Power consumption suppression type switch aging self-maintenance modulation method for current source inverter

Abstract

The invention relates to the technical field of current source inverters, in particular to a current source inverter power consumption suppression type switch aging self-maintenance modulation method, which comprises the following steps: acquiring the junction temperature of each power switch of an H7 current source inverter, and determining the power switch which is aged too early according to the junction temperature of each power switch; and through a front-end power switch S7 of the H7 current source inverter, performing zero-current switching operation on the power switch which is aged too early, thereby realizing self-maintenance of the H7 current source inverter. Based on the H7-CSI topology circuit, the front-end power switch optimizes the circuit commutation process, and zero-current switching operation is performed on the aged power switch, so that the switching state is dynamically adjusted, the power consumption is remarkably reduced, the self-maintenance purpose is achieved, the service life of the current source inverter is effectively prolonged, and the working efficiency of the current source inverter is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of current source inverters, and particularly to a power consumption suppression type switch aging self-maintenance modulation method for a current source inverter. Background Art

[0002] As the core energy conversion device of renewable energy systems such as wind energy, photovoltaic energy, and ocean energy, the reliability of an inverter directly determines the operating efficiency and lifespan of a power generation system. In new energy power generation applications, an inverter operates in complex and variable environmental conditions for a long time. Research shows that the aging of power switch devices (such as IGBTs, MOSFETs, etc.) is mainly manifested as the accumulation of thermal stress caused by the fluctuation of the junction temperature, the damage of the gate oxide layer, and the fatigue of the packaging material, etc. Its failure process is closely coupled with the environment, electrical stress, and operating conditions. For example, in scenarios such as ocean energy power generation and offshore wind power, harsh conditions such as high humidity, salt spray corrosion, temperature fluctuations, and frequent load changes will significantly accelerate the aging process of the internal power switch devices of the inverter. The performance degradation of power switch devices will not only lead to a decrease in the electrical energy conversion efficiency, but may also cause system failures or even shutdowns, seriously affecting the economy and power supply stability of the new energy power generation system.

[0003] A current source inverter (CSI) is an inverter with boost capability and DC fault tolerance, and has been applied in the fields of new energy power generation, active power filtering, etc. The most widely used circuit topology at present is the traditional three-phase bridge circuit structure composed of 6 power switches, which is also called H6-CSI. The most commonly used seven-segment space vector modulation sequence model of H6-CSI is as Figure 3 shown, where A and B respectively represent two different non-zero vector states, N represents the zero vector state, and T s is the modulation period. During the modulation operation process, each power switch inside the H6-CSI has exactly the same modulation process, and there is no essential difference in the commutation operation, that is, the switching sequence of S1-S6 within one power frequency period is exactly the same. The H6-CSI lacks a differential commutation mechanism. Therefore, when facing a power switch that ages prematurely, it is difficult to design a dynamic regulation method.

[0004] Facing the device aging risk of the inverter, the traditional methods of inverter health management mostly rely on regular manual inspections or off-line tests. When it is found that a power switch device ages prematurely, there are usually only two options: Option 1, replace the module as a whole; Option 2, reduce the switching frequency to reduce the switching loss.

[0005] However, its limitations are also obvious: The maintenance cost of Solution 1 is relatively high, and it is difficult to respond in a timely manner in the harsh development environments of new energy sources such as the ocean or desert. Solution 2 will increase harmonics due to the overall reduction of the switching frequency, sacrificing the power quality, and it does not improve the unbalanced aging trend of each power switch device caused by long-term use. Therefore, it is difficult to achieve an ideal maintenance effect. Generally speaking, traditional technologies have not effectively addressed the aging problem of power switches caused by long-term use, thus limiting the service life and performance of current source inverters. Summarizing the technical solutions of H6-CSI, it is not difficult to find that this traditional topology restricts the improvement of the commutation mechanism. Especially for the premature aging phenomenon of power switches, there is a lack of feasibility in designing a mitigation power consumption modulation strategy.

[0006] In recent years, among the improvement and exploration works of many three-phase current source inverters, the H7 current source inverter (H7-CSI) is a meaningful attempt. What H7-CSI defines is a class of current source inverters that integrate 7 power semiconductor switches in the circuit, and its topology is as Figure 1 shown. Compared with H6-CSI, the most intuitive feature of H7-CSI is that on the basis of the original bridge circuit, an additional power switch S7 is added to obtain more flexible DC current control ability. This topology provides more commutation degrees of freedom for CSI, and there is great potential for improving the design of modulation strategies. However, there is still a lack of exploration on the aging maintenance of power switches for H7-CSI at present. Summary of the Invention

[0007] The purpose of the present invention is to provide a power consumption suppression type switch aging self-maintenance modulation method for a current source inverter, which can effectively extend the service life of the current source inverter and improve its working efficiency.

