A 3TSMC Control Method for Improving the Maximum Voltage Transfer Ratio

Abstract

The present application discloses a 3TSMC control method for improving the maximum voltage transfer ratio, which relates to the field of three - harmonic injection dual - stage matrix converters. This method pre - designs the over - modulation strategies for each of the three over - modulation regions. In over - modulation region I, the virtual bus voltage is increased to raise the reference bus voltage, thereby increasing the voltage transfer ratio. In over - modulation region II, the minimum phase - error over - modulation of the inverter stage is utilized to change the amplitude of the inverter - stage output voltage to increase the modulation ratio of the inverter stage, thus increasing the voltage transfer ratio. In over - modulation region III, the basic - vector - maintaining over - modulation of the inverter stage is used to change the amplitude and phase angle of the inverter - stage output voltage to increase the modulation ratio of the inverter stage, thereby increasing the voltage transfer ratio. By selecting different over - modulation strategies according to the required modulation ratio to obtain the duty cycle required for space - vector modulation and then obtaining the driving signals of the inverter - stage switching tubes, the effect of improving the voltage transfer ratio can be achieved.

Description

Technical Field

[0001] This application relates to the field of three - harmonic - injection dual - stage matrix converters, and particularly to a 3TSMC control method for improving the maximum voltage transfer ratio. Background Art

[0002] The three - harmonic - injection dual - stage matrix converter (3TSMC) is a new type of matrix converter (MC) based on a hybrid three - harmonic - injection rectifier. It inherits most of the advantages of traditional matrix converters and also has advantages such as stronger reactive - power control ability, decoupling of the rectifier stage and the inverter stage, and the maximum linear voltage transfer ratio is not affected by the input - side power factor. Therefore, it is more suitable for occasions such as AC motor speed - regulation systems, wind turbine generators, flexible AC transmission, and aviation starting - power generation systems.

[0003] However, as a buck - type power converter, the maximum linear voltage transfer ratio of 3TSMC is limited to 0.866. The relatively low voltage transfer ratio restricts the application range of 3TSMC: in AC speed - regulation systems, it limits the speed - regulation range of motors, and the devices need to withstand higher voltages, which may lead to device damage or shortened lifespan. Summary of the Invention

[0004] In view of the above problems and technical requirements, this application proposes a 3TSMC control method for improving the maximum voltage transfer ratio. The technical solution of this application is as follows:

[0005] A 3TSMC control method for improving the maximum voltage transfer ratio, the 3TSMC control method includes:

[0006] Collect the three - phase input voltages of the three - harmonic - injection dual - stage matrix converter and calculate the amplitude U of the three - phase input voltages im , determine the amplitude U of the three - phase reference output voltages and the phase angle θ om according to the given three - phase reference output voltages r , and calculate the modulation ratio and the vector position angle of the output voltage vector in the sector where it is located where, / / is the remainder operator;

[0007] When the modulation ratio m < 0.866, determine the duty cycle required for space - vector modulation according to the three - phase input voltages and the vector position angle θ;

[0008] When 0.866 ≤ m < m1, it is determined that it is in over - modulation region I, determine the reference bus voltage as and calculate the virtual bus voltage u dcvir , and determine the duty cycle required for space - vector modulation according to the virtual bus voltage u dcvir in combination with the vector position angle θ;

[0009] When the modulation ratio m1 ≤ m < m2, it is determined that the overmodulation region II is in effect. According to the relationship between the voltage vector trajectory and the output voltage waveform during overmodulation with the minimum phase error of the inverter stage, the duty cycle required for space vector modulation is determined by combining the modulation ratio m and the vector position angle θ.

[0010] When the modulation ratio m ≥ m2, it is determined that the overmodulation region III is in effect. According to the relationship between the voltage vector trajectory and the output voltage waveform during overmodulation with the basic vectors of the inverter stage remaining unchanged, the duty cycle required for space vector modulation is determined by combining the modulation ratio m and the vector position angle θ.

[0011] According to the phase angle θ of the three-phase input voltage i Determine the driving signals for the rectifier stage switching tubes and the bidirectional switching tubes to drive the rectifier stage switching tubes and the bidirectional switching tubes in the 3TSMC. Pulse width modulation is performed according to the duty cycle required for space vector modulation to obtain the driving signals for the inverter stage switching tubes to drive the switching tubes in the three-phase bridge arm of the inverter stage of the 3TSMC.

[0012] Among them, in the overmodulation region I, by increasing the virtual bus voltage u dcvir To increase the reference bus voltage u dcref To increase the voltage transfer ratio. In the overmodulation region II, on the basis of keeping the reference bus voltage u dcref At its maximum value, by changing the amplitude of the output voltage of the inverter stage to increase the modulation ratio of the inverter stage to increase the voltage transfer ratio. In the overmodulation region III, on the basis of keeping the reference bus voltage u dcref At its maximum value, by changing the amplitude and phase angle of the output voltage of the inverter stage to increase the modulation ratio of the inverter stage to increase the voltage transfer ratio.

[0013] The beneficial technical effects of this application are:

[0014] This application discloses a 3TSMC control method for improving the maximum voltage transfer ratio. This method does not require changing the topology of the three-harmonic injection dual-stage matrix converter. By using different overmodulation strategies corresponding to the designed three overmodulation regions, the duty cycle required for space vector modulation can be obtained by selecting different overmodulation strategies according to the required modulation ratio, and then pulse width modulation is performed to obtain the driving signals for the inverter stage switching tubes to drive the switching tubes in the three-phase bridge arm of the inverter stage of the 3TSMC, thereby achieving the effect of improving the voltage transfer ratio.

[0015] In the overmodulation region I designed in this application, by increasing the virtual bus voltage u dcvir To increase the reference bus voltage u dcref To increase the voltage transfer ratio. In the overmodulation region II, on the basis of the reference bus voltage u dcrefOn the basis of maintaining the maximum value, by changing the amplitude of the output voltage of the inverter stage to increase the modulation ratio of the inverter stage, the voltage transfer ratio is increased. In overmodulation region III, for the reference bus voltage u dcref On the basis of maintaining the maximum value, by changing the amplitude and phase angle of the output voltage of the inverter stage to increase the modulation ratio of the inverter stage, the voltage transfer ratio is increased. On the basis of increasing the voltage transfer ratio, the voltage and current quality during overmodulation of 3TSMC can be effectively improved. Moreover, by using the pre-constructed first look-up table curve, second look-up table curve, and third look-up table curve, the calculation process can be simplified, the control efficiency can be improved, and the operation load can be reduced. Brief Description of the Drawings

[0016] Figure 1 is the topological structure diagram of the 3TSMC targeted by the method of this application.

[0017] Figure 2 is the relationship diagram of each voltage variable in overmodulation region I.

[0018] Figure 3 is the schematic diagram of the first look-up table curve.

[0019] Figure 4 is the schematic diagram of the voltage vector trajectory and output voltage waveform during minimum phase error overmodulation of the inverter stage in overmodulation region II.

[0020] Figure 5 is the schematic diagram of the second look-up table curve.

[0021] Figure 6 is the schematic diagram of the voltage vector trajectory and output voltage waveform during basic vector retention overmodulation of the inverter stage in overmodulation region III.

[0022] Figure 7 is the schematic diagram of the third look-up table curve.

[0023] Figure 8 is the schematic flow diagram of the 3TSMC control method of an embodiment of this application. Detailed Embodiments

[0024] The following further describes the detailed embodiments of this application with reference to the drawings.

[0025] This application discloses a 3TSMC control method for enhancing the maximum voltage transfer ratio. The topological structure of the three-phase harmonic injection dual-stage matrix converter (3TSMC) targeted by this method is as Figure 1 shown. The three-phase harmonic injection dual-stage matrix converter mainly includes a three-phase AC power supply, a rectifier stage three-phase bridge arm, three bidirectional switches, a harmonic injection control bridge arm, and an inverter stage three-phase bridge arm. As Figure 1 shown, the three-phase AC power supply provides three-phase input voltages u ia 、u iband u ic , the rectifier - stage three - phase bridge arm includes switching transistors S ap , S bp , S cp , S an , S bn , S cn , the three bidirectional switches include switching transistors S ay , S by , S cy , S ya , S yb , S yc ,, the harmonic - injection control bridge arm includes S yp , S yn , L y , the inverter - stage three - phase bridge arm includes S up , S vp , S wp , S un , S vn , S wn , the specific structure of the 3TSMC in this application will not be elaborated in detail.

