JP3178568B2 - Control device for synchronous motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a synchronous motor, and more particularly to a control device for controlling a permanent magnet type synchronous motor having a distorted induced electromotive force (induced voltage) waveform without torque pulsation and with high efficiency. Related to the device.

[0002]

2. Description of the Related Art In general, when a synchronous motor is controlled at a variable speed via a power converter, it is desirable to employ an oblique slot method with an induced voltage waveform of a sine wave in order to reduce torque pulsation. .

[0003]

However, in order to make the induced voltage waveform strictly a sine wave, the design of the electric motor is restricted, which not only makes the production difficult, but also increases the cost and increases the cost of the electric motor. There is a problem that the output of the device is reduced. In addition, there is a similar problem in employing the oblique slot method. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to enable a synchronous motor having a distorted induced voltage and not employing an oblique slot system, particularly a permanent magnet synchronous motor, to be controlled at a high power factor and high efficiency without torque pulsation. .

[0004]

SUMMARY OF THE INVENTION In order to solve such a problem, the present invention provides a control apparatus for a synchronous motor supplied with electric power via a power converter, in which a target value of an armature current of each phase is set to all of the target values. An amount that is inversely proportional to the square of the instantaneous value of the induced voltage of the phase, an amount that is proportional to the instantaneous value of the induced voltage of each phase, and an amount that is proportional to the value obtained by subtracting a predetermined value corresponding to the magnetic pole position from the torque target value. Computing means for computing as a function consisting of:
A current control means for controlling the armature current of each phase based on the calculation result is provided. In the present invention, at least one of the windings of the synchronous motor is provided.
When performing open-phase operation in which power is not supplied to more than one phase,
Assuming that the instantaneous value of the induced voltage of the missing phase is zero, the target value of the armature current of each phase can be calculated.

[0005]

According to the present invention, the torque (first torque) generated by the magnetomotive force of the windings of each phase according to the waveform of the induced voltage of the synchronous motor and the imbalance of the magnetic resistance in the gap due to the existence of the stator slot are generated. The instantaneous value of the armature current is controlled under the condition that the sum of the generated cogging torque (second torque) becomes a constant value and the power factor with respect to the induced voltage becomes maximum. Specifically, the instantaneous value of the induced voltage of the multiphase (n-phase) armature windings, respectively _{e 1, e 2, ...,} e m, when the e _n, any n-th of the armature current instantaneous value i _m is, Is controlled so that Note that in (1), K is the coefficient, T ^* represents the torque target value, T ₂ is the cogging torque, respectively.

Hereinafter, the principle of the present invention including the process of deriving the equation (1) will be described. The first torque is a torque generated by the interaction between the gap magnetic flux and the armature current, and generates an effective torque for applying a rotating force to the electric motor. The second torque is generated by an attractive force generated between the stator teeth and the magnetic poles, and generates only a torque pulsation without depending on the armature current. However, when the induced voltage has a distorted waveform, when the armature current is set to a sine wave, torque pulsation also occurs in the first torque.

Therefore, the applicant has proposed a method for solving such a problem (Japanese Patent Application No. 4-246823).
No .: Also called the proposed method). This is to make the torque pulsation due to the first torque zero and to control the synchronous motor with high power factor and high efficiency. However, since the proposed method ignores the second torque, there is a new problem that torque pulsation due to the second torque occurs. This second torque can be zeroed or reduced by skewing the slots, i.e., using an oblique slot system. However, this has the above-mentioned problem, and in order to reduce the cost, it is desirable not to adopt the oblique slot method. To do so:

According to the proposed method, since the induced voltage e _m of the armature winding is proportional to the rotational speed _{ω, e m = ωe 0m ...} (2) in e _{0 m} (hereinafter, referred to as reference induction voltage) represented the When defined, the armature current that makes the torque pulsation due to the first torque zero and has a high power factor and high efficiency is: (T ₁ ^* is the first torque target value).

The second torque produces a torque pulsation determined by the structure of the synchronous motor, which is not directly controllable. However, the shaft torque of the electric motor is represented by the sum of the first torque and the second torque. If the sum is constant, the torque pulsation becomes zero and smooth rotation is guaranteed. Focusing on this point, in the present invention, the pulsation due to the uncontrollable second torque is compensated by the controllable first torque so that the torque pulsation of the shaft torque becomes zero. That is, T ₁ + T ₂ = T (constant) (4) (T ₁ : first torque, T ₂ : second torque, T: shaft torque), so that T ₁ ^* = T ^* −T ₂ .. (5) controls the _first torque T ₁ .

[0010] Substituting into the above equation (5) (3), an armature current i _m which the shaft torque becomes a desired torque T ^* (constant)
Is Which is consistent with equation (1).

[0011]

FIG. 1 is a block diagram showing a first embodiment of the present invention.
FIG. 2 is a configuration diagram of a power converter main circuit to which the present invention is applied. As shown in FIG. 2, the power converter 1
１1n, consisting of n single-phase inverters,
Is a permanent magnet type n-phase synchronous motor having n sets of independent windings 21 to 2n. 2 ′ is a magnetic pole position sensor for detecting the position of the magnetic pole.