[0008] To achieve the above purpose, the present invention provides the following solution:

[0009] A power consumption suppression type switch aging self-maintenance modulation method for a current source inverter, including:

[0010] Obtain the junction temperature of each power switch of the H7 current source inverter, and determine the power switch with premature aging according to the junction temperature of each power switch;

[0011] Perform zero-current switching operation on the power switch with premature aging through the front-end power switch S7 of the H7 current source inverter to achieve self-maintenance of the H7 current source inverter.

[0012] Optionally, determining the power switch with premature aging according to the junction temperature of each power switch includes:

[0013] Collect the junction temperature of each of the power switches S1-S6 of the H7 current source inverter during normal operation, and obtain the average junction temperature;

[0014] Collect the junction temperature of each power switch of S1 - S6 when the current source inverter is working, compare the junction temperature of the power switch with a preset multiple of the average junction temperature, and determine the power switch with premature aging.

[0015] Optionally, performing zero - current - switching operation on the prematurely aged power switch through the front - end power switch S7 of the H7 current source inverter includes:

[0016] Obtain a zero vector by turning on the front - end power switch S7;

[0017] Obtain the number of times of performing the zero - current - switching operation according to the average junction temperature, the limit junction temperature of the power switch, and the junction temperature of the prematurely aged power switch;

[0018] Allocate the zero vector between two non - zero vectors, and according to the number of times of the zero - current - switching operation, make the front - and - rear adjacent two non - zero vector switches complete zero - current - switching within the zero - vector interval.

[0019] Optionally, obtaining the number of times of the zero - current - switching operation includes:

[0020] Calculate the limit aging coefficient according to the limit junction temperature of the power switch and the average junction temperature;

[0021] Calculate the premature aging coefficient according to the junction temperature of the prematurely aged power switch and the average junction temperature;

[0022] Calculate the number of times of the zero - current - switching operation according to the limit aging coefficient and the premature aging coefficient.

[0023] Optionally, calculating the number of times of the zero - current - switching operation includes:

[0024] ;

[0025] where N z is the number of times of the zero - current - switching operation, β i is the premature aging coefficient, α is the limit aging coefficient, M is the number of times of the turn - on - turn - off operation of the power switch in a single sector, and i is the number of the inverter power switch.

[0026] Optionally, calculating the limit aging coefficient includes:

[0027] α = T lim / T av ;

[0028] where T lim is the limit junction temperature of the power switch, and T av is the average junction temperature of the power switch of the inverter.

[0029] Optionally, calculating the premature aging coefficient includes:

[0030] β i = T i / T av ;

[0031] Wherein, T i is the junction temperature of the aging power switch.

[0032] Optionally, calculating the number of on-off operations performed by the power switch in the single sector includes:

[0033] ;

[0034] Wherein, T 工频 is the power frequency period, and T s is the modulation period.

[0035] The beneficial effects of the present invention are as follows: In the present invention, all the switching losses of the current source inverter are borne by S7. By configuring high-performance semiconductor devices (such as SiC power switches) for S7, the power consumption distribution reconstruction and optimization of the CSI can be realized. Therefore, the strong engineering practicability of the present invention is mainly manifested in two aspects: one is that the technical route of the present invention has low cost and high cost performance; the other is that on the basis of the existing traditional H6-CSI structure, it can be directly and quickly transformed. By adding S7 with high performance / reliability, the performance can be efficiently improved, so it is very conducive to practical application and expansion. At the same time, the present invention integrates three aspects: junction temperature measurement, aging determination, and power consumption suppression aging self-maintenance commutation strategy, which is conducive to realizing the intelligent management and control of the current source inverter and improving the operation and maintenance efficiency. This is of great significance for improving the guarantee ability of new energy power generation equipment in remote areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0037] Figure 1 It is a schematic diagram of the H7-CSI topology structure according to an embodiment of the present invention;

[0038] Figure 2 It is a schematic diagram of the H7-CSI space vector according to an embodiment of the present invention;

[0039] Figure 3 It is a schematic diagram of the single-cycle vector sequence model of the seven-segment space vector debugging strategy according to an embodiment of the present invention;