[0026] The 3TSMC control method of this application does not need to change the original topological structure of the 3TSMC. By introducing a space - vector over - modulation strategy, the maximum voltage transfer ratio is improved. The main methods include:

[0027] Step 1, collect the three - phase input voltages u ia , u ib and u ic of the three - harmonic - injection bipolar matrix converter, and determine the given three - phase reference output voltages u oa , u ob and u oc .

[0028] After obtaining the three - phase input voltages u ia , u ib and u ic , the amplitude U im of the three - phase input voltages can be calculated. And by performing an abc / αβ coordinate transformation on the three - phase input voltages u ia , u ib and u ic , the αβ components of the three - phase input voltages are obtained, and the phase angle θ i of the three - phase input voltages can be calculated through a double - generalized second - order integrator phase - locked loop.

[0029] In addition, using the three - phase input voltages u ia , u ib and u ic , the DC - bus voltage u dc can also be calculated as:

[0030]

[0031] Among them, / / is the remainder operator.

[0032] Similarly, after obtaining the three-phase reference output voltages u oa 、u ob and u oc , the amplitude U om of the three-phase reference output voltages can be calculated. And for the three-phase reference output voltages u oa 、u ob and u oc , by performing the abc / αβ coordinate transformation, the αβ components of the three-phase reference output voltages are obtained, and through the double generalized second-order integrator phase-locked loop, the phase angle θ r of the three-phase reference output voltages can be calculated. Furthermore, according to the phase angle θ r of the three-phase reference output voltages, the sector where the output voltage vector is located and the angle by which the output voltage vector rotates in the sector can be determined. This angle is called the vector position angle θ and

[0033] Then, the required modulation ratio m can be calculated according to the following formula:

[0034]

[0035] After obtaining the modulation ratio m, two different methods are used to control the switching tubes in the rectifier three-phase bridge arm, the three bidirectional switches, and the inverter three-phase bridge arm in the 3TSMC:

[0036] For the rectifier three-phase bridge arm and the bidirectional switches, according to the phase angle θ i of the three-phase input voltages, the driving signals of the rectifier switching tubes and the driving signals of the bidirectional switches are determined to drive the rectifier switching tubes and the bidirectional switches in the 3TSMC. This part is the same as the conventional method. It includes controlling according to the control strategy corresponding to the sector where the phase angle θ i is located. The switching signal table is as follows:

[0037]

[0038] For the inverter three-phase bridge arm, using the space vector overmodulation strategy, the driving signals of the inverter switching tubes are obtained according to the required modulation ratio m to drive the inverter switching tubes in the 3TSMC. Directly using SVPWM can make the modulation ratio reach 0.866 at most. Therefore, in order to increase the maximum voltage transfer ratio, an overmodulation strategy design is required to enable the part where the modulation ratio m > 0.866 to be achieved, so as to achieve the effect of increasing the maximum voltage transfer ratio. This is the design focus of this application. Next, the design idea of the overmodulation region corresponding to the modulation ratio m > 0.866 is introduced as follows:

[0039] This application designs three overmodulation regions, corresponding to different modulation ratio ranges, which are introduced as follows:

[0040] I. Overmodulation Region I, corresponding to the range of modulation ratio 0.866 ≤ m < m1.

[0041] This overmodulation Region I increases the virtual bus voltage u dcvir to increase the reference bus voltage u dcref and thus increase the voltage transfer ratio until the virtual bus voltage u dcvir reaches the maximum value and the reference bus voltage u dcref also reaches the maximum value, at which point the voltage transfer ratio cannot be further increased by increasing the virtual bus voltage u dcvir . As a result, the modulation ratio is increased from 0.866 to m1 until the virtual bus voltage u dcvir can no longer be increased. Through actual calculations, it is determined that m1 = 0.955.

