Power allocation method for single-stage multi-port motor drive based on vector decomposition

Abstract

The present invention discloses a single-stage multi-port motor drive power distribution method based on vector decomposition. According to the needs under different working conditions, the single-stage multi-port inverter is equivalent to two two-level inverters, and then based on the two-level inverter, a power distribution strategy based on space vector decomposition is further proposed. In this way, the energy transmission efficiency of the power system is improved while the stability under complex working conditions is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power distribution control of single-stage multi-port motor drivers, and more specifically, relates to a power distribution control method of a single-stage multi-port motor driver based on space vector decomposition. Background Art

[0002] With the development and progress of society, the increasing depletion of fossil energy has become a serious problem that people have to pay attention to. In recent years, the strategy of replacing fuel vehicles with electric vehicles has provided scientists with an effective solution to the fossil energy crisis. At the same time, electric vehicles driven by new energy have occupied part of the automotive industry market, and have also made new energy vehicles widely concerned by people. However, new energy vehicles are facing severe tests in terms of power supply mode, battery charging and discharging, and power system performance. In order to effectively solve these problems and maximize the advantages of new energy vehicles, choosing a suitable topology and a complete modulation method can reduce the loss of electric energy during transmission and achieve efficient energy transfer.

[0003] At present, most hybrid motor drive systems are two-stage, that is, the power supply needs to pass through two-stage converters, DC-DC converter and DC-AC inverter, to achieve motor drive. Such a structure increases the weight and volume of the system and reduces the power density of the system. At the same time, the two-stage topology causes the energy flow between the power system and the motor to undergo two energy conversions, greatly reducing the energy transmission efficiency. In order to solve the drawbacks of the two-stage inverter, the single-stage multi-port inverter has begun to be widely studied. The single-stage multi-port inverter removes the DC-DC converter of the previous stage and directly connects the input voltage to the upper and lower bridge arms of the inverter, so that the energy is directly transmitted from the DC end to the AC end through the inverter. Thanks to the direct conversion of energy by the single-stage multi-port inverter, the energy transmission efficiency of the system is greatly improved, providing a practical solution for improving the efficiency of the power supply system of new energy vehicles.

[0004] Comparison with the invention patent of the same type: A quasi-single-stage variable bus voltage motor drive device and control method. The present invention adopts a single-stage multi-port inverter, that is, the bidirectional DC-DC converter of the previous stage is removed, so that the cost of the topological structure is lower. At the same time, the present invention decomposes the space vector to make the original single-stage multi-port inverter equivalent to two two-level inverters, thereby realizing the flexible distribution of the port power of the single-stage multi-port inverter. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a single-stage multi-port motor drive power distribution method based on vector decomposition, which utilizes the decomposed space vector and the replacement idea of ​​the single-stage multi-port inverter structure being equivalent to two two-level inverters to achieve flexible distribution of the output power of the single-stage multi-port inverter.

[0006] To achieve the above-mentioned object of the invention, the present invention provides a single-stage multi-port motor driver power distribution method based on vector decomposition, characterized in that it includes the following steps:

[0007] (1) Obtain the reference composite voltage v of the permanent magnet synchronous motor in the stationary coordinate system * ;

[0008] (1.1), assuming that the given speed of the three-phase AC motor is

[0009] (1.2) Obtain the position angle θ of the three-phase AC motor through the position encoding module, input θ into the speed calculation module, and obtain the actual speed ω of the three-phase AC motor. e ;

[0010] (1.3) With ω e The difference is controlled by the speed PI controller to obtain the first given current of the q axis.

