Adjustable carrier mixing modulation method and system

Abstract

The invention relates to the technical field of carrier modulation, and discloses an adjustable carrier mixing modulation method and system, and the method comprises the steps: obtaining a first change rate of a target modulation wave under a first working condition, and carrying out the first division operation of the first change rate; obtaining a first change rate of the target modulation wave under the real-time working condition, and determining a first target carrier frequency according to the first division operation result; and presetting a first constraint, and carrying out carrier frequency mixing modulation based on the first constraint in combination with the first target carrier frequency. According to the invention, the dynamic adjustment of the carrier frequency can be realized, and the optimal carrier frequency is determined according to the change rate of the modulated wave, so that unnecessary switching operation is reduced, switching loss is reduced, and the overall efficiency of the system is improved. Meanwhile, through preset constraint conditions, the system can also ensure the quality of the output waveform, the harmonic content of the three-phase voltage and the three-phase current is controlled within a target range, and the actual application requirement is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of carrier modulation technology, in particular to a kind of adjustable carrier mixing modulation method and system. BACKGROUND

[0002] In recent years, with the wide application of renewable energy and the growth of DC load demand, DC power transmission and distribution technology has developed rapidly due to its excellent power control flexibility, easy access to new energy, and advantages of long-distance power transmission. Currently, the mainstream medium-voltage DC converter usually adopts a topology structure of single-phase modular multilevel inverter connected with diode rectifier bridge through an isolation transformer, and is controlled in combination with modular multilevel modulation technology.

[0003] Due to the advantages of modularity, scalability and low harmonic content exhibited by the modular multilevel converter topology structure, it has promoted its application in wind power, photovoltaic and other new energy gathering and sending occasions. Unlike high-voltage large-capacity modular multilevel DC converters, the modular multilevel DC converter in a medium-voltage DC application scenario usually uses a smaller number of sub-modules. Under this configuration, the number of sub-modules per bridge arm is much lower than the hundreds of sub-modules in high-voltage large-capacity systems. At this time, the traditional nearest level modulation (NLM) method is not applicable, and the carrier phase-shifted modulation (PSC-PWM) becomes a more advantageous modulation scheme as it can achieve a higher equivalent switching frequency at a lower switching frequency, effectively improving the overall performance of the converter. However, the traditional carrier phase-shifted modulation method uses a fixed carrier frequency, which can cause frequent switching operations when the modulation wave variation rate is low, resulting in high switching losses and reducing the overall efficiency of the system. Therefore, how to reduce switching operations while ensuring output waveform quality has become a key issue. SUMMARY

[0004] In view of the above existing problems, the present application is proposed.

[0005] Therefore, the present application provides an adjustable carrier mixing modulation method and system to solve the problem of excessive switching operations and high switching losses caused by the traditional carrier phase-shifted modulation method using a fixed carrier frequency when the modulation wave variation rate is low, low efficiency and unable to guarantee the output waveform quality in medium-voltage DC converters.

[0006] To solve the above technical problems, the present application provides the following technical solutions: In a first aspect, the present application provides an adjustable carrier mixing modulation method, comprising: obtaining a first variation rate of a target modulation wave under a first working condition, and performing a first division operation on the first variation rate; acquire a first variation rate of the target modulation wave under a real-time working condition, and determine a first target carrier frequency according to a result of the first division operation; a first constraint is preset, and carrier frequency mixing modulation is performed based on the first constraint and the first target carrier frequency; the first constraint is designed by a first frequency proportional coefficient and a first frequency parameter; the first constraint designed by the first frequency proportional coefficient and the first frequency parameter comprises: a first frequency parameter is determined, and a first comparison operation is performed on the first variation rate and the first frequency parameter; a first carrier frequency and a second carrier frequency are preset; a specifically selected first target carrier frequency is determined according to a first comparison result; the first carrier frequency and the second carrier frequency are determined by a first frequency proportional coefficient.

[0007] As a preferred scheme of the adjustable carrier frequency mixing modulation method, the first division operation comprises: a first division point is set according to a first variation rate of the target modulation wave under the first working condition; the first variation rate of the target modulation wave under the first working condition is divided according to the first division point; the result of the first division operation corresponds to a plurality of carrier frequencies.

[0008] As a preferred scheme of the adjustable carrier frequency mixing modulation method, the preset first constraint comprises: the first constraint is used to constrain the harmonic content of three-phase voltage and current in a target range; the first constraint is for a plurality of different working conditions.