[0042] Introduce the reference angle of overmodulation Region I and use the reference angle α1 to calculate the upper limit u dcul of the virtual bus voltage as:

[0043]

[0044] Use the DC bus voltage u dc and the upper limit u dcul of the virtual bus voltage to synthesize the virtual bus voltage u dcvir as:

[0045]

[0046] Please refer to Figure 2 which shows the relationship diagram of the DC bus voltage u dc , the upper limit u dcul of the virtual bus voltage, and the virtual bus voltage u dcvir .

[0047] After that, find the average value of the virtual bus voltage u dcvir which is the reference bus voltage u dcref :

[0048]

[0049] Figure 2 The solid line in (b) of dcvir is the waveform of the synthesized virtual bus voltage u dcref , while the dashed line is the reference bus voltage u Figure 2 obtained by calculating the average value. It can be seen that the value of the reference angle α1 directly affects the upper limit udcul value, thus affecting the synthesized virtual bus voltage u dcvir , ultimately affecting the reference bus voltage u dcref , so it can be considered that the reference bus voltage u dcref is affected by the reference angle α1. Substituting the above formulas (2) to (4) into (5), the reference bus voltage u dcref and the relationship formula with the reference angle α1 is:

[0050]

[0051] According to the relationship of formula (6), by adjusting the reference angle α1, the corresponding reference bus voltage u dcref can be obtained, thus achieving the required modulation ratio. In order to simplify the operation and improve the control efficiency, a first look-up table curve can be pre-constructed based on formula (5), including: taking the reference bus voltage u dcref as the independent variable and the reference angle α1 as the dependent variable, constructing a first look-up table curve representing the relationship formula (6) between the reference bus voltage u dcref and the reference angle α1. The constructed first look-up table curve is as Figure 3 shown.

[0052] Second, overmodulation region II, corresponding to the interval where the modulation ratio m1 ≤ m < m2.

[0053] As described above, when the virtual bus voltage u dcvir increases to a certain extent, continuing to increase the virtual bus voltage u dcvir will not be able to continue to increase the reference bus voltage u dcref . Please combine with Figure 2 It can be seen that when the upper limit u of the virtual bus voltage dcul reaches and continues to increase the upper limit u of the virtual bus voltage dcul it will not be able to continue to increase the virtual bus voltage u dcvir and the reference bus voltage u dcref . At this time, it enters the overmodulation region II.

[0054] In the overmodulation region II, keep the reference bus voltage u dcref as the maximum value reached in the above overmodulation region I, then keep the phase angle of the inverter output voltage unchanged, and increase the voltage transmission ratio by changing the amplitude of the inverter output voltage, so that the modulation ratio is increased from m1 to m2 until continuing to change the amplitude of the inverter output voltage can no longer increase the voltage transmission ratio. At this time, through actual calculation, m2 = 1.002.

[0055] When performing minimum phase error overmodulation of the inverter in the overmodulation region II, The output voltage waveform within the interval is a piecewise function composed of four segments, and the expression is:

[0056]

[0057] where θ r is the phase angle of the three-phase reference output voltage, θ o is the phase angle of the actual output voltage, and α2 is the reference angle in overmodulation region II.

[0058] Please combine Figure 4 with the illustration of the voltage vector trajectory and the output voltage waveform during overmodulation with the minimum phase error of the inverter stage shown. Due to symmetry, the remaining parts can be determined similarly.

[0059] Since the phase angle of the output voltage of the inverter stage remains unchanged within overmodulation region II, there is a characteristic that the phase angle θ o of the actual output voltage = θ r within this overmodulation region II. From this, the modulation ratio m inv of the inverter stage can be calculated as:

[0060]

[0061] It can be seen from Equation (8) that changing the reference angle α2 can change the modulation ratio m inv of the inverter stage, so as to achieve the required modulation ratio. In order to simplify the operation and improve the control efficiency, a second look-up table curve can be pre-constructed based on Equation (8), including: taking the modulation ratio m inv of the inverter stage as the independent variable and the reference angle α2 as the dependent variable, constructing a second look-up table curve representing the relationship (8) between the modulation ratio m inv of the inverter stage and the reference angle α2. The constructed second look-up table curve is as shown in Figure 5 Figure.

[0062] III. Overmodulation region III, corresponding to the interval where the modulation ratio m ≥ m2.

