CN1087117C - Apparatus and method for controlling induction motor - Google Patents

Abstract

The present invention relates to a control device of an induction motor, which is provided with an inverter and a control device, wherein the inverter transforms a DC voltage into an AC voltage with variable frequency and variable voltage by pulse width modulation control; the control device controls the output voltage of the inverter; according to the excitation current component instruction and the torque current component instruction of a primary current in an induction motor driven by the inverter, the control device calculates voltage component instructions corresponding to the components; moreover, the control device controls the output voltage of the inverter according to the modulation rate calculated by the voltage component instruction. The present invention is characterized in that the present invention also has the means of testing a torque current component from the primary current of the induction motor, the means of correcting the torque current component instruction according to the deviation of the torque current component value and the instruction value thereof, the means of correcting the output frequency of the inverter according to the corrected torque current component instruction and the means of limiting the modulation rate over the specified value or under any condition. Therefore, without switching a control structure, the induction motor can be continuously well controlled by a vector from a low velocity area to a high velocity area with a voltage instruction value above the output maximum voltage of the inverter determined by a DC voltage (a PWM pulse mode is a monopulse area).

Description

The control device of induction motor and method

Technical field

The present invention relates to the vector control of induction motor, relate in particular at the frequency height and can not carry out control device and the method that the induction motor of vector control also can be carried out in voltage-controlled zone.

Background technology

To disclose 1993 No. 83976 communique in Japanese patent of invention on the books to driving technology that rolling stock carries out vector control with the induction motor of electric locomotive.In addition, rolling stock generally in the high-speed cruising district, to greatest extent utilizes DC power supply voltage for the switching loss that reduces inverter reaches with electric locomotive, uses the control of pwm pulse mode as single pulse mode.But the cybernetics at the 33rd railway of Japan utilizes in domestic Conference Papers collection (in November, 1996) 247-250 page or leaf " using the driver for vehicle of the vector control " literary composition, is putting down in writing the technology of also carrying out vector control in the single pulse mode that can not control this voltage swing.

Disclose in the vector control of 1993 No. 83976 communique record in above-mentioned Japanese patent of invention, except 2 current control units of 2 voltage command signals revising vector control according to the deviation of excitation current instruction value and the exciting current measured and torque current command value and the deviation of the torque current of measuring, also be provided with and revise the 3rd current control unit that slip frequency is used, because control structure complicates, thus when having usefulness microcomputer operational order signal operation time elongated problem.In above-mentioned " using the driver for vehicle of vector control " document, single pulse mode must be added the computing of magnetic flux correction value in addition, the promptly additional feedback that weakens excitation.Above-mentioned two kinds of conventional arts all must be to switching with single pulse mode and the control system of otherwise controlling.

In addition, except above-mentioned conventional art, also have Japanese patent of invention No. 32788 communique of open nineteen ninety.The formation of the vector control of this communique record comprises part according to each components operation voltage instruction of exciting current and torque current, 1 secondary frequencies is sent the current control system of instruction so that the torque current actual value becomes the part of torque current command value and from the part of the above-mentioned voltage instruction of 1 secondary frequencies ordering calculation that obtained as shown in figure 16.

But the problem that the vector control of this communique record exists is, if the pwm pulse mode becomes pulse, in the time of can not carrying out voltage control, just can not carry out vector control, this corresponding measure do not had any explanation.

The objective of the invention is to, a kind of control device and method of induction motor are provided, it is when carrying out vector control to induction motor, can be with simpler control structure, to from low regime to the DC power supply voltage that utilizes the PWM inverter to greatest extent, the pwm pulse number can carry out good vector control continuously for the high velocity of pulse, and switching controls structure not.