[0009] As a preferred scheme of the adjustable carrier frequency mixing modulation method, the first constraint designed by the first frequency proportional coefficient and the first frequency parameter further comprises: a first frequency parameter m is determined, and a first comparison operation is performed on the first variation rate k and the first frequency parameter m; a first carrier frequency f n and a second carrier frequency jf n are preset, wherein j is a first frequency proportional coefficient; a specifically selected first target carrier frequency is determined according to a first comparison result, and the first target carrier frequency is selected from the first carrier frequency and the second carrier frequency; the first carrier frequency and the second carrier frequency are determined by the first frequency proportional coefficient; When the first carrier frequency is selected as the first target carrier frequency, the first frequency ratio coefficient is 1; When the second carrier frequency is selected as the first target carrier frequency, the first frequency ratio coefficient is j, and j≠1; When m<k<1, the carrier frequency is set as the rated frequency f n , i.e. the first carrier frequency; When -m<k<m, the carrier frequency is set as jf n , i.e. the second carrier frequency, wherein j is a carrier frequency ratio coefficient; When -1<k<-m, the carrier frequency is restored to the rated frequency f n , i.e. the first carrier frequency.

[0010] As a preferred scheme of the adjustable carrier frequency mixing modulation method, the first frequency ratio coefficient comprises: The first frequency ratio coefficient is adjusted according to the total harmonic distortion value of the target modular multi-level direct current converter output waveform.

[0011] As a preferred scheme of the adjustable carrier frequency mixing modulation method, the first change rate of the target modulation wave under the first working condition comprises: The first change rate of the target modulation wave under the first working condition is obtained by performing first analysis on the derivative or differential signal of the modulation wave.

[0012] As a preferred scheme of the adjustable carrier frequency mixing modulation method, the first working condition is a normal operation working condition of the target modular multi-level direct current converter.

[0013] In a second aspect, the present application provides an adjustable carrier frequency mixing modulation system, comprising: A first operation module is configured to obtain a first change rate of a target modulation wave under a first working condition, and perform a first division operation on the first change rate. A frequency determination module is configured to obtain a first change rate of a target modulation wave under a real-time working condition, and determine a first target carrier frequency according to a result of the first division operation. A modulation module is configured to preset a first constraint, and perform carrier frequency mixing modulation based on the first constraint and the first target carrier frequency; the first constraint comprises: determining a first frequency parameter, performing a first comparison operation on the first change rate and the first frequency parameter, presetting a first carrier frequency and a second carrier frequency, and determining a specific selected first target carrier frequency according to a first comparison result; the first carrier frequency and the second carrier frequency are determined by a first frequency ratio coefficient.

[0014] In a third aspect, the present application provides a computer device comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method as described above when executing the computer program.

[0015] In a fourth aspect, the present application provides a computer readable storage medium, which stores a computer program, and the computer program implements the steps of the method as described above when executed by a processor.

[0016] Compared with the prior art, the present application has the following beneficial effects: the present application provides a tunable carrier mixing modulation method and system, obtains a first change rate of a target modulation wave under a first working condition, and performs a first division operation on the first change rate; obtains a first change rate of a target modulation wave under a real-time working condition, determines a first target carrier frequency according to the result of the first division operation; presets a first constraint, and performs carrier mixing modulation based on the first constraint and the first target carrier frequency. The system can realize dynamic adjustment of the carrier frequency, determine the optimal carrier frequency according to the change rate of the modulation wave, thereby reducing unnecessary switching operations, reducing switching loss, and improving the overall efficiency of the system. At the same time, through the preset constraint condition, the system can also ensure the quality of the output waveform, control the harmonic content of three-phase voltage and current within a target range, and meet the demand of actual application. In addition, the system also has good adaptability and flexibility, and can be adjusted and optimized for different working conditions, further improving its performance in actual application. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0018] Figure 1 A flowchart of a tunable carrier mixing modulation method provided for an embodiment of the present application; Figure 2 A schematic diagram of a tunable carrier mixing modulation method provided for an embodiment of the present application; Figure 3 A tunable carrier mixing modulation output schematic diagram when the modulation wave of a tunable carrier mixing modulation method provided for an embodiment of the present application is a sine wave; Figure 4 A tunable carrier mixing modulation output schematic diagram when the modulation wave of a tunable carrier mixing modulation method provided for an embodiment of the present application is a saddle wave; Figure 5A typical medium voltage direct current converter topology diagram of an adjustable carrier frequency modulation method is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0019] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of protection of the present application.

