A voltage equalization control method for a DC transformer

Abstract

The application provides a voltage balance control method of a direct current transformer. The direct current transformer comprises at least N modules, each module comprising at least one pre-stage circuit and at least one power circuit, and based on the working states of the pre-stage circuit and the power circuit, the module serves as a normal module, a redundant module or a bypass module; the control method comprises: through the balance control of the running power of the normal module, the voltage balance of the first direct current port of the normal module is adjusted; and based on the second common direct current port, the voltage of the first direct current port of the redundant module is reversely adjusted.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to a voltage equalization control method for a DC transformer. Background Technology

[0002] As a crucial component in DC power grids for voltage transformation, DC transformers have garnered increasing attention from scholars in the field. To achieve medium / high voltage to low voltage conversion, due to the stress and cost of switching devices, bidirectional DC-DC converters for this type of application often employ a multi-module input-series-output-parallel structure (ISOP). The modules typically utilize isolated DC-DC converters based on dual active bridge (DAB) or LC resonant technology.

[0003] As voltage levels increase, the number of modules required for DC transformers also increases, leading to a decrease in system reliability. Therefore, redundant modules are necessary. However, to ensure normal system operation in DC transformers, it is usually necessary to provide a preceding circuit for all modules to achieve redundancy. Furthermore, depending on the power relationship, the operating state of all modules will change compared to when there are no redundant modules. At this point, there are two methods to configure the operating state of the redundant modules:

[0004] One approach is to operate all modules, including any added redundant modules, in the same state. In this case, the voltage at the series-connected port of all modules decreases. If an isolated DC-DC converter based on LC resonant technology is used, the lack of voltage regulation in this circuit leads to a decrease in the low-voltage side voltage, failing to meet the low-voltage side requirements. If an isolated DC-DC converter based on a dual active bridge is used, it results in voltage mismatch on both sides, thus reducing its operating efficiency. A solution is to equip the pre-amplifier circuit within the module with voltage regulation capabilities, but this undoubtedly introduces switching losses in the pre-amplifier circuit.

[0005] Another approach involves modifying the state of the pre-amplifier circuit to establish a separate hot standby state for each module. In this state, the voltage on the series-connected side of all modules remains constant, and the redundant modules maintain the hot standby state by transferring energy back through the low-voltage side. Furthermore, the pre-amplifier circuits of all modules are not in voltage regulation operation, thus eliminating switching losses. However, in this scenario, the redundant modules do not transfer power, resulting in a significant power difference compared to the other normally operating modules, posing a challenge to voltage equalization control across all modules. Summary of the Invention

[0006] This application provides a voltage equalization control method for a DC transformer. The DC transformer includes at least N modules, where N is a natural number greater than or equal to 2. Each module includes at least one front-end circuit and at least one power circuit. The front-end circuit includes a first port and a second port, and the power circuit includes a third port and a fourth port. The cascaded port of the second port of the front-end circuit and the third port of the power circuit is defined as the first DC port of the module. The first ports of all module front-end circuits are connected in series to form the first common DC port of the DC transformer, and the fourth ports of all module power circuits are connected in parallel to form the second common DC port of the DC transformer. Based on the operating states of the front-end circuit and the power circuit, the module is configured as a normal module, a redundant module, or a bypass module. The control method includes: adjusting the voltage equalization of the first DC port of the normal module by equalizing the operating power of the normal module; and adjusting the voltage of the first DC port of the redundant module in reverse based on the second common DC port.

[0007] According to some embodiments, all power circuits include at least two operating states: unlocked state and locked state; all front-end circuits include at least three operating states: engaged state, disengaged state, and locked state, with engaged state and disengaged state both belonging to the unlocked state; when all front-end circuits and power circuits are in the locked state, the DC transformer is in the shutdown state; a module where the front-end circuit is in the engaged state and the power circuit is in the unlocked state is a normal module; a module where the front-end circuit is in the disengaged state and the power circuit is in the unlocked state is a redundant module; and a module where the front-end circuit is in the disengaged state and the power circuit is in the locked state is a bypass module.

[0008] According to some embodiments, when all modules of the DC transformer consist only of normal modules, redundant modules, and bypass modules, the voltage of the first common DC port of the DC transformer is equal to the sum of the voltages of the first DC ports of all normal modules.

[0009] According to some embodiments, the front-end circuit is a half-bridge circuit, including a first switch and a second switch connected vertically; the upper end of the first switch and the lower end of the second switch constitute the second port of the front-end circuit; the upper end of the second switch and the lower end of the second switch constitute the first port of the front-end circuit; when the first switch is turned on and the second switch is turned off, the front-end circuit is in an active state; when the first switch is turned off and the second switch is turned on, the front-end circuit is in an active state; when the first switch is turned off and the second switch is turned on, the front-end circuit is in a deactivated state; when both the first and second switches are turned off, the front-end circuit is in a locked state.

[0010] According to some embodiments, the front-end circuit further includes a bypass switch, which is connected in parallel with the second switching transistor. For normal modules and redundant modules, the bypass switch is always in the open state, and for bypass modules, the bypass switch is in the closed state.

[0011] According to some embodiments, the power circuit is a dual active bridge circuit, including a first H-bridge circuit, a second H-bridge circuit, and a first AC transformer connected in sequence. The DC port of the first H-bridge circuit constitutes the third port of the power circuit; the DC port of the second H-bridge circuit constitutes the fourth port of the power circuit; when at least one switch of the first H-bridge circuit and the second H-bridge circuit is in a switching state, the power circuit is in an unlocked state; when all switches of the first H-bridge circuit and the second H-bridge circuit are in a turning-off state, the power circuit is in a locked state.

[0012] According to some embodiments, the step of adjusting the voltage balance of the first DC port of the normal module through the equalization control of the operating power of the normal module includes: sampling the first DC port voltage of all normal modules and redundant modules, the average value of the first DC port voltage of all normal modules and redundant modules is a first average value, and the average value of the first DC port voltage of all normal modules is a second average value; comparing the first DC port voltage of all normal modules with the first average value or the second average value, and generating a first equalization adjustment command corresponding to each normal module after passing through a regulator; comparing the second common DC port voltage of the DC transformer or the first common DC port voltage with a reference voltage, and generating a first common adjustment command after passing through a regulator; adding the first equalization adjustment command and the first common adjustment command corresponding to each normal module, and sending them to the power circuit of each normal module to adjust the power operation of the corresponding module.

[0013] According to some embodiments, the reverse adjustment of the voltage of the first DC port of the redundant module based on the second common DC port includes: comparing the first DC port voltage of all redundant modules with the first average value, generating a second equalization adjustment command corresponding to each redundant module after passing through a regulator; adding the second equalization adjustment command corresponding to each redundant module with a preset fixed second common adjustment command, and sending it to the power circuit of each redundant module to adjust the power operation of the corresponding module.

[0014] According to some embodiments, the reverse adjustment of the voltage of the first DC port of the redundant module based on the second common DC port includes: comparing the first DC port voltage of all redundant modules with the second average value, generating a third equalization adjustment command corresponding to each redundant module after passing through a regulator; and sending the third equalization adjustment command corresponding to each redundant module to the power circuit of each redundant module to adjust the power operation of the corresponding module.

[0015] According to some embodiments, the method further includes controlling the forward start of the DC transformer, which includes: unlocking the front-end circuits of all modules, making them all in the active state, and turning all modules into normal modules; unlocking the power circuits of all normal modules, and adjusting the second common DC port voltage of the DC transformer to the rated value through the first common adjustment command; simultaneously adjusting the first DC port voltage of all normal modules to a first average value or a second average value through the first equalization adjustment command; after converting any normal module into a redundant module, changing the first equalization adjustment command of the converted module to a second equalization adjustment command, changing the first common adjustment command of the converted module to a second common adjustment command, and adjusting the first DC port voltage of the converted module to the first average value, until the number of redundant modules reaches a first preset value.

[0016] According to some embodiments, the method further includes controlling the forward start of the DC transformer, wherein controlling the forward start of the DC transformer includes: selectively unlocking the minimum number of modules required for the DC transformer system to operate normally as normal modules; unlocking the remaining modules as redundant modules; unlocking the power circuit of the normal modules and adjusting the second common DC port voltage of the DC transformer to a rated value through a first common adjustment command; simultaneously adjusting the first DC port voltage of all the normal modules to a first average value or a second average value through a first equalization adjustment command; unlocking the power circuit of the redundant modules and adjusting the first DC port voltage of the redundant modules to a second average value through a third equalization adjustment command.

[0017] According to some embodiments, the method further includes controlling the DC transformer to start in reverse, wherein controlling the DC transformer to start in reverse includes: unlocking the power circuits of all modules; unlocking all modules as normal modules, adjusting the first common DC port voltage of the DC transformer to the rated value through a first common adjustment command, and simultaneously adjusting the first DC port voltage of all modules to a first average value or a second average value through a first equalization adjustment command; converting any normal module into a redundant module, changing the first equalization adjustment command of the converted module to a second equalization adjustment command, changing the first common adjustment command of the converted module to a second common adjustment command, and adjusting the first DC port voltage of the converted module to the first average value, until the number of redundant modules reaches a second preset value.

[0018] According to some embodiments, the method further includes controlling the DC transformer to reverse start, wherein controlling the DC transformer to reverse start includes: unlocking the power circuits of all modules; arbitrarily selecting the minimum number of modules that allow the DC transformer system to operate normally and unlocking them as normal modules; unlocking the remaining modules as redundant modules; adjusting all normal modules through a first common adjustment command to make the first common DC port voltage of the DC transformer reach the rated value, and simultaneously adjusting the first DC port voltage of all normal modules to a first average value or a second average value through a first equalization adjustment command; and adjusting the first DC port voltage of all redundant modules to a second average value through a third equalization adjustment command.

[0019] According to some embodiments, when the normal module fails, the method further includes: blocking the power circuit of the normal module that failed, and converting the normal module that failed into a bypass module; selectively converting a fault-free redundant module into a normal module, changing the second or third equalization adjustment command of the converted module into a first equalization adjustment command, changing the second common adjustment command of the converted module into a first common adjustment command, and adjusting the first DC port voltage of the converted module to a first average value or a second average value.

[0020] The technical solution provided in this application, compared to DC transformer applications without voltage regulation in the front-end circuit, can ensure stable low-voltage side voltage or maintain the voltage matching state across normal modules even when there are different numbers of redundant modules in the DC transformer system, thereby improving system operating efficiency. Compared to DC transformer applications with voltage regulation in the front-end circuit, the solution in this application eliminates the voltage regulation function of the front-end circuit, avoiding additional switching losses and improving system operating efficiency. For DC transformer applications with hot standby mode, it solves the voltage balancing problem between redundant modules and normal modules, providing necessary redundancy while ensuring the normal operation of the DC transformer system. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a DC transformer configuration according to an embodiment of this application.

[0023] Figure 2 This is a schematic diagram of a DC transformer module circuit according to an embodiment of this application.

[0024] Figure 3This is a schematic flowchart of a voltage equalization control method for a DC transformer according to an embodiment of this application.

[0025] Figure 4 yes Figure 3 A schematic diagram of a voltage balancing process for adjusting the first DC port of a normal module according to an embodiment.

[0026] Figure 5 yes Figure 3 A schematic diagram of the voltage flow at the first DC port of a reverse regulation redundant module according to an embodiment.

[0027] Figure 6 yes Figure 3 Block diagram of the voltage equalization control strategy for the DC transformer in the embodiment.

[0028] Figure 7 This is a schematic flowchart of another DC transformer voltage equalization control method according to an embodiment of this application.

[0029] Figure 8 yes Figure 7 A schematic diagram of the voltage flow at the first DC port of a reverse regulation redundant module according to an embodiment.

[0030] Figure 9 yes Figure 7 Block diagram of the voltage equalization control strategy for the DC transformer in the embodiment.

[0031] Figure 10 This is a schematic diagram of the forward startup process of a DC transformer according to an embodiment of this application.

[0032] Figure 11 This is a schematic diagram of another forward startup process of a DC transformer according to an embodiment of this application.

