A method for regulating the magnetization of a DC-type memory motor based on specific zero vector allocation

Abstract

This invention belongs to the field of motor technology and discloses a method for adjusting the magnetization of a DC-controlled memory motor based on specific zero-vector allocation. During transient magnetization adjustment of the DC-controlled memory motor, this method uses a 180° decoupled voltage distribution method to split the voltage vector applied to the motor into two smaller voltage vectors with the same amplitude but opposite phases. These two smaller voltage vectors are then synthesized using two voltage source inverters. A zero-vector redistribution is made to modulate the two smaller voltage vectors, ensuring a constant voltage value applied to the magnetization winding. The H-bridge circuit is then controlled to apply a forward or reverse DC voltage to the magnetization winding, magnetizing or demagnetizing the permanent magnets in the DC-controlled memory motor. This solves the problem that traditional DC-controlled memory motors require an additional DC power supply with low utilization, ensuring that the DC-controlled memory motor does not experience magnetization or demagnetization during steady-state operation.

Description

Technical Field

[0001] This invention belongs to the field of motor technology, specifically relating to a method for adjusting the magnetization of a DC magnetization-adjustable memory motor based on a specific zero vector allocation. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) have rapidly developed due to their high efficiency, high power density, and fast dynamic response, and have been widely used in aerospace, electric vehicles, and home appliances. However, due to the high coercivity of permanent magnet materials (such as neodymium iron boron), the air gap magnetic field of traditional PMSMs remains essentially constant, posing a challenge to field weakening speed regulation in the high-speed range. During field weakening speed regulation, not only are additional excitation losses incurred, but operating efficiency in the high-speed range is also reduced, and heat generation issues arise, affecting motor parameters. Therefore, adjustable flux permanent magnet motors, aiming to achieve effective adjustment of the air gap magnetic field, have always been a hot topic and a difficult area in motor research. Variable flux magnet memory motors (VFMMs) use low-coercivity permanent magnets. These permanent magnets can change their magnetization state through a tuning current pulse and maintain that magnetization level after the tuning pulse disappears, thus truly achieving variable flux.

[0003] Based on the method of generating the magnetomotive force (MMF), VFMMs can be divided into AC-modulated VFMMs and DC-modulated VFMMs. AC-modulated VFMMs typically use a magnetizing current pulse applied to the d-axis for magnetization. However, since the d-axis current may not be zero during actual operation, unexpected demagnetization may occur. DC-modulated VFMMs usually use a separate magnetizing winding to adjust the magnetization state of the low-coercivity permanent magnet. Its advantage is that the armature winding and the magnetizing winding are independent, facilitating online magnetization control. However, this often results in a more complex motor structure. An additional DC power supply is required to power the magnetizing winding. Since the DC power supply only operates during magnetization, this method suffers from high cost and low DC power utilization.

[0004] An open-winding electric machine (OWEM) system opens the motor's neutral point and uses dual-sided inverters for power supply, which can double the system's output voltage. Furthermore, OWEM systems offer good fault tolerance, flexibility, and adaptability. The topologies of OWEMs can generally be categorized into common DC bus, isolated DC bus, and hybrid power supply types. A common DC bus requires only one power source to power two inverters, reducing system size and cost, and allowing independent control of the three-phase windings. However, its structure contains a zero-sequence path, which can generate a large zero-sequence current even with small zero-sequence excitation, causing additional losses and torque ripple, ultimately reducing system efficiency and stability. An isolated DC bus requires two DC power sources, increasing the cost of the motor system, but the amplitude of the two DC power sources is arbitrary and can be flexibly adjusted to control the motor. This structure also eliminates the zero-sequence current path, so even with zero-sequence voltage excitation, no zero-sequence current will be generated. The hybrid power supply structure uses only one power source and has no zero-sequence path. Its basic operating idea is to allow the inverter connected to the capacitor to only handle reactive power and increase the required voltage level without using an additional DC power source. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for adjusting the magnetization of a DC-modulated memory motor based on a specific zero-vector allocation. This method solves the problems of existing DC-modulated memory motors requiring an additional DC power supply with low utilization, as well as the unexpected magnetization or demagnetization that occurs during steady-state operation.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for adjusting the magnetization of a DC-controlled magnetization memory motor based on specific zero-vector allocation is disclosed. This method involves using a 180° decoupled voltage allocation to split the voltage vector applied to the DC-controlled magnetization memory motor into two smaller voltage vectors with the same amplitude but opposite phases during transient magnetization. These two smaller voltage vectors are then synthesized using two voltage source inverters. By modulating the two smaller voltage vectors to redistribute the zero vector, the voltage applied to the magnetization winding is kept constant. Forward or reverse DC voltages are applied to the magnetization winding by controlling the switching of power electronic devices in the H-bridge circuit, thereby magnetizing or demagnetizing the low-coercivity permanent magnets in the DC-controlled magnetization memory motor.

