A three-level topology modulation control method, system, device and storage medium

Abstract

The application discloses a three-level topology modulation control method, system and device and a storage medium, and relates to the control field of power electronic technology. In the scheme, the trigger condition for switching between each carrier mode modulation mode is determined based on each carrier mode modulation mode, and when the trigger condition for switching from the current carrier mode modulation mode to the target carrier mode modulation mode is met, the driving waveform after the carrier of the target carrier mode modulation mode is modulated based on the target modulation wave is used to control the three-level topology, that is, by switching the carrier mode modulation mode, different carrier mode modulation modes are selected for modulation control in the full modulation ratio range. It can be seen that, in the application, the carrier mode modulation mode with the best common-mode voltage suppression effect is selected at different modulation ratios according to the common-mode voltage suppression conditions of different carrier mode modulation modes in the full modulation ratio range, so that the common-mode voltage suppression in the full modulation ratio range is realized.

Description

Technical Field

[0001] This invention relates to the field of power electronics control, and in particular to a three-level topology modulation control method, system, device, and storage medium. Background Technology

[0002] In the modulation control of a three-level topology, the main considerations are midpoint voltage balance control, common-mode voltage suppression, and PWM (Pulse width modulation) waveform control. The modulation methods mainly include SPWM (Sinusoidal Pulse Width Modulation) and SVPWM (Space Vector Pulse Width Modulation).

[0003] To achieve midpoint voltage balance control, zero-sequence voltage injection can be used in SPWM modulation, while SVPWM space vector modulation can be achieved by selecting appropriate small vectors according to different current directions. For common-mode voltage suppression, carrier-stacked SPWM modulation can be selected in SPWM modulation, that is, common-mode voltage is suppressed by carrier stacking. In SVPWM space vector modulation, common-mode voltage is suppressed by vector selection or virtual vector construction, or by using additional hardware to isolate or filter common-mode voltage, such as adding a grounding carbon brush to the shaft, isolation transformer, passive filter or active filter, etc.

[0004] However, carrier-layered SPWM modulation includes different carrier mode modulation methods, specifically carrier-in-phase, carrier-out-of-phase, and carrier-phase-shifted SPWM modulation methods. Carrier-in-phase SPWM modulation cannot achieve common-mode voltage suppression. Due to the injection of zero-sequence voltage, neither carrier-out-of-phase nor carrier-phase-shifted SPWM modulation methods can independently achieve complete common-mode voltage suppression across the entire modulation ratio range. For example, in the low modulation ratio stage, the common-mode voltage suppression effect of carrier-out-of-phase SPWM modulation is poor, and in the high modulation ratio stage, the common-mode voltage suppression effect of carrier-phase-shifted SPWM modulation is poor. The algorithm for selecting the SVPWM space vector modulation method through vector selection or constructing a virtual vector is complex and difficult to implement. Adding hardware structures to achieve common-mode voltage suppression will significantly increase the system cost.

[0005] In summary, designing a simple method to suppress common-mode voltage across the entire modulation ratio range is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a three-level topology modulation control method, system, device, and storage medium, wherein by selecting the carrier mode modulation method with the best common-mode voltage suppression effect under different modulation ratios based on the suppression of common-mode voltage of different carrier mode modulation methods across the full modulation ratio range, common-mode voltage suppression is achieved across the full modulation ratio range.

[0007] To solve the above technical problems, the present invention provides a three-level topology modulation control method, comprising:

[0008] The triggering conditions for switching between the various carrier mode modulation schemes are determined based on the modulation ratio range in which the common-mode voltage is less than the desired common-mode voltage across the full modulation ratio range for each carrier mode modulation scheme.

[0009] Based on the current modulation ratio, determine whether the triggering condition for switching from the current carrier mode modulation scheme to the target carrier mode modulation scheme is met;

[0010] If the conditions are met, the current carrier mode modulation method is switched to the target carrier mode modulation method, and the three-level topology is controlled based on the driving waveform after modulating the carrier of the target carrier mode modulation method according to the target modulation wave.

[0011] Preferably, the triggering condition for switching between each carrier mode modulation scheme is determined based on the modulation ratio range where the common-mode voltage is less than the desired common-mode voltage across the entire modulation ratio range for each carrier mode modulation scheme, including:

[0012] Determine the common-mode voltage of each of the carrier mode modulation schemes within the full modulation ratio range;

[0013] Determine the target modulation ratio range in which the common-mode voltage of each of the carrier mode modulation schemes is less than the desired common-mode voltage;

[0014] Hysteresis selection is performed based on the target modulation ratio range of each of the aforementioned carrier mode modulation schemes;

[0015] The triggering conditions for switching between the various carrier mode modulation schemes are determined based on the hysteresis.

[0016] Preferably, hysteresis selection is performed based on the target modulation ratio range of each of the carrier mode modulation schemes, including:

[0017] The maximum and minimum modulation ratio values ​​of the hysteresis loop are determined based on the target modulation ratio range of each of the carrier modes.

[0018] Preferably, determining the triggering condition for switching between each of the carrier mode modulation schemes based on the hysteresis includes:

[0019] Based on the target modulation ratio range of each of the carrier mode modulation schemes, the switching conditions between each of the carrier mode modulation schemes are set as follows: when the modulation ratio increases from the minimum modulation ratio value less than the hysteresis to the maximum modulation ratio value, or when the modulation ratio decreases from the maximum modulation ratio value greater than the hysteresis to the minimum modulation ratio value.

[0020] Preferably, before switching the current carrier mode modulation scheme to the target carrier mode modulation scheme, and controlling the three-level topology based on the drive waveform obtained by modulating the carrier of the target carrier mode modulation scheme with the target modulation wave, the method further includes:

[0021] The initial modulated wave is generated based on the modulation ratio and the modulation scheme of each of the carrier modules;

[0022] The target modulation wave is obtained based on the initial modulation wave.

[0023] Preferably, obtaining the target modulated wave based on the initial modulated wave includes:

[0024] Determine the zero-sequence voltage and third harmonic for midpoint voltage balance control of the three-level topology;

[0025] The instantaneous value of the target modulation wave is determined based on the initial modulation wave, the zero-sequence voltage, and the third harmonic, thereby determining the target modulation wave.

[0026] Preferably, switching the current carrier mode modulation scheme to the target carrier mode modulation scheme, and controlling the three-level topology based on the target modulation wave after modulating the carrier of the target carrier mode modulation scheme with the drive waveform, includes:

[0027] The current carrier mode modulation scheme is switched to the target carrier mode modulation scheme, and the carrier of the target carrier mode modulation scheme is modulated based on the instantaneous value;

[0028] Determine the duty cycle values ​​of each phase after the carrier is modulated;

[0029] The driving waveform is generated based on the duty cycle value of each phase;

[0030] The three-level topology is controlled based on the driving waveform.

[0031] To solve the above-mentioned technical problems, the present invention provides a three-level topology modulation control system, comprising:

[0032] The determining unit is used to determine the triggering conditions for switching between the various carrier mode modulation methods based on the modulation ratio range in which the common-mode voltage of each carrier mode modulation method is less than the desired common-mode voltage across the full modulation ratio range.

[0033] The judgment unit is used to determine, based on the current modulation ratio, whether the triggering condition for switching from the current carrier mode modulation scheme to the target carrier mode modulation scheme is met;

[0034] The control unit is used to switch the current carrier mode modulation mode to the target carrier mode modulation mode when the triggering condition is met, and to control the three-level topology based on the driving waveform after modulating the carrier of the target carrier mode modulation mode with the target modulation wave.

[0035] To solve the above-mentioned technical problems, the present invention provides a three-level topology modulation control device, comprising:

[0036] Memory, used to store computer programs;

[0037] A processor is used to implement the steps of the three-level topology modulation control method as described above when executing the computer program.

[0038] To address the aforementioned technical problems, the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the three-level topology modulation control method described above.

[0039] This application provides a three-level topology modulation control method, system, device, and storage medium, relating to the field of power electronics control technology. In this scheme, the triggering conditions for switching between different carrier mode modulation methods are first determined based on each carrier mode modulation method. When the triggering condition for switching from the current carrier mode modulation method to the target carrier mode modulation method is met, the three-level topology is controlled based on the driving waveform obtained by modulating the carrier of the target carrier mode modulation method with the target modulation wave. That is, by switching the carrier mode modulation methods, different carrier mode modulation methods are selected for modulation control within the full modulation ratio range. It can be seen that this application achieves common-mode voltage suppression across the entire modulation ratio range by selecting the carrier mode modulation method with the best common-mode voltage suppression effect at different modulation ratios, based on the common-mode voltage suppression performance of different carrier mode modulation methods within the full modulation ratio range. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the prior art and embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 A flowchart illustrating a three-level topology modulation control method provided by the present invention;

[0042] Figure 2 A schematic diagram of a three-level topology circuit structure provided by the present invention;

[0043] Figure 3 The diagram shows the common-mode voltage waveforms under carrier in-phase stacked SPWM modulation and carrier in-reverse stacked SPWM modulation.

[0044] Figure 4 The diagram shows the common-mode voltage waveforms under carrier in-phase stacked SPWM modulation and carrier phase-shift stacked SPWM modulation.

[0045] Figure 5 This is a schematic diagram of the common-mode voltage waveform under carrier in-phase stacked SPWM modulation across the entire modulation ratio range.

[0046] Figure 6 A schematic diagram of the common-mode voltage waveform under carrier-reverse stacked SPWM modulation mode across the entire modulation ratio range;

[0047] Figure 7 A schematic diagram of the common-mode voltage waveform under carrier phase-shift stacked SPWM modulation mode across the entire modulation ratio range;

[0048] Figure 8 This diagram illustrates the common-mode voltage waveforms of carrier-inverting stacked SPWM modulation and carrier-phase-shifting stacked SPWM modulation at low modulation ratios.

[0049] Figure 9 This is a schematic diagram of the common-mode voltage waveform at a high modulation ratio for carrier inverted stacked SPWM modulation and carrier phase-shifted stacked SPWM modulation.

[0050] Figure 10 This is a schematic diagram of the common-mode voltage waveform under segmented modulation ratios for carrier inverted stacked SPWM modulation and carrier phase-shifted stacked SPWM modulation.

[0051] Figure 11 A schematic diagram of hysteresis selection provided by the present invention;

[0052] Figure 12A schematic diagram of a target modulation wave and a driving waveform provided by the present invention;

[0053] Figure 13 This is a schematic diagram of a three-level topology modulation control system provided by the present invention;

[0054] Figure 14 This is a schematic diagram of a three-level topology modulation control device provided by the present invention. Detailed Implementation

[0055] The core of this invention is to provide a three-level topology modulation control method, system, device, and storage medium, wherein by selecting the carrier mode modulation method with the best common-mode voltage suppression effect under different modulation ratios based on the suppression of common-mode voltage of different carrier mode modulation methods within the full modulation ratio range, common-mode voltage suppression is achieved within the full modulation ratio range.

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0057] Please refer to Figure 1 , Figure 1 This invention provides a flowchart illustrating a three-level topology modulation control method, which includes:

[0058] S11: Determine the triggering conditions for switching between each carrier mode modulation method based on the modulation ratio range where the common-mode voltage is less than the expected common-mode voltage across the full modulation ratio range for each carrier mode modulation method.

[0059] In existing technologies, when modulating and controlling a three-level topology, carrier-layered SPWM modulation, SVPWM space vector modulation, or peripheral hardware structures are typically used.

[0060] However, in order to achieve midpoint voltage balance control for the three-level topology, the carrier-in-phase SPWM modulation method in the carrier-layered SPWM modulation method will have a large common-mode voltage after the zero-sequence voltage is added. The carrier-reverse SPWM modulation method can only suppress the common-mode voltage at high modulation ratios, and there will still be a high common-mode voltage at low modulation ratios. The carrier-phase-shifted SPWM modulation method can suppress the common-mode voltage at low modulation ratios, but there will still be a high common-mode voltage at high modulation ratios. The SVPWM space vector modulation method requires vector selection or virtual vector construction. Moreover, when selecting the vector, in addition to considering the suppression of common-mode voltage, the midpoint voltage balance control must also be considered, which makes the implementation more complex. When the peripheral hardware structure suppresses the common-mode voltage, the cost is high.

[0061] To address the aforementioned technical issues, this application achieves common-mode voltage suppression under the premise of midpoint voltage balance control. It switches and selects the modulation scheme of each carrier mode across the entire modulation ratio range, utilizing the common-mode voltage suppression effect of each carrier mode modulation scheme at different modulation ratios to ensure the suppression of common-mode voltage in the three-level topology across the entire modulation ratio range.

[0062] Specifically, the common-mode voltage of each carrier mode modulation method is first determined based on the modulation ratio range within the full modulation ratio range where the common-mode voltage is less than the desired common-mode voltage, and the triggering condition for switching between each carrier mode modulation method is determined based on the modulation ratio range corresponding to each carrier mode modulation method.

[0063] The carrier mode modulation method can include, but is not limited to, carrier inverse stacked SPWM modulation method and carrier phase shift stacked SPWM modulation method. The triggering conditions include the triggering conditions for switching from carrier inverse stacked SPWM modulation method to carrier phase shift stacked SPWM modulation method and the triggering conditions for switching from carrier phase shift stacked SPWM modulation method to carrier inverse stacked SPWM modulation method. By switching the carrier mode modulation method, common mode voltage suppression is achieved across the entire modulation ratio range.

[0064] S12: Determine whether the triggering condition for switching from the current carrier mode modulation method to the target carrier mode modulation method is met based on the current modulation ratio;

[0065] After determining the triggering conditions for switching between various carrier mode modulation schemes, it is determined whether the triggering conditions for switching from the current carrier mode modulation scheme to the target carrier mode modulation scheme are met based on the current modulation ratio. For example, when the current carrier mode modulation scheme is carrier inverse layered SPWM modulation, it is determined whether the triggering conditions for switching from carrier inverse layered SPWM modulation to carrier phase-shift layered SPWM modulation are met based on the current modulation ratio; similarly, when the current carrier mode modulation scheme is carrier phase-shift layered SPWM modulation, it is determined whether the triggering conditions for switching from carrier phase-shift layered SPWM modulation to carrier inverse layered SPWM modulation are met based on the current modulation ratio.

[0066] S13: If satisfied, switch the current carrier mode modulation mode to the target carrier mode modulation mode, and control the three-level topology based on the target modulation wave and the modulated wave of the target carrier mode modulation mode carrier after modulation.

[0067] If the triggering condition is met, the current carrier mode modulation method is switched to the target carrier mode modulation method, and the carrier of the target carrier mode modulation method is determined. The carrier is modulated based on the target modulation wave, and the three-level topology is controlled based on the generated driving waveform to achieve modulation control of the three-level topology and ensure the suppression of common-mode voltage across the entire modulation ratio range.

[0068] It should be noted that, please refer to Figure 2 , Figure 2 This invention provides a schematic diagram of a three-level topology circuit structure. The three-level topology can be, but is not limited to, ANPC, INPC, and TNPC topologies. When modulating and controlling the three-level topology, with the DC bus voltage Vdc = 1800V, the instantaneous common-mode voltage output values ​​of the three-level topology are: ±Vdc / 2 = ±900V, ±Vdc / 3 = ±600V, ±Vdc / 6 = ±300V, and 0V. The output levels of each phase are defined as P level, 0 level, and N level, respectively. Please refer to... Figure 3 and Figure 4 , Figure 3 The diagram shows the common-mode voltage waveforms under in-phase and out-of-phase SPWM modulation methods. Figure 4The diagram shows the common-mode voltage waveforms under carrier in-phase stacked SPWM modulation and carrier phase-shifted stacked SPWM modulation. mA, mB, and mC represent the three-phase instantaneous values ​​of the target modulation wave, and Vcom is the common-mode voltage. It can be seen that the carrier in-phase stacked SPWM modulation consists of positive and negative carriers symmetrically distributed along the time axis, with the switching period of the switching transistor as the carrier period. All three phases of the modulation wave have the same carrier. The output level signal of the carrier in-phase stacked SPWM modulation includes the modulation of the corresponding phase's modulation wave with the positive and negative carriers of the same phase, resulting in the corresponding P, O, and N levels. The carrier phase-shifted stacked SPWM modulation consists of three sets of in-phase carriers with a phase difference of 120°. The two carriers of each phase are stacked in the same direction around the time axis, with the switching period of the switching transistor as the carrier period. The output level signal of the carrier phase-shifted stacked SPWM modulation includes the modulation of the corresponding phase's modulation wave with the stacked carriers of the same phase, resulting in the corresponding P, O, and N levels.

[0069] Please refer to Figure 5 , Figure 6 and Figure 7 , Figure 5 This is a schematic diagram of the common-mode voltage waveform under carrier in-phase stacked SPWM modulation across the entire modulation ratio range. Figure 6 This is a schematic diagram of the common-mode voltage waveform under carrier-reverse stacked SPWM modulation across the entire modulation ratio range. Figure 7 The diagram shows the common-mode voltage waveform under carrier phase-shift stacked SPWM modulation across the entire modulation ratio range. It can be seen that, within the entire modulation ratio range, the amplitude of the common-mode voltage under carrier in-phase stacked SPWM modulation is ±600V, which is relatively large and has a poor suppression effect. In the high modulation ratio range, the amplitude of the common-mode voltage under carrier inverse stacked SPWM modulation is ±300V, and in the low modulation ratio range, the amplitude of the common-mode voltage under carrier phase-shift stacked SPWM modulation is ±300V.

[0070] Please refer to Figure 8 and Figure 9 , Figure 8 This diagram illustrates the common-mode voltage waveforms at low modulation ratios for carrier-inverting stacked SPWM modulation and carrier-phase-shifting stacked SPWM modulation. Figure 9The diagrams illustrate the common-mode voltage waveforms of carrier-inverted stacked SPWM modulation and carrier-phase-shifted stacked SPWM modulation at high modulation ratios. It is evident that at low modulation ratios, carrier-phase-shifted stacked SPWM modulation is more effective at suppressing common-mode voltage than carrier-inverted stacked SPWM modulation. Conversely, at high modulation ratios, carrier-inverted stacked SPWM modulation is more effective at suppressing common-mode voltage than carrier-phase-shifted stacked SPWM modulation. Therefore, carrier-phase-shifted stacked SPWM modulation can be selected at low modulation ratios, while carrier-inverted stacked SPWM modulation can be selected at high modulation ratios. By switching between the two carrier modulation modes, common-mode voltage suppression can be achieved across the entire modulation ratio range. Please refer to [reference needed]. Figure 10 , Figure 10 The diagram shows the common-mode voltage waveforms of carrier inverted stacked SPWM modulation and carrier phase-shifted stacked SPWM modulation under segmented modulation ratios. It can be seen that, within the full modulation ratio range, the common-mode voltage is suppressed to within ±300V, or ±Vdc / 6. The common-mode voltage suppression effect is better than that of selecting either carrier inverted stacked SPWM modulation or carrier phase-shifted stacked SPWM modulation alone.

[0071] Based on this, the triggering condition for switching from carrier inverse stacked SPWM modulation mode to carrier phase-shift stacked SPWM modulation mode can be that the modulation ratio decreases from a high modulation ratio to a low modulation ratio, and the triggering condition for switching from carrier phase-shift stacked SPWM modulation mode to carrier inverse stacked SPWM modulation mode can be that the modulation ratio increases from a low modulation ratio to a high modulation ratio.

[0072] After switching the carrier mode modulation method, the carrier of the target carrier mode modulation method is modulated based on the target modulation wave. Specifically, when the target carrier mode modulation method is carrier inverse stacked SPWM modulation, the carrier is carrier inverse stacked, that is, the carrier inverse stacked is modulated by the target modulation wave; when the target carrier mode modulation method is carrier phase shift stacked SPWM modulation, the carrier is carrier phase shift stacked, that is, the carrier phase shift stacked is modulated by the target modulation wave.

[0073] In summary, this application achieves common-mode voltage suppression across the entire modulation ratio range by selecting the carrier mode modulation method with the best common-mode voltage suppression effect under different modulation ratios based on the suppression performance of different carrier mode modulation methods within the full modulation ratio range.

[0074] Based on the above embodiments:

[0075] As a preferred embodiment, the triggering conditions for switching between each carrier mode modulation scheme are determined based on the modulation ratio range where the common-mode voltage is less than the desired common-mode voltage across the entire modulation ratio range for each carrier mode modulation scheme, including:

[0076] Determine the common-mode voltage of each carrier mode modulation scheme across the full modulation ratio range;

[0077] Determine the target modulation ratio range within which the common-mode voltage of each carrier mode modulation scheme is less than the desired common-mode voltage;

[0078] Hysteresis selection is performed based on the target modulation ratio range of each carrier mode modulation scheme;

[0079] The triggering conditions for switching between different carrier mode modulation schemes are determined based on hysteresis.

[0080] When switching carrier mode modulation methods based on the current modulation ratio, in order to avoid repeated switching of carrier mode modulation methods due to unstable changes in the modulation ratio, this embodiment performs hysteresis selection based on the common-mode voltage suppression effect of each carrier mode modulation method in the full modulation ratio range. That is, it determines whether the carrier mode modulation method needs to be switched based on the hysteresis, thus avoiding the instability of modulation control caused by setting a modulation ratio threshold as a trigger condition.

[0081] The range of hysteresis is determined based on the common-mode voltage suppression effect of each carrier mode modulation scheme across the full modulation ratio range, i.e., the target modulation ratio range in which the common-mode voltage can be suppressed to less than the desired common-mode voltage across the full modulation ratio range, so as to achieve stable switching of carrier mode modulation scheme.

[0082] As a preferred embodiment, hysteresis selection is performed based on the target modulation ratio range of each carrier mode modulation scheme, including:

[0083] The maximum and minimum modulation ratios of the hysteresis loop are determined based on the target modulation ratio range of each carrier mode modulation scheme.

[0084] When performing hysteresis selection, the maximum and minimum modulation ratio values ​​of the hysteresis are determined based on the target modulation ratio range of each carrier mode modulation scheme. By determining the maximum and minimum modulation ratio values ​​of the hysteresis, a buffer space is provided for the switching of carrier mode modulation schemes.

[0085] If the minimum value of the target modulation ratio range of the carrier-reverse stacked SPWM modulation method is less than the maximum value of the target modulation ratio range of the carrier-phase-shift stacked SPWM modulation method, that is, there is an overlap between the target modulation ratio ranges of the carrier-reverse stacked SPWM modulation method and the carrier-phase-shift stacked SPWM modulation method, then this overlap can be set as a hysteresis. In other words, the minimum value of the target modulation ratio range of the carrier-reverse stacked SPWM modulation method is the minimum value of the hysteresis modulation ratio, and the maximum value of the target modulation ratio range of the carrier-phase-shift stacked SPWM modulation method is the maximum value of the hysteresis modulation ratio.

[0086] Based on this, by performing hysteresis selection, the stable switching of carrier mode modulation can be guaranteed, thereby ensuring stable control of the three-level topology.

[0087] Please refer to Figure 11 , Figure 11 This is a schematic diagram of hysteresis selection provided by the present invention. In the diagram, m0 represents the minimum modulation ratio, and m1 represents the maximum modulation ratio.

[0088] As a preferred embodiment, the triggering conditions for switching between various carrier mode modulation schemes are determined based on hysteresis, including:

[0089] Based on the target modulation ratio range of each carrier mode modulation scheme, the switching conditions between each carrier mode modulation scheme are set as follows: when the modulation ratio increases from the minimum modulation ratio value less than the hysteresis to the maximum modulation ratio value, or when the modulation ratio decreases from the maximum modulation ratio value greater than the hysteresis to the minimum modulation ratio value.

[0090] When determining the triggering condition, considering that the hysteresis selected in this application is the overlapping part of the modulation ratio between carrier mode modulation methods with better common-mode voltage suppression effect, specifically, for example, the target modulation ratio range of the carrier inverse stacked SPWM modulation method is 0.7 to 1, and the target modulation ratio range of the carrier phase-shift stacked SPWM modulation method is 0 to 0.8. If the modulation ratio of 0.75 is directly selected as the triggering condition, that is, the carrier mode modulation method is switched when the current modulation ratio is 0.75, it will cause repeated jumps in the carrier mode modulation method. In this embodiment, the maximum value of the modulation ratio of the hysteresis can be set to 0.8, and the minimum value of the modulation ratio can be set to 0.7. If the current modulation ratio decreases from a modulation ratio greater than 0.8 to 0.7, the modulation ratio is switched from the carrier inverse stacked SPWM modulation method to the carrier phase-shift stacked SPWM modulation method. If the current modulation ratio increases from a modulation ratio less than 0.7 to 0.8, the modulation ratio is switched from the carrier phase-shift stacked SPWM modulation method to the carrier inverse stacked SPWM modulation method.

[0091] Based on this, it is ensured that the common-mode suppression effect of each carrier mode modulation method is good within the modulation ratio range of the hysteresis range, and the stability before and after the modulation method switching is guaranteed.

[0092] As a preferred embodiment, before switching the current carrier mode modulation scheme to the target carrier mode modulation scheme, and controlling the three-level topology based on the drive waveform obtained by modulating the carrier of the target carrier mode modulation scheme using the target modulation wave, the method further includes:

[0093] The initial modulated wave is generated based on the modulation ratio and the modulation method of each carrier module;

[0094] The target modulation wave is obtained based on the initial modulation wave.

[0095] In this embodiment, before determining the triggering condition, the initial modulation wave needs to be determined according to the modulation ratio. Specifically, the initial tuning wave is determined according to the amplitude of the carrier and the modulation ratio. The initial modulation wave is a sine wave. The target modulation wave is obtained based on the initial modulation wave so that the carrier can be modulated using the target modulation wave under different modulation ratios, thereby realizing the modulation control of the three-level topology.

[0096] Of course, the modulation ratio can be a user-defined value or a modulation ratio calculated according to a predetermined algorithm; this application does not limit this.

[0097] It should be noted that the per-unit value of the initial modulation ratio without the superposition of zero-sequence voltage and three-phase harmonics can be [-1, 1], while after the injection of zero-sequence voltage and third harmonics, the per-unit value of the initial modulation ratio becomes [-1.1547, 1.1547].

[0098] As a preferred embodiment, obtaining the target modulated wave based on the initial modulated wave includes:

[0099] Determine the zero-sequence voltage and third harmonic for midpoint voltage balance control of a three-level topology;

[0100] The instantaneous value of the target modulation wave is determined based on the initial modulation wave, zero-sequence voltage, and third harmonic, in order to identify the target modulation wave.

[0101] Before performing modulation control, it is necessary to determine the target modulation wave. The target modulation wave can be an existing modulation wave or a target modulation wave generated based on the initial modulation wave, zero-sequence voltage, and third harmonic. Specifically, after determining the initial modulation wave in the form of a sine wave, the instantaneous values ​​of the target modulation wave are determined based on the zero-sequence voltage and third harmonic required for midpoint voltage balance control, as well as the initial modulation wave.

[0102] Specifically, the instantaneous values ​​of the three-phase target modulation wave are denoted as mA, mB, and mC, ua, ub, and uc are the three-phase instantaneous values ​​of the initial modulation wave, vo1 is the third harmonic, vo2 is the zero-sequence voltage, and the instantaneous value of the target modulation wave can be determined by the following formula:

[0103]

[0104] The third harmonic can be determined by the following formula:

[0105]

[0106] Based on this, the target modulation wave is discretized to modulate different carriers. Different carriers can refer to carrier inversion stacked waveforms or carrier phase shift stacked waveforms.

[0107] Please refer to Figure 12 , Figure 12 This is a schematic diagram of a target modulation wave and a driving waveform provided by the present invention. It can be seen that after adding zero-sequence voltage and three-phase harmonics, the target modulation wave is a saddle wave.

[0108] As a preferred embodiment, the current carrier mode modulation method is switched to the target carrier mode modulation method, and the three-level topology is controlled based on the drive waveform obtained by modulating the carrier of the target carrier mode modulation method according to the target modulation wave, including:

[0109] Switch the current carrier mode modulation scheme to the target carrier mode modulation scheme, and modulate the carrier of the target carrier mode modulation scheme based on the instantaneous value;

[0110] Determine the duty cycle values ​​of each phase after the carrier is modulated;

[0111] The driving waveform is generated based on the duty cycle value of each phase;

[0112] Control of the three-level topology based on the driving waveform.

[0113] By determining the instantaneous value of the target modulation wave, when modulating the carrier, the instantaneous value of the target modulation wave at the moment of carrier mode modulation switching is obtained, and modulation of a new carrier cycle begins from the switching moment. After carrier modulation, the duty cycle value of each phase can be determined, and the driving waveform, i.e., the three-phase driving waveform, can be determined based on the duty cycle value of each phase, thereby controlling the three-level topology and realizing modulation control.

[0114] Specifically, the duty cycles of each phase can be set to T1, T2 and T3 respectively, and the corresponding PWM drive waveform can be determined according to T1, T2 and T3.

[0115] The transition from carrier-reverse stacked SPWM modulation to carrier-phase-shift stacked SPWM modulation requires latching the three-phase modulation wave at the transition point, i.e., at the initial moment of carrier counting, and simultaneously modulating it with three sets of carrier-phase-shift stacked waveforms that are 120° apart; the transition from carrier-phase-shift stacked SPWM modulation to carrier-reverse stacked SPWM modulation requires latching the three-phase modulation wave at the transition point, i.e., at the initial moment of carrier counting, and simultaneously modulating it with three sets of identical carrier-phase-in-phase stacked waveforms.

[0116] Please refer to Figure 13 , Figure 13 This is a schematic diagram of a three-level topology modulation control system provided by the present invention. The system includes:

[0117] The determining unit 131 is used to determine the triggering conditions for switching between each carrier mode modulation method based on the modulation ratio range in which the common mode voltage of each carrier mode modulation method is less than the expected common mode voltage in the full modulation ratio range.

[0118] The judgment unit 132 is used to determine whether the triggering condition for switching from the current carrier mode modulation mode to the target carrier mode modulation mode is met based on the current modulation ratio;

[0119] The control unit 133 is used to switch the current carrier mode modulation mode to the target carrier mode modulation mode when the triggering condition is met, and to control the three-level topology based on the drive waveform after modulating the carrier of the target carrier mode modulation mode according to the target modulation wave.

[0120] For an introduction to the three-level topology modulation control system provided by the present invention, please refer to the above method embodiments; the present invention will not be described again here.

[0121] Please refer to Figure 14 , Figure 14 This is a schematic diagram of a three-level topology modulation control device provided by the present invention. The device includes:

[0122] Memory 141 is used to store computer programs;

[0123] The processor 142 is used to implement the steps of the three-level topology modulation control method described above when executing a computer program.

[0124] For a description of the three-level topology modulation control device provided by the present invention, please refer to the above method embodiments; the present invention will not be described again here.

[0125] The computer-readable storage medium of the present invention stores a computer program, which, when executed by a processor, implements the steps of the three-level topology modulation control method described above.

[0126] For a description of the computer-readable storage medium provided by the present invention, please refer to the above method embodiments; the present invention will not be described again here.

