Multi-mode modulation method and controller for soft-switching three-level inverter

Abstract

The application discloses a kind of soft-switching three-level inverter multi-mode modulation method and controller, belong to power electronic conversion and control technical field, by providing the multi-mode modulation method of above-mentioned soft-switching three-level inverter, can utilize the index table including the modulation mode index of minimum loss under each working condition, can select the modulation mode of minimum loss for each phase three-level bridge arm at each time, make the whole system improve efficiency in full working condition range.In addition, the multi-mode modulation method has universality, the three-level structure used can be T type, ANPC type or flying capacitor type topology structure, the switch device used can be IGBT or MOSFET, the modulation method provided can be used in three-phase, single-phase system, therefore not be restricted by topology structure, device type and inverter type, and universality is stronger.

Description

Technical Field

[0001] This invention belongs to the field of power electronic conversion and control technology, and more specifically, relates to a multi-mode modulation method and controller for a soft-switching three-level inverter. Background Technology

[0002] Three-level inverters, as power conversion devices, are widely used to connect DC units such as photovoltaics and energy storage to AC loads or the power grid. With the increasing penetration rate of new energy sources in the power grid, the complexity of AC loads is increasing, requiring inverters to have higher control bandwidth. From the perspective of inverter components, this means a higher switching frequency is needed.

[0003] However, higher switching frequencies lead to greater switching losses, resulting in decreased reliability and cost-effectiveness. Soft-switching technology can significantly reduce these losses. In particular, the turn-on losses of SiC MOSFETs (Silicon Carbide Metal-Oxide-Semiconductor Field-Effect Transistors) are much higher than their turn-off losses. If these turn-on losses could be eliminated through Zero Voltage Switching (ZVS) technology, there is enormous potential for frequency increases. However, for three-level inverters, which have more series-connected devices and greater conduction losses, ZVS introduces even greater current stress, leading to more significant conduction losses. Therefore, the eliminated turn-on losses may not be enough to cover the increased conduction losses, leaving three-level inverters still facing substantial losses.

[0004] Therefore, optimizing the ZVS soft-switching modulation method for three-level inverters can potentially improve their switching frequency. ZVS soft-switching modulation focuses on lower switching losses, while traditional hard-switching modulation focuses on lower conduction losses. Under different load intensities and even at different times within a cycle, the instantaneous current stress varies, and different modulation methods will lead to differences in system losses. Therefore, for three-level inverters, researching the switching operation of multiple modulation modes, including soft-switching modulation, is of great significance for improving the system's conversion efficiency, power density, and controllability. Summary of the Invention

[0005] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a multi-mode modulation method and controller for a soft-switching three-level inverter, so as to reduce system losses, improve system efficiency under all operating conditions, and further improve the power density of the entire system in high-power and high-frequency applications.

[0006] To achieve the above objectives, according to a first aspect of the present invention, a multi-mode modulation method for a soft-switching three-level inverter is provided, comprising: For any three-level bridge arm in a soft-switching three-level inverter, during actual operation of the soft-switching three-level inverter, the real-time operating power and real-time phase information of the sinusoidal modulation wave signal of the any three-level bridge arm are obtained; the sinusoidal modulation wave signal is generated based on the current of the AC filter inductor connected to the output terminal of the any three-level bridge arm. Based on the real-time operating power and the real-time phase information, a preset index table is retrieved, and the modulation mode with the minimum inverter loss at that moment is selected for operation. The index table is obtained by performing loss analysis after modulating any phase three-level bridge arm according to multiple preset modulation modes under different operating conditions, and establishing an index of the modulation mode with the minimum loss for each operating condition. Any operating condition is represented by the real-time operating power and the real-time phase information. The soft-switching three-level inverter includes three-phase parallel three-level bridge arms and three AC output filter inductors, and the three-phase three-level bridge arms are independently modulated; the three-phase parallel three-level bridge arms include three pairs of three-level bridge arms and three pairs of differential-mode inductors, and one pair of three-level bridge arms and one pair of differential-mode inductors form one phase three-level bridge arm; in one phase three-level bridge arm, the output terminal of each three-level bridge arm is connected to the first terminal of a differential-mode inductor, the second terminals of two differential-mode inductors are connected, and the connection terminal between the two differential-mode inductors serves as the output terminal of one phase three-level bridge arm, and the output terminal of one phase three-level bridge arm is connected to an AC output filter inductor.

[0007] According to the above multi-mode modulation method, the first mode among the multiple preset modulation modes modulates any three-level bridge arm based on the following method: Generate driving signals corresponding to the first three-level bridge arm and the second three-level bridge arm in any phase three-level bridge arm, so as to drive the first three-level bridge arm and the second three-level bridge arm to operate based on the driving signals corresponding to the first three-level bridge arm and the second three-level bridge arm respectively, so as to achieve the zero-voltage turn-on soft-switching condition of the soft-switching three-level inverter. The driving signals corresponding to the first and second three-level bridge arms respectively enable the operation of the second three-level bridge arm to always be delayed compared to the first three-level bridge arm, resulting in the current direction of the two differential mode inductors connected to the first and second three-level bridge arms changing alternately; the driving signal levels corresponding to the first and second three-level bridge arms respectively include +1, 0 and -1.

