JP2012055164A - Variable magnetic flux drive system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable magnetic flux drive system for driving a variable magnetic flux motor capable of improving variable magnet flux repetition accuracy and torque accuracy.SOLUTION: The variable magnetic flux drive system comprises a permanent magnet motor 1 which uses a permanent magnet, an inverter 4 which drives the permanent magnet motor, and magnetization means which flows magnetization current for controlling a permanent magnet flux. The permanent magnet is a variable magnet whose flux density can be made variable by magnetization current from the inverter 4. The magnetization means flows the magnetization current which is higher than or equal to a magnetization saturation region of a magnetic body of the variable magnet.

Description

  The present invention relates to a variable magnetic flux drive system.

  Instead of conventional induction motors (IM motors), permanent magnet synchronous motors (PM motors), which are excellent in efficiency and can be expected to be reduced in size and noise, are becoming popular. For example, PM motors are increasingly used as drive motors for railway vehicles and electric vehicles.

  The IM motor has a technical problem that a loss occurs due to the excitation current flowing because the magnetic flux itself is generated by the excitation current from the stator. On the other hand, since the PM motor is a motor that includes a permanent magnet in the rotor and outputs torque using the magnetic flux, there is no such problem that the IM motor has. However, the PM motor generates an induced voltage corresponding to the rotational speed because of its permanent magnet. In application fields with a wide rotation range such as railway vehicles and automobiles, it is a condition that the inverter that drives and controls the PM motor is not destroyed (due to overvoltage) by the induced voltage generated at the maximum rotation speed. In order to satisfy this condition, it is necessary to increase the withstand voltage of the inverter sufficiently, or conversely limit the magnetic flux of the permanent magnet provided in the motor. The former has an influence on the power supply side, and the latter is often selected. In some cases, the amount of magnetic flux in this case is about 1: 3 when compared with the amount of magnetic flux of the IM motor (in the case of an IM motor, the amount of gap magnetic flux created by the excitation current). In this case, in order to generate the same torque, it is necessary to flow a large (torque) current in a PM motor with a small amount of magnetic flux. This means that when the current that outputs the same torque in the low speed range is compared between the IM motor and the PM motor, the PM motor needs to pass a larger current. For this reason, the current capacity of the inverter that drives the PM motor is increased as compared with the IM motor. Further, since the switching frequency of the switching element in the inverter is high and the generated loss increases depending on the current value, a large loss and heat generation occur at a low speed in the PM motor.

  A train or the like may be expected to be cooled by the traveling wind, and if a large loss occurs at a low speed, the inverter device must be enlarged because of the need to improve the cooling capacity. Conversely, when the induced voltage is high, field-weakening control is performed. In this case, the efficiency is reduced by superimposing the excitation current.

  Thus, the PM motor has advantages and disadvantages due to the inherent magnet. As a motor, the benefits are significant, leading to loss reduction and miniaturization. On the other hand, in the case of variable speed control such as trains and electric cars, there are operating points that are less efficient than conventional IM motors. Exists. Further, since the current capacity and the loss increase for the inverter, the device size increases. Since the efficiency of the system itself is dominant on the motor side, the overall efficiency is improved by the application of the PM motor. On the other hand, an increase in the size of the inverter is a disadvantage of the system, which is not preferable.

  On the other hand, there is a variable magnetic flux drive system that can make the magnetic flux variable by the current from the inverter. Since this system can change the amount of magnetic flux of the permanent magnet according to the operating conditions, an improvement in efficiency can be expected as compared with a conventional PM motor drive system with a fixed magnet. Moreover, when a magnet is unnecessary, it is also possible to suppress an induced voltage as much as possible by reducing the amount of magnetic flux.

  However, since the BH characteristic (magnetization-magnetic flux density characteristic) of the variable magnet shows a steep response to the magnetizing current from the inverter, the magnetic flux tends to vary depending on the way of magnetization. In such a case, the torque repeatability is impaired, and a drive system with poor quality can be obtained.

US Pat. No. 6,800,077 US Pat. No. 5,977,679

  The present invention has been made in view of the above-described problems of the prior art, and is a variable magnetic flux drive system that drives a variable magnetic flux motor that can variably control the amount of magnetic flux by a magnetizing current from an inverter. It is an object of the present invention to provide a variable magnetic flux drive system that can improve the repeatability of the above and improve the torque accuracy.

  The present invention comprises a permanent magnet motor using a permanent magnet, an inverter for driving the permanent magnet motor, and a magnetizing means for passing a magnetizing current for controlling the magnetic flux of the permanent magnet, A variable magnet in which the magnetic flux density of the permanent magnet can be varied at least in part by the magnetizing current from the inverter, and the magnetizing means allows a magnetizing current to flow beyond the magnetization saturation region of the magnetic material of the variable magnet. Featuring a magnetic flux drive system.

  The present invention also provides a permanent magnet motor using a permanent magnet, an inverter for driving the permanent magnet motor, variable magnetic flux control means for passing a magnetizing current to control the magnetic flux of the permanent magnet, and the permanent magnet motor. Means for detecting current, and magnetic flux estimating means for estimating the amount of magnetic flux based on the voltage, current applied to the permanent magnet motor and winding inductance which is a motor parameter, and the permanent magnet has a magnetic flux of the permanent magnet. A variable magnetic flux drive system having a variable magnet whose density can be changed by a magnetizing current from the inverter at least in part.

  According to the variable magnetic flux drive system of the present invention, the variable magnetic flux motor can be driven while controlling the amount of magnetic flux of the variable magnet by the magnetizing current from the inverter, improving the repeatability of the magnetic flux of the variable magnet and increasing the torque accuracy. It can be improved.

