JP2002051589A - Controller for inverter for drive of motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller for a motor which does not much affect efficiency even if ripple occurs sharply, and an inverter for drive of the motor, which controls the currents of the d and q axes of the motor so that the the input current i may become sine waves as far as possible by letting a current ed contain ripple intentionally and controlling it. SOLUTION: This controller for an inverter for drive of a motor improves the input power factor of a diode full wave rectifying circuit 2 and the waveform, by controlling the torque of a motor 5 in advance, with the frequency double the power source, by means of a single-phase diode full wave rectifying circuit 2 which receives the input of a single-phase AC power source 1, a small- capacity smoothing capacitor 3 about one hundredth the smoothing capacitor for a conventional diode full wave rectifying circuit connected to this, and 8 control circuit 6 composed of a PWM inverter circuit 4 for control and a motor 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor (or a smoothing reactor) for improving a power factor of a single-phase diode rectifier circuit of an internal magnet synchronous motor or a reluctance motor driven by a PWM inverter having a single-phase diode rectifier circuit.
And a control device for a motor drive inverter for intentionally generating a ripple at twice the frequency of a power supply in a DC link voltage by reducing a smoothing capacitor as much as possible to realize an input current waveform improvement and a high power factor. It cannot be used for those that use a three-phase power supply or for servos that require high-speed torque control, and can only be used for small-capacity general power that requires steady torque, but uses a lot of single-phase power. In the home appliance field and small industrial motor drive systems,
The present invention relates to an extremely advantageous motor drive inverter control device that achieves light weight, long life, low cost, and high efficiency.

[0002]

2. Description of the Related Art FIG. 10 shows a case where a power-factor improving reactor 11 is used as an input of a single-phase AC power supply 10 which is currently most frequently used.
This is a circuit for improving the input power factor of the capacitor input diode rectifier circuit 12. In this circuit, the reactor 11 is heavy and large in size, and it is difficult to sufficiently improve the waveform, and it is difficult to satisfy the current harmonic regulation. Even the current best one has a power factor of about 80 to 85% and a large harmonic component.

In this rectifier circuit, a PWM inverter is used.
Although an induction motor driven by 14 or a permanent magnet motor 15 is often used, a large smoothing capacitor 13 is often used to suppress ripple of the DC link voltage in order to improve the characteristics of the motor. At this time, a large current flows through the diode only in a short section near the peak of the input voltage. For this reason, if the reactor 11 is small, the current waveform becomes sharp and contains many harmonics, which causes a large power failure.

[0004] If a capacitor 16 of the voltage doubler rectifier circuit is inserted, the waveform and the power factor can be improved. However, since an electrolytic capacitor having a large current capacity is required, it is expensive and its life is short.

[0005] Single-phase power supplies are often 100V and 200V systems, and from the economical viewpoint of inverter elements, the DC link voltage is high.
e _d is being used a lot about 250~350V. For this reason, it is difficult to employ a voltage doubler rectifier circuit (DC link voltage of 500 V or more) in a 200 V system, and a full-wave rectifier circuit is often used.

When a large reactor is inserted in series with the power supply of the voltage doubler rectifier circuit, the waveform is somewhat improved, but at most 90%, and the voltage drop at this impedance increases the voltage fluctuation rate, thus making it difficult to control the PWM inverter. It creates obstacles and reduces efficiency.

When the power of the reactor 11 is small,
Since a large rush current flows to charge the electrolytic capacitor 13, some kind of capacitor charging circuit 17 is required.

As shown in FIG. 11, an active filter 22 is inserted between a diode rectifier circuit 21 and an electrolytic capacitor 23 having a single-phase power supply 20 for satisfying the harmonic regulation value.
In some cases, the input current i in phase with the input voltage v is converted into a sine wave by instantaneously controlling the input current. This circuit is ideal because a high power factor of almost 100% (99% or more) can be obtained. However, since this circuit includes an extra switching element, it is inferior in efficiency, price, size, and noise with respect to the power supply. It is.