[0020] Embodiment 1 Reference Figures 1-5 For the first embodiment of the present application, the embodiment provides an adjustable carrier frequency modulation method and system, comprising: In the prior art, there are some problems, such as the traditional carrier phase shift modulation method adopts a fixed carrier frequency, which causes frequent switching operation when the modulation wave change rate is small, thereby causing high switching loss and reducing the overall efficiency of the system.

[0021] The present application provides a method that can effectively solve the above-mentioned problems. Next, how to realize the adjustable carrier frequency modulation method will be described in detail in combination with multiple embodiments; Figure 1 A whole flowchart of an adjustable carrier frequency modulation method is shown, comprising: S101, obtaining a first change rate of a target modulation wave under a first working condition, and performing a first division operation on the first change rate; It should be noted that with the widespread application of renewable energy and the growth of direct current load demand, direct current transmission and distribution technology has developed rapidly due to its excellent power control flexibility, easy access to new energy, and advantages of long-distance power transmission. The mainstream medium voltage direct current converter usually adopts a topology structure of single-phase modular multilevel inverter connected with diode rectifier bridge through an isolation transformer, and is controlled in combination with modular multilevel modulation technology.

[0022] In an optional embodiment, the target modular multilevel direct current converter has various working conditions such as normal operation condition, overload condition or fault condition, etc. Under different working conditions, the first change rate of the target modulation wave may have great differences. Therefore, the embodiment divides different change rate ranges into different intervals by performing a first division operation on the first change rate, so as to determine the appropriate carrier frequency according to the change rate under the real-time working condition subsequently.

[0023] In the embodiment of the present application, the first working condition is the normal operation condition of the target modular multilevel direct current converter.

[0024] In the embodiments of the present application, the first change rate of the target modulation wave under the first working condition comprises: The first change rate of the target modulation wave under the first working condition is obtained by first analyzing the derivative or differential signal of the modulation wave.

[0025] Specifically, the first analysis first calculates the change rate k of the modulation wave in real time.

[0026] The specific expression can be obtained by differentiating the modulation wave: , It should be noted that the k value is divided into several different ranges according to its size, and the appropriate carrier frequency is determined accordingly, so as to optimize the switching frequency and power output of the converter. It should also be noted that it measures the speed of change of the modulation signal with time, and a higher carrier frequency is required when the modulation wave change rate k is larger, and the carrier frequency can be appropriately lowered when the modulation wave change rate k is smaller.

[0027] In an optional embodiment, the first division operation can be realized by setting multiple thresholds, each threshold corresponding to a carrier frequency interval.

[0028] In an optional embodiment, the maximum and minimum values of the first change rate of the target modulation wave under the first working condition are first determined, and then according to actual needs, several thresholds are set between the maximum and minimum values, and the range of the first change rate is divided into several subintervals. Each subinterval corresponds to a specific carrier frequency or carrier frequency range, so as to quickly determine the appropriate first target carrier frequency according to the subinterval where the first change rate of the target modulation wave under the real-time working condition is located.

[0029] It should be noted that the specific carrier frequency or carrier frequency range is dynamically determined by the first frequency scaling factor and the rated frequency, specifically including: using the rated frequency when the modulation wave change rate is large (such as |k|>m), and using the reduced frequency when the change rate is small (such as |k|<m). The specific carrier frequency or carrier frequency range is dynamically switched according to the real-time modulation wave change rate and the preset parameters, so as to ensure that both the switching loss is reduced and the harmonics are controlled within the allowable range.

[0030] It should be noted that through such a division operation, the carrier frequency can be more finely controlled, further optimizing the switching frequency and power output, and improving the overall efficiency of the system.

[0031] In an optional embodiment, the first division operation can also be implemented by a machine learning algorithm, which can automatically divide the first variation rate of the target modulation wave under the first working condition into different intervals according to the data distribution characteristics of the first variation rate, and determine the corresponding carrier frequency of each interval. This method can more accurately reflect the relationship between the variation rate of the modulation wave and the carrier frequency, and further improve the performance of the system.

[0032] In an optional embodiment, the first division operation can also be determined by expert experience or engineering practice. According to the empirical formula or common cases in engineering practice, a series of threshold values and corresponding carrier frequencies are set. This method is simple and easy to implement, and can be quickly applied to actual systems.

[0033] In the embodiments of the present application, the first division operation includes: setting a first division point according to the first variation rate of the target modulation wave under the first working condition; dividing the first variation rate of the target modulation wave under the first working condition according to the first division point; the result of the first division operation corresponds to a plurality of carrier frequencies.