[0011] (1.4) The three-phase current i generated by the single-stage multi-port inverter a 、i b 、i c After T1 coordinate transformation, the first actual current i of the q axis is obtained q and the second actual current i of the d-axis d ;

[0012] (1.5) with i q The difference is controlled by the PI controller of the current of the q-axis to generate the first given voltage v of the q-axis of the plane in the rotating coordinate system. q ;

[0013] (1.6), given the second given current of the d-axis Will with i d The difference is controlled by the d-axis PI controller to generate the d-axis second given voltage v in the rotating coordinate system plane. d ;

[0014] (1.7), the first given voltage v q , the second given voltage v dThe plane vector v in the stationary coordinate system is obtained by T2 coordinate transformation α With v β , and then use v α With v β Synthesized composite space vector voltage v * ;

[0015] (2) Through the composite space vector v * Calculate the total active power P of a single-stage multi-port inverter * ;

[0016]

[0017] in, represents the conjugate of the current vector i;

[0018] (3) Decomposition of the composite space vector v * for and

[0019] The single-stage multi-port inverter is decomposed into two two-level inverters, denoted as inverter 1 and inverter 2. The space vectors acting on inverter 1 and inverter 2 are respectively and

[0020] Composite space vector v * It is expressed as the vector sum of the space vectors of inverter 1 and inverter 2:

[0021]

[0022] (4) Decompose the total active power P* into the active power output by inverter 1 and inverter 2

[0023] (4.1), according to the space vector relationship make Wherein, k is the ratio of the output active power of the equivalent inverter 1 to the output active power of the single-stage multi-port inverter;

[0024] (4.2), calculate the space vector of inverter 1 The output active power under the action of is expressed as:

[0025]

[0026] Furthermore, by P1 * The expression of k is obtained as follows:

[0027]

[0028] Similarly, we get the space vector of inverter 2 The output active power under the action of

[0029]

[0030] (5) Power distribution is achieved by changing the k value, and the Dwell time under two-level space vector;

[0031] (5.1) When the total active power P* remains unchanged, the power size between inverter 1 and inverter 2 is realized by changing the k value, thereby realizing the power distribution between inverter 1 and inverter 2;

[0032] (5.2) After the power distribution is completed, the space vectors are determined according to the active power output by inverter 1 and inverter 2. The duration of action;

[0033] (5.2.1) For inverter 1, in two-level space vector modulation, a given reference voltage of one cycle is divided into the following six sectors according to phase θ:

[0034]

[0035] (5.2.2) Convert θ in other sectors to the first sector. The conversion method is as follows: If θ is in the second sector, let If θ is in the third sector, let By analogy, when θ is in the fourth, fifth, and sixth sectors, for subtracting π, That's it;

[0036] (5.2.3), in the first sector, let the two adjacent active voltage space vectors be v a With v b ,but j represents the imaginary part; in a sampling period T s Inside, The action time of inverter 1 is expressed as follows:

[0037]

[0038] Among them, T1' and T2' are respectively the voltage of inverter 1 a and v b Duration, d x1 ∈[0,T s ] represents the action time of each phase, x = a, b, c, represents three phases;

[0039] Similarly, in a sampling period T s Inside, The action time of inverter 2 is expressed as follows:

[0040]

[0041] Where T″1 and T″2 are the v a and v b duration, and T″0=T s -T″1-T″2,d x2 ∈[0,T s ] indicates the action time of each phase;

[0042] (6) The space vector synthesis controller generates modulation waveforms SVPWM1 and SVPWM2 according to the action time of each phase, and then compares the modulation waveforms with the amplitude of the triangular carrier in one switching cycle to generate six switching signals G that drive the single-stage multi-port inverter. x1 , G x2 , and then use the driving signal G x1 Control switch tube S x1 , driving signal G x1 The complementary signal controls the switch tube S x3 , driving signal G x2 Control switch tube S x2 , driving signal G x2 The complementary signal controls the switch tube S x4 , S x1 , S x2 , S x3 , S x4 They correspond to the upper tube, upper middle tube, middle lower tube, and lower tube of the bridge arm respectively.

[0043] The object of the invention of the present invention is achieved in this way:

[0044] The present invention discloses a single-stage multi-port motor driver power distribution method based on vector decomposition. According to the needs under different working conditions, the single-stage multi-port inverter is equivalent to two two-level inverters, and then based on the two-level inverter, a power distribution strategy based on space vector decomposition is further proposed. In this way, the energy transmission efficiency of the power system is improved while the stability under complex working conditions is improved.