Disclosure of an invention

The control device of induction motor of the present invention has by pulse width modulation control and dc voltage conversion is become the inverter of interchange of variable-frequency variable-voltage and the control device of control inverter output voltage, this control device draws the component of voltage instruction corresponding with described each component according to instruction of the excitation current component in the primary current of the induction motor that is driven by this inverter and torque current component ordering calculation, and come the output voltage of control inverter according to the modulation rate of obtaining by the instruction of described component of voltage (output voltage instruction), it is characterized in that also having: the unit that detects torque current component from described induction motor primary current; Revise the unit of described torque current component instruction according to the deviation of this torque current component value of measuring and its command value; Revise the unit of the output frequency of described inverter according to the torque current component instruction of this correction; And the unit that limits described modulation rate size, the condition that this unit limits described modulation rate size is that the umber of pulse in during phase voltage half period of described inverter output is a pulse, perhaps, the value of the described modulation rate size of restriction is set at the exportable maximum voltage of the described inverter that determines by described direct voltage, and, during described modulation rate big or small confined, export described excitation current component instruction from the instruction generating unit that produces definite value.

The simple declaration of accompanying drawing

Fig. 1 is the block diagram that the control device of one embodiment of the invention is shown.Fig. 2 is the detailed pie graph of the modulation rate arithmetic unit among Fig. 1.Figure 3 shows that the simulation example that the present invention controls.Figure 4 shows that the torque response simulation example that the present invention controls.

The optimal morphology that carries out an invention

Below with Fig. 1 one embodiment of the invention are described.In the figure, filtered from the direct current that DC power supply 11 is supplied with by filtering capacitor 13, supply with pulse width modulation (hereinafter referred to as PWM) inverter 1 as supply convertor.

PWM inverter 1 will become 3 cross streams voltages as the dc voltage conversion of power supply, and this alternating voltage is supplied with induction motor 2.2 of this induction motors are as drive source driving electric locomotive driving.

Current command generator produces excitation current instruction value Id* and torque current command value Iq*.

Current controller 4 is according to torque current command value Iq ^*And the back is the deviation of torque current detected value Iq with the output of coordinate converter 5 of narration, generates revised torque current command value Iq ^*, this command value Iq ^*Be transfused to voltage instruction arithmetic unit 6 and slip angular frequency arithmetic unit 7.

Slip angular frequency arithmetic unit 7 is according to excitation current instruction value Iq ^*And revised torque current command value Iq ^*, output slip angular frequency command value ω s ^*

Voltage instruction arithmetic unit 6 is according to excitation current instruction value Iq ^*, revised torque current command value Iq ^*Reach 1 angular frequency command value ω 1 that the back will be narrated ^*, be Vd to the instruction of 2 component of voltages of the rotating magnetic field coordinate system of supplying with induction motor 2 ^*And Vq ^*Carry out computing, and output to polar coordinate transform device 8.

Polar coordinate transform device 8 will be used Vd ^*And Vq ^*The voltage vector of expression is transformed into the big or small V0 and the phase place δ of voltage vector.

On the other hand, the induction motor speed omega r that is measured by speed detector 16 is slip angular frequency command value ω s in the output of adder 17 and slip angular frequency arithmetic unit 7 ^*Addition generates angular frequency command value ω 11 time ^*This 1 angular frequency command value ω 1 ^*Supply with integrator 18 and voltage instruction arithmetic unit 6.

18 couples of 1 angular frequency command value ω 1 of integrator ^*Carry out integration, computing coordinate basis signal θ.

Coordinate converter 5 inputs are by current detector 15u, the 15v of the output current that detects PWM inverter 1, inverter output current iu, iv, the iw that 15w measures, and being transformed into the excitation current component Id and the torque current component Iq of rotating magnetic field coordinate system by coordinate basis signal θ, Iq outputs to current controller 4.

Adder 19 is that the output of coordinate basis signal θ and polar coordinate transform device 8 is the phase place δ addition of voltage vector with the output of integrator 18, and output θ '.

Modulation rate arithmetic unit 10 is according to the signal of voltage detector 14 outputs that the direct voltage VFC as the power supply of supply convertor is detected, restriction is the big or small V0 of voltage vector as the output of polar coordinate transform device 8, so that it does not exceed the maximum voltage that supply convertor can be exported, and output modulation rate Vc.

At pwm signal arithmetic unit 9, produce switching pulse Su, Sv, Sw by the output Vc of modulation rate arithmetic unit 10 and the output θ ' of adder 19, supply with PWM inverter 1.

Describe each part mentioned above below in detail.