[0033] Figure 12 This is a schematic diagram of the reverse start-up process of a DC transformer according to an embodiment of this application.

[0034] Figure 13 This is a schematic diagram of another reverse start-up process of a DC transformer according to an embodiment of this application.

[0035] Figure 14 This is a schematic diagram of a fault control process for a DC transformer according to an embodiment of this application. Detailed Implementation

[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0037] It should be understood that the terms "comprising" and "including" used in the specification and claims of this application indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0038] Figure 1 This is a schematic diagram of a DC transformer configuration according to an embodiment of this application.

[0039] like Figure 1 As shown, the DC transformer comprises at least N modules 10, 20, ..., N0, where N is a natural number greater than or equal to 2. Each module comprises at least one pre-amplifier circuit and at least one power circuit. For example, module 10 comprises at least one pre-amplifier circuit 101 and at least one power circuit 102. Pre-amplifier circuit 101 comprises a first port 103 and a second port 104, and power circuit 102 comprises a third port 105 and a fourth port 106. The cascaded port, formed by connecting the second port 104 of pre-amplifier circuit 101 and the third port 105 of power circuit 102, is defined as the first DC port of the module. The first ports of all module pre-amplifier circuits are connected in series to form the first common DC port 01 of the DC transformer. The fourth ports of all module power circuits are connected in parallel to form the second common DC port 02 of the DC transformer. Based on the operating states of pre-amplifier circuit 101 and power circuit 102, module 10 can be a normal module, a redundant module, or a bypass module.

[0040] All power circuits include at least two operating states: unlocked and latched. All front-end circuits include at least three operating states: engaged, disengaged, and latched, with engaged and disengaged states both belonging to the unlocked state.

[0041] When all front-end circuits and power circuits are in the locked state, the DC transformer is in the off state. A module with its front-end circuit in the engaged state and its power circuit in the unlocked state is a normal module. A module with its front-end circuit in the disengaged state and its power circuit in the unlocked state is a redundant module. A module with its front-end circuit in the disengaged state and its power circuit in the locked state is a bypass module.

[0042] Figure 2 This is a schematic diagram of a DC transformer module circuit according to an embodiment of this application.

[0043] like Figure 2 As shown, the front-end circuit 101 is a half-bridge circuit, which includes a first switching transistor 1011 and a second switching transistor 1012 connected vertically.

[0044] The upper end of the first switching transistor 1011 and the lower end of the second switching transistor 1012 constitute the second port 104 of the front-end circuit 101. The upper end of the second switching transistor 1012 and the lower end of the second switching transistor 1012 constitute the first port 103 of the front-end circuit 101.

[0045] When the first switch 1011 is turned on and the second switch 1012 is turned off, the front-end circuit 101 is in the active state. When the first switch 1011 is turned off and the second switch 1012 is turned on, the front-end circuit 101 is in the deactivated state. When the first switch 1011 is turned off and the second switch 1012 is turned off, the front-end circuit 101 is in the locked state.

[0046] Optionally, the front-end circuit 101 also includes a bypass switch 1013, which is connected in parallel with the second switch 1012. For normal modules and redundant modules, the bypass switch 1013 is always in the open state, and for bypass modules, the bypass switch 1013 is in the closed state.

[0047] The power circuit 102 is a dual active bridge circuit, including a first H-bridge circuit, a first AC transformer, and a second H-bridge circuit connected in a cascaded manner.

[0048] The DC port of the first H-bridge circuit forms the third port 105 of the power circuit. The DC port of the second H-bridge circuit forms the fourth port 106 of the power circuit.

[0049] When at least one switch in the first H-bridge circuit and the second H-bridge circuit is in the switching state, the power circuit 102 is in the unlocked state. When all switches in the first H-bridge circuit and the second H-bridge circuit are in the off state, the power circuit 102 is in the latched state.

[0050] Figure 3 This is a schematic flowchart of a voltage equalization control method for a DC transformer according to an embodiment of this application.

[0051] In S10, the voltage balance of the first DC port of the normal module is adjusted by the power balancing control of the normal module operation. S10 includes steps S11-S14, such as... Figure 4 As shown.

