-bridge circuit is connected to the transformer via the resonant inductor, and the transformer is connected to the low-voltage full-bridge circuit;

[0183] The low voltage full bridge circuit is connected to the low voltage capacitor C1, the switch full bridge circuit is connected to the high voltage full bridge circuit via the high voltage capacitor C2, and the high voltage capacitor is arranged on the intermediate bus of the power electronic transformer.

[0184] Reference Figure 7 The four low-voltage diodes are respectively a low-voltage diode S1, a low-voltage diode S2, a low-voltage diode S3 and a low-voltage diode S4, forming a low-voltage full-bridge circuit on the low-voltage side.

[0185] The four high-voltage diodes are respectively a high-voltage diode S5, a high-voltage diode S6, a high-voltage diode S7 and a high-voltage diode S8, which constitute a high-voltage full-bridge circuit on the high-voltage side.

[0186] Switching diode Q1, switching diode Q2, switching diode Q3 and switching diode Q4. In the power module, the AC / DC circuit of the power module is composed of a full-bridge circuit, in which Q1 and Q2, Q3 and Q4 are respectively connected in series to form two bridge arms, and the output of the bridge arm is used as the output of the power module, and the output current can be defined as ig.

[0187] It should be noted that the voltage levels at both ends of the power electronic transformer composed of power modules are 10kV AC and 750V DC respectively. Due to the voltage level problem on the 10kV AC side, a cascade connection is required, so ig is represented by the AC side current of a single-phase single module, and the modules on the AC side are connected in series. The modules on the 750V DC side are connected in parallel, and the structure can be referred to. Figure 6 .

[0188] The AC / DC and DC / DC circuits are connected by a high-voltage capacitor C2, which can filter the AC / DC power and DC / DC power. The isolated DC / DC circuit uses a DAB circuit, which is symmetrical on the high-voltage side and the low-voltage side. Both use a full-bridge circuit, and the outputs of the high-voltage full-bridge circuit on the high-voltage side and the low-voltage full-bridge circuit on the low-voltage side are connected through a transformer.

[0189] The normal operation of the DAB circuit also requires a resonant inductor, which can be realized by the leakage inductance of the transformer or by an external inductor. The external inductor can be configured on the low-voltage side or on the high-voltage side. In this example, a resonant inductor is connected in series with the full-bridge circuit on the high-voltage side. On the low-voltage side of the DAB, a low-voltage capacitor C1 is configured to realize the low-voltage side DC bus.

[0190] In addition, it should be noted that since all power modules bear the power task equally, the real-time power value is collected in Figure 3 The name SST in Chinese is solid state transformer, which is also called solid-state transformer. This name is also another name for power electronic transformer.

[0191] The above traditional working mode refers to the traditional carrier phase shift modulation method. Figure 2 The control strategy of voltage and current dual closed loop is shown in FIG.

[0192] For further explanation, two examples are used to illustrate charging.

[0193] In one example, we first introduce the scenario of power transfer from the low-voltage side to the high-voltage side. The output of the low-voltage side bridge circuit is in the form of a pulse voltage. Specifically, in one switching cycle, S1 and S3 can be controlled to be turned on, where the conduction time of S1 and S3 only lasts for T1 time, S1 and S2 signals are complementary, and S3 and S4 signals are complementary. It is also possible to control S5 and S7, S6 and S8 devices to remain on only for T1 time.

[0194] During the T1 time, S1 and S4 are turned on, S6 and S8 are turned on, the output voltage of the low-voltage bridge circuit on the low-voltage side is the low-voltage side bus voltage Vc1, and the output voltage of the high-voltage bridge circuit on the high-voltage side is 0. At this time, the low-voltage side bus voltage is used to charge the inductor on the resonant circuit, and the current IL in the high-frequency circuit rises linearly. After the T1 time, all devices can be controlled to be turned off. Since the inductor current cannot change suddenly, the current will continue to flow through the diode. Its freewheeling circuit is a resonant inductor, and its flow direction is the S5 diode, capacitor C2, S8 diode, transformer, S2, S4. During the freewheeling process, the current continues to charge C2, and the Vcd voltage is the C2 voltage until the current drops to zero. In this mode, since S2 and S4 are turned on, the Vab voltage is zero. After half of the switching cycle of this operating mode, S3 and S2 are turned on first, realizing the reversal of the Vab output voltage. At the same time, S5 and S7 are turned on, ensuring that Vcd is 0, and the low-voltage side voltage charges the inductor. After T1 time, the inductor current is continued through the diodes of S6 and S7. At the same time, Vab maintains a voltage of zero due to the action of the switch tube.