Further, a large-capacity electrolytic capacitor 23 must be used, and there are still problems in life, price, size, capacitor charging circuit, and the like. The motor 25 is designed so that the DC link power supply of the inverter 24 has little ripple. Since this circuit is also designed with a small inductance of the active filter, a large inrush current flows when the switch is turned on, so that the charging circuit 26 of the electrolytic capacitor 23 is required.

As described above, the conventional circuit has problems in price, life, efficiency, weight, and size.

However, these are items that must be given the highest priority in terms of the system configuration.

[0012]

The absolute value of the invention It is an object of the input voltage at the diode full-wave rectifier circuit shown in FIG. 1 | v | is greater than the DC link voltage _{e d (| v |> e} d) become not a current flows Absent.

[0013] FIG. 2 (a) The input current i and | v |, which is an example of a waveform showing the relation between e _d. The input current i if the ripple is small output e _d in the smoothing capacitor is large rectifier circuit as in Fig has many waveforms poor harmonic component because the sharp waveform.

[0014] FIG. 2 (b) set small smoothing capacitor, in which so as to generate a large ripple e _d. In this case, | v | ≒ e in the area is increased portion thereof _d diode it can be seen that the current conducting width so also conduct is improved as well FIG widens current waveform than the case of FIG. (A). However, when the motor is driven by such an inverter input, ripple is unlikely to occur as shown in FIG. 2A depending on the motor, and the waveform is not improved, or the harmonics cause a significant decrease in motor efficiency. .

An object of the present invention is to improve the waveform of an input current by controlling a motor capable of generating a large ripple and having no significant effect on the efficiency reduction.

[0016] occurs is difficult to cause the motor of ripple in e _d is because for example the surface magnet type motor motor of the field (gap magnetic field) can not be much change in this category.

The cause of the decrease in efficiency is that the rotor has a short-circuit winding (a damper winding of an induction machine or a synchronous machine), and these motors cannot be used.

In the case of the surface magnet type motor, one of the motors which are currently used in brushless motors and the like, and which has little influence on the efficiency even if the DC link voltage includes ripples. However, the field weakening used here requires an excessive d-axis field weakening current. That is, since the induced electromotive force cannot be changed significantly, the current waveform becomes sharp as in the case where a large electrolytic capacitor is connected to the DC link, and the contribution to the power factor improvement is small.

In the case of an induction motor, which is an AC motor that is currently most frequently used, when it is operated with a DC power supply that changes twice as much as the power supply, the inverter output has an amplitude with the DC link voltage _ed as an envelope. Since a modulated voltage is generated, the output contains many harmonics of the frequency of (output average frequency ± 2 × power supply frequency), resulting in a fatal decrease in efficiency of the motor.

This is because this harmonic component causes an excessive harmonic current to flow through the rotor, and the copper loss increases. A reduction in efficiency of 10-20% will be seen.

In the case of a synchronous motor with a damper winding, also in this case, as in the case of the induction motor, a short-circuit winding is provided on the field side. In addition, since it is not designed with a thermal margin like an induction motor, a large short-circuit current flows through the damper winding, which may lead to burnout. However, the power factor is improved as compared with the conventional method.

Even if the ripple is superimposed on the DC link voltage and the output voltage of the inverter becomes a three-phase AC voltage having the DC voltage as an envelope, there is a need for a motor that is less affected by the waveform and a control method therefor.

[0023] Therefore, an object of the present invention, only the sinusoidal wave such ripples can input current i is controlled to include less motor and ripple affecting the even lower efficiency occurs substantially deliberately e _d The present invention relates to a control device for a motor driving inverter for controlling d and q axis currents of a motor.

