Modulation method and control system of suspension capacitance type double-inverter motor

Abstract

The invention relates to the technical field of electrics, and provides a modulation method and a control system of a suspension capacitance type double-inverter motor, the modulation of inverters is carried out based on an SVPWM (Space Vector Pulse Width Modulation) algorithm, and each divided modulation area at least comprises a first type vector with a redundant switch state. All modulation areas can effectively modulate the voltage of the floating capacitor; and after the target modulation region is obtained according to the reference vector, when only one first type of vector is included in three target basic vectors corresponding to the target modulation region, the action time of the corresponding first type of vector is increased, so that the voltage of the suspension capacitor at the auxiliary inverter side follows the preset capacitor reference voltage. According to the invention, the divided modulation areas comprise the first type of vectors, so that the voltage modulation effect of each modulation area on the suspension capacitor can be effectively improved, the voltage stability of the suspension capacitor is improved, and the working reliability of the suspension capacitor type dual-inverter motor is further improved.

Description

Technical Field

[0001] The present invention relates to the field of electrical technology, and in particular to a modulation method and control system for a suspended capacitor type dual inverter motor. Background Art

[0002] Multilevel inverters are widely used in motor drives due to their low harmonics and higher voltage tolerance. They are attracting significant attention in transportation electrification applications. Dual inverters are a popular multilevel topology, offering superior fault tolerance compared to traditional multilevel inverters due to their inherent redundant switching states.

[0003] like Figure 1 As shown, the main inverter of the suspended capacitor type dual inverter motor is powered by a DC power supply, and the auxiliary inverter is powered by a capacitor, which is not affected by zero-sequence current and only requires one isolated power supply, thereby improving the reliability and power density of the system.

[0004] However, in the traditional space vector pulse width modulation (SVPWM), Figure 2 and Figure 3 As shown in the figure, each sector of the voltage space vector of the suspended capacitor type dual inverter motor is divided into 9 modulation areas in the shape of equilateral triangles, and each node in the modulation area corresponds to a basic vector. Among the 10 basic vectors in a sector, there are first-type vectors that can be redundantly provided by multiple switching states of the inverter, which have strong adjustable capabilities for the charging and discharging currents of the capacitor; and second-type vectors that can only be provided by a single switching state of the inverter, which have low adjustable capabilities for the charging and discharging currents of the capacitor. Among them, some modulation areas are dominated by the second-type vectors. When the voltage reference vector is in the modulation area dominated by the second-type vector, the control effect of the capacitor voltage is difficult to achieve as expected, reducing the reliability of the system. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a modulation method and control system for a suspended capacitor type dual inverter motor to solve the problem in the prior art that the control effect of the suspended capacitor type dual inverter in some modulation areas is difficult to achieve the expected and the reliability of the system is insufficient.

[0006] In one aspect, the present invention provides a modulation method for a suspended capacitor dual-inverter motor, comprising: Collecting the operating data of the target motor to obtain a reference vector based on SVPWM, and combining the preset identification conditions and modulation area division rules to obtain the target modulation area where the reference vector is currently located; Obtaining a target basic vector according to the target modulation area, and obtaining an action time of each target basic vector in combination with the reference vector, so that a composite vector of an actual action vector of each target basic vector is consistent with the reference vector; Obtaining the duration of each switching state of the target dual inverter according to the final action time of each target basic vector, so that the space vector of the target dual inverter is consistent with the space vector of the target motor; Wherein, each modulation area corresponding to the preset modulation area division rule includes at least one first type vector, and the first type vector has a redundant switch state; When the three target basic vectors corresponding to the target modulation area include only one first-type vector, the action time of the corresponding first-type vector is increased to make the voltage of the auxiliary inverter side floating capacitor of the target dual inverter follow the preset capacitor reference voltage.