At coordinate converter 5, according to formula (1) from for example coordinate basis signal θ and inverter output current iu, iv, iw computing excitation current component Id and torque current component Iq. $\left[\begin{array}{c}\mathrm{Id}\\ \mathrm{Iq}\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}\cos \mathrm{\θ}& \cos (\mathrm{\θ}-\frac{2\mathrm{\π}}{3})& \cos (\mathrm{\θ}+\frac{2\mathrm{\π}}{3})\\ -\sin \mathrm{\θ}& -\sin (\mathrm{\θ}-\frac{2\mathrm{\π}}{3})& -\sin (\mathrm{\θ}+\frac{2\mathrm{\π}}{3})\end{array}\right]\left[\begin{array}{c}\mathrm{iu}\\ \mathrm{iv}\\ \mathrm{iu}\end{array}\right]...\left(1\right)$

As current controller 4 for example usage ratio, integral control.Formula (2) is the one example.Thus according to current instruction value Iq ^*With the deviation of torque current detected value Iq, export revised current instruction value Iq ^* ${\mathrm{Iq}}^{**}={\mathrm{Iq}}^{*}+(K1+\frac{K2}{s})({\mathrm{Iq}}^{*}-\mathrm{Iq})...\left(2\right)$

In the formula, K1, K2 are respectively proportionality coefficient and integral coefficient, and s is a Laplacian.

Formula (3) is an example of voltage instruction arithmetic unit 6. $\left[\begin{array}{c}{\mathrm{Vd}}^{*}\\ {\mathrm{Vq}}^{*}\end{array}\right]=\left[\begin{array}{c}r1\\ L1{\mathrm{\ω}1}^{*}\end{array}\right]\left[\begin{array}{c}-\mathrm{Ls}{\mathrm{\σ\ωI}}^{*}\\ r1\end{array}\right]\left[\begin{array}{c}{\mathrm{Id}}^{*}\\ {\mathrm{Iq}}^{**}\end{array}\right]...\left(3\right)$

In the formula, r1 is 1 resistance of induction motor 2, and Ls σ is a leakage inductance, and L1 is 1 inductance.

Formula (4) is one of slip angular frequency arithmetic unit 7 example. ${\mathrm{\&omega;s}}^{*}=\frac{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="C9718205400121.png"\; state="\{\{state\}\}">r</figure-callout>}2\&CenterDot;{\mathrm{Iq}}^{**}}{M\&CenterDot;{\mathrm{Id}}^{*}}...\left(4\right)$

In the formula, r2 is 2 resistance of induction motor 2, and M is mutual inductance.

Polar coordinate transform device 8 usefulness formulas (5), (6) expression. $V0=\sqrt{{\mathrm{Vd}}^{*2}+{\mathrm{Vq}}^{*2}}...\left(5\right)$ $\mathrm{\&delta;}=\frac{\mathrm{\&pi;}}{2}-{\tan }^{-1}\left(\frac{{\mathrm{Vd}}^{*}}{{\mathrm{Vq}}^{*}}\right)...\left(6\right)$

Fig. 2 illustrates one of modulation rate arithmetic unit 10 example.By divider 201, with the output V0 of filtering capacitor voltage VFC depolarization coordinate converter 8, its output is normalized into modulation rate Vc ' through coefficient multiplier 202, and this is worth input chopper 203.Not overshoot of the modulation rate Vc ' value that amplitude limiter 203 is imported modulation rate (voltage instruction) Vc of output relatively.The formation of Fig. 2 is represented then as the formula (7) with arithmetic expression.(P6) $\mathrm{Vc}=\min (\sqrt{\frac{2}{3}},\frac{\mathrm{\&pi;}}{2},\frac{V0}{\mathrm{VFC}},1)...\left(7\right)$

In the formula, modulation rate Vc has passed through range conversion, and the voltage when making the PWM inverter output voltage for maximum single pulse mode is 1.Min () is for getting the function of minimum value, and result of calculation surpasses at 1 o'clock Vc is restricted to 1.From formula (7), the maximum V0max of V0 can write an accepted way of doing sth (8). $V0\max =\sqrt{\frac{3}{2}},\frac{2}{\mathrm{\&pi;}},\mathrm{VFC}...\left(8\right)$

Adopt Fig. 1 of above explanation and the control structure shown in formula (1)-(7), extremely can utilize the PWM single pulse mode high velocity of the direct voltage of PWM inverter 1 can both carry out good control to greatest extent low regime.