[0040] Figure 4 Schematic diagram of the monotonic modulation period vector state action model of the ZCS operation method according to an embodiment of the present invention;

[0041] Figure 5 Schematic diagram of the monotonic modulation period switch action sequence and its space vector state of the ZCS operation method according to an embodiment of the present invention;

[0042] Figure 6 Schematic diagram of the switch action process in the lower half modulation period of the ZCS mode according to an embodiment of the present invention;

[0043] Figure 7 Schematic diagram of the principle of a current source inverter power consumption suppression type switch aging self-maintenance modulation method according to an embodiment of the present invention. Detailed implementation manners

[0044] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0045] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0046] This embodiment provides a current source inverter power consumption suppression type switch aging self-maintenance modulation method, including:

[0047] Obtain the junction temperature of each power switch of the H7 current source inverter, and determine the power switches with premature aging according to the junction temperature of each power switch;

[0048] Perform zero-current switching operation on the power switches with premature aging through the front-end power switch S7 of the H7 current source inverter to achieve self-maintenance of the H7 current source inverter.

[0049] Specifically, this embodiment is based on the H7-CSI topology circuit, optimizes the commutation process of the circuit through the front-end power switch, performs zero-current switching operation on the aging power switches, dynamically adjusts the switch state, and significantly reduces power consumption, so as to achieve the purpose of self-maintenance, effectively extend the service life of the current source inverter, and improve its working efficiency.

[0050] Further, determining the power switches with premature aging according to the junction temperature of each power switch includes:

[0051] Collect the junction temperatures of each power switch S1-S6 when the H7 current source inverter is working normally, and obtain the average junction temperature;

[0052] Collect the junction temperatures of each power switch S1 - S6 during the operation of the current - source inverter, compare the junction temperature of the power switch with the average junction temperature multiplied by a preset multiple, and determine the power switches with premature aging.

[0053] Specifically, in this embodiment, the junction temperature of the power switch is measured by physical contact measurement method, optical non - contact measurement method, thermal impedance model prediction method, thermal - sensitive electrical parameter method, etc.

[0054] Furthermore, the zero - current - switching operation of the prematurely aged power switch through the front - end power switch S7 of the H7 current - source inverter includes:

[0055] Obtain a zero vector by turning on the front - end power switch S7;

[0056] Obtain the number of zero - current - switching operations according to the average junction temperature, the limit junction temperature of the power switch, and the junction temperature of the prematurely aged power switch;

[0057] Allocate the zero vector between two non - zero vectors, and according to the number of zero - current - switching operations, make the adjacent two non - zero - vector switches complete zero - current - switching within the zero - vector interval.

[0058] Specifically, under the zero - current - switching (ZCS) method, the switching losses of the rear - stage power switches S1 - S6 are approximately zero, and the switching losses generated by circuit modulation will be completely borne by the power switch S7, and the power switches S1 - S6 achieve zero - current - switching ability. Since its switching action times are relatively large, S7 should use wide - bandgap semiconductor devices with good performance, such as SiC - MOSFET, etc., to maintain its own low - power consumption level and reliability.

[0059] Even further, obtaining the number of zero - current - switching operations includes:

[0060] Calculate the limit aging coefficient according to the limit junction temperature and the average junction temperature of the power switch;

[0061] Calculate the premature aging coefficient according to the junction temperature of the prematurely aged power switch and the average junction temperature;

[0062] Calculate the number of zero - current - switching operations according to the limit aging coefficient and the premature aging coefficient.

[0063] Specifically, define the state where the power switch is about to completely fail due to aging as the limit aging condition. Under this limit condition, it should be ensured that all on - off operations of the power switch adopt the ZCS operation method. At this time, there is a limit aging coefficient , premature aging coefficient β i .

[0064] Further, calculating the number of zero-current switching operations includes:

[0065] ;

[0066] where N z is the number of zero-current switching operations, β i is the premature aging coefficient, is the limit aging coefficient, M is the number of on-off operations performed by the power switch in a single sector, and i is the number of the inverter power switch.

[0067] Further, calculating the limit aging coefficient includes:

[0068] α = T lim / T av ;

[0069] where T lim is the limit junction temperature of the power switch, and T av is the average junction temperature of the power switch of the inverter.

[0070] Further, calculating the premature aging coefficient includes:

[0071] β i = T i / T av ;

[0072] where T i is the junction temperature of the aging power switch.