[0008] Furthermore, the topology of the magnetization method includes a first voltage source inverter, a second voltage source inverter, and an H-bridge circuit; the input power supply is directly connected to the DC bus of the first voltage source inverter and the second voltage source inverter, and the output terminals of the first voltage source inverter and the second voltage source inverter jointly power the DC magnetization type memory motor; at the same time, any one of the outputs of the first voltage source inverter and the second voltage source inverter supplies power to the H-bridge circuit of the magnetization winding.

[0009] Furthermore, the switching status of the power electronic devices in the H-bridge circuit is determined by the magnetization operation required by the DC magnetization type memory motor and the sector to which the synthesized voltage vectors of the first voltage source inverter and the second voltage source inverter belong.

[0010] Furthermore, the zero-vector allocation is a voltage allocation method based on 180° decoupling, employing a specific zero-vector allocation method that uses zero-vector modulation with a switching mode of 000 in three sectors and zero-vector modulation with a switching mode of 111 in another three sectors.

[0011] Furthermore, when the DC-modulated memory motor needs to be magnetized, the H-bridge circuit is controlled to apply a positive DC voltage to the magnetizing winding.

[0012] Furthermore, when the DC-modulated memory motor needs to be demagnetized, the H-bridge circuit is controlled to apply a reverse DC voltage to the magnetizing winding.

[0013] Furthermore, the magnetization method is only applicable to the transient magnetization process of the DC magnetization-adjustable memory motor, while the H-bridge circuit does not participate in the steady-state operation of the DC magnetization-adjustable memory motor.

[0014] The beneficial effects of this invention are:

[0015] 1. The magnetization method provided by this invention can solve the problem that traditional DC magnetization type memory motors require an additional DC power supply and the utilization rate of the DC power supply is low, and can also ensure that the DC magnetization type memory motor will not experience accidental magnetization or demagnetization during steady-state operation.

[0016] 2. The topology provided by this invention can reduce the power level of power electronic devices and improve the utilization rate of DC voltage.

[0017] 3. The specific zero-vector allocation method proposed in this invention can minimize the number of switching operations of the power electronic switching devices on the H-bridge under the condition of constant DC output voltage, thereby reducing the loss of power electronic devices and extending their lifespan. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a topological diagram of the overall structure of the present invention;

[0020] Figure 2 This is a structural diagram of the H-bridge switch of the present invention;

[0021] Figure 3 This is a schematic diagram of the voltage distribution principle of the present invention;

[0022] Figure 4 This is a schematic diagram of the H-bridge magnetization operation switch of the present invention;

[0023] Figure 5 This is a schematic diagram of the H-bridge demagnetizing operation switch of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In the description of this invention, it should be understood that the terms "opening", "upper", "lower", "thickness", "top", "middle", "length", "inner", "around", etc., which indicate orientation or positional relationship, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting this invention.

[0026] like Figure 1-5As shown, this invention provides a magnetization method for a DC-controlled memory motor based on specific zero-vector allocation. During transient magnetization of the DC-controlled memory motor, this method employs a 180° decoupled voltage distribution to split the voltage vector applied to the motor into two smaller voltage vectors with the same amplitude but opposite phases. These two smaller voltage vectors are then synthesized using two voltage source inverters. By modulating the two smaller voltage vectors to make a specific zero-vector redistribution, the voltage applied to the magnetization winding is kept constant. Forward or reverse DC voltages are applied to the magnetization winding by controlling the switching of power electronic devices in the H-bridge circuit, thus magnetizing or demagnetizing the low-coercivity permanent magnets in the DC-controlled memory motor. This magnetization method solves the problem of traditional DC-controlled memory motors requiring an additional DC power supply with low utilization, and also ensures that the DC-controlled memory motor does not experience accidental magnetization or demagnetization during steady-state operation.

