JP7724599B2 - Polyphase Motor Drive - Google Patents

Description

An embodiment of the present invention relates to a polyphase motor drive device.

A polyphase motor drive uses multiple power conversion units (inverters) to drive a polyphase motor, which has multiple windings that are electrically isolated from one another.
Some polyphase motor drive devices have multiple power conversion units connected in parallel to a single DC link. Each of the multiple power conversion units receives DC power from the DC link, converts the DC power to generate AC power, and supplies the AC power to each of the multiple windings of the polyphase motor, thereby driving the polyphase motor. In such polyphase motor drive devices, there has been a demand for a higher DC voltage in the DC link.

Japanese Patent Application Publication No. 11-127593

The problem that this invention aims to solve is to provide a multi-phase motor drive device that can further increase the DC voltage of a DC link to which multiple power conversion units that supply AC power to a multi-phase motor are connected.

A polyphase motor drive device according to an embodiment includes a first row of M single-phase inverters and a second row of M single-phase inverters. The M single-phase inverters in the first row are M single-phase inverters connected in series at their DC power supply sides to form a first row, and supply single-phase AC power converted from DC power supplied to a DC link from a DC power supply to each of a first group of windings of a polyphase motor having 2M single-phase windings. The M single-phase inverters in the second row are M single-phase inverters connected in series at their DC power supply sides to form a second row, and supply single-phase AC power converted from DC power supplied to the DC link to each of a second group of windings of the polyphase motor . power supply sides of the M single-phase inverters forming the first column are connected in series with each other, and the M single-phase inverters forming the first column connected in series are connected between both poles of the DC link; power supply sides of the M single-phase inverters forming the second column are connected in series with each other, and the M inverters forming the second column connected in series are connected between both poles of the DC link; the M single-phase inverters of the first column form a first set of inverter groups; the M single-phase inverters of the second column form a second set of inverter groups; a first connection point connecting two single-phase inverters of the M single-phase inverters of the first column to each other and a second connection point connecting two single-phase inverters of the M single-phase inverters of the second column to each other are connected to each other at equipotential connection points; and AC currents with a phase difference of 90 degrees are output from the two single-phase inverters connected in parallel with each other by connecting the equipotential connection points to each other; M is a natural number equal to or greater than 2, and the number of columns of the M single-phase inverters in the first column and the second column is two.

1 is a configuration diagram of a multi-phase motor drive device according to an embodiment; FIG. 2 is a configuration diagram of a single-phase inverter according to an embodiment. FIG. 2 is a configuration diagram of a single-phase inverter according to an embodiment. 3A and 3B are diagrams for explaining the relationship between a polyphase motor and each single-phase inverter according to the embodiment;

The following describes a polyphase motor drive device according to an embodiment, with reference to the drawings. In the following description, components having the same or similar functions are assigned the same reference numerals. Duplicate descriptions of these components may be omitted. Electrically connected may simply be referred to as "connected." In the following description, "orthogonal" includes cases where the components are approximately orthogonal. In addition, "equal in size" also includes cases where the components are approximately equal.

FIG. 1 is a configuration diagram of a polyphase motor drive device according to an embodiment.
FIG. 1 shows a polyphase motor 1, a polyphase motor drive device 2, and a speed control device 4.

The multi-phase motor drive device 2 includes single-phase inverters 21, 22, ..., 2M and single-phase inverters 31, 32, ..., 3M. The single-phase inverters 21, 22, ..., 2M are collectively referred to as single-phase inverter group 20 (first set of inverter group). The single-phase inverters 31, 32, ..., 3M are collectively referred to as single-phase inverter group 30 (second set of inverter group). M is, for example, a natural number greater than or equal to 2. The multi-phase motor drive device 2 drives the multi-phase motor 1 by operating the single-phase inverter group 20 and the single-phase inverter group 30, respectively. The single-phase inverter 21 and other inverters will be described later.

The multi-phase motor drive device 2 includes DC links LP and LN connected to the DC side of a rectifier (not shown), for example. For example, the DC link LP is positive and the DC link LN is negative. The DC links LP and LN are connected to a DC power supply device, rectifier, battery, power capacitor, etc. (not shown).

The power supply sides of the single-phase inverters 21, 22, ..., 2M included in the single-phase inverter group 20 are connected to each other in series. The serially connected single-phase inverters 21, 22, ..., 2M are connected between the poles of the DC links LP and LN, and receive DC power from the DC links LP and LN.

Similarly, the power supply sides of the single-phase inverters 31, 32, ..., 3M included in the single-phase inverter group 30 are connected in series with each other. The serially connected single-phase inverters 31, 32, ..., 3M are connected between the poles of the DC links LP and LN, and receive DC power from the DC links LP and LN.

The multi-phase motor 1 has multiple windings (see Figure 4) corresponding to each phase, and the windings are electrically insulated from one another. Each winding is connected to the output of single-phase inverters 21, 22, ..., 2M and the output of single-phase inverters 31, 32, ..., 3M, respectively. The multi-phase motor 1 is driven by AC power supplied to each winding from single-phase inverters 21, 22, ..., 2M and single-phase inverters 31, 32, ..., 3M. The following description will be given using a multi-phase motor 1 with a permanent magnet field as an example. However, an electromagnet field may also be used, in which case the magnetic pole direction of the excitation should be changed to that of a permanent magnet. A rotation angle detector (not shown) is attached to the shaft of the multi-phase motor 1. The output of the rotation angle detector is connected to the input of the speed control device 4. The rotation angle detector detects the mechanical angle of the shaft of the multi-phase motor 1 and supplies the detected mechanical angle to the speed control device 4.

The speed control device 4 is provided in common to each of the single-phase inverters 21, 22, ..., 2M and the single-phase inverters 31, 32, ..., 3M, and receives a speed command transmitted from a higher-level control device (not shown). This speed command may vary over time. The speed control device 4 transmits a fundamental wave current command ICOM to each of the single-phase inverters 21, 22, ..., 2M and the single-phase inverters 31, 32, ..., 3M. Each of the single-phase inverters 21, 22, ..., 2M and the single-phase inverters 31, 32, ..., 3M passes an AC current corresponding to the fundamental wave current command ICOM through the windings of the multi-phase motor 1.

2 and 3 are configuration diagrams of a single-phase converter cell according to an embodiment.
2 and 3 show a single-phase inverter 21 including at least one semiconductor element. The single-phase inverter 21 may be, for example, a single-phase full-bridge type that combines multiple semiconductor elements as shown in FIG. 3. The semiconductor element shown in FIG. 3 is an insulated gate bipolar transistor (IGBT). The semiconductor element is not limited to an IGBT, and other types of semiconductor elements such as field effect transistors (FETs) may also be used. The single-phase inverter 21 shown in FIG. 2 is not limited to the single-phase inverter 21 shown in FIG. 3, but a chopper-type single-phase inverter other than that shown in FIG. 3 may also be used.

The relationship between the polyphase motor 1 and each single-phase inverter will be described with reference to FIG.
FIG. 4 is a diagram illustrating the relationship between the multi-phase motor 1 and each single-phase inverter according to the embodiment. A single-phase inverter is arranged corresponding to each phase winding. In this embodiment, a single-phase inverter group 20, in which M single-phase inverters are connected in series, and a single-phase inverter group 30 are connected in parallel. Therefore, the total number of single-phase inverters is 2M. The total number W of windings shown in FIG. 4 is 2M, which is equal to the total number of single-phase inverters. Note that although the windings of each phase of the multi-phase motor 1 are not electrically connected, they may be magnetically coupled because the magnetic paths of the windings of different phases overlap.

The multi-phase motor 1 is driven by single-phase inverters provided corresponding to the windings of each phase.