That is, according to the present invention, in a conventional diode full-wave rectifier circuit having a single-phase power supply, an input reactor is removed and a small-capacity smoothing capacitor (about 1/100 of a conventional one) is used. An object of the present invention is to make it possible to generate a ripple in a DC link voltage and to improve a waveform and a power factor of an input current by d and q axis currents of a motor.
Another object of the present invention is to realize a control method for improving the structure, waveform and power factor of the motor with little reduction in efficiency due to the ripple.

As a result, a long-life capacitor such as a reactorless film or a film can be used, so that small size, light weight, long life, low cost and high efficiency can be achieved. Also, since the capacitor is small when the switch is turned on, a simple circuit configuration that does not require a special charging circuit is provided.

[0026]

The gist of the present invention will be described with reference to the accompanying drawings.

A single-phase diode full-wave rectifier circuit 2 having a single-phase AC power supply 1 as an input, and a small-capacity smoothing capacitor 3 connected to the single-phase diode full-wave rectifier circuit, which is about 1/100 of a conventional smoothing capacitor for a diode full-wave rectifier circuit. , Control PWM inverter 4
By controlling the torque of the motor 5 at twice the frequency of the power supply in advance by the control circuit 6 composed of the motor 5 and the motor 5, the input power factor and the waveform of the diode full-wave rectifier circuit 2 can be improved. The present invention relates to a control device for a motor driving inverter.

Further, a single-phase diode full-wave rectifier circuit 2 having a single-phase AC power supply 1 as an input, and 1/100 of a conventional smoothing capacitor for a diode full-wave rectifier circuit connected thereto.
A control circuit 6 including a small-capacity smoothing capacitor 3, a control PWM inverter 4 and a motor 5,
A motor driving inverter characterized in that by preliminarily controlling the field of the motor 5 at twice the frequency of the power supply, the current conduction width of the diode full-wave rectifier circuit 2 is widened and the input power factor and the waveform are improved. The present invention relates to the control device.

Further, in claim 1 or claim 2,
A motor drive wherein an internal magnet synchronous motor or a reluctance motor is used as the motor 5, and the loss does not increase significantly even if the terminal voltage of the motor 5 is pulsated at twice the frequency of the power supply. The present invention relates to an inverter control device for a vehicle.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention (how to implement the invention) which is considered to be preferable will be briefly described with reference to the drawings, showing its operational effects.

[0031] There is a DC link voltage less motor affect the at most ripple efficiency e _d, it is possible to enhance the control of the ripple without significant efficiency reduction by combination of high-speed control. The following motors can realize this.

[0032] - internal magnet type synchronous motor d-axis, the induced electromotive force of the motor by field weakening since the q-axis inductance ratio L _q / L _d can be designed larger can be greatly reduced. At present, the field can be weakened 3 to 5 times.

When this is used, the induced electromotive force can be controlled three to five times by d-axis current (I _d ) control. This is 33% of the maximum value e _d (1/3), it can significantly increase the meaning and ripple voltage that even if 20% (1/5) can flow the input current.

However, since the field weakening must be performed at twice the frequency of the power supply and at a high speed, d
The value of the axis inductance L _d must be small. Fortunately, this motor has a permanent magnet on the d-axis and uses materials such as fillite and neodymium boron.The permeability of these motors is almost the same as that of vacuum, so that the gap It can be seen as a large motor and L _d is small. In an actual motor, the impedance drop 2ωL _d I _{d at} an angular frequency 2ω twice as large as that of the power supply is 20% or less of the rated voltage even when I _d is the rated current, and can be sufficiently controlled.

Since a pulsating current modulated at twice the frequency of the power supply also flows through the winding, the copper loss increases, but there is no practical problem with the copper loss of a single-phase induction motor. The iron loss will not be much different from the iron loss of the single-phase induction motor. From these points,
There are few problems due to reduced efficiency.