[0045] At the same time, the single-stage multi-port motor driver power allocation method based on vector decomposition of the present invention also has the following beneficial effects:

[0046] (1) In terms of topology, the DC-DC converter in the front stage of the quasi-single-stage multi-port inverter is removed, reducing the cost of the topology. At the same time, the structure adopted enables the energy of the DC port to be completely transferred to the single-stage multi-port inverter, reducing the energy loss in the DC-DC converter.

[0047] (2) By adopting the idea of ​​equivalent replacement, the single-stage multi-port inverter is equivalent to two two-level current inverters, avoiding the complex sector identification and dwell time calculation under the unevenly distributed voltage vector diagram, and greatly reducing the workload in the modulation process. At the same time, the decomposition of the space vector can adjust the active power output of the two equivalent two-level inverters to achieve power distribution between ports. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic diagram of a single-stage multi-port drive motor device based on space vector decomposition;

[0049] Figure 2 It is a schematic diagram and topological structure diagram of a single-stage multi-port inverter;

[0050] Figure 3 It is a schematic diagram of the topological decomposition and space vector decomposition of a single-stage multi-port inverter.

[0051] Figure 4 It is a schematic diagram of sector division;

[0052] Figure 5 It is a schematic diagram of the time of action of the space vector in the sector;

[0053] Figure 6 yes and v H Adjust v while keeping it constant L The operating curve of the single-stage multi-port inverter after the size is changed;

[0054] Figure 7 It is the operating curve of single-stage multi-port inverter under different motor speeds. DETAILED DESCRIPTION

[0055] The specific implementation of the present invention is described below in conjunction with the accompanying drawings so that those skilled in the art can better understand the present invention. It should be noted that in the following description, when the detailed description of known functions and designs may dilute the main content of the present invention, these descriptions will be omitted here.

[0056] Example

[0057] Figure 1 It is the schematic diagram of a single-stage multi-port drive motor device based on space vector decomposition.

[0058] In this embodiment, we first briefly introduce the single-stage multi-port drive motor device based on space vector decomposition. Figure 1As shown, it includes: a DC bus input voltage, two DC detectors, two voltage stabilizing capacitors, a multi-port current inverter, a three-phase current detector, a motor drive controller, a power distribution controller and a space vector synthesis controller.

[0059] like Figure 2 (a) is a schematic diagram of a single-stage multi-port inverter, which has two input terminals and one output terminal. Figure 2 As shown in (b), the single-stage multi-port inverter structure is improved from the diode clamped (NPC) three-level inverter topology, with one power supply connected between the positive and negative poles, and another power supply connected between the neutral line and the ground line. A capacitor is connected between the neutral line and the ground line, and another capacitor is connected between the neutral line and the positive pole, while retaining the original three bridge arms of the inverter.

[0060] from Figure 1 It can be seen that the energy flow path from the two DC power supplies to the inverter reduces one DC bidirectional DC-DC unit compared with the traditional inverter of the same type, which can reduce the energy level conversion and improve the energy transmission efficiency of the system; in addition, according to the needs under different working conditions, the present invention converts the single-stage multi-port inverter into two two-level inverters, and further proposes a single-stage multi-port motor drive power allocation strategy based on space vector decomposition. The specific allocation includes the following steps:

[0061] S1. Obtain the reference composite voltage v of the permanent magnet synchronous motor in the stationary coordinate system * ;

[0062] S1.1, Assume that the given speed of the three-phase AC motor is

[0063] S1.2. Obtain the position angle θ of the three-phase AC motor through the position encoding module, input θ into the speed calculation module, and obtain the actual speed ω of the three-phase AC motor. e ;

[0064] S1.3. With ω e The difference is controlled by the speed PI controller to obtain the first given current of the q axis.