The multi-phase motor drive device 2 may have, for example, the following configuration:

In the first configuration, single-phase inverters 21, 22, ..., 2M and single-phase inverters 31, 32, ..., 3M each have the same specifications. In this case, if the rated DC voltage of each single-phase inverter is represented by VIN, the rated DC voltage of single-phase inverter group 20, which consists of M single-phase inverters connected in series, is (Vin x M). In other words, it is M times the rated DC voltage of a single single-phase inverter. In other words, the DC link voltage VDC can be increased to (Vin x M). If the DC link voltage VDC is specified first, the rated DC voltage VIN of each single-phase inverter is (VDC/M). By adopting the first configuration, which aligns the specifications of each single-phase inverter, the following second configuration becomes possible.

In a second configuration, the connection points on the DC power supply sides of single-phase inverters 21, 22, ..., 2M and the connection points on the DC power supply sides of single-phase inverters 31, 32, ..., 3M are connected at equipotential points. For example, the DC power supply sides of single-phase inverter 21 and single-phase inverter 22 are connected in series, so that the negative side of the DC power supply of single-phase inverter 21 is connected to the positive side of the DC power supply of single-phase inverter 22. This connection point is called connection point 212. The single-phase inverters 31 and 32 are connected in series, so that the negative side of the DC power supply of single-phase inverter 31 is connected to the positive side of the DC power supply of single-phase inverter 32. This connection point is called connection point 312.

For example, if the voltage between DC links LP and LN is represented by voltage VDC and the number of inverters (number of series connections) in single-phase inverter group 20 is M, then the potential at node 212 is (VDC x (1-1/M)). Similarly, the potential at node 312 is also (VDC x (1-1/M)). From the results of the above calculation, the potential at node 212 and the potential at node 312 are equipotential, so it is advisable to connect node 212 and node 312.

Similar to the connection between connection point 212 and connection point 312 described above, it is preferable to connect the connection points between inverters in single-phase inverter group 20 and the corresponding connection points between inverters in single-phase inverter group 30 such that the connection points are at the same potential. By connecting the connection points at the same potential as described above, it is possible to reduce the impact of potential fluctuations on the DC input side when single-phase inverters 21, 22, ..., 2M and single-phase inverters 31, 32, ..., 3M are operating.

In a third configuration, a capacitor is provided on the power supply side of each of single-phase inverters 21, 22, ..., 2M and single-phase inverters 31, 32, ..., 3M. Each capacitor helps to reduce the effects of voltage fluctuations caused by the operating state of the nearest single-phase inverter.

For example, by combining the first to third configurations described above, it is possible to connect the capacitors on the single-phase inverter group 20 side and the capacitors on the single-phase inverter group 30 side that are at the same potential in parallel, thereby further contributing to suppressing fluctuations in the DC power supply.

In the above embodiment, the single-phase inverters 21, 22, ..., 2M provided in the multi-phase motor drive device 2 supply AC power converted from DC power supplied to the DC link to each winding of the multi-phase motor 1, which has multiple windings. The DC power supply sides of the single-phase inverters 21, 22, ..., 2M are connected in series with each other, and both ends are connected between the poles of the DC link, thereby further increasing the DC voltage of the DC link to which the single-phase inverters 21, 22, ..., 2M are connected.

The outputs of single-phase inverters 21, 22, ..., 2M may be connected to each winding of polyphase motor 1. This makes it possible to drive polyphase motor 1 using the AC power converted by each of single-phase inverters 21, 22, ..., 2M.

The multi-phase motor drive device 2 may be configured to further include a single-phase inverter group 30 (a second set of inverters forming a second row) in addition to the single-phase inverter group 20 (a first set of inverters forming a first row). In this case, the single-phase inverter group 20 and the single-phase inverter group 30 are preferably connected in parallel with each other. This allows the DC link voltage to be increased without excessively increasing the DC link voltage by increasing the number of single-phase inverter groups connected in parallel.

(First Modification of the Embodiment)
A first modification of the embodiment will be described below. The windings of the polyphase motor 1 of this modification are driven in order of the phases so that the phase difference in electrical angle is approximately 90 degrees.

