Twelve-phase motor five and seven harmonic suppression method

Abstract

The application discloses a five-seventh harmonic suppression method suitable for a twelve-phase motor, four sets of three-phase currents of a twelve-phase propulsion system are collected to obtain twelve alternating currents; two sets of three-phase windings of the twelve-phase motor with a phase difference of 30 degrees are taken as a whole, five-seventh harmonic amounts of the two sets of three-phase currents with a difference of 30 degrees are converted into direct currents by using a six-phase park conversion matrix; the output amounts of the direct currents obtained by a PI regulator are combined with the direct currents on a fundamental wave plane, and the alternating currents calculated by using a six-phase park inverse conversion matrix are taken as corresponding modulation waves of each channel respectively. The application is simple and easy to implement, has strong universality, has good five-seventh harmonic suppression effect, and is easy to be popularized to other multi-phase motor system harmonic suppression occasions.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of harmonic suppression of multiphase motor, and particularly relates to a five-seventh harmonic suppression method suitable for a twelve-phase motor. BACKGROUND

[0002] Compared with a traditional three-phase motor system, a multiphase motor has more prominent advantages in a high-power and high-reliability occasion, and a power propulsion system formed by a multiphase open-winding propulsion motor and a matching multiphase H-bridge frequency converter has the characteristics of simple main circuit topology, strong fault tolerance, small torque ripple, and easy expansion of power capacity, and is a preferred solution for a large-tonnage ship propulsion system.

[0003] Irrespective of a traditional three-phase motor or a multiphase motor system, due to a frequency converter PWM modulation dead zone, a minimum pulse width limit, or a flux linkage non-ideal, there are rich five-seventh current harmonics in motor winding currents. On the one hand, current harmonics affect motor control and easily cause base wave and harmonic control aliasing, and for three-level converter neutral point potential control or dead zone compensation depending on current direction, harmonics will cause control errors or failures. On the other hand, serious motor winding current distortion will directly affect motor system efficiency and increase vibration, and even worsen system electromagnetic capacity, and therefore, it is necessary to optimize and suppress harmonics.

[0004] Compared with a traditional three-phase motor system, the redundancy of the number of phases of a multiphase motor system adds a new degree of freedom to the harmonic control of the multiphase motor system. Since five-seventh harmonic frequencies are high, with the rated frequency of a large-capacity permanent magnet motor of a ship main propulsion being 50Hz, the corresponding five-seventh current harmonics are 250Hz or 350Hz, which have exceeded the current loop control bandwidth limit of a large-capacity frequency converter (the switching frequency of a large-capacity frequency converter is ≤1kHz due to the junction temperature limit of a device), resulting in poor effect of a conventional harmonic suppression method, and the conventional method does not fully exert the multiphase degree of freedom characteristics of the motor system. SUMMARY

[0005] The application aims to solve the above technical problems, and provides a five-seventh harmonic suppression method suitable for a twelve-phase motor, so as to realize optimized control of motor harmonic currents and improve motor operation control performance.

[0006] To achieve the above object, the application provides a five-seventh harmonic suppression method suitable for a twelve-phase motor, which is characterized in that:

[0007] 1) four sets of three-phase currents of the twelve-phase propulsion system are collected respectively to obtain twelve alternating currents;

[0008] 2) two sets of three-phase windings of the twelve-phase motor with a phase difference of 30° are taken as a whole, and five-seventh harmonic quantities of two sets of three-phase currents with a difference of 30° are converted into direct currents by using a six-phase park conversion matrix;

[0009] 3) The output of the PI regulator is combined with the direct current of the fundamental plane, and the cross current calculated by the six-phase park inverse transformation matrix is used as the modulation wave of each channel.

[0010] Further, the six-phase park transformation matrix T j is:

[0011]

[0012] j is 5 or 7, corresponding to the transformation matrix of the fifth or seventh harmonic current.

[0013] Further, the six-phase park inverse transformation matrix T j -1 is:

[0014]

[0015] j is 5 or 7, corresponding to the transformation matrix of the fifth or seventh harmonic current.

[0016] Further, in step 2), the two sets of three-phase winding currents with a mutual difference of 30° are subjected to coordinate transformation by the formula (4) transformation matrix to obtain:

[0017]

[0018] Further, in step 2), the winding three-phase currents of the first and third channels are brought into the formula (5) to obtain the direct current of the one-three harmonic plane of the winding three-phase currents, which is i dj ( _s i u ( 5m 、 _ i d ), s5 i u_ ( m 1、 d i3) s );

[0019] The winding three-phase currents of the second and fourth channels are brought into the formula (5') to obtain the direct current of the two-four harmonic plane of the winding three-phase currents, which is i qj_sum (i q5_sum (i q5_sum13 、i q5_sum24 ),i q7_sum (i q7_sum13 、i q7_sum24 ))。

[0020] Compared with the prior art, the present application has the following advantages:

[0021] 1) Control is simple. The method does not need to increase any hardware circuit and offline test, simple, easy to realize, after park transformation of two sets of three-phase currents of the multiphase motor with a mutual difference of 30°, the modulation wave of each channel can be obtained by inverse transformation according to the PI controller output to suppress the fifth and seventh harmonics;

[0022] 2) Strong universality. Combined with the characteristics of two sets of windings with a mutual difference of 30°, the park transformation and inverse transformation matrix based on the fifth and seventh harmonic planes are expanded from the three-phase circuit coordinate transformation theory, only the transformation matrix needs to be adjusted accordingly, and the related conclusions can be extended to multiple sets of multiphase motor systems, which has certain universality;

[0023] 3) Good suppression effect. Since the fifth and seventh harmonics become direct current after the new six-dimensional park transformation, the fundamental wave with a mutual difference of 30° is completely cancelled, and the PI current controller is used for adjustment, which can realize accurate suppression of the fifth and seventh harmonics of two sets of three-phase currents with a mutual difference of 30°, avoiding the problem that the harmonic components are difficult to separate and accurately remove in the conventional control method. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is the multiphase motor winding main circuit of the application;

[0025] Figure 2 is the multiphase motor five and seventh harmonic suppression closed-loop control block diagram of the application;

[0026] Figure 3 is the multiphase motor current five and seventh harmonic suppression simulation effect diagram at a speed of 200r / min (Fig. (a), (c), (e) and (g) are five and seventh harmonic suppression diagrams before suppression, and Fig. (b), (d), (f) and (h) are five and seventh harmonic suppression diagrams after suppression);

[0027] Figure 4 is the multiphase motor current five and seventh harmonic suppression experimental effect diagram at a speed of 200r / min (Fig. (a), (c), (e) and (g) are five and seventh harmonic suppression diagrams before suppression, and Fig. (b), (d), (f) and (h) are five and seventh harmonic suppression diagrams after suppression). DETAILED DESCRIPTION

[0028] The application will be further described below in combination with the drawings and specific embodiments.

[0029] A twelve-phase propulsion system composed of a twelve-phase frequency converter and a propulsion motor is taken as the research object, and the matched twelve-phase motor winding schematic diagram is shown in Figure 1 , which is composed of four sets of three-phase windings with a mutual difference of 15°.

[0030] Four sets of three-phase currents i hm Twelve-phase current is obtained by collecting respectively, h takes a, b, c, which represents a set of three-phase current, m takes 1, 2, 3, 4, which represents channel one to channel four current respectively; taking the first and third channels of two sets of three-phase currents with a phase difference of 30° as an example, when the twelve-phase motor contains five and seven harmonics, the three-phase current of the first and third channels is shown as formula (1) and formula (2):

[0031]

[0032] I1 is the amplitude of the fundamental, I5 is the amplitude of the fifth harmonic, I7 is the amplitude of the seventh harmonic, ω is the electrical angular velocity, and t is the time.

[0033] In order to suppress the five and seven harmonics, the first and third two sets of three-phase windings with a phase difference of 30° are taken as a whole, and the second and fourth two sets of three-phase windings with a phase difference of 30° are taken as a whole, and the five and seven harmonic quantities of the two sets of three-phase currents with a phase difference of 30° are subjected to six-phase park transformation matrix transformation to obtain direct current, and then proportional integral PI regulator is used for control.

[0034] And for multi-phase or even arbitrary phase park transformation, the derivation principle is extended from three-phase park transformation, and the coordinate transformation matrix of generalized park transformation can be expressed as:

[0035]

[0036] The matrix theoretical explanation is:

[0037] If the state signal quantity of an n (n≥3) phase circuit is represented in the natural coordinate system as And it can be represented in the rotating coordinate system as Then y=C(θ)x, k=1, 2…n-1, u, w are positive integers, u<w. Wherein, α=2π / n, which is the electrical angle between every two sets of windings, C(θ) is the coordinate transformation matrix, θ is the phase angle of the corresponding state quantity in the natural coordinate system. The value of w is related to the number of phases of the motor, when n is odd, w=(n-1) / 2, and the last row is removed; when n is even, w=n / 2-1, and the last row is kept. The last two rows correspond to zero sequence components. In addition, the coefficient in formula (3) is obtained by taking power invariable as the constraint condition, when taking amplitude invariable as the constraint condition, only the coefficient in formula (3) needs to be modified as 2 / n.

[0038] Obviously, only the five and seven harmonic currents of a single channel three-phase winding meet the n-phase current condition. But if two sets of three-phase winding currents i abc1 and iabc3 The combination can meet the condition of multiple-phase symmetry of the sinusoidal signal. Therefore, the application adopts a six-phase park transformation matrix based on the fifth and seventh harmonic planes, performs synchronous coordinate transformation on two sets of three-phase windings with a mutual difference of 30° on the fifth and seventh planes, realizes decoupling of the fifth and seventh harmonics, makes the fifth and seventh harmonics project as direct currents in the respective dq planes, and then controls by using a PI regulator. The six-phase park transformation matrix T j As shown in formula (4):

[0039]

[0040] θ is the electric angle of the dq rotating coordinate system.

[0041] The coordinate transformation on the currents of the two sets of three-phase windings with a mutual difference of 30° by using the transformation matrix of formula (4) can obtain:

[0042]

[0043]

[0044] The value of j in formula (4) and formula (5) is 5 and 7, which respectively correspond to the transformation matrix of the fifth and seventh harmonic currents. The currents of formula (1) and formula (2) are respectively substituted into formula (5) and (5'), and the matrix multiplication criterion is used to calculate, and the following results can be obtained:

[0045]

[0046] In the above formula, i d_sum13 , i q_sum13 refers to the d-axis and q-axis currents of the fundamental wave plane obtained by the six-phase park transformation matrix formula (4) on the winding phase currents of the first and third channels of the twelve-phase open-winding motor, i d5_sum13 , i q5_sum13 refers to the d-axis and q-axis currents of the fifth harmonic plane, i d7_sum13 , i q7_sum13 refers to the d-axis and q-axis currents of the seventh harmonic plane. i d5_1 refers to the d-axis current of the fifth harmonic plane of the first set of winding currents, i q5_1 refers to the q-axis current of the fifth harmonic plane of the first set of winding currents, i d5_3 refers to the d-axis current of the fifth harmonic plane of the third set of winding currents, i q5_3 refers to the q-axis current of the fifth harmonic plane of the third set of winding currents; i d7_1 refers to the d-axis current of the seventh harmonic plane of the first set of winding currents, i q7_1 refers to the q-axis current of the seventh harmonic plane of the first set of winding currents, i d7_3 refers to the d-axis current of the seventh harmonic plane of the third set of winding currents, iq7_3 denotes the third set of winding current in the seventh harmonic plane q-axis current; i d1_1 denotes the first set of winding current in the fundamental plane d-axis current, i q1_1 denotes the first set of winding current in the fundamental plane q-axis current, i d1_3 denotes the third set of winding current in the fundamental plane d-axis current, i q1_3 denotes the third set of winding current in the fundamental plane q-axis current; another 5 (7) times harmonic current in the 7 (5) times harmonic plane projection produces 12 times frequency components which can be suppressed by a low pass filter, which can be ignored here. Therefore, the above formula is further simplified to obtain:

[0047]

[0048] It can be found from formula (6) to (8) that when the six-phase park transformation matrix T k is adopted, the fundamental component, the fifth and seventh harmonic components and the zero sequence component in the winding are all transformed into direct current in the respective planes, and then PI regulator is adopted for suppression.

[0049] The output quantity obtained by the PI controller is calculated as the alternating current by the six-phase park inverse transformation matrix, and the fifth and seventh harmonic contents in the modulation wave are changed to suppress the fifth and seventh harmonic of the winding current. Taking the first and third channels of two sets of three-phase windings with a mutual difference of 30° as an example, the six-phase park inverse transformation matrix T j -1 as shown in formula (9):

[0050]

[0051] According to the above control strategy, since the twelve-phase motor can be regarded as four sets of three-phase windings with a mutual displacement of 15°, the six-phase park transformation and inverse transformation matrices corresponding to the second and fourth channels can be obtained by subtracting the phase difference of 15° between sets from the phase angle θ in the above T j and T j -1 Therefore, the first and third channels (with a phase difference of 30°) of three-phase windings can be regarded as a whole, and the second and fourth channels (with a phase difference of 30°) of three-phase windings can be regarded as a whole, and the above strategy is used for control respectively. In theory, the fifth and seventh harmonic currents of the motor can be effectively suppressed. The multi-phase motor five and seven harmonic suppression closed-loop control block diagram of the present application is shown in Figure 2 . As shown in the figure, the winding current of the twelve-phase open winding motor is divided into two groups of three channels and four channels, which are different by 30°, and the direct current in the respective harmonic planes can be obtained by the six-phase park transformation matrix (4) i dk_sum (i d5_sum (id5_sum13 , i d5_sum24 ), i d7_sum (i d7_sum13 , i d7_sum24 )) and i qk_sum (i q5_sum (i q5_sum13 , i q5_sum24 ), i q7_sum (i q7_sum13 , i q7_sum24 )) can be obtained by further adopting the PI regulator for suppression. dj * and u qj * (j is 5, 7), and then the direct current u d * and u q * The modulation wave u abc1 , u abc2 , u abc3 , u abc4 can be obtained through the inverse transformation matrix (9), so that the five and seven harmonic precise suppression of the two groups of four sets of three-phase windings with a difference of 30° of the twelve-phase motor can be realized.