[0027] The topology of this magnetization method includes a first voltage source inverter VSC1, a second voltage source inverter VSC2, and an H-bridge circuit. The input power supply Udc is directly connected to the DC bus of the first voltage source inverter VSC1 and the second voltage source inverter VSC2. The output terminals of the first voltage source inverter VSC1 and the second voltage source inverter VSC2 together power the DC magnetization type memory motor. Simultaneously, points A1 and A2 of the output terminals of the first voltage source inverter VSC1 and the second voltage source inverter VSC2 are used to power the H-bridge circuit of the magnetization winding. This topology can reduce the power rating of power electronic devices and improve the utilization rate of DC voltage.

[0028] The switching status of the power electronic devices in the H-bridge circuit is determined by the magnetization operation required by the DC magnetization type memory motor and the sector to which the synthesized voltage vectors of the first voltage source inverter and the second voltage source inverter belong. In other words, different switching statuses of the H-bridge power electronic devices can satisfy the requirement of applying a forward or reverse DC voltage to the magnetization winding.

[0029] Specific zero-vector allocation is a voltage allocation method based on 180° voltage vector decoupling. It employs a specific zero-vector allocation method that uses zero-vector modulation with a switching mode of 000 in three sectors and zero-vector modulation with a switching mode of 111 in another three sectors. This zero-vector allocation method ensures that the two bridge arms used for magnetization in the two inverters will not have the same switching condition, and can significantly reduce the number of switching operations of power electronic devices in the H-bridge circuit. This ensures that the output common-mode voltage value will not be 0, thereby ensuring that the single-phase common-mode voltage output is a constant value.

[0030] The working principle of the topology proposed in this invention will be further explained below. The magnetization method of this invention adopts a 180° decoupled voltage distribution method, which maximizes the modulation range of the voltage vector.

[0031] like Figure 2 and Figure 3 As shown, assuming the voltage vector is located in the first sector, a 180° decoupled voltage distribution method is used, splitting the voltage vector into two smaller voltage vectors with the same amplitude but opposite phases. These two smaller voltage vectors are then synthesized by two voltage source inverters. If the smaller voltage vector to be synthesized by the first voltage source inverter is located in the first sector, then the smaller voltage vector to be synthesized by the second voltage source inverter is located in the fourth sector. Assume the power electronic switch in the voltage source inverter is 1 when on and 0 when off. Observation reveals that the effective voltage vector switching modes for modulating the voltage vector in the first sector are 100 and 110, meaning the switching modes of the A-phase bridge arm of the first voltage source inverter are S11 = 1 and S14 = 0. Simultaneously, the effective voltage vector switching modes for modulating the voltage vector in the fourth sector are 011 and 001, meaning the switching modes of the A-phase bridge arm of the second voltage source inverter are S21 = 0 and S24 = 1. Therefore, the common-mode voltage generated in phase A is the DC voltage value.

[0032] Meanwhile, since the remaining time of a sampling period, excluding the effective vector's action time, is supplemented by the zero vector, it can be adapted to the effective voltage vector according to the different switching modes of the two zero vectors, namely 000 and 111.

[0033] In this embodiment, since the voltage vector modulated by the first voltage source inverter is located in the first sector, the A-phase power electronic devices corresponding to its effective vector are all on with the upper bridge arm turned on and the lower bridge arm turned off. Therefore, the 111 switching mode is selected to supplement the remaining time within the zero vector period. Similarly, since the voltage vector modulated by the second voltage source inverter is located in the fourth sector, the A-phase power electronic devices corresponding to its effective vector are all off with the upper bridge arm turned on and the lower bridge arm turned on. Therefore, the 000 switching mode is selected to supplement the remaining time within the zero vector period. Thus, under this specific zero vector allocation method, the output A-phase common-mode voltage is a constant value, and this switching mode also leads to a significant reduction in the switching frequency of the power electronic devices in the H-bridge circuit.

[0034] It is worth noting that the situation where the composite vector is located in the first, second, fourth, and fifth sectors is the same as in this embodiment; however, it is slightly different when it is located in the third and sixth sectors. The allocation method of the zero vector remains unchanged, and only one type of zero vector can still be selected for supplementation. The only difference is that the switching frequency in the H-bridge circuit is increased.