1 is a block diagram of a variable magnetic flux drive system according to a first embodiment of the present invention. A simplified model diagram of a variable magnetic flux motor. Sectional drawing of the variable magnetic flux motor used in the 1st Embodiment of this invention. The BH characteristic view of the variable magnetic flux motor used in the 1st embodiment of the present invention. The BH characteristic figure of the permanent magnet of various materials. The block diagram which shows the internal structure of the magnetization request | requirement production | generation part in the 1st Embodiment of this invention. The block diagram which shows the internal structure of the variable magnetic flux control part 13 in the 1st Embodiment of this invention. The timing chart of variable magnetic flux motor control in the 1st embodiment of the present invention. Sectional drawing of the variable magnetic flux motor used with the variable magnetic flux drive system of the 2nd Embodiment of this invention. The BH characteristic view of two variable magnets employ | adopted for the variable magnetic flux motor used in the 2nd Embodiment of this invention. The block diagram which shows the internal structure of the variable magnetic flux control part in the 2nd Embodiment of this invention. The magnetization current table which the variable magnetic flux control part in the 2nd Embodiment of this invention refers. The block diagram of the variable magnetic flux drive system of the 3rd Embodiment of this invention. The block diagram which shows the internal structure of the variable magnetic flux control part in the 3rd Embodiment of this invention. The timing chart of the variable magnetic flux motor control in the 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a control block diagram of the variable magnetic flux drive system according to the first embodiment of the present invention. Before explaining the figure, a variable magnetic flux motor as a permanent magnet synchronous motor will be explained.

An image of the variable magnetic flux motor 1 is shown in FIG. The stator side may be considered the same as a conventional motor. On the rotor 51 side, as permanent magnets, there are a fixed magnet FMG whose magnetic flux density is fixed and a variable magnet VMG whose magnetic flux density is variable. The conventional PM motor is only the former fixed magnet FMG, whereas the variable magnetic flux motor 1 is characterized in that the variable magnet VMG is provided.

  Here, description is added about a fixed magnet and a variable magnet. A permanent magnet maintains a magnetized state in the state where no current flows from the outside, and the magnetic flux density does not change strictly under any condition. Even a conventional PM motor is demagnetized by passing an excessive current through an inverter or the like, or magnetized in reverse. Therefore, the permanent magnet means that the amount of magnetic flux is not constant and the magnetic flux density is not substantially changed by a current supplied from an inverter or the like in a state close to normal rated operation. On the other hand, the above-described permanent magnet having a variable magnetic flux density, that is, a variable magnet refers to a magnet whose magnetic flux density changes due to a current that can be passed through an inverter or the like even under the above operating conditions.

  Such a variable magnet can be designed within a certain range depending on the material and structure of the magnetic material. For example, recent PM motors often use neodymium (NdFeB) magnets with a high residual magnetic flux density Br. In the case of this magnet, since the residual magnetic flux density Br is as high as about 1.2 T, it is possible to output a large torque with a small device size, and it is suitable for a hybrid vehicle HEV or a train that requires a high output and a small motor. . In the case of a conventional PM motor, it is a requirement that it is not demagnetized by a normal current. However, this neodymium magnet (NdFeB) has a very high holding force Hc of about 1000 kA / m. It is an optimal magnetic material. This is because a magnet having a large residual magnetic flux density and a large coercive force is selected for the PM motor.

  Here, a magnetic material such as Alnico AlNiCo (Hc = 60 to 120 kA / m) or FeCrCo magnet (Hc = about 60 kA / m) having a high residual magnetic flux density and a small coercive force Hc is used as a variable magnet. The magnetic flux density (magnetic flux amount) of the neodymium magnet is almost constant due to the normal amount of current (meaning the amount of current flowing when the conventional PM motor is driven by the inverter), and the magnetic flux of a variable magnet such as an Alnico AlNiCo magnet The density (magnetic flux amount) is variable. Strictly speaking, since the neodymium magnet is used in the reversible region, the magnetic flux density fluctuates within a very small range, but returns to the original value when the inverter current disappears. On the other hand, since the variable magnet is used up to the irreversible region, the initial value is not obtained even if the inverter current is lost.

  FIG. 2 is a model of the variable magnetic flux motor 1 as a simple image. In the same figure, the amount of magnetic flux of the alnico magnet which is the variable magnet VMG is almost zero in the Q-axis direction only by changing the amount in the D-axis direction.

  FIG. 3 shows a specific configuration example of the variable magnetic flux motor 1. The rotor (rotor) 51 is configured such that a high coercivity permanent magnet 54 such as a neodymium magnet (NdFeB) and a low coercivity permanent magnet 53 such as an alnico magnet (AlNiCo) are combined in the rotor core 52. It is. The low coercive force permanent magnets 53 that are the variable magnets VMG are disposed on both sides of the magnetic pole part 55 of the rotor core 52 in the radial direction in the boundary area with the adjacent magnetic pole part 55. The high coercive force magnet 54 that is the fixed magnet FMG is arranged in a direction perpendicular to the diameter in the magnetic pole portion 55 of the rotor core 52. With this structure, the low coercive force permanent magnet 53, which is the variable magnet VMG, is magnetized by the D-axis current without being affected by the Q-axis current because the Q-axis direction and the magnetization direction thereof are orthogonal to each other.

  FIG. 4 illustrates the BH characteristics (magnetic flux density-magnetization characteristics) of the fixed magnet and the variable magnet. FIG. 5 shows only the second quadrant of FIG. 4 in a quantitatively correct relationship. In the case of a neodymium magnet and an Alnico magnet, there is no significant difference in their residual magnetic flux densities Br1 and Br2, but for the coercive forces Hc1 and Hc2, Hc1 of the Alnico magnet (AlNiCo) is equal to Hc2 of the neodymium magnet (NdFeB). From 1/15 to 1/8, the Hc1 of the FeCrCo magnet is 1/15.