[0073] Further, calculating the number of on-off operations performed by the power switch in a single sector includes:

[0074] ;

[0075] where T 工频 is the power frequency period, and T s is the modulation period.

[0076] The method of this embodiment will be further described below with reference to the accompanying drawings:

[0077] This embodiment proposes a self-maintenance modulation method for aging of the power switch of a current source inverter. As Figure 7 shown, the overall execution is divided into two steps:

[0078] Step 1: Junction temperature measurement and aging determination, that is, based on the H7-CSI circuit topology, obtain the junction temperature of each power switch, and evaluate the aging degree of the power switch according to the junction temperature information.

[0079] There is an extremely close and non - negligible relationship between the aging degree of a power switch device and its junction temperature. As the junction temperature continues to rise, significant changes will occur in the microstructure and material properties inside the device, thus accelerating its aging process. For example, due to the different thermal expansion coefficients of the materials in each layer inside the module, the increase in junction temperature will generate varying shear stresses, causing irreversible plastic deformation inside the power switch. With the accumulation of deformation, cracks and voids will appear at the root of the bonding wire and the solder layer. Moreover, the aging of the device will further lead to a decline in heat dissipation performance and an increase in power consumption, causing the junction temperature to rise further, forming a vicious cycle. Therefore, the aging degree of the power switch device and the junction temperature are interdependent and mutually causal. The closeness of their relationship is crucial for ensuring the long - term stable operation of the device. In the domestic and international academic fields, certain work has been done on the measurement of the power switch junction temperature. The common methods mainly include: physical contact measurement method, optical non - contact measurement method, thermal impedance model prediction method, thermal - sensitive electrical parameter method, etc.

[0080] When the H7 current - source inverter operates normally and stably, the above - mentioned methods can be selected to measure the junction temperature of each power switch one by one, and calculate the average value of these junction temperatures. If this average value approaches a certain constant value, then this value is recorded as the average junction temperature T av . Further, through continuous monitoring of the junction temperature of the power switch during the operation of the current - source inverter, once it is found that the junction temperature of a certain power switch ( , where i is the power - switch number) reaches or exceeds k times the average junction temperature T av , that is (k is the preset aging determination coefficient), it can be determined that the power switch is prematurely aged.

[0081] Step 2: Implement the power - consumption - suppression - type switch aging self - maintenance commutation strategy, that is: execute the power - consumption - suppression - type switch aging self - maintenance commutation strategy for the power switch that has been determined to be prematurely aged, reduce the power consumption of this power switch, so as to slow down its aging process and extend its service life, and achieve the self - maintenance of the current - source inverter.

[0082] The power - consumption - suppression - type switch aging self - maintenance modulation method proposed in this embodiment is based on the H7 - CSI topology circuit. By using the newly added front - end power switch S7 to optimize the circuit commutation process, perform zero - current - switching (ZCS) operation on the aging power switch to reduce its power consumption, thereby achieving the self - maintenance of the current - source inverter and extending its life.

[0083] The implementation conditions and specific principles of the power - consumption - suppression - type switch aging self - maintenance commutation strategy are as follows:

[0084] 1. Hardware configuration of H7 - CSI:

[0085] This embodiment is based on the H7-CSI topology, as shown in Figure 1 shown. In the circuit, six power switches S1-S6 use components with the same rated parameters and are responsible for performing commutation tasks; the power switch tube S7 is responsible for performing the "zero-current switching" task on aging components. Since its switching operation times are relatively large, S7 should use wide-bandgap semiconductor components with better performance, such as SiC-MOSFET, etc., to maintain its own low power consumption level and reliability.

[0086] 2. Basic commutation mode of H7-CSI (for normal working state):

[0087] ① Modulation method:

[0088] The space vector diagram of H7-CSI is as shown in Figure 2 shown. Its space vector states include six non-zero vector states (I1-I6) and four zero vector states (I0, I7, I8, I9).

[0089] In the normal working state, H7-CSI performs a seven-segment space vector modulation strategy, and its reference vector synthesis method is exactly the same as that of the traditional H6-CSI seven-segment space vector modulation strategy, and the zero vector is not realized through I0. The vector state action model within a standard modulation period is as shown in Figure 3 shown. Among them, T s is the modulation period; A and B respectively represent two different non-zero vector states, and N represents the zero vector state. In this state, the zero vector state does not need to be implemented by I0. As the reference vector rotates between sectors, the corresponding relationship of its composite vector is shown in Table 1.

[0090] Table 1: Method for selecting space vectors in the basic commutation mode

[0091]

[0092] ② Number of turn-on and turn-off operations:

[0093] Within a complete power frequency cycle, for a certain power switch, it will perform switching operations in three sectors (for example, the switching operation of S1 occurs in the II, IV, and VI sectors). Within a single modulation period, this power switch needs to perform a total of 2 turn-on and turn-off operations. Therefore, within a single sector, the number of turn-on and turn-off operations M of a certain power switch can be calculated by the following formula.

[0094] ;

[0095] Among them, T 工频 is the power frequency cycle, and multiplying it by one-sixth gives the time for the reference vector to rotate through one sector; Ts is the modulation period.

[0096] 3. Implementation of zero-current switching operation of H7-CSI:

[0097] In the space vector of H7-CSI, the zero vector can be realized by turning on S7, that is, executing I0. When the power factor angle on the AC side is less than ±30°, S7 can short-circuit the subsequent circuit. At this time, only current flows through S7 in H7-CSI, and the current flowing through the remaining power switches is zero.

[0098] The zero-current switching operation method is to allocate the zero vector (I0) between two non-zero vectors, so that the zero vector covers the switching edges of the two adjacent non-zero vectors before and after, enabling the switching combination of the two adjacent non-zero vectors before and after to complete zero-current switching within the zero vector interval. The vector state action model within a single modulation period is as Figure 4 shown. Among them, T s is the modulation period, A and B respectively represent two different non-zero vector states, and N represents the zero vector state. The corresponding relationship between the reference vector and its synthesized vector in different sectors during ZCS operation is shown in Table 2.

[0099] Table 2: Method for selecting space vectors for ZCS operation of H7-CSI

[0100]

[0101] Taking the case where S6 is determined to be prematurely aged as an example, focusing on its switching operation within sector I, the switching action sequence of the single modulation period of the ZCS operation method to be executed and the corresponding space vector states are as Figure 5 shown. When switch S7 is turned on, the subsequent circuit can be short-circuited, forcing H7-CSI to execute the zero vector I0 (corresponding to the zero vector N in Figure 4 ); when switch S7 is in the non-conducting state, the switch combinations {S1, S6} and {S1, S2} respectively execute the non-zero vectors I6 and I1 (corresponding to the non-zero vector A and non-zero vector B in Figure 4 respectively). I0 is between I6 and I1, and the switch combinations corresponding to I6 and I1 can complete zero-current switching within the I0 interval. Taking half of the modulation period as an example, Figure 6 shows the action process of the relevant switches. The conduction segment of S7 covers the front and back of when S6 needs to be turned on or off, enabling S6 to have the ability of zero-current switching. The switching situation in the remaining half cycle is symmetric and the same reason. The corresponding action time points t a 、t n1 and t n2 can be obtained by the following calculations.

[0102] ;

[0103] In the formula, T s is the modulation period, T0 is the action time of the zero vector within a single modulation period, and T1 and T2 are the action times of two different non-zero vectors respectively.

[0104] Therefore, under the ZCS operation method, the switching losses of the subsequent-stage power switches S1 - S6 are approximately zero. The switching losses generated by the circuit modulation will be entirely borne by the power switch S7, and the power switches S1 - S6 achieve zero-current switching capability. Since the high-performance SiC-MOSFET is selected for the power switch S7, its power consumption can be maintained at a relatively low level.

[0105] 4. Execution times of the aging switch ZCS operation within a single sector:

[0106] Define the state where the power switch is about to completely fail due to aging as the extreme aging condition. Under this extreme condition, it should be ensured that all turn-on and turn-off operations of this power switch adopt the ZCS operation method. At this time, there is an extreme aging coefficient , which can be expressed as: α = T lim / T av , where T lim is the extreme junction temperature of the power switch, and T av is the average junction temperature of the power switches of the inverter.

[0107] Define the premature aging coefficient β i , which can be expressed as: β i = T i / T av , where T i is the junction temperature of the aging power switch, i is the number of the power switch of the inverter (i = 1, 2, 3...6), and obviously β i ≥k.

[0108] For the power switches (S1~S6) that have been determined to be prematurely aging, the power consumption suppression aging self-maintenance commutation strategy can be adopted, that is, the switching modulation sequence is reallocated according to the degree of premature aging, so that the ZCS operation mode is executed in some modulation periods to extend the service life of this power switch. The number of ZCS operations of this aging power switch is determined according to the proportional relationship. Specifically, within one-sixth of the power frequency period (corresponding to one sector of the space vector diagram), the number of ZCS operations N z that this power switch needs to execute can be calculated and determined through the following formula.