[0008] According to the above multi-mode modulation method, generating driving signals corresponding to the first and second three-level bridge arms in any phase three-level bridge arm, and driving the first and second three-level bridge arms to operate based on the driving signals corresponding to the first and second three-level bridge arms respectively, specifically includes: Obtain the current of the differential mode inductor connected to the first three-level bridge arm and the second three-level bridge arm in any of the three-phase bridge arms, and the current of the AC output filter inductor connected to the output terminal of any of the three-phase bridge arms. A sinusoidal modulation wave is generated based on the current of the AC output filter inductor connected to the output terminal of any of the three-level bridge arms, and a driving signal corresponding to the first three-level bridge arm is generated using a three-level carrier modulation method for the sinusoidal modulation wave. Within one switching cycle corresponding to the sinusoidal modulation wave, the first three-level bridge arm is driven to operate first based on the drive signal corresponding to the first three-level bridge arm, so that there is a level difference between the first three-level bridge arm and the second three-level bridge arm. Under the influence of the level difference, the current of the differential mode inductor connected to the two three-level bridge arms drops from the peak value to zero and rises from zero to the peak value, respectively. After the current exchange of the differential mode inductor connected to the two three-level bridge arms is completed, the level of the drive signal corresponding to the second three-level bridge arm is switched, and the level of the drive signal corresponding to the second three-level bridge arm switches between +1 and 0 and between -1 and 0.

[0009] According to the above multi-mode modulation method, after the current exchange of the differential mode inductors connected to the two three-level bridge arms is completed, switching the level of the drive signal corresponding to the second three-level bridge arm specifically includes: Within one switching cycle corresponding to the sinusoidal modulation wave, when the sinusoidal modulation wave is in the positive half-cycle, if the trigger condition i is satisfied... Lx1 >i Lx2 And i Lx2 <-I ZVS Then, the level of the drive signal corresponding to the second three-level bridge arm is set to +1. If the trigger condition i is met... Lx1 Lx2 And i Lx1 <-I ZVS Then, the level of the driving signal corresponding to the second three-level bridge arm is set to 0; when the sinusoidal modulation wave is in the negative half-cycle, if the trigger condition i is met... Lx1 Lx2 And i Lx2 >I ZVS Then, the level of the drive signal corresponding to the second three-level bridge arm is set to -1. If the trigger condition i is met... Lx1 >i Lx2 And i​​Lx1 >I ZVS Then the level of the drive signal corresponding to the second three-level bridge arm is set to 0; Among them, i Lx1 i is the current of the differential mode inductor connected to the first three-level bridge arm. Lx2 For the current of the differential mode inductor connected to the second three-level bridge arm, I ZVS To meet the minimum reverse current required for the complete charging and discharging of the output capacitor of the switching transistor.

[0010] According to the above multi-mode modulation method, in the second mode among the multiple preset modulation modes, the driving signals corresponding to the first three-level bridge arm and the second three-level bridge arm in any phase three-level bridge arm are generated in accordance with the driving signal generation method corresponding to the first three-level bridge arm in the first mode.

[0011] According to the above multi-mode modulation method, the third mode among the multiple preset modulation modes modulates any three-level bridge arm based on the following method: Generate driving signals corresponding to the first three-level bridge arm and the second three-level bridge arm in any phase three-level bridge arm, so as to drive the first three-level bridge arm and the second three-level bridge arm to operate based on the driving signals corresponding to the first three-level bridge arm and the second three-level bridge arm respectively, so as to achieve the zero-voltage turn-on soft-switching condition of the soft-switching three-level inverter. The driving signals corresponding to the first and second three-level bridge arms respectively enable the operation of the second three-level bridge arm to always be delayed compared to the first three-level bridge arm, resulting in the current direction of the two differential mode inductors connected to the first and second three-level bridge arms changing alternately; the driving signal levels corresponding to the first and second three-level bridge arms respectively include +1 and -1.

[0012] According to the above multi-mode modulation method, generating driving signals corresponding to the first and second three-level bridge arms in any phase three-level bridge arm, and driving the first and second three-level bridge arms to operate based on the driving signals corresponding to the first and second three-level bridge arms respectively, specifically includes: Obtain the current of the differential mode inductor connected to the first three-level bridge arm and the second three-level bridge arm in any of the three-phase bridge arms, and the current of the AC output filter inductor connected to the output terminal of any of the three-phase bridge arms. A sinusoidal modulation wave is generated based on the current of the AC output filter inductor connected to the output terminal of any of the three-level bridge arms, and a driving signal corresponding to the first three-level bridge arm is generated based on the two-level carrier modulation method for the sinusoidal modulation wave. Within one switching cycle corresponding to the sinusoidal modulation wave, the first three-level bridge arm is driven to operate first based on the drive signal corresponding to the first three-level bridge arm, so that there is a level difference between the first three-level bridge arm and the second three-level bridge arm. Under the influence of the level difference, the current of the differential mode inductor connected to the two three-level bridge arms drops from the peak value to zero and rises from zero to the peak value, respectively. After the current exchange of the differential mode inductor connected to the two three-level bridge arms is completed, the level of the drive signal corresponding to the second three-level bridge arm is switched. The level of the drive signal corresponding to the second three-level bridge arm switches between +1 and -1.

[0013] According to the above multi-mode modulation method, after the current exchange of the differential mode inductors connected to the two three-level bridge arms is completed, switching the level of the drive signal corresponding to the second three-level bridge arm specifically includes: Within one switching cycle corresponding to the sinusoidal modulation wave, when the sinusoidal modulation wave is in the positive half-cycle, if the trigger condition i is satisfied... Lx1 >i Lx2 And i Lx2 <-I ZVS Then, the level of the drive signal corresponding to the second three-level bridge arm is set to +1. If the trigger condition i is met... Lx1 Lx2 And i Lx1 <-I ZVS Then, the level of the driving signal corresponding to the second three-level bridge arm is set to -1; when the sinusoidal modulation wave is in the negative half-cycle, if the trigger condition i is met... Lx1 Lx2 And i Lx2 >I ZVS Then, the level of the drive signal corresponding to the second three-level bridge arm is set to -1. If the trigger condition i is met... Lx1 >i Lx2 And i Lx1 >I ZVS Then the level of the drive signal corresponding to the second three-level bridge arm is set to +1; Among them, i Lx1 i is the current of the differential mode inductor connected to the first three-level bridge arm. Lx2 For the current of the differential mode inductor connected to the second three-level bridge arm, I ZVS To meet the minimum reverse current required for the complete charging and discharging of the output capacitor of the switching transistor.

[0014] According to the above multi-mode modulation method, in the fourth mode among the multiple preset modulation modes, the driving signals corresponding to the first three-level bridge arm and the second three-level bridge arm in any phase three-level bridge arm are generated in accordance with the driving signal generation method corresponding to the first three-level bridge arm in the third mode. ​​

[0015] According to a second aspect of the invention, a controller is provided for performing the method as described in the first aspect.

[0016] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: By providing the aforementioned multi-mode modulation method for soft-switching three-level inverters, an index table containing the modulation mode index with the minimum loss under each operating condition can be used to select the modulation mode with the minimum loss for each phase three-level bridge arm at any given time, thereby improving the efficiency of the entire system across the entire operating range. Furthermore, this multi-mode modulation method is versatile; the three-level structure used can be T-type, ANPC-type, or flying capacitor-type topology, and the switching devices can be IGBTs or MOSFETs. The provided modulation method can be applied to three-phase and single-phase systems, thus it is not constrained by topology, device type, or inverter type, exhibiting strong versatility. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the inverter's operating principle during operation of the multi-mode modulation method provided in this embodiment of the invention. Figure 2 This is a schematic diagram of the structure of a soft-switching three-level inverter provided in an embodiment of the present invention; Figure 3 A schematic diagram of an index table provided in an embodiment of the present invention; Figure 4 The waveforms of the differential mode inductor current and the AC filter inductor current of phase a when operating alone in the first mode, as provided in the embodiments of the present invention; Figure 5 The waveforms of the differential mode inductor current and AC filter inductor current of phase a when operating alone in the second mode provided in this embodiment of the invention; Figure 6 The waveforms of the differential mode inductor current and AC filter inductor current of phase a when the third mode is operated alone, as provided in the embodiments of the present invention; Figure 7 The waveforms of the differential mode inductor current and AC filter inductor current of phase a when operating alone in the fourth mode provided in this embodiment of the invention; Figure 8 The waveforms of the phase differential mode inductor current and the AC filter inductor current when the multi-mode modulation method provided in this embodiment of the invention is working; Figure 9 The power loss histograms generated during the operation of the four working modes and the multi-mode modulation method provided in the embodiments of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0019] This invention provides a multi-mode modulation method for a soft-switching three-level inverter, such as... Figure 1 As shown, it includes: For any three-level bridge arm in a soft-switching three-level inverter, during actual operation of the soft-switching three-level inverter, the real-time operating power and real-time phase information of the sinusoidal modulation wave signal of the soft-switching three-level inverter are obtained; the sinusoidal modulation wave signal is generated based on the current of the AC filter inductor connected to the output terminal of any three-level bridge arm. Based on the real-time operating power and the real-time phase information, a preset index table is retrieved, and the modulation mode with the minimum inverter loss at that moment is selected for operation. The index table is obtained by performing loss analysis after modulating any phase three-level bridge arm according to multiple preset modulation modes under different operating conditions, and establishing an index of the modulation mode with the minimum loss for each operating condition. Any operating condition is represented by the real-time operating power and the real-time phase information. Here, as Figure 2 As shown, the soft-switching three-level inverter includes three-phase parallel three-level bridge arms and three AC output filter inductors. It should be noted that... Figure 2 In the three-phase parallel three-level bridge arm, the three-level bridge arm is exemplified by a T-type configuration. However, the multi-mode modulation method provided in this embodiment can be applied to inverters with T-type, ANPC-type, or flying capacitor-type three-level structures. Therefore, this embodiment does not impose any limitations on the three-level structure. Furthermore, the switching transistors used in this inverter can be IGBTs or MOSFETs, and this embodiment also does not impose any limitations on this. The three-phase parallel three-level bridge arm includes three pairs of three-level bridge arms and three pairs of differential-mode inductors, and one pair of three-level bridge arms (e.g., as shown in the original text). Figure 2 The bridge arm 1 and bridge arm 2 of phase a are shown, and a pair of differential mode inductors (e.g., ... Figure 2 The L phase shown is a a1 and L a2 This forms a single-phase three-level bridge arm. In this single-phase three-level bridge arm, the output terminal of each three-level bridge arm is connected to the first terminal of a differential-mode inductor, and the second terminals of two differential-mode inductors are connected together. The connection between the two differential-mode inductors serves as the output terminal of the single-phase three-level bridge arm, which is then connected to an AC output filter inductor L. fx Connected.

