CN102005955B - Dead zone compensation method based on DSP (Digital Signal Processor) controller - Google Patents

Abstract

The invention provides a dead zone compensation method based on a DSP (Digital Signal Processor) controller, comprising the following steps of: firstly configuring a DSP chip to ensure that the comparison value calculated in period interrupt takes an effect after a timer returns to zero, and the comparison value calculated in underflow interrupt takes the effect after the timer reaches a period value; then judging the direction of phase current and calculating the opening point t1 and the closing point t2 of an ideal driving waveform; and finally shifting a comparison register according to the direction of the phase current. The dead zone compensation method realizes full digitization by using a control chip DSP 2812 of the current main-current motor and has more obvious effect than the prior dead zone compensation method.

Description

A kind of dead-zone compensation method of DSP-based control device

Technical field

The present invention relates to the power device field.

Background technology

The action of power device has certain time that turns on and off, and two brachium pontis occur to lead directly in order to avoid up and down, adopt time-delay technique, are called the control Dead Time.Switching frequency is higher, the dead time effect of the PWM that Dead Time causes (pulse width modulation) inverter is more remarkable: namely export fundamental voltage amplitude and reduce, harmonic content increases, the output current distortion is more serious, and inverter switching frequency is higher, and dead time effect is more remarkable: namely export fundamental voltage amplitude and reduce, the harmonic voltage amplitude increases, the output current distortion, the output torque pulsation easily causes motor oscillates in the application scenario of translator.For this problem a lot of different compensation methodes have been proposed, a kind of is to use the control method of space vector that error vector voltage is compensated, it regards error voltage as another voltage vector, and it and given voltage vector is synthesized, the impact that produces in order to compensate the dead band, but control more complicated; Another kind is the mechanism that produces in conjunction with the dead band, and the moment point that turns on and off of switching tube is compensated.At present, dