Modulation Method and Device of a Combined Multilevel Converter with T-Type Cells and Half-Bridge Cells

Abstract

The present invention discloses a modulation method and device for a combined multilevel converter of a T-type unit and a half-bridge unit. The multilevel converter includes a T-type unit and a half-bridge unit connected in series. The modulation method includes: when the modulation ratio m satisfies 0.556 ≤ m ≤ 1, determining the conduction angle θ of the half-bridge unit according to the modulation ratio m: #imgabs0# determining the modulation wave V H,ref (t) of the half-bridge unit and the modulation wave V T，ref (t) of the T-type unit; performing stepped-wave modulation on the half-bridge unit according to the modulation wave V H,ref (t), and performing high-frequency PWM modulation on the T-type unit according to the modulation wave V T，ref (t). By adopting the modulation method and device of the present invention, the output power balance of two DC power supplies in the converter is achieved without affecting the output performance of the converter, and the long-term stable operation performance of the converter is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and in particular, relates to a modulation technology of a multi-level converter, and more particularly, to a modulation method and device of a multi-level converter combining a T-type unit and a half-bridge unit. Background Art

[0002] As a key carrier for realizing power conversion in various fields such as power generation, transmission and distribution, multi-level converters use multi-level technology to change the topology structure, reduce the voltage stress of a single device, and use low-voltage devices to achieve high-voltage, multi-level output. Multi-level converters have a smaller voltage jump amplitude and a higher equivalent output frequency, and have a higher output voltage waveform quality, which reduces the system's requirements for filtering devices. Using fewer power devices and power supplies to achieve more levels of output to improve the quality of converter output power has always been one of the most active research directions in power electronics technology.

[0003] In the prior art, two full-bridge cascade multilevel converters are composed of only eight power devices and two DC power supplies; when the rated voltage ratio of the two DC power supplies is 1:3, the output voltage is as high as nine levels. However, the specifications of the two power supplies in this topology are inconsistent, the power output is seriously unbalanced, and if the modulation is improper, it is easy to cause the high-voltage unit to flow back to the low-voltage unit.

[0004] like Figure 1 As shown in FIG. 1 , a T-type cell and half-bridge cell combined (TCHC) multi-level converter is another commonly used topology structure in the prior art, which consists of only eight power devices S 1 -S 8 It is composed of two DC power supplies with equal rated voltages, and its output voltage can be as high as nine levels. TCHC multi-level converter is a multi-level topology with great application value and market competitiveness. Figure 1 As shown, the TCHC multi-level converter includes a T-type unit and a half-bridge unit. The two units are connected by two switching devices S 5 , S 6 Cross-connected to form a series connection structure. The DC side power supply voltage V dc1 The DC side power supply voltage V dc2 The rated values ​​are the same, both are E. The T-type unit includes three terminals, namely X, P 1 、N 1 , endpoint X and endpoint P 1 A switch device S is connected between 1 , endpoint X and endpoint N 1 A switch device S is connected between 4 , located at endpoint P1 In parallel with the DC power supply between the end point N 1 are two capacitors C 11 and C 12 . A switching device S 2 and S 3 are connected in series between the end point X and the connection point between the two capacitors. The half-bridge unit includes three end points, namely Y, P 2 , N 2 . A switching device S 2 is connected between the end point Y and the end point N 7 , and a switching device S 2 is connected between the end point Y and the end point P 8 . The end point X of the T-type unit and the end point Y of the half-bridge unit are used as two output end points of the converter to connect the load. When the TCHC multilevel converter of this structure works, in the positive half power frequency cycle, S 6 is always turned on and S 5 is turned off, then the converter output voltage V XY =V XN1 +V P2Y ; in the negative half power frequency cycle, S 5 is always turned on and S 6 is turned off, then the converter output voltage V XY =V XP1 +V N2Y . In the positive half power frequency cycle, by changing the values of V XN1 and V P2Y , multilevel output can be achieved; while in the negative half power frequency cycle, by changing the values of V XP1 and V N2Y , multilevel output can be achieved.