[0109] ;

[0110] In the other two sectors where the power switch needs to act, the number of on-off operations for ZCS can be obtained in the same way. It should be noted that at this time, only this power switch determined to be prematurely aged is subjected to ZCS operation, and the other power switches still maintain their original modulation modes unchanged.

[0111] Taking the switch S6 as an example, it performs switch actions in three sectors I, III, and V. Among them, in sectors I and V, it acts as a non-zero vector, and in sector III, it acts as a zero vector. In sector I, the number M of ZCS operations performed on the power switch S6 can be obtained from If it has been determined that S6 is prematurely aged, its junction temperature and the average junction temperature The relationship between them can be expressed as: . Then, in sector I, the number N of ZCS operations that need to be performed on S6 z can be obtained from , and the number of ZCS operations performed in sectors III and V can be obtained in the same way.

[0112] Generally, the schematic diagram of the aging self-maintenance modulation method for the power switch of the current source inverter is as shown in Figure 7 . By performing two steps of junction temperature measurement and determination and power consumption suppression aging self-maintenance commutation strategy, the aging self-maintenance work of the power switch of the current source inverter can be completed.

[0113] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A self-maintenance modulation method for suppressing switch aging with power consumption of a current source inverter, characterized in that Including: Obtain the junction temperature of each power switch of the H7 current source inverter, and determine the prematurely aged power switch according to the junction temperature of each power switch; Perform zero-current switching operation on the prematurely aged power switch through the front-end power switch S7 of the H7 current source inverter to achieve self-maintenance of the H7 current source inverter.

2. The current source inverter power consumption suppression type switch aging self-maintenance modulation method according to claim 1, wherein Determining the prematurely aged power switch according to the junction temperature of each power switch includes: Collect the junction temperature of each power switch of S1 - S6 when the H7 current source inverter is working normally, and obtain the average junction temperature; Collect the junction temperature of each power switch of S1 - S6 when the current source inverter is working, compare the junction temperature of the power switch with a preset multiple of the average junction temperature, and determine the prematurely aged power switch.

3. The power consumption suppression type switching aging self-maintenance modulation method for a current source inverter according to claim 2, characterized in that, Performing zero-current switching operation on the prematurely aged power switch through the front-end power switch S7 of the H7 current source inverter includes: Obtain a zero vector by turning on the front-end power switch S7; Obtain the number of times of performing the zero-current switching operation according to the average junction temperature, the limit junction temperature of the power switch, and the junction temperature of the prematurely aged power switch; Allocate the zero vector between two non-zero vectors, and according to the number of times of the zero-current switching operation, enable the front and rear adjacent non-zero vector switches to complete zero-current switching within the zero vector interval.

4. The current source inverter power consumption suppression type switch aging self-maintenance modulation method according to claim 3, characterized in that, Obtaining the number of times of the zero-current switching operation includes: Calculate the limit aging coefficient according to the limit junction temperature and the average junction temperature of the power switch; Calculate the premature aging coefficient according to the junction temperature of the prematurely aged power switch and the average junction temperature; Calculate the number of times of the zero-current switching operation according to the limit aging coefficient and the premature aging coefficient.

5. The current source inverter power consumption suppression type switch aging self-maintenance modulation method according to claim 4, characterized in that Calculating the number of times of the zero-current switching operation includes: ； Among them, N z is the number of zero-current switching operations, β i is the premature aging coefficient, α is the ultimate aging coefficient, M is the number of on-off operations performed by the power switch in a single sector, and i is the number of the inverter power switch.

6. The current source inverter power consumption suppression type switch aging self-maintenance modulation method according to claim 5, characterized in that, Calculating the limit aging coefficient includes: α = T lim / T av ; Among them, T lim is the limit junction temperature of the power switch, and T av is the average junction temperature of the power switch of the inverter.

7. The current source inverter power consumption suppression type switch aging self-maintenance modulation method according to claim 6, characterized in that Calculating the premature aging coefficient includes: β i = T i / T av ; Among them, T i is the junction temperature of the aging power switch.

8. The method for self-maintenance modulation of switch aging by suppressing power consumption of a current source inverter according to claim 5, characterized in that Calculating the number of times of the turn-on - turn-off operation performed by the power switch in a single sector includes: ； Among them, T 工频 is the power frequency period, and T s is the modulation period.

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