[0007] Optionally, the modulation area division rule includes: Based on the equilateral triangles of each sector, the center point, the zero vector vertex, the two non-zero vector vertices, and the trisection points on each side are used as the vertices of the modulation area. The two diamond areas from the center point to the two non-zero vector vertices are divided into two obtuse-angled triangle modulation areas, and the other areas are divided into five equilateral triangle modulation areas of equal size.

[0008] Optionally, when the three target basic vectors corresponding to the target modulation area include only one first-type vector, the step of increasing the action time of the corresponding first-type vector is obtained according to the following calculation formula: ; ; ; ; in, 、 and are the original action times of the first second-category vector, the second second-category vector, and the first-category vector obtained based on the volt-second balance, respectively. The second-category vector is generated by only a single switching state. is the correction factor, 、 and are the corrected action times of the first second-category vector, the second second-category vector, and the first-category vector, respectively. is the current voltage of the floating capacitor on the auxiliary inverter side, is the capacitance reference voltage of the floating capacitor, C is the capacitance value of the floating capacitor, 、 and The first second-class vector, the second second-class vector, and the first-class vector correspond to the current flowing through the suspension capacitor.

[0009] Optionally, the suspended capacitor includes a non-electrolytic capacitor.

[0010] Another aspect of the present invention provides a control system for a suspended capacitor type dual inverter motor, comprising: A first processing module is configured to collect operating data of a target motor to obtain a reference vector based on SVPWM, and to obtain a target modulation region in which the reference vector is currently located by combining preset identification conditions and modulation region division rules; a second processing module, configured to obtain a target basic vector according to the target modulation area, and obtain an action time of each target basic vector in combination with the reference vector, so that a composite vector of an actual action vector of each target basic vector is consistent with the reference vector; a third processing module, configured to obtain a duration of each switching state of the target dual inverter according to a final action time of each target basic vector, so that the space vector of the target dual inverter is consistent with the space vector of the target motor; Wherein, each modulation area corresponding to the preset modulation area division rule includes at least one first type vector, and the first type vector has a redundant switch state; The second processing module is also used to: when only one first-type vector is included in the three target basic vectors corresponding to the target modulation area, increase the action time of the corresponding first-type vector so that the voltage of the auxiliary inverter side floating capacitor of the target dual inverter follows the preset capacitor reference voltage.

[0011] The modulation method of the suspended capacitor type dual inverter motor provided by the present invention is based on the SVPWM algorithm, and the divided modulation areas all include at least one first-class vector with redundant switching state, so that all modulation areas can effectively modulate the voltage of the suspended capacitor; after obtaining the target modulation area according to the reference vector, when only one first-class vector is included in the three target basic vectors corresponding to the target modulation area, the action time of the corresponding first-class vector is increased so that the voltage of the suspended capacitor on the auxiliary inverter side follows the preset capacitor reference voltage, thereby improving the voltage stability of the suspended capacitor and thereby improving the working reliability of the suspended capacitor type dual inverter motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The topological structure diagram of the suspended capacitor dual inverter motor; Figure 2 Schematic diagram of space vector synthesis of suspended capacitor dual inverter motor; Figure 3 A schematic diagram of the partitioning of the space vector modulation interval of the floating capacitor type dual inverter motor in the prior art; Figure 4 This is a main flow chart of a modulation method for a suspended capacitor dual inverter motor according to an embodiment of the present invention; Figure 5 Schematic diagram of the partitioning of the space vector modulation interval of the modulation method of the suspended capacitor type dual inverter motor according to an embodiment of the present invention; Figure 6 A test diagram of duty ratios of some basic vectors in modulation of a floating capacitor dual-inverter motor according to an embodiment of the present invention; Figure 7 The capacitor voltage modulation waveforms of the modulation method of the floating capacitor type dual inverter motor according to the embodiment of the present invention and the conventional method under the first condition are shown; Figure 8 The capacitor voltage modulation waveforms of the modulation method of the suspended capacitor type dual inverter motor under the second condition of the embodiment of the present invention and the traditional method are shown; Figure 9 1 is a capacitor voltage modulation waveform of the modulation method of the floating capacitor type dual inverter motor according to an embodiment of the present invention and the conventional method under the third condition; Figure 10 1 is a capacitor voltage modulation waveform of the modulation method of the floating capacitor type dual inverter motor according to an embodiment of the present invention and the conventional method under the fourth condition; Figure 11 1. A peak-to-peak test waveform diagram of a capacitor voltage modulation waveform under the fifth condition of a modulation method for a suspended capacitor dual-inverter motor according to an embodiment of the present invention and a conventional method; Figure 12 1. A waveform diagram showing a capacitor voltage modulation time test under the fifth condition for a modulation method of a suspended capacitor dual inverter motor according to an embodiment of the present invention and a conventional method; Figure 13 1. A peak-to-peak test waveform diagram of a capacitor voltage modulation waveform under the sixth condition of a modulation method for a suspended capacitor dual-inverter motor according to an embodiment of the present invention and a conventional method; Figure 14 1 is a capacitor voltage modulation time test waveform diagram of the modulation method of the floating capacitor type dual inverter motor according to an embodiment of the present invention and the traditional method under the sixth condition.