[0005] For the TCHC multilevel converter, the traditional modulation method is to use stepped wave modulation for the half-bridge unit. The conduction angle θ of the half-bridge unit is determined according to the intersection point of the sine voltage output by the converter and the horizontal voltage E. When the modulation ratio m satisfies 0 < m < 0.5, the conduction angle θ = π / 2; when the modulation ratio m satisfies 0.5 ≤ m ≤ 1, the conduction angle Adopting this traditional modulation method can ensure that the converter output voltage is a sine wave and meet the requirements of the converter output performance. However, due to the difference in the working states of the T-type unit and the half-bridge unit, when using the traditional modulation method and the modulation ratio is greater than 0.5, the output powers of the two DC power supplies of the T-type unit and the half-bridge unit are inconsistent. If running for a long time, due to the power imbalance of the two DC power supplies, the service life of the DC power supply will be reduced, and the output power quality of the converter will also be affected, which affects the long-term stable operation of the converter. Summary of the Invention

[0006] The object of the present invention is to provide a modulation method and device for a combined multilevel converter of a T-type unit and a half-bridge unit, which can achieve the balance of the output powers of two DC power supplies in the converter without affecting the output performance of the converter, and improve the long-term stable operation performance of the converter.

[0007] To achieve the above object of the invention, the modulation method provided by the present invention is implemented by the following technical solutions:

[0008] A modulation method for a combined multilevel converter of a T-type unit and a half-bridge unit, the multilevel converter includes a T-type unit and a half-bridge unit connected in series, and the modulation method includes:

[0009] When the modulation ratio m satisfies 0.556 ≤ m ≤ 1, the conduction angle θ of the half-bridge unit is determined according to the modulation ratio m:

[0010] The modulation wave V of the half-bridge unit and the modulation wave V of the T-type unit are determined according to the conduction angle θ H,ref (t): T，ref (t):

[0011]

[0012]

[0013] The half-bridge unit is subjected to stepped wave modulation according to the modulation wave V H,ref (t), and the T-type unit is subjected to high-frequency PWM modulation according to the modulation wave V T，ref (t).

[0014] In some embodiments of the present application, the modulation method further includes:

[0015] When the modulation ratio m satisfies 0 < m < 0.5, the conduction angle θ is determined as: θ = π / 2;

[0016] When the modulation ratio m satisfies 0.5 ≤ m < 0.556, the conduction angle θ is determined as:

[0017] To achieve the aforementioned object of the invention, the modulation device provided by the present invention is implemented by the following technical solutions:

[0018] A modulation device for a combined multilevel converter of a T-type unit and a half-bridge unit, the multilevel converter includes a T-type unit and a half-bridge unit connected in series, and the modulation device includes:

[0019] A conduction angle determination unit, configured to determine the conduction angle of the half-bridge unit, and when the modulation ratio m satisfies 0.556 ≤ m ≤ 1, determine the conduction angle θ of the half-bridge unit according to the modulation ratio m:

[0020] A modulation wave determination unit of the half-bridge unit, configured to determine the modulation wave V of the half-bridge unit according to the following formula H,ref (t):

[0021] A modulation wave determination unit of the T-type unit, configured to determine the modulation wave V of the T-type unit according to the following formula T，ref (t):

[0022] A modulation unit, configured to perform stepped wave modulation on the half-bridge unit according to the modulation wave V H,ref (t), and is further configured to perform high-frequency PWM modulation on the T-type unit according to the modulation wave V T，ref (t).

[0023] In some embodiments of the present application, the conduction angle determination unit is further configured to, when the modulation ratio m satisfies 0 < m < 0.5, determine the conduction angle θ as: θ = π / 2; and is further configured to, when the modulation ratio m satisfies 0.5 ≤ m < 0.556, determine the conduction angle θ as:

[0024] Another object of the present invention is to provide an electronic device, including a processor, a memory, and a computer program stored on the memory, where the processor is configured to execute the computer program to implement the modulation method of the combined multi-level converter of the T-type unit and the half-bridge unit as described above.

[0025] Another object of the present invention is a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the modulation method of the combined multi-level converter of the T-type unit and the half-bridge unit as described above is implemented.