If the armature reaction of the synchronous motor is small and negligible (the induced voltage does not change due to the armature current), the induced voltage is a function of the position of the magnetic pole and the rotational angular velocity. Therefore, this relationship is stored in the memory 3 of FIG.
1 to 3n, and by reading out the contents of this memory in accordance with the position θ of the magnetic pole, the instantaneous values e _{01 to} e _0n of the reference induced voltage corresponding to each phase can be obtained. On the other hand, since the second torque T ₂ gives a torque pulsation determined by the structure of the synchronous motor, if this is also stored in the memory 4 of FIG. 1 as a function related only to the magnetic pole position, the magnetic pole position θ
This by reading the contents of the memory 4, it is possible to obtain a second value of the torque T ₂ in accordance with the.

An arithmetic unit 5 calculates a current command value or a target value. The torque target value T ^* and the instantaneous values e ₀₁ to e of the reference induced voltage read from the memories 31 to 3n and 4.
e _0n, the second torque T _2, obtains the previous equation (6) to the basis of each phase current target value i ₁ ^* ~i _n ^*. 61-6n
Is a current regulator (ACR), and current target values i ₁ ^{* to} i
_n ^* and amplifies the deviation between the detected current value i ₁ through i _n. 71
7 to 7n are pulse generators (PG) that perform pulse width modulation (PWM) on the outputs of the ACRs 61 to 6n and generate gate pulses for the single-phase inverters 11 to 1n. If the waveform of the induced voltage is symmetrical in each phase, the memory capacity can be reduced by devising the read address of the memory that stores the reference induced voltage.

FIG. 3 is a block diagram showing another embodiment of the present invention. Each of the memory 31~3n in the _{figure, n n n e 01 / Σe} 0m 2, e 02 / Σe 0m 2, a ^{_{... e 0n / Σe 0m m =}} 1 m = 1 m = 1 becomes the waveform, also, the memory 4 stores the waveform of the second torque T ₂ , reads out the content according to the magnetic pole position θ, and subtracts T ₂ from the torque target value T ^* to obtain T ^* −T _2. Is multiplied by the outputs from the memories 31 to 3n,
The current target values i ₁ ^{* to} i _n ^* of each phase are obtained.

FIG. 4 is a block diagram showing still another embodiment of the present invention. This shows an example of open-phase operation in which only one or more phases are not supplied when an abnormality occurs in some phases of the inverter. That is, in the case of the open phase operation, the reference induction voltage of the open phase is set to zero (in FIG. 4, the switches S _{1 to} S corresponding to the open phase are set).
the _n open), so as to obtain the phase of the current target value i ₁ ^* through i _n ^* according to the previous equation (6). in this way,
By controlling each phase current, the pulsation of the shaft torque becomes zero, which is obvious from the principle described in the proposed method and the fact that the second torque is the same as in the non-open phase even in the case of the open phase. is there.

[0016]

According to the present invention, the target value of each phase of the armature current is set to an amount inversely proportional to the square of the instantaneous value of the induced voltage of all phases, and the induction value of each phase is set, as in the proposed method. Not only the amount proportional to the instantaneous value of the voltage, but also the amount proportional to the value obtained by subtracting the predetermined value corresponding to the magnetic pole position from the torque target value is obtained, so that torque pulsation is more effectively eliminated. Therefore, there is provided an advantage that the control can be performed with high power factor and high efficiency.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram of a main circuit of a power converter to which the present invention is applied.

FIG. 3 is a block diagram showing another embodiment of the present invention.

FIG. 4 is a block diagram showing still another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Power converter, 11-1n ... Single phase inverter, 2 ... Synchronous motor, 21-2n ... Synchronous motor winding, 2 '... Magnetic pole position sensor, 31-3n, 4 ... Memory, 5 ... Current command calculator, 61, 6n ... current regulator (ACR), 71-7n ...
Pulse generators (PG), 81 to 8n... Multipliers.

Continuation of the front page (56) References JP-A-6-98596 (JP, A) JP-A-64-1492 (JP, A) JP-A-62-163591 (JP, A) JP-A-3-178590 (JP) , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 5/408-5/412 H02P 7/628-7/632 H02P 21/00 H02P 6/00-6/24

Claims (2)

(57) [Claims] 1. A control device for a synchronous motor supplied with electric power via a power converter, wherein a target value of an armature current of each phase is inversely proportional to a square value of an instantaneous value of an induced voltage of all phases; Calculating means for calculating as a function consisting of an amount proportional to the instantaneous value of the induced voltage of each phase and an amount proportional to a value obtained by subtracting a predetermined value corresponding to the magnetic pole position from the torque target value; A control device for a synchronous motor, comprising: current control means for controlling a phase armature current. 2. When an open-phase operation is performed such that at least one or more phases of the windings of the synchronous motor are not supplied with power, the instantaneous value of the induced voltage of the open phase is regarded as zero.
The control device for a synchronous motor according to claim 1, wherein a target value of the armature current of each phase is calculated.