JP2000333498A - Controller for synchronous motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain large braking torque by keeping regenerative power at zero or a minimum. SOLUTION: Braking torque is generated with equipment, whose regenerative energy absorbing capacity is small at braking of a motor 2, such as an electric propulsion apparatus for marine. In this case, a section indicated by an a dashed line is added to a vector controller, a switch 10i is closed by a mode discriminating device 10h, and an armature magnetizing current component iM and a field current component 'if' are increased via a ramp function 10j, an amplifier 10k and so on to increase loss of the motor.

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 controlling a synchronous motor at a variable speed by using a semiconductor power converter, and more particularly to a control for increasing a braking torque of a synchronous motor for propulsion for electric propulsion of a ship. Related to the device.

[0002]

2. Description of the Related Art Vector control is known as a high-performance variable speed control of a synchronous motor, and its principle is described, for example, in "Fuji Times" Vol. 53, No. 9, p. 640 to 648 (19
80) It is introduced in many documents such as "Transformer vector control of AC machine". According to this control, the torque of the synchronous motor can be controlled with high response and high accuracy. Further, since the power factor of the synchronous motor can be controlled to 1, the synchronous motor and the power converter can be made highly efficient and compact.

FIG. 5 shows a vector diagram of a synchronous motor. In particular, when paying attention to the vector amount, a dot "." Is added to the code, and the same applies hereinafter. Armature in FIG, [psi (·) is the armature flux linkage, this is the flux linkage ψ _f (·) generated by the field current i _f (·), caused by the armature current i (·) Reaction flux linkage ψ _a
(.) v (•) is the armature voltage, and if the armature resistance is ignored, the armature interlinkage flux ψ (•)
Orthogonal to. In the vector control of the synchronous motor, the armature current i (•) is converted to a component i parallel to the armature linkage flux ψ (•).
Decomposes into _M (•) and a component i _T (•) that is also orthogonal,
The feature is that each component is controlled independently. Since i _M (•) is a current component that directly affects the armature interlinkage magnetic flux, it is called an armature magnetizing current, and the torque is represented by the magnitude of ψ (•) and i _T
Since it is proportional to the product of the magnitude of (•), i _T (•) is called the torque current. If the armature magnetizing current i _M (•) is controlled to zero, the vector directions of the armature voltage v (•) and the armature current i (•) match as shown in the vector diagram of FIG. The power factor of the motor can be reduced to one. Note that d
The angle of intersection δ between the axis and the vector ψ (•) is called the load angle.

FIG. 7 is a block diagram showing a conventional example of a vector control device for a synchronous motor.
This is an example using 1. Cycloconverters are generally
This is a power converter that directly obtains a variable voltage and variable frequency AC power supply from the AC power supply. Here, power is supplied to the synchronous motor 2 (SM), and power is regenerated from the synchronous motor to the power supply system during deceleration. 3 is a rectifier for the field of the synchronous motor, and 4 is a position detector for detecting the magnetic pole position of the synchronous motor. Although the input of the cycloconverter and the input of the rectifier for the field are connected to the same power supply, the field voltage is generally lower than the armature voltage.

[0005] In Fig. 7, reference numeral 10 denotes a control device surrounded by a broken line, and only the portions related to the present invention will be described below. The speed adjuster 10a amplifies the deviation between the speed command ω ^* and the speed (detected value) ω, and performs speed feedback control. The output of the speed controller 10a becomes a torque command T ^* , which is divided by an armature interlinkage flux command ψ ^* to obtain a torque current command i _T ^* . On the other hand, the magnetizing current command i _M ^* is set to zero in order to control the power factor of the synchronous motor to 1. Flux calculator 10b is the command i _T and i _M i _T ^*, i _M ^* and i
_The armature interlinkage magnetic flux magnitude 子 and the load angle δ are calculated from _f ^* . As shown in FIG. 8, the coordinate converter 10c rotates the coordinate axes by the sum of the magnetic pole positions θ and δ to convert the currents i _T ^* and i _M ^* into current commands i α and i β in the armature coordinate system. .
Furthermore, iα ^*, iβ ^* the two-phase / three-phase by three-phase converter 10d current command i _a ^*, i _b ^*, are converted into i _c ^*, 3-phase current commands in a current regulator 10e is obtained Feedback control. As a result, the armature current is controlled so that i _T and i _M that match the instructed i _T ^* and i _M ^* flow. On the other hand, the deviation between ψ ^* and ψ is amplified by the magnetic flux adjuster 10f, and its output is divided by cos δ to calculate the field current command _if ^* . Further, by amplifying the difference between the i _f and i _f ^* by the field current controller 10 g, controls to match the field current i _f to i _f ^*.

[0006]

The cycloconverter normally supplies electric power to the synchronous motor, but when the synchronous motor is decelerated, outputs a torque in a direction opposite to the rotational direction, that is, a braking torque. . At this time, the cycloconverter converts the kinetic energy stored in the inertia of the electric motor and the machine connected thereto into electric energy to regenerate electric power to the power supply. However, when power is supplied from a power supply that is not connected to a commercial power supply, the amount of power that can be regenerated may be limited. For example, in an electric propulsion device for a ship, a power source generally includes a diesel engine and a generator. However, diesel engines have little ability to absorb energy. Forcibly regenerating power to the power supply may cause problems such as an increase in engine speed, which may lead to equipment failure, or a reduction in engine life.Therefore, it is necessary to limit regenerative power. . For this reason, in the conventional control method, the power that can be regenerated to the power supply becomes very small, and the braking torque is limited to almost zero, so that the deceleration time of the electric motor may become extremely long, which hinders the operation of the hull. Has occurred. When connecting a resistor and an opening / closing switch to a power source to output a braking torque, the braking torque can be increased by closing the opening / closing switch and consuming regenerative power by the resistor. There is also a problem that the size of the apparatus is increased accordingly. Therefore, an object of the present invention is to make it possible to obtain a large braking torque in a synchronous motor by reducing or minimizing regenerative power without increasing ancillary equipment such as a resistor.

[0007]

In order to solve such a problem, in the invention of claim 1, the current and the magnetic flux of the synchronous motor are taken as a vector, and the armature current is parallel to the armature interlinkage magnetic flux vector. The second orthogonal to the current component 1
In a synchronous motor control device that separates the current components into independent current components and independently controls the respective current components, the first motor only outputs the torque (braking torque) in the direction opposite to the rotational direction when the synchronous motor outputs And a power factor reducing means for reducing the power factor of the electric motor by increasing the field current and flowing the current component to the polarity for demagnetizing the armature interlinkage magnetic flux.

According to the second aspect of the present invention, the current and the magnetic flux of the synchronous motor are taken as a vector, and the armature current is decomposed into a first current component parallel to the armature linkage magnetic flux vector and a second current component orthogonal to the armature linkage magnetic flux vector. In the control device for a synchronous motor that independently controls each current component, the first current component is set to an armature only when the synchronous motor outputs a torque (braking torque) in a direction opposite to a rotation direction. Power factor reduction means for reducing the power factor of the motor by increasing the field current while flowing the linkage flux to the demagnetizing polarity, loss calculation means for calculating the loss of equipment including the synchronous motor, and braking of the synchronous motor Limiting means for limiting the upper limit of the shaft output of the synchronous motor in association with the loss only when outputting torque is provided.

According to the third aspect of the present invention, the current and the magnetic flux of the synchronous motor are taken as a vector, and the armature current is decomposed into a first current component parallel to the armature linkage flux vector and a second current component orthogonal to the armature linkage magnetic flux vector. A synchronous motor control device for controlling each current component independently, a loss calculating means for calculating a loss of a device including the synchronous motor, and a torque (braking torque) in a direction opposite to a rotational direction of the synchronous motor.
Only when the output is output, limiting means for limiting the upper limit of the shaft output of the synchronous motor in association with the loss, and only when the shaft output is limited, the first current component is demagnetized to the armature interlinkage magnetic flux. And a power factor reducing means for reducing the power factor of the electric motor by increasing the field current while flowing in the same polarity.

That is, in the conventional vector control, since the power factor of the synchronous motor is controlled to 1, the loss of the motor and the cycloconverter is extremely small. Incidentally, the loss of the synchronous motor is divided into armature loss and field loss. If the power factor of the synchronous motor is reduced, the armature current increases for the same braking torque, and the armature loss increases. Furthermore, if the power factor is reduced in the demagnetizing direction, the field current increases for the same braking torque, and the field loss also increases. Since the regenerative power at the time of the braking torque is power obtained by subtracting the loss of the device from the shaft output of the synchronous motor, if the loss of the device increases, the power regenerated by the power supply can be reduced accordingly. The present invention has been made in view of this point, and only when a braking torque is output, the power factor of the synchronous motor is reduced in the demagnetizing direction to increase the armature loss and the field loss. The regenerative power to be regenerated is reduced or controlled to zero.

[0011]

FIG. 1 is a block diagram showing a first embodiment of the present invention. This is configured by adding a portion surrounded by a one-point oblique line to the conventional configuration shown in FIG. Hereinafter, the differences will be described. If the polarities of the speed and the torque match, the synchronous motor outputs the driving torque, and if the polarities do not match, the synchronous motor outputs the braking torque. For this reason, the mode discriminator 10h discriminates whether the polarity of the speed ω and the polarity of the torque command T ^* match, and determines that the synchronous motor is outputting the braking torque when the polarities do not match. When it is determined that the braking torque is output, the switch 10i is closed in the opposite direction to that shown in the figure, and a predetermined negative polarity is applied to the armature magnetizing current command via the ramp function (generator) 10j to prevent a sudden change in the current. Set the value i _M0 ^* . As a result, i _M increases to a negative polarity, and the armature current increases accordingly.

On the other hand, the current command iμ ₀ ^* is added to the output of the magnetic flux adjuster 10f to increase the field current. The armature interlinkage magnetic flux is kept constant irrespective of i _M0 ^* by setting the i μ ₀ ^* to a value obtained by multiplying i _M0 ^* by a negative coefficient k by the amplifier 10k. The field current is controlled by the action of the magnetic flux adjuster 10f so that the armature interlinkage magnetic flux is constant in a steady state even when the above iμ ₀ ^* is zero.
Adding μ ₀ ^* improves the responsiveness of the magnetic flux control. Thus, the mode discriminator 10h and the switch 10
By providing a power factor reduction means including a setter for i, a ramp function 10j, an amplifier 10k, and i _M0 ^* , the armature current and the field current can be increased without changing the braking torque of the synchronous motor. The loss of the motor can be increased, and the regenerative electric power regenerated to the power supply at the time of the braking torque can be reduced.

The principle of the present invention will be described with reference to FIG. FIG. 2 is a vector diagram when the synchronous motor is outputting a braking torque. FIGS. 5 and 6 are vector diagrams when the driving torque is output. FIG.
(A) is a vector diagram in the case where the conventional control is performed, and when the braking torque is output, the power factor becomes -1.
FIG. 2B is a vector diagram in the case of the present invention, in which the armature magnetizing current i _M (·) is caused to flow in the opposite direction to the magnetic flux ψ (·) to intentionally lower the power factor. is there. FIG.
In both cases (a) and (b), the armature interlinkage flux ψ (•)
And the armature current component orthogonal to this, that is, the torque current i _T (•) is the same, so that the torque is the same. However, in FIG. 2B, both the armature current and the field current increase compared to FIG. 2A, and the loss of the synchronous motor and the power converter increases. Since the regenerative power regenerated by the power supply can be reduced by the increased loss, the braking torque can be increased.

FIG. 3 is a block diagram showing a second embodiment of the present invention, which is configured by adding a portion surrounded by a one-point oblique line to the conventional configuration. Since the added function is the one shown in FIG. 1 with a torque limiting function further added, only the added function will be described below. Here, since a large current flows at the time of the braking torque, the copper loss of the synchronous motor becomes dominant. Therefore, a loss calculator 10m is provided to calculate the copper loss P _L of the winding from the armature current and the field current of the synchronous motor based on the following equation (1). ^{_{P L = Ra (i M *}} 2 + i T * 2) + Rfi f * 2 ... (1) However, Ra is armature resistance, Rf is a field resistance. In the equation (1), the copper loss is calculated using the current command value. However, it is needless to say that the calculation can be performed using the detected current value.

[0015] Alternatively, the copper loss P _L, computes the input power of the motor using the armature voltage v _M, v _T and v _f in M-T coordinates, subtracting therefrom the shaft output, from the following equation (2) The calculation may be performed. P _L = v if ^{_{M i M * + v T i}} T * + v f i f -ωT * ... (2) This can calculate the loss of the synchronous motor including iron loss of the synchronous motor.

Alternatively, the equipment loss including the loss of the synchronous motor and the loss of the power converter can be calculated by subtracting the shaft output of the synchronous motor from the input power of the converter. The operation equation in this case is shown in the following equation (3). _{P L = v U i U +} v V i V + v W i W -ωT * ... (3) _{However, v U, v V, v} W input phase voltage of the power converter,
i _U , i _V , and i _W are input phase currents of the power converter. the above
The loss PL calculated by any of the equations (1) to (3) is divided by the speed ω to obtain a torque command limit value T _LIM . Torque limiter 10n so that torque command T ^* does not exceed T _LIM
By limiting the torque command by the above, the shaft output becomes equal to or less than the loss of the device, and regenerating power to the power supply is avoided.

FIG. 4 is a block diagram showing a third embodiment of the present invention, which is configured by adding a portion surrounded by a one-point oblique line to the conventional configuration. Only the added function will be described below. The loss calculator 10m calculates the loss PL of the device, divides the output by the speed ω, and obtains the torque command limit value T.
_LIM . The mode discriminator 10h discriminates whether the polarity of the speed ω and the polarity of the torque command T ^* match or not, and when the polarities do not match, determines that the synchronous motor is outputting the braking torque.
In this case, the switch 10i is closed, and the torque command is limited by the torque limiter 10n so that the torque command T ^* does not exceed T _LIM . The difference between the output T ^** of the speed controller 10a and the torque command T ^* after the torque limitation is amplified by the amplifier 10p. However, the amplifier 10p has a function of converting the polarity so that its output becomes negative, and the output of 10p is used as the armature magnetizing current command i _M0 ^* . Simultaneously increasing the field current is the same as in the case of FIGS. Thus,
The torque is limited so that the shaft output of the synchronous motor does not exceed the loss of the equipment. T _LIM increases, and a large braking torque can be obtained.

[0018]

According to the present invention, when the synchronous motor is outputting the driving torque, the power factor of the synchronous motor is controlled to 1 so that the synchronous motor and the power converter can be made highly efficient and compact. . On the other hand, when the synchronous motor is outputting the braking torque, the power factor decreases in the demagnetization direction, so that the armature current and the field current increase, and the loss of the equipment increases, thereby supplying power to the power supply. A large braking torque can be obtained without regeneration or with small regenerative power. It is effective for stable operation, avoidance of trouble due to abnormal increase in speed of the engine, and prolonging the life of the engine in applications in which power cannot be regenerated to the power supply, for example, in a marine electric propulsion device using a diesel engine as a power source.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a vector diagram for explaining the principle of the present invention.

FIG. 3 is a configuration diagram showing a second embodiment of the present invention.

FIG. 4 is a configuration diagram showing a third embodiment of the present invention.

FIG. 5 is a vector diagram when a power factor is ≠ 1 when a general synchronous motor is driven.

FIG. 6 is a vector diagram when a power factor = 1 when a general synchronous motor is driven.

FIG. 7 is a block diagram showing a conventional example of a control device for a synchronous motor.

FIG. 8 is a diagram illustrating the relationship between coordinate axes.

[Explanation of symbols]

1. Cyclo converter, 2. Synchronous motor (SM), 3.
... Rectifier, 4 ... Position detector, 5 ... Transformer, 10 ... Control device, 10a ... Speed regulator, 10b ... Flux calculator, 10c
... Coordinate converter, 10d ... 2-phase / 3-phase converter, 10e ... Current regulator, 10f ... Flux regulator, 10g ... Field current regulator, 10h ... Mode discriminator, 10i ... Switch, 10j
... Ramp function (generator), 10k, 10p ... Amplifier,
10m: Loss calculator, 10n: Torque limiter.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Katsuhiro Murayama 1-1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa F-term in Fuji Electric Co., Ltd. 5H576 AA20 BB06 CC06 DD02 DD05 EE01 EE02 EE09 GG02 GG04 GG10 HB04 JJ28 LL22 LL34 LL41 LL60

Claims (3)

[Claims] 1. An electric current and a magnetic flux of a synchronous motor are taken as vectors, and an armature current is decomposed into a first current component parallel to an armature interlinkage magnetic flux vector and a second current component orthogonal to the armature linkage magnetic flux vector. In a synchronous motor control device for independently controlling a current component, the armature interlinkage magnetic flux is reduced by reducing the first current component only when the synchronous motor outputs a torque (braking torque) in a direction opposite to a rotation direction. A control device for a synchronous motor, characterized in that a power factor reducing means for reducing the power factor of the motor by flowing the current to the magnetizing polarity and increasing the field current is provided. 2. The current and magnetic flux of the synchronous motor are taken as vectors, and the armature current is decomposed into a first current component parallel to the armature interlinkage flux vector and a second current component orthogonal to the armature flux vector. In a synchronous motor control device for independently controlling a current component, the armature interlinkage magnetic flux is reduced by reducing the first current component only when the synchronous motor outputs a torque (braking torque) in a direction opposite to a rotation direction. Power factor reducing means for reducing the power factor of the motor by increasing the field current while flowing to the magnetizing polarity; loss calculating means for calculating the loss of equipment including the synchronous motor; and when the synchronous motor outputs braking torque. Limiting means for limiting the upper limit of the shaft output of the synchronous motor in association with the loss. 3. The current and magnetic flux of the synchronous motor are taken as vectors, and the armature current is decomposed into a first current component parallel to the armature linkage flux vector and a second current component orthogonal to the armature linkage flux vector. In a synchronous motor control device for independently controlling a current component, a loss calculating means for calculating a loss of a device including the synchronous motor, and only when the synchronous motor outputs a torque (braking torque) in a direction opposite to a rotational direction. Limiting means for limiting the upper limit of the shaft output of the synchronous motor in association with the loss; and only when the shaft output is limited, the first current component is supplied to a polarity that demagnetizes the armature interlinkage magnetic flux. A control device for a synchronous motor, comprising: a power factor reducing means for increasing a field current to reduce a power factor of the motor.