[0013] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0014] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The drawings illustrate several embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present invention.

[0015] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0017] like Figure 1 、 Figure 2 and Figure 3 As shown in the figure, the floating capacitor type dual inverter motor is mainly composed of a main inverter, an auxiliary inverter and an open-winding motor. The current of the motor winding is jointly controlled by the main inverter and the auxiliary inverter. The power supply on the main inverter side is a DC source, and the power supply on the auxiliary inverter side is provided by the floating capacitor FC. The voltage ratio of the DC source to the voltage of the floating capacitor FC is 2:1.

[0018] In SVPWN modulation, 1 indicates that the upper bridge arm is in the on state and the lower bridge arm is in the off state, and 0 indicates that the upper bridge arm is in the off state and the lower bridge arm is in the on state. The switching state combination of the three-phase bridge arm can be represented by a three-bit binary number. Each switching state can provide a space vector. One inverter can provide eight space vectors from 0 to 7. Dual inverters can synthesize multiple space vectors. In a single sector, there are ten preset basic vectors.

[0019] in, It is a zero vector and can be redundantly provided by the four switching states 07', 00', 70' and 77'. Among them, the 0 in 07' indicates that the switching state of the three-phase bridge arm of the main inverter is 000, and 7' indicates that the switching state of the three-phase bridge arm of the auxiliary inverter is 111. At this time, no current flows through the floating capacitor FC. The other basic vectors are non-zero vectors. In the corresponding switching states, current flows through the floating capacitor FC. 、 、 The currents flowing through the floating capacitor FC are phase A, phase B and phase C of the three-phase current, respectively. The symbol “-” indicates that the direction of the current is toward the negative plate of the floating capacitor FC, and the floating capacitor FC is in a discharged state.

[0020] In the prior art, a single sector is divided into 9 modulation areas (①~⑨), each modulation area is an equilateral triangle. In some modulation areas, the basic vectors involved in the modulation are all second-class vectors, which can only provide one current or no current. For example, among the three basic vectors in modulation area ⑤, the basic vector and Only one current can be provided, basic vector No current can be supplied.

[0021] When the reference vector is in the modulation region ⑤, the basic vector It can only provide the discharge current of phase A, basic vector Only the charging current of phase C can be provided, so that in the voltage balancing modulation of the floating capacitor, the current of phase A and the current of phase C need to frequently participate in the voltage balancing modulation of the floating capacitor. However, the current of phase A and the current of phase C have a phase difference of 120°, and the current size difference is large. The charging and discharging speeds are different, which will cause the voltage ripple of the floating capacitor to increase and the balancing effect to be poor.