Below the action in the above-mentioned formation is described.

The situation of the low regime that the maximum voltage that may be exported by the supply convertor of the direct voltage decision of power supply the voltage instruction value ratio is little describes earlier.The output V0 of polar coordinate transform device is because than little by the voltage V0max of modulation rate arithmetic unit 10 restrictions, so Vc＜1.At this moment, the voltage unit error of PWM inverter 1 output, the parameter of induction motor 2 is consistent with the parameter that voltage instruction arithmetic unit 6, slip angular frequency arithmetic unit 7 use, under such ideal conditions, and 1 output and the on all four voltage of voltage instruction value of PWM inverter.Its result, the output Id of current command generator 3 ^*And Iq ^*In full accord with the output Id and the Iq of coordinate converter, can carry out vector control.In fact, since the output voltage error of PWM inverter 1 and the parameter change of induction motor 2 etc., Id ^*, Iq ^*And the meeting generation is inconsistent between Id, the Iq, but in this case, controls by current controller 4, makes Iq and Iq ^*Consistent.For example, if 2 resistance r2 that consider induction motor are than the big situation of employed r2 in the computing of slip angular frequency arithmetic unit 7, then because the slip angular frequency command value ω s of slip angular frequency arithmetic unit 7 outputs ^*Littler than the value that should export originally, so the induction motor electric current diminishes Iq ^*Just inconsistent with Iq.At this moment, current controller 4 is inconsistent and work in order to eliminate this, strengthens output Iq ^*Its result, slip angular frequency command value ω s ^*Become big, the error that the change of modifying factor parameter causes, so, even parameter error is arranged slightly,, also can stably carry out vector control by the work of current controller 4.

Then the voltage that the outputs to induction motor situation the during high velocity of (pulse mode of PWM is a pulse) more than the exportable ceiling voltage of supply convertor is described.Even under the free from error ideal conditions of the parameter of induction motor, the big or small V0 of the voltage vector command value of polar coordinate transform device 8 outputs also can be bigger than the maximum voltage V0max that PWM inverter 1 may be exported, and can produce inconsistent between voltage instruction value and output voltage.Therefore, the output Id of current command generator 3 ^*, Iq ^*Will be inconsistent with output Id, the Iq of coordinate converter 5.

Added modulation rate arithmetic unit 9 in order to solve the problem that exists under this condition.

This arithmetic unit 9 promptly limits with this value when the voltage instruction Vc ' that calculates as shown in Figure 2 is bigger than exportable maximum voltage V0max, and the value after will limiting is exported as modulation rate (output voltage instruction) Vc of inverter.

Must will be equivalent to Vc ' in vector control in the past feeds back with the amount of the difference of V0max.For example, in above-mentioned the driver for vehicle of vector control " use " document, adjust so that as the excitation current instruction value Id of the output of current command generator 3 ^*Reduce (in action specification of the present invention, will be like this to Id ^*Excitation current instruction value when controlling through adjusting laggard row vector is called Id ^*).

Just can carry out vector control but the present invention needn't carry out aforesaid feedback, this is very big characteristics.With regard to these characteristics, below describe control principle in detail.

Current controller 4 among Fig. 1 is in low regime as described above, and to compensate be major function in change to parameter, and in high velocity, this controller carries out work, so that because of the inconsistent Iq that causes of above-mentioned voltage ^*Consistent with the error concealment of Iq.

For example, if Vc ' is bigger than V0max, then corresponding to its difference, the output Id of current controller 4 ^*Compare Id ^*Greatly.Consequently, at the poised state of control, the output Iq of current controller 4 ^*Output Id with current command generator 3 ^*Ratio be Iq ^*/ Id ^*Ratio Iq when carrying out vector control originally ^*/ Id ^*Equate.The output of slip angular frequency arithmetic unit 7 is slip angular frequency command value ω s at this moment ^*As seen from formula (4), equate when carrying out vector control, and at adder 17 and integrator 18 from ω s ^*The coordinate basis signal θ that calculates also equates.Similarly, in the time before control reaches poised state, the speed omega r of induction motor 2 can be regarded as indeclinablely, decide the response time of current controller 4 thereby the output Vd of voltage instruction arithmetic unit 6 like this ^*, Vq ^*Ratio Vq ^*/ Vd ^*Also with formula (3) no change.