[0195] During the pulse wave generation period, the low-voltage side continues to provide power to the intermediate high-frequency bus. The power is related to the T1 time. In actual design, the length of T1 can be adjusted to achieve different power outputs. Compared with the traditional shift control strategy, the voltage superimposed on the transformer is the same as the heavy load scenario, and the resulting core loss is also consistent with the heavy load situation. Under light load conditions, the core loss accounts for a large proportion in traditional solutions. Through the solution of the present invention, the voltage superimposed on the transformer is significantly reduced, and the core loss can be greatly reduced, thereby meeting the efficiency optimization requirements of light loads.

[0196] Reference Figure 8 , showing a schematic diagram of pulse wave generation of a power module provided in an embodiment of the present invention.

[0197] S1-S8 of the power module are all turned on by PWM signal control; refer to Figure 8 In the first section T1, S1 and S4, S6 and S8 are turned on. In the second section T1, S2 and S3, S5 and S7 are turned on. In the third section T1, S1 and S4, S6 and S8 are turned on again. The pulse wave control strategy is implemented by analogy, which greatly reduces the core loss under light load and thus improves the conversion efficiency under light load conditions.

[0198] And by controlling the duty cycle of each device; to determine the time interval. At the same time, S1, S2 and S3, S4 are a group of switch tubes on a single bridge arm, and the on-off logic of the two is opposite, that is, S1 is on, S2 is off; S3 is on, S4 is off.

[0199] In another example, power can also be transmitted from the high-voltage side to the low-voltage side. In this scenario, the output of the high-voltage side bridge circuit as a whole is in the form of a pulse voltage. Specifically, in one switching cycle, the conduction time of S5 and S7 is controlled to last only for T1 time, and the S5 and S6 signals are complementary, and the S7 and S8 signals are complementary. Control S1 and S3, S2 and S4 devices to remain on only during T1 time. During the T1 time, S5 and S8 can also be controlled to be on, and S2 and S4 can be controlled to be on. The output voltage of the high-voltage side bridge circuit is the high-voltage side bus voltage Vc2, and the output voltage of the low-voltage side bridge circuit is 0. At this time, the high-voltage side bus voltage charges the inductance on the resonant circuit, and the current IL in the high-frequency circuit rises linearly.

[0200] After T1 time, all devices are turned off. Since the inductor current cannot change suddenly, the current will continue to flow through the diode. Its freewheeling circuit is a resonant inductor, S1 diode, C1, S4 diode, transformer, S6, S8. During the freewheeling process, the current continues to charge C1, and the Vab voltage is the C1 voltage until the current drops to zero. In this mode, since S6 and S8 are turned on, the Vcd voltage is zero. After half of the switching cycle of this operating mode, S7 and S6 are turned on first, realizing the reversal of the Vcd output voltage. At the same time, S1 and S3 are turned on, ensuring that Vab is 0, and the low-voltage side voltage charges the inductor. After T1 time, the inductor current continues to flow through the diodes of S2 and S3, and at the same time, Vcd maintains a voltage of zero due to the action of the switch tube.

[0201] During the pulse wave generation period, the high-voltage side continuously provides power to the intermediate high-frequency AC bus. The power is related to the T1 time. In actual design, different power outputs can be achieved by adjusting the length of T1.

[0202] Those skilled in the art can clearly understand that, for the sake of convenience and brevity of description, the specific working process of the device described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0203] Furthermore, an embodiment of the present application also provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the control method for the power electronic transformer as described in the above embodiment is implemented.

[0204] Furthermore, an embodiment of the present application also provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer-executable program, and the computer-executable program is used to enable a computer to execute the control method of the power electronic transformer as described in the above embodiment.

[0205] It should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", etc. is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. When an element such as a layer, region or substrate is referred to as being "on" or "above" another element, it can be directly on the other element, or there can also be an intermediate element. On the contrary, when an element is referred to as "directly on" or "above" another element, there is no intermediate element. It should also be understood that when an element is referred to as being "under" or "below" another element, it can be directly under or below the other element, or there can also be an intermediate element. On the contrary, when an element is referred to as being "directly under" or "below" another element, there is no intermediate element. Unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0206] Those skilled in the art will appreciate that the embodiments of the present application may also provide computer program products. Therefore, the present application may adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the present application may adopt the form of computer program products implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program codes.