[0052] In S11, the first DC port voltage of all normal modules and redundant modules is sampled, the average of the first DC port voltage of all normal modules and redundant modules is the first average value, and the average of the first DC port voltage of all normal modules is the second average value.

[0053] In S12, the first DC port voltage of all normal modules is compared with the first average value or the second average value, and after passing through the regulator, the first equalization adjustment command corresponding to each normal module is generated.

[0054] In S13, the voltage of the second common DC port of the DC transformer or the voltage of the first common DC port is compared with the reference voltage, and a first common regulation command is generated after passing through the regulator.

[0055] In S14, the first equalization adjustment command and the first common adjustment command corresponding to each normal module are added together and sent to the power circuit of each normal module to adjust the power operation of the corresponding module.

[0056] In S20, based on the second common DC port, the voltage of the first DC port of the redundant module is adjusted in reverse. S20 includes steps S21-S22, such as... Figure 5 As shown.

[0057] In S21, the first DC port voltage of all redundant modules is compared with the first average value, and after passing through the PI regulator, a second equalization adjustment command corresponding to each redundant module is generated.

[0058] Figure 6 For the corresponding control strategy block diagram, assume there are x normal modules and y redundant modules, satisfying x + y = N, where i represents the label of any normal module and j represents the label of any redundant module. bus_r This is the reference voltage for either the second common DC port voltage or the first common DC port voltage. bus This refers to the voltage of either the second or first common DC port. `phase_main1` is the first common power regulation command. `phase_main2` is the second common power regulation command. dc_n This is the voltage at the first DC port of a normal module. dc_u This is the voltage at the first DC port of the redundant module. av_r1 This is the first average value. Phase_c1 is the first equalization adjustment command. Phase_c2 is the second equalization adjustment command. Phasei is the final adjustment command for the normal module. Phasej is the final adjustment command for the redundant module.

[0059] In S22, the second equalization adjustment command corresponding to each redundant module and the preset fixed second common adjustment command are added together and sent to the power circuit of each redundant module to adjust the power operation of the corresponding module.

[0060] The technical solution provided in this embodiment, compared to DC transformer applications without voltage regulation in the front-end circuit, can ensure stable low-voltage side voltage or maintain the voltage matching state across the normal module even when there are different numbers of redundant modules in the DC transformer system, thereby improving system operating efficiency. Compared to DC transformer applications with voltage regulation in the front-end circuit, the solution in this application eliminates the voltage regulation function of the front-end circuit, avoiding additional switching losses and improving system operating efficiency. For DC transformer applications with hot standby mode, it solves the voltage balancing problem between redundant modules and normal modules, providing necessary redundancy while ensuring the normal operation of the DC transformer system.

[0061] Figure 7 This is a schematic flowchart of another DC transformer voltage equalization control method according to an embodiment of this application.

[0062] In S10, the voltage balance of the first DC port of the normal module is adjusted by the power balancing control of the normal module operation. S10 includes steps S11-S14, and... Figure 3 The implementation methods are the same.

[0063] In S30, based on the second common DC port, the voltage of the first DC port of the redundant module is adjusted in reverse. S30 includes steps S31-S32, such as... Figure 8 As shown.

[0064] In S23, the first DC port voltage of all redundant modules is compared with the second average value, and after passing through the PI regulator, a third equalization adjustment command corresponding to each redundant module is generated.

[0065] like Figure 9 The diagram shown is the corresponding control strategy block diagram. Assume there are x normal modules and y redundant modules, satisfying x + y = N, where i represents the label of any normal module and j represents the label of any redundant module. bus_r This is the reference voltage for either the second common DC port voltage or the first common DC port voltage. bus This refers to the voltage at the second or first common DC port. `phase_main1` is the first common power regulation command. dc_n This is the voltage at the first DC port of a normal module. dc_u This is the voltage at the first DC port of the redundant module. av_r2 This is the second average value. phase_ci is the first equalization adjustment command. phasei is the final adjustment command for the normal module. phase_c3 is the third equalization adjustment command. phasej is the final adjustment command for the redundant module, i.e., phase_c3 = phasej.

