Inverter modulation method and system based on parallel capacitance

Abstract

The application provides an inverter modulation method and system based on capacitor parallel connection, which comprises the following steps: connecting multiple capacitor-switch series branches in parallel to construct a capacitor parallel connection topology; taking the capacitor parallel connection topology as a sub-module of an inverter to construct an inverter three-phase circuit topology; determining the sine voltage required to be output by each phase circuit in the inverter three-phase circuit topology according to the voltage to be modulated, and sequentially charging the capacitors in the inverter three-phase circuit topology by alternating current until all the capacitors are fully charged; and switching the capacitor parallel connection topology of each phase according to the sine voltage required to be output by each phase circuit to generate the sine voltage required by each phase circuit, so as to obtain the voltage to be modulated and complete the modulation of the inverter. The method can avoid the internal circulating current that may be generated by the series topology structure, effectively improve the service life of the inverter while realizing the modulation of the inverter, and overcome the safety hazards existing in the prior art.

Description

Technical Field

[0001] This invention relates to the field of inverter modulation technology, and in particular to an inverter modulation method and system based on parallel capacitors. Background Technology

[0002] An inverter is a transformer that converts direct current (DC) power into alternating current (AC). In grid applications, it generates AC voltage to support the grid. Existing inverter topologies can convert DC signals to sinusoidal signals; their topologies are as follows: Figure 1 As shown.

[0003] This topology is based on multiple capacitors connected in series. Therefore, when two or more capacitors need to be connected, the switches must be opened simultaneously, which places high demands on synchronization. Furthermore, during normal operation, because there are multiple sub-modules with capacitors connected in parallel with switches on a certain bridge arm, circulating current will exist inside the circuit when the sub-module's switch is closed. The presence of circulating current can lead to inverter failure, and if the circulating current is too large, it may even burn out the inverter, reducing its lifespan, significantly increasing system costs, and also posing safety hazards. Summary of the Invention

[0004] This invention aims to provide an inverter modulation method and system based on parallel capacitors to solve the above-mentioned technical problems. By using a capacitor parallel topology formed by connecting multiple capacitor-switch series branches in parallel as a sub-module of the inverter, the problem of internal circulating current in the circuit when the switch is closed is effectively avoided, the service life of the inverter is improved, and the safety hazards existing in the prior art are overcome.

[0005] To address the aforementioned technical problems, this invention provides an inverter modulation method based on parallel capacitors, comprising the following steps:

[0006] Multiple capacitor-switch series branches are connected in parallel to construct a capacitor parallel topology;

[0007] The capacitor parallel topology is used as a sub-module of the inverter to construct the three-phase circuit topology of the inverter.

[0008] Determine the sinusoidal voltage that each phase circuit in the three-phase circuit topology of the inverter needs to output based on the voltage to be modulated.

[0009] Based on the sinusoidal voltage required to be output by each phase circuit, the capacitors in the three-phase circuit topology of the inverter are charged sequentially using AC power until all capacitors are fully charged.

[0010] The parallel capacitor topology of each phase is switched according to the sinusoidal voltage required by each phase circuit to generate the sinusoidal voltage required by each phase circuit, thereby obtaining the voltage to be modulated and completing the modulation of the inverter.

[0011] In the above scheme, the capacitor parallel topology formed by connecting multiple capacitor-switch series branches in parallel is used as a sub-module of the inverter. This can avoid the internal circulating current that may occur in the series topology, effectively improve the service life of the inverter while achieving modulation of the inverter, and overcome the safety hazards existing in the prior art.

[0012] Furthermore, the step of sequentially charging the capacitors in the three-phase circuit topology of the inverter with AC power according to the sinusoidal voltage required to be output by each phase circuit until all capacitors are fully charged is specifically as follows:

[0013] Divide one cycle of the sinusoidal voltage required to be output by each phase circuit into several time intervals, and calculate the DC voltage value required for each time interval.

