Direct-current bus current ripple suppression method for six-phase open winding motor driving system

Abstract

The invention discloses a direct current bus current ripple suppression method for a six-phase open winding motor driving system. A switch sequence with a zero-sequence current suppression function is reordered, on the basis, phase shifting of a plurality of switching periods can be carried out on the switch sequence according to two different phase shifting modes, pulses generated by the switch sequence which is sequenced firstly and then subjected to phase shifting act on four sets of inverters, no filter circuit is used, and therefore the frequency conversion efficiency of the inverter is improved. And the direct current bus current ripples are suppressed by adjusting the switch sequence in a full modulation range by staggering overlapping of valley values and peak values.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronics and power transmission, and particularly relates to a DC bus current ripple suppression method for a six-phase open-winding motor driving system. BACKGROUND

[0002] In order to reduce the DC bus current ripple, a filter circuit with corresponding capacity can be designed, but this will cause the DC bus power supply to be too large in size and too high in cost, and increase the risk of potential failure due to damage of the filter circuit; without increasing the filter circuit, some methods of rearranging the bus current through software are proposed to suppress the bus current ripple.

[0003] However, the prior art still has deficiencies, first, increasing the filter circuit will greatly increase the manufacturing cost and complexity of the DC bus power supply, and the filter circuit will increase the risk of failure of the DC bus power supply; second, the existing method of rearranging the bus current is for multi-phase motors or three-phase open-winding motors, but for six-phase open-winding motors, the control dimension increases, and the suppression of the bus current ripple becomes more flexible, and there is currently no method that can well suppress the bus current ripple of the six-phase open-winding motor driving system. SUMMARY

[0004] (I) Technical problems solved

[0005] In view of the deficiencies in the prior art, the present application proposes a DC bus current ripple suppression method for a six-phase open-winding motor driving system, wherein the six-phase open-winding motor uses two sets of three-phase windings with a spatial angle difference of 30° to better suppress motor harmonics, uses four groups of three-phase two-level voltage source inverters as power devices to meet the characteristics of economy and commercialization, does not use a filter circuit, and comprehensively uses sequencing and phase-shifting methods, combined with the flexible characteristics of the six-phase open-winding motor control dimension, proposes a comprehensive suppression method of sequencing first and then phase-shifting to suppress the bus current ripple, so as to better and more safely play the advantages of low-voltage and high-power of the six-phase open-winding permanent magnet synchronous motor.

[0006] (II) Technical solutions

[0007] To achieve the above purpose, the present application is implemented by the following technical solutions:

[0008] A DC bus current ripple suppression method for a six-phase open-winding motor driving system, comprising:

[0009] When using five-segment space vector pulse width modulation technology to generate PWM, compared with seven-segment space vector pulse width modulation technology, the five-segment DC current pulsation frequency is equal to the switching frequency because only one zero vector is selected, while the seven-segment DC current pulsation frequency is equal to twice the switching frequency because two zero vectors are selected;

[0010] For a three-phase open-winding motor with a common DC bus, when the inverters at both ends of the ABC windings use 180-degree opposite voltage vectors to synthesize the total voltage vector form, the DC bus current waveforms of the inverters at both ends are completely consistent. This will cause the peak and valley values ​​of the DC bus current on both sides to completely overlap, resulting in an excessively large peak value of the synthesized DC bus current and zero valley value, which in turn causes greater bus current fluctuations.

[0011] Considering that the bus current ripple of the above method is too large, the sorting method is used to rearrange the bus currents of the inverters at both ends. The inverter 12 side arranges it with high on both sides and low in the middle, and the inverter 13 side arranges it with high in the middle and high on both sides. At this time, the combined bus current of the two avoids the peak overlap.

[0012] Considering that this article is targeting a six-phase open-winding motor with a common DC bus, the DC bus current arrangement of the DEF winding is the same as that of the ABC winding;

[0013] When the two sets of windings jointly synthesize the DC bus current, peak value overlap and valley value overlap will inevitably occur again, resulting in excessive total bus current ripple. At this time, since the switching mode of the inverter at both ends of the two sets of windings has been determined by the sorting method, the vector action time of the switching tube can no longer be adjusted. Therefore, the phase shifting method is used to shift the phase of one of the windings for several switching cycles (0.5 cycle phase shift for five-segment space vector pulse width modulation, 0.25 cycle phase shift for seven-segment space vector pulse width modulation), and the valley value of the DC bus current generated by the ABC winding is overlapped with the non-zero value of the DC bus current of the DEF winding to achieve the staggered valley value overlap, so as to achieve the purpose of comprehensive suppression of the bus current.

[0014] The beneficial effects of the present invention are as follows:

[0015] A proposed method for suppressing the DC bus current ripple in a six-phase open-winding motor drive system does not add any filtering circuits compared to traditional methods, reducing the manufacturing cost and volume of the electric drive system and improving the system safety to a certain extent. At the same time, combining the flexibility and variability of the six-phase open-winding motor, a comprehensive suppression method of first sequencing and then phase shifting is used to greatly suppress the bus current ripple and increase the service life of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1This is the schematic diagram of a six-phase open-winding permanent magnet synchronous motor drive system based on a common DC bus;

[0017] Figure 2 The voltage and current waveforms during the normal operation of the motor;

[0018] Figure 3 This is a schematic diagram of the synthesis of the voltage space vector of the open-winding motor;

[0019] Figure 4 Schematic diagram of the synthesis of DC side currents generated by the ABC winding inverter 12;

[0020] Figure 5 Schematic diagram of the synthesis of DC side current generated by the ABC winding inverter 13;

[0021] Figure 6 Schematic diagram of the synthesis of DC bus current generated by the sequencing method for the ABC winding inverter;

[0022] Figure 7 Schematic diagram of the synthesis of the DC side current generated by the DEF winding inverter 14;

[0023] Figure 8 Schematic diagram of the synthesis of the DC side current generated by the DEF winding inverter 15;

[0024] Figure 9 Schematic diagram of the synthesis of DC bus current generated by the DEF winding inverter using the sorting method;

[0025] Figure 10 This is a schematic diagram of the DC bus current when only the ABC winding and the DEF winding are used in the sorting method;

[0026] Figure 11 The schematic diagram of the DC bus current composed of the ABC winding and the DEF winding using the method of first sequencing and then phase shifting is shown;

[0027] The reference numerals are explained as follows: 11 is a DC bus power supply, 12 is a three-phase inverter for winding ABC near the power supply end, 13 is a three-phase inverter for winding ABC far from the power supply end, 14 is a three-phase inverter for winding DEF near the power supply end, 15 is a three-phase inverter for winding DEF far from the power supply end, and 16 is a six-phase open-winding permanent magnet synchronous motor. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0029] In order to make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present invention and are not intended to limit the present invention. That is, the embodiments described herein are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and illustrated in the drawings herein can be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative work shall fall within the scope of protection of the present invention. It should be noted that relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0031] Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes 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. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0032] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0033] like Figure 1 As shown, a common DC bus type six-phase open-winding permanent magnet synchronous motor drive system includes a DC bus power supply 11, an ABC winding near-power-end inverter 12, an ABC winding far-power-end inverter 13, a DEF near-power-end inverter 14, a DEF far-power-end inverter 15, and a six-phase open-winding permanent magnet synchronous motor 16. The ABC winding near-power-end inverter 12, the six-phase open-winding permanent magnet synchronous motor ABC windings, and the ABC winding far-power-end inverter group 13 are connected in sequence; the DEF winding near-power-end inverter 14, the six-phase open-winding permanent magnet synchronous motor DEF windings, and the DEF winding far-power-end inverter 15 are connected in sequence; the inverters 12, 13, 14, and 15 are connected in parallel to the DC bus power supply terminal 11;

[0034] During the operation of the motor, each sampling cycle adopts the control method described below. Taking the control process of one sampling cycle as an example, during the normal operation of the motor, the phase current lags the phase voltage pi / 6, and both are sinusoidal waves, such as Figure 2 shown.

[0035] by Figure 2 Take point A as an example. At this time, the voltage phase is 3 / 4pi, and the three-phase voltages are 0.707U, 0.259U and -0.996U respectively, where U is the phase voltage amplitude. U is obtained by Clark transformation. α =0.717U, U β =0.724U. Therefore, if Figure 3 As shown, according to the space vector pulse width modulation process, the synthetic vector is in the state of Figure 3 In sector 1, the effective voltage vectors are 100 and 110. Under a modulation index of 0.433, the corresponding action time is: T 100 =0.112T s 、T 110 =0.30T s At this time, the phase currents at point A are 0.966I, -0.129I, and -0.707I respectively.

[0036] Based on the above data, the bus current ripple suppression method at point A is introduced in detail:

[0037] The bus current of the ABC winding is rearranged using the sorting method. When the inverters at both ends use voltage vectors with a 180° difference to synthesize the total voltage vector, the bus currents generated by inverter 12 and inverter 13 are respectively as follows: Figure 4 and Figure 5 As shown, it can be seen that the bus current synthesized by the inverters at both ends is the same. This situation will cause the peak and valley values ​​to completely overlap when the inverters at both ends synthesize the bus current, which will lead to excessive bus current ripple. In order to avoid the peak overlap, the bus current is rearranged. The bus current of inverter 12 is arranged as high on both sides and low in the middle, and the bus current of inverter 13 is arranged as high in the middle and low on both sides. Figure 6 As shown, the peak value has been staggered to the maximum extent;

[0038] The bus current of the DEF winding is rearranged using the sorting method. The bus current generated by inverter 14 and inverter 15 is as follows: Figure 7 and Figure 8 As shown, similar to the ABC winding, in order to avoid peak overlap, the bus current of the inverter 14 is arranged as high on both sides and low in the middle, and the inverter 15 is arranged as high in the middle and low on both sides, as shown in FIG. Figure 9It can be seen that the peak values of bus current generated by DEF winding are staggered to the maximum extent.

