Solid state transformer power cell cyclo-inversion modulation method, system and storage medium

Abstract

The embodiment of the application provides a solid-state transformer power unit rotation modulation method, system and storage medium, and belongs to the technical field of solid-state transformer control. The method comprises the following steps: acquiring unit operation information of each power unit, determining a target rotation unit pair according to the unit operation information, determining a handover waiting interval according to the unit operation information of the target rotation unit pair, determining a rotation influence parameter corresponding to each candidate handover time according to the modulation state of the target rotation unit pair in the handover waiting interval, and determining a target handover time according to the rotation influence parameter, and exchanging the modulation roles of the target rotation unit pair at the target handover time, and updating the unit operation information of each power unit. The scheme of the application realizes low disturbance rotation of the high-frequency modulation role of the power unit of the solid-state transformer, reduces the additional switching action generated by rotation, and balances the long-term operation burden of each power unit.

Description

Technical Field

[0001] This invention relates to the field of solid-state transformer control technology, and more specifically to a method, system, and storage medium for switching modulation of solid-state transformer power units. Background Technology

[0002] Solid-state transformers typically consist of multiple cascaded power units, each achieving power conversion and output modulation through the periodic switching of power devices. In actual operation, the modulation tasks undertaken by different power units are not always completely consistent. Some power units may continuously perform high-frequency switching operations for extended periods, causing their cumulative switching frequency, conduction duration, and device temperature to gradually exceed those of other power units. Over long-term operation, significant differences in operating load can easily emerge between different power units.

[0003] To mitigate these discrepancies, existing technologies typically employ fixed-period rotation, preset sequence switching, or adjustments to modulation tasks based on unit operating states, allowing different power units to alternately undertake high-frequency modulation tasks. While this approach can alleviate the long-term load concentration problem to some extent, in actual rotation processes, the switching time of modulation tasks is usually directly triggered by a fixed period or rotation conditions, and the switching states of the power unit to be switched out and the power unit to be switched in may not be consistent at that moment. Directly switching modulation roles could cause power devices that would not otherwise require state changes to perform additional switching actions, and could also cause instantaneous changes in cascaded outputs, thus creating a new switching burden within the rotation process itself.

[0004] Therefore, how to reduce the additional switching actions and output disturbances generated during the modulation role switching process while realizing the rotation of the power unit operation load is an urgent problem to be solved in the power unit rotation modulation process of solid-state transformers. Summary of the Invention

[0005] The purpose of this invention is to provide a solid-state transformer power unit switching modulation method, system, and storage medium to at least solve the problem of additional switching actions and output disturbances generated during the power unit modulation role switching process.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for switching modulation of power units in a solid-state transformer, the method comprising: Obtain the unit operation information of each power unit, and determine the target rotation unit pair based on the unit operation information; The handover waiting interval is determined based on the unit operation information of the target rotation unit pair; Within the handover waiting interval, the rotation influence parameters corresponding to each candidate handover time are determined according to the modulation state of the target rotation unit pair, and the target handover time is determined according to the rotation influence parameters. At the target handover time, the modulation roles of the target switching unit pairs are exchanged, and the unit operation information of each power unit is updated.

[0007] A second aspect of the present invention provides a solid-state transformer power unit switching modulation system, the system comprising: The data acquisition unit is used to acquire the unit operation information of each power unit and determine the target rotation unit pair based on the unit operation information; An interval determination unit is used to determine a handover waiting interval based on the unit operation information of the target rotation unit pair; A time determination unit is used to determine the rotation influence parameters corresponding to each candidate handover time according to the modulation state of the target rotation unit pair within the handover waiting interval, and to determine the target handover time according to the rotation influence parameters. An execution unit is used to exchange the modulation roles of the target switching unit pairs at the target handover time and update the unit operation information of each power unit.

[0008] On the other hand, the present invention provides a computer-readable storage medium storing instructions that, when executed on a computer, cause the computer to perform the above-described solid-state transformer power unit switching modulation method.

[0009] Through the above technical solution, this invention determines the target switching unit pair by acquiring the unit operation information of each power unit, enabling targeted adjustments to the high-frequency modulation task among power units with switching requirements. Furthermore, it determines the handover waiting interval based on the operating status of the target switching unit pair, and evaluates the switching impact corresponding to different candidate handover times within this interval, thereby avoiding immediate modulation role switching based solely on a fixed cycle or switching condition trigger. By selecting a target handover time with minimal switching impact to complete the modulation role exchange, it can balance the high-frequency modulation load of each power unit while reducing additional switching actions during role handover, thus lowering instantaneous output disturbances caused by switching. After the switching is completed, the unit operation information of each power unit is updated, providing new judgment criteria for subsequent switching, thereby forming a continuous closed-loop power unit switching modulation process.