Reluctance motor In this motor, the field can be adjusted from zero because the field is generated by the d-axis current, so that voltage control is possible from zero. Also,
Can inductance ratio L _q / L _d to obtain a large above motor the same characteristics. However, rotors that have been used in the past have been made of massive iron cores.If the field changes at high speed, eddy currents flow through the iron core, increasing losses and deteriorating the transient characteristics of field adjustment. Made of iron core and limited to those with little iron loss.

In order to generate a ripple voltage using such a motor, it is sufficient that the terminal voltage of the motor can be modulated to twice the frequency of the power supply by using a high-speed field control technique using the d-axis current of the motor. Whether such a high-speed excitation is possible with a general device or a method thereof has been a problem. Fortunately, as described above, this motor has a small d-axis inductance, and since it is intended for a high-speed motor, it can be sufficiently controlled at a frequency of about twice the power supply.

When these motors are used, the magnitude of the field of the motor can be controlled at high speed with a small d-axis current or voltage. If control can be performed at twice the frequency of the power supply, the induced electromotive force of the motor can be modulated to twice the power supply frequency. At this time, the envelope of the three-phase terminal voltage of the motor changes at twice the frequency of the power supply. Further, since the double ripple is also superimposed on the DC link voltage, the conduction range of the diode is widened and high power factor control is possible.

FIG. 3 is a waveform showing the principle of this circuit. Since the three-phase AC voltage is an inverter output (e.g., v _ab) is a waveform as amplitude-modulated by the DC link voltage e _d as shown, the DC link voltage e _d of the rectifier circuit as in FIG. Since the envelope becomes an envelope, the conduction width of the input current is increased with a large amount of ripples, and the input current waveform can be approximated to a sine wave.

[0040] To achieve the first aspect, modulates the q-axis current i _q corresponding to the torque current of the motor at twice the frequency of the power source, to generate twice the pulsating torque of deliberately power frequency. Since this current is almost proportional to the DC link current _idc , follow this current or use one modulated with a waveform of | v |.

In order to achieve the second aspect, the rectifier circuit excludes the input reactor so that as much ripple as possible is generated.
Use as small a smoothing capacitor as possible. This capacitor is of such a size as to bypass harmonics caused by the switching of the inverter, and may be about 1/100 of the conventional capacitor.

Since the induced electromotive force of the motor is proportional to the gap magnetic flux of the motor and the rotation speed, if the rotation speed is fixed, the motor follows the gap magnetic flux as close as possible to | v | You need to be able to do it.
For this, the magnetic flux control must be controlled by following the waveform of | v |.

In order to achieve the third aspect, a motor is required in which even if a large amount of ripple is generated in the DC link voltage, the loss does not increase much. This includes an internal magnet synchronous motor and a reluctance motor, as described above. The q-axis current and d-axis magnetic flux of these motors are deliberately changed by the absolute value of the power supply to realize steady high-precision torque control, speed up the sine wave tracking control of the input current, and reduce the induced electromotive force. By performing the control, the input current can be controlled up to the region where | v | is low.

In the case of an internal magnet type synchronous motor, the d and q axis inductance ratios and those with large L _q / L _d , especially L
_{When a} motor having a small value of _d is used, field weakening and high-speed field current control are easy.

In the case of a reluctance motor, since the field can be controlled from zero, a power factor of 100% is theoretically obtained.

As described above, the motor has no significant increase in copper loss and iron loss, and the overall efficiency is improved as compared with the conventional system. In the structure of the motor, since the field changes at a high speed, the rotor core must be made of a material that is not massive but stacked and has small iron loss. However, current high-speed motors are often made of such an iron core, and can withstand efficiencies up to about twice the frequency range of the power supply without a drop in efficiency.

In the first aspect, the torque T is equal to the electric input = the mechanical output when the loss and the energy stored in the reactor are ignored.

[0048]

(Equation 1) Holds, and the torque that keeps the rotation speed constant is v = V in phase.
_{If m} sinωt, I = I _m sinωt,

[0049]

(Equation 2) It becomes.