[0063] As described above, when keeping the reference bus voltage u dcref at the maximum value and then only changing the amplitude of the output voltage of the inverter stage, the modulation ratio can be increased to m2 at most, and then it cannot be increased further. In order to further increase the modulation ratio, within overmodulation region III, when the reference bus voltage u dcrefOn the basis of maintaining the maximum value, the voltage transfer ratio is improved by changing the amplitude and phase angle of the output voltage of the inverter stage. At this time, the virtual bus voltage reaches the maximum, and the inverter stage is six-step modulation. The cost of this approach is more input and output waveform distortion compared with only changing the amplitude of the output voltage of the inverter stage. Limited by the physical constraints of the topology, the maximum modulation ratio that can be achieved in overmodulation region III is up to 1.053. That is, in practical applications, overmodulation region III corresponds to the interval of modulation ratio 1.002 ≤ m ≤ 1.053.

[0064] When performing overmodulation while maintaining the basic vectors of the inverter stage within overmodulation region III, The output voltage waveform within the interval is:

[0065]

[0066] Among them, α3 is the reference angle of overmodulation region III.

[0067] Please combine Figure 6 With the illustration of the voltage vector trajectory and output voltage waveform when maintaining overmodulation of the basic vectors of the inverter stage as shown. Due to symmetry, the remaining parts can be determined similarly.

[0068] Since the phase angle of the output voltage of the inverter stage within overmodulation region III will also change, at this time, the phase angle θ of the actual output voltage o No longer equals the phase angle θ of the three-phase reference output voltage r Instead, it satisfies the following relationship:

[0069]

[0070] Combining relationships (9) and (10) to construct the relationship between the modulation ratio m inv Of the inverter stage and the reference angle α3:

[0071]

[0072] It can be seen from equation (11) that changing the reference angle α3 can change the modulation ratio m inv Of the inverter stage, so as to achieve the required modulation ratio. In order to simplify the operation and improve the control efficiency, a third look-up table curve can also be pre-constructed based on formula (11), including: using the modulation ratio m inv Of the inverter stage as the independent variable and the reference angle α3 as the dependent variable, constructing a third look-up table curve representing the relationship (11) between the modulation ratio m inv Of the inverter stage and the reference angle α3. The constructed third look-up table curve is as shown in Figure 7 Shown.

[0073] Based on the design of the above three overmodulation regions, after calculating the required modulation ratio m according to formula (2), the process of obtaining the driving signals of the inverter stage switches is as follows. Please refer to Figure 8 :

[0074] (1) When the modulation ratio m < 0.866, according to the three-phase input voltages u ia , u ib and u ic and the vector position angle θ, determine the duty cycles d1 and d2 required for space vector modulation:

[0075]

[0076] This part is the same as the conventional method, and the required reference bus voltage u dcref and the required modulation ratio m inv of the inverter stage can be determined as:

[0077]

[0078] (2) When the modulation ratio 0.866 ≤ m < m1, it is determined that it is in overmodulation region I. The required reference bus voltage u dcref and the modulation ratio m inv of the inverter stage can be determined as:

[0079]

[0080] It can also be seen from the above formula that within overmodulation region I, the modulation ratio m inv of the inverter stage is fixed, and the modulation ratio m is mainly increased by changing the reference bus voltage u dcref .

[0081] Then, according to the required reference bus voltage u dcref , calculate the required virtual bus voltage u dcvir . One method is to calculate the required virtual bus voltage u dcvir according to formula (5). However, in order to simplify the calculation and improve the efficiency, based on the first look-up table curve shown in Figure 3 , in another embodiment, first query the first look-up table curve to directly determine the reference angle α1 corresponding to the calculated reference bus voltage u dcref , and then use the obtained reference angle α1 to calculate the upper limit u dcul of the virtual bus voltage according to formula (3), and combine formula (4) to obtain the virtual bus voltage u dcvir , thus simplifying the operation.