[0066] In S24, the third equalization adjustment command corresponding to each redundant module is sent to the power circuit of each redundant module to adjust the power operation of the corresponding module.

[0067] The technical solution provided in this embodiment, compared to DC transformer applications without voltage regulation in the front-end circuit, can ensure stable low-voltage side voltage or maintain the voltage matching state across the normal module even when there are different numbers of redundant modules in the DC transformer system, thereby improving system operating efficiency. Compared to DC transformer applications with voltage regulation in the front-end circuit, the solution in this application eliminates the voltage regulation function of the front-end circuit, avoiding additional switching losses and improving system operating efficiency. For DC transformer applications with hot standby mode, it solves the voltage balancing problem between redundant modules and normal modules, providing necessary redundancy while ensuring the normal operation of the DC transformer system.

[0068] Figure 10 This is a schematic diagram of the forward startup process of a DC transformer according to an embodiment of this application, including the following steps.

[0069] In S011, the pre-amplifier circuits of all modules are unlocked, putting them all into the active state, and all modules become normal modules.

[0070] In S012, the power circuits of all normal modules are unlocked, and the voltage of the second common DC port of the DC transformer is adjusted to the rated value via the first common regulation command.

[0071] In S013, the first DC port voltage of all normal modules is adjusted to either the first average value or the second average value by means of the first equalization adjustment command.

[0072] In S014, after converting any normal module into a redundant module, the first equalization adjustment command of the converted module is changed to the second equalization adjustment command, the first common adjustment command of the converted module is changed to the second common adjustment command, and the first DC port voltage of the converted module is adjusted to the first average value until the number of redundant modules reaches the first preset value.

[0073] Figure 11 This is a schematic diagram of another forward startup process of a DC transformer according to an embodiment of this application, including the following steps.

[0074] In S021, the minimum number of modules required for the DC transformer system to operate normally can be unlocked as normal modules.

[0075] In S022, the remaining modules are unlocked as redundant modules.

[0076] In S023, the power circuit of the normal module is unlocked, and the voltage of the second common DC port of the DC transformer is adjusted to the rated value through the first common adjustment command; at the same time, the voltage of the first DC port of all normal modules is adjusted to the first average value or the second average value through the first equalization adjustment command.

[0077] In S024, the power circuit of the redundant module is unlocked, and the first DC port voltage of the redundant module is adjusted to the second average value through the third equalization adjustment command.

[0078] Figure 12 This is a schematic diagram of the reverse start-up process of a DC transformer according to an embodiment of this application, including the following steps.

[0079] In S031, unlock the power circuits of all modules.

[0080] In S032, all modules are unlocked as normal modules, and the voltage of the first common DC port of the DC transformer is adjusted to the rated value through the first common adjustment command. At the same time, the voltage of the first DC port of all modules is adjusted to the first average value or the second average value through the first equalization adjustment command.

[0081] In S033, any normal module is converted into a redundant module, the first equalization adjustment command of the converted module is changed to the second equalization adjustment command, the first common adjustment command of the converted module is changed to the second common adjustment command, and the first DC port voltage of the converted module is adjusted to the first average value until the number of redundant modules reaches the second preset value.

[0082] Figure 13 This is a schematic diagram of another reverse start-up process for a DC transformer according to an embodiment of this application, including the following steps.

[0083] In S041, unlock the power circuits of all modules.

[0084] In S042, any number of modules that require the minimum number of modules to operate normally in the DC transformer system can be selected and unlocked as normal modules.

[0085] In S043, the remaining modules are unlocked as redundant modules.

[0086] In S044, all normal modules are adjusted by the first common adjustment command to make the voltage of the first common DC port of the DC transformer the rated value. At the same time, the voltage of the first DC port of all normal modules is adjusted to the first average value or the second average value by the first equalization adjustment command.

[0087] In S045, the first DC port voltage of all redundant modules is adjusted to the second average value through the third equalization adjustment command.

[0088] Figure 14This is a schematic diagram of a fault control process for a DC transformer according to an embodiment of this application, including the following steps.

[0089] In S051, when a normal module fails, the power circuit of the failed normal module is blocked, and the failed normal module is switched to a bypass module.

[0090] In S052, any fault-free redundant module is selected and converted into a normal module. The second or third equalization adjustment command of the converted module is changed to the first equalization adjustment command, the second common adjustment command of the converted module is changed to the first common adjustment command, and the first DC port voltage of the converted module is adjusted to the first average value or the second average value.

[0091] The technical solution provided in this embodiment allows for the smooth operation of the system's redundancy module when a faulty module needs to be removed from the system. Since the voltage of the redundant module can be controlled to be the same as that of the normal module, the activation or deactivation of the redundant module has a relatively small impact on the remaining normal modules. The redundancy activation or deactivation process of the system is smooth and has a small impact.

[0092] The above embodiments are only for illustrating the technical concept of this application and should not be used to limit the scope of protection of this application. Any modifications made to the technical solution based on the technical concept proposed in this application shall fall within the scope of protection of this application.

Claims

1. A voltage equalization control method for a DC transformer, wherein the DC transformer comprises at least N modules, where N is a natural number greater than or equal to 2, each module comprises at least one pre-amplifier circuit and at least one power circuit, the pre-amplifier circuit being a half-bridge circuit, comprising a bypass switch, a first switch transistor and a second switch transistor connected vertically, the pre-amplifier circuit further comprising a first port and a second port, the upper end of the first switch transistor and the lower end of the second switch transistor constituting the second port of the pre-amplifier circuit, the upper end of the second switch transistor and the lower end of the second switch transistor constituting the first port of the pre-amplifier circuit; the power circuit comprises a third port and a fourth port, the cascaded port of the second port of the pre-amplifier circuit and the third port of the power circuit being cascaded together is defined as the first DC port of the module, the first ports of all module pre-amplifier circuits are connected in series to form the first common DC port of the DC transformer, the fourth ports of all module power circuits are connected in parallel to form the second common DC port of the DC transformer, and based on the operating state of the pre-amplifier circuit and the power circuit, the module is configured as a normal module, a redundant module, or a bypass module, wherein: The module in which the front-end circuit is in the active state and the power circuit is in the unlocked state is the normal module; the module in which the front-end circuit is in the deactivated state and the power circuit is in the unlocked state is the redundant module; and the module in which the front-end circuit is in the deactivated state and the power circuit is in the locked state is the bypass module. When the first switch is on and the second switch is off, the front-end circuit is in the active state; when the first switch is off and the second switch is on, the front-end circuit is in the deactivated state; when both the first and second switches are off, the front-end circuit is in the locked state; the bypass switch is connected in parallel with the second switch. For normal modules and redundant modules, the bypass switch is always in the open state; for bypass modules, the bypass switch is in the closed state. The control method includes: The voltage balance of the first DC port of the normal module is adjusted by the power balancing control of the normal module, including: The first DC port voltage of all normal modules and redundant modules is sampled, and the average of the first DC port voltages of all normal modules and redundant modules is the first average value, and the average of the first DC port voltages of all normal modules is the second average value. The first DC port voltage of all normal modules is compared with the first average value or the second average value, and after passing through the regulator, the first equalization adjustment command corresponding to each normal module is generated. The voltage at the second common DC port of the DC transformer or the voltage at the first common DC port is compared with the reference voltage, and a first common regulation command is generated after passing through the regulator. The first equalization adjustment command and the first common adjustment command corresponding to each normal module are added together and sent to the power circuit of each normal module to adjust the power operation of the corresponding module. Based on the second common DC port, the voltage of the first DC port of the redundant module is adjusted in reverse, including: The first DC port voltage of all redundant modules is compared with the first average value, and a second equalization adjustment command corresponding to each redundant module is generated after passing through the regulator; the second equalization adjustment command corresponding to each redundant module is added to a preset fixed second common adjustment command and sent to the power circuit of each redundant module to adjust the power operation of the corresponding module; or The first DC port voltage of all redundant modules is compared with the second average value, and a third equalization adjustment command corresponding to each redundant module is generated after passing through the regulator. The third equalization adjustment command corresponding to each redundant module is sent to the power circuit of each redundant module to adjust the power operation of the corresponding module.