[0039] The bus current generated by ABC winding and DEF winding by using the phase-shifting method to avoid the coincidence of valley values is shown in Fig. 6. Figure 10 It can be seen that the valley values coincide, so the sorting method can only suppress the bus current of ABC winding or DEF winding, and cannot better suppress the ripple of six-phase open winding bus current. In order to stagger the valley values, the valley value of DC bus current generated by ABC winding is coincided with the non-zero value of DC bus current generated by DEF winding to achieve the staggering of valley value coincidence. This effect is achieved by shifting the phase of DEF winding by 0.25 cycle, and the result is shown in Fig. 7. Figure 11 It can be seen that compared with Fig. 5, Figure 10 the bus current ripple is suppressed to a greater extent.

[0040] The above description is only the preferred embodiments of the present application, and it should be understood that the present application is not limited to the forms disclosed herein, and should not be considered as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concepts described herein by using the above teachings or related art or knowledge. Any modification and change made by those skilled in the art without departing from the spirit and scope of the present application shall be within the protection scope of the appended claims of the present application.

Claims

1. A method for suppressing DC bus current ripple in a six-phase open-winding motor drive system, characterized in that: include: This patent optimizes the switching sequence of four sets of inverters of a six-phase open-winding motor. First, the switching sequence is reordered according to the position of the DC bus current peak generated by each set of inverters in each switching cycle, and the optimal sorting combination is selected to achieve the purpose of staggering the overlap of the DC bus current peaks at both ends of the winding; in order to further suppress the DC bus current ripple within the full modulation range, the reordered switching sequence is phase-shifted in two different ways. The first phase-shifting method simultaneously shifts the switching sequences of inverters (14) and (15) used by the DEF winding by 0.25 switching cycles; the second phase-shifting method shifts the switching sequence of inverter (13) used by the ABC winding by 0.5 switching cycles, and at the same time shifts the switching sequence of inverter (14) used by the DEF winding by 0.25 switching cycles and the switching sequence of inverter (15) by 0.75 switching cycles. Both methods can avoid valley overlap and achieve the purpose of further suppressing the DC bus current ripple. The bus current generated by each group of inverters can be centered in the high bus current area or the low bus current area by reordering the switching sequence. The optimal combination can minimize the overlap of peak currents. Considering that the sum of the DC bus currents generated by the two sets of windings still has valley overlap after the peak values ​​are offset, there are two phase-shifting methods for the switching sequence that can further avoid valley overlap. The resulting switching sequence can maximize the suppression of DC bus current ripple within the full modulation range.

2. The method for suppressing DC bus current ripple of a six-phase open-winding motor drive system according to claim 1, characterized in that: All switching sequences of the obtained ABC winding and DEF winding are reordered as follows: The switching sequences of the four sets of inverters of the six-phase open-winding motor are rearranged according to the positions of the higher DC bus current areas to obtain 16 sorting combinations, among which the switching sequences of the higher DC bus current areas of inverters (12) and (14) are arranged on both sides, and the switching sequences of the higher DC bus current areas of inverters (13) and (15) are arranged in the middle, which can maximize the avoidance of the overlap of the DC bus current peaks.

3. The method for suppressing DC bus current ripple of a six-phase open-winding motor drive system according to claim 1, characterized in that: The specific phase shifting of the DEF winding inverter switching sequence is: There are two phase shifting modes for the reordered switching sequence. The first is to perform a phase shift of 0.25 switching cycles on the switching sequences of the inverters (14) and (15) of the DEF winding. The second is to perform a phase shift of 0.5 switching cycles on the switching sequence of the inverter (13) of the ABC winding, while performing a phase shift of 0.25 switching cycles on the switching sequence of the inverter (14) of the DEF winding and a phase shift of 0.75 switching cycles on the switching sequence of the inverter (15). These two phase shifting modes make the valley value of the DC bus current generated by the ABC winding coincide with the non-zero value of the DC bus current of the DEF winding to achieve the effect of staggered valley value coincidence. Applying the switching sequence that is first ordered and then phase shifted to the inverter can achieve the purpose of suppressing the bus current ripple by staggering the peak value coincidence and the valley value coincidence within the full modulation range.

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