[0020] In some embodiments, Figure 2 The relevant parameters for the topology shown can be: rated capacity S =20kVA; DC input voltage V dc =800V; AC output voltage V o =220V (RMS); Output frequency f o =50 Hz; Switching frequency f s =150kHz; AC output filter inductor L fx =100μH.

[0021] Based on this soft-switching three-level inverter, various preset modulation modes can be set for each phase three-level bridge arm under different operating conditions characterized by different real-time operating power and different real-time phase information. It should be noted that each preset modulation mode can be independently modulated for a single-phase three-level bridge arm in the soft-switching three-level inverter; that is, the three-phase three-level bridge arms in the soft-switching three-level inverter are modulated independently. Under different operating conditions, the modulation modes used for different phase three-level bridge arms may be the same or different. Here, real-time operating power refers to the real-time operating power of a single-phase three-level bridge arm, and real-time phase information is the real-time phase of a sinusoidal modulated wave signal generated based on the current of the AC filter inductor connected to the output terminal of that single-phase three-level bridge arm.

[0022] For any three-level bridge arm of the inverter, under different operating conditions, loss analysis is performed after modulation according to the aforementioned preset modulation modes. Then, an index of the modulation mode with minimum loss under each operating condition is created, thus constructing an index table. As can be seen, this index table stores the modulation modes with minimum loss under various operating conditions. A schematic diagram of the index table is shown below. Figure 3 As shown.

[0023] During actual operation of the soft-switching three-level inverter, for any phase three-level bridge arm, the real-time operating power of that phase three-level bridge arm and the real-time phase information of the sinusoidal modulation wave signal generated based on the current of the AC filter inductor connected to the output terminal of that phase three-level bridge arm can be obtained. The aforementioned index table is then searched according to this real-time operating power and real-time phase information to select the modulation mode with the lowest loss at that moment.

[0024] In some embodiments, the preset modulation mode may include a first mode, wherein the specific modulation process of the first mode for any phase three-level bridge arm includes: Drive signals are generated for the first and second three-level bridge arms in this phase, respectively. These signals drive the first and second three-level bridge arms to operate, achieving the zero-voltage turn-on soft-switching condition of the soft-switching three-level inverter. The drive signals for the first and second three-level bridge arms ensure that the operation of the second three-level bridge arm is always delayed compared to the first, causing the current directions of the two differential-mode inductors connected to the first and second three-level bridge arms to change alternately. The drive signal levels for the first and second three-level bridge arms include +1, 0, and -1.

[0025] With the above modulation method, the current of the AC output filter inductor connected in this phase is greater than the minimum reverse current I required for the output capacitor of the switching transistor to fully charge and discharge. ZVS Therefore, it can achieve the zero-voltage turn-on soft-switching condition of a soft-switching three-level inverter.