  In the conventional PM motor drive system, the magnetization region due to the output current of the inverter is sufficiently smaller than the coercive force of the neodymium magnet (NdFeB), and is utilized in the reversible range of its magnetization characteristics. However, since the coercive force of the variable magnet is small as described above, it can be used in the irreversible region (even if the current is zero, it does not return to the magnetic flux density B before the current application) in the inverter output current range. Thus, the magnetic flux density (magnetic flux amount) can be made variable.

An equivalent simple model of the dynamic characteristics of the variable magnetic flux motor 1 is shown in equation (1). The model is a model on the DQ axis rotational coordinate system in which the D axis is given as the magnet magnetic flux direction and the Q axis is perpendicular to the D axis.

  Here, R1: winding resistance, Ld: D-axis inductance, Lq: Q-axis inductance, Φfix: amount of magnetic flux of the fixed magnet, Φvar: amount of magnetic flux of the variable magnet, and ω1: inverter frequency.

  FIG. 1 shows a main circuit and a control circuit of the variable magnetic flux drive system according to the first embodiment. The main circuit includes a DC power source 3, an inverter 4 that converts DC power into AC power, and a variable magnetic flux motor 1 that is driven by AC power of the inverter 4. The main circuit is provided with an AC current detector 2 for detecting motor power and a speed detector 18 for detecting motor speed.

  Next, the control circuit will be described. The inputs here are the operation command Run * and the torque command Tm *. The operation command generation unit 16 receives the operation command Run * and the protection signal PROT determined by the protection determination unit 17 and generates and outputs an operation state flag Run. Basically, when the operation command is entered (Run * = 1), the operation state flag Run is set to the operation state (Run = 1), and when the operation command instructs to stop (Run * = 0), The operation state flag Run is set to the stop state (Run = 0). Further, in the case of protection detection (PROT = 1), even if the operation command Run * = 1, the operation state is set to the stop state Run = 0.

  The gate command generation unit 15 receives the operation state flag Run, and generates and outputs a gate command Gst to the switching element included in the inverter 4. In the gate command generation unit 15, when the operation state flag Run changes from stop (Run = 0) to operation (Run = 1), the gate start (Gst = 1) is immediately started, and the operation state flag Run operates (Run = In the case of changing from 1) to stop (Run = 0), the gate is turned off (Gst = 0) after a predetermined time has elapsed.

The magnetic flux command calculation unit 12 receives the operating state flag Run and the inverter frequency ω1, that is, the rotor rotational frequency ωR, and generates and outputs a magnetic flux command Φ * as shown in the following equation (2), for example. That is, when the operation is stopped (Run = 0), the magnetic flux command Φ * is set to the minimum Φmin, the operation state (Run = 1), and the rotational frequency ωR is lower than the predetermined value, the magnetic flux The command Φ * is set to the maximum Φmax, and when the speed is higher than a predetermined value, the magnetic flux command Φ * is set to the minimum Φmin.

  Here, Φmin is the minimum amount of magnetic flux (> 0) that can be taken as the variable magnetic flux motor 1, Φmax is the maximum amount of magnetic flux that can be taken as the variable magnetic flux motor 1, and ωA is a predetermined rotational frequency. The setting of the magnetic flux amounts Φmin and Φmax will be described later in the variable magnetic flux controller 13.

The current reference calculator 11 receives the torque command Tm * and the magnetic flux command Φ * and calculates the D-axis current reference IdR and the Q-axis current reference IqR as in the following equations (3) and (4).

  The expressions (3) and (4) are arithmetic expressions assuming that the motor reluctance torque is not used and the number of motor poles is zero. Even a salient pole motor having a difference ΔL between the D-axis inductance Ld and the Q-axis inductance Lq may be a non-salient pole type motor having no difference.

However, it is effective to consider the reluctance torque when optimizing the efficiency and considering the maximum output at a predetermined current. In this case, for example, the calculation is performed as follows.

  Here, K is the ratio of the D-axis current and the Q-axis current, and is a value that varies depending on the application, such as the aforementioned efficiency optimization and maximum output. To optimize, it takes a function form and uses torque, speed, etc. as its arguments. In addition, simple approximation or a table can be used. Further, the magnetic flux command Φ * in the equation (5) can be operated even if a magnetic flux estimated value Φh described later is used.

  A detailed configuration of the magnetization request generator 29 is shown in FIG. The block of FIG. 6 is assumed to be controlled every predetermined time by the control microcomputer. The magnetic flux command Φ * is input to the previous value holding unit 31 and the value is held. The output of the previous value holding unit 31 is the previously stored magnetic flux command Φ *, and is input to the change determination unit 30 together with the current magnetic flux command value Φ *. The change determination unit 30 outputs 1 when there are two input changes, and outputs 0 when there is no change. That is, 1 is set only when the magnetic flux command Φ * changes. A circuit similar to the above is provided for the operation state flag Run instead of the magnetic flux command Φ *. The outputs of the two change determination units 30 and 34 are input to the logical sum operation unit (OR) 32, and the logical sum of these is output as the magnetization request flag FCreq.

  The magnetization request flag FCreq, which is the output of the magnetization request generation unit 29, becomes a magnetization request (FCreq = 1) when the magnetic flux command Φ * changes or when the operation state flag Run changes, otherwise there is no request ( FCreq = 0). The state in which the operation state flag Run changes is when the inverter starts, stops, or stops due to protection. Further, although the magnetic flux command Φ * is used here, the magnetization request FCreq may be generated by a change in a magnetization current command Im * (output of the magnetization current table 27) of the variable magnetic flux control unit 13 described later.