[0010] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0011] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart of the steps of a solid-state transformer power unit switching modulation method provided in one embodiment of the present invention; Figure 2 This is a detailed flowchart of step S20 of the solid-state transformer power unit switching modulation method provided in one embodiment of the present invention; Figure 3 This is a detailed flowchart of step S30 of the solid-state transformer power unit switching modulation method provided in one embodiment of the present invention; Figure 4 This is a schematic diagram of the switching modulation principle of a solid-state transformer power unit provided in one embodiment of the present invention; Figure 5 This is a schematic diagram showing the distribution of the cumulative number of switching times before and after the power unit rotation, provided by one embodiment of the present invention; Figure 6 This is a system structure diagram of a solid-state transformer power unit switching modulation system provided in one embodiment of the present invention. Detailed Implementation

[0012] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0013] like Figure 1 As shown, embodiments of the present invention provide a method for alternating modulation of solid-state transformer power units, the method comprising: Step S10: Obtain the unit operation information of each power unit, and determine the target rotation unit pair based on the unit operation information.

[0014] In this embodiment of the invention, each power unit participating in the same switching process is a power unit with modulation role interchangeability conditions. These power units are located in the same phase or the same cascaded branch, and have the same power topology and corresponding modulation function, ensuring that any power unit assuming the corresponding modulation role can generate the corresponding output according to the current modulation reference value. Power units in different phases, different converter stages, or without modulation role interchangeability conditions do not participate in the determination of the same target switching unit pair.

[0015] Specifically, obtaining the unit operation information of each power unit includes: the cumulative on-time, cumulative switching count, device temperature, current modulation role, and DC-side voltage of each power unit; determining the target switching unit pair based on the unit operation information includes: determining the power unit to be switched out and the power unit to be switched in based on the current modulation role, cumulative on-time, cumulative switching count, and device temperature; and determining the target switching unit pair based on the DC-side voltage of each of the power units to be switched out and the power units to be switched in.

[0016] In this embodiment of the invention, the cumulative on-time is the cumulative time the power unit has been in the power on-state since the preset operating statistical start point; the cumulative switching count is the cumulative number of actual on- and off-state transitions of the corresponding power device since the preset operating statistical start point; and the device temperature is the current temperature of the target power device or its corresponding heat dissipation location in the power unit. The current modulation role is used to characterize whether the corresponding power unit is currently undertaking a high-frequency modulation task, and the DC-side voltage is used to characterize the current DC-side operating state of the corresponding power unit.

[0017] Power units are categorized into those performing high-frequency modulation tasks and those not, based on their current modulation roles. A rotation priority is determined by considering cumulative on-time, cumulative switching counts, and device temperature. High-frequency modulation power units with more cumulative switching counts are prioritized as replacement power units. When the difference in cumulative switching counts is less than a preset threshold, the replacement power unit is further determined based on cumulative on-time and device temperature. For example, among two power units being compared, 5% of the larger cumulative switching count is set as the preset threshold. When the difference in cumulative switching counts between the two power units is below this threshold, the power unit with a longer cumulative on-time and higher device temperature is prioritized as the replacement power unit. For power units not performing high-frequency modulation tasks, power units with fewer cumulative switching counts, shorter cumulative on-time, and lower device temperature are prioritized as the replacement power units.

[0018] Further compare the DC-side voltages of the power unit to be swapped out and the power unit to be swapped in. When the difference between their DC-side voltages meets the preset role-swapping voltage condition, they are identified as the target rotation unit pair. When the preset role-swapping voltage condition is not met, the next power unit to be swapped in is determined according to the aforementioned rotation priority relationship, and the DC-side voltage comparison is performed again. If there is currently no power unit to be swapped in that meets the preset role-swapping voltage condition, the current rotation judgment ends, and the unit operation information of each power unit is reacquired in the next rotation check cycle. For example, the preset role-swapping voltage condition is set to the absolute value of the difference between the DC-side voltages of the power unit to be swapped out and the power unit to be swapped in not exceeding 3% of the rated DC-side voltage. The above values ​​are only used to illustrate specific implementation methods; in actual applications, they are preset according to the rated voltage of the power unit and the allowable output fluctuation range.

[0019] Step S20: Determine the handover waiting interval based on the unit operation information of the target rotation unit pair.

[0020] Specifically, based on the current device temperature of the power unit to be replaced in the target switching unit, the allowed waiting time to maintain the current modulation role is determined, and a corresponding handover waiting interval is formed starting from the current moment. This handover waiting interval limits the search range of subsequent candidate handover moments, shortening the waiting process when the device temperature is high and preserving appropriate handover selection space when the device temperature is low, thus providing a time boundary for subsequently determining the target handover moment with minimal impact from the switching. For example... Figure 2 Step S20 includes the following steps: Step S201: Obtain the device temperature of the power unit to be replaced in the target switching unit.

[0021] Specifically, based on the unit identifier corresponding to the power unit to be replaced in the target switching unit, the corresponding device temperature is extracted from the unit operation information. The device temperature uses the same temperature acquisition location and temperature characterization method as the aforementioned unit operation information to ensure the comparability of temperature data in different switching cycles.

[0022] In one specific embodiment, the estimated junction temperature of the main power device performing high-frequency switching in the power unit to be replaced is used as the device temperature. When the heat sink or device housing temperature is used for characterization, the same sampling location and sampling rules are maintained in each rotation cycle. Further, the validity of the temperature sampling value corresponding to the current rotation check moment is verified, and the most recent valid temperature value is determined as the device temperature of the power unit to be replaced. The device temperature is used to subsequently determine the allowable waiting time, and its specific acquisition method does not constitute a limitation on the form of temperature detection.

[0023] Step S202: Determine the allowable waiting time corresponding to the device temperature.

[0024] Specifically, the higher the device temperature, the shorter the allowable waiting time. A temperature margin is determined based on a preset rotation temperature and the device temperature; a preset margin range to which the temperature margin belongs is determined, and a baseline waiting time corresponding to the preset margin range is obtained; the baseline waiting time is reduced based on the position of the temperature margin within the preset margin range to obtain the allowable waiting time.

[0025] In this embodiment of the invention, the preset switching temperature is a pre-set switching temperature reference value, used to adjust the waiting time for the power device to continue performing its current high-frequency modulation role before it reaches its allowable operating temperature. The preset switching temperature is lower than the allowable operating temperature of the corresponding power device. The temperature margin is used to characterize the remaining temperature space of the current device temperature relative to the preset switching temperature. Specifically, the difference between the preset switching temperature and the current device temperature is determined as the temperature margin, and multiple preset margin intervals are pre-set according to different temperature margins, each preset margin interval corresponding to a baseline waiting time.

[0026] For example, the preset switching temperature is set to 90℃, and the temperature margin is divided into four preset margin ranges: greater than 15℃, 8℃ to 15℃, 3℃ to 8℃, and less than 3℃. The corresponding reference waiting times are set to 20, 12, 6, and 2 carrier cycles, respectively. When the device temperature of the power unit to be replaced is 84℃, the corresponding temperature margin is 6℃. Therefore, it enters the preset margin range of 3℃ to 8℃, and obtains 6 carrier cycles as the corresponding reference waiting time.

[0027] Furthermore, the reference waiting time is reduced based on the position of the temperature margin within the current preset margin range. The closer the temperature margin is to the lower boundary of the preset margin range, the closer the device temperature is to the preset rotation temperature, and the greater the reduction; the closer the temperature margin is to the upper boundary of the preset margin range, the smaller the reduction. In the embodiment where the temperature margin is 6°C, based on its position within the 3°C to 8°C range, the reference waiting time of 6 carrier cycles is reduced to 4 carrier cycles, and 4 carrier cycles are determined as the allowable waiting time.

[0028] By using a margin range to determine the baseline waiting time, and then refining and reducing it based on the position within the range, the subsequent handover search time is compressed when the device temperature is high, while time and space are reserved to find handover moments with lower rotation impacts when the temperature margin is large. The temperature values, range boundaries, and number of carrier cycles mentioned above are used to illustrate the specific implementation method. The actual settings are predetermined based on the allowable operating temperature of the power device, the switching frequency, and the thermal response characteristics.

[0029] Step S203: Determine the handover waiting interval based on the current time and the allowed waiting time.

[0030] Specifically, the current rotation check time is determined as the start time of the handover waiting interval, and the end time of the handover waiting interval is determined according to the allowed waiting time obtained in step S202, thereby limiting the search range of subsequent candidate handover times. The current time corresponds to the current modulation time after the target rotation unit pair is determined. In actual processing, it is aligned to the first carrier cycle boundary after the current time to avoid starting the modulation role handover judgment directly in the middle of the carrier cycle.