[0065] S1.4, the three-phase current i generated by the single-stage multi-port inverter a 、i b 、i c After T1 coordinate transformation, the first actual current i of the q axis is obtained q and the second actual current i of the d-axis d ;

[0066] Among them, the formula for T1 coordinate transformation is:

[0067]

[0068] S1.5. with i q The difference is controlled by the PI controller of the current of the q-axis to generate the first given voltage v of the q-axis of the plane in the rotating coordinate system. q ;

[0069] S1.6, set the second set current of d axis Will with i d The difference is controlled by the d-axis PI controller to generate the d-axis second given voltage v in the rotating coordinate system plane. d ;

[0070] S1.7, the first given voltage v q , the second given voltage v d Through T2 coordinate transformation, we can get the vector v of the plane in the stationary coordinate system. α With v β , and then use v α With v β Synthesized composite space vector voltage v * ;

[0071] Among them, the formula for T2 coordinate transformation is:

[0072]

[0073] S2, through the composite space vector v * Calculate the total active power P of a single-stage multi-port inverter * ;

[0074] In this embodiment, since v * It is obtained through the T1 and T2 coordinate transformation units, so the system power is reduced by 2 / 3 compared with before the coordinate transformation. Therefore, the actual required active power P * for:

[0075]

[0076] in, represents the conjugate of the current vector i;

[0077] S3. Decomposition of composite space vector v * for and

[0078] For the convenience of description and understanding, the single-stage multi-port inverter is decomposed into two two-level inverters, denoted as inverter 1 and inverter 2, as shown in the attached figure. Figure 3 (a)

[0079] like Figure 3 As shown in (b), the space vectors acting on inverter 1 and inverter 2 are and Composite space vector v * It is expressed as the vector sum of the space vectors of inverter 1 and inverter 2, that is:

[0080]

[0081] S4, the total active power P * Decomposed into two equivalent inverters, the active power P1 output by inverter 1 and inverter 2 is obtained * ,

[0082] S4.1. According to the space vector relationship make Then there is Wherein, k is the ratio of the output active power of the two-level inverter 1 to the output active power of the single-stage multi-port inverter;

[0083] S4.2. Since the switches are connected in series in a certain phase, the current vectors flowing through them are consistent, so the inverter 1 is in the space vector Under the action of , its output active power can be expressed as:

[0084]

[0085] Furthermore, by P1 * The expression of k is obtained as follows:

[0086]

[0087] Similarly, we get the space vector of inverter 2 The output active power under the action of

[0088]

[0089] S5. Power distribution is achieved by changing the k value, and the Dwell time under two-level space vector;

[0090] S5.1, in the total active power P * Under the condition that the power remains unchanged, the power size between inverter 1 and inverter 2 is realized by changing the k value, thereby realizing the power distribution between inverter 1 and inverter 2;

[0091] S5.2. After the power distribution is completed, the space vectors are determined according to the active power output by inverter 1 and inverter 2. The duration of action;

[0092] In this embodiment, when the k value is determined, P1 * , is uniquely determined by P1 * , From the functional expression, we know that when the system works normally and stably and the current remains unchanged, P1 * Size by In a two-level space vector the action time is determined, Size by The action time of the space vector in two levels is determined;

[0093] S5.2.1. For inverter 1, in two-level space vector modulation, a given reference voltage of one cycle is divided into the following six sectors according to phase θ:

[0094]

[0095] In this embodiment, the sectors are divided as follows: Figure 4 As shown, in order to achieve high-quality voltage output of the single-stage multi-port motor driver and prevent over-modulation, the reference voltage v ref The amplitude must satisfy: Among them, V H is the DC bus input voltage;

[0096] S5.2.2. Convert θ in other sectors to the first sector. The conversion method is as follows: If θ is in the second sector, let If θ is in the third sector, let By analogy, when θ is in the fourth, fifth, and sixth sectors, for subtracting π, That's it;

[0097] S5.2.3, in the first sector, let the two adjacent active voltage space vectors be v a With v b ,but j represents the imaginary part; in a sampling period T s Inside, The action time of inverter 1 is expressed as follows:

[0098]

[0099] Among them, T′1 and T′2 are respectively the voltage of inverter 1 a and v b Duration, dx1 ∈[0,T s ] represents the action time of each phase, x = a, b, c, represents three phases;

[0100] Similarly, in a sampling period T s Inside, The action time of inverter 2 is expressed as follows:

[0101]

[0102] Where T″1 and T″2 are respectively the voltage of inverter 2 a and v b duration, and T″0=T s -T″1-T″2,d x2 ∈[0,T s ] indicates the action time of each phase;

[0103] In this embodiment, Figure 3 (a) It can be seen that the DC voltage corresponding to inverter 1 is v H -v L , the DC voltage corresponding to inverter 2 is v L . Figure 5 (a) is a sampling period T s Space vector of inner inverter 1 Schematic diagram of the relationship between action time and corresponding level in modulation. Figure 5 (b) is a sampling period T s Space vector of inner inverter 2 Schematic diagram of the relationship between action time and corresponding level in modulation. Figure 5 (c) is a sampling period T s Space vector v of single-stage multi-port inverter * Schematic diagram of the relationship between the action time and the corresponding level in modulation. From Figure (5), we can see that at the same time, v * The level size is and The superposition of levels verifies the correctness of the idea of ​​equivalent substitution.

[0104] S6, the space vector synthesis controller generates modulation waveforms SVPWM1 and SVPWM2 according to the action time of each phase, and then compares the modulation waveforms with the amplitude of the triangular carrier in one switching cycle to generate six switching signals G that drive the single-stage multi-port inverter. x1 , G x2 , and then use the driving signal G x1 Control switch tube S x1 , driving signal G x1 The complementary signal controls the switch tube Sx3 , driving signal G x2 Control switch tube S x2 , driving signal G x2 The complementary signal controls the switch tube S x4 , S x1 , S x2 , S x3 , S x4 are the upper tube, upper middle tube, middle lower tube and lower tube of the corresponding bridge arm respectively.

[0105] Example verification

[0106] Next, we will explain this embodiment with an example. Suppose a DC power supply v H =300V,v L =125~175V, rated torque T N =8N·m, the rated active power is set to 1000W, the rated speed

[0107] In this embodiment, if Figure 6 As shown, when the rated speed and v H =300V remains unchanged, by adjusting v L The size of the motor is observed, and the stability of the motor at rated speed and rated torque is observed. Figure 6 (a) is v L = Working condition of single-stage multi-port inverter at 125V, Figure 6 (b) is v L =175V single-stage multi-port inverter working conditions, comparing the two figures shows that changing the DC power supply v L The size of the phase voltage v will not affect the rotation speed of the motor. aN With the output phase current i a No distortion will occur, v H With v L All of them can output stably, which shows that the present invention can achieve wide range regulation of DC bus voltage.

[0108] In this embodiment, if Figure 7 As shown, by changing the rated torque of the motor and the output power of the inverter 1, Figure 7 As can be seen from (a), when the motor torque is set to half of the rated torque, the output phase current i a The frequency and amplitude of the phase voltage have changed, the duration of the high level in the phase voltage has decreased, and the output power of inverter 1 is set to P1. * =0W. Figure 7 In (b), the motor speed is set to the rated speed and the inverter 1 output power is set to P1 *=600W; Figure 7 In (c), the motor speed is set to the rated speed and the inverter 1 output power is set to P1 * =1000W; Figure 7 In (d), the motor speed is set to the rated speed and the inverter 1 output power is set to P1 * = 1400W, observe the power P1 output by inverter 1 and the working condition of the single-stage multi-port inverter; Figure 7 (b) Figure 7 (c) Figure 7 (d) It can be seen that under rated torque and different rated load conditions, as the rated load torque increases, the power of P1 increases accordingly, and the phase voltage v aN 、v bN 、v cN The duration of the high level increases, and the overall waveform of the inverter output remains unchanged. This shows that under the control method of the present invention, the power distribution of the port is achieved under different required motor torques.