[0050] Also, ideally the absolute value of the induced electromotive force input voltage | vary according substantially this value also d-axis magnetic flux [psi _d of the motor for which you want to control with closer waveform | v. Motor torque T
Is

[0051]

[Equation 3] Is represented by

(Equation 4)

Is as follows. That is, the DC link current may be controlled to follow the q-axis current of the motor, or the q-axis current may be controlled according to a command value modulated with a waveform of | v |.

In this control, the q-axis current is modulated in advance at a frequency of 2ω as described above, with the aim of increasing the speed and accuracy of the control.

In order to realize the second aspect, at the moment when | v | is low, if the field is weakened and the induced electromotive force of the motor can be reduced, the current must be controlled even in this region. This requires a motor capable of instantaneously controlling the induced electromotive force in a wide voltage range and at a high speed twice the frequency of the power supply, and a high-speed field control thereof.

The internal magnet type synchronous motor has recently become capable of weakening the field by 3 to 5 times, and if this is used, a power factor of about 99% can be obtained. This is described below.

FIG. 4 shows waveforms by the field weakening control of the internal magnet type synchronous motor. This motor has a field-weakening limit from the point of efficiency. At that time, the minimum induced electromotive force is V _m , and the maximum is V _M. | v | <since the i = 0 becomes diode non-conductive in the area of V _m, the input current waveform becomes a sine wave which does not conduct part.

FIG. 5 shows the calculated power factor improving effect of this waveform.

[0058] Power Factor (total power factor) cos [phi maximum value and the minimum value of the ratio of the field-weakening magnetic permeability (V _M / V _m) of the e _d in FIG. 4 Tosureba formula (4)
It is represented as

[0059]

(Equation 5) The calculation result more, weak field permeability (V _M / V _m) it is understood that if more than 97% of the power factor can be obtained. At present, a value of 3 or more can be easily obtained, so that the power factor is 99% or more.

[0060] reluctance motors because it until V _m is 0 in the figure, 100% power factor is obtained theoretically.

These can be said to be effective means that sufficiently satisfy the current harmonic and power factor regulation values.

[0062] In addition to this, since they must be as large as possible controlled ripple e _d, by removing the input reactor 11, and may be reduced as much as possible the smoothing capacitor 13. As a result, a long-life, compact, lightweight, low-loss film capacitor can be used for the capacitor, and the loss of the reactor is eliminated, so that the efficiency is further improved.

Further, since the capacitance of the capacitor is drastically reduced (capacity: 1/100), the circuit for preventing the inrush current of the electrolytic capacitor at the time of switch-on, which is conventionally required, becomes unnecessary.

According to the third aspect, since the motor terminal voltage is modulated at twice the frequency of the power supply having the DC link voltage as an envelope, a motor having little effect on the efficiency is required.

Motors with little reduction in efficiency even at the voltage shown in FIG. 3 include a permanent magnet synchronous motor and a reluctance motor. This is because there is no loss factor except for a slight increase in copper loss and iron loss. However, the surface magnet type synchronous motor requires a large current for demagnetization, and it is not an idea that the present invention can be realized by an internal magnet type synchronous motor.

In order to realize this field control at high speed, it is necessary that the d-axis inductance is small. Such an internal magnet type synchronous motor having a high speed rotation (several thousands of rpm) has a voltage of 20% or less of the rated voltage. Field control is possible. In the case of a reluctance motor, there is no problem since the field control can be performed from zero.

As a disadvantage of the present system, there are the following disadvantages due to a large current pulsation.

1. The motor copper loss increases. But,
It is about 1.5 times, and the efficiency is higher than that of the conventional one from the viewpoint of the total loss.

2. Although the iron loss is not much different from that of the conventional one, the magnetic flux density is proportional to the peak value of the voltage, so that a larger iron core is required.