[0014] Determine the capacitor charging value in each phase circuit based on the DC voltage value;

[0015] Based on the capacitor charging values, the capacitors in the three-phase circuit topology of the inverter are charged sequentially using AC power until all capacitors are fully charged.

[0016] The above scheme utilizes the AC / DC signal conversion process. A sinusoidal voltage can be decomposed into several DC voltage integrals, thereby determining several DC voltage values. Charging the capacitor with AC power only requires switching on a corresponding switch at specific time intervals to put a capacitor in a charging state; once the capacitor is fully charged, the switch connected in series with it is disconnected. The charging process is simple to operate and easy to implement.

[0017] Furthermore, in the process of sequentially charging the capacitors in the three-phase circuit topology of the inverter with AC power according to the capacitor charging value, after the charging operation of a certain capacitor is completed, a certain period of time must be waited before the charging operation of the next capacitor is carried out.

[0018] In the above scheme, the purpose of waiting for a certain period of time after the charging operation of a certain capacitor is completed is to ensure that the charging process of the next capacitor can be completely isolated from the influence of the first charging process, similar to a calibration process, which ensures the accuracy of charging, and ensures that the charging value of each capacitor is strictly equal to the calculated DC voltage value.

[0019] Furthermore, the switching operation of the parallel capacitor topology of each phase according to the sinusoidal voltage required by each phase circuit to generate a sinusoidal voltage that meets the needs of each phase circuit, thereby obtaining the voltage to be modulated and completing the modulation of the inverter, specifically involves:

[0020] The sinusoidal voltage that each phase circuit needs to output is sampled at certain time intervals to obtain the voltage value corresponding to each phase circuit in each time interval.

[0021] The capacitance required for each phase circuit in each time interval is determined based on the corresponding voltage value in each phase circuit in each time interval.

[0022] Based on the capacitors required to be connected in each circuit during each time interval, the parallel capacitor topology of each phase is switched to generate a sinusoidal voltage that meets the needs of each phase circuit, thereby obtaining the voltage to be modulated and completing the modulation of the inverter.

[0023] In the switching process described above, since each switching operation only requires determining the capacitor to be switched on, i.e., only one switch needs to be operated, eliminating the need to operate multiple switches simultaneously, the synchronous operation requirements of the circuit are reduced, ensuring more accurate modulation results. Furthermore, at any given moment during modulation, only one submodule needs to be operated on for a given phase, i.e., only the parallel topology of one capacitor needs to be operated, making the implementation process more convenient and effectively improving modulation efficiency.

[0024] Furthermore, the step of determining the capacitance to be applied in each phase circuit within each time interval based on the corresponding voltage value of each phase circuit within each time interval specifically involves:

[0025] Based on the voltage value of a certain phase circuit within a certain time interval, determine the capacitor in that phase circuit that has the closest DC voltage value to that voltage value, and use that capacitor as the capacitor that needs to be put into operation in that phase circuit within that time interval.

[0026] Repeat the above process until the capacitance required for each phase circuit in each time interval is determined.

[0027] In the above scheme, before the capacitor is switched on, the required voltage value is compared with the DC voltage value of the capacitor, and the capacitor with the closest DC voltage value is selected as the capacitor to be switched on in that phase circuit during that time interval. This ensures that the sinusoidal voltage obtained during the switching process is more in line with the modulation requirements and further improves the modulation accuracy.

[0028] This invention also proposes an inverter modulation system based on parallel capacitors, comprising a parallel topology module, an inverter three-phase circuit topology module, a processing module, a charging module, and a modulation module; wherein:

[0029] The parallel topology module is used to connect multiple capacitor-switch series branches in parallel to construct a capacitor parallel topology.

[0030] The inverter three-phase circuit topology module is used to construct the inverter three-phase circuit topology by using the parallel capacitor topology as a sub-module of the inverter.

[0031] The processing module is used to determine the sinusoidal voltage that each phase circuit in the three-phase circuit topology of the inverter needs to output based on the voltage to be modulated.

[0032] The charging module is used to charge the capacitors in the three-phase circuit topology of the inverter sequentially with AC power according to the sinusoidal voltage required by each phase circuit, until all capacitors are charged.

[0033] The modulation module is used to switch the parallel capacitor topology of each phase according to the sinusoidal voltage required by each phase circuit, so as to generate a sinusoidal voltage that meets the needs of each phase circuit, obtain the voltage to be modulated, and complete the modulation of the inverter.

[0034] The above system uses a capacitor parallel topology formed by connecting multiple capacitor-switch series branches in parallel as a sub-module of the inverter. This effectively avoids the internal circulating current that may occur in the series topology, and while achieving modulation of the inverter, it effectively improves the inverter's service life and overcomes the safety hazards existing in the prior art.

[0035] Furthermore, the charging module is used to sequentially charge the capacitors in the three-phase circuit topology of the inverter using AC power, according to the sinusoidal voltage required by each phase circuit, until all capacitors are fully charged. Specifically:

[0036] Divide one cycle of the sinusoidal voltage required to be output by each phase circuit into several time intervals, and calculate the DC voltage value required for each time interval.

[0037] Determine the capacitor charging value in each phase circuit based on the DC voltage value;

[0038] Based on the capacitor charging values, the capacitors in the three-phase circuit topology of the inverter are charged sequentially using AC power until all capacitors are fully charged.

[0039] Furthermore, in the charging module, during the process of sequentially charging the capacitors in the three-phase circuit topology of the inverter using AC power according to the capacitor charging value, after the charging operation of a certain capacitor is completed, a certain period of time must be waited before the charging operation of the next capacitor is performed.

[0040] Furthermore, the modulation module is used to switch the parallel capacitor topology of each phase according to the sinusoidal voltage required by each phase circuit, so as to generate a sinusoidal voltage that meets the needs of each phase circuit, obtain the voltage to be modulated, and complete the modulation of the inverter, specifically:

[0041] The sinusoidal voltage that each phase circuit needs to output is sampled at certain time intervals to obtain the voltage value corresponding to each phase circuit in each time interval.

[0042] The capacitance required for each phase circuit in each time interval is determined based on the corresponding voltage value in each phase circuit in each time interval.

[0043] Based on the capacitors required to be connected in each circuit during each time interval, the parallel capacitor topology of each phase is switched to generate a sinusoidal voltage that meets the needs of each phase circuit, thereby obtaining the voltage to be modulated and completing the modulation of the inverter.

[0044] Furthermore, in the modulation module, determining the capacitance to be applied to each phase circuit in each time interval based on the corresponding voltage value of each phase circuit in each time interval specifically involves:

[0045] Based on the voltage value of a certain phase circuit within a certain time interval, determine the capacitor in that phase circuit that has the closest DC voltage value to that voltage value, and use that capacitor as the capacitor that needs to be put into operation in that phase circuit within that time interval.

[0046] Repeat the above process until the capacitance required for each phase circuit in each time interval is determined. Attached Figure Description

[0047] Figure 1 A schematic diagram of an existing inverter topology is provided for the background art of this invention;

[0048] Figure 2 This is a schematic diagram of the inverter modulation method based on parallel capacitors proposed in an embodiment of the present invention.

[0049] Figure 3 This is a schematic diagram of the AC / DC signal conversion process according to an embodiment of the present invention;

[0050] Figure 4 This is a schematic diagram of a three-phase circuit topology of an inverter provided in an embodiment of the present invention;

[0051] Figure 5 A connection diagram of an inverter modulation system module based on parallel capacitors proposed in one embodiment of the present invention. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] Please see Figure 2 This embodiment provides an inverter modulation method based on parallel capacitors, including the following steps:

[0054] S1: Connect multiple capacitor-switch series branches in parallel to construct a capacitor parallel topology;

[0055] S2: Use the parallel capacitor topology as a sub-module of the inverter to construct the three-phase circuit topology of the inverter.