[0026] Compared with the prior art, the advantages and positive effects of the present invention are:

[0027] The modulation method and device for a combined multilevel converter of T-type units and half-bridge units provided by the present invention, when the modulation ratio is within a specific numerical range, determine the conduction angle of the half-bridge unit according to a specific relational expression and the modulation ratio adjustment, then determine the modulation wave of the half-bridge unit and the modulation wave of the T-type unit based on the conduction angle, and perform stepped wave modulation on the half-bridge unit and high-frequency PWM modulation on the T-type unit according to the modulation wave, so that the fundamental amplitude of the output voltage of the half-bridge unit is equal to the fundamental amplitude of the output voltage of the T-type unit, and the output powers of the two units are equal. When ignoring the device power loss, the output powers of the DC side power supplies of the two units are equal, realizing the balanced modulation of the output powers of the two power supplies when the modulation ratio is within a specific numerical range; at the same time, it does not affect the overall output power quality of the converter, achieving the balance of the output powers of the two DC power supplies in the converter without affecting the output performance of the converter, and improving the long-term stable operation performance of the converter.

[0028] After reading the specific embodiments of the present invention in conjunction with the accompanying drawings, other features and advantages of the present invention will become clearer. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 FIG. is a schematic diagram of a topological structure of a combined multilevel converter of T-type units and half-bridge units in the prior art;

[0031] Figure 2 FIG. is a waveform diagram of the expected output voltage of the half-bridge unit and the expected output voltage of the T-type unit of the combined multilevel converter of T-type units and half-bridge units;

[0032] Figure 3 FIG. is a curve diagram of the change of the fundamental amplitude of the output voltage and the modulation ratio obtained by using the modulation method of the combined multilevel converter of T-type units and half-bridge units of the present invention;

[0033] Figure 4 FIG. is a waveform comparison diagram of the output voltage of the converter obtained by using the modulation method of the combined multilevel converter of T-type units and half-bridge units of the present invention and the output voltage of the converter obtained by using the prior art modulation method;

[0034] Figure 5 FIG. is a waveform comparison diagram of the output voltage of the half-bridge unit obtained by using the modulation method of the combined multilevel converter of T-type units and half-bridge units of the present invention and the output voltage of the half-bridge unit obtained by using the prior art modulation method;

[0035] Figure 6 Waveform comparison diagram of the output voltage of the T-type unit obtained by using the modulation method of the combined multilevel converter of the T-type unit and the half-bridge unit of the present invention and the output voltage of the T-type unit obtained by using the modulation method of the prior art;

[0036] Figure 7 Comparison diagram of the output voltage spectrum of the converter obtained by using the modulation method of the combined multilevel converter of the T-type unit and the half-bridge unit of the present invention and the output voltage spectrum of the converter obtained by using the modulation method of the prior art;

[0037] Figure 8 Structural schematic diagram of an embodiment of the modulation device of the combined multilevel converter of the T-type unit and the half-bridge unit of the present invention. Detailed implementation manners

[0038] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0039] In the prior art, for the combined multilevel converter of the T-type unit and the half-bridge unit, the traditional modulation method only focuses on the output performance of the converter, and does not consider the problem of the output power balance of the DC power supplies of the two units. After long-term operation, it will reduce the service life of the DC power supplies, and will also affect the output power quality of the converter, affecting the long-term stable operation of the converter. The present invention has conducted sufficient research and analysis on the converter of this topological structure, and creatively proposed a new type of converter modulation method and device. When the modulation ratio is within a specific numerical range, the conduction angle of the half-bridge unit is appropriately adjusted, so as to achieve the balance of the output power of the two DC power supplies when the modulation ratio is a specific value, and does not affect the overall output power quality of the converter, improving the long-term stable operation performance of the converter.

[0040] First, a brief description will be given to the theoretical analysis and derivation process of the modulation method of the converter proposed by the present invention.