2. The control method as described in claim 1, wherein, All power circuits include at least two operating states: unlocked and latched. All front-end circuits include at least three operating states: engaged, disengaged, and latched. Engaged and disengaged states are both considered unlocked states. The DC transformer is in a stopped state when all front-end circuits and power circuits are in a locked state.

3. The control method as described in claim 1, wherein, When all modules of the DC transformer consist of only normal modules, redundant modules, and bypass modules, the voltage at the first common DC port of the DC transformer is equal to the sum of the voltages at the first DC ports of all normal modules.

4. The control method according to claim 1, wherein, The power circuit is a dual active bridge circuit, including: The first H-bridge circuit, the DC port of the first H-bridge circuit constitutes the third port of the power circuit; The first AC transformer is cascaded with the first H-bridge circuit; The second H-bridge circuit is cascaded with the first AC transformer, and the DC port of the second H-bridge circuit constitutes the fourth port of the power circuit. The power circuit is in an unlocked state when at least one switch in the first H-bridge circuit and the second H-bridge circuit is in a switching state; the power circuit is in a locked state when all switches in the first H-bridge circuit and the second H-bridge circuit are in a turning-off state.

5. The control method according to claim 1, further comprising: Controlling the forward start of the DC transformer includes: Unlock the pre-amplifier circuits of all modules to put them all into operation, and all modules become normal modules. Unlock the power circuits of all normal modules, and adjust the voltage of the second common DC port of the DC transformer to the rated value using the first common adjustment command; Simultaneously, the first DC port voltage of all normal modules is adjusted to either the first average value or the second average value using the first equalization adjustment command. After converting any normal module into a redundant module, the first equalization adjustment command of the converted module is changed to the second equalization adjustment command, the first common adjustment command of the converted module is changed to the second common adjustment command, and the first DC port voltage of the converted module is adjusted to the first average value until the number of redundant modules reaches the first preset value.

6. The control method according to claim 1, further comprising: Controlling the forward start of the DC transformer includes: Choose any number of modules that allow the DC transformer system to operate normally to be unlocked as normal modules; Unlock the remaining modules as redundant modules; Unlock the power circuit of the normal module, and adjust the voltage of the second common DC port of the DC transformer to the rated value through the first common adjustment command; at the same time, adjust the voltage of the first DC port of all the normal modules to the first average value or the second average value through the first equalization adjustment command. Unlock the power circuit of the redundant module, and adjust the first DC port voltage of the redundant module to the second average value through the third equalization adjustment command.

7. The control method according to claim 1, further comprising: Controlling the reverse start of the DC transformer includes: Unlock the power circuits of all modules; Unlock all modules as normal modules, adjust the first common DC port voltage of the DC transformer to the rated value through the first common adjustment command, and at the same time adjust the first DC port voltage of all modules to the first average value or the second average value through the first equalization adjustment command. Convert any normal module into a redundant module, change the first equalization adjustment command of the converted module to the second equalization adjustment command, change the first common adjustment command of the converted module to the second common adjustment command, and adjust the first DC port voltage of the converted module to the first average value until the number of redundant modules reaches the second preset value.

8. The control method according to claim 1, further comprising: Controlling the reverse start of the DC transformer includes: Unlock the power circuits of all modules; Arbitrarily select the minimum number of modules required for the DC transformer system to operate normally, and unlock them as normal modules; Unlock the remaining modules as redundant modules; The first common adjustment command is used to adjust all normal modules so that the voltage of the first common DC port of the DC transformer is at the rated value. At the same time, the first equalization adjustment command is used to adjust the voltage of the first DC port of all normal modules to the first average value or the second average value. The third equalization adjustment command adjusts the first DC port voltage of all redundant modules to the second average value.

9. The control method according to claim 1, wherein, When the normal module malfunctions, the method further includes: The power circuit of the normal module that has failed is locked out, and the normal module that has failed is switched to a bypass module. Select any fault-free redundant module to convert into a normal module, change the second or third equalization adjustment command of the converted module to the first equalization adjustment command, change the second common adjustment command of the converted module to the first common adjustment command, and adjust the first DC port voltage of the converted module to the first average value or the second average value.

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