[0031] In one specific embodiment, when the current rotation check time is t0 and the allowable waiting time determined in step S202 is 4 carrier cycles, the boundary of the first complete carrier cycle after t0 is taken as the starting point of the handover waiting interval, and the time range covered by 4 consecutive carrier cycles is determined as the handover waiting interval. Subsequently, each carrier cycle boundary within this handover waiting interval is selected as a candidate handover time to further determine the corresponding rotation impact parameters.

[0032] By defining a handover waiting interval, the subsequent handover time search ensures that it does not exceed the allowable waiting range of the current temperature state of the power unit to be replaced, while also preserving multiple complete carrier boundaries for comparison of rotation effects. The above implementation method, which determines the start and end positions of the interval based on carrier period boundaries, ensures the continuity of the modulation process, and the actual length of the handover waiting interval is determined by the aforementioned allowable waiting time.

[0033] Step S30: Within the handover waiting interval, determine the rotation influence parameters corresponding to each candidate handover time according to the modulation state of the target rotation unit pair, and determine the target handover time according to the rotation influence parameters.

[0034] Within the handover waiting interval, multiple candidate handover times are determined according to the carrier period boundary, and the modulation state of the target switching unit pair at each candidate handover time is obtained. The switching and output changes during maintaining the current modulation role and during modulation role switching are analyzed to obtain the switching impact parameters corresponding to each candidate handover time. Based on these switching impact parameters, candidate handover times with output changes exceeding the allowable range are eliminated. From the remaining candidate handover times, the time with fewer additional switching actions during switching is preferentially selected as the target handover time to reduce the additional switching burden and instantaneous output disturbances generated during the modulation role switching process. Figure 3 Step S30 includes the following steps: Step S301: Determine multiple candidate handover times within the handover waiting interval, and obtain the modulation reference quantity and switching state corresponding to each candidate handover time. Determine the modulation state of the target switching unit pair at each candidate handover time based on the modulation reference quantity and switching state.

[0035] Specifically, within the handover waiting interval determined in step S203, the boundary times corresponding to each complete carrier cycle are sequentially determined as candidate handover times to avoid changing the modulation role within a single carrier cycle and thus disrupting the integrity of the original PWM pulse. For each candidate handover time, the modulation reference quantity corresponding to that time and the current switching states of the power units to be switched out and the power units to be switched in in the target switching unit pair are obtained. The modulation reference quantity is a reference quantity used to determine the target output state of the power units during the current modulation control process, and the switching state is used to characterize the on or off state of the power devices corresponding to each power unit before the candidate handover time arrives. The modulation reference quantity corresponding to each candidate handover time is correlated with the switching state of the target switching unit pair to determine the modulation state of the target switching unit pair at each candidate handover time. The modulation state is used to characterize the current modulation operation of the target switching unit pair at the corresponding candidate handover time.

[0036] In one specific embodiment, the handover waiting interval covers four carrier cycles. The boundaries of these four consecutive carrier cycles within this interval are then defined as candidate handover times t1, t2, t3, and t4, respectively. The modulation reference values ​​and the current switching state of the target rotation unit pair corresponding to each candidate handover time are recorded. The acquired modulation reference values ​​and switching states remain consistent with the data definitions used in the current normal modulation process, without altering the original modulation algorithm. These candidate handover times are used to subsequently deduce the switching sequences when maintaining the current modulation role and when exchanging modulation roles, thereby providing a unified starting point for determining the rotation impact parameters.

[0037] Step S302: Based on the modulation state corresponding to each candidate handover time, determine the switching sequence corresponding to the target rotation unit pair when maintaining the current modulation role and when exchanging modulation roles.

[0038] Specifically, based on the modulation reference quantity in the modulation state corresponding to each candidate handover time and the current modulation role of the target rotation unit pair, the target modulation state after each candidate handover time is predicted; based on the switch state in the modulation state corresponding to each candidate handover time and the target modulation state, the hold state switch sequence corresponding to the target rotation unit pair when maintaining the current modulation role is determined; based on the target modulation state after exchanging the modulation roles of the target rotation unit pair and the switch state in the modulation state corresponding to each candidate handover time, the corresponding rotation state switch sequence is determined.

[0039] In this embodiment of the invention, for each candidate handover time, the target modulation state within a preset analysis period after the candidate handover time is first predicted according to the modulation reference quantity corresponding to the candidate handover time and the modulation role currently undertaken by the target switching unit, based on the existing modulation rules of the current solid-state transformer. The target modulation state is used to characterize the output state that the power unit to be switched out and the power unit to be switched in should achieve under the corresponding modulation role, without changing the current modulation reference quantity and the original modulation rules.