[0041] For Figure 1 The combined multilevel converter of the T-type unit and the half-bridge unit shown, the T-type unit and the half-bridge unit are in series relationship. Therefore, the output voltage of the converter can be regarded as the superposition of the output voltages of the T-type unit and the half-bridge unit, that is:

[0042] V XY =V T +V H (1-1).

[0043] In the formula, V XY is the output voltage of the converter, V T is the output voltage of the T-type unit, and V H is the output voltage of the half-bridge unit.

[0044] Assume that the expected output voltage of the converter is:

[0045] V XY = m×2E sinωt (1-2).

[0046] Where m is the modulation ratio, ω is the angular frequency, and E is the power supply voltage of each unit.

[0047] Assume that the expression of the output current of the converter is:

[0048] i o = I o sin(ωt-α) (1-3).

[0049] Where I o is the phase current amplitude and α is the power factor angle.

[0050] Since the T-type unit and the half-bridge unit are in series, the current flowing through the two units is equal to the output current i o . Ignoring the device power loss, the output power of each power supply is equal to the average power of its unit. The average powers P T 、P H of the T-type unit and the half-bridge unit can be expressed as:

[0051]

[0052] Where T s is the power frequency period.

[0053] The output voltage of each unit contains a fundamental frequency component and a high-order harmonic component. According to mathematical knowledge, the integral of the high-order harmonic voltage component and the fundamental frequency current component within a power frequency period T s is equal to zero. Therefore, Equation (1-4) can be further simplified to:

[0054]

[0055] Where V T(1) and V H(1) are the fundamental voltage amplitudes of the T-type unit and the half-bridge unit, respectively.

[0056] According to Equation (1-5), the ratio of the output powers of the T-type unit and the half-bridge unit is:

[0057]

[0058] It can be seen from Equation (1-6) that the ratio of the output powers of the two power supplies is the same as the ratio of the fundamental voltage amplitudes of the two units.

[0059] Figure 2The figure shows the expected output voltage waveform diagram of the half-bridge unit and the T-type unit in the combined multilevel converter of the T-type unit and the half-bridge unit, and the expected output voltage waveform diagram of the T-type unit. Among them, Figure 2 (a) is the expected output voltage waveform diagram of the half-bridge unit, Figure 2 (b) is the expected output voltage waveform diagram of the T-type unit.

[0060] As Figure 2 (a) shows, the expected output voltage V H of the half-bridge unit is a three-level stepped wave, θ is the conduction angle of the half-bridge unit, 0 ≤ θ ≤ π / 2, and the general Fourier expression of V H is:

[0061]

[0062] In the formula, a 0 , a n , b n are all Fourier coefficients.

[0063] Since V H is an odd function, so a 0 = 0, a n = 0, and b n can be expressed as:

[0064]

[0065] By combining equations (1-7) and (1-8), we can get:

[0066]

[0067] According to equation (1-9), the fundamental amplitude of the output voltage of the half-bridge unit can be obtained as:

[0068]

[0069] Theoretically, it can be known that if the fundamental amplitude V H(1) of the half-bridge unit is always 1 / 2 of the fundamental amplitude V XY(1) of the output voltage of the converter, the output power balance of the two power supplies can be achieved.

[0070] According to equation (1-10), V H(1) is related to the conduction angle θ of the half-bridge unit. If the value of θ is changed, the magnitude of V H(1) can be adjusted. Under this constraint condition, we can get:

[0071]

[0072] After further simplification, the relationship between the conduction angle θ and the modulation ratio m can be obtained as:

[0073]

[0074] During the positive half - cycle, V T The instantaneous expression is as follows:

[0075]

[0076] Since the T - type unit and the half - bridge unit are connected in series with the same polarity, that is: during the positive half - cycle, the instantaneous output voltages of the two units are both non - negative, and during the negative half - cycle, the output voltages are both non - positive. Therefore, during the positive half - cycle, it is necessary to satisfy that V T ≥0 always holds, which is equivalent to that the following formula must hold within the range of θ < ωt < π - θ:

[0077] V T =(2Em sinωt - E)≥0 (1 - 14).

[0078] According to the knowledge of trigonometric functions, within the range of θ < ωt < π - θ, when ωt = θ, V T obtains the minimum value. Therefore, formula (1 - 14) can be further equivalently expressed as the following formula always holds:

[0079] 2m sinθ - 1≥0 (1 - 15). Substituting formula (1 - 12) into formula (1 - 15) and simplifying gives:

[0080] π 2 m 4 -16m 2 +4≤0 (1 - 16).

[0081] The value range of m obtained is:

[0082] 0.556≤m≤1.15 (1 - 17).

[0083] To avoid over - modulation, m needs to satisfy:

[0084] 0.556≤m≤1.0 (1 - 18).

[0085] The above formula shows that when the modulation ratio m is within the range of [0.556, 1.0], by appropriately adjusting the conduction angle of the half - bridge unit, the balanced output power of the two power supplies can be achieved.

[0086] Based on the above analysis and derivation, an embodiment of the present invention proposes a modulation method for a combined multilevel converter of a T - type unit and a half - bridge unit. The multilevel converter includes a T - type unit and a half - bridge unit connected in series. The modulation method includes:

[0087] When the modulation ratio m satisfies 0.556≤m≤1, determine the conduction angle θ of the half - bridge unit according to the modulation ratio m:

[0088] Then, determine the modulation wave V of the half-bridge unit and the modulation wave V of the T-type unit according to the conduction angle θ: H,ref (t): T，ref (t):

[0089]

[0090]

[0091] Finally, perform stepped-wave modulation on the half-bridge unit according to the modulation wave V H,ref (t), and perform high-frequency PWM modulation on the T-type unit according to the modulation wave V T，ref (t).

[0092] To ensure the output performance of the converter, when the modulation ratio m satisfies 0 < m < 0.5, determine the conduction angle θ as: θ = π / 2; while when the modulation ratio m satisfies 0.5 ≤ m < 0.556, determine the conduction angle θ as: Then, determine the modulation waves of the two units according to the determined conduction angle and the above modulation wave calculation formula.

[0093] Figure 3 Shows the fundamental amplitude V of the output voltage of the half-bridge unit obtained by using the above modulation method H(1) , the fundamental amplitude V of the output voltage of the T-type unit T(1) , the fundamental amplitude V of the output voltage of the converter XY(1) And the change curve diagram of the modulation ratio. From Figure 3 It can be seen that when the modulation ratio m satisfies 0 < m < 0.5, V H(1) Is always equal to zero; when the modulation ratio satisfies 0.556 ≤ m ≤ 1, the fundamental amplitudes V of the output voltages of the two power supplies H(1) , V T(1) Are basically equal.

[0094] Build a simulation model of the 9L-TCHC converter with the structure shown in Figure 1 using Matlab / Simulink software, and perform simulation according to the simulation model. The specific simulation circuit parameters are shown in Table 1-1.

[0095] Table 1-1 Simulation circuit parameters

[0096]

[0097] Use the aforementioned modulation method to perform modulation simulation on the established model. When the modulation ratio m = 0.9, obtain the modulation waveform diagram, and compare the waveforms with the modulation method of the existing technology to obtain Figure 4 , Figure 5 , Figure 6 And Figure 7 The waveform comparison diagrams shown.

[0098] Figure 4 The figure shows a waveform comparison diagram of the converter output voltage (after power balance) obtained by using the modulation method of the T-type unit and half-bridge unit combined multilevel converter of the present invention and the converter output voltage (before power balance) obtained by using the modulation method of the prior art. From Figure 4 It can be seen that before and after power balance modulation, the converter output voltage is a nine-level stepped wave, and the fundamental amplitude of the converter output voltage before power balance is 539V, while the fundamental amplitude of the converter output voltage after power balance is 533V. The fundamental amplitudes of the voltage before and after power balance are basically the same, indicating that the power balance modulation method does not affect the output of the converter.

[0099] Figure 5 The figure shows a waveform comparison diagram of the output voltage of the half-bridge unit (after power balance) obtained by using the modulation method of the T-type unit and half-bridge unit combined multilevel converter of the present invention and the output voltage of the half-bridge unit (before power balance) obtained by using the modulation method of the prior art. Figure 6 The figure shows a waveform comparison diagram of the output voltage of the T-type unit (after power balance) obtained by using the modulation method of the T-type unit and half-bridge unit combined multilevel converter of the present invention and the output voltage of the T-type unit (before power balance) obtained by using the modulation method of the prior art.