[0082] After obtaining the required virtual bus voltage u dcvir , the virtual bus voltage u can be based ondcvir The duty ratios d1 and d2 required for space vector modulation are determined in combination with the vector position angle θ as follows:

[0083]

[0084] (3) When the modulation ratio m1 ≤ m < m2, it is determined that it is in the overmodulation region II. According to the relationship between the voltage vector trajectory and the output voltage waveform during overmodulation with the minimum phase error of the inverter stage, the duty ratios required for space vector modulation are determined in combination with the modulation ratio m and the vector position angle θ. According to the above analysis of the overmodulation region II, the required reference bus voltage u dcref and the modulation ratio m of the inverter stage inv are as follows:

[0085]

[0086] It can also be seen from the above formula that within the overmodulation region II, the reference bus voltage u dcref remains unchanged, and the modulation ratio m of the inverter stage is mainly increased inv to increase the modulation ratio m and thus increase the voltage transfer ratio.

[0087] Within the overmodulation region II, the modulation ratio m of the inverter stage is increased by changing the amplitude of the output voltage of the inverter stage inv . As analyzed above, the modulation ratio m of the inverter stage inv is related to the reference angle α2. Therefore, first, according to the relational formula between the modulation ratio m of the inverter stage inv and the reference angle α2, the reference angle α2 required to achieve the required modulation ratio m of the inverter stage inv is determined.

[0088] One method is that the required reference angle α2 can be calculated according to the above formula (8). However, since formula (8) involves complex operations, in another embodiment, when the second look-up table curve as shown in Figure 5 is pre-constructed, the reference angle α2 corresponding to the calculated modulation ratio m of the inverter stage inv can be directly determined by querying the second look-up table curve.

[0089] Then, the duty ratios required for space vector modulation are determined in combination with the reference angle α2, the modulation ratio m, and the vector position angle θ, including:

[0090] First, d1′ and d2′, which are intermediate variables of two duty ratios, are determined according to the modulation ratio m and the vector position angle θ. d1′ and d2′ are two intermediate variables of the duty ratios.

[0091] When , the duty ratios d1 and d2 required for space vector modulation are Otherwise, the duty ratios d1 and d2 required for space vector modulation are directly determined as

[0092] (4) When the modulation ratio m ≥ m2, it is determined to be in the overmodulation zone III. According to the relationship between the voltage vector trajectory and the output voltage waveform when the inverter basic vector maintains overmodulation, the duty cycle required for space vector modulation is determined in combination with the modulation ratio m and the vector position angle θ. According to the above analysis of the overmodulation zone II, the required reference bus voltage u can be determined in this case. dcref and inverter modulation ratio m inv It is also shown in the above formula (16).

[0093] It can also be seen from the above formula (16) that in the overmodulation region III, the reference bus voltage u dcref unchanged, mainly by increasing the inverter modulation ratio m inv Increasing the modulation ratio m can improve the voltage transfer ratio.

[0094] However, unlike overmodulation region II, overmodulation region III increases the inverter modulation ratio m by changing the amplitude and phase angle of the inverter output voltage. inv As can be seen from the above analysis, the inverter stage modulation ratio m inv It is related to the reference angle α3, so firstly according to the inverter level modulation ratio m inv The relationship between the reference angle α3 is used to determine the required inverter modulation ratio m. inv Required reference angle α3.

[0095] One approach is to calculate the required reference angle α3 according to the above formula (11). However, since formula (11) involves complex calculations, in another embodiment, when the following formula is pre-constructed: Figure 7 After the third lookup table curve is shown, the inverter level modulation ratio m obtained by calculating can be determined by directly looking up the third lookup table curve. inv The corresponding reference angle is α3.

[0096] Then, the duty cycle required for space vector modulation is determined based on the obtained reference angle α3 combined with the modulation ratio m and the vector position angle θ. This includes determining based on the reference angle α3 combined with the modulation ratio m and the vector position angle θ:

[0097]

[0098] when The duty cycles d1 and d2 required for space vector modulation are determined as When 0<θ≤α3, the duty ratios d1 and d2 required for space vector modulation are determined as follows: Otherwise, the duty cycles d1 and d2 required for space vector modulation are determined as

[0099] Regardless of which of the above situations is the case, after determining the duty ratios d1 and d2 required for space vector modulation, pulse width modulation can be performed according to the duty ratios d1 and d2 required for space vector modulation to obtain the inverter-stage switch tube drive signal, and then the switch tubes in the inverter-stage three-phase bridge arm of the 3TSMC are driven according to the inverter-stage switch tube drive signal.