[0056] S3: Determine the sinusoidal voltage that each phase circuit in the three-phase circuit topology of the inverter needs to output based on the voltage to be modulated;

[0057] S4: Based on the sinusoidal voltage required to be output by each phase circuit, the capacitors in the three-phase circuit topology of the inverter are charged sequentially by AC power until all capacitors are fully charged.

[0058] S5: Based on the sinusoidal voltage required by each phase circuit, the parallel capacitor topology of each phase is switched to generate a sinusoidal voltage that meets the requirements of each phase circuit, thereby obtaining the voltage to be modulated and completing the modulation of the inverter.

[0059] In this embodiment, a capacitor parallel topology formed by connecting multiple capacitor-switch series branches in parallel is used as a sub-module of the inverter. This avoids the internal circulating current that may occur in the series topology, effectively improving the inverter's service life while achieving modulation of the inverter, and overcoming the safety hazards existing in the prior art.

[0060] Furthermore, the step of sequentially charging the capacitors in the three-phase circuit topology of the inverter with AC power according to the sinusoidal voltage required to be output by each phase circuit until all capacitors are fully charged is specifically as follows:

[0061] Divide one cycle of the sinusoidal voltage required to be output by each phase circuit into several time intervals, and calculate the DC voltage value required for each time interval.

[0062] Determine the capacitor charging value in each phase circuit based on the DC voltage value;

[0063] Based on the capacitor charging values, the capacitors in the three-phase circuit topology of the inverter are charged sequentially using AC power until all capacitors are fully charged.

[0064] This embodiment utilizes the AC / DC signal conversion process; please refer to [link / reference]. Figure 3 A sinusoidal voltage can be decomposed into several integrals of DC voltage, thus determining several DC voltage values. The process of charging a capacitor with alternating current simply requires switching on a corresponding switch at specific time intervals to put a capacitor in a charging state; once the capacitor is fully charged, the switch connected in series with it is disconnected. The charging process is simple to operate and easy to implement.

[0065] Furthermore, in the process of sequentially charging the capacitors in the three-phase circuit topology of the inverter with AC power according to the capacitor charging value, after the charging operation of a certain capacitor is completed, a certain period of time must be waited before the charging operation of the next capacitor is carried out.

[0066] In this embodiment, the purpose of waiting for a certain period of time after the charging operation of a certain capacitor is completed is to ensure that the charging process of the next capacitor can be completely isolated from the influence of the first charging process, similar to a calibration process, which ensures the accuracy of charging and ensures that the charging value of each capacitor is strictly equal to the calculated DC voltage value.

[0067] Furthermore, the switching operation of the parallel capacitor topology of each phase according to the sinusoidal voltage required by each phase circuit to generate a sinusoidal voltage that meets the needs of each phase circuit, thereby obtaining the voltage to be modulated and completing the modulation of the inverter, specifically involves:

[0068] The sinusoidal voltage that each phase circuit needs to output is sampled at certain time intervals to obtain the voltage value corresponding to each phase circuit in each time interval.

[0069] The capacitance required for each phase circuit in each time interval is determined based on the corresponding voltage value in each phase circuit in each time interval.

[0070] Based on the capacitors required to be connected in each circuit during each time interval, the parallel capacitor topology of each phase is switched to generate a sinusoidal voltage that meets the needs of each phase circuit, thereby obtaining the voltage to be modulated and completing the modulation of the inverter.

[0071] In this embodiment, during the switching process, only one capacitor needs to be selected for each switching operation, meaning only one switch needs to be operated, eliminating the need to operate multiple switches simultaneously. This reduces the synchronization requirements of the circuit and ensures more accurate modulation results. Furthermore, at any given moment during modulation, only one submodule needs to be operated on for a given phase; that is, only the parallel topology of one capacitor needs to be manipulated. This makes the implementation process more convenient and effectively improves modulation efficiency.