  A detailed configuration of the variable magnetic flux controller 13 is shown in FIG. The variable magnetic flux control unit 13 receives the magnetic flux command Φ * that is the output of the magnetic flux command calculation unit 12 and outputs a D-axis magnetization current difference amount ΔIdm * that corrects the D-axis current reference IdR. The generation of the magnetizing current difference amount ΔIdm * is performed by the following arithmetic processing.

  In order to magnetize the variable magnet VMG, a predetermined magnetization current command Im * may be obtained in accordance with the BH characteristics of the variable magnet shown in FIG. In particular, the magnitude of the magnetization current command Im * is set to be equal to or greater than H1sat in FIG. 4, that is, the magnetization saturation region of the variable magnet.

In order to flow the magnetization current to the magnetization saturation region, the magnetic flux amount Φmin and Φmax to be set by the magnetic flux command calculation unit 12 is set to the maximum (saturation) value of the fixed magnet with the magnetic flux (magnetic flux density) of the variable magnet being positive or negative. Is set as a value obtained by adding. If the positive maximum value of the magnetic flux amount of the variable magnet VMG is Φvarmax (assuming that the absolute value of the negative maximum value is equal to the positive maximum value) and the magnetic flux amount of the fixed magnet FMG is Φfix, the following equation is obtained.

  A magnetic current command Im * for obtaining the magnetic flux command Φ * is output from the magnetic current command 27 using the magnetic flux command Φ * as an input and the corresponding magnetizing current table 27 storing the magnetizing current.

Basically, since the magnetization direction of the magnet is the D axis, the magnetizing current command Im * is given to the D axis current command Id *. In the present embodiment, the D-axis current reference IdR, which is an output from the current reference calculation unit 11, is corrected with the D-axis magnetization current command difference ΔIdm * to obtain the D-axis current command Id *. 26, the D-axis magnetization current command ΔIdm * is obtained by the following equation.

  It is also possible to adopt a configuration in which the magnetizing current Im * is directly given to the D-axis current command Id * when switching the magnetic flux.

  On the other hand, the magnetization request flag FCreq is at least momentarily switched (FCreq = 1) when a request for switching the magnetic flux is made. In order to reliably change the magnetic flux, the magnetization request flag FCreq is input to the minimum on-pulse device 28. The magnetization completion flag (= 1: during magnetization = 0: magnetization completion), which is an output, has a function of not being turned off (= 0) for a predetermined time once turned on (= 1). . When the input is on (= 1) for a predetermined time, the output is turned off at the same time as it is turned off.

  The switch 23 receives a magnetization completion flag, and outputs the output of the subtractor 26 when the magnetization is in progress (magnetization completion flag = 1), and outputs 0 when the magnetization is complete (magnetization completion flag = 0).

  Based on the DQ-axis current commands Id * and Iq * generated as described above, the voltage command calculation unit 10 generates DQ-axis voltage commands Vd * and Vq * including a current controller so that a current matching the command flows. To do.

  The DQ axis voltage commands Vd * and Vq * of the voltage command calculation unit 10 are converted into three-phase voltage commands Vu *, Vv * and Vw * by the coordinate conversion unit 5, and the PWM circuit 6 is converted by the three-phase voltage command. A gate signal is generated by PWM, and the inverter 4 is PWM-controlled. The coordinate conversion unit 7 converts the AC detection currents Iu and Iw of the current detector 2 into two-axis DQ axes, converts them into DQ-axis current detection values Id and Iq, and inputs them to the voltage command calculation unit 10. Further, the pseudo-differentiator 8 obtains the inverter frequency ω1 from the signal from the speed detector 18. The voltage command calculation unit 10, the coordinate conversion units 5 and 7, and the PWM circuit 6 employ known techniques similar to those in the prior art.

  FIG. 8 shows an example of a timing chart of the operation of each signal. Here, although the protection signal is not raised (PROT = 0), the magnetization request flag is raised by the change of the operation state flag Run and the change of the magnetic flux command Φ *, and the magnetization completion flag for securing the predetermined time width is raised. The magnetization current command Im * has a value only during the period of the magnetization completion flag.

  With the above configuration, the present embodiment has the following operational effects. The variable magnetic flux motor 1 has a sudden characteristic change with respect to the magnetization caused by the inverter current, like the BH characteristic of FIG. For this reason, even if the same control is applied in practice, the same D axis and magnetic flux axis, which are likely to occur in position sensorless control, may not be exactly the same due to an axis deviation, a difference in current response, and individual motor differences. It is difficult to obtain the magnetic flux repeatedly. If the repetition accuracy of the magnetic flux is poor, the torque accuracy is deteriorated, which is not preferable.

  However, according to the variable magnetic flux drive system of the present embodiment, the variable magnetic flux amount after magnetization is determined by setting the magnetization current of the magnetization saturation region or more to flow in the magnetization characteristics of the variable magnet VMG. The repeatability can be improved, thus ensuring torque accuracy and improving drive reliability.

  In addition, according to the variable magnetic flux drive system of the present embodiment, since the minimum time for flowing the magnetizing current is set, it does not end in the halfway magnetization state, thereby making the variable after the magnetization processing variable. Variations in the amount of magnetic flux can be suppressed and torque accuracy can be improved.

(Second Embodiment)
A variable magnetic flux drive system according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 9 shows the structure of a variable magnetic flux motor 1A to be controlled in the variable magnetic flux drive system according to the second embodiment of the present invention. In the variable magnetic flux motor 1A in the present embodiment, the variable magnet VMG is composed of a pair of two different low coercive force permanent magnets as compared with the variable magnetic flux motor 1 in the first embodiment shown in FIG.

  That is, the rotor 51 includes a permanent coercive magnet 54 such as a neodymium magnet (NdFeB) and a low coercivity permanent magnet A53 such as a pair of alnico magnets (AlNiCo) in the rotor core 52. It is the structure arrange | positioned combining magnetic permanent magnet B56. The high coercive force magnet 54 that is the fixed magnet FMG is arranged in a direction perpendicular to the diameter in the magnetic pole portion 55 of the rotor core 52. One low coercive force permanent magnet A53, which is a variable magnet VMG, is arranged on both sides of the magnetic pole part 55 of the rotor core 52 in the radial direction in the boundary area with the adjacent magnetic pole part 55. The other low coercive force permanent magnet B56 is arranged closer to the center of the rotor 51 than the high coercive force permanent magnet 54 and in parallel. These two low coercive force permanent magnets A53 and B56 are the same magnetic body, and Alnico magnets (AlNiCo) are used as in the first embodiment.

  As described above, the variable magnet VMG is composed of the low coercive force permanent magnet A53 and the low coercive force permanent magnet B56, so that the same magnetic body is used, but the arrangement positions thereof are different. The magnetization action on the magnetization current differs between these two low coercivity permanent magnets A53 and B56. Therefore, a variable magnet structure having two BH characteristics as shown in FIG. 10 is obtained.

  In FIG. 10, there are two variable magnet curves C53 and C56 having different BH characteristics. The curves C53 and C56 of the two variable magnets are caused by arranging the alnico magnets of the same material at spatially different positions. Even if two low coercivity permanent magnets of different materials are used as a pair, the same two BH characteristics can be obtained. BH characteristics are the same for magnetic materials of the same material, but a difference occurs in the magnetic flux Φ with respect to the magnetization H caused by the current, depending on where the motor is arranged. FIG. 10 does not simply show the characteristics depending on the material, but shows the relationship between the magnetizing current from the inverter and the magnetic flux.

  In the case of this embodiment, the structure of the variable magnetic flux motor 1A is different from that of the first embodiment as described above, and the setting of the magnitude of the magnetizing current when changing the magnetic flux with respect to them is also the first. Different from the embodiment. In this embodiment, the configuration of the variable magnetic flux drive system is the same as that of the first embodiment shown in FIG. However, the functional configuration of the variable magnetic flux control unit 13 is as shown in FIG. 11 and is different from that of the first embodiment. Below, the detail of the variable magnetic flux control part 13 in this Embodiment is demonstrated.

  A variable magnet having a small coercive force is called a variable magnet A, and a magnet having a high coercive force is called a variable magnet B. Here, setting is made so that two magnetizing current commands Im_A and Im_B are given step by step.

  Im_A: A magnetization saturation region with respect to the variable magnet A, that is, near HcAsat, and a reversible region with respect to the variable magnet B.

  Im_B: The magnetization saturation region for both the variable magnet B and the variable magnet A, that is, near the HcBsat.

  The variable magnetic flux control unit 13 selects these two magnetizing current commands (there are positive and negative combinations) according to the required level of the magnetic flux command Φ * and gives it as the magnetizing current command Im *.

  The variable magnetic flux controller 13 calculates a magnetization current command Im * based on the magnetic flux command Φ *. The variable magnetic flux control unit 13 in the present embodiment has two arguments in the previous value holding unit 35 and the magnetizing current table 27 as compared to the first embodiment shown in FIG. Different. Here, the control process is repeated every predetermined time by the control microcomputer.

  The magnetic flux command Φ * and the magnetization request flag FCreq are input to the previous value holding unit 35. The magnetization request flag stores the magnetic flux command Φ * for each up edge. The output of the previous value holding unit 35 is the value of the magnetic flux command Φ * when the previous magnetization request flag becomes FCreq = 1, that is, the magnetic flux command value Φ * before the current magnetization process. Here, the previous magnetic flux command value is called Φ * old. The magnetization current table 27 receives the current magnetic flux command value Φ * and the previous magnetic flux command value Φ * old.

The magnetizing current table 27 is set as shown in the table of FIG. Assuming that the maximum magnetic flux of the variable magnet A53 is ΦvarAmax and the maximum magnetic flux of the variable magnet B56 is ΦvarBmax, the following four values can be taken as the magnetic flux command.

  As can be seen from the table of FIG. 12, the magnetization current table 27 is characterized in that, even when the same magnetic flux is obtained, the magnetization process, that is, the magnetization current differs depending on the previous state. In the table of FIG. 12, for example, the description “Im_B → −Im_A” in the case where the previous magnetic flux command value Φ * old = Φ2 and the current magnetic flux command value Φ * = Φ3 is first changed to Im * = Im_B. This indicates that the magnetizing process is performed and then the magnetizing process is performed as Im * = − Im_A. Simply, the magnetizing current command Φ * may be changed from Im_B to −Im_A according to time. However, in order to surely magnetize, firstly magnetizing at Im_B, the first embodiment Alternatively, as in a third embodiment to be described later, the magnetic flux command Φ * is changed to −Im_A when the magnetization is reliably completed, and the magnetization request flag is set again.

  According to the variable magnetic flux drive system of the present embodiment, by having two or more variable magnets A53 and B56 having different characteristics, only two magnetic flux amounts can be set with one variable magnetic flux. The amount of magnetic flux can be set to one level. In particular, since the setting of the magnetization current is set so as to be the magnetization reversible region and the saturation region, the value of any variable magnet does not become indefinite. Therefore, it is possible to set a magnetic flux with high repeatability with reproducibility, and torque accuracy can be improved. In addition, since a plurality of levels of magnetic flux values can be obtained in this way, it is possible to set a fine magnetic flux amount according to the operating condition, and it is possible to promote improvement in system efficiency, which is a feature of the variable magnetic flux motor. In the present embodiment, the combination of two variable magnets A and B is described, but a combination of three or more variable magnets is also possible.

(Third embodiment)
FIG. 13 shows a variable magnetic flux drive system according to a third embodiment of the present invention. In FIG. 13, elements common to the first embodiment shown in FIG. 1 are denoted by the same reference numerals.