[0026] In some embodiments, for the first three-level bridge arm, in order to generate a drive signal corresponding to the first three-level bridge arm and drive the first three-level bridge arm to operate based on the drive signal, the current of the differential-mode inductor connected to the first and second three-level bridge arms and the current of the AC filter inductor connected to the output terminal of the phase three-level bridge arm can be obtained. Subsequently, a sinusoidal modulation wave is generated based on the current of the AC filter inductor connected to the output terminal of the phase three-level bridge arm, and a three-level carrier modulation method is used to intersect the sinusoidal modulation wave with positive and negative triangular carriers to generate the drive signal corresponding to the first three-level bridge arm. Specifically, the currents of the two differential-mode inductors within the phase can be obtained. i Lx1 , i Lx2 (like Figure 1 The differential mode inductor current of phase a shown i La1 , i La2 and AC output filter inductor current i Lfx ( i Lfx = i Lx1 + i Lx2 In phase a, i Lx1 Right now i La1 , i Lx2 Right now i La2The measured i Lfx With a pre-given reference current i refx Calculate the difference and send the difference value to the corresponding PR controller G. ix (s) The controller outputs a sinusoidal modulated wave. v mx The sinusoidal modulated wave v mx The positive and negative triangular carriers output by the carrier generator intersect to generate a drive signal corresponding to the first three-level bridge arm, thereby driving the first three-level bridge arm. The drive signal levels corresponding to the first three-level bridge arm include +1, 0, and -1.

[0027] In other embodiments, for the second three-level bridge arm, in the sinusoidal modulation wave v mx Within a corresponding switching cycle, the first three-level bridge arm is driven by the drive signal corresponding to it, causing it to operate first and creating a level difference between it and the second three-level bridge arm. Under this level difference, the currents of the differential-mode inductors connected to the two three-level bridge arms decrease from their peak values ​​to zero and rise from zero to their peak values, respectively. After the current exchange between the differential-mode inductors connected to the two three-level bridge arms is complete—that is, when the current of one differential-mode inductor has decreased to zero and the current of the other has risen to its peak value—the level of the drive signal corresponding to the second three-level bridge arm is switched, generating a corresponding drive signal. The level of the drive signal corresponding to the second three-level bridge arm switches between +1 and 0 and between -1 and 0.

[0028] Furthermore, in sinusoidal modulated waves v mx Within a corresponding switching cycle, when the sinusoidal modulation wave v mx When in the positive half-cycle, if the triggering condition i is met Lx1 >i Lx2 And i Lx2 <-I ZVS Then, the level of the drive signal corresponding to the second three-level bridge arm is set to +1. If the trigger condition i is met... Lx1 Lx2 And i Lx1 <-I ZVS Then, the level of the drive signal corresponding to the second three-level bridge arm is set to 0; when the sinusoidal modulation wave v mx When in the negative half-cycle, if the trigger condition i is met... Lx1 Lx2 And i Lx2 >I ZVS ​​Then, the level of the drive signal corresponding to the second three-level bridge arm is set to -1. If the trigger condition i is met... Lx1 >i Lx2 And i Lx1 >I ZVS Then the level of the drive signal corresponding to the second three-level bridge arm will be set to 0.

[0029] As can be seen, the first mode generates drive signals corresponding to the first and second three-level bridge arms respectively, so that the action of the second three-level bridge arm is always delayed compared to the first three-level bridge arm. This causes the current direction of the two differential mode inductors connected to the first and second three-level bridge arms to change alternately, thereby changing the current flow direction when the switching transistor is turned on. This allows each switching transistor in the inverter to achieve the ZVS soft switching condition, reducing system losses under specific operating conditions. Furthermore, the modulation method of this embodiment is universal and can be applied to three-phase and single-phase systems. It is not constrained by the type of device or converter, and has strong versatility.

[0030] In other embodiments, the preset modulation mode further includes a second mode. When modulation is performed in this second mode, the driving signals corresponding to the first and second three-level bridge arms in any phase three-level bridge arm are generated according to the driving signal generation method for the first three-level bridge arm in the first mode. That is, a sinusoidal modulated wave is obtained according to the method in the first mode. v mx The sinusoidal modulation wave is intersected with the positive and negative triangular carrier waves to generate a driving signal, and the first and second three-level bridge arms in the three-level bridge arm of the phase operate in unison according to the driving signal.

[0031] In other embodiments, the preset modulation mode also includes a third mode, which is similar to the first mode, but changes the three-level commutation in the first mode, where the level of the drive signal switches between +1, 0, and -1, to a two-level commutation, where the level switches between +1 and -1.

[0032] Specifically, based on a method similar to the first mode, drive signals are generated for the first and second three-level bridge arms in any phase three-level bridge arm. These drive signals drive the first and second three-level bridge arms respectively, achieving the zero-voltage turn-on soft-switching condition of the soft-switching three-level inverter. The drive signals for the first and second three-level bridge arms ensure that the action of the second three-level bridge arm is always delayed compared to the first, causing the current directions of the two differential-mode inductors connected to the first and second three-level bridge arms to change alternately. Unlike the first mode, the drive signals for the first and second three-level bridge arms include levels of +1 and -1.

[0033] In other embodiments, the current of the differential-mode inductor connected to the first and second three-level bridge arms and the current of the AC output filter inductor connected to the output terminal of the three-level bridge arm can be obtained. A sinusoidal modulation wave is generated based on the current of the AC output filter inductor connected to the output terminal of the three-level bridge arm. v mx And for sinusoidal modulated waves v mx The driving signal corresponding to the first three-level bridge arm is generated by intersecting the triangular carrier with a two-level carrier modulation method. Therefore, the driving signal corresponding to the first three-level bridge arm will not output a 0 level, but only output two levels: +1 and -1.

[0034] In sinusoidal modulation wave v mx Within a corresponding switching cycle, the first three-level bridge arm is driven by the drive signal corresponding to it, causing it to operate first. This creates a level difference between the first and second three-level bridge arms. Under the influence of this level difference, the current in the differential-mode inductors connected to the two three-level bridge arms decreases from its peak value to zero and then rises from zero to its peak value, respectively. After the current exchange between the differential-mode inductors connected to the two three-level bridge arms is complete, the level of the drive signal corresponding to the second three-level bridge arm is switched. Unlike the first mode, the level of the drive signal corresponding to the second three-level bridge arm switches between +1 and -1.

[0035] Furthermore, in sinusoidal modulated waves v mx Within a corresponding switching cycle, when the sinusoidal modulation wave v mx When in the positive half-cycle, if the triggering condition i is met Lx1 >i Lx2 And i Lx2 <-I ZVS Then, the level of the drive signal corresponding to the second three-level bridge arm is set to +1. If the trigger condition i is met... Lx1 Lx2 And i Lx1 <-I ZVS Then, the level of the drive signal corresponding to the second three-level bridge arm is set to -1; when the sinusoidal modulation wave v mx When in the negative half-cycle, if the trigger condition i is met... Lx1 Lx2 And i Lx2 >I ZVS Then, the level of the drive signal corresponding to the second three-level bridge arm is set to -1. If the trigger condition i is met... Lx1 >i Lx2 And i Lx1 >I ZVS ​​Then the level of the drive signal corresponding to the second three-level bridge arm will be set to +1.

[0036] In other embodiments, the preset modulation mode further includes a fourth mode. When this fourth mode is used for modulation, the driving signals corresponding to the first and second three-level bridge arms in any phase three-level bridge arm are generated according to the driving signal generation method for the first three-level bridge arm in the third mode. That is, a sinusoidal modulated wave is obtained according to the method in the third mode. v mx The sinusoidal modulated wave is intersected with the triangular carrier using a two-level carrier modulation method to generate a driving signal. The first three-level bridge arm and the second three-level bridge arm in the three-level bridge arm operate in unison according to the driving signal.

[0037] Figures 4-7 The waveforms of the differential-mode inductor current and AC filter inductor current of phase a are shown when operating independently in the first, second, third, and fourth modulation modes. As can be seen from the figures, the differential-mode inductor current waveform has its own characteristics for each modulation mode, but the AC filter inductor current has a relatively high sinusoidal degree. The four modulation methods provided in this embodiment can operate independently and are feasible. When the first and third modes are operated independently, due to the ZVS soft-switching effect, the switching transistors have no turn-on losses, resulting in low losses under high switching frequency conditions. When the second and fourth modes are operated independently, because the two bridge arms operate in the same manner, each sharing half of the current, the total conduction loss is even lower, resulting in low losses under high power (i.e., high output current) conditions.

[0038] Figure 8 The waveforms of the differential mode inductor current and the AC filter inductor current when the multi-mode modulation method provided in this embodiment of the invention is used are shown. Each mode of the multi-mode modulation method provided in this embodiment of the invention can work relatively independently and switch seamlessly within its optimal working range in one cycle, ensuring the overall feasibility of the multi-mode modulation method.

[0039] Figure 9 The power loss generated by operating the four working modes individually and the multi-mode modulation method is shown. The multi-mode modulation method provided in this embodiment of the invention generates the lowest loss and is effective. The loss is reduced by 14.4% compared with traditional hard-switching modulation (i.e., the second mode is operated alone) and by 21.1% compared with ZVS soft-switching modulation (i.e., the first mode is operated alone).

[0040] In summary, by providing the aforementioned multi-mode modulation method for soft-switching three-level inverters, an index table containing the modulation mode index with the minimum loss under each operating condition can be used to select the modulation mode with the minimum loss for each phase three-level bridge arm at any given time, thereby improving the efficiency of the entire system across the entire operating range. Furthermore, this multi-mode modulation method is versatile; the three-level structure used can be T-type, ANPC-type, or flying capacitor-type topology, and the switching devices can be IGBTs or MOSFETs. The provided modulation method can be applied to three-phase and single-phase systems, thus it is not constrained by topology, device type, or inverter type, exhibiting strong versatility.

[0041] Furthermore, embodiments of the present invention also provide a controller for executing the multi-mode modulation method as provided in any of the above embodiments.

[0042] This invention provides an electronic device, including: a computer-readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is configured to read executable instructions stored in the computer-readable storage medium and execute the method as described in any of the above embodiments.

[0043] This invention provides a computer-readable storage medium storing computer instructions that cause a processor to perform the method described in any of the above embodiments.