[0072] Furthermore, the step of determining the capacitance to be applied in each phase circuit within each time interval based on the corresponding voltage value of each phase circuit within each time interval specifically involves:

[0073] Based on the voltage value of a certain phase circuit within a certain time interval, determine the capacitor in that phase circuit that has the closest DC voltage value to that voltage value, and use that capacitor as the capacitor that needs to be put into operation in that phase circuit within that time interval.

[0074] Repeat the above process until the capacitance required for each phase circuit in each time interval is determined.

[0075] In this embodiment, before the capacitor is switched on, the required voltage value is compared with the DC voltage value of the capacitor, and the capacitor with the closest DC voltage value is selected as the capacitor to be switched on in this phase circuit during this time interval. This ensures that the sinusoidal voltage obtained during the switching process is more in line with the modulation requirements and further improves the modulation accuracy.

[0076] To further illustrate the implementation process of this invention, this embodiment provides a specific circuit topology diagram. The connections and parameters in this diagram are merely one practical application of this invention and should not be construed as limiting the scope of protection of this invention. Please refer to [link / reference] for details. Figure 4 The diagram shows a three-phase inverter circuit topology. This circuit topology is connected to another modular multilevel inverter to form a DC power transmission circuit, which can convert DC power into three-phase AC power through the switching process of capacitors.

[0077] The charging process for this topology is as follows:

[0078] For phase A, alternating current is used to charge the capacitors in the parallel capacitor topology of phase A, at time s. a1 The capacitor a1 is charged until the value u is reached. dca1 Disconnect switch k after capacitor a1 has finished charging. a1 Waiting for a period of time at time s a2 The capacitor a2 is charged until the value u is reached. dca2 Disconnect switch k after capacitor a2 has finished charging. a2 Capacitor a (n-1) Disconnect switch k after charging is complete a(n-1) After waiting for a period of time, at time s an For capacitor a n Charge and reach the value u dcan .

[0079] For phase B, at time s b1 The capacitor b1 is charged until the value u is reached. dcb1 Wait until capacitor b1 is fully charged, then disconnect switch k. b1 After waiting for a period of time, at time s b2 The capacitor b2 is charged until the value u is reached. dcb2 Wait until capacitor b2 is fully charged, then disconnect switch k. b2 Capacitor b (n-1) Disconnect switch k after charging is complete (n-1) After waiting for a period of time, at time s bn For capacitor b n Charge and reach the value u dcbn .

[0080] For phase C, at time s c1The capacitor C1 is charged until the value u is reached. dcc1 Disconnect switch K after capacitor C1 has finished charging. c1 At time s c2 The capacitor C2 is charged until the value u is reached. dcc2 Disconnect switch K after capacitor C2 has finished charging. c2 Capacitor c (n-1) Disconnect switch k after charging is complete (n-1) After waiting for a period of time, at time s cn For capacitor c n Charge and reach the value u dccn .

[0081] Taking phase A as an example, this embodiment illustrates the numerical value u. dcan The modulation is determined based on actual needs during operation. Phase A requires an adjustable sinusoidal signal. Dividing one period (T) of an adjustable sinusoidal signal into N equal time intervals, then NΔt = T. The DC voltage of phase A capacitor is then:

[0082]

[0083] In the formula, Δt represents the time interval.

[0084] The specific switching process for this topology is as follows:

[0085] For phase A, at time s ta1 At time s ta2 Between these points, capacitor a1 is connected; at time s ta2 At time s ta3 Between these points, capacitor a2 is connected; at time s tan At time s ta(n+1) Between, capacitor a is inserted n Then repeat the process.

[0086] For phase B, at time s ta1 +Δt b1 to s ta1 +Δt b2 Capacitor b1 is connected; at time s ta1 +Δt b2 to s ta1 +Δt b3 Capacitor b2 is connected; at time s tan +Δt bn to s ta(n+1) +Δt b(n+1) Then, capacitor bn is added, and the process is repeated.