[0207] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), apparatuses, and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0208] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0209] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0210] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A control method for a power electronic transformer, characterized in that: The method comprises: When it is determined that the power electronic transformer is in a light-load state, obtaining a bus voltage value of an intermediate high-frequency bus of the power electronic transformer, wherein the light-load state is a state in which the power electronic transformer is in a real-time power shortage state; If the bus voltage value is less than the preset first voltage value, controlling the circuit at any end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer; If the bus voltage value is greater than the preset first voltage value, the bus voltage value is less than the preset second voltage value and the power electronic transformer continues to send a high level signal, the circuit at either end of the power electronic transformer is controlled to charge the intermediate high-frequency bus of the power electronic transformer.

2. The control method of the power electronic transformer according to claim 1, characterized in that: The power electronic transformers are respectively arranged in the A-phase circuit, the B-phase circuit and the C-phase circuit of the AC power grid; The power electronic transformer comprises: a plurality of power modules, wherein the first end of the power module is a low-voltage side port, and the second end of the power module is a high-voltage side port; The low-voltage side ports of multiple power modules of the same phase are connected in parallel to access low-voltage direct current; The high-voltage side ports of multiple power modules of the same phase are connected in series for receiving high-voltage alternating current.

3. The control method of the power electronic transformer according to claim 2, characterized in that: The power module includes: four switching diodes, four high-voltage diodes, four low-voltage diodes, a high-voltage capacitor, a low-voltage capacitor, a transformer and a resonant inductor; The four switch diodes are connected to form a switch full-bridge circuit, the four high-voltage diodes are connected to form a high-voltage full-bridge circuit, and the four low-voltage diodes are connected to form a low-voltage full-bridge circuit; The high-voltage full-bridge circuit is connected to the transformer via the resonant inductor, and the transformer is connected to the low-voltage full-bridge circuit; The low-voltage full-bridge circuit is connected to the low-voltage capacitor, the switch full-bridge circuit is connected to the high-voltage full-bridge circuit via the high-voltage capacitor, and the high-voltage capacitor is arranged on the intermediate bus of the power electronic transformer.

4. The control method of the power electronic transformer according to claim 1, characterized in that: The circuit controlling any one end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer includes: During a preset first cycle, the diode at the low-voltage side port of the power electronic transformer is controlled to conduct based on the PWM signal, so that the low-voltage side port charges the resonant inductor of the intermediate high-frequency bus, so that the resonant inductor generates freewheeling current; After a preset first cycle duration, the diode at the low-voltage side port of the power electronic transformer is closed based on the PWM signal control, so that the freewheeling current generated by the resonant inductor can be used to charge the high-voltage capacitor of the intermediate high-frequency bus.

5. The control method of the power electronic transformer according to claim 1, characterized in that: The circuit controlling any one end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer includes: During a preset first cycle, the diode at the high-voltage side port of the power electronic transformer is controlled to be turned on based on the PWM signal, so that the high-voltage side port charges the resonant inductor of the intermediate high-frequency bus, so that the resonant inductor generates freewheeling current; After a preset first cycle time, the diode at the high-voltage side port of the power electronic transformer is closed based on the PWM signal control, so that the freewheeling current generated by the resonant inductor can be used to charge the high-voltage capacitor of the intermediate high-frequency bus.

6. The control method of the power electronic transformer according to claim 1, characterized in that: After the step of obtaining the bus voltage value of the intermediate high-frequency bus of the power electronic transformer, the method further includes: If the bus voltage value is greater than the preset first voltage value and the power electronic transformer is in a state of non-continuously sending a high level signal, the electronic components of the power electronic transformer are controlled to be locked.

7. The control method of the power electronic transformer according to claim 1, characterized in that: After the step of obtaining the bus voltage value of the intermediate high-frequency bus of the power electronic transformer, the method further includes: If the bus voltage value is greater than the preset first voltage value, the bus voltage value is greater than the preset second voltage value and the power electronic transformer continues to send a high level signal, the electronic device of the power electronic transformer is controlled to lock, and the power electronic transformer is controlled to continue to send a low level signal.

8. The control method of the power electronic transformer according to claim 1, characterized in that: Determining that the power electronic transformer is in a light load state includes: Acquire a real-time power value of the power electronic transformer, where the real-time power value is the whole machine power of the power electronic transformer in normal operation; If the real-time power value is less than the preset power value, it is determined that the power electronic transformer is in a light-load state; If the real-time power value is greater than the preset power value, it is determined that the power electronic transformer is in a non-light load state.

9. The control method of the power electronic transformer according to claim 8, characterized in that: After the step of determining that the power electronic transformer is in a non-light-load state, the method further includes: Control the power electronic transformer to perform single phase shift modulation or double phase shift modulation.