[0100] From Figure 5 It can be seen that the fundamental amplitude of the output voltage of the half-bridge unit before power balance is 317V, and the fundamental amplitude of the output voltage of the half-bridge unit after power balance is 267V. From Figure 6 It can be seen that the fundamental amplitude of the output voltage of the T-type unit before power balance is 221V, and the fundamental amplitude of the output voltage of the T-type unit after power balance is 265V. From this, it can be obtained that before power balance, the difference in the fundamental amplitudes of the output voltages of the two units is (317 - 221) = 96V. After power balance, the difference in the fundamental amplitudes of the output voltages of the two units is (267 - 265) = 2V. This result shows that the power balance modulation method realizes the balance of the fundamental amplitudes of the output voltages of the two units, which also means the balance of the output powers of the two power supplies.

[0101] Figure 7 (a) and Figure 7 (b) respectively show a comparison diagram of the converter output voltage spectrum obtained by using the modulation method of the T-type unit and half-bridge unit combined multilevel converter of the present invention and the converter output voltage spectrum obtained by using the modulation method of the prior art. From Figure 7It can be seen that after modulation by the power equalization modulation method, in the output voltage spectrum diagram of the converter, except for some low-order harmonics, the distribution of the remaining harmonics is basically the same as that before the power equalization modulation; moreover, before and after the power equalization modulation, the THD values (harmonic content values) of the two are not much different. Therefore, it further shows that the power equalization modulation method can achieve the output power equalization of two DC power supplies without affecting the output power quality of the converter.

[0102] Figure 8 The figure shows a schematic structural diagram of an embodiment of a modulation device for a combined multi-level converter of a T-type unit and a half-bridge unit according to the present invention.

[0103] As Figure 8 shown, the structural units included in the modulation device of this embodiment, the functions of the structural units, and the relationships between them are as follows:

[0104] The modulation device includes:

[0105] A conduction angle determination unit 81, configured to determine the conduction angle of the half-bridge unit, and when the modulation ratio m satisfies 0.556 ≤ m ≤ 1, determine the conduction angle θ of the half-bridge unit according to the modulation ratio m:

[0106] A modulation wave determination unit 82 for the half-bridge unit, configured to determine the modulation wave V H,ref (t) of the half-bridge unit according to the following formula:

[0107] A modulation wave determination unit 83 for the T-type unit, configured to determine the modulation wave V T，ref (t) of the T-type unit according to the following formula:

[0108] A modulation unit 84, configured to perform stepped wave modulation on the half-bridge unit according to the modulation wave V H,ref (t), and is also configured to perform high-frequency PWM modulation on the T-type unit according to the modulation wave V T，ref (t).

[0109] In some other embodiments, in order to ensure the output performance of the converter, the conduction angle determination unit is further configured to determine the conduction angle θ as: θ = π / 2 when the modulation ratio m satisfies 0 < m < 0.5; and is further configured to determine the conduction angle θ as: The modulation wave determination unit for the half-bridge unit and the modulation wave determination unit for the T-type unit determine the corresponding modulation waves according to the determined conduction angle.

[0110] By adopting the above modulation method and device for the combined multi-level converter of T-type unit and half-bridge unit, when the modulation ratio is within a specific numerical range, the conduction angle of the half-bridge unit is determined according to a specific relational expression and the modulation ratio adjustment. Then, based on the conduction angle, the modulation wave of the half-bridge unit and the modulation wave of the T-type unit are determined. And according to the modulation waves, the half-bridge unit is subjected to stepped wave modulation and the T-type unit is subjected to high-frequency PWM modulation, so that the fundamental wave amplitude of the output voltage of the half-bridge unit is equal to the fundamental wave amplitude of the output voltage of the T-type unit, and the output powers of the two units are equal. When the device power loss is ignored, the output powers of the DC side power supplies of the two units are equal, realizing the balanced modulation of the output powers of the two power supplies when the modulation ratio is within a specific numerical range, and prolonging the service life of the power supply. At the same time, it will not affect the overall output power quality of the converter, achieving the balance of the output powers of the two DC voltages in the converter without affecting the output performance of the converter, and improving the long-term stable operation performance of the converter.