[0100] The above is only a preferred embodiment of the present application, and the present application is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present application should be considered to be included in the protection scope of the present application.

Claims

1. A 3TSMC control method for improving the maximum voltage transfer ratio, characterized in that The 3TSMC control method includes: Collect the three-phase input voltages of the three-harmonic injection bipolar matrix converter and calculate the amplitude U of the three-phase input voltages im , determine the amplitude U of the three-phase reference output voltages according to the given three-phase reference output voltages om and the phase angle θ r , and calculate the modulation ratio and the vector position angle of the output voltage vector in the sector where, / / is the modulo operator; When the modulation ratio m < 0.866, determine the duty cycle required for space vector modulation according to the three-phase input voltage and the vector position angle θ; When the modulation ratio 0.866 ≤ m < m1, it is determined that the overmodulation region I is entered, and the reference bus voltage is determined as and the virtual bus voltage u is calculated dcvir . According to the virtual bus voltage u dcvir , the duty cycle required for space vector modulation is determined in combination with the vector position angle θ; When the modulation ratio m1 ≤ m < m2, it is determined that it is in the overmodulation region II. According to the relationship between the voltage vector trajectory and the output voltage waveform during overmodulation with the minimum phase error of the inverter stage, combine the modulation ratio m and the vector position angle θ to determine the duty cycle required for space vector modulation; When the modulation ratio m ≥ m2, it is determined that it is in the overmodulation region III. According to the relationship between the voltage vector trajectory and the output voltage waveform during overmodulation with the basic vector of the inverter stage remaining unchanged, combine the modulation ratio m and the vector position angle θ to determine the duty cycle required for space vector modulation; According to the phase angle θ of the three-phase input voltage i Determine the driving signals of the rectifier-stage switching transistors and the bidirectional switch to drive the rectifier-stage switching transistors and the bidirectional switch in the 3TSMC, perform pulse-width modulation according to the duty cycle required by space vector modulation, and obtain the driving signals of the inverter-stage switching transistors to drive the switching transistors in the three-phase bridge arm of the inverter stage of the 3TSMC; Among them, in overmodulation region I, by increasing the virtual bus voltage u dcvir to increase the reference bus voltage u dcref to increase the voltage transfer ratio. In overmodulation region II, on the basis of keeping the maximum value of the reference bus voltage u dcref by changing the amplitude of the inverter stage output voltage to increase the modulation ratio of the inverter stage to increase the voltage transfer ratio. In overmodulation region III, on the basis of keeping the maximum value of the reference bus voltage u dcref by changing the amplitude and phase angle of the inverter stage output voltage to increase the modulation ratio of the inverter stage to increase the voltage transfer ratio.

2. The 3TSMC control method according to claim 1, wherein Calculate the virtual bus voltage u dcvir And determining the duty cycle required for space vector modulation includes: Based on the relationship, the virtual bus voltage u dcref is calculated according to the reference bus voltage u dcvir , and the duty cycles d1 and d2 required for space vector modulation are determined as follows: Among them, u dc is the DC bus voltage calculated from the three-phase input voltage.

3. The 3TSMC control method according to claim 2, wherein The 3TSMC control method includes: Reference angle using overmodulation region I Construct the virtual bus voltage u dcvir The expression is as follows: where u dcul is the upper limit of the virtual bus voltage related to the reference angle α1 and: Substitute the expression of the virtual bus voltage u dcvir into the relationship of to obtain the relationship between the reference bus voltage u dcref and the reference angle α1 as follows: Taking the reference bus voltage u dcref as the independent variable and the reference angle α1 as the dependent variable, a first look-up table curve representing the relationship between the reference bus voltage u dcref and the reference angle α1 is constructed; Calculate the virtual bus voltage u dcvir It also includes: Query the first look-up curve to determine the reference bus voltage u dcref The corresponding reference angle α1, and use the obtained reference angle α1 to calculate to obtain the upper limit u of the virtual bus voltage dcul , and combine it with to obtain the virtual bus voltage u dcvir .