[0034] Specifically, the specific values of the first division points are first determined, which are selected based on the statistical characteristics of the first variation rate of the target modulation wave under the first working condition and the expected system performance requirements. Each first division point divides the range of the first variation rate into one or more subintervals, and each subinterval is associated with one or more carrier frequencies. In this way, the system can flexibly select the most suitable carrier frequency according to the subinterval in which the first variation rate of the target modulation wave under the real-time working condition is located.

[0035] It should be noted that the most suitable carrier frequency refers to the carrier frequency dynamically selected according to the comparison result of the real-time modulation wave variation rate k and the preset parameter m: when |k|>m, the rated frequency fn is selected to ensure the waveform quality; when |k|<m, the reduced frequency j⋅fn (where 0<j<1) is selected to reduce the switching loss, while the constraint condition ensures that the harmonic content does not exceed the limit.

[0036] In the embodiments of the present application, the division of the first division point affects the design of the subsequent first constraint, wherein the first division point can be a first frequency parameter, and the first frequency parameter is taken as the first division point.

[0037] For example, the first frequency parameter is denoted as m, and for the variation rate k of the modulation wave, the first division operation specifically represents when m<k<1, when -m<k<m, and when -1<k<-m. Such design can ensure that when the modulation wave varies rapidly, the carrier frequency is high, thereby maintaining the quality of the output waveform; and when the modulation wave varies slowly, the carrier frequency is low, which can reduce unnecessary switching operations and reduce switching loss.

[0038] It should be noted that the first change rate of the target modulation wave under the first working condition is obtained, and the first change rate is subjected to the first division operation, which can provide basic data and division basis for subsequent steps, so that the system can flexibly adjust the carrier frequency according to the change rate of the modulation wave. Specifically, by subjecting the first change rate to the first division operation, the system can divide different change rate ranges into different intervals, and determine one or more corresponding carrier frequencies for each interval. In this way, under the real-time working condition, the system can quickly select the most suitable carrier frequency for carrier mixing modulation according to the interval in which the first change rate of the target modulation wave is located. This way of dynamically adjusting the carrier frequency not only reduces unnecessary switching operations, reduces switching loss, and improves the overall efficiency of the system, but also ensures the quality of the output waveform, controls the harmonic content of the three-phase voltage and current within the target range, and meets the needs of actual applications. Therefore, obtaining the first change rate of the target modulation wave under the first working condition and subjecting the first change rate to the first division operation is one of the important steps for implementing the adjustable carrier mixing modulation method and system.

[0039] S102, obtaining a first change rate of a target modulation wave under a real-time working condition, and determining a first target carrier frequency according to a result of the first division operation; In an optional embodiment, the first target carrier frequency can be set according to the result of the first division operation. When there are two kinds of first division results, the first target carrier frequency can be divided into a first carrier frequency and a second carrier frequency, and the first carrier frequency and the second carrier frequency correspond to different ranges of the change rate of the modulation wave, respectively.

[0040] In an optional embodiment, the first change rate of the modulation wave is monitored in real time, and compared with the preset first division operation result, so as to determine the first target carrier frequency to be used under the current working condition. This design enables the carrier frequency to be dynamically adjusted according to the change of the modulation wave, which not only ensures the quality of the output waveform, but also effectively reduces the switching loss and improves the overall efficiency of the system.

[0041] In an optional embodiment, when there are more than two kinds of first division results, the system can further include a carrier frequency selector for selecting one from a plurality of preset carrier frequencies as the current first target carrier frequency according to the result of the first division operation. For example, when there are three kinds of first division results, the first target carrier frequency can be divided into a first carrier frequency, a second carrier frequency and a third carrier frequency, and each carrier frequency corresponds to a different range of the change rate of the modulation wave. In this way, the system can more accurately adjust the carrier frequency according to the change of the modulation wave, further optimize the quality of the output waveform, reduce the switching loss, and improve the overall performance and efficiency of the system.

[0042] In the embodiments of the present application, the first target carrier frequency is divided into a first carrier frequency and a second carrier frequency, which are configured together with the first division operation to achieve fine control of the carrier frequency. Among them, the first carrier frequency corresponds to the case where the modulation wave change rate is large, ensuring that the system can maintain a high carrier frequency when the modulation wave changes rapidly, thereby maintaining the quality of the output waveform. The second carrier frequency corresponds to the case where the modulation wave change rate is small, at which time the system can appropriately reduce the carrier frequency to reduce unnecessary switching operations and reduce switching loss. Through such a design, the present application can effectively improve the overall efficiency of the system while ensuring the quality of the output waveform.