[0022] In order to solve the problem that in the prior art SVPWM modulation, there is a modulation area in which only the second type of vector participates, when the reference vector is in this type of modulation area, the voltage ripple of the floating capacitor is large, the balancing effect is poor, and the system reliability is reduced.

[0023] The present invention provides a modulation method for a suspended capacitor type dual inverter motor, such as Figure 4 Shown, including: Step S01: collecting operating data of a target motor to obtain a reference vector based on SVPWM, and combining preset identification conditions and modulation region division rules to obtain a target modulation region where the reference vector is currently located; Step S02: obtaining a target basic vector according to the target modulation area, and obtaining an action time of each target basic vector in combination with the reference vector, so that a composite vector of an actual action vector of each target basic vector is consistent with the reference vector; Step S03: obtaining the duration of each switching state of the target dual inverter according to the final action time of each target basic vector, so that the space vector of the target dual inverter is consistent with the space vector of the target motor; Wherein, each modulation area corresponding to the preset modulation area division rule includes at least one first type vector, and the first type vector has a redundant switch state; When the three target basic vectors corresponding to the target modulation area include only one first-type vector, the action time of the corresponding first-type vector is increased to make the voltage of the auxiliary inverter side floating capacitor of the target dual inverter follow the preset capacitor reference voltage.

[0024] Specifically, if Figure 5 As shown, the modulation area division rules of this embodiment include: Based on the equilateral triangle of each sector, with the center point ( corresponding points), zero vector vertices ( corresponding points), two non-zero vector vertices ( and Corresponding points), the three-divided points on each side are used as modulation area vertices, and the two rhombus areas from the center point to the two non-zero vector vertices are divided into two obtuse triangle modulation areas, and the other areas are divided into five equilateral triangle modulation areas of equal size.

[0025] Among them, the comparison Figure 3 and Figure 5 In the modulation area divided in this embodiment, the modulation areas ⑤, ⑥, ⑧, and ⑨ are re-divided and associated with the basic vectors in the first type of vectors. , basic vector The currents provided by the two switching states are both B-phase currents, and its switching state 23' can provide charging current, and the switching state 16' can provide discharging current. The charging and discharging speeds are consistent, which can reduce the ripple introduced during the voltage modulation process of the floating capacitor FC, improve the voltage stability of the floating capacitor FC, and thus improve the reliability of the floating capacitor type dual inverter motor.

[0026] To further improve the voltage stability of the suspended capacitor FC, in this embodiment, when the three target basic vectors corresponding to the target modulation area include only one first-type vector, the step of increasing the action time of the corresponding first-type vector is obtained according to the following calculation formula: ; ; ; ; in, 、 and are the original action times of the first second-category vector, the second second-category vector, and the first-category vector obtained based on the volt-second balance, respectively. The second-category vector is generated by only a single switching state. is the correction coefficient, which is calculated according to the fourth formula. 、 and are the corrected action times of the first second-category vector, the second second-category vector, and the first-category vector, respectively. is the current voltage of the floating capacitor on the auxiliary inverter side, is the capacitance reference voltage of the floating capacitor (determined by the configuration of the floating capacitor type dual inverter motor, in this embodiment, it is 1 / 2 of the DC power supply voltage on the main inverter side), C is the capacitance value of the floating capacitor, 、 and The first second-class vector, the second second-class vector, and the first-class vector correspond to the current flowing through the suspension capacitor.

[0027] like Figure 6 As shown, it is the basic vector after adjustment The duty cycle of the y-axis is the reference vector angle, which ranges from 0 to π / 3, and the x-axis is the modulation ratio, which ranges from 0.6 to 1. The corresponding modulation areas include ⑤, ⑥, ⑧, and ⑨. Figure 6 It can be seen that after re-dividing the modulation area, the action time of the first type of vector can be increased, thereby enhancing the capacitor voltage regulation capability.