The polyphase motor 1 generates a first torque based on the first AC power supplied by each inverter (first inverter) in the single-phase inverter group 20, and generates a second torque based on the second AC power supplied by each inverter (second inverter) in the single-phase inverter group 30. At this time, the speed control device 4 can suppress torque fluctuations by controlling the single-phase inverter group 20 and the single-phase inverter group 30 so that the first torque fluctuations caused by the first torque and the second torque fluctuations caused by the second torque cancel each other out.

For example, the phase of the first AC voltage output by each inverter in the single-phase inverter group 20 and the phase of the second AC voltage output by each inverter in the single-phase inverter group 30 are determined so that the first torque fluctuation and the second torque fluctuation cancel each other out. The speed control device 4 controls each inverter in the single-phase inverter group 20 and each inverter in the single-phase inverter group 30 so that the difference between the phase of the first AC voltage and the phase of the second AC voltage becomes the desired phase difference.

More specifically, the first electrical angle associated with the first AC voltage output by each inverter in the single-phase inverter group 20 and the second electrical angle associated with the second AC voltage output by each inverter in the single-phase inverter group 30 are preferably determined to be approximately orthogonal.

According to the first modified example described above, a first torque fluctuation occurs in the polyphase motor 1 based on the first AC power supplied by each inverter of the single-phase inverter group 20 to each winding of the polyphase motor 1. A second torque fluctuation occurs in the polyphase motor 1 based on the second AC power supplied by each inverter of the single-phase inverter group 30 to each winding of the polyphase motor 1. The speed control device 4 controls each inverter of the single-phase inverter group 20 and each inverter of the single-phase inverter group 30 so that the first torque fluctuation and the second torque fluctuation cancel each other out, thereby further increasing the DC voltage of the DC link and enabling the polyphase motor 1 to be driven more stably.

Furthermore, the phase of the first AC voltage output by each inverter in the single-phase inverter group 20 and the phase of the second AC voltage output by each inverter in the single-phase inverter group 30 are determined in accordance with the specifications of the windings of the multi-phase motor 1 so that the first torque fluctuation and the second torque fluctuation cancel each other out, thereby enabling the multi-phase motor 1 to be driven more stably.

In the above case, the first electrical angle associated with the first AC voltage output by each inverter in the single-phase inverter group 20 and the second electrical angle associated with the second AC voltage output by each inverter in the single-phase inverter group 30 are determined to be approximately orthogonal. For example, if the multi-phase motor 1 has a first group of windings and a second group of windings that are 90° out of phase with each other, each single-phase inverter in the single-phase inverter group 20 is connected to the first group of windings, and each single-phase inverter in the single-phase inverter group 30 is connected to the second group of windings. The speed control device 4 then controls each single-phase inverter so that the AC signals output by the single-phase inverter group 20 and the single-phase inverter group 30 are out of phase with each other by 90°, thereby allowing the power pulsation generated by the single-phase inverter group 20 and the single-phase inverter group 30 to cancel each other out.

(Second Modification of the Embodiment)
A second modification of the embodiment will be described. The first modification describes a case where the number of parallel inverter groups is set to two. When the number of parallel inverter groups is generalized to PN, the phase difference φ of the electrical angle may be calculated using the following equation (1).

φ=180°/PN...(1)

According to the second variant described above, even if the number of parallel inverter groups is increased, the power pulsations generated by each inverter group can be canceled out.

According to at least the above embodiment, the multi-phase motor drive device 2 includes single-phase inverters 21, 22, ..., 2M included in the single-phase inverter group 20. The single-phase inverters 21, 22, ..., 2M supply AC power converted from DC power supplied to a DC link to each winding of the multi-phase motor 1, which has multiple windings. The DC power supply sides of the single-phase inverters 21, 22, ..., 2M are connected to each other in series, and the serially connected single-phase inverters 21, 22, ..., 2M are connected across both poles of the DC link, thereby further increasing the DC voltage of the DC link to which the single-phase inverters 21, 22, ..., 2M that supply AC power to the multi-phase motor 1 are connected.