[0043] It should be noted that obtaining the first change rate of the target modulation wave under real-time working conditions and determining the first target carrier frequency according to the first division operation result can quickly adjust the carrier frequency according to the real-time working conditions, so that the carrier frequency matches the change rate of the modulation wave, thereby reducing unnecessary switching operations, reducing switching loss, improving the overall efficiency of the system while ensuring the quality of the output waveform. In addition, through the preset first division operation result, the system can more quickly determine the appropriate first target carrier frequency, further improving the response speed and performance of the system.

[0044] S103, presetting a first constraint, and performing carrier mixing modulation based on the first constraint and the first target carrier frequency.

[0045] In an optional embodiment, the first constraint can be a further restriction or optimization condition for the carrier frequency to ensure the stability of the system and the quality of the output waveform. Specifically, the first constraint can include various factors such as maximum carrier frequency limit, minimum carrier frequency limit, carrier frequency change rate limit, etc., which are determined according to the actual system requirements and performance requirements.

[0046] In an optional embodiment, by presetting the first constraint and combining the previously determined first target carrier frequency, the system can consider not only the change rate of the modulation wave but also the stability of the system and the quality of the output waveform when performing carrier mixing modulation. For example, when the modulation wave change rate is large, the system may choose a higher carrier frequency to maintain the quality of the output waveform, but if the carrier frequency is too high at this time, it may cause the system to be unstable or generate too many harmonics. Therefore, by presetting the first constraint, the system can ensure the quality of the output waveform while avoiding problems caused by excessively high carrier frequency.

[0047] In an optional embodiment, the first constraint can be determined through experiments or simulations. For example, a simulation model similar to the actual system can be constructed, and by adjusting the carrier frequency and the constraint condition, the stability of the system and the quality of the output waveform are observed to determine the appropriate constraint condition. This method can more accurately reflect the performance requirements of the actual system and provide strong support for system design and optimization.

[0048] In addition, the first constraint can also be dynamically adjusted according to the actual application scenario. For example, in some application scenarios, there may be higher requirements for the quality of the output waveform, at which time the restriction on the carrier frequency can be appropriately relaxed to obtain better output waveform quality. In other application scenarios, if there are higher requirements for the stability of the system, the restriction on the carrier frequency can be strengthened to ensure the stable operation of the system.

[0049] In the embodiments of the present application, the preset first constraint comprises: The first constraint is used to constrain the harmonic content of the three-phase voltage and current within a target range; The first constraint is designed through a first frequency scaling factor and a first frequency parameter; The first constraint is for several different working conditions.

[0050] In the embodiments of the present application, the first constraint is designed through a first frequency scaling factor and a first frequency parameter, comprising: determining the first frequency parameter, and performing a first comparison operation on the first change rate and the first frequency parameter; presetting a first carrier frequency and a second carrier frequency; determining a specific selected first target carrier frequency according to the first comparison result; The first carrier frequency and the second carrier frequency are determined through a first frequency scaling factor.

[0051] It should be noted that the first comparison operation refers to comparing the value of the real-time obtained modulation wave change rate k with the preset first frequency parameter m, and selecting the corresponding carrier frequency according to the comparison result, so as to achieve the purpose of dynamically adjusting the carrier frequency.

[0052] Specifically, for the change rate k of the modulation wave, the segmented processing specifically shows (m is the first frequency parameter): When m < k < 1, the carrier frequency is set to the rated frequency f n (i.e. the first carrier frequency), at which time the waveform changes relatively sharply, the frequency changes greatly, and maintaining the rated frequency can ensure that the waveform quality is not affected; When -m < k < m, the carrier frequency is set to jf n(i.e. the second carrier frequency); wherein j is a carrier frequency proportionality coefficient, and j is in the range of 0 to 1, at this time, the modulation wave change rate is small, and appropriately reducing the carrier frequency can reduce the switching times and reduce the system loss, while the influence on the output waveform quality should be considered; When -1 < k < -m, the carrier frequency is set to recover to the rated frequency f n (i.e. the first carrier frequency), in the case of a large change rate, a higher carrier frequency is maintained to ensure system response speed and power quality; In the embodiments of the present application, the first frequency proportionality coefficient includes: The first frequency proportionality coefficient is adjusted according to the total harmonic distortion value of the output waveform of the target modular multilevel DC converter.

[0053] In an optional embodiment, the first frequency proportionality coefficient is adjusted according to the total harmonic distortion value of the output waveform of the target modular multilevel DC converter to ensure that the quality of the output waveform meets certain requirements. Specifically, when the total harmonic distortion value of the output waveform is detected to be out of the preset range, the system can automatically adjust the first frequency proportionality coefficient, thereby changing the carrier frequency, so that the total harmonic distortion value of the output waveform returns to the preset range. This method can realize dynamic optimization of the output waveform, and ensure that the system can output high-quality waveforms under various operating conditions.

[0054] In the embodiments of the present application, the adjustment of the first frequency proportionality coefficient can be realized by various methods. For example, the optimal first frequency proportionality coefficient corresponding to different total harmonic distortion values can be determined through experiments or simulations, and then stored in the system.

[0055] In an optional embodiment, during actual operation, the system can select the corresponding optimal first frequency proportionality coefficient from the stored data according to the real-time monitored total harmonic distortion value for adjustment. In addition, a model can also be trained through a machine learning algorithm, which can predict the optimal first frequency proportionality coefficient according to the total harmonic distortion value. In this way, the system can automatically adjust the carrier frequency in real time according to the quality of the output waveform, realizing intelligent waveform optimization.

[0056] In the embodiments of the present application, the steps of determining the first carrier frequency and the second carrier frequency through the first frequency proportionality coefficient include: The first carrier frequency (i.e. the rated frequency fn) corresponds to the case of the first frequency proportionality coefficient j = 1, and the second carrier frequency is obtained by multiplying the rated frequency fn by the first frequency proportionality coefficient j (wherein 0 < j < 1), i.e. j⋅fn, the specific value of which is determined by j, and is dynamically selected through the comparison result of the real-time modulation wave change rate and the parameter m, to realize the optimization balance of switching loss and waveform quality.

[0057] To sum up, the application provides an adjustable carrier mixing modulation method, obtains a first variation rate of a target modulation wave under a first working condition, and performs a first division operation on the first variation rate; obtains a first variation rate of the target modulation wave under a real-time working condition, determines a first target carrier frequency according to a result of the first division operation; presets a first constraint, and performs carrier mixing modulation based on the first constraint and the first target carrier frequency. The system can realize dynamic adjustment of the carrier frequency, determine the optimal carrier frequency according to the variation rate of the modulation wave, thereby reducing unnecessary switching operations, reducing switching loss, and improving the overall efficiency of the system. At the same time, through the preset constraint condition, the system can also ensure the quality of the output waveform, control the harmonic content of three-phase voltage and current within a target range, and meet the demand of actual application. In addition, the system also has good adaptability and flexibility, can be adjusted and optimized for different working conditions, and further improves its performance in actual application.

[0058] Embodiment 2 The embodiment provides an adjustable carrier mixing modulation system, comprising: A first operation module is configured to obtain a first variation rate of a target modulation wave under a first working condition, and perform a first division operation on the first variation rate. A frequency determination module is configured to obtain a first variation rate of a target modulation wave under a real-time working condition, and determine a first target carrier frequency according to a result of the first division operation. A modulation module is configured to preset a first constraint, and perform carrier mixing modulation based on the first constraint and the first target carrier frequency. The first constraint is designed by a first frequency proportional coefficient and a first frequency parameter, comprising: determining the first frequency parameter, performing a first comparison operation on the first variation rate and the first frequency parameter; presetting a first carrier frequency and a second carrier frequency; determining the first target carrier frequency selected according to a result of the first comparison; and determining the first carrier frequency and the second carrier frequency by the first frequency proportional coefficient.

[0059] The above-mentioned unit modules can be embedded in or independent of the processor in the computer device in hardware form, or can be stored in the memory in the computer device in software form, so as to call and execute the operations of the above-mentioned modules by the processor.

[0060] This embodiment also provides a computer device, which can be a terminal. The computer device includes a processor, a memory, a communication interface, a display screen, and an input device connected via a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The communication interface of the computer device is used to communicate with external terminals in a wired or wireless manner, and the wireless manner can be achieved through WIFI, carrier network, NFC (Near Field Communication) or other technologies. When the computer program is executed by the processor, it implements an adjustable carrier mixing modulation method. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer covered on the display screen, or a button, trackball or touchpad set on the computer device shell, or an external keyboard, touchpad or mouse, etc.

[0061] This embodiment also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the following steps are implemented: Obtain the first change rate of the target modulation wave under the first working condition, and perform a first partitioning operation on the first change rate; Obtain the first change rate of the target modulation wave under the real-time working condition, and determine the first target carrier frequency according to the result of the first partitioning operation; Preset a first constraint, and perform carrier mixing modulation based on the first constraint and the first target carrier frequency.