[0028] Please refer to further Figure 7 、 Figure 8 、 Figure 9 and Figure 10 , which shows the simulation results of the capacitance voltage ripple of the suspended capacitor FC, wherein (a) is the modulation ripple under the traditional method, and (b) is the modulation ripple under the modulation method of this embodiment, wherein, Figure 7 The power factor PF=0.3, modulation ratio MI=0.89, Figure 8 The power factor PF=0.3, modulation ratio MI=1, Figure 9 The power factor PF=0.9, modulation ratio MI=0.77, Figure 10 The power factor PF=0.9 and the modulation ratio MI=0.79.

[0029] According to the simulation results, under different power factors, the modulation scheme of this embodiment can effectively reduce the voltage ripple of the floating capacitor FC, and when the power factor PF=0.3, the modulation ratio MI=1, and the power factor PF=0.9, the modulation ratio MI=0.79, the traditional method cannot be modulated, that is, the modulation method of this embodiment can effectively improve the voltage stability of the floating capacitor.

[0030] The capacitor voltage ripple is reduced, making it easier to configure a floating capacitor with a smaller capacitance. For example, in this embodiment, the floating capacitor includes a non-electrolytic capacitor.

[0031] Please refer to further Figure 11 、 Figure 12 、 Figure 13 and Figure 14 , which shows the simulation results of the peak-to-peak value of the capacitor voltage of the floating capacitor FC and the corresponding adjustment time, where (a) is the traditional method and (b) is the modulation method of this embodiment.

[0032] in, Figure 11 and Figure 12 The power factor PF=0.3, modulation ratio MI=0.8, Figure 13 and Figure 14 The power factor PF=0.9, modulation ratio MI=0.77, Figure 11 and Figure 13 is the peak-to-peak value of the capacitor voltage, Figure 12 and Figure 14 To adjust the time.

[0033] according to Figure 11 、 Figure 12 、 Figure 13 and Figure 14 It can be seen that when PF = 0.3 and MI = 0.8, the modulation method of the present invention can reduce capacitor voltage ripple by 44.1%, reduce adjustment time from 9.4ms to 4.6ms, and increase adjustment speed by 51.1%. When PF = 0.9 and MI = 0.77, the modulation method of the present invention can reduce capacitor voltage ripple by 53.8%, reduce adjustment time from 0.05s to 0.01s, and increase adjustment speed by 80%. In other words, the modulation method of this embodiment can effectively reduce capacitor voltage ripple, increase adjustment speed, and improve system reliability.

[0034] The present invention also provides a control system for a suspended capacitor type dual inverter motor, comprising: A first processing module is configured to collect operating data of a target motor to obtain a reference vector based on SVPWM, and to obtain a target modulation region in which the reference vector is currently located by combining preset identification conditions and modulation region division rules; a second processing module, configured to obtain a target basic vector according to the target modulation area, and obtain an action time of each target basic vector in combination with the reference vector, so that a composite vector of an actual action vector of each target basic vector is consistent with the reference vector; a third processing module, configured to obtain a duration of each switching state of the target dual inverter according to a final action time of each target basic vector, so that the space vector of the target dual inverter is consistent with the space vector of the target motor; Wherein, each modulation area corresponding to the preset modulation area division rule includes at least one first type vector, and the first type vector has a redundant switch state; The second processing module is also used to: when only one first-type vector is included in the three target basic vectors corresponding to the target modulation area, increase the action time of the corresponding first-type vector so that the voltage of the auxiliary inverter side floating capacitor of the target dual inverter follows the preset capacitor reference voltage.

[0035] The modulation method and control system of the suspended capacitor type dual-inverter motor provided by the present invention redistribute the modulation area of ​​SVPWM, so that each modulation area includes at least one first-class vector with redundant switching state, so that all modulation areas can effectively modulate the voltage of the suspended capacitor; after obtaining the target modulation area according to the reference vector, when only one first-class vector is included in the three target basic vectors corresponding to the target modulation area, the action time of the corresponding first-class vector is increased, which can effectively reduce the voltage ripple of the suspended capacitor, increase the modulatable range, improve the voltage stability of the suspended capacitor, and thus improve the reliability of the suspended capacitor type dual-inverter motor.