[0040] While maintaining the current modulation role, using the switch state obtained in step S301 as the starting state, the switching change process of the target switching unit within the preset analysis period is predicted according to the target modulation state to obtain the holding state switch sequence. Subsequently, without changing the modulation reference value, the modulation roles corresponding to the power unit to be switched out and the power unit to be switched in are hypothetically swapped, and the target modulation state within the same preset analysis period is re-predicted according to the swapped modulation roles; then, using the same switch state as the starting state, the corresponding switching state switch sequence is determined.

[0041] For example, a carrier cycle following the candidate handover time is used as the preset analysis period. The power unit to be switched out currently assumes a high-frequency modulation role, while the power unit to be switched in assumes a low-frequency modulation role. The state switch sequence is generated according to the original role mapping, and the rotation state switch sequence is generated according to the mapping after the role exchange. Both switch sequences use the same candidate handover time, modulation reference value, and initial switch state, only changing the modulation role correspondence. This ensures that the subsequent rotation additional switch count and rotation voltage increment can reflect the impact of the role exchange itself. The preset analysis period is determined in advance based on the actual modulation frequency; this embodiment uses one carrier cycle for illustration.

[0042] Step S303: Determine the number of additional switching cycles corresponding to each candidate handover time based on the two switching sequences, and determine the corresponding switching voltage increment based on the DC side voltage of the target switching unit pair and the two switching sequences.

[0043] Specifically, for the same candidate handover time, the hold state switch sequence and the rotation state switch sequence obtained in step S302 are aligned according to the corresponding power devices and time positions, and the state transition events in the two switch sequences are determined respectively. State transition events present in the rotation state switch sequence but not present at the corresponding position in the hold state switch sequence are determined as new state transition events, and the number of these new state transition events is determined as the rotation additional switch count. When the rotation state switch sequence does not have any new state transition events relative to the hold state switch sequence, the rotation additional switch count is recorded as zero, indicating that no additional switching action is generated due to the modulation role exchange at this candidate handover time.

[0044] Furthermore, based on the DC-side voltages of the power units to be switched out and the power units to be switched in, and the output states in the corresponding switching sequences, the combined output voltages of the target switching unit pairs are determined when maintaining the current modulation role and when switching modulation roles, respectively. The maximum difference between the two combined output voltages at the same sampling position is determined as the switching voltage increment. For example, within a preset analysis period of one carrier cycle, the combined output voltages corresponding to the holding state are 0, Udc, and 0 in sequence. When the switching state corresponds to 0, Udc, and 0, the switching voltage increment is 0. If an additional voltage step occurs at one of the sampling positions, the voltage difference corresponding to that position is used as the switching voltage increment. Thus, the additional switching number during switching is used to characterize the increased switching burden of switching, and the switching voltage increment is used to characterize the impact of switching on the instantaneous output state.

[0045] Step S304: Use the number of additional switching cycles and the voltage increment during the switching cycle as the switching influence parameters.

[0046] Specifically, the number of additional switching operations and the switching voltage increment obtained in step S303 are correlated according to the corresponding candidate handover times to form the switching impact parameters corresponding to each candidate handover time. The number of additional switching operations is used to characterize the number of additional switching actions performed at the corresponding candidate handover time compared to maintaining the current modulation role, and the switching voltage increment is used to characterize the degree of instantaneous change in the combined output voltage of the target switching unit caused by the modulation role exchange.

[0047] In one specific embodiment, the candidate handover time t1 corresponds to 0 additional switching cycles and a voltage increment of 5V. Therefore, 0 cycles and 5V are used together as the handover influence parameter for t1. The candidate handover time t2 corresponds to 2 additional switching cycles and a voltage increment of 2V, thus forming the handover influence parameter for t2. These handover influence parameters are recorded separately as two evaluation quantities, without being weighted and combined into a single evaluation value, to avoid the weighting of different physical quantities affecting subsequent judgments. Subsequently, candidate handover times that meet the output change requirements are first determined based on the voltage increment, and then filtered based on the number of additional switching cycles, thereby providing a direct basis for determining the target handover time.

[0048] Step S305: Determine the target handover time based on the rotation impact parameters.

[0049] Specifically, the candidate handover time when the switching voltage increment is within a preset allowable voltage range is determined as the candidate safe handover time; the candidate safe handover time with the fewest number of switching additional switches is selected from the candidate safe handover times; and the earliest candidate safe handover time among the selected candidate safe handover times is determined as the target handover time.