[0062] Embodiment 3 Refer to Figures 2-5 , which is an embodiment of the present invention, provides an adjustable carrier mixing modulation method and system, specifically including: During the normal operation of the modular multilevel DC converter system, first calculate the change rate k of the modulation wave in real time. The specific expression can be obtained by taking the derivative of the modulation wave: , Specifically, divide k into several different ranges according to its value, and correspondingly determine the appropriate carrier frequency, so as to optimize the switching frequency and power output of the converter; Perform segmented processing on the normalized modulation wave change rate k. Taking m = 0.5 as an example for analysis, for the modulation wave change rate k, the segmented processing is specifically as follows: When 0.5 < k < 1, set the carrier frequency to the rated frequency f n ; When -0.5 < k < 0.5, set the carrier frequency to jf​n ; wherein j is a carrier frequency proportional coefficient, and here, j = 0.5 is taken as an example for analysis, at this time, the modulation wave change rate is small, and the carrier frequency is reduced to half of the original; When -1 < k < -0.5, the carrier frequency is set to recover to the rated frequency f n ; In the above case, the first frequency parameter m = 0.5 and the frequency proportional coefficient j = 0.5, and when the absolute value of the modulation wave change rate is less than 0.5, the influence of the carrier frequency being reduced to half of the original on the voltage and current needs to be considered. First, the reduction of the carrier frequency leads to the extension of the modulation signal period, and the voltage waveform becomes more gentle, which may cause distortion. Second, the current response becomes more gentle and lags, which may cause the response speed to slow down, especially when the load changes greatly.

[0063] When the system works in the carrier frequency reduction interval, the total harmonic distortion (THD) value of the output waveform should be monitored in real time to evaluate the power quality. When the THD value of the waveform exceeds the preset limit, the frequency proportional coefficient j should be adjusted in time to effectively suppress the harmonic components by increasing the j value, so that the quality of the output waveform is restored to an acceptable range, and the power quality meets the system operation requirements.

[0064] It should be noted that, compared with the traditional carrier phase-shift modulation method, the present method does not need to increase an additional control loop, greatly simplifying the design of the control strategy. The adjustable carrier mixing modulation strategy not only improves the operating efficiency of the modular multi-level DC converter system, significantly reduces the switching loss, but also effectively ensures the high-quality output of the voltage and current waveforms. By reducing unnecessary switching, the efficiency of the system is improved, and the control design is simplified, which has high practical application value and engineering feasibility.

[0065] It should be noted that, in addition to considering the change rate of the modulation wave, the influence of the reduction of the carrier frequency on the power quality also needs to be considered. Although a lower carrier frequency can reduce switching loss, it may increase harmonic components, thereby affecting the power quality.

[0066] It should be noted that when adjusting the carrier frequency, the selection of the frequency proportional coefficient j and the parameter m should be optimized to ensure that the harmonic content is within the allowable range. This strategy dynamically adjusts the carrier frequency to ensure that the harmonic requirements of the voltage and current are met under different operating conditions, while the switching loss of the modular multi-level DC converter system can be greatly reduced.

[0067] It should be noted that, on the basis of the traditional carrier phase modulation, the switching loss of the modular multilevel DC converter system is effectively reduced by analyzing the modulation wave change rate in real time and dynamically adjusting the carrier frequency. On this basis, the influence of carrier frequency adjustment on voltage and current quality needs to be fully considered, including the influence on voltage and current harmonic characteristics. Therefore, the parameters m and the carrier frequency proportional coefficient j are set to ensure that the harmonic content of three-phase voltage and current remains within the specified allowable range during system operation.

[0068] It should be noted that the corresponding adjustable carrier mixed modulation waveform can be designed and generated according to the characteristics of any modulation waveform. Specifically, this strategy intelligently adjusts the carrier frequency by detecting the change rate of the modulation signal in real time to achieve dynamic loss reduction.

[0069] It should be noted that in specific implementation, when the modulation wave change rate is large, the carrier frequency is appropriately increased to meet the higher response requirement and improve the dynamic performance of the system; on the contrary, when the modulation wave change rate is small, the carrier frequency is reduced, thereby reducing high-frequency switching operation and effectively reducing switching loss.

[0070] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

[0071] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can adopt a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer usable storage media containing computer usable program code (including but not limited to disk storage, CD-ROM, optical storage, etc.). The solutions in the embodiments of the present application can be implemented in various computer languages.

