A five-phase motor pulse width modulation method and a five-phase motor system

Abstract

The application provides a five-phase motor pulse width modulation method and a five-phase motor system. The method comprises the following steps: obtaining a reference voltage vector, wherein the reference voltage vector comprises a fundamental reference voltage vector and a third harmonic reference voltage vector; determining a sector in which the fundamental reference voltage vector is located in a fundamental space vector sector division diagram according to the fundamental reference voltage vector; selecting a plurality of basic voltage vector combinations according to the sector in which the fundamental reference voltage vector is located; respectively performing analog modulation on the reference voltage vector by using the plurality of basic voltage vector combinations to obtain a plurality of groups of modulation time; selecting a unique group of feasible solutions from the plurality of groups of modulation time; and selecting a basic voltage vector combination corresponding to the feasible solution to modulate the five-phase motor. According to the scheme, a third harmonic voltage can be modulated, and the third harmonic voltage can be injected under a rated working condition to increase the modulation ratio of the fundamental voltage vector.

Description

Technical Field

[0001] This invention belongs to the field of motor control technology, and specifically relates to a pulse width modulation method for a five-phase motor and a five-phase motor system. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) have been widely used in aerospace, industrial automation, and electric vehicles due to their advantages such as high power density, high efficiency, and high torque density. While three-phase PMSMs are currently the primary industrial application, five-phase PMSMs are gradually becoming a research hotspot due to their superior performance. This is because the angle between adjacent vectors in the vector pulse width modulation (PWM) of a five-phase motor is 36°, compared to 60° in a three-phase motor. Therefore, five-phase PMSMs exhibit less torque ripple during modulation. Furthermore, they also possess greater energy density.

[0003] In five-phase permanent magnet synchronous motors, existing space vector pulse width modulation (SVM) techniques require modulating the motor's third harmonic by sacrificing the modulation ratio of the bus voltage. When the motor operates under high load and high power, this method severely impacts the modulation ratio of the bus voltage. Summary of the Invention

[0004] The purpose of the embodiments in this specification is to provide a pulse width modulation method for a five-phase motor and a five-phase motor system.

[0005] To solve the above-mentioned technical problems, the embodiments of this application are implemented in the following ways:

[0006] In a first aspect, this application provides a pulse width modulation method for a five-phase motor, the method comprising:

[0007] Obtain the reference voltage vector, which includes the fundamental reference voltage vector and the third harmonic reference voltage vector;

[0008] Based on the fundamental reference voltage vector, determine the sector in the fundamental space vector sector partitioning diagram where the fundamental reference voltage vector is located;

[0009] Based on the sector where the fundamental reference voltage vector is located, select several combinations of basic voltage vectors;

[0010] Several basic voltage vectors are combined to simulate and modulate the reference voltage vector, resulting in several sets of modulation times.

[0011] Select a unique feasible solution from several sets of modulation times, and select the basic voltage vector combination corresponding to the feasible solution to modulate the five-phase motor.

[0012] In one embodiment, the fundamental space vector sector partitioning diagram includes: 10 boundaries formed by the directions of the five-phase windings of the five-phase motor and the opposite directions of the five-phase windings in the fundamental space, and the angle bisectors of each pair of adjacent boundaries divide the fundamental space into 10 sectors.

[0013] In one embodiment, each boundary includes large, medium, and small vectors synthesized from different switching states.

[0014] In one embodiment, several combinations of fundamental voltage vectors are selected based on the sector where the fundamental reference voltage vector is located, including:

[0015] The selection range of the fundamental voltage vector is determined based on the sector where the fundamental reference voltage vector is located;

[0016] Based on the selection criteria, several combinations of basic voltage vectors are selected from the range of basic voltage vectors.

[0017] In one embodiment, the selection range of the fundamental voltage vector is determined based on the sector where the fundamental reference voltage vector is located, including:

[0018] Determine the boundaries within a sector based on the sector where the fundamental reference voltage vector is located;

[0019] Rotate the boundaries 90° counterclockwise and 90° clockwise respectively to form the selected area;

[0020] The selection range of the basic voltage vector is formed by selecting the large, medium, and small vectors of all boundaries within the region.

[0021] In one embodiment, the selection criteria include:

[0022] All basic voltage vectors in the basic voltage vector combination satisfy the principle of minimum number of switching operations;

[0023] The basic voltage vector combination includes large vectors in the sector where the fundamental reference voltage vector is located.

[0024] In one embodiment, selecting a unique feasible solution from a plurality of modulation times includes:

[0025] From a number of modulation times, select the group in which all modulation times are positive numbers;

[0026] The set of solutions where all modulation times are positive is considered a feasible solution.