Therefore, also equate when carrying out vector control originally according to the output δ of the polar coordinate transform device 8 of formula (6).Its result, the θ ' that adder 19 calculates also equates, therefore, is applied in identical voltage when carrying out common vector control on the induction motor 2, coordinate converter 5 is as output Id, Iq under the perfect condition, the Id that the value of output when carrying out common vector control equated ^*And Iq ^*Current controller 4 is because contain integral element, so, even input Iq ^*Equate Iq with Iq ^*Also with than Iq ^*Big value is poised state.

Promptly, even when the output V0 of polar coordinate transform device 8 is bigger than the maximum V0max of the voltage of PWM inverter 1 output, according to the present invention, because the effect of current controller 4, do not adjust current command generator 3, equivalence fully during yet with vector control that the excitation current instruction value is descended.In other words, in case the output voltage of PWM inverter is fixed on the maximum voltage that can export, promptly weaken excitation control automatically.In addition, when this was controlled at the direct voltage change of power supply, also owing to the effect of above-mentioned control system, its influence was revised automatically, under stable state, is controlled to torque current Iq and torque current command value Iq all the time ^*Consistent.

Fig. 3 reaches simulation drawing till maximum, voltage reach stable zone to the action of the control system of Fig. 1 from inactive state to the inverter output voltage of induction motor.Fig. 3 (a) illustrates the variation for the induction motor speed omega r of time t, shows that induction motor quickens in time.Fig. 3 (b) illustrates output V0 to polar coordinate transform device 8 to carry out range conversion and is transformed into the variation that takes place in time with the output Vc of the Vc ' of the identical range of modulation rate Vc and modulation rate arithmetic unit 10.Near 18 seconds, the Vc ' device 203 that is limited limits, after this Vc (maximum voltage that the PWM inverter can be exported) stuck-at-.Fig. 3 (c) illustrates output Id, the Iq of coordinate converter 5 and the output Id of current command generator 3 ^*, current controller 4 output Iq ^*The variation of Fa Shenging in time.Establish output Id this moment from current command generator 3 ^*And Iq ^*All the time certain.As can be seen, before voltage is limited, Id and Id ^*And Iq and Iq ^*Be consistent, but after voltage becomes certain moment, Iq ^*Because the effect of current controller 4, become big with the increase of induction motor speed.On the other hand, voltage reaches the certain moment relative Id of Id afterwards ^*Gradually diminish.That is, weaken excitation control.

In addition, unshownedly in the drawings be Iq ^*By the effect of current controller 4, send the certain command value consistent with Iq, and Id ^*Command value also be set at necessarily.

Fig. 3 (d) illustrates the variation that the induction motor torque takes place in time, because before the moment that voltage is restricted, and torque current command value Iq ^*And excitation current instruction value Id ^*Be certain, so torque is also certain.After the moment, even because command value is certain, the voltage of supplying with induction motor also is limited, so by weakening the degree that excitation is carried out, the automatically corresponding decline of torque in voltage limit.Like this as can be known, also obtain confirming through simulation, can realize the vector control continuous from low speed to high speed based on the control action of above-mentioned control principle.

Below vector control from different angle proof present embodiment.Fig. 4 is illustrated near one of the torque response simulation in the certain zone of voltage (25 seconds of Fig. 3) example.In the figure, for the variation of torque instruction value Tref, though the response of the torque T of induction motor has transitional slightly vibration, in addition, T is rapid for the Tref response, and hence one can see that, utilizes present embodiment can carry out vector control.In addition, the transitionality of above-mentioned generation vibration by the control constant of current controller 4 being set for the optimum value that adapts with constant as the induction motor of controlling object, can make its reduction.