  The variable magnetic flux drive system according to the present embodiment is different from the first embodiment shown in FIG. 1 in that the voltage commands Vd * and Vq * output from the voltage command calculation unit 10 and the DQ output from the coordinate conversion unit 7. The magnetic flux Φh is estimated using the shaft currents Id and Iq and the rotor rotational angular frequency ω1, and the magnetic flux estimator 9 is additionally provided to the variable magnetic flux controller 13. The variable magnetic flux controller 13 has the configuration shown in FIG. It is characterized by having.

The magnetic flux estimation unit 9 estimates the D-axis magnetic flux amount by the following equation based on the DQ-axis voltage commands Vd *, Vq *, the DQ-axis currents Id, Iq, and the rotor rotation angular frequency ω1 (inverter frequency).

  The estimated magnetic flux Φh is input to the variable magnetic flux controller 13 together with the magnetic flux command Φ * from the magnetic flux command calculator 12.

  A detailed configuration of the variable magnetic flux controller 13 in the present embodiment is shown in FIG. A subtractor 19 calculates a deviation between the magnetic flux command Φ * and the magnetic flux estimated value Φh, and the deviation is input to the PI controller 20. The magnetic flux command Φ * is input to the magnetizing current reference calculation unit 21. The magnetizing current reference calculation unit 21 calculates the magnetizing current command Im * by using a table so as to be magnetized by the magnetic flux corresponding to the magnetic flux command Φ *, or by applying it to a function formula. This characteristic is calculated based on the aforementioned BH characteristic. The adder 22 adds the output of the magnetizing current reference calculation unit 21 and the output of the PI control unit 20.

  This adder 22 becomes the magnetizing current command Im *. In order to magnetize, this magnetizing current command Im * is given as a D-axis current command Id *. Therefore, in the configuration of the present embodiment, the subtractor 26 subtracts the D-axis current reference IdR from the magnetization current command Im * so that Id * matches Im *, and the D-axis magnetization current command difference value ΔIdm *. Is calculated. Accordingly, the D-axis current reference IdR is added by the adder 14 in FIG.

  The switch 23 in the variable magnetic flux controller 13 selects two inputs based on a magnetization completion flag, which will be described later, and selects and outputs it as a magnetization current command Idm *. When the magnetization completion flag = 0 (magnetization completion), the D-axis magnetization current command difference ΔIdm * = 0. When the magnetization completion flag = 1 (in magnetization), the output of the adder 22 is output as ΔIdm *.

  The deviation between the magnetic flux command Φ * and the magnetic flux estimated value Φh, which is the output of the subtractor 19, is input to the magnetization completion determination unit 24. For example, the magnetization completion determination unit 24 outputs 1 when the absolute value of the magnetic flux deviation is smaller than a predetermined value α, and outputs 0 when larger than α. The flip-flop (RS-FF) 25 inputs the magnetization request flag FCreq to the input to the set S and the output of the magnetization completion determination unit 24 to the reset R side. The output of the RS-FF 25 is a magnetization completion flag and is input to the PI control unit 20 and the switch 23. If the magnetization completion flag is 0, the magnetization is completed, and if it is 1, the magnetization is in progress.

Further, the estimated magnetic flux value Φh that is the output of the magnetic flux estimating unit 9 is also input to the current reference calculating unit 11. In the current reference calculation unit 11, DQ-axis current references IdR and IqR are obtained by the following equations based on the estimated magnetic flux value Φh instead of the magnetic flux command Φ * in the calculation formula in the first embodiment.

  With the above configuration, the present embodiment has the following operational effects. When there is a magnetization request, the magnetization request flag = 1 stands for at least a moment. By setting the RS-FF 25, the magnetization completion flag = 1, that is, the magnetization is in progress. The switch 23 outputs the outputs from the PI controller 20 and the magnetization current reference calculation unit 21 as the magnetization current command Im *. The magnetizing current reference calculation unit 21 feeds a magnetizing current based on the BH characteristic grasped in advance so as to be magnetized by the magnetic flux command Φ *. Thereby, it is possible to instantaneously magnetize the vicinity of the command value, and the time required for magnetization is reduced, so that generation of unnecessary torque and loss can be suppressed. The BH characteristics can be obtained experimentally in advance.

  However, as described above, it is difficult to precisely match the magnetic flux to a predetermined value. Therefore, in the present embodiment, as shown in FIG. 15, the magnetizing current Im * is corrected so that the deviation of the magnetic flux approaches 0 by the action of the PI controller 20 in the variable magnetic flux control unit 13. As a result, the magnetic flux command Φ * and the magnetic flux estimated value Φh (that is, the actual magnetic flux if there is no estimation error) eventually coincide. For this reason, the accuracy of repetition of the magnetic flux amount in the magnetization process is improved, and the torque accuracy can be improved.

  Further, in the present embodiment, as shown in FIG. 15, in the magnetization completion determination unit 24 in the variable magnetic flux control unit 13, the magnetic flux substantially coincides with the magnetization because the absolute value of the magnetic flux deviation is within the predetermined value α. Is completed, the output is set to 1, and the RS-FF 25 receives this reset request and sets the output magnetization completion flag to 0. Therefore, the magnetization process can be completed when the estimated magnetic flux value surely matches the magnetic flux command Φ * that is the command. Thereby, according to this Embodiment, the repetition precision of the magnetic flux amount in a magnetization process improves, and the improvement of a torque precision can be anticipated.

  Further, according to the present embodiment, since the estimated magnetic flux Φh estimated from the voltage current is used to generate the DQ axis current references IdR and IqR, even if the amount of magnetic flux varies due to the magnetization process, The DQ axis current command is corrected. Since the DQ axis current flows in response to this command, it is possible to reduce the influence of the variation in the variable magnetic flux amount on the torque, and the torque accuracy is improved.