[0109] Although the above describes the illustrative specific embodiments of the present invention to facilitate those skilled in the art to understand the present invention, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. A single-stage multi-port motor driver power allocation method based on vector decomposition, characterized in that: The following steps are involved: (1) Obtain the reference composite voltage v of the permanent magnet synchronous motor in the stationary coordinate system * ; (1.1), assuming that the given speed of the three-phase AC motor is (1.2) Obtain the phase angle θ of the three-phase AC motor through the position encoding module, input θ into the speed calculation module, and obtain the actual speed ω of the three-phase AC motor. e ; (1.3) With ω e The difference is controlled by the speed PI controller to obtain the first given current of the q axis. (1.4) The three-phase current i generated by the single-stage multi-port inverter a 、i b 、i c After T1 coordinate transformation, the first actual current i of the q axis is obtained q and the second actual current i of the d-axis d ; (1.5) with i q The difference is controlled by the PI controller of the current of the q-axis to generate the first given voltage v of the q-axis of the plane in the rotating coordinate system. q ; (1.6), given the second given current of the d-axis Will with i d The difference is controlled by the d-axis PI controller to generate the d-axis second given voltage v in the rotating coordinate system plane. d ; (1.7), the first given voltage v q , the second given voltage v d Through T2 coordinate transformation, we can get the vector v of the plane in the stationary coordinate system. α With v β , and then use v α With v β Synthesized composite space vector voltage v * ; (2) Through the composite space vector v * Calculate the total active power P of a single-stage multi-port inverter * ; in, represents the conjugate of the current vector i; (3) Decomposition of the composite space vector v * for and The single-stage multi-port inverter is equivalently decomposed into two two-level inverters, denoted as inverter 1 and inverter 2. The space vectors acting on inverter 1 and inverter 2 are respectively and Composite space vector v * It is expressed as the vector sum of the space vectors of inverter 1 and inverter 2: (4) Decompose the total active power P* into two two-level inverters to obtain the active power P1 output by inverter 1 and inverter 2 * , (4.1), according to the space vector relationship make Wherein, k is the ratio of the output active power of the inverter 1 to the output active power of the single-stage multi-port inverter; (4.2), calculate the space vector of inverter 1 The active power output under the action of can be expressed as: Furthermore, by P1 * The expression of k is obtained as follows: Similarly, we get the space vector of inverter 2 The output active power under the action of (5) Power distribution is achieved by changing the k value, and the Dwell time under two-level space vector; (5.1), in the total active power P * Under the condition that the power remains unchanged, the power size between inverter 1 and inverter 2 is realized by changing the k value, thereby realizing the power distribution between inverter 1 and inverter 2; (5.2) After the power distribution is completed, the space vectors are determined according to the active power output by inverter 1 and inverter 2. The duration of action; (5.2.1) For inverter 1, in two-level space vector modulation, a given reference voltage of one cycle is divided into the following six sectors according to phase θ: (5.2.2) Convert θ in other sectors to the first sector. The conversion method is as follows: If θ is in the second sector, let If θ is in the third sector, let By analogy, when θ is in the fourth, fifth, and sixth sectors, for subtracting π, That's it; (5.2.3), in the first sector, let the two adjacent active voltage space vectors be v a With v b ,but j represents the imaginary part; in a sampling period T s Inside, The action time of inverter 1 is expressed as follows: Among them, T1' and T2' are respectively the voltage of inverter 1 a and v b Duration, d x1 ∈[0,T s ] represents the action time of each phase, x = a, b, c, represents three phases; Similarly, in a sampling period T s Inside, The action time of inverter 2 is expressed as follows: Where T1" and T2" are the v a and v b duration, and T0" = T s -T1”-T2”,d x2 ∈[0,T s ] indicates the action time of each phase; (6) The space vector synthesis controller generates modulation waveforms SVPWM1 and SVPWM2 according to the action time of each phase, and then compares the modulation waveforms with the amplitude of the triangular carrier in one switching cycle to generate six switching signals G that drive the single-stage multi-port inverter. x1 , G x2 , and then use the driving signal G x1 Control switch tube S x1 , driving signal G x1 The complementary signal controls the switch tube S x3 , driving signal G x2 Control switch tube S x2 , driving signal G x2 The complementary signal controls the switch tube S x4 , S x1 , S x2 , S x3 , S x4 They correspond to the upper tube, upper middle tube, middle lower tube, and lower tube of the bridge arm respectively.

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