10. A control device for a power electronic transformer, characterized in that: The device comprises: A voltage acquisition module is used to acquire a bus voltage value of an intermediate high-frequency bus of the power electronic transformer when it is determined that the power electronic transformer is in a light-load state, wherein the light-load state is a state in which the power electronic transformer is in a real-time power shortage state; A first charging module, configured to control a circuit at any end of the power electronic transformer to charge an intermediate high-frequency bus of the power electronic transformer if the bus voltage value is less than a preset first voltage value; The second charging module is used to control the circuit at either end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer if the bus voltage value is greater than the preset first voltage value, the bus voltage value is less than the preset second voltage value and the power electronic transformer continues to send a high-level signal.

11. The control device for a power electronic transformer according to claim 10, characterized in that: The circuit controlling any one end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer includes: During a preset first cycle, the diode at the low-voltage side port of the power electronic transformer is controlled to conduct based on the PWM signal, so that the low-voltage side port charges the resonant inductor of the intermediate high-frequency bus, so that the resonant inductor generates freewheeling current; After a preset first cycle duration, the diode at the low-voltage side port of the power electronic transformer is closed based on the PWM signal control, so that the freewheeling current generated by the resonant inductor can be used to charge the high-voltage capacitor of the intermediate high-frequency bus.

12. The control device for a power electronic transformer according to claim 10, characterized in that: The circuit controlling any one end of the power electronic transformer to charge the intermediate high-frequency bus of the power electronic transformer includes: During a preset first cycle, the diode at the high-voltage side port of the power electronic transformer is controlled to be turned on based on the PWM signal, so that the high-voltage side port charges the resonant inductor of the intermediate high-frequency bus, so that the resonant inductor generates freewheeling current; After a preset first cycle time, the diode at the high-voltage side port of the power electronic transformer is closed based on the PWM signal control, so that the freewheeling current generated by the resonant inductor can be used to charge the high-voltage capacitor of the intermediate high-frequency bus.

13. The control device for a power electronic transformer according to claim 10, characterized in that: The device also includes: The locking module is used to control the electronic components of the power electronic transformer to lock if the bus voltage value is greater than a preset first voltage value and the power electronic transformer is in a state of non-continuously sending a high-level signal.

14. The control device for a power electronic transformer according to claim 10, characterized in that: The device also includes: The low-level module is used to control the electronic components of the power electronic transformer to be locked and control the power electronic transformer to continuously send a low-level signal if the bus voltage value is greater than a preset first voltage value, the bus voltage value is greater than a preset second voltage value and the power electronic transformer continues to send a high-level signal.

15. The control device for a power electronic transformer according to claim 10, characterized in that: Determining that the power electronic transformer is in a light load state includes: Acquire a real-time power value of the power electronic transformer, where the real-time power value is the whole machine power of the power electronic transformer in normal operation; If the real-time power value is less than the preset power value, it is determined that the power electronic transformer is in a light-load state; If the real-time power value is greater than the preset power value, it is determined that the power electronic transformer is in a non-light load state.

16. The control device for a power electronic transformer according to claim 15, characterized in that: The device also includes: The modulation module is used to control the power electronic transformer to perform single phase shift modulation or double phase shift modulation.

17. A power electronic transformer, characterized in that: The power electronic transformer comprises: a plurality of power modules, wherein the first end of the power module is a low-voltage side port, and the second end of the power module is a high-voltage side port; The low-voltage side ports of multiple power modules of the same phase are connected in parallel to access low-voltage direct current; The high-voltage side ports of multiple power modules of the same phase are connected in series for receiving high-voltage alternating current.

18. The power electronic transformer according to claim 17, characterized in that: The power module includes: four switching diodes, four high-voltage diodes, four low-voltage diodes, a high-voltage capacitor, a low-voltage capacitor, a transformer and a resonant inductor; The four switch diodes are connected to form a switch full-bridge circuit, the four high-voltage diodes are connected to form a high-voltage full-bridge circuit, and the four low-voltage diodes are connected to form a low-voltage full-bridge circuit; The high-voltage full-bridge circuit is connected to the transformer via the resonant inductor, and the transformer is connected to the low-voltage full-bridge circuit; The low-voltage full-bridge circuit is connected to the low-voltage capacitor, the switch full-bridge circuit is connected to the high-voltage full-bridge circuit via the high-voltage capacitor, and the high-voltage capacitor is arranged on the intermediate bus of the power electronic transformer.

19. An electronic device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the control method for a power electronic transformer as described in any one of claims 1 to 9 when executing the computer program.

20. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer-executable program, and the computer-executable program is used to enable a computer to execute the control method of the power electronic transformer according to any one of claims 1 to 9.

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