  Although the present embodiment is configured based on the estimated magnetic flux value, the magnetic flux estimator includes motor inductances such as Ld and Lq. These values vary depending on the magnetic saturation. In particular, in a variable magnetic flux motor, the magnetic saturation varies greatly depending on the amount of variable magnetic flux. Therefore, providing a function or table for outputting the motor inductance with the estimated value of the variable magnetic flux as an input is useful for improving the accuracy of estimating the magnetic flux and thus the torque accuracy.

  Moreover, even if the table is formed as described above, it may be difficult to accurately grasp the inductance characteristics. In that case, a magnetic flux detector constituted by a Hall element or the like is provided instead of estimating the magnetic flux, and the detected magnetic flux Φr is used in place of the magnetic flux estimated value Φh, thereby further improving the accuracy of magnetic flux estimation. As a result, torque accuracy can be improved.

DESCRIPTION OF SYMBOLS 1,1A Variable magnetic flux motor 2 Current detector 3 DC power supply 4 Inverter 5 Coordinate conversion part 6 PWM circuit 7 Coordinate conversion part 8 Pseudo-differentiator 9 Magnetic flux estimation part 10 Voltage command calculating part 11 Current reference calculating part 12 Magnetic flux command calculating part 13 Variable magnetic flux control unit 14 Adder 15 Gate command generation unit 16 Operation command generation unit 17 Protection determination unit 18 Position detector 19 Subtractor 20 PI controller 21 Magnetization current reference calculation unit 22 Adder 23 Switcher 24 Magnetization completion determination unit 25 RS flip-flop 26 Subtractor 27 Magnetization current table 28 Minimum on-pulse 29 Magnetization request generation unit 30 Change determination unit 31 Previous value holding unit 32 OR circuit 33 Previous value holding unit 34 Change determination unit 35 Previous value holding unit 51 Rotation Child 52 Rotor core 53 Low coercivity permanent magnet 54 High coercivity permanent magnet 55 Magnet of core Pole 56 Low coercivity permanent magnet

The present invention comprises a permanent magnet motor using a permanent magnet, an inverter for driving the permanent magnet motor, and a magnetizing means for passing a magnetizing current for controlling the magnetic flux of the permanent magnet, The permanent magnet has at least a part of a variable magnet whose magnetic flux density changes irreversibly due to the magnetizing current from the inverter, and the magnetizing means has a size equal to or larger than a region where the magnetic flux amount characteristics are saturated by the magnetizing current of the inverter . the magnetizing current, characterized in variable magnetic flux drive system in which with the ability to irreversibly change the flux density of the variable magnet by flow to the inverter.

The present invention also includes a permanent magnet motor using a permanent magnet, an inverter that drives the permanent magnet motor, and a magnetizing unit that flows a magnetizing current for controlling the magnetic flux of the permanent magnet, At least a part of the permanent magnet is provided with a variable magnet whose magnetic flux density can be changed by a magnetizing current from the inverter, and the magnetizing means has a magnetization larger than a region where the magnetic flux amount characteristics are saturated by the magnetizing current of the inverter. When the variable magnet is changed to a magnetic flux amount other than the maximum magnetic flux amount or the minimum magnetic flux amount, it is once magnetized to the maximum magnetic flux amount or the minimum magnetic flux amount. after, it characterized a variable magnetic flux drive system Ru is magnetized again to the desired amount of magnetic flux.

Such a variable magnet can be designed within a certain range depending on the material and structure of the magnetic material. For example, recent PM motors often use neodymium (NdFeB) magnets with a high residual magnetic flux density Br. In the case of this magnet, since the residual magnetic flux density Br is as high as about 1.2 T, it is possible to output a large torque with a small device size, and it is suitable for a hybrid vehicle HEV or a train that requires a high output and a small motor. . For conventional PM motor, but it is that the requirement is not demagnetized by normal current, because the neodymium magnet (NdFeB) has an extremely high coercive magnetic force Hc of about 1000 kA / m, a PM motor It is the most suitable magnetic material. This is because a magnet having a large residual magnetic flux density and a large coercive force is selected for the PM motor.

Here, the residual magnetic flux density is high, a small coercive magnetic force Hc alnico AlNiCo (Hc = 60~120kA / m) or FeCrCo magnetic such magnet (Hc = about 60 kA / m) of the variable magnet. The magnetic flux density (magnetic flux amount) of the neodymium magnet is almost constant due to the normal amount of current (meaning the amount of current flowing when the conventional PM motor is driven by the inverter), and the magnetic flux of a variable magnet such as an Alnico AlNiCo magnet The density (magnetic flux amount) is variable. Strictly speaking, since the neodymium magnet is used in the reversible region, the magnetic flux density fluctuates within a very small range, but returns to the original value when the inverter current disappears. On the other hand, since the variable magnet is used up to the irreversible region, the initial value is not obtained even if the inverter current is lost.

In other words, the rotor 51 is in the rotor core 52, a neodymium magnet (NdFeB) permanent magnet 54 having a high coercive force, such as two pair of alnico magnet (AlNiCo) permanent magnet 5 3 low coercivity such as, a structure disposed in combination with low-coercive-force permanent magnet 5 6. The high coercive force magnet 54 that is the fixed magnet FMG is arranged in a direction perpendicular to the diameter in the magnetic pole portion 55 of the rotor core 52. Variable While the low coercivity permanent magnet 3 is magnet VMG are on both sides of the magnetic pole portion 55 of the rotor core 52, are arranged in the radial direction in the boundary zone between the magnetic pole portion 55 adjacent, respectively. The other low coercive-force permanent magnet 5 6 toward the center of the rotor 51 than the high-coercive-force permanent magnets 54, and are arranged in parallel. These two low-coercive-force permanent magnet 3 and the low coercive force permanent magnet 5 6 have the same magnetic material, is used alnico magnet (AlNiCo) similar to the first embodiment.