[0050] In this embodiment of the invention, safety screening is performed based on the alternating voltage increment corresponding to each candidate handover moment. The preset allowable voltage range is used to limit the maximum allowable instantaneous change in the combined output voltage caused by the modulation role exchange of the target alternating unit. Its specific value is preset based on the rated DC side voltage of the power unit and the allowable output voltage fluctuation range of the solid-state transformer. For example, when the rated DC side voltage of a single power unit is 800V, the preset allowable voltage range is set to not exceed 2% of the rated DC side voltage, that is, the alternating voltage increment is not greater than 16V. The candidate handover moment that meets this condition is determined as the candidate safe handover moment, and the remaining candidate handover moments are excluded to avoid introducing large instantaneous output changes in order to reduce switching operations.

[0051] After obtaining the candidate safe handover times, the number of additional switch rotations corresponding to each candidate safe handover time is further compared, and the candidate safe handover time with the fewest additional switch rotations is retained. For example, the alternating voltage increments corresponding to candidate handover times t1, t2, and t3 are 8V, 12V, and 20V, respectively, and the corresponding number of additional switch rotations are 2, 0, and 0 times, respectively. When the preset allowable voltage range is 16V, t1 and t2 are determined as candidate safe handover times, and t3 is excluded; after further comparison, t2, with 0 additional switch rotations, is retained.

[0052] When there are two or more candidate safe handover times with the same number of additional switching operations and both being the minimum, the candidate safe handover time closest to the current time is determined as the target handover time, in chronological order. This shortens the time the power unit to be switched out continues to assume the current modulation role while meeting output change limits and reducing additional switching operations. If there is no candidate safe handover time within the current handover waiting interval that meets the preset allowable voltage range, the target handover time is not determined for this round, and the unit operating information is reacquired in subsequent rotation check cycles to avoid forcibly executing modulation role switching when output safety conditions are not met.

[0053] Preferably, taking the target handover time as the center, one adjacent time is selected forward and one adjacent time is selected according to a preset control sampling interval. Based on the modulation reference quantity, switch state, and role exchange rules obtained in step S302, the number of additional switching operations and the voltage increment corresponding to the adjacent time are determined respectively. When the voltage increments corresponding to the two adjacent times are both within the preset allowable voltage range, and the number of additional switching operations does not exceed the preset increment of the number corresponding to the target handover time, the target handover time remains unchanged; otherwise, the target handover time is re-determined from the remaining candidate safe handover times according to the number of additional switching operations from least to most and the time from earliest to latest.

[0054] Step S40: At the target handover time, exchange the modulation roles of the target switching unit pair and update the unit operation information of each power unit.

[0055] Specifically, at the target handover time, the high-frequency modulation role of the power unit to be replaced is switched to the power unit to be replaced, and the modulation role of the power unit to be replaced is adjusted; the actual conduction time, actual switching count, and device temperature of each power unit after the modulation role exchange are obtained; the corresponding cumulative conduction time and cumulative switching count are updated according to the actual conduction time and actual switching count, and the unit operation information is updated according to the device temperature and the modulation role after the exchange.

[0056] In this embodiment of the invention, when the target handover time determined in step S305 arrives, the current modulation reference value and the original modulation rules of each power unit remain unchanged. The high-frequency modulation role currently undertaken by the power unit to be replaced is switched to the power unit to be replaced, and the power unit to be replaced is adjusted to the modulation role corresponding to the power unit to be replaced before the role exchange. The modulation role exchange only changes the correspondence between the target rotation unit pair and the existing modulation role, without changing the modulation frequency, modulation reference value, and basic topology of the power unit currently used by the solid-state transformer, thereby ensuring that the overall modulation target remains consistent before and after the rotation.

[0057] After the modulation role exchange is completed, the actual conduction time and actual switching count of each power unit are recorded using the same statistical caliber as in step S10. The actual conduction time is the cumulative time the corresponding power unit is in the power conduction state within the current statistical period, and the actual switching count is the number of times the corresponding power device actually undergoes state transitions within that statistical period. The actual conduction time is added to the cumulative conduction time before the exchange, and the actual switching count is added to the cumulative switching count before the exchange. Simultaneously, the current device temperature of each power unit is acquired.

[0058] In one specific embodiment, after the power unit A to be replaced and the power unit B to be replaced complete their role exchange, if the actual switching count of A in the subsequent statistical period is 120 times and the actual switching count of B is 480 times, then these counts are added to the original cumulative switching counts of A and B, respectively, and the cumulative conduction time is updated in the same way. Furthermore, the current device temperature, the modulation role after the exchange, and the original DC-side voltage information are jointly updated to the corresponding unit operating information. The updated unit operating information serves as the basis for determining the target rotation unit pair in the next round, thus forming a continuous rotation modulation closed loop. The aforementioned statistical period is preset based on the actual modulation frequency and rotation check period, and is not limited to a fixed time length.