[0127] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0128] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A three-level topology modulation control method, characterized in that, include: The triggering conditions for switching between the various carrier mode modulation schemes are determined based on the modulation ratio range in which the common-mode voltage is less than the desired common-mode voltage across the full modulation ratio range for each carrier mode modulation scheme. An initial modulated wave is generated based on the modulation ratio and the modulation scheme of each of the aforementioned carrier modes; The target modulation wave is obtained based on the initial modulation wave; Based on the current modulation ratio, determine whether the triggering condition for switching from the current carrier mode modulation scheme to the target carrier mode modulation scheme is met; If satisfied, the current carrier mode modulation method is switched to the target carrier mode modulation method, and the three-level topology is controlled based on the driving waveform after modulating the carrier of the target carrier mode modulation method according to the target modulation wave. The triggering conditions for switching between each carrier mode modulation scheme are determined based on the modulation ratio range where the common-mode voltage is less than the desired common-mode voltage across the entire modulation ratio range for each carrier mode modulation scheme, including: Determine the common-mode voltage of each of the carrier mode modulation schemes within the full modulation ratio range; Determine the target modulation ratio range in which the common-mode voltage of each of the carrier mode modulation schemes is less than the desired common-mode voltage; Hysteresis selection is performed based on the target modulation ratio range of each of the aforementioned carrier mode modulation schemes; The triggering conditions for switching between the various carrier mode modulation schemes are determined based on the hysteresis.

2. The three-level topology modulation control method as described in claim 1, characterized in that, Hysteresis selection based on the target modulation ratio range of each of the aforementioned carrier mode modulation schemes includes: The maximum and minimum modulation ratio values ​​of the hysteresis loop are determined based on the target modulation ratio range of each of the carrier modes.

3. The three-level topology modulation control method as described in claim 2, characterized in that, The triggering conditions for switching between each of the carrier mode modulation schemes are determined based on the hysteresis, including: Based on the target modulation ratio range of each of the carrier mode modulation schemes, the switching conditions between each of the carrier mode modulation schemes are set as follows: when the modulation ratio increases from the minimum modulation ratio value less than the hysteresis to the maximum modulation ratio value, or when the modulation ratio decreases from the maximum modulation ratio value greater than the hysteresis to the minimum modulation ratio value.

4. The three-level topology modulation control method as described in claim 1, characterized in that, Obtaining the target modulation wave based on the initial modulation wave includes: Determine the zero-sequence voltage and third harmonic for midpoint voltage balance control of the three-level topology; The instantaneous value of the target modulation wave is determined based on the initial modulation wave, the zero-sequence voltage, and the third harmonic, thereby determining the target modulation wave.

5. The three-level topology modulation control method as described in claim 4, characterized in that, Switching the current carrier mode modulation scheme to the target carrier mode modulation scheme, and controlling the three-level topology based on the target modulation wave and the resulting drive waveform after modulating the carrier of the target carrier mode modulation scheme, including: The current carrier mode modulation scheme is switched to the target carrier mode modulation scheme, and the carrier of the target carrier mode modulation scheme is modulated based on the instantaneous value; Determine the duty cycle values ​​of each phase after the carrier is modulated; The driving waveform is generated based on the duty cycle value of each phase; The three-level topology is controlled based on the driving waveform.

6. A three-level topology modulation control system, characterized in that, include: The determining unit is used to determine the triggering conditions for switching between the various carrier mode modulation methods based on the modulation ratio range in which the common-mode voltage of each carrier mode modulation method is less than the desired common-mode voltage across the full modulation ratio range. The judgment unit is used to determine, based on the current modulation ratio, whether the triggering condition for switching from the current carrier mode modulation scheme to the target carrier mode modulation scheme is met; The control unit is used to switch the current carrier mode modulation mode to the target carrier mode modulation mode when the triggering condition is met, and to control the three-level topology based on the driving waveform after modulating the carrier of the target carrier mode modulation mode with the target modulation wave. Also includes: An initial modulated wave is generated based on the modulation ratio and the modulation scheme of each of the aforementioned carrier modes; The target modulation wave is obtained based on the initial modulation wave; The specific unit is used for: Determine the common-mode voltage of each of the carrier mode modulation schemes within the full modulation ratio range; Determine the target modulation ratio range in which the common-mode voltage of each of the carrier mode modulation schemes is less than the desired common-mode voltage; Hysteresis selection is performed based on the target modulation ratio range of each of the aforementioned carrier mode modulation schemes; The triggering conditions for switching between the various carrier mode modulation schemes are determined based on the hysteresis.

7. A three-level topology modulation control device, characterized in that, include: Memory, used to store computer programs; A processor, configured to implement the steps of the three-level topology modulation control method as described in any one of claims 1 to 5 when executing the computer program.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the three-level topology modulation control method as described in any one of claims 1 to 5.

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