Hybrid pulse width modulation method, apparatus, device and program product

Abstract

The embodiment of the invention provides a hybrid pulse width modulation method and device, equipment and a program product. The method is applied to a controller in a three-phase voltage source converter, and comprises the following steps: acquiring a first duty ratio in a continuous pulse width modulation mode and a second duty ratio in a discontinuous pulse width modulation mode, and obtaining a power grid period count value corresponding to a current pulse width modulation period according to the first duty ratio and the second duty ratio; obtaining a mixed pulse width modulation switching count value, and screening from the first duty ratio and the second duty ratio according to the power grid period count value and the mixed pulse width modulation switching count value to obtain a target duty ratio; and according to the target duty ratio, generating a corresponding pulse width modulation signal so as to control a full-control power device in the power converter in the current pulse width modulation period. The method is used for prolonging the service life of components of the three-phase voltage source converter and improving the operation stability.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a hybrid pulse width modulation method, device, equipment and program product. Background Art

[0002] As a power electronic device, the three-phase voltage source converter is used to achieve efficient conversion and control of electric energy. It can convert DC to AC, or AC to DC, and is widely used in power systems. The controller of the three-phase voltage source converter uses pulse width modulation (PWM) to achieve precise control of the fully controlled power devices in the power converter to meet different power requirements or adapt to different load conditions.

[0003] Traditional pulse width modulation methods include continuous and discontinuous. In the continuous pulse width modulation method, the fully controlled power device needs to be turned on and off once in each control cycle. This frequent switching operation will cause large switching losses and device temperature rise, affecting its performance and service life. In the discontinuous pulse width modulation method, by adjusting the duty cycle, the power switching device remains in a fixed state within a specific time period, thereby reducing the number of switches and reducing switching losses. However, this method will cause the DC side voltage fluctuation to increase and the DC capacitor temperature to increase, thereby reducing the component life and stable operation of the three-phase voltage source converter. Summary of the invention

[0004] The embodiments of the present application provide a hybrid pulse width modulation method, device, equipment and program product to improve the component life and operation stability of a three-phase voltage source converter.

[0005] In a first aspect, an embodiment of the present application provides a hybrid pulse width modulation method, which is applied to a controller in a three-phase voltage source converter, comprising:

[0006] Obtaining a first duty cycle in a continuous pulse width modulation mode and a second duty cycle in a discontinuous pulse width modulation mode, and obtaining a grid cycle count value corresponding to a current pulse width modulation cycle according to the first duty cycle and the second duty cycle;

[0007] Obtaining a hybrid pulse width modulation switching count value, and filtering from the first duty cycle and the second duty cycle according to the grid cycle count value and the hybrid pulse width modulation switching count value to obtain a target duty cycle of the current pulse width modulation cycle;

[0008] According to the target duty cycle, a corresponding pulse width modulation signal is generated to control the fully controlled power device in the power converter in the current pulse width modulation cycle; wherein the three-phase voltage source converter includes a power converter.

[0009] In a possible implementation manner, obtaining a grid cycle count value corresponding to a current pulse width modulation cycle according to the first duty cycle and the second duty cycle includes:

[0010] According to the first duty cycle, a corresponding first zero-sequence duty cycle is obtained;

[0011] According to the second duty cycle, a corresponding second zero-sequence duty cycle is obtained;

[0012] Calculating the first zero-sequence duty cycle and the second zero-sequence duty cycle to obtain a zero-sequence duty cycle difference of a current pulse width modulation period;

[0013] According to the zero-sequence duty cycle difference, the grid cycle count value corresponding to the current pulse width modulation cycle is obtained.

[0014] In a possible implementation manner, obtaining a grid cycle count value corresponding to a current pulse width modulation cycle according to the zero-sequence duty cycle difference includes:

[0015] Determine whether the preset duty cycle difference threshold is greater than the zero-sequence duty cycle difference corresponding to the current pulse width modulation cycle and less than the zero-sequence duty cycle difference corresponding to the previous pulse width modulation cycle. If so, increase the grid cycle count value corresponding to the current pulse width modulation cycle by the preset value; wherein the zero-sequence duty cycle difference and the grid cycle count value are both initially set to 0;

[0016] If not, the grid cycle count value corresponding to the current pulse width modulation cycle is maintained;

[0017] Obtain a preset hybrid pulse width modulation cycle count value, analyze the grid cycle count value and the preset hybrid pulse width modulation cycle count value, and obtain the grid cycle count value corresponding to the current pulse width modulation cycle; wherein the preset hybrid pulse width modulation cycle count value is used to indicate the total number of cycles of the discontinuous pulse width modulation mode and the continuous pulse width modulation mode in the hybrid pulse width modulation method.

[0018] In a possible implementation, analyzing the grid cycle count value and the preset hybrid pulse width modulation cycle count value to obtain the grid cycle count value corresponding to the current pulse width modulation cycle includes:

[0019] Determine whether the power grid cycle count value is greater than or equal to a preset hybrid pulse width modulation cycle count value, and if so, set the power grid cycle count value to 0, wherein the preset hybrid pulse width modulation cycle count value refers to the total number of cycles of the continuous pulse width modulation mode and the discontinuous pulse width modulation mode;

[0020] If not, the grid cycle count value corresponding to the current pulse width modulation cycle is maintained.

[0021] In a possible implementation, a hybrid pulse width modulation switching count value is obtained, and a first duty cycle and a second duty cycle are screened according to a grid cycle count value and a hybrid pulse width modulation switching count value to obtain a target duty cycle of a current pulse width modulation cycle, including:

[0022] According to a preset discontinuous pulse width modulation mode proportion threshold and a preset mixed pulse width modulation cycle count value, a mixed pulse width modulation switching count value is obtained; wherein the preset discontinuous pulse width modulation mode proportion threshold is used to indicate the proportion of the discontinuous pulse width modulation mode in the mixed pulse width modulation method;

[0023] If the grid cycle count value is less than or equal to the hybrid pulse width modulation switching count value, then selecting the second duty cycle as the target duty cycle of the current pulse width modulation cycle;

[0024] If the grid cycle count value is greater than the hybrid pulse width modulation switching count value, the first duty cycle is selected as the target duty cycle of the current pulse width modulation cycle.

[0025] In a possible implementation, obtaining a first duty cycle in a continuous pulse width modulation mode and a second duty cycle in a discontinuous pulse width modulation mode includes:

[0026] Obtaining a DC voltage on the DC side of a power converter in a three-phase voltage source converter and a three-phase output voltage reference value on the AC side corresponding to a current pulse width modulation cycle;

[0027] The DC voltage and the three-phase output voltage reference value are calculated to obtain a first duty cycle in a continuous pulse width modulation mode and a second duty cycle in a discontinuous pulse width modulation mode.

[0028] In a second aspect, an embodiment of the present application provides a hybrid pulse width modulation device, comprising:

[0029] A first processing module is used to obtain a first duty cycle in a continuous pulse width modulation mode and a second duty cycle in a discontinuous pulse width modulation mode, and obtain a power grid cycle count value corresponding to a current pulse width modulation cycle according to the first duty cycle and the second duty cycle;

[0030] The second processing module is used to obtain the hybrid pulse width modulation switching count value, and select from the first duty cycle and the second duty cycle according to the power grid cycle count value and the hybrid pulse width modulation switching count value to obtain the target duty cycle of the current pulse width modulation cycle;

[0031] A generating module is used to generate a corresponding pulse width modulation signal according to a target duty cycle to control a fully controlled power device in a power converter in a current pulse width modulation cycle; wherein the three-phase voltage source converter includes a power converter.

[0032] In a possible implementation manner, the first processing module is further configured to:

[0033] According to the first duty cycle, a corresponding first zero-sequence duty cycle is obtained;

[0034] According to the second duty cycle, a corresponding second zero-sequence duty cycle is obtained;

[0035] Calculating the first zero-sequence duty cycle and the second zero-sequence duty cycle to obtain a zero-sequence duty cycle difference of a current pulse width modulation period;

[0036] According to the zero-sequence duty cycle difference, the grid cycle count value corresponding to the current pulse width modulation cycle is obtained.

[0037] In a possible implementation manner, the first processing module is further configured to:

[0038] Determine whether the preset duty cycle difference threshold is greater than the zero-sequence duty cycle difference corresponding to the current pulse width modulation cycle and less than the zero-sequence duty cycle difference corresponding to the previous pulse width modulation cycle. If so, increase the grid cycle count value corresponding to the current pulse width modulation cycle by the preset value; wherein the zero-sequence duty cycle difference and the grid cycle count value are both initially set to 0;

[0039] If not, the grid cycle count value corresponding to the current pulse width modulation cycle is maintained;

[0040] Obtain a preset hybrid pulse width modulation cycle count value, analyze the grid cycle count value and the preset hybrid pulse width modulation cycle count value, and obtain the grid cycle count value corresponding to the current pulse width modulation cycle; wherein the preset hybrid pulse width modulation cycle count value is used to indicate the total number of cycles of the discontinuous pulse width modulation mode and the continuous pulse width modulation mode in the hybrid pulse width modulation method.

[0041] In a possible implementation manner, the first processing module is further configured to:

[0042] Determine whether the power grid cycle count value is greater than or equal to a preset hybrid pulse width modulation cycle count value, and if so, set the power grid cycle count value to 0, wherein the preset hybrid pulse width modulation cycle count value refers to the total number of cycles of the continuous pulse width modulation mode and the discontinuous pulse width modulation mode;

[0043] If not, the grid cycle count value corresponding to the current pulse width modulation cycle is maintained.

[0044] In a possible implementation manner, the second processing module is further used for:

[0045] According to a preset discontinuous pulse width modulation mode proportion threshold and a preset mixed pulse width modulation cycle count value, a mixed pulse width modulation switching count value is obtained; wherein the preset discontinuous pulse width modulation mode proportion threshold is used to indicate the proportion of the discontinuous pulse width modulation mode in the mixed pulse width modulation method;

[0046] If the grid cycle count value is less than or equal to the hybrid pulse width modulation switching count value, then selecting the second duty cycle as the target duty cycle of the current pulse width modulation cycle;

[0047] If the grid cycle count value is greater than the hybrid pulse width modulation switching count value, the first duty cycle is selected as the target duty cycle of the current pulse width modulation cycle.

[0048] In a possible implementation manner, the first processing module is further configured to:

[0049] Obtaining a DC voltage on the DC side of a power converter in a three-phase voltage source converter and a three-phase output voltage reference value on the AC side corresponding to a current pulse width modulation cycle;

[0050] The DC voltage and the three-phase output voltage reference value are calculated to obtain a first duty cycle in a continuous pulse width modulation mode and a second duty cycle in a discontinuous pulse width modulation mode.

[0051] In a third aspect, an embodiment of the present application provides a three-phase voltage source converter, including: a DC interface, a DC capacitor, a power converter, an AC filter, an AC interface, and a controller;

[0052] The power converter supports a variety of topologies, including three-phase two-level power conversion unit and three-phase multi-level power conversion unit;

[0053] AC filter, which is any one of L-type, LC-type and LCL-type filters;

[0054] The controller includes a memory and a processor, the memory storing computer-executable instructions;

[0055] The processor executes the computer-executable instructions stored in the memory, so that the processor executes the above first aspect and / or various possible implementations of the first aspect.

[0056] In a fourth aspect, an embodiment of the present application provides a hybrid pulse width modulation device, including: a memory, a processor;

[0057] The memory stores computer-executable instructions;

[0058] The processor executes the computer-executable instructions stored in the memory, so that the processor executes the above first aspect and / or various possible implementations of the first aspect.

[0059] In a fifth aspect, an embodiment of the present application provides a computer program product, including a computer program, which, when executed by a processor, implements the above first aspect and / or various possible implementation methods of the first aspect.

[0060] The hybrid pulse width modulation method, device, equipment and program product provided in the embodiments of the present application calculate the first duty cycle and the second duty cycle to obtain a grid cycle count value corresponding to the current pulse width modulation cycle; obtain a hybrid pulse width modulation switching count value, and select a continuous pulse width modulation mode and a discontinuous pulse width modulation mode by analyzing the grid cycle count value and the hybrid pulse width modulation switching count value to achieve alternating use of the two modes. Compared with the traditional single mode, the DC capacitor temperature of the three-phase voltage source converter is reduced and the component life is increased, thereby promoting the stable operation of the three-phase voltage source converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0062] Figure 1 A flow chart of a hybrid pulse width modulation method provided in an embodiment of the present application Figure 1 ;

[0063] Figure 2 A schematic diagram of the structure of a three-phase two-level power conversion unit provided in an embodiment of the present application;

[0064] Figure 3 A schematic diagram of the structure of a mid-point clamped three-level power conversion unit provided in an embodiment of the present application;

[0065] Figure 4 A schematic diagram of a duty cycle signal of a continuous pulse width modulation method provided in an embodiment of the present application;

[0066] Figure 5 A flow chart of a hybrid pulse width modulation method provided in an embodiment of the present application Figure 2 ;

[0067] Figure 6 A flow chart of a hybrid pulse width modulation method provided in an embodiment of the present application Figure 3 ;

[0068] Figure 7 A schematic diagram of the structure of a hybrid pulse width modulation device provided in the present application;

[0069] Figure 8 A schematic diagram of the structure of a three-phase voltage source converter provided in an embodiment of the present application;

[0070] Fig. 9 A schematic diagram of the structure of a hybrid pulse width modulation device provided in this application.

[0071] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0072] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0073] Three-phase voltage source converters play an important role in various application scenarios such as power systems. The controller in the three-phase voltage source converter uses pulse width modulation to achieve precise control of the fully controlled power devices in the power converter. Under the action of the pulse width modulation signal, the fully controlled power device will be turned on and off according to the requirements of the signal, thereby controlling the average voltage on the AC side. For example, when the pulse of the pulse width modulation signal is at a high level, the fully controlled power device may be triggered to turn on, and current can flow through the device; when the pulse is at a low level, the device is turned off and the current path is cut off. This periodic opening and closing action will affect the output of the power converter. Because the fully controlled power device constantly changes the on and off state, the voltage waveform on the AC side of the three-phase voltage source converter is effectively modulated.

[0074] Specifically, the average voltage on the AC side is controlled by precisely controlling the time ratio (i.e., pulse width) of the fully controlled power device being turned on and off. If the pulse width is wide, then in one cycle, the power electronic device is turned on for a relatively long time, and the average voltage obtained on the AC side will be higher; conversely, if the pulse width is narrow and the on time is short, the average voltage on the AC side will be lower. In this way, the controller of the three-phase voltage source converter uses pulse width modulation technology to achieve effective control of the average voltage on the AC side to meet different power requirements or adapt to different load conditions.

[0075] Traditional pulse width modulation methods include continuous pulse width modulation and discontinuous pulse width modulation. In continuous pulse width modulation, the fully controlled power device needs to be turned on and off once in one control cycle. Since one turn-on and one turn-off are required in one control cycle, this frequent state transition causes large switching losses in the fully controlled power device. If the switching frequency is high, the temperature of the fully controlled power device will increase. Excessive temperature will affect the performance of the device, such as reducing its efficiency, shortening its service life, and may even cause device damage.

[0076] In the discontinuous pulse width modulation method, the duty cycle of the three-phase pulse width modulation is adjusted to control the power switch device to remain in a fixed state within a specific time period, thereby avoiding frequent switching operations within this time period. Compared with the continuous pulse width modulation method, the number of switches is reduced, thereby reducing the switching loss of the fully controlled power device. However, in this method, since the three-phase AC side and the DC side are interrelated in the converter, when the duty cycle of the three-phase pulse width modulation changes, there are technical problems such as the fluctuation of the DC side voltage becomes larger and the temperature of the DC capacitor increases, thereby reducing the component life and stable operation of the three-phase voltage source converter.

[0077] The present application provides a hybrid pulse width modulation method, which monitors and obtains the first duty cycle in the continuous pulse width modulation mode and the second duty cycle in the discontinuous pulse width modulation mode, and obtains the grid cycle count value corresponding to the current pulse width modulation cycle according to the first duty cycle and the second duty cycle obtained; obtains the hybrid pulse width modulation switching count value, and selects the appropriate duty cycle from the first duty cycle and the second duty cycle by comparing the relationship between the grid cycle count value and the hybrid pulse width modulation switching count value, and generates a corresponding pulse width modulation signal according to the determined target duty cycle to control the fully controlled power device in the power converter of the current pulse width modulation cycle. By reasonably switching between the continuous pulse width modulation mode and the discontinuous pulse width modulation mode, the technical problems of increased temperature and reduced life of DC capacitors in three-phase voltage source converters can be solved.

[0078] The technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0079] Figure 1 A flow chart of a hybrid pulse width modulation method provided in an embodiment of the present application Figure 1 ,like Figure 1 As shown, the method includes:

[0080] S101, obtaining a first duty cycle in a continuous pulse width modulation mode and a second duty cycle in a discontinuous pulse width modulation mode, and obtaining a grid cycle count value corresponding to a current pulse width modulation cycle according to the first duty cycle and the second duty cycle.

[0081] In this embodiment, pulse width modulation is a technology that controls the output of a circuit by adjusting the width of a pulse signal. Pulse width modulation includes continuous pulse width modulation (CPWM) and discontinuous pulse width modulation (DPWM), wherein continuous pulse width modulation is a method of controlling the output signal by continuously adjusting the pulse width. In continuous pulse width modulation, the fully controlled power device performs switching actions according to a certain rule in each switching cycle. Taking a DC-AC inverter as an example, by comparing a fixed-frequency triangular wave (carrier) with a low-frequency sine wave (modulation wave), when the modulation wave is greater than the carrier, the corresponding switch tube is turned on, otherwise it is turned off. Discontinuous pulse width modulation adjusts the output duty cycle of the controller to ensure that the output voltage remains unchanged within a specific time period, so that the fully controlled power device remains in a fixed state (for example, always on or always off), thereby causing the pulse width modulation waveform to be discontinuous.

[0082] Duty cycle is an important parameter in pulse width modulation, which describes the ratio of pulse width to period. Specifically, duty cycle refers to the ratio of the time that the pulse is in a high level state to the entire cycle time in a pulse width modulation cycle. For example, a duty cycle of 50% means that in a pulse width modulation cycle, the high level will occupy half of the entire cycle time. In the continuous pulse width modulation mode, for example, the first duty cycle can be obtained by circuit measurement or control algorithm. The duty cycle acquisition method in the discontinuous pulse width modulation mode is similar to the continuous mode. According to the first duty cycle and the second duty cycle, the grid cycle count value corresponding to the current pulse width modulation cycle is obtained. The grid cycle count value refers to the time required for the grid voltage or current to complete a complete cycle (such as a cycle of a sine wave). The grid cycle count value can be used to adjust the required duty cycle in the pulse width modulation to ensure the stable operation of the three-phase voltage source converter. The grid cycle count value can also be used to determine the switching of different modulation modes (such as continuous pulse width modulation and discontinuous pulse width modulation). This helps to optimize the performance of the three-phase voltage source converter, reduce switching losses, and reduce the temperature of DC capacitors.

[0083] Optionally, the DC voltage on the DC side of the power converter in the three-phase voltage source converter and the three-phase output voltage reference value on the AC side corresponding to the current pulse width modulation period are obtained, and the DC voltage and the three-phase output voltage reference value are calculated to obtain the first duty cycle in the continuous pulse width modulation mode and the second duty cycle in the discontinuous pulse width modulation mode.

[0084] In this embodiment, in each pulse width modulation cycle, a voltage sensor (such as a Hall effect sensor or a resistor divider) in the three-phase voltage source converter can be used to obtain the DC voltage U on the DC side of the power converter. dc At the same time, in each pulse width modulation cycle, the controller calls the mixed pulse width modulation duty cycle calculation program once, and calls the interrupt program through hardware interrupts when the hardware pulse width modulation counter count value is zero or the count value reaches the maximum value, and calculates the three-phase (phase A, phase B, phase C) output voltage reference value U A , U B with U C .

[0085] Optionally, the power converter supports multiple topologies, which can be any one of a three-phase two-level power conversion unit and a three-phase multi-level power conversion unit. For example, when the topology of the power converter is a three-phase two-level power conversion unit, the corresponding circuit diagram is as follows: Figure 2As shown, the topological structure of the three-phase two-level power conversion unit includes a capacitor CAP and six groups of fully controlled power devices. Phase A includes two groups of fully controlled power devices T1 and T2; Phase B includes two groups of fully controlled power devices T3 and T4; Phase C includes two groups of fully controlled power devices T5 and T6. In this topological form, the first duty cycle in the continuous pulse width modulation mode is obtained as:

[0086]

[0087] In the formula, p A is the duty cycle of the fully controlled power device T1 / T2, p B is the duty cycle of the fully controlled power device T3 / T4, p C is the duty cycle of the fully controlled power device T5 / T6, U zero is the zero-sequence voltage, that is:

[0088]

[0089] Optionally, when the topology of the power converter is a neutral point clamped three-level (NPC) power conversion unit, the corresponding circuit diagram is as follows: Figure 3 As shown, it should be noted that the midpoint clamped three-level power conversion unit is a specific topological structure in the three-phase multi-level power conversion unit. Three levels are generated by midpoint clamping and DC capacitors. Its topological structure includes two capacitors CAP1 and CAP2 connected in series; the point between the two capacitors is called the midpoint Z; the A phase includes four groups of fully controlled power devices T1_A, T2_A, T3_A and T4_A, and two clamping diodes D1_A and D2_A; the B phase includes four groups of fully controlled power devices T1_B, T2_B, T3_B and T4_B, and two clamping diodes D1_B and D2_B; the C phase includes four groups of fully controlled power devices T1_C, T2_C, T3_C and T4_C, and two clamping diodes D1_C and D2_C. In this topological form, the first duty cycle in the continuous pulse width modulation mode is obtained as follows:

[0090]

[0091]

[0092] In the formula, , , and They are the duty cycles corresponding to phase A, phase B, and phase C, and are the duty cycles of the fully controlled power devices T1_A / T3_A and T4_A / T2_A, respectively. and They are the duty cycles of the fully controlled power devices T1_B / T3_B and T4_B / T2_B, and They are the duty cycles of the fully controlled power devices T1_C / T3_C and T4_C / T2_C respectively. In this circuit, taking the duty cycle of phase A (A_phase) as an example, a fixed-frequency triangle wave (carrier) is compared with a low-frequency sine wave (modulation wave), such as Figure 4 As shown, the pulse width modulation waveforms of the two duty cycles corresponding to phase A (phase A duty cycle 1 and phase A duty cycle 2) are obtained.

[0093] Optionally, the DC voltage and the three-phase output voltage reference value are calculated to obtain the second duty cycle in the discontinuous pulse width modulation mode, including discontinuous pulse width modulation 0 (Discontinuous Pulse Width Modulation 0, DPWM0), discontinuous pulse width modulation 1 (Discontinuous Pulse Width Modulation 1, DPWM1), discontinuous pulse width modulation 2 (Discontinuous Pulse Width Modulation 2, DPWM2) and other methods. Taking DPWM1 as an example, when the topology of the power converter is a three-phase two-level power conversion unit, the second duty cycle in the discontinuous pulse width modulation mode is obtained as follows:

[0094]

[0095] In the formula, p A is the duty cycle of the fully controlled power device T1 / T2, p B is the duty cycle of the fully controlled power device T3 / T4, p C is the duty cycle of the fully controlled power device T5 / T6, U zero is the zero-sequence voltage, that is

[0096]

[0097] In the formula, for , , The maximum value in ; for , , The minimum value in .

[0098] When the topology of the power converter is a neutral point clamped three-level (NPC) power conversion unit, the second duty cycle in the discontinuous pulse width modulation mode is obtained as follows:

[0099]

[0100]

[0101] In the formula, ; for , , The maximum value in ; for , , The minimum value in .

[0102] S202, obtaining a hybrid pulse width modulation switching count value, and filtering from the first duty cycle and the second duty cycle according to the grid cycle count value and the hybrid pulse width modulation switching count value to obtain a target duty cycle of the current pulse width modulation cycle.

[0103] Optionally, a hybrid pulse width modulation switching count value is obtained according to a preset duty ratio threshold of the discontinuous pulse width modulation mode and a preset hybrid pulse width modulation cycle count value; if the grid cycle count value is less than or equal to the hybrid pulse width modulation switching count value, the second duty cycle is selected as the target duty cycle of the current pulse width modulation cycle; if the grid cycle count value is greater than the hybrid pulse width modulation switching count value, the first duty cycle is selected as the target duty cycle of the current pulse width modulation cycle.

[0104] Optionally, when the three-phase voltage source converter is started, the preset ratio threshold of the discontinuous pulse width modulation mode and the preset mixed pulse width modulation cycle count value are both set to fixed initial values. The preset ratio threshold of the discontinuous pulse width modulation mode (P_RATIO) and the preset mixed pulse width modulation cycle count value (P_PERIOD) are calculated to obtain the mixed pulse width modulation switching count value (V_SWITCH):

[0105]

[0106] Hybrid pulse width modulation is usually a modulation method that switches between continuous pulse width modulation and discontinuous pulse width modulation or uses them in combination. The hybrid pulse width modulation switching count value refers to the count value at the switching moment between the continuous pulse width modulation and discontinuous pulse width modulation methods, and this value is a fixed value. Among them, the preset discontinuous pulse width modulation mode ratio threshold is used to indicate the ratio of the discontinuous pulse width modulation mode in the hybrid pulse width modulation method, and its value range is [0~1]. This value can be pre-adjusted according to actual conditions; the preset hybrid pulse width modulation cycle count value refers to the total number of cycles of continuous pulse width modulation and discontinuous pulse width modulation in the hybrid pulse width modulation method. This value is a positive integer and can be pre-adjusted according to actual conditions.

[0107] Specifically, if the grid cycle count value is less than or equal to the hybrid pulse width modulation switching count value, the target duty cycle selects the second duty cycle to control the fully controlled power device. This pulse width modulation method has low switching loss but large grid-connected current harmonics and high DC capacitor temperature; when the grid cycle count value is greater than the hybrid pulse width modulation switching count value, the target duty cycle selects the first duty cycle as the target duty cycle. This pulse width modulation method has high switching loss but small grid-connected current harmonics and low DC capacitor temperature.

[0108] S203 . Generate a corresponding pulse width modulation signal according to the target duty cycle to control the fully controlled power devices in the power converter in the current pulse width modulation cycle.

[0109] Optionally, the controller inputs the obtained target duty cycle into the corresponding register of the pulse width modulation control unit, and the pulse width modulation control unit generates a corresponding pulse width modulation signal according to the duty cycle information in the register. These pulse width modulation signals are applied to the fully controlled power devices in the power converter, thereby controlling the on and off time of these devices and realizing the control of the output (such as voltage, current, etc.) of the power converter.

[0110] Optionally, the pulse width modulation control unit is a module for generating a pulse width modulation signal. This module includes registers, the values ​​of which determine the characteristics of the pulse width modulation signal, such as pulse width, etc. The pulse width modulation control unit can be integrated in the controller or exist independently of the controller.

[0111] A hybrid pulse width modulation method provided in an embodiment of the present application is to obtain a grid cycle count value corresponding to the current pulse width modulation period by calculating the first duty cycle and the second duty cycle obtained; obtain a hybrid pulse width modulation switching count value, and select a suitable duty cycle as the target duty cycle from the first duty cycle and the second duty cycle by comparing the relationship between the grid cycle count value and the hybrid pulse width modulation switching count value, and generate a corresponding pulse width modulation signal according to the determined target duty cycle to control the fully controlled power device in the power converter of the current pulse width modulation period. By reasonably switching between the continuous pulse width modulation mode and the discontinuous pulse width modulation mode, the technical problems of the increase in temperature and the reduction in life of the DC capacitor of the three-phase voltage source converter can be solved.

[0112] Figure 5 A flow chart of a hybrid pulse width modulation method provided in an embodiment of the present application Figure 2 ,like Figure 5 As shown, in this embodiment Figure 1 Based on the embodiment, a possible implementation of the hybrid pulse width modulation method is described in detail, and the method includes:

[0113] S501, acquiring a first duty cycle in a continuous pulse width modulation mode and a second duty cycle in a discontinuous pulse width modulation mode.

[0114] Step S501 is similar to step S101 and will not be described again here.

[0115] S502: obtaining a corresponding first zero-sequence duty cycle according to the first duty cycle, obtaining a corresponding second zero-sequence duty cycle according to the second duty cycle, and calculating the first zero-sequence duty cycle and the second zero-sequence duty cycle to obtain a zero-sequence duty cycle difference of the current pulse width modulation period.

[0116] In this embodiment, taking the topology of the power converter as a three-phase two-level power conversion unit as an example, the first duty cycle , , Calculate and get the corresponding first zero-sequence duty cycle . For the second duty cycle , , Calculate and get the corresponding second zero-sequence duty cycle The first zero-sequence duty cycle and the second zero-sequence duty cycle are calculated to obtain the zero-sequence duty cycle difference of the current pulse width modulation cycle: .

[0117] It should be noted that the zero-sequence duty cycle refers to a control variable generated by a controller during a three-phase pulse width modulation process, which can affect the output characteristics of a power converter.

[0118] S503: Determine whether the preset duty cycle difference threshold is greater than the zero-sequence duty cycle difference corresponding to the current pulse width modulation cycle and less than the zero-sequence duty cycle difference corresponding to the previous pulse width modulation cycle.

[0119] Optionally, the preset duty cycle difference threshold value can be theoretically derived, for example, based on the three-phase duty cycle relationship under the ideal working state of the power converter. For example, under the ideal condition of three-phase balance, the fluctuation range of the three-phase duty cycle can be calculated by circuit theory, and then the ideal fluctuation range of the zero-sequence duty cycle is calculated based on this, so as to determine a theoretical threshold value. It should be noted that the preset duty cycle difference threshold values ​​corresponding to power converters of different topological forms are different. The preset duty cycle difference threshold value can also be determined based on the operating experience data of similar power converters in the past or through experimental tests. Different zero-sequence duty cycle differences mean different system operating states. Determining the power grid cycle count value based on this difference can make the control strategy more adaptive and accurate.

[0120] S504: If yes, increase the grid cycle count value corresponding to the current pulse width modulation cycle by a preset value.

[0121] In this embodiment, when the three-phase voltage source converter is started, the initial values ​​of the zero-sequence duty cycle difference and the grid cycle count value are set to 0, which is a starting reference point. It provides an initial benchmark for subsequent comparison and judgment, which is convenient for calculation and judgment during system startup or initialization. When it is determined that the preset duty cycle difference threshold satisfies the zero-sequence duty cycle difference corresponding to the current pulse width modulation cycle and is less than the zero-sequence duty cycle difference corresponding to the previous pulse width modulation cycle, the grid cycle count value corresponding to the current pulse width modulation cycle is increased by the preset value as required. The preset value is a fixed value pre-set according to system requirements, and the preset value is related to relevant parameters such as the control cycle or the switching frequency of the power converter.

[0122] S505: If not, maintain the grid cycle count value corresponding to the current pulse width modulation cycle.

[0123] In this embodiment, when the preset duty cycle difference threshold is not satisfied, which is greater than the zero-sequence duty cycle difference corresponding to the current pulse width modulation cycle and less than the zero-sequence duty cycle difference corresponding to the previous pulse width modulation cycle, in order to maintain the stability of the three-phase voltage source converter and the continuity of the current state, it is selected to keep the grid cycle count value corresponding to the current pulse width modulation cycle unchanged.

[0124] S506: Obtain a preset hybrid pulse width modulation cycle count value, and determine whether the power grid cycle count value is greater than or equal to the preset hybrid pulse width modulation cycle count value.

[0125] S507: If yes, set the grid cycle count value to 0, wherein the preset hybrid pulse width modulation cycle count value refers to the total number of cycles of the continuous pulse width modulation mode and the discontinuous pulse width modulation mode.

[0126] S508: If not, maintain the grid cycle count value corresponding to the current pulse width modulation cycle.

[0127] Optionally, in step S506-step S508, when the three-phase voltage source converter is started, the preset hybrid pulse width modulation cycle count value is a fixed initial value. The grid cycle count value corresponding to the current pulse width modulation cycle obtained in step S503-step S505 is compared with the preset hybrid pulse width modulation cycle count value. If the grid cycle count value is greater than or equal to the preset hybrid pulse width modulation cycle count value, the grid cycle count value is further set to 0; if the grid cycle count value is less than the preset hybrid pulse width modulation cycle count value, the grid cycle count value corresponding to the current pulse width modulation cycle is maintained.

[0128] S509, obtaining a hybrid pulse width modulation switching count value, and filtering from the first duty cycle and the second duty cycle according to the grid cycle count value and the hybrid pulse width modulation switching count value to obtain a target duty cycle of the current pulse width modulation cycle.

[0129] Step S509 is similar to step S102 and will not be described again here.

[0130] S510 . Generate a corresponding pulse width modulation signal according to the target duty cycle to control a fully controlled power device in the power converter in the current pulse width modulation cycle.

[0131] Step S510 is similar to step S103 and will not be described again here.

[0132] A hybrid pulse width modulation method provided in an embodiment of the present application is helpful to optimize the control strategy of pulse width modulation by comparing the zero-sequence duty cycle difference and the preset duty cycle difference threshold to obtain a power grid cycle count value. When a specific duty cycle difference condition is met, the power grid cycle count value is increased, which helps to switch between the two modes more reasonably according to the actual operating state of the system (such as the changing trend of the duty cycle), thereby improving the performance of the entire system. A hybrid pulse width modulation switching count value is obtained by using a fixed preset discontinuous pulse width modulation mode ratio threshold value to indicate when the two modes are switched, so that the system can switch to the appropriate mode more stably. The power grid cycle count value is compared with the preset hybrid pulse width modulation cycle count value and set accordingly, which can ensure the accuracy of the power grid cycle count value. This method further improves the component life and operation stability of the three-phase voltage source converter.

[0133] Figure 6 A flow chart of a hybrid pulse width modulation method provided in an embodiment of the present application Figure 3 ,like Figure 6 As shown, in this embodiment Figure 5 Based on the embodiment, a possible implementation method of the hybrid pulse width modulation method is described in detail, the method includes: when the three-phase voltage source converter is started, the parameters "discontinuous pulse width modulation mode proportion threshold", "hybrid pulse width modulation cycle count value", and "duty ratio difference threshold value" are set to fixed initial values; the variables "hybrid pulse width modulation switching count value", "grid cycle count value", and "zero sequence duty ratio difference value" are initially set to zero. For each pulse width modulation cycle, the controller calls the hybrid pulse width modulation duty ratio calculation program once, and calls the interrupt program and calculates the three-phase output voltage reference value U when the hardware pulse width modulation counter count value is zero or the count value reaches the maximum value through hardware interrupt. A , U B with U C .

[0134] The hybrid pulse width modulation switching count value is calculated according to the duty threshold of the discontinuous pulse width modulation mode and the hybrid pulse width modulation cycle count value; the DC voltage on the DC side of the power converter in the three-phase voltage source converter is obtained, and the duty cycle and zero-sequence duty cycle required for continuous pulse width modulation, as well as the duty cycle and zero-sequence duty cycle required for discontinuous pulse width modulation are calculated according to the DC voltage and the three-phase output voltage reference value. It should be noted that the topology of the power converter can be a three-phase multi-level power conversion unit.

[0135] The zero-sequence duty cycle of continuous pulse width modulation and the zero-sequence duty cycle of discontinuous pulse width modulation are calculated to obtain the zero-sequence duty cycle difference, and it is judged whether the preset duty cycle difference threshold is greater than the zero-sequence duty cycle difference corresponding to the current pulse width modulation period and less than the zero-sequence duty cycle difference corresponding to the previous pulse width modulation period; if so, the grid cycle count value corresponding to the current pulse width modulation period is increased by the preset value; if not, the grid cycle count value corresponding to the current pulse width modulation period is maintained, and it is judged whether the grid cycle count value at this time is greater than or equal to the preset mixed pulse width modulation period count value; if so, the grid cycle count value is set to 0; if not, the grid cycle count value corresponding to the current pulse width modulation period is maintained.

[0136] Then, the numerical values ​​of the grid cycle count value and the hybrid pulse width modulation switching count value are determined. If the grid cycle count value is less than or equal to the hybrid pulse width modulation switching count value, the duty cycle required for discontinuous pulse width modulation is selected as the target duty cycle of the current pulse width modulation cycle; if the grid cycle count value is greater than the hybrid pulse width modulation switching count value, the duty cycle required for continuous pulse width modulation is selected as the target duty cycle of the current pulse width modulation cycle. The controller inputs the obtained target duty cycle into the corresponding register of the pulse width modulation control unit, and the pulse width modulation control unit generates a corresponding pulse width modulation signal according to the duty cycle information in the register. These pulse width modulation signals are applied to the fully controlled power devices in the power converter, thereby controlling the on and off time of these devices and realizing the control of the output (such as voltage, current, etc.) of the power converter.

[0137] Figure 7 A schematic diagram of the structure of a hybrid pulse width modulation device provided in this application is shown in FIG. Figure 7 As shown, the hybrid pulse width modulation device 700 provided in this embodiment includes:

[0138] The first processing module 701 is used to obtain a first duty cycle in a continuous pulse width modulation mode and a second duty cycle in a discontinuous pulse width modulation mode, and obtain a grid cycle count value corresponding to a current pulse width modulation cycle according to the first duty cycle and the second duty cycle;

[0139] The second processing module 702 is used to obtain a hybrid pulse width modulation switching count value, and filter from the first duty cycle and the second duty cycle according to the grid cycle count value and the hybrid pulse width modulation switching count value to obtain a target duty cycle of the current pulse width modulation cycle;

[0140] The generating module 703 is used to generate a corresponding pulse width modulation signal according to the target duty cycle to control the fully controlled power devices in the power converter in the current pulse width modulation cycle; wherein the three-phase voltage source converter includes a power converter.

[0141] In a possible implementation manner, the first processing module 701 is further configured to:

[0142] According to the first duty cycle, a corresponding first zero-sequence duty cycle is obtained;

[0143] According to the second duty cycle, a corresponding second zero-sequence duty cycle is obtained;

[0144] Calculating the first zero-sequence duty cycle and the second zero-sequence duty cycle to obtain a zero-sequence duty cycle difference of a current pulse width modulation period;

[0145] According to the zero-sequence duty cycle difference, the grid cycle count value corresponding to the current pulse width modulation cycle is obtained.

[0146] In a possible implementation manner, the first processing module 701 is further configured to:

[0147] Determine whether the preset duty cycle difference threshold is greater than the zero-sequence duty cycle difference corresponding to the current pulse width modulation cycle and less than the zero-sequence duty cycle difference corresponding to the previous pulse width modulation cycle. If so, increase the grid cycle count value corresponding to the current pulse width modulation cycle by the preset value; wherein the zero-sequence duty cycle difference and the grid cycle count value are both initially set to 0;

[0148] If not, the grid cycle count value corresponding to the current pulse width modulation cycle is maintained;

[0149] Obtain a preset hybrid pulse width modulation cycle count value, analyze the grid cycle count value and the preset hybrid pulse width modulation cycle count value, and obtain the grid cycle count value corresponding to the current pulse width modulation cycle; wherein the preset hybrid pulse width modulation cycle count value is used to indicate the total number of cycles of the discontinuous pulse width modulation mode and the continuous pulse width modulation mode in the hybrid pulse width modulation method.

[0150] In a possible implementation manner, the first processing module 701 is further configured to:

[0151] Determine whether the power grid cycle count value is greater than or equal to a preset hybrid pulse width modulation cycle count value, and if so, set the power grid cycle count value to 0, wherein the preset hybrid pulse width modulation cycle count value refers to the total number of cycles of the continuous pulse width modulation mode and the discontinuous pulse width modulation mode;

[0152] If not, the grid cycle count value corresponding to the current pulse width modulation cycle is maintained.

[0153] In a possible implementation manner, the second processing module 702 is further configured to:

[0154] According to a preset discontinuous pulse width modulation mode proportion threshold and a preset mixed pulse width modulation cycle count value, a mixed pulse width modulation switching count value is obtained; wherein the preset discontinuous pulse width modulation mode proportion threshold is used to indicate the proportion of the discontinuous pulse width modulation mode in the mixed pulse width modulation method;

[0155] If the grid cycle count value is less than or equal to the hybrid pulse width modulation switching count value, then selecting the second duty cycle as the target duty cycle of the current pulse width modulation cycle;

[0156] If the grid cycle count value is greater than the hybrid pulse width modulation switching count value, the first duty cycle is selected as the target duty cycle of the current pulse width modulation cycle.

[0157] In a possible implementation manner, the first processing module 701 is further configured to:

[0158] Obtaining a DC voltage on the DC side of a power converter in a three-phase voltage source converter and a three-phase output voltage reference value on the AC side corresponding to a current pulse width modulation cycle;

[0159] The DC voltage and the three-phase output voltage reference value are calculated to obtain a first duty cycle in a continuous pulse width modulation mode and a second duty cycle in a discontinuous pulse width modulation mode.

[0160] The hybrid pulse width modulation device provided in this embodiment can execute the method provided in the above method embodiment, and its implementation principle and technical effect are similar, which will not be described in detail in this embodiment.

[0161] Figure 8 A schematic diagram of the structure of a three-phase voltage source converter provided in this application is shown in FIG. Figure 8As shown, the three-phase voltage source converter provided in this embodiment includes a DC interface, a DC capacitor, a power converter, an AC filter, an AC interface and a controller. The DC interface includes a DC positive bus interface and a DC negative bus interface, which are respectively connected to one side of the DC capacitor, and the other side of the DC capacitor is connected to the DC side of the power converter. The three-phase output (A phase, B phase and C phase respectively) of the AC side of the power converter is connected to one side of the AC filter, and the other side of the AC filter is connected to the AC interface. Among them, the power converter supports a variety of topological forms, including a three-phase two-level power conversion unit and a three-phase multi-level power conversion unit; the AC filter can be any one of an inductor filter (L type), an inductor-capacitor filter (LC type) and an inductor-capacitor-inductor (LCL type) filter; the controller includes a memory and a processor, and the memory stores computer execution instructions; the processor executes the computer execution instructions stored in the memory, so that the processor executes the method provided in the above method embodiment.

[0162] Fig. 9 This is a schematic diagram of the structure of a hybrid pulse width modulation device provided in this application. Fig. 9 As shown, the hybrid pulse width modulation device 900 provided in this embodiment includes: at least one processor 901 and a memory 902. Optionally, the device 900 also includes a communication component 903. The processor 901, the memory 902 and the communication component 903 are connected via a bus 904.

[0163] In a specific implementation process, at least one processor 901 executes the computer execution instructions stored in the memory 902, so that at least one processor 901 executes the above method.

[0164] The specific implementation process of the processor 901 can be found in the above method embodiment, and its implementation principle and technical effect are similar, so this embodiment will not be repeated here.

[0165] In the above embodiments, it should be understood that the processor can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), etc. A general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in the invention can be directly implemented as a hardware processor, or can be implemented by a combination of hardware and software modules in the processor.

[0166] The memory may include a high-speed memory (Random Access Memory, RAM), and may also include a non-volatile memory (NVM), such as at least one disk storage.

[0167] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, the bus in the drawings of this application is not limited to only one bus or one type of bus.

[0168] The present application also provides a computer program product, including a computer program, which implements the above method when executed by a processor.

[0169] Those skilled in the art can understand that all or part of the steps of implementing the above-mentioned method embodiments can be completed by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, the steps of the above-mentioned method embodiments are executed; and the aforementioned storage medium includes: ROM, RAM, disk or optical disk and other media that can store program codes.

[0170] It should be noted that the data involved in this application (including but not limited to data used for analysis, stored data, displayed data, etc.) are all data authorized by the user or fully authorized by all parties, and the collection, storage, use, processing, transmission, provision, disclosure and application of the relevant data comply with the relevant laws, regulations and standards of the relevant countries and regions, take necessary confidentiality measures, do not violate public order and good morals, and provide corresponding operation entrances for users to choose to authorize or refuse.