4. The 3TSMC control method according to claim 1, characterized in that, The 3TSMC control method further includes: Determine that when performing overmodulation with the minimum phase error of the inverter stage in overmodulation region II, The output voltage waveform within the interval is as follows: where θ r is the phase angle of the three-phase reference output voltage, θ o is the phase angle of the actual output voltage, and α2 is the reference angle of overmodulation region II; Combined with the phase angle θ of the actual output voltage in overmodulation region II o = θ r Characteristics, construct the relationship between the modulation ratio m inv of the inverter stage and the reference angle α2; When the modulation ratio m1 ≤ m < m2, combining the modulation ratio m and the vector position angle θ to determine the duty cycle required for space vector modulation includes: Determine the modulation ratio of the inverter stage according to the modulation ratio m Combine the modulation ratio m of the inverter stage inv Determine the reference angle α2 based on the relational expression with the reference angle α2, and determine the duty cycle required for space vector modulation according to the reference angle α2, in combination with the modulation ratio m and the vector position angle θ.

5. The 3TSMC control method according to claim 4, characterized in that Determining the duty cycle required for space vector modulation according to the reference angle α2 by combining the modulation ratio m and the vector position angle θ includes: Determine according to the modulation ratio m and the vector position angle θ When the duty cycles d1 and d2 required for space vector modulation are determined as Otherwise, the duty cycles d1 and d2 required for space vector modulation are directly determined as 6. The 3TSMC control method according to claim 4, characterized in that, The 3TSMC control method further includes: Construct the modulation ratio m of the inverter stage inv The relational expression with the reference angle α2 is as follows: Taking the modulation ratio m of the inverter stage inv as the independent variable and the reference angle α2 as the dependent variable, construct a second look-up table curve representing the relationship between the modulation ratio m inv of the inverter stage and the reference angle α2; The determining of the reference angle α2 includes: querying the second look-up curve table to determine the reference angle α2 corresponding to the calculated modulation ratio m of the inverter stage inv level.

7. The 3TSMC control method according to claim 1, characterized in that, The 3TSMC control method further includes: Determine that when the basic vector of the inverter stage maintains overmodulation in the overmodulation region III, The output voltage waveform within the interval is as follows: where, θ r is the phase angle of the three-phase reference output voltage, θ o is the phase angle of the actual output voltage, and α3 is the reference angle of overmodulation region III; Combined with the phase angle θ of the actual output voltage in overmodulation region III o and the phase angle θ of the three-phase reference output voltage r to construct the modulation ratio m of the inverter stage inv Relationship formula with the reference angle α3: When the modulation ratio m ≥ m2, combining the modulation ratio m and the vector position angle θ to determine the duty cycle required for space vector modulation includes: Determine the modulation ratio of the inverter stage according to the modulation ratio m Combine the modulation ratio m of the inverter stage inv Determine the reference angle α3 based on the relationship with the reference angle α3, and determine the duty cycle required for space vector modulation according to the reference angle α3 in combination with the modulation ratio m and the vector position angle θ.

8. The 3TSMC control method according to claim 7, characterized in that, Determining the duty cycle required for space vector modulation according to the reference angle α3 by combining the modulation ratio m and the vector position angle θ includes: Determine according to the reference angle α3 by combining the modulation ratio m and the vector position angle θ: When the duty ratios d1 and d2 required for space vector modulation are determined as When 0 < θ ≤ α3, the duty ratios d1 and d2 required for space vector modulation are determined as Otherwise, the duty ratios d1 and d2 required for space vector modulation are determined as 9. The 3TSMC control method according to claim 7, wherein The 3TSMC control method further includes: Construct the modulation ratio m of the inverter stage inv The relational expression with the reference angle α3 is as follows: With the modulation ratio m of the inverter stage inv as the independent variable and the reference angle α3 as the dependent variable, construct a third look-up table curve representing the relationship between the modulation ratio m of the inverter stage inv and the reference angle α3; Combined with the modulation ratio m of the inverter stage inv Determining the reference angle α3 based on the relational expression with the reference angle α3 includes: Query the third look-up table curve to determine the reference angle α3 corresponding to the calculated modulation ratio m of the inverter stage. inv ​ 10. The 3TSMC control method according to claim 1, wherein m1 = 0.955, m2 = 1.002.

Images