The speed control device 4 may be realized, at least in part, by a software function unit that functions when a processor such as a CPU executes a program, or may be realized entirely by a hardware function unit such as an LSI.

While several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments may be embodied in a variety of other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their variations are within the scope of the invention and its equivalents as defined in the claims, as well as the scope and spirit of the invention.

For example, in the above embodiment, an example was described in which the polyphase motor drive device 2 and the speed control device 4 were configured separately, but there is no restriction on integrating the polyphase motor drive device 2 and the speed control device 4, and the polyphase motor drive device 2 and the speed control device 4 may also be integrated.

In addition, the number of single-phase inverter groups connected in parallel within the polyphase motor drive device 2 and the number of single-phase inverters connected in series within the single-phase inverter group can be determined arbitrarily to match the number of phases of the polyphase motor 1 described above.

1... Multi-phase motor, 2... Multi-phase motor drive device, 4... Speed control device (control unit), 20, 30... Single-phase inverter group (inverter group), 21, 22, ..., 2M, 31, 32, ..., 3M... Single-phase inverter (inverter), LP, LN... DC link

Claims (2)

M single-phase inverters in the first column are connected in series on the DC power supply side to form a first column, and supply single-phase AC power converted from DC power supplied to a DC link from the DC power supply to each of the first group of windings of a polyphase electric motor having 2M single-phase windings;
M single-phase inverters in a second row, the DC power supply sides of which are connected in series to each other, and which supply single-phase AC power converted from DC power supplied to the DC link to each of the second group of windings of the polyphase motor;
Equipped with
power supply sides of the M number of single-phase inverters forming the first row are connected in series with each other, and the M number of single-phase inverters forming the first row connected in series are connected between both poles of the DC link;
power supply sides of the M number of single-phase inverters forming the second row are connected in series with each other, and the M number of single-phase inverters forming the second row connected in series are connected between both poles of the DC link,
the M single-phase inverters in the first column form a first set of inverters;
the M single-phase inverters in the second column form a second set of inverters;
a first connection point connecting two single-phase inverters of the M single-phase inverters in the first column to each other;
a second connection point connecting two of the M single-phase inverters in the second column to each other and a connection point at which the two single-phase inverters are equipotential are connected to each other,
The two single-phase inverters are connected in parallel by connecting the equipotential connection points to each other, and outputting alternating currents with a phase difference of 90 degrees,
The polyphase motor drive device, wherein M is a natural number equal to or greater than 2, and the number of columns of the M single-phase inverters in the first column and the second column is two. a first row of M single-phase inverters, each having a DC power supply side connected in series to form a first inverter group, for supplying single-phase AC power converted from DC power supplied to a DC link from the DC power supply to each winding of the first group of a polyphase electric motor having 2M single-phase windings;
a second column of M single-phase inverters, the DC power sources of which are connected in series to form a second set of inverter groups, and which supply single-phase AC power converted from DC power supplied to the DC link to each winding of the second group of the polyphase motor;
a control unit that provides a phase difference of 90 degrees between a phase of a first AC voltage output by a first inverter of the first inverter group and a phase of a second AC voltage output by a second inverter of the second inverter group, thereby controlling a first power pulsation of the first AC power supplied by the first inverter of the first inverter group and a second power pulsation of the second AC power supplied by the second inverter of the second inverter group to cancel each other out,
power supply sides of the M number of single-phase inverters forming the first row are connected in series with each other, and the M number of single-phase inverters forming the first row connected in series are connected between both poles of the DC link;
power supply sides of the M number of single-phase inverters forming the second row are connected in series with each other, and the M number of single-phase inverters forming the second row connected in series are connected between both poles of the DC link,
The polyphase motor drive device, wherein M is a natural number equal to or greater than 2, and the number of columns of the M single-phase inverters in the first column and the second column is two.