[0059] Preferably, the minimum role retention time after this rotation is determined based on the device temperature change of the power unit to be replaced before and after the role exchange, and the actual number of switching operations of the power unit to be replaced after the exchange. Within this minimum role retention time, the target rotation unit maintains its current modulation role unchanged. The minimum role retention time limits the shortest interval between two adjacent rotations. For example, when the temperature of the power unit to be replaced is still in a high range, its retention time after exiting the high-frequency modulation role is appropriately extended; when the actual number of switching operations of the power unit to be replaced does not show an abnormal increase after the exchange, the current role is maintained until the end of the role retention interval. After the role retention interval ends, the next round of target rotation unit judgment is entered based on the updated unit operation information, thereby reducing invalid role jitter caused by repeated switching in and out within a short period.

[0060] In one specific embodiment, the solid-state transformer in the same cascade branch includes power units 1 to 4. Each power unit continuously records the cumulative on-time, cumulative switching count, and device temperature according to its current modulation role. Figure 4 As shown, the power units to be switched out and the power units to be switched in are determined based on the above unit operation information, and the handover waiting interval is limited according to the device temperature of the power unit to be switched out. Within the handover waiting interval, the boundary of each carrier period is used as the candidate handover time, and the switch sequences corresponding to maintaining the current modulation role and switching the modulation role are generated respectively. The target handover time is determined according to the number of additional switches and the increment of the switching voltage, and the modulation role exchange is completed at the target handover time. Then, the unit operation information of each power unit is updated.

[0061] Furthermore, the change in the cumulative number of switching operations for each power unit is as follows: Figure 5 As shown. Among them, Figure 5 In the figure, A represents the cumulative switching number distribution when no modulation role rotation is performed. Power unit 1 undertakes more high-frequency modulation tasks for a long time, and its cumulative switching number increases significantly faster than other power units. As the running time increases, the differences between the units gradually widen. Figure 5In this embodiment, B represents the cumulative switching frequency distribution after alternating modulation. During the alternation phases corresponding to t1, t2, and t3, the power unit responsible for high-frequency modulation is changed, causing different power units to bear higher switching loads at different times. Therefore, while the cumulative switching frequency curves still maintain monotonically increasing, their growth rates alternate. Around t4, the cumulative switching frequency of each power unit tends to converge, thus limiting the long-term concentration of high-frequency switching load on a subset of power units.

[0062] like Figure 6 As shown, this invention provides a solid-state transformer power unit switching modulation system. The system includes: a data acquisition unit, used to acquire unit operation information of each power unit and determine a target switching unit pair based on the unit operation information; an interval determination unit, used to determine a handover waiting interval based on the unit operation information of the target switching unit pair; a time determination unit, used to determine the switching influence parameters corresponding to each candidate handover time based on the modulation state of the target switching unit pair within the handover waiting interval, and determine the target handover time based on the switching influence parameters; and an execution unit, used to exchange the modulation roles of the target switching unit pair at the target handover time and update the unit operation information of each power unit.

[0063] The present invention also provides a computer-readable storage medium storing instructions that, when executed on a computer, cause the computer to perform the above-described solid-state transformer power unit switching modulation method.

[0064] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a microcontroller, chip, or processor to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0065] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details described above. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not further describe the various possible combinations.

[0066] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the embodiments of the present invention, they should also be regarded as the content disclosed by the embodiments of the present invention.

Claims

1. A method for alternating modulation of power units in a solid-state transformer, characterized in that, The method includes: Obtain the unit operation information of each power unit, and determine the target rotation unit pair based on the unit operation information; The handover waiting interval is determined based on the unit operation information of the target rotation unit pair; Within the handover waiting interval, the rotation influence parameters corresponding to each candidate handover time are determined according to the modulation state of the target rotation unit pair, and the target handover time is determined according to the rotation influence parameters. At the target handover time, the modulation roles of the target switching unit pairs are exchanged, and the unit operation information of each power unit is updated.

2. The solid-state transformer power unit switching modulation method according to claim 1, characterized in that, The unit operation information obtained for each power unit includes: the cumulative on-time, cumulative switching count, device temperature, current modulation role, and DC side voltage of each power unit; Determining the target rotation unit pair based on the unit operation information includes: Based on the current modulation role, cumulative on-time, cumulative switching count, and device temperature, determine the power unit to be replaced and the power unit to be replaced. The target switching unit pair is determined based on the DC-side voltage of the power unit to be switched out and the power unit to be switched in.