[0027] In one embodiment, after obtaining the reference voltage vector, the method further includes:

[0028] The amplitude of the reference voltage vector is limited to prevent overmodulation.

[0029] In one embodiment, limiting the magnitude of the reference voltage vector includes:

[0030] If the amplitude of the fundamental reference voltage vector is less than or equal to the first preset amplitude, the amplitude of the fundamental reference voltage vector remains unchanged; wherein, the first preset amplitude is determined based on the modulation ratio of the bus voltage amplitude and the fundamental reference voltage.

[0031] If the magnitude of the basic reference voltage vector is greater than the first preset magnitude, then the magnitude of the basic reference voltage vector is set to the first preset magnitude.

[0032] If the amplitude of the third harmonic reference voltage vector is less than or equal to the second preset amplitude, the amplitude of the third harmonic reference voltage vector remains unchanged; wherein, the second preset amplitude is determined based on the amplitude of the fundamental reference voltage vector and the modulation ratio of the third harmonic reference voltage.

[0033] If the amplitude of the third harmonic reference voltage vector is greater than the second preset amplitude, then the amplitude of the third harmonic reference voltage vector is set to the second preset amplitude.

[0034] In a second aspect, this application provides a five-phase motor system, which includes a five-phase motor and a controller, wherein the controller performs any of the five-phase motor pulse width modulation methods described in the first aspect.

[0035] As can be seen from the technical solutions provided in the embodiments of this specification above, this solution can: modulate the third harmonic voltage, thus ensuring good harmonic characteristics when the motor is operating under high load; and injecting the third harmonic voltage under rated operating conditions can increase the modulation ratio of the fundamental voltage vector, which has a significant effect on improving the power density of the motor. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a vector distribution diagram of a five-phase motor's SVPWM.

[0038] Figure 2 This is a schematic diagram of the voltage vector synthesis principle of the NFV-SVPWM algorithm.

[0039] Figure 3 This is a structural schematic diagram of the five-phase motor system provided in this application;

[0040] Figure 4A flowchart illustrating the pulse width modulation method for a five-phase motor provided in this application;

[0041] Figure 5 The vector sector partitioning diagram provided for this application;

[0042] Figure 6 The reference voltage vector orthogonal decomposition diagram provided in this application;

[0043] Figure 7 The relationship diagram between modulation ratio, amplitude ratio, and phase difference provided in this application;

[0044] Figure 8 The simulation model diagram provided in this application;

[0045] Figure 9 The voltage modulation diagram of phase A under the 52.6V fundamental reference voltage command provided in this application;

[0046] Figure 10 Simulation diagram of phase A voltage waveform when the third harmonic vector provided in this application lags by 180° and the method of this application modulates a 14.2V harmonic voltage and a 60.4V fundamental voltage;

[0047] Figure 11 The waveform diagram of the back EMF of phase A voltage under no-load conditions provided in this application;

[0048] Figure 12 Fourier analysis diagram of the phase voltage back EMF waveform under no-load conditions provided in this application;

[0049] Figure 13 The waveform diagram of the back EMF of phase A voltage under load conditions provided in this application;

[0050] Figure 14 Fourier analysis diagram of phase voltage back EMF waveform under load conditions provided in this application;

[0051] Figure 15 Vector position diagrams of the fundamental and third harmonic waves of the motor provided in this application, along with their d-axis and q-axis positions.

[0052] Figure 16 Simulation diagram of the opening and closing state of phase A switch when the 14V harmonic voltage and 59V fundamental voltage are modulated by FV-SVPWM;

[0053] Figure 17 Waveform of phase A voltage when FV-SVPWM modulates 14V harmonic voltage and 59V fundamental voltage;

[0054] Figure 18 Waveform of phase A voltage when modulating a 59V fundamental voltage using the modulation method of this application;

[0055] Figure 19Simulation diagram of the on / off state of phase A switch when modulating a 59V fundamental voltage using the modulation method of this application. Detailed Implementation

[0056] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this specification.

[0057] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0058] Various modifications and variations can be made to the specific embodiments described in this application without departing from the scope or spirit of this application, as will be apparent to those skilled in the art. Other embodiments derived from this application will be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0059] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0060] Unless otherwise specified, "parts" in this application refers to parts by weight.