[0035] The working principle of the H-bridge circuit required for this invention will be explained next. In the previous introduction about the specific zero vector allocation, it was explained how to generate a DC voltage with constant amplitude. Next, the H-bridge circuit is needed to maintain the generated DC voltage with constant amplitude in a specific direction.

[0036] When the DC magnetizing memory motor needs to be magnetized, the control H-bridge circuit applies a positive DC voltage to the magnetizing winding; when the DC magnetizing memory motor needs to be demagnetized, the control H-bridge circuit applies a reverse DC voltage to the magnetizing winding.

[0037] In this embodiment, the voltage vector is located in the first sector, the small voltage vector generated by the first voltage source inverter is located in the first sector, and the small voltage vector generated by the second voltage source inverter is located in the fourth sector. If the memory motor needs to be magnetized at this time, switches S1 and S4 are turned on, and switches S2 and S3 are turned off. At this time, a positive voltage is applied to the magnetizing winding, such as... Figure 4 As shown. If the memory motor needs demagnetization at this time, switches S1 and S4 are turned off, and switches S2 and S3 are turned on. At this time, a reverse voltage is applied to the magnetizing winding, such as... Figure 5 As shown.

[0038] It is worth noting that the magnetization method for DC magnetization-adjustable memory motors based on specific zero-vector allocation proposed in this invention is only for the transient magnetization process of DC magnetization-adjustable memory motors. In the steady-state operation of DC magnetization-adjustable memory motors, the H-bridge circuit does not participate in the operation, that is, the switching transistors of the H-bridge circuit are all in the off state. Since the transient process of DC magnetization-adjustable memory motors is very rapid in practical applications, the potential problems such as three-phase asymmetry caused by the topology required by this invention can be ignored.

[0039] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0040] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for adjusting the magnetization of a DC-controlled memory motor based on specific zero-vector allocation, characterized in that, This magnetization method involves using a 180° decoupled voltage distribution method to split the voltage vector applied to the DC magnetization memory motor into two smaller voltage vectors with the same amplitude but opposite phases during transient magnetization of the DC magnetization memory motor. These two smaller voltage vectors are then synthesized by two voltage source inverters. By modulating the two smaller voltage vectors to redistribute the zero vector, the voltage applied to the magnetization winding is kept constant. By controlling the switching of the power electronic devices in the H-bridge circuit, a forward or reverse DC voltage is applied to the magnetization winding to magnetize or demagnetize the low coercivity permanent magnet in the DC magnetization memory motor. The topology of the magnetization method includes a first voltage source inverter, a second voltage source inverter, and an H-bridge circuit; the input power supply is directly connected to the DC bus of the first voltage source inverter and the second voltage source inverter, and the output terminals of the first voltage source inverter and the second voltage source inverter jointly power the DC magnetization type memory motor; at the same time, either the output of the first voltage source inverter and the second voltage source inverter supplies power to the H-bridge circuit of the magnetization winding; The switching status of the power electronic devices in the H-bridge circuit is determined by the magnetization operation required by the DC magnetization type memory motor and the sector to which the synthesized voltage vectors of the first voltage source inverter and the second voltage source inverter belong. The zero-vector allocation is a voltage allocation method based on 180° decoupling, employing a specific zero-vector allocation method that uses zero-vector modulation with a switching mode of 000 in three sectors and zero-vector modulation with a switching mode of 111 in another three sectors. The magnetization method is only applicable to the transient magnetization process of the DC magnetization-adjustable memory motor. During the steady-state operation of the DC magnetization-adjustable memory motor, the H-bridge circuit does not participate in the operation.

2. The method for adjusting the magnetization of a DC magnetization-type memory motor based on specific zero-vector allocation according to claim 1, characterized in that, When the DC-modulated memory motor needs to be magnetized, the H-bridge circuit is controlled to apply a positive DC voltage to the magnetizing winding.

3. The method for adjusting the magnetization of a DC magnetization-type memory motor based on specific zero-vector allocation according to claim 1, characterized in that, When the DC-modulated memory motor needs to be demagnetized, the H-bridge circuit is controlled to apply a reverse DC voltage to the magnetizing winding.

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