[0111] Some embodiments of the present invention also provide an electronic device. The electronic device includes a processor, a memory, and a computer program stored on the memory. The processor is configured to execute the computer program to implement the modulation method of the combined multi-level converter of T-type unit and half-bridge unit in the above embodiments, and achieve the technical effects of the corresponding embodiments.

[0112] Other embodiments of the present invention also provide a computer storage medium. A computer program is stored on the computer storage medium. When the computer program is executed by a processor, it implements the modulation method of the combined multi-level converter of T-type unit and half-bridge unit in the above embodiments, and achieves the technical effects of the corresponding embodiments.

[0113] The above computer storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic disk or optical disk. The computer storage medium can be any available storage medium accessible by a general-purpose or special-purpose computer.

[0114] In some embodiments, the computer storage medium is coupled to the processor, so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can be located in an application specific integrated circuit (ASIC). Of course, the processor and the storage medium can also exist as discrete components in the device.

[0115] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, for those of ordinary skill in the art, it is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions required to be protected by the present invention.

Claims

1. A modulation method for a combined multilevel converter of a T-type unit and a half-bridge unit, the multilevel converter comprising a T-type unit and a half-bridge unit connected in series. Characterized in that, The modulation method includes: When the modulation ratio m satisfies 0.556 ≤ m ≤ 1, determining the conduction angle θ of the half-bridge unit according to the modulation ratio m: Determine the modulation wave V of the half-bridge unit and the modulation wave V of the T-type unit according to the conduction angle θ H,ref (t): T，ref (t) as follows: According to the modulation wave V H,ref (t), perform stepped wave modulation on the half-bridge unit, and according to the modulation wave V T，ref (t), perform high-frequency PWM modulation on the T-type unit.

2. The modulation method for a combined multilevel converter of a T-type unit and a half-bridge unit according to claim 1, Characterized in that, The modulation method further includes: When the modulation ratio m satisfies 0 < m < 0.5, determining the conduction angle θ as: θ = π / 2; When the modulation ratio m satisfies 0.5 ≤ m < 0.556, determine the conduction angle θ as:

3. A modulation device for a combined multilevel converter of a T-type unit and a half-bridge unit, the multilevel converter comprising a T-type unit and a half-bridge unit connected in series. Characterized in that, The modulation device includes: A conduction angle determination unit is configured to determine a conduction angle of the half-bridge unit, and when a modulation ratio m satisfies 0.556 ≤ m ≤ 1, determine the conduction angle θ of the half-bridge unit according to the modulation ratio m: The modulation wave determination unit of the half-bridge unit is used to determine the modulation wave V of the half-bridge unit according to the following formula H,ref (t): The modulation wave determination unit of the T-type unit is used to determine the modulation wave V of the T-type unit according to the following formula T，ref (t): A modulation unit, configured to perform stepped-wave modulation on the half-bridge unit according to the modulation wave V H,ref (t), and further configured to perform high-frequency PWM modulation on the T-type unit according to the modulation wave V T，ref (t).

4. The modulation device for a combined multilevel converter of a T-type unit and a half-bridge unit according to claim 3, Characterized in that, The conduction angle determination unit is further configured to determine the conduction angle θ as: θ = π / 2 when the modulation ratio m satisfies 0 < m < 0.5; and is further configured to determine the conduction angle θ as:

5. An electronic device, comprising a processor, a memory, and a computer program stored on the memory. Characterized in that, The processor is configured to execute the computer program to implement the modulation method for a combined multilevel converter of a T-type unit and a half-bridge unit according to claim 1 or 2 above.

6. 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 modulation method for a combined multilevel converter of a T-type unit and a half-bridge unit according to claim 1 or 2 above.

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