3. The solid-state transformer power unit switching modulation method according to claim 2, characterized in that, The handover waiting interval is determined based on the unit operation information of the target rotation unit pair, including: Obtain the device temperature of the power unit to be replaced in the target switching unit; Determine the allowable waiting time corresponding to the device temperature, wherein the higher the device temperature, the shorter the allowable waiting time; The handover waiting interval is determined based on the current time and the allowed waiting time.

4. The solid-state transformer power unit switching modulation method according to claim 3, characterized in that, Determining the allowable waiting time corresponding to the device temperature includes: The temperature margin is determined based on the preset rotation temperature and the temperature of the device. Determine the preset margin range to which the temperature margin belongs, and obtain the benchmark waiting time corresponding to the preset margin range; The baseline waiting time is reduced based on the position of the temperature margin within the preset margin range to obtain the allowable waiting time.

5. The solid-state transformer power unit switching modulation method according to claim 2, characterized in that, Within the handover waiting interval, the rotation impact parameters corresponding to each candidate handover time are determined based on the modulation state of the target rotation unit pair, including: Multiple candidate handover times are determined within the handover waiting interval, and the modulation reference quantity and switching state corresponding to each candidate handover time are obtained. The modulation state of the target switching unit pair at each candidate handover time is determined based on the modulation reference quantity and switching state. Based on the modulation state corresponding to each of the candidate handover times, the switching sequences corresponding to the target rotation unit pairs when maintaining the current modulation role and when exchanging modulation roles are determined respectively; The number of additional switching cycles corresponding to each candidate handover time is determined based on the two switching sequences, and the corresponding switching voltage increment is determined based on the DC side voltage of the target switching unit pair and the two switching sequences. The number of additional switching cycles and the voltage increment during the switching cycle are used as the switching influence parameters.

6. The solid-state transformer power unit switching modulation method according to claim 5, characterized in that, Based on the modulation state corresponding to each of the candidate handover times, the switching sequences corresponding to the target rotation unit pairs when maintaining the current modulation role and when exchanging modulation roles are determined, including: Based on the modulation reference quantity in the modulation state corresponding to each candidate handover time and the current modulation role of the target rotation unit pair, predict the target modulation state after each candidate handover time. Based on the switch state and target modulation state in the modulation state corresponding to each candidate handover time, determine the corresponding hold state switch sequence of the target rotation unit when maintaining the current modulation role; Based on the target modulation state after exchanging the modulation roles of the target rotation unit pair and the switching state in the modulation state corresponding to each candidate handover time, the corresponding rotation state switching sequence is determined.

7. The solid-state transformer power unit switching modulation method according to claim 5, characterized in that, Determining the target handover time based on the aforementioned rotation impact parameters includes: Candidate handover times where the rotation voltage increment is within a preset allowable voltage range are determined as candidate safe handover times; Select the candidate safe handover time that has the fewest number of additional switch rotations from the candidate safe handover times; The earliest candidate safe handover time among the selected candidate safe handover times is determined as the target handover time.

8. The solid-state transformer power unit switching modulation method according to claim 2, characterized in that, At the target handover time, the modulation roles of the target rotation unit pairs are exchanged, and the unit operation information of each power unit is updated, including: At the target handover time, the high-frequency modulation role of the power unit to be replaced is switched to that of the power unit to be replaced, and the modulation role of the power unit to be replaced is adjusted. Obtain the actual on-time, actual switching count, and device temperature of each power unit after the modulation role swap; The corresponding cumulative conduction time and cumulative switching count are updated based on the actual conduction time and actual switching count, and the unit operation information is updated based on the device temperature and the switched modulation role.

9. A solid-state transformer power unit switching modulation system, characterized in that, The system includes: The data acquisition unit is used to acquire the unit operation information of each power unit and determine the target rotation unit pair based on the unit operation information; An interval determination unit is used to determine a handover waiting interval based on the unit operation information of the target rotation unit pair; A time determination unit is used to determine the rotation influence parameters corresponding to each candidate handover time according to the modulation state of the target rotation unit pair within the handover waiting interval, and to determine the target handover time according to the rotation influence parameters. An execution unit is used to exchange the modulation roles of the target switching unit pairs at the target handover time and update the unit operation information of each power unit.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores instructions that, when executed on a computer, cause the computer to perform the solid-state transformer power unit switching modulation method according to any one of claims 1-8.

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