As mentioned above, if adopt present embodiment, as long as 1 current controller and modulation rate arithmetic unit with the controlling torque electric current, do not change control structure, the high velocity that just can surpass the maximum voltage (the pwm pulse mode is the zone of pulse) that to export by the inverter of direct voltage decision to the size of voltage instruction in low regime, induction motor is carried out vector control continuously, is the high velocity of pulse at potential pulse especially, and torque also can respond rapidly.

In addition, because as shown in Figure 2, along with the change of DC power supply voltage VFC, Vc revises automatically to modulation rate, so can not be subjected to the influence of DC power supply variation in voltage, presses the output of command value control inverter fully.

Also have, in the above-described embodiments, the situation that limits value with voltage clipper is set at the exportable maximum voltage of supply convertor is narrated, but the limits value of voltage clipper also can be set at the voltage arbitrarily that desire begins to weaken excitation control, lights arbitrarily to carry out from this and weakens excitation control.Therefore,, excitation control can be just weakened, therefore traditional excitation current instruction Id needn't be specially prepared in advance as long as change this set point ^*Weaken excitation mode, can simple control structure.

In addition in the present embodiment, only torque current is provided with current controller, but, also can current controller all be set to exciting current and torque current in the also little low regime of exportable maximum voltage of voltage instruction value ratio by the supply convertor of the direct voltage decision of power supply.Just when the output V0 of polar coordinates arithmetic unit 8 is also bigger than exportable maximum voltage V0max, must switching controls, so that the current controller of exciting current is failure to actuate.This be because, also can be clear from Fig. 3, be excitation current instruction value Id as the output of current command generator 3 this moment ^*With the output as coordinate converter 5 is that exciting current detected value Id may not be consistent, so, if add according to Id ^*Making normal deviate with the deviation of Id is 0 the current controller with integral element, and control of the present invention is just untenable.

The possibility of using on the industry

If employing the present invention, switching controls structure not just can be to induction conductivity from low regime to voltage instruction The size of (modulation rate) surpasses the exportable maximum voltage of inverter (the pwm pulse mode that is determined by DC voltage Be the one-pip area) high velocity carry out continuously good vector controlled. Therefore, the present invention can use certainly In the control of the railway electric locomotive that requires certain torque response characteristic, also can be applied at road up The electric automobile of sailing.

Claims (3)

1. the control device of an induction motor, have by pulse width modulation control and dc voltage conversion is become the inverter of interchange of variable-frequency variable-voltage and the control device of control inverter output voltage, this control device draws the component of voltage instruction corresponding with described each component according to instruction of the excitation current component in the primary current of the induction motor that is driven by this inverter and torque current component ordering calculation, and control the output voltage of described inverter according to the modulation rate of obtaining by the instruction of described component of voltage (output voltage instruction), it is characterized in that also having:

Detect the unit of torque current component from described induction motor primary current; Revise the unit of described torque current component instruction according to the deviation of this torque current component value of measuring and its command value; Revise the unit of the output frequency of described inverter according to the torque current component instruction of this correction; And the unit that limits described modulation rate size, the condition that this unit limits described modulation rate size is that the umber of pulse in during phase voltage half period of described inverter output is a pulse, perhaps, the value of the described modulation rate size of restriction is set at the exportable maximum voltage of the described inverter that determines by described direct voltage, and

During described modulation rate big or small confined, export described excitation current component instruction from the instruction generating unit that produces definite value.

2. the control device of induction motor according to claim 1 is characterized in that, described modulation rate is carried out normalized according to the size of the described direct voltage of measuring.

3. the control method of an induction motor, this method utilization becomes the inverter of the interchange of variable-frequency variable-voltage and constant pressure frequency conversion to come control of induction dc voltage conversion, go out the component of voltage instruction corresponding according to instruction of the excitation current component in the primary current of this induction motor and torque current component ordering calculation with described each component, and according to the modulation rate of obtaining by described component of voltage instruction (output voltage instruction), control the output voltage of described inverter, it is characterized in that

After the control of described variable-frequency variable-voltage becomes the control of described constant pressure frequency conversion, described modulation rate is limited in setting, and, increases described torque current component instruction along with the increase of described inverter output frequency.

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