[0171] It should be noted that the terms "first", "second", etc. in the claims, the specification and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the invention described herein, for example, can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, products or devices.

[0172] Finally, it should be noted that those skilled in the art will readily conceive of other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses or adaptations of the present invention, which follow the general principles of the present invention and include common knowledge or customary technical means in the art not disclosed by the present invention, are not limited to the precise structure described above and shown in the drawings, and may be modified and changed in various ways without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A hybrid pulse width modulation method, characterized in that: A controller for a three-phase voltage source converter, comprising: Acquire a first duty cycle in a continuous pulse width modulation mode and a second duty cycle in a discontinuous pulse width modulation mode, and obtain a grid cycle count value corresponding to a current pulse width modulation cycle according to the first duty cycle and the second duty cycle; Acquire a hybrid pulse width modulation switching count value, and select from the first duty cycle and the second duty cycle according to the grid cycle count value and the hybrid pulse width modulation switching count value to obtain a target duty cycle of the current pulse width modulation cycle; According to the target duty cycle, a corresponding pulse width modulation signal is generated to control the fully controlled power devices in the power converter in the current pulse width modulation cycle; wherein the three-phase voltage source converter includes the power converter.

2. The method according to claim 1, characterized in that Obtaining a grid cycle count value corresponding to a current pulse width modulation cycle according to the first duty cycle and the second duty cycle, including: According to the first duty cycle, obtaining a corresponding first zero-sequence duty cycle; According to the second duty cycle, obtaining a corresponding second zero-sequence duty cycle; Calculating the first zero-sequence duty cycle and the second zero-sequence duty cycle to obtain a zero-sequence duty cycle difference of a current pulse width modulation period; According to the zero-sequence duty cycle difference, a grid cycle count value corresponding to the current pulse width modulation cycle is obtained.

3. The method according to claim 2, characterized in that According to the zero-sequence duty cycle difference, a grid cycle count value corresponding to the current pulse width modulation cycle is obtained, including: Determine whether the preset duty cycle difference threshold is greater than the zero-sequence duty cycle difference corresponding to the current pulse width modulation cycle, and less than the zero-sequence duty cycle difference corresponding to the previous pulse width modulation cycle, and if so, increase the grid cycle count value corresponding to the current pulse width modulation cycle by a preset value; wherein the zero-sequence duty cycle difference and the grid cycle count value are both initially set to 0; If not, then maintaining the grid cycle count value corresponding to the current pulse width modulation cycle; Obtain a preset hybrid pulse width modulation cycle count value, analyze the power grid cycle count value and the preset hybrid pulse width modulation cycle count value, and obtain the power grid cycle count value corresponding to the current pulse width modulation cycle; wherein the preset hybrid pulse width modulation cycle count value is used to indicate the total number of cycles of the discontinuous pulse width modulation mode and the continuous pulse width modulation mode in the hybrid pulse width modulation method.

4. The method according to claim 3, characterized in that Analyzing the grid cycle count value and the preset hybrid pulse width modulation cycle count value to obtain the grid cycle count value corresponding to the current pulse width modulation cycle includes: Determine whether the power grid cycle count value is greater than or equal to a preset hybrid pulse width modulation cycle count value, and if so, set the power grid cycle count value to 0, wherein the preset hybrid pulse width modulation cycle count value refers to the total number of cycles of the continuous pulse width modulation mode and the discontinuous pulse width modulation mode; If not, the grid cycle count value corresponding to the current pulse width modulation cycle is maintained.

5. The method according to claim 1, characterized in that Acquiring a hybrid pulse width modulation switching count value, and filtering from the first duty cycle and the second duty cycle according to the grid cycle count value and the hybrid pulse width modulation switching count value to obtain a target duty cycle of the current pulse width modulation cycle, including: According to a preset discontinuous pulse width modulation mode proportion threshold and a preset mixed pulse width modulation cycle count value, the mixed pulse width modulation switching count value is obtained; wherein the preset discontinuous pulse width modulation mode proportion threshold is used to indicate the proportion of the discontinuous pulse width modulation mode in the mixed pulse width modulation method; If the grid cycle count value is less than or equal to the hybrid pulse width modulation switching count value, selecting the second duty cycle as the target duty cycle of the current pulse width modulation cycle; If the grid cycle count value is greater than the hybrid pulse width modulation switching count value, the first duty cycle is selected as the target duty cycle of the current pulse width modulation cycle.

6. The method according to claim 1, characterized in that Obtaining a first duty cycle in a continuous pulse width modulation mode and a second duty cycle in a discontinuous pulse width modulation mode, including: Obtaining a DC voltage on the DC side of a power converter in a three-phase voltage source converter and a three-phase output voltage reference value on the AC side corresponding to a current pulse width modulation cycle; The DC voltage and the three-phase output voltage reference value are calculated to obtain a first duty cycle in the continuous pulse width modulation mode and a second duty cycle in the discontinuous pulse width modulation mode.

7. A hybrid pulse width modulation device, characterized in that: include: A first processing module, used for obtaining a first duty cycle in a continuous pulse width modulation mode and a second duty cycle in a discontinuous pulse width modulation mode, and obtaining a grid cycle count value corresponding to a current pulse width modulation cycle according to the first duty cycle and the second duty cycle; A second processing module is used to obtain a hybrid pulse width modulation switching count value, and filter from the first duty cycle and the second duty cycle according to the grid cycle count value and the hybrid pulse width modulation switching count value to obtain a target duty cycle of the current pulse width modulation cycle; A generating module is used to generate a corresponding pulse width modulation signal according to the target duty cycle to control the fully controlled power device in the power converter in the current pulse width modulation cycle; wherein the three-phase voltage source converter includes the power converter.

8. A three-phase voltage source converter, characterized in that: include: DC interfaces, DC capacitors, power converters, AC filters, AC interfaces and controllers; The power converter supports a variety of topologies, including a three-phase two-level power conversion unit and a three-phase multi-level power conversion unit; The AC filter may be any one of an L-type, LC-type and LCL-type filter; The controller includes a memory and a processor, the memory storing computer-executable instructions; The processor executes the computer-executable instructions stored in the memory, so that the processor performs the method according to any one of claims 1 to 6.

9. A hybrid pulse width modulation device, characterized in that: include: Memory, processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory, so that the processor performs the method according to any one of claims 1 to 6.

10. A computer program product, characterized in that The invention comprises a computer program, which implements the method according to any one of claims 1 to 6 when being executed by a processor.

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