[0061] A five-phase inverter has five pairs of IGBT (Insulated Gate Bipolar Transistor) switches corresponding to the switches of the five phase windings A, B, C, D, and E. Therefore, by changing the switch states, a total of 2 5 Different fundamental voltage vectors, such as Figure 1 The diagram shows the vector distribution of a five-phase motor using SVPWM (Space Vector Pulse Width Modulation). Figure 1 (a) shows the vector distribution in the fundamental wave space. Figure 1 (b) shows the vector distribution in harmonic space. As shown in Figure (a), these 32 vectors can be divided into two zero vectors (V) in the fundamental space. 00000 V11111 ), ten large vectors (V 11001 V 11000 V 11100 V 01100 V 01110 V 00110 V 00111 V 00011 V 10011 V 10001 ), ten medium vectors (V 10000 V 11101 V 01000 V 11110 V 00100 V 01111 V 00010 V 10111 V 00001 V 11011 ), ten small vectors (V 01001 V 11010 V 10100 V 01101 V 01010 V 10110 V 00101 V 01011 V 10010 V 10101 ),like Figure 1 (b) The vector V in the fundamental space n The vector V corresponding to the third harmonic n ′, the large vector, medium vector, and small vector in the original fundamental wave space correspond to the small vector, medium vector, and large vector in the third harmonic space, respectively.

[0062] Currently, the traditional near-four vectors-based spacevector pulse width modulation (NFV-SVPWM) algorithm modulates the reference voltage vector U1 using two adjacent large vectors abe,ab and two medium vectors a,abce. For example... Figure 2 The diagram shown is a schematic of the voltage vector synthesis principle of the NFV-SVPWM algorithm. Figure 2 (a) is a schematic diagram of the fundamental space voltage vector synthesis principle. Figure 2 (b) is a schematic diagram of the harmonic space voltage vector synthesis principle.

[0063] Because in the third harmonic space, the amplitude of the median vector (a, abce) in the original fundamental space is 1.618 times the amplitude of the large vector (abe, ab) in the original fundamental space, and their directions are opposite. Therefore, if we let Figure 2In (b), the duration of the large vector abe is 1.618 times that of the medium vector a, and the duration of the large vector ab is 1.618 times that of the medium vector abce, which can cancel out the third harmonic voltage of the motor. Although this method eliminates the third harmonic voltage vector and harmonic voltage fluctuations, it also reduces the bus voltage utilization rate. However, in a five-phase motor, by properly controlling the third harmonic voltage, additional torque can be generated for the five-phase motor.

[0064] To address the issue of NFV-SVPWM's inability to modulate third harmonic voltage, related papers analyzed the injection of third harmonics into the fundamental frequency of induction motors and proposed two new third harmonic injection methods based on the original methods. These methods improve the modulation ratio of the motor bus voltage compared to previous methods; however, compared to the NFV-SVPWM algorithm, the modulation ratio decreases somewhat when injecting third harmonics.

[0065] Based on the above, the defects existing in the prior art include:

[0066] a. The traditional NFV-SVPWM algorithm cannot inject third harmonic voltage. This will cause the back electromotive force of the third harmonic to increase due to the change in inductance under high torque conditions, which will lead to a deterioration in the harmonic characteristics of the motor current and affect the motor torque.

[0067] b. In five-phase permanent magnet synchronous motors, existing space vector pulse width modulation (SVM) technology requires modulating the motor's third harmonic by sacrificing the modulation ratio of the bus voltage. Under high load and high power operation, this method severely affects the modulation ratio of the bus voltage, which is detrimental to high-power motor operation.

[0068] c. Although the traditional five-vector pulse width modulation algorithm (FV-SVPWM) can modulate a stable third harmonic voltage, the amplitude of the third harmonic voltage modulated by this algorithm is limited (i.e., the ratio of the third harmonic voltage amplitude to the fundamental voltage amplitude).

[0069] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0070] Reference Figure 3 This illustrates a structural schematic diagram of a five-phase motor system applicable to embodiments of this application. For example... Figure 3 As shown, the five-phase motor system includes a five-phase motor 31 and a controller 32, wherein the controller 32 executes the five-phase motor pulse width modulation method provided in the embodiments of this application.

[0071] Understandably, a five-phase motor system can be a five-phase permanent magnet synchronous motor system or a five-phase induction motor system, etc.

[0072] Reference Figure 4 It shows a flowchart of the pulse width modulation method for a five-phase motor applicable to the embodiments of this application.

[0073] like Figure 4 As shown, a pulse width modulation method for a five-phase motor may include:

[0074] S410. Obtain the reference voltage vector, which includes the fundamental reference voltage vector and the third harmonic reference voltage vector.

[0075] Specifically, the controller issues a reference voltage input command, and then receives the input reference voltage vector. in, in, This is the fundamental reference voltage vector, also known simply as the fundamental voltage. This is the reference voltage vector for the third harmonic, also known simply as the third harmonic voltage.