[0087] For phase C, at time s ta1 +Δtc1 to s ta2 +Δt c2 Connect capacitor C1; at time s ta2 +Δt c2 to s ta3 +Δt c3 Connect capacitor C2; at time s tan +Δt cn to s ta(n+1) +Δt c(n+1) , input capacitor c n Then repeat the process.

[0088] It should be noted that, to further improve the modulation accuracy, this embodiment can also perform the switching operation using intelligent devices such as relays. The switching is performed by identifying and finding the capacitor with the closest DC voltage value to the desired voltage value. Specifically:

[0089] Taking phase A as an example, the sinusoidal voltage that phase A needs to output is The sampling time is Δt s The first sampled value of the A-phase sinusoidal voltage is The sampled value is compared with the DC voltage values ​​of all capacitor banks, and the capacitor corresponding to the DC voltage with the closest value is connected. This process is repeated to compare subsequent sampled values ​​of the A-phase sinusoidal voltage with the DC voltage values ​​of the capacitor banks to determine which capacitors need to be connected.

[0090] Please see Figure 5 This embodiment proposes an inverter modulation system based on parallel capacitors to implement an inverter modulation method based on parallel capacitors. The system includes a parallel topology module, an inverter three-phase circuit topology module, a processing module, a charging module, and a modulation module; wherein:

[0091] The parallel topology module is used to connect multiple capacitor-switch series branches in parallel to construct a capacitor parallel topology.

[0092] The inverter three-phase circuit topology module is used to construct the inverter three-phase circuit topology by using the parallel capacitor topology as a sub-module of the inverter.

[0093] The processing module is used to determine the sinusoidal voltage that each phase circuit in the three-phase circuit topology of the inverter needs to output based on the voltage to be modulated.

[0094] The charging module is used to charge the capacitors in the three-phase circuit topology of the inverter sequentially with AC power according to the sinusoidal voltage required by each phase circuit, until all capacitors are charged.

[0095] The modulation module is used to switch the parallel capacitor topology of each phase according to the sinusoidal voltage required by each phase circuit, so as to generate a sinusoidal voltage that meets the needs of each phase circuit, obtain the voltage to be modulated, and complete the modulation of the inverter.

[0096] The system provided in this embodiment uses a capacitor parallel topology formed by connecting multiple capacitor-switch series branches in parallel as a sub-module of the inverter. This effectively avoids the internal circulating current that may occur in the series topology, and while achieving modulation of the inverter, it effectively improves the service life of the inverter and overcomes the safety hazards existing in the prior art.

[0097] Furthermore, the charging module is used to sequentially charge the capacitors in the three-phase circuit topology of the inverter using AC power, according to the sinusoidal voltage required by each phase circuit, until all capacitors are fully charged. Specifically:

[0098] Divide one cycle of the sinusoidal voltage required to be output by each phase circuit into several time intervals, and calculate the DC voltage value required for each time interval.

[0099] Determine the capacitor charging value in each phase circuit based on the DC voltage value;

[0100] Based on the capacitor charging values, the capacitors in the three-phase circuit topology of the inverter are charged sequentially using AC power until all capacitors are fully charged.

[0101] Furthermore, in the charging module, during the process of sequentially charging the capacitors in the three-phase circuit topology of the inverter using AC power according to the capacitor charging value, after the charging operation of a certain capacitor is completed, a certain period of time must be waited before the charging operation of the next capacitor is performed.

[0102] Furthermore, the modulation module is used to switch the parallel capacitor topology of each phase according to the sinusoidal voltage required by each phase circuit, so as to generate a sinusoidal voltage that meets the needs of each phase circuit, obtain the voltage to be modulated, and complete the modulation of the inverter, specifically:

[0103] The sinusoidal voltage that each phase circuit needs to output is sampled at certain time intervals to obtain the voltage value corresponding to each phase circuit in each time interval.