[0036] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0037] The above-described embodiments merely represent several specific implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of protection of the present invention. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A modulation method for a suspended capacitor type dual inverter motor, characterized in that: include: Collecting the operating data of the target motor to obtain a reference vector based on SVPWM, and combining the preset identification conditions and modulation area division rules to obtain the target modulation area where the reference vector is currently located; Obtaining a target basic vector according to the target modulation area, and obtaining an action time of each target basic vector in combination with the reference vector, so that a composite vector of an actual action vector of each target basic vector is consistent with the reference vector; Obtaining the duration of each switching state of the target dual inverter according to the final action time of each target basic vector, so that the space vector of the target dual inverter is consistent with the space vector of the target motor; Wherein, each modulation area corresponding to the preset modulation area division rule includes at least one first type vector, and the first type vector has a redundant switch state; When the three target basic vectors corresponding to the target modulation area include only one first-type vector, the action time of the corresponding first-type vector is increased to make the voltage of the auxiliary inverter side floating capacitor of the target dual inverter follow the preset capacitor reference voltage.

2. The modulation method of the floating capacitor type dual inverter motor according to claim 1, characterized in that: The modulation area division rules include: Based on the equilateral triangles of each sector, the center point, the zero vector vertex, the two non-zero vector vertices, and the trisection points on each side are used as the vertices of the modulation area. The two diamond areas from the center point to the two non-zero vector vertices are divided into two obtuse-angled triangle modulation areas, and the other areas are divided into five equilateral triangle modulation areas of equal size.

3. The modulation method of the floating capacitor type dual inverter motor according to claim 2, characterized in that: When the three target basic vectors corresponding to the target modulation area include only one first-type vector, the step of increasing the action time of the corresponding first-type vector is obtained according to the following calculation formula: ； ； ； ； in, 、 and are the original action times of the first second-category vector, the second second-category vector, and the first-category vector obtained based on the volt-second balance, respectively. The second-category vector is generated by only a single switching state. is the correction factor, 、 and are the corrected action times of the first second-category vector, the second second-category vector, and the first-category vector, respectively. is the current voltage of the floating capacitor on the auxiliary inverter side, is the capacitance reference voltage of the floating capacitor, C is the capacitance value of the floating capacitor, 、 and The first second-class vector, the second second-class vector, and the first-class vector correspond to the current flowing through the suspension capacitor.

4. The modulation method of the floating capacitor type dual inverter motor according to claim 3, characterized in that: The suspended capacitor includes a non-electrolytic capacitor.

5. A control system for a floating capacitor type dual inverter motor, characterized in that: include: A first processing module is configured to collect operating data of a target motor to obtain a reference vector based on SVPWM, and to obtain a target modulation region in which the reference vector is currently located by combining preset identification conditions and modulation region division rules; a second processing module, configured to obtain a target basic vector according to the target modulation area, and obtain an action time of each target basic vector in combination with the reference vector, so that a composite vector of an actual action vector of each target basic vector is consistent with the reference vector; a third processing module, configured to obtain a duration of each switching state of the target dual inverter according to a final action time of each target basic vector, so that the space vector of the target dual inverter is consistent with the space vector of the target motor; Wherein, each modulation area corresponding to the preset modulation area division rule includes at least one first type vector, and the first type vector has a redundant switch state; The second processing module is also used to: when only one first-type vector is included in the three target basic vectors corresponding to the target modulation area, increase the action time of the corresponding first-type vector so that the voltage of the auxiliary inverter side floating capacitor of the target dual inverter follows the preset capacitor reference voltage.

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