Thus, by configuring the variable magnet VMG in the low coercivity permanent magnets 3 and low coercive force permanent magnet 5 6, but using the same magnetic material, it is made different and the positions Therefore, the magnetization effect on the D-axis magnetizing current is different between these two low coercivity permanent magnets 3 and low coercive force permanent magnet 5 6. Therefore, a variable magnet structure having two BH characteristics as shown in FIG. 10 is obtained.

The magnetizing current table 27 is set as shown in the table of FIG. When the maximum magnetic flux of the variable magnet A is ΦvarAmax and the maximum magnetic flux of the variable magnet B is ΦvarBmax, the following four values can be taken as the magnetic flux command.

According to the variable magnetic flux drive system of the present embodiment, by having two or more variable magnets A and B having different characteristics, one variable magnet can set only two magnetic flux amounts. The amount of magnetic flux can be set to one level. In particular, since the setting of the magnetization current is set so as to be the magnetization reversible region and the saturation region, the value of any variable magnet does not become indefinite. Therefore, it is possible to set a magnetic flux with high repeatability with reproducibility, and torque accuracy can be improved. In addition, since a plurality of levels of magnetic flux values can be obtained in this way, it is possible to set a fine magnetic flux amount according to the operating condition, and it is possible to promote improvement in system efficiency, which is a feature of the variable magnetic flux motor. In the present embodiment, the combination of two variable magnets A and B is described, but a combination of three or more variable magnets is also possible.

Claims (16)

A permanent magnet motor using a permanent magnet;
An inverter for driving the permanent magnet motor;
Magnetizing means for flowing a magnetizing current for controlling the magnetic flux of the permanent magnet,
The permanent magnet includes at least a part of a variable magnet in which the magnetic flux density of the permanent magnet can be varied by a magnetizing current from the inverter,
The variable magnetic flux drive system according to claim 1, wherein the magnetizing means has a capability of flowing a magnetizing current not less than a magnetization saturation region of the magnetic material of the variable magnet.   2. The variable magnetic flux drive system according to claim 1, wherein the variable magnet is configured by two or more variable magnets so that a saturation region becomes stepwise in view of a magnetization current of the inverter.   The variable magnetic flux drive system according to claim 2, wherein the two or more variable magnets are composed of two or more variable magnets having different coercive forces.   3. The variable magnetic flux drive system according to claim 2, wherein the two or more variable magnets are configured by two variable magnets arranged in a plurality of non-continuous regions of the rotor and having the same coercive force.   5. The variable magnetic flux drive system according to claim 1, wherein the magnetization means determines the magnitude of the magnetization current based on a magnetic flux amount before the magnetic flux change and a magnetic flux amount after the magnetic flux change. .   5. The variable magnetic flux drive system according to claim 1, wherein the magnetizing unit magnetizes the magnetic flux twice or more with different magnetizing currents. A permanent magnet motor using a permanent magnet;
An inverter for driving the permanent magnet motor;
Variable magnetic flux control means for flowing a magnetizing current to control the magnetic flux of the permanent magnet;
Means for detecting the current of the permanent magnet motor;
Magnetic flux estimation means for estimating the amount of magnetic flux based on the winding inductance which is the voltage, current and motor parameters applied to the permanent magnet motor,
The said permanent magnet has a variable magnet which can change the magnetic flux density of the said permanent magnet with the magnetizing current from the said inverter at least in part, The variable magnetic flux drive system characterized by the above-mentioned.   DQ-axis current correction means for correcting the D-axis current and the Q-axis current so that the output torque of the permanent magnet motor approaches a torque command based on the estimated magnetic flux amount estimated by the magnetic flux estimation means, The variable magnetic flux drive system according to claim 7.   9. The variable magnetic flux drive system according to claim 8, wherein the DQ axis current correction means corrects a DQ axis current command based on the estimated magnetic flux amount estimated by the magnetic flux estimation means.   8. The variable magnetic flux control means includes magnetizing current correcting means for adjusting a magnetizing current so that an estimated magnetic flux amount estimated by the magnetic flux estimating means coincides with a magnetic flux command value. Variable flux drive system.   The magnetizing current correcting means has a magnetizing current reference calculating means for calculating a magnetizing current reference necessary for obtaining the magnetic flux based on the magnetic flux command value, and the magnetizing current reference is a feedforward target current to the magnetizing current. The variable magnetic flux drive system according to claim 10.   The variable magnetic flux controller according to any one of claims 7 to 10, wherein the variable magnetic flux control means sets a minimum time for flowing the magnetizing current and controls so that a short magnetizing current within the minimum time does not flow. Magnetic flux drive system.   The variable magnetic flux control means completes the magnetization of the permanent magnet when a difference between the estimated magnetic flux amount estimated by the magnetic flux estimation means and the magnetic flux command value falls within a predetermined range. Item 11. The variable magnetic flux drive system according to any one of Items 7 to 10.   14. The variable magnetic flux drive system according to claim 7, wherein the magnetic flux estimation means estimates the magnetic flux amount by using a function or a table of the winding inductance for the variable magnet amount. . Instead of the magnetic flux estimating means for estimating the magnetic flux, the magnetic flux detecting means for detecting the magnetic flux is provided,
11. The variable magnetic flux control means controls the magnetization current using a magnetic flux detection value detected by the magnetic flux detection means instead of the estimated magnetic flux amount estimated by the magnetic flux estimation means. The variable magnetic flux drive system according to any one of claims 13 and 13.   16. The variable magnetic flux drive system according to claim 1, wherein the magnetic flux density of the variable magnet is utilized from a positive maximum to a negative maximum.