[0104] The capacitance required for each phase circuit in each time interval is determined based on the corresponding voltage value in each phase circuit in each time interval.

[0105] Based on the capacitors required to be connected in each circuit during each time interval, the parallel capacitor topology of each phase is switched to generate a sinusoidal voltage that meets the needs of each phase circuit, thereby obtaining the voltage to be modulated and completing the modulation of the inverter.

[0106] Furthermore, in the modulation module, determining the capacitance to be applied to each phase circuit in each time interval based on the corresponding voltage value of each phase circuit in each time interval specifically involves:

[0107] Based on the voltage value of a certain phase circuit within a certain time interval, determine the capacitor in that phase circuit that has the closest DC voltage value to that voltage value, and use that capacitor as the capacitor that needs to be put into operation in that phase circuit within that time interval.

[0108] Repeat the above process until the capacitance required for each phase circuit in each time interval is determined.

[0109] In this embodiment, the charging and switching of the capacitor can be intelligently achieved through a controller and relays. The most suitable capacitor is intelligently found by calculating the values ​​of the processing module, charging module and modulation module, and the intelligent switching of the capacitor is achieved by controlling the on and off of the relay, thereby improving the operability of the modulation process.

[0110] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. An inverter modulation method based on parallel capacitors, characterized in that, Includes the following steps: Multiple capacitor-switch series branches are connected in parallel to construct a capacitor parallel topology; The capacitor parallel topology is used as a sub-module of the inverter to construct the three-phase circuit topology of the inverter. Determine the sinusoidal voltage that each phase circuit in the three-phase circuit topology of the inverter needs to output based on the voltage to be modulated. Based on the sinusoidal voltage required to be output by each phase circuit, the capacitors in the three-phase circuit topology of the inverter are charged sequentially using AC power until all capacitors are fully charged. The parallel capacitor topology of each phase is switched according to the sinusoidal voltage required by each phase circuit to generate the sinusoidal voltage required by each phase circuit, thereby obtaining the voltage to be modulated and completing the modulation of the inverter.

2. The inverter modulation method based on parallel capacitors according to claim 1, characterized in that, The process involves sequentially charging the capacitors in the three-phase circuit topology of the inverter using alternating current, based on the sinusoidal voltage required by each phase circuit, until all capacitors are fully charged. Specifically: Divide one cycle of the sinusoidal voltage required to be output by each phase circuit into several time intervals, and calculate the DC voltage value required for each time interval. Determine the capacitor charging value in each phase circuit based on the DC voltage value; Based on the capacitor charging values, the capacitors in the three-phase circuit topology of the inverter are charged sequentially using AC power until all capacitors are fully charged.

3. The inverter modulation method based on parallel capacitors according to claim 2, characterized in that, In the process of sequentially charging the capacitors in the three-phase circuit topology of the inverter with AC power according to the capacitor charging value, after the charging operation of a certain capacitor is completed, a certain period of time must be waited before the charging operation of the next capacitor is carried out.

4. The inverter modulation method based on parallel capacitors according to claim 1, characterized in that, The process involves switching the parallel capacitor topology of each phase according to the sinusoidal voltage required by each phase circuit to generate a sinusoidal voltage that meets the needs of each phase circuit, thus obtaining the voltage to be modulated and completing the modulation of the inverter. Specifically: The sinusoidal voltage that each phase circuit needs to output is sampled at certain time intervals to obtain the voltage value corresponding to each phase circuit in each time interval. The capacitance required for each phase circuit in each time interval is determined based on the corresponding voltage value in each phase circuit in each time interval. Based on the capacitors required to be connected in each circuit during each time interval, the parallel capacitor topology of each phase is switched to generate a sinusoidal voltage that meets the needs of each phase circuit, thereby obtaining the voltage to be modulated and completing the modulation of the inverter.