[0072] The present application is described with reference to flowcharts and / or block diagrams according to the methods, devices (systems), and computer program products of the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device that implements the functions specified in the flowcharts and / or block diagrams. Figure 1one or more processes and / or blocks Figure 1 an apparatus for performing the functions specified in the flowchart

[0073] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the flowchart Figure 1 one or more processes and / or blocks Figure 1 an apparatus for performing the functions specified in the flowchart

[0074] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flowchart Figure 1 one or more processes and / or blocks Figure 1 an apparatus for performing the functions specified in the flowchart

[0075] While the preferred embodiments of the application have been described, additional variations and modifications can be made to the embodiments by those skilled in the art once they learn of the basic inventive concepts. Therefore, the appended claims are intended to cover all such additional variations and modifications as fall within the scope of the application.

[0076] Obviously, numerous modifications and variations of the present application are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A method for adjustable carrier mixing modulation, characterized in that, include: Obtain the first rate of change of the target modulated wave under the first operating condition, and perform a first division operation on the first rate of change; Obtain the first rate of change of the target modulated wave under real-time operating conditions, and determine the first target carrier frequency based on the result of the first division operation; A first constraint is preset, and carrier mixing modulation is performed based on the first constraint and the first target carrier frequency. The first constraint is designed using a first frequency scaling factor and a first frequency parameter; The first constraint, designed using a first frequency scaling factor and first frequency parameters, includes: Determine a first frequency parameter, and perform a first comparison operation between the first rate of change and the first frequency parameter; The first carrier frequency and the second carrier frequency are preset; The specific first target carrier frequency is determined based on the first comparison result; The first carrier frequency and the second carrier frequency are determined by a first frequency scaling factor.

2. The adjustable carrier mixing modulation method as described in claim 1, characterized in that, The first partitioning operation includes: The first dividing point is set according to the first rate of change of the target modulated wave under the first operating condition; The first rate of change of the target modulated wave under the first operating condition is divided according to the first dividing point; The result of the first partitioning operation corresponds to several carrier frequencies.

3. The adjustable carrier mixing modulation method as described in claim 2, characterized in that, The preset first constraint includes: The first constraint is used to constrain the harmonic content of the three-phase voltage and current within the target range; The first constraint applies to several different operating conditions.

4. The adjustable carrier mixing modulation method as described in claim 3, characterized in that, The first constraint, designed using a first frequency scaling factor and first frequency parameters, also includes: Determine the first frequency parameter m, and perform a first comparison operation between the first rate of change k and the first frequency parameter m; Preset first carrier frequency f n and the second carrier frequency jf n , where j is the first frequency scaling factor; The first target carrier frequency is determined based on the first comparison result, and the first target carrier frequency is selected from the first carrier frequency and the second carrier frequency. The first carrier frequency and the second carrier frequency are determined by a first frequency scaling factor; When the first carrier frequency is selected as the first target carrier frequency, the first frequency scaling factor is set to 1. When the second carrier frequency is selected as the first target carrier frequency, the first frequency scaling factor is j, and j≠1; When m < k < 1, set the carrier frequency to the rated frequency f n , that is, the first carrier frequency; When -m < k < m, set the carrier frequency as jf n , that is, the second carrier frequency, where j is the carrier frequency ratio coefficient; When -1 < k < -m, set the carrier frequency to return to the rated frequency f n , which is the first carrier frequency.

5. The adjustable carrier mixing modulation method as described in claim 4, characterized in that, The first frequency scaling factor includes: The first frequency scaling factor is adjusted based on the total harmonic distortion value of the output waveform of the target modular multilevel DC-DC converter.

6. The adjustable carrier mixing modulation method as described in claim 5, characterized in that, The process of obtaining the first rate of change of the target modulated wave under the first operating condition includes: The first rate of change of the target modulated wave under the first operating condition is obtained by performing a first analysis on the derivative or differential signal of the modulated wave.

7. The adjustable carrier mixing modulation method as described in claim 6, characterized in that, The first operating condition is the normal operating condition of the target modular multilevel DC-DC converter.

8. A tunable carrier mixing modulation system, applied to a tunable carrier mixing modulation method as described in any one of claims 1 to 7, characterized in that, include: The first operation module is used to obtain the first rate of change of the target modulated wave under the first operating condition, and to perform a first division operation on the first rate of change. The frequency determination module is used to obtain the first rate of change of the target modulated wave under real-time operating conditions and determine the first target carrier frequency based on the result of the first division operation. A modulation module is used to preset a first constraint and perform carrier mixing modulation based on the first constraint and the first target carrier frequency. The first constraint, designed using a first frequency scaling factor and a first frequency parameter, includes: determining the first frequency parameter; performing a first comparison operation between the first rate of change and the first frequency parameter; presetting a first carrier frequency and a second carrier frequency; determining a specific first target carrier frequency based on the first comparison result; and determining the first carrier frequency and the second carrier frequency using the first frequency scaling factor.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 7.

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