[0076] S420. Based on the fundamental reference voltage vector, determine the sector in the fundamental space vector sector partitioning diagram where the fundamental reference voltage vector is located.

[0077] In one embodiment, the fundamental space vector sector division diagram includes: 10 boundaries formed by the directions of the five-phase windings of the five-phase motor and the opposite directions of the five-phase windings in the fundamental space, and the angle bisectors of each pair of adjacent boundaries divide the fundamental space into 10 sectors.

[0078] Specifically, refer to Figure 5 It shows a vector sector partitioning diagram, in which, Figure 5 (a) is a sector division diagram of the fundamental wave space vector. Figure 5 (b) is a sector division diagram of the third harmonic space vector. For example... Figure 5 As shown, the directions of the five-phase windings of the five-phase motor are ( Figure 5 The directions A, B, C, D, and E in the fundamental wave (and their opposite directions) can form 10 boundaries in the fundamental wave space. Each boundary is as follows: Figure 5 (a) shows the solid line, marked Q. y y∈1…10. Boundary Q on the fundamental space. y Corresponding to the third harmonic space Figure 5 The boundary location in (b) is marked as Q. y y ∈ 1…10. The dashed lines in the fundamental space are the angle bisectors between two adjacent boundaries. The 10 angle bisectors divide the fundamental space into 10 sectors, denoted as D. y At the aforementioned fundamental wave spatial boundary, as... Figure 5 (a) contains large, medium, and small vectors synthesized from different switching states, respectively labeled as follows: In the third harmonic space, the large vector in the fundamental space becomes the small vector in the third harmonic space, but in the opposite direction. The projections of the large, medium, and small vectors in the fundamental space onto the harmonic space are denoted as... The magnitude of the amplitude is shown in (1), where U dc This represents the amplitude of the bus voltage.

[0079]

[0080] Based on the received fundamental reference voltage vector The location can determine the fundamental reference voltage vector. The sector in the fundamental space vector sector partitioning diagram.

[0081] S430. Based on the sector where the fundamental reference voltage vector is located, select several combinations of basic voltage vectors, including:

[0082] The selection range of the fundamental voltage vector is determined based on the sector where the fundamental reference voltage vector is located;

[0083] Based on the selection criteria, several combinations of basic voltage vectors are selected from the range of basic voltage vectors.

[0084] In one embodiment, determining the selection range of the fundamental voltage vector based on the sector where the fundamental reference voltage vector is located may include:

[0085] Determine the boundaries within a sector based on the sector where the fundamental reference voltage vector is located;

[0086] Rotate the boundaries 90° counterclockwise and 90° clockwise respectively to form the selected area;

[0087] The selection range of the basic voltage vector is formed by selecting the large, medium, and small vectors of all boundaries within the region.

[0088] In one embodiment, the selection criteria may include:

[0089] All basic voltage vectors in the basic voltage vector combination satisfy the principle of minimum number of switching operations;

[0090] The basic voltage vector combination includes large vectors in the sector where the fundamental reference voltage vector is located.

[0091] Specifically, when the fundamental reference voltage vector In D y When selecting a sector, the range for selecting the basic voltage vector is determined based on the selected region: Where ya < 0 (a ∈ 1, 2), then ya = y - a + 10; if y + a > 10, then ya = ya - 10. For example, when y = 1, i.e., sector D... 1 The inner boundary is Q 1 Q 1 Rotate 90° counterclockwise and 90° clockwise respectively to form the selected area as shown below. Figure 5 (a) shows the gray shaded area, within which all boundaries include Q. 1 Q 2 Q 3 Q 10 Q 9 Then the range of all corresponding basic voltage vectors is:

[0092] If four basic voltage vectors (i.e., combinations of basic voltage vectors) are directly selected from the 15 basic voltage vectors for pulse width modulation, there will be 1365 possible selection schemes, which significantly increases the complexity of the algorithm. To simplify the algorithm, this application adopts the following two principles to select the basic voltage vectors:

[0093] ① The four basic voltage vectors selected must meet the principle of minimum switching count. Since each switching on and off process in a five-phase motor increases the inverter loss during one PWM cycle, the four basic voltage vectors selected must meet the principle of minimum switching count in order to reduce the loss of the motor driver.

[0094] ② To maximize the modulation ratio of the fundamental voltage, the selected scheme must include the fundamental voltage vector. For example, when y = 1, the basic voltage vector combination must include

[0095] Based on the above two principles, 12 alternative schemes (i.e., 12 combinations of basic voltage vectors) can be selected: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

[0096] S440. Combine several basic voltage vectors to simulate and modulate the reference voltage vector to obtain several sets of modulation times.

[0097] Specifically, the above 12 selection schemes are applied to the reference voltage vector. Simulation modulation was performed, and 12 solutions were obtained, which are 12 sets of modulation times.

[0098] For example, taking Scheme 1 as an example, the basic voltage vector is selected. For the reference voltage vector Modulation is performed. For example... Figure 6 As shown, it illustrates an orthogonal decomposition plot of the reference voltage vector, in which, Figure 6 (a) is the orthogonal decomposition diagram of the fundamental reference voltage vector in the fundamental space. Figure 6 (b) is an orthogonal decomposition diagram of the third harmonic reference voltage vector in the third harmonic space. For example... Figure 6 As shown in (a), the fundamental reference voltage vector At the boundary line Q y Orthogonal decomposition is performed on the above to obtain Right now At the same time, such as Figure 6 As shown in (b), the third harmonic reference voltage vector At the boundary line Q y Orthogonal decomposition is performed on ′ to obtain Right now ( Figure 6 (a) α 1 shaft and Figure 5 Q in (a) 1 Axis coincidence, Figure 6 (a) β 1 shaft and Figure 5 Q in (a) 3 Axis and Q 4 The angle bisector of the axis is perpendicular. Figure 6 (b) α 3 shaft and Figure 5 (b) Q 1 ' axis coincides Figure 6 (b) β 3 shaft and Figure 5 (b) Q 5 ′ axis and Q 2 The angle bisector of the '-axis is perpendicular to it.

[0099] Similarly, the basic voltage vector Perform orthogonal decomposition separately to obtain the following results: Its size is shown in (2):

[0100]

[0101] Understandably, the above angles represent the fundamental voltage vector and α, respectively. 1 The angle between the axes, for example, 0 degrees, represents the fundamental voltage vector and α. 1 The axes coincide, and so on.

[0102] Using the basic voltage vector modulation Equation (3) is obtained:

[0103]

[0104] in,

[0105]

[0106]

[0107] Among them, T s One PWM cycle is T; T is the basic voltage vector modulation time within one PWM cycle. For the basic voltage vector The duration of action within one PWM cycle; For the basic voltage vector The duration of action within one PWM cycle; For the basic voltage vector The duration of action within one PWM cycle; For the basic voltage vector The duration of action within one PWM cycle.

[0108] Transforming equation (3), we get:

[0109]

[0110] Substituting (1) and (2) into (4) yields the modulation time of each basic voltage vector.

[0111] Similarly, the other eleven pulse width modulation schemes can all be solved by the above method to obtain the basic voltage vector, thus obtaining the 12 modulation times.

[0112] S450. Select a unique feasible solution from several sets of modulation times, and select the basic voltage vector combination corresponding to the feasible solution to modulate the five-phase motor.

[0113] Among them, selecting a unique feasible solution from several sets of modulation times can include:

[0114] From a number of modulation times, select the group in which all modulation times are positive numbers;

[0115] The set of solutions where all modulation times are positive is considered a feasible solution.

[0116] Specifically, in S440, 12 sets of modulation times are obtained. Among the 12 solutions, only one set of modulation times is all positive. The other 11 solutions all have negative solutions. Since the time constant does not have negative values, the other 11 solutions can be discarded, and a unique feasible solution is obtained. The basic voltage vector combination corresponding to this feasible solution is used to modulate the five-phase motor.

[0117] The modulation method in this application expands the original NFV-SVPWM's four vectors to 15 vectors, and then filters the vector selection schemes based on the principles of minimizing the number of switching operations and maximizing the modulation ratio. This results in 12 schemes, and then a unique solution is selected based on the principle that the equation solution is greater than 0.

[0118] The modulation method of this application can modulate a controllable fundamental voltage vector and harmonic voltage vector in any vector direction within the permissible range of the bus voltage modulation ratio.

[0119] The modulation method of this application is such that, in the third harmonic space, the large vector on the original fundamental wave will become a small vector in the harmonic space, but the direction will be reversed. Therefore, when modulating the inverted third harmonic, modulation can be achieved by increasing the duty cycle of the two large vectors in the fundamental wave space, thereby increasing the modulation ratio of the fundamental wave voltage vector.

[0120] The modulation method of this application can control the third harmonic voltage while controlling the fundamental voltage of a five-phase motor, and generate additional torque in the five-phase motor by adjusting the third harmonic voltage, thereby maximizing the utilization of the motor bus voltage and increasing the power density of the motor.

[0121] To prevent overmodulation in the inverter, the amplitude of the reference voltage needs to be limited.

[0122] In one embodiment, after obtaining the reference voltage vector, the method further includes:

[0123] The amplitude of the reference voltage vector is limited to prevent overmodulation.

[0124] In one embodiment, limiting the magnitude of the reference voltage vector includes:

[0125] If the amplitude of the fundamental reference voltage vector is less than or equal to the first preset amplitude, the amplitude of the fundamental reference voltage vector remains unchanged; wherein, the first preset amplitude is determined based on the modulation ratio of the bus voltage amplitude and the fundamental reference voltage.

[0126] If the magnitude of the basic reference voltage vector is greater than the first preset magnitude, then the magnitude of the basic reference voltage vector is set to the first preset magnitude.

[0127] If the amplitude of the third harmonic reference voltage vector is less than or equal to the second preset amplitude, the amplitude of the third harmonic reference voltage vector remains unchanged; wherein, the second preset amplitude is determined based on the amplitude of the fundamental reference voltage vector and the modulation ratio of the third harmonic reference voltage.

[0128] If the amplitude of the third harmonic reference voltage vector is greater than the second preset amplitude, then the amplitude of the third harmonic reference voltage vector is set to the second preset amplitude.

[0129] Specifically, when the reference voltage vector is obtained Then, the reference voltage vector is subjected to anti-overmodulation processing using the following formula:

[0130]

[0131]

[0132] Wherein, V1 corresponds to the fundamental reference voltage vector. |V1| is the fundamental reference voltage vector. The amplitude, V3 corresponds to the third harmonic reference voltage vector. |V3| is the third harmonic reference voltage vector. The amplitude. The first preset amplitude is The second preset amplitude is in, The fundamental voltage modulation ratio, This is the third harmonic voltage modulation ratio.

[0133] For the fundamental voltage modulation ratio and The third harmonic voltage modulation ratio can be determined in the following way.

[0134] Since pulse width modulation of a five-phase motor requires modulation of both the fundamental reference voltage vector and the third harmonic reference voltage vector, this application defines the fundamental voltage modulation ratio and the third harmonic voltage modulation ratio of the pulse width modulation of a five-phase motor.

[0135] First, define the voltage modulation signal for the five-phase inverter, as shown below:

[0136]

[0137] Let the amplitude ratio of the third harmonic voltage to the fundamental voltage be σ:

[0138]

[0139] Substituting equation (8) into equation (7), we get:

[0140]

[0141] Modulation ratio of fundamental frequency voltage Defined as: when the modulation amplitude ratio is σ and the phase difference is... When dealing with the third harmonic voltage, the maximum moduloable fundamental voltage amplitude max(|V1|) is related to the amplitude of the bus voltage |U. dc |Comparison, as shown in (10):

[0142]

[0143] Third harmonic voltage modulation ratio Defined as: when the modulation phase difference is When the third harmonic voltage is used, the ratio of the maximum moduloable third harmonic voltage amplitude to the fundamental voltage amplitude is shown in (11):

[0144]

[0145] Where max(|V3|) is the maximum modulotable third harmonic voltage amplitude when the fundamental voltage has a modulation amplitude of |V1|.

[0146] In this application, the modulation ratios of the fundamental voltage and the third harmonic voltage are solved using nonlinear programming. The nonlinear programming equation for the fundamental voltage modulation ratio is defined as follows:

[0147]

[0148]

[0149] The nonlinear programming equation for the third harmonic voltage modulation ratio is defined as follows:

[0150]

[0151]

[0152] By modeling the fundamental voltage modulation ratio and the third harmonic voltage modulation ratio as described above, we can obtain the fundamental voltage modulation ratio and the harmonic voltage modulation ratio relative to the amplitude ratio σ and the phase difference. Relationships, such as Figure 7 As shown. From Figure 7 This can be reflected in the fact that the fundamental voltage modulation ratio will change with the phase difference. It changes with the amplitude ratio σ. When the phase difference... When the amplitude ratio σ is 0 and the fundamental voltage modulation ratio is 0.23, the fundamental voltage modulation ratio reaches its maximum, i.e., 0.604.

[0153] Traditional NFV-SVPWM algorithms use two adjacent large vectors and two medium vectors for modulation. Because the amplitude of the medium vector is 1.618 times that of the large vector in the third harmonic space, ensuring the duration of the large vector is 1.618 times that of the medium vector can cancel the third harmonic voltage of the motor. However, the motor itself contains a small amount of third harmonic flux linkage, and under rated operating conditions, inductor saturation can generate third harmonic voltage. Traditional NFV-SVPWM algorithms cannot modulate this third harmonic voltage. Therefore, under high motor load conditions, traditional NFV-SVPWM algorithms struggle to guarantee good harmonic characteristics. The modulation method proposed in this application, however, can modulate the third harmonic voltage, thus ensuring good harmonic characteristics even under high motor load conditions.

[0154] Existing technologies propose a four-vector pulse width modulation algorithm that injects third harmonics. However, this algorithm requires sacrificing the modulation ratio of the third harmonic voltage to inject it. When the motor is running under rated load, the modulation ratio of the bus voltage will greatly limit the motor speed, thus limiting the motor's power density. The modulation method (NMV-SVPWM) proposed in this application, however, can increase the modulation ratio of the fundamental voltage vector by injecting third harmonic voltage under rated operating conditions. This has a significant effect on improving the motor's power density.

[0155] Experimental verification

[0156] Verification Example 1

[0157] To demonstrate the effectiveness and correctness of the proposed bus voltage modulation strategy, a Simulink simulation model of SVPWM was built, and the model was verified. Figure 8 The image shown is a simulation model diagram, as follows: Figure 9 The diagram shows the voltage modulation of phase A under a 52.6V fundamental reference voltage command.

[0158] like Figure 8 , Figure 9 As shown, it is easy to verify that without third harmonic voltage injection, the bus voltage modulation ratio of the modulation method in this application is equal to the modulation ratio of the NFV-SVPWM algorithm. Since the bus voltage of the simulated motor is 100V, the maximum modulated voltage without third harmonic voltage injection is 52.6V. That is, without third harmonic voltage injection, the fundamental frequency bus voltage modulation ratio can reach 52.6 / 100, or 0.526.

[0159] Verification Example 2

[0160] when At this time, injecting the third harmonic voltage can maximize the bus voltage modulation ratio, reaching 0.604. Next, we take... U3 = 14.2V, U1 = 60.4V, U dc Simulation was performed at 100V, and the simulation results are as follows: Figure 10 As shown. By Figure 10 It can be concluded that the maximum bus voltage utilization rate that the modulation method of this application can achieve after injecting the third harmonic voltage, that is, the maximum bus voltage modulation ratio, is 0.604.

[0161] Verification Example 3

[0162] In low-torque, low-power operation of a motor, smooth operation is sufficient. However, in high-torque, high-speed operation, the duty cycle of the motor's bus voltage significantly affects the modulation ratio. Furthermore, under high-torque conditions, changes in the inductance of the motor's direct-axis and quadrature-axis axes lead to an increase in the amplitude of the third harmonic of the back electromotive force (EMF) in the five-phase motor, and a phase lag compared to the no-load condition. Based on this phenomenon, if a third harmonic voltage cannot be modulated to counteract the third harmonic back EMF, the motor will generate a third harmonic current that is detrimental to torque enhancement and reduces efficiency, resulting in decreased smoothness under high-torque conditions. The following figure shows the finite element analysis of the back EMF characteristics of a five-phase motor under no-load and load conditions using Motor-CAD. Figure 11 The figure shown is the back EMF waveform of phase A voltage under no-load conditions, as follows: Figure 12 The figure shown is a Fourier analysis diagram of the phase voltage back EMF waveform under no-load conditions. Figure 13 The figure shown is the back EMF waveform of phase A voltage under load conditions. Figure 14 This is a Fourier analysis diagram of the phase voltage back EMF waveform under load conditions.

[0163] As can be seen from the Motor-CAD finite element analysis in the figure, the characteristics of the third harmonic will change as the motor torque increases. Under no-load torque, the phase of the motor back electromotive force is as follows (because the direction of the rotor's fundamental back electromotive force is located on the fundamental q-axis, the coordinate system is established below with the fundamental q-axis as the starting position and counterclockwise rotation as positive):

[0164] V=A1*sin(x-18°)+A3*sin(3x-55°)

[0165] Let y = x - 18°,

[0166] V = A1*sin(y) + A3*sin(3y+1°)

[0167] From the expression, it can be seen that the third harmonic flux linkage of the motor is almost in phase with the fundamental flux linkage, such as... Figure 15 The diagram shows the vector positions of the fundamental and third harmonic waves of the motor along the d and q axes.

[0168] Under rated operating conditions, the flow rate is 7.11 A / mm. 2 The back electromotive force characteristics of a five-phase motor finite element model are analyzed based on the current magnitude.

[0169] V=A1*sin(x+20.3°)+A3*sin(3x+245.4°)

[0170] Let y = x + 20.3°,

[0171] V=A1*sin(y)+A3*sin(3y+184.5°)

[0172] By comparing finite element analysis under no-load and rated operating conditions, it can be seen that the amplitude of the third harmonic back EMF of the motor increases with increasing motor current, and the phase of the third harmonic back EMF lags behind the fundamental back EMF, by approximately 184.5° compared to the no-load condition. Next, a third harmonic voltage with an amplitude of 13.8V and a phase lag of 184.5° is injected onto a fundamental voltage amplitude of 59V, and the model is simulated using Simulink. Figure 16 The diagram shown is a simulation of the on / off state of the A-phase switch when the FV-SVPWM modulates a 14V harmonic voltage and a 59V fundamental voltage. Figure 17 The figure shows the voltage waveform of phase A when FV-SVPWM modulates a 14V harmonic voltage and a 59V fundamental voltage; as shown. Figure 18 The figure shown is the voltage waveform of phase A when the modulation method of this application modulates the 59V fundamental voltage; as shown Figure 19 The figure shown is a simulation diagram of the on / off state of the A-phase switch when the modulation method of this application modulates the 59V fundamental voltage.

[0173] As can be seen from the above figure, after injecting a third harmonic voltage vector with a phase angle lag of 184.5°, the A-phase switch of the modulation method of this application can still open and close normally, while the modulation method of this application reaches saturation at a modulation amplitude of 52.6V (the maximum bus voltage modulation ratio of this algorithm is 0.526). Therefore, the simulation verifies that under the rated operating conditions of this five-phase motor, the injection of the third harmonic promotes the improvement of the modulation ratio of the fundamental voltage.

[0174] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0175] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

Claims

1. A pulse width modulation method for a five-phase motor, characterized in that, The method includes: Obtain a reference voltage vector, which includes a fundamental reference voltage vector and a third harmonic reference voltage vector; Based on the fundamental reference voltage vector, determine the sector in the fundamental space vector sector partitioning diagram where the fundamental reference voltage vector is located; Based on the sector where the fundamental reference voltage vector is located, select several combinations of basic voltage vectors; The reference voltage vector is simulated by combining the several basic voltage vectors to obtain several sets of modulation times. Select a unique feasible solution from the several sets of modulation times, and select the basic voltage vector combination corresponding to the feasible solution to modulate the five-phase motor; The fundamental space vector sector division diagram includes: 10 boundaries formed by the directions of the five-phase windings of the five-phase motor and the opposite directions of the five-phase windings in the fundamental space, and the angle bisector of each pair of adjacent boundaries divides the fundamental space into 10 sectors. Each boundary includes large, medium, and small vectors synthesized from different switching states; The step of selecting several combinations of basic voltage vectors based on the sector where the fundamental reference voltage vector is located includes: The boundaries within a sector are determined based on the sector where the fundamental reference voltage vector is located; Rotate the boundaries 90° counterclockwise and 90° clockwise respectively to form the selected area; The large, medium, and small vectors of all boundaries within the selected area constitute the selection range of the basic voltage vectors; all basic voltage vectors in the basic voltage vector combination satisfy the principle of minimum switching times; the basic voltage vector combination includes the large vector in the sector where the fundamental reference voltage vector is located; the basic voltage vector combination consists of 4 basic voltage vectors.

2. The method according to claim 1, characterized in that, The step of selecting a unique feasible solution from the plurality of modulation times includes: From the aforementioned sets of modulation times, select one set in which all modulation times are positive numbers; The set of all positive modulation times is considered a feasible solution.

3. The method according to claim 1, characterized in that, After obtaining the reference voltage vector, the method further includes: The amplitude of the reference voltage vector is limited to prevent overmodulation.

4. The method according to claim 3, characterized in that, The limitation on the magnitude of the reference voltage vector includes: If the amplitude of the fundamental reference voltage vector is less than or equal to a first preset amplitude, then the amplitude of the fundamental reference voltage vector remains unchanged; wherein, the first preset amplitude is determined based on the bus voltage amplitude and the fundamental reference voltage modulation ratio; If the amplitude of the fundamental reference voltage vector is greater than the first preset amplitude, then the amplitude of the fundamental reference voltage vector is set to the first preset amplitude. If the amplitude of the third harmonic reference voltage vector is less than or equal to the second preset amplitude, the amplitude of the third harmonic reference voltage vector remains unchanged; wherein, the second preset amplitude is determined based on the amplitude of the fundamental reference voltage vector and the modulation ratio of the third harmonic reference voltage. If the amplitude of the third harmonic reference voltage vector is greater than the second preset amplitude, then the amplitude of the third harmonic reference voltage vector is set to the second preset amplitude.

5. A five-phase motor system, characterized in that, The system includes a five-phase motor and a controller, the controller performing the five-phase motor pulse width modulation method as described in any one of claims 1-4.

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