5. The inverter modulation method based on parallel capacitors according to claim 4, characterized in that, The determination of the capacitor to be applied in each phase circuit during each time interval based on the corresponding voltage value of each phase circuit during each time interval is specifically as follows: Based on the voltage value of a certain phase circuit within a certain time interval, determine the capacitor in that phase circuit that has the closest DC voltage value to that voltage value, and use that capacitor as the capacitor that needs to be put into operation in that phase circuit within that time interval. Repeat the above process until the capacitance required for each phase circuit in each time interval is determined.

6. An inverter modulation system based on parallel capacitors, characterized in that, It includes a parallel topology module, an inverter three-phase circuit topology module, a processing module, a charging module, and a modulation module; among which: The parallel topology module is used to connect multiple capacitor-switch series branches in parallel to construct a capacitor parallel topology. The inverter three-phase circuit topology module is used to construct the inverter three-phase circuit topology by using the parallel capacitor topology as a sub-module of the inverter. The processing module is used to determine the sinusoidal voltage that each phase circuit in the three-phase circuit topology of the inverter needs to output based on the voltage to be modulated. The charging module is used to charge the capacitors in the three-phase circuit topology of the inverter sequentially with AC power according to the sinusoidal voltage required by each phase circuit, until all capacitors are charged. The modulation module is used to switch the parallel capacitor topology of each phase according to the sinusoidal voltage required by each phase circuit, so as to generate a sinusoidal voltage that meets the needs of each phase circuit, obtain the voltage to be modulated, and complete the modulation of the inverter.

7. The inverter modulation system based on parallel capacitors according to claim 6, characterized in that, The charging module is used to charge the capacitors in the three-phase circuit topology of the inverter sequentially using AC power, according to the sinusoidal voltage required by each phase circuit, until all capacitors are fully charged. Specifically: Divide one cycle of the sinusoidal voltage required to be output by each phase circuit into several time intervals, and calculate the DC voltage value required for each time interval. Determine the capacitor charging value in each phase circuit based on the DC voltage value; Based on the capacitor charging values, the capacitors in the three-phase circuit topology of the inverter are charged sequentially using AC power until all capacitors are fully charged.

8. The inverter modulation system based on parallel capacitors according to claim 7, characterized in that, In the charging module, during the process of sequentially charging the capacitors in the three-phase circuit topology of the inverter using AC power according to the capacitor charging value, after the charging operation of a certain capacitor is completed, a certain amount of time must be waited before the charging operation of the next capacitor is performed.

9. The inverter modulation system based on parallel capacitors according to claim 6, characterized in that, The modulation module is used to switch the parallel capacitor topology of each phase according to the sinusoidal voltage required by each phase circuit, so as to generate a sinusoidal voltage that meets the needs of each phase circuit, obtain the voltage to be modulated, and complete the modulation of the inverter, specifically: The sinusoidal voltage that each phase circuit needs to output is sampled at certain time intervals to obtain the voltage value corresponding to each phase circuit in each time interval. The capacitance required for each phase circuit in each time interval is determined based on the corresponding voltage value in each phase circuit in each time interval. Based on the capacitors required to be connected in each circuit during each time interval, the parallel capacitor topology of each phase is switched to generate a sinusoidal voltage that meets the needs of each phase circuit, thereby obtaining the voltage to be modulated and completing the modulation of the inverter.

10. The inverter modulation system based on parallel capacitors according to claim 9, characterized in that, In the modulation module, determining the capacitance to be applied to each phase circuit in each time interval based on the corresponding voltage value of each phase circuit in each time interval specifically involves: Based on the voltage value of a certain phase circuit within a certain time interval, determine the capacitor in that phase circuit that has the closest DC voltage value to that voltage value, and use that capacitor as the capacitor that needs to be put into operation in that phase circuit within that time interval. Repeat the above process until the capacitance required for each phase circuit in each time interval is determined.

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