[0044] This invention provides a computer program product, including a computer program or instructions, which, when executed by a processor, implement the method described in any of the above embodiments.

[0045] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-mode modulation method for a soft-switching three-level inverter, characterized in that, include: For any three-level bridge arm in a soft-switching three-level inverter, during actual operation of the soft-switching three-level inverter, the real-time operating power and real-time phase information of the sinusoidal modulation wave signal of any three-level bridge arm are obtained. The sinusoidal modulated wave signal is generated based on the current of the AC filter inductor connected to the output terminal of any of the three-level bridge arms. Based on the real-time operating power and the real-time phase information, a preset index table is retrieved, and the modulation mode with the minimum inverter loss at that moment is selected for operation. The index table is obtained by performing loss analysis after modulating any phase three-level bridge arm according to multiple preset modulation modes under different operating conditions, and establishing an index of the modulation mode with the minimum loss for each operating condition. Any operating condition is represented by the real-time operating power and the real-time phase information. The soft-switching three-level inverter includes three-phase parallel three-level bridge arms and three AC output filter inductors, and the three-phase three-level bridge arms are independently modulated; the three-phase parallel three-level bridge arms include three pairs of three-level bridge arms and three pairs of differential-mode inductors, and one pair of three-level bridge arms and one pair of differential-mode inductors form one phase three-level bridge arm; in one phase three-level bridge arm, the output terminal of each three-level bridge arm is connected to the first terminal of a differential-mode inductor, the second terminals of two differential-mode inductors are connected, and the connection terminal between the two differential-mode inductors serves as the output terminal of one phase three-level bridge arm, and the output terminal of one phase three-level bridge arm is connected to an AC output filter inductor.

2. The multi-mode modulation method as described in claim 1, characterized in that, The first mode among the multiple preset modulation modes modulates any three-level bridge arm based on the following method: Generate driving signals corresponding to the first three-level bridge arm and the second three-level bridge arm in any phase three-level bridge arm, so as to drive the first three-level bridge arm and the second three-level bridge arm to operate based on the driving signals corresponding to the first three-level bridge arm and the second three-level bridge arm respectively, so as to achieve the zero-voltage turn-on soft-switching condition of the soft-switching three-level inverter. The driving signals corresponding to the first and second three-level bridge arms respectively enable the operation of the second three-level bridge arm to always be delayed compared to the first three-level bridge arm, resulting in the current direction of the two differential mode inductors connected to the first and second three-level bridge arms changing alternately; the driving signal levels corresponding to the first and second three-level bridge arms respectively include +1, 0 and -1.

3. The multi-mode modulation method as described in claim 2, characterized in that, The step of generating driving signals corresponding to the first and second three-level bridge arms in any phase three-level bridge arm, and driving the first and second three-level bridge arms to operate based on the driving signals corresponding to the first and second three-level bridge arms respectively, specifically includes: Obtain the current of the differential mode inductor connected to the first three-level bridge arm and the second three-level bridge arm in any of the three-phase bridge arms, and the current of the AC output filter inductor connected to the output terminal of any of the three-phase bridge arms. A sinusoidal modulation wave is generated based on the current of the AC output filter inductor connected to the output terminal of any of the three-level bridge arms, and a driving signal corresponding to the first three-level bridge arm is generated using a three-level carrier modulation method for the sinusoidal modulation wave. Within one switching cycle corresponding to the sinusoidal modulation wave, the first three-level bridge arm is driven to operate first based on the drive signal corresponding to the first three-level bridge arm, so that there is a level difference between the first three-level bridge arm and the second three-level bridge arm. Under the influence of the level difference, the current of the differential mode inductor connected to the two three-level bridge arms drops from the peak value to zero and rises from zero to the peak value, respectively. After the current exchange of the differential mode inductor connected to the two three-level bridge arms is completed, the level of the drive signal corresponding to the second three-level bridge arm is switched, and the level of the drive signal corresponding to the second three-level bridge arm switches between +1 and 0 and between -1 and 0.

4. The multi-mode modulation method as described in claim 3, characterized in that, After the current exchange with the differential mode inductor connected to the two three-level bridge arms is completed, the level of the drive signal corresponding to the second three-level bridge arm is switched, specifically including: Within one switching cycle corresponding to the sinusoidal modulation wave, when the sinusoidal modulation wave is in the positive half-cycle, if the trigger condition i is satisfied... Lx1 >i Lx2 And i Lx2 <-I ZVS Then, the level of the drive signal corresponding to the second three-level bridge arm is set to +1. If the trigger condition i is met... Lx1 Lx2 And i Lx1 <-I ZVS Then, the level of the driving signal corresponding to the second three-level bridge arm is set to 0; when the sinusoidal modulation wave is in the negative half-cycle, if the trigger condition i is met... Lx1 Lx2 And i Lx2 >I ZVS Then, the level of the drive signal corresponding to the second three-level bridge arm is set to -1. If the trigger condition i is met... Lx1 >i Lx2 And i Lx1 >I ZVS Then the level of the drive signal corresponding to the second three-level bridge arm is set to 0;​​ Among them, i Lx1 i is the current of the differential mode inductor connected to the first three-level bridge arm. Lx2 For the current of the differential mode inductor connected to the second three-level bridge arm, I ZVS To meet the minimum reverse current required for the complete charging and discharging of the output capacitor of the switching transistor.