[0052] The method will be applied to the twelve-phase motor system, Figure 3 and Figure 4 are respectively the simulation and experimental effect diagram of the five and seven harmonic current suppression of the multi-phase motor of the method at a speed of 200r / min. Through the simulation and experimental comparison results, it can be found that after adding the five and seven harmonic suppression algorithm, the five and seven harmonic content of the motor under the stable operation condition is reduced, which proves that the effective value of the fundamental current of the motor under the rated operating condition can be improved, and the algorithm can greatly improve the operating condition of the multi-phase induction motor.

[0053] The application is a five and seven harmonic suppression method suitable for multi-phase motors. The control strategy can suppress the five and seven harmonic currents by changing the five and seven harmonic components of the modulation wave, the regulation amount is calculated by the six-phase park transformation matrix and the PI controller, the method is simple in programming and strong in universality. The application can meet the five and seven harmonic suppression of the multi-phase motor, and can be extended to other harmonic suppression occasions of multiple sets of multi-phase electrical equipment.

Claims

1. A method of five, seven harmonic suppression suitable for twelve phase electric machines characterized by: The inhibition method is: 1) Twelve-phase propulsion system four sets of three-phase current is collected, and twelve alternating currents are obtained; 2) Two sets of three-phase windings with a phase difference of 30° are taken as a whole, and the fifth and seventh harmonic currents of the two sets of three-phase windings with a phase difference of 30° are transformed into direct currents by using a six-phase park transformation matrix; 3) The output of the direct current obtained by the PI regulator is combined with the direct current on the fundamental plane, and the alternating current calculated by using the six-phase park inverse transformation matrix is used as the corresponding modulation wave of each channel. The six-phase park transformation matrix T j is: j is 5 or 7, corresponding to the transformation matrix of the fifth or seventh harmonic current; and θ is the electric angle of the dq rotating coordinate system.

2. The method for five, seven harmonic suppression suitable for twelve phase electric machine as claimed in claim 1 wherein: The six-phase park inverse transformation matrix T j -1 is: j is 5 or 7, corresponding to the transformation matrix of the fifth or seventh harmonic current.

3. The method for five, seven harmonic suppression suitable for twelve phase electric machine as claimed in claim 1 wherein: In step 2), the two sets of three-phase winding currents with a phase difference of 30° are transformed by using the formula (4) transformation matrix for coordinate transformation to obtain: i d_sum13 i q_sum13 i d_sum24 i q_sum24 i hm i 0_1 i 0_2 i 0_3 i 0_4 i 4. The method for five, seven harmonic suppression suitable for twelve phase electric machine as claimed in claim 3 wherein: In the step 2), the direct current of the three-phase current of the winding of the first and third channels into a three-channel harmonic plane in formula (5) is i dj_sum (i d5_sum (i d5_sum13 、i d5_sum24 ),i d7_sum (i d7_sum13 、i d7_sum24 )) The second, fourth channel winding three-phase current into the formula (5') two four channel harmonic plane straight flow is i qj_sum (i q5_sum (i q5_sum13 、i q5_sum24 ),i q7_sum (i q7_sum13 、i q7_sum24 )); wherein, i d5_sum13 , i q5_sum13 denotes the d, q-axis current of the twelve-phase open-winding electric machine in the fifth harmonic plane of the first, third channel, i d7_sum13 , i q7_sum13 denotes the d, q-axis current of the twelve-phase open-winding electric machine in the seventh harmonic plane of the first, third channel; i d5_sum24 , i q5_sum24 denotes the d, q-axis current of the twelve-phase open-winding electric machine in the fifth harmonic plane of the second, fourth channel, i d7_sum24 , i q7_sum24 denotes the d, q-axis current of the twelve-phase open-winding electric machine in the seventh harmonic plane of the second, fourth channel.

Images