3. Since a pulsating torque twice as large as that of the power supply is generated, uneven rotation and noise are generated. This is also a motor which can be used in many cases like a single-phase AC motor. In fact, the power of a single-phase AC motor whose input voltage and current are sinusoidal changes at twice the frequency of the power supply, and torque pulsation at twice the frequency occurs in steady rotation. This will slightly increase the noise.

However, in a small motor drive system which must be operated by a single-phase power supply, an effect exceeding the above-mentioned disadvantage can be expected.

[0072]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the present invention will be described with reference to the drawings.

FIG. 6 shows the control circuit 6 of the main circuit in detail.

[0074] This circuit is the average torque command T ^*, the input power supply voltage v of the absolute value circuit 6a, the DC link current i _dc, d which receives the rotational angular velocity ω7 of the motor, q-axis current command value i _d ^*, i _q
I _d ^* for calculating the *, i _q ^* arithmetic circuit 6b, which a motor d,
A current control circuit 6c for calculating d and q-axis voltage command values v _d ^* and v _q ^* by comparing with the q-axis current, and rotating coordinate conversions 6d1 and 6d2 for converting between the actual motor coordinate system and the dq coordinate system. , And a gate control circuit 6f for controlling the inverter.

[0075] Among this, i _d ^*, i _q ^* arithmetic circuit 6b This will be described below in this patent-specific circuit. Torque T
Is represented by the following equation.

[0076]

(Equation 6) Since i _d and _iq are pulsating currents having twice the frequency of the power supply, the torque T becomes a pulsating torque including a frequency component twice that of the power supply.

In this case, the command value is the average torque T ^* , but a pulsating torque having twice the frequency of the power supply is actually generated, as in the case of the single-phase motor. In these motors, the induced electromotive force e _o = ψ _a + L _d i _d is reduced by the field control, that is, by reducing i _d, and if | v | <e _o , the current can flow. _dc can be controlled in a sinusoidal manner. However, in the case of the internal magnet type synchronous motor, _eo cannot be set to 0, so that a section in which the current cannot be controlled occurs. However, in the case of the reluctance motor, the sine wave current control is possible in the entire region.

[0078] Since the DC link current i _dc is controlled so that possible close to the DC link voltage e _d, i _q ^* may well prefer modulated at twice the frequency of the power source, and using the absolute value circuit 6a.

Hereinafter, two types of circuit examples will be described.

In the circuit shown in FIG. 7A, the q-axis current for calculating the d- and q-axis steady current command values I _d ^* , I _q ^* passes through the coefficient K6b1 and then is absolutely calculated using the multiplier 6b5. modulating the value 6a outputs, to obtain the command value i _q ^* by following the direct current i _dc in PI circuit 6b2.

[0081] On the other hand, d-axis current command value i _d ^* uses a low-pass filter LPF6b3, v the mean value V and ω of from I _q ^*, are calculated by the arithmetic circuit 6b4 according equation (7). This equation is obtained by calculating a value that allows a current to flow with the minimum field current.

[0082]

(Equation 7)This output is modulated by the output of the absolute value circuit 6a to obtain a command value.
You. These d and q axis command values correspond to the actual d and q axis of the motor.
The voltage command value v is compared with the current by the PI circuit 6c._d ^*, v_q ^*Tona
You.

[0083] Since the q-axis current is torque current, magnetic flux also may be modulated current so substantially similar changes a DC link voltage e _d is expected in e _d and the same waveform to a sine wave. In the case of maximum efficiency, this can be realized by changing this function.

The circuit of FIG. 7B is a circuit for modulating the q-axis current with | v | to obtain a command value i _q ^* . d-axis current by comparing with i _dc and PI circuit 6B7, a circuit capable of sinusoidal input current Sadamari field current. These command value (a) FIG similarly to PI circuit 6c to v _q ^*, v _d ^* is obtained this circuit waveform at circuit for sinusoidal input current by the field control simple d-axis is good.