5. The multi-mode modulation method as described in claim 3 or 4, characterized in that, In the second mode among the multiple preset modulation modes, the driving signals corresponding to the first three-level bridge arm and the second three-level bridge arm in any phase three-level bridge arm are generated in accordance with the driving signal generation method corresponding to the first three-level bridge arm in the first mode.

6. The multi-mode modulation method as described in claim 1, characterized in that, The third mode among the various preset modulation modes modulates any three-level bridge arm based on the following method: Generate driving signals corresponding to the first three-level bridge arm and the second three-level bridge arm in any phase three-level bridge arm, so as to drive the first three-level bridge arm and the second three-level bridge arm to operate based on the driving signals corresponding to the first three-level bridge arm and the second three-level bridge arm respectively, so as to achieve the zero-voltage turn-on soft-switching condition of the soft-switching three-level inverter. The driving signals corresponding to the first and second three-level bridge arms respectively enable the operation of the second three-level bridge arm to always be delayed compared to the first three-level bridge arm, resulting in the current direction of the two differential mode inductors connected to the first and second three-level bridge arms changing alternately; the driving signal levels corresponding to the first and second three-level bridge arms respectively include +1 and -1.

7. The multi-mode modulation method as described in claim 6, characterized in that, The step of generating driving signals corresponding to the first and second three-level bridge arms in any phase three-level bridge arm, and driving the first and second three-level bridge arms to operate based on the driving signals corresponding to the first and second three-level bridge arms respectively, specifically includes: Obtain the current of the differential mode inductor connected to the first three-level bridge arm and the second three-level bridge arm in any of the three-phase bridge arms, and the current of the AC output filter inductor connected to the output terminal of any of the three-phase bridge arms. A sinusoidal modulation wave is generated based on the current of the AC output filter inductor connected to the output terminal of any of the three-level bridge arms, and a driving signal corresponding to the first three-level bridge arm is generated based on the two-level carrier modulation method for the sinusoidal modulation wave. Within one switching cycle corresponding to the sinusoidal modulation wave, the first three-level bridge arm is driven to operate first based on the drive signal corresponding to the first three-level bridge arm, so that there is a level difference between the first three-level bridge arm and the second three-level bridge arm. Under the influence of the level difference, the current of the differential mode inductor connected to the two three-level bridge arms drops from the peak value to zero and rises from zero to the peak value, respectively. After the current exchange of the differential mode inductor connected to the two three-level bridge arms is completed, the level of the drive signal corresponding to the second three-level bridge arm is switched. The level of the drive signal corresponding to the second three-level bridge arm switches between +1 and -1.

8. The multi-mode modulation method as described in claim 7, characterized in that, After the current exchange with the differential mode inductor connected to the two three-level bridge arms is completed, the level of the drive signal corresponding to the second three-level bridge arm is switched, specifically including: Within one switching cycle corresponding to the sinusoidal modulation wave, when the sinusoidal modulation wave is in the positive half-cycle, if the trigger condition i is satisfied... Lx1 >i Lx2 And i Lx2 <-I ZVS Then, the level of the drive signal corresponding to the second three-level bridge arm is set to +1. If the trigger condition i is met... Lx1 Lx2 And i Lx1 <-I ZVS Then, the level of the driving signal corresponding to the second three-level bridge arm is set to -1; when the sinusoidal modulation wave is in the negative half-cycle, if the trigger condition i is met... Lx1 Lx2 And i Lx2 >I ZVS Then, the level of the drive signal corresponding to the second three-level bridge arm is set to -1. If the trigger condition i is met... Lx1 >i Lx2 And i Lx1 >I ZVS Then the level of the drive signal corresponding to the second three-level bridge arm is set to +1;​​ Among them, i Lx1 i is the current of the differential mode inductor connected to the first three-level bridge arm. Lx2 For the current of the differential mode inductor connected to the second three-level bridge arm, I ZVS To meet the minimum reverse current required for the complete charging and discharging of the output capacitor of the switching transistor.

9. The multi-mode modulation method as described in claim 7 or 8, characterized in that, In the fourth mode among the various preset modulation modes, the driving signals corresponding to the first three-level bridge arm and the second three-level bridge arm in any phase three-level bridge arm are generated according to the driving signal generation method corresponding to the first three-level bridge arm in the third mode.

10. A controller, characterized in that, Used to perform the multi-mode modulation method as described in any one of claims 1-9.

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