The current control circuit 6c calculates the P value from the d-axis and q-axis currents.
This is a circuit for obtaining voltage command values v _d ^* , v _q ^* by an I circuit or the like.

FIG. 8 shows a part of the rotation coordinate conversion, in which
This is to mutually convert a coordinate system performed in the -q coordinate system (DC level) into an actual rotating coordinate system. This is based on the commonly used electric angle θ of the motor shaft,
Conversion is performed using the s function (6d1, 6d2).

As a result, the voltage command value of the PWM inverter
v _a ^* , v _b ^* , v _c ^* can be obtained.

Since the coordinate conversion circuit requires a large number of high-speed multiplications, it is conceivable to use a high-speed microcomputer, a DSP or the like. The system will be a control method using these elements.

The gate control circuit 6f shown in FIG. 6 controls the gates of the IGBT inverter and the like according to the three-phase voltage command values v _a ^* , v _b ^* , and v _c ^* . A PWM control technique is used.

The position detection sensor 7 uses a pulse encoder or the like installed on the motor shaft,
A sensorless means for calculating from the current is used.

FIG. 9 shows the result of a simulation for the internal magnet type synchronous motor. Fig. 7 shows the control method.
The control method of (a) is adopted.

FIG. 9A shows the specifications of the motor used here.
It is a 00V, 1.5 kW, 7200 rpm motor. d, q
But it is of relatively small value of the axis inductance ratio _{L q / L d = 1.67,} 97% input power factor is obtained.

The smoothing capacitor used for this was 20 μF
In the conventional single-phase 200 V system, about 2000 μF is used, so that the capacity is about 1/100 of the conventional capacity. The inductance of the power supply is 0.1 mH, which is comparable to the internal inductance of the power supply.

FIG. 9B shows the DC link voltage _ed and the input current waveform. Weakening permeability (a ratio of the maximum value and the minimum value of e _d) is 2. The power factor at this time is 97%, which is very good. Further power factor improvement can be expected by designing the motor so as to increase the field weakening coefficient. Even at this level, the harmonic regulation value is completely satisfied.

FIG. 9C shows the pulsation of the rotation speed, which is small due to the pulsation of the rotation speed caused by the pulsation torque.

FIG. 9D shows that the torque T pulsates intermittently at twice the frequency of the power supply.

FIG. 9E shows a terminal voltage waveform between the a and b phases of the motor. It can be seen that this envelope pulsates at twice the frequency of the power supply as shown in FIG.

[0098]

Since the present invention is constructed as described above, the reactor for improving the power factor of the single-phase full-wave diode rectifier circuit becomes unnecessary, and the smoothing capacitor is reduced to about 1/100 of the conventional one. The size is reduced to about 1/2 of the conventional size, and significant size reduction can be expected. Further, since a heavy reactor can be removed, a weight reduction of about 1/3 can be expected.

Although the loss of the reactor caused a large decrease in efficiency of 3 to 5%, since these are eliminated, the loss of the motor is slightly reduced (about 2%), but the efficiency is improved as a whole system.

Since the number of smoothing capacitors is drastically reduced, a capacitor charging circuit which was required at the time of switch-on in the past becomes unnecessary.

Although the control circuit becomes complicated, the cost is not increased and the cost of the system can be expected to be low because the control circuit is recently mostly implemented by a microcomputer.

Due to the drastic reduction of the capacitance of the smoothing capacitor, it is 3 to 3 times smaller than that of a conventional electrolytic capacitor such as a film capacitor.
A five-fold longer life capacitor can be used and longer life can be expected.

As described above, the present invention is characterized in that it is possible to realize the miniaturization and weight reduction, high efficiency, simplification, low cost, and long life, which are most necessary for a practical system, with almost no deterioration in characteristics.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of the present embodiment.

FIG. 2 is a diagram showing a relationship between a DC link voltage and an input current, and showing that an input current waveform approaches a sine wave when there are many ripples.

FIG. 3 is a diagram schematically showing a terminal voltage waveform when terminal voltage of a motor needs to be modulated in accordance with the ripple in order to include a large amount of ripple in the DC link voltage.

FIG. 4 is a graph showing waveforms of respective parts when field-weakening control is performed by an internal magnet type synchronous motor.

FIG. 5 is a graph showing the result of theoretically determining the relationship between the field weakness and the power factor from FIG. (This is a graph showing the power factor improvement effect of the field weakening.)

FIG. 6 is a diagram showing details of a control circuit. It is a d and q axis current, voltage, and an actual control system diagram.

[7] d, is an explanatory diagram showing two forms q-axis current, calculation methods of the voltage to the method 7 (a) is made to follow the torque i _dc, FIG. 7 (b) i _q ^* This shows a method of causing _idc to follow _idc .

FIG. 8 is an explanatory diagram showing a conversion method of rotational coordinate conversion.

FIG. 9 is an explanatory diagram in which a simulation is performed on an actual internal magnet type synchronous motor to obtain an input current waveform (a power factor of 97% is obtained). FIG. 9A shows simulation parameters (rotational speed 7200 rpm, torque 2N).
FIG. 9B shows a power supply voltage, a current waveform, and a DC link voltage waveform, and FIG. 9C shows a rotation angular velocity waveform (command value: 7200 rpm). (d)
FIG. 9E shows a torque waveform (average: 2 Nm), and FIG. 9E shows an inverter output voltage (line-to-line) waveform.

FIG. 10 is a waveform / power factor improvement circuit using a conventional input reactor. The broken line is the voltage doubler rectifier circuit.

FIG. 11 is a waveform and power factor improvement circuit using a conventional active filter circuit.

[Explanation of symbols]

Reference Signs List 1 single-phase AC power supply 2 diode full-wave rectifier circuit 3 smoothing capacitor 4 PWM inverter 5 motor (internal magnet type synchronous motor or reluctance motor) 6 control circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 5H550 BB01 CC01 DD04 DD09 GG01 GG03 GG05 HA09 HB08 HB16 JJ03 JJ24 JJ26 LL01 LL22 LL35 5H560 BB04 BB12 DA00 DB00 DC12 EB01 RR04 SS07 TT15 UA06 XA02 XA03 BB02 XA02 XA03 XA02 XA03 DD07 DD09 EE01 EE02 EE11 GG01 GG02 GG04 HA04 HB02 JJ03 JJ24 JJ26 LL07 LL12 LL22 LL41

Claims (3)

[Claims] 1. A single-phase diode full-wave rectifier circuit having a single-phase AC power supply as an input, and a small-capacity smoothing capacitor connected to the single-phase diode full-wave rectifier circuit, which is about 1/100 of a smoothing capacitor for a conventional diode full-wave rectifier circuit. A control circuit composed of a control PWM inverter and a motor controls the torque of the motor at twice the frequency of the power supply in advance, thereby realizing an improvement in the input power factor and the waveform of the diode full-wave rectifier circuit. A control device for an inverter for driving a motor, characterized in that: 2. A single-phase diode full-wave rectifier circuit having a single-phase AC power supply as an input, and a small-capacity smoothing capacitor connected to the single-phase diode full-wave rectifier circuit, which is about 1/100 of a smoothing capacitor for a conventional diode full-wave rectifier circuit. A control circuit composed of a control PWM inverter and a motor controls the field of the motor at twice the frequency of the power supply in advance, thereby increasing the current conduction width of the diode full-wave rectifier circuit and increasing the input power factor and waveform. A motor drive inverter control device characterized by realizing improvements. 3. The loss according to claim 1 or 2, wherein an internal magnet synchronous motor or a reluctance motor is used as the motor, and the terminal voltage of the motor is pulsated at twice the frequency of the power supply, thereby greatly increasing the loss. A control device for a motor drive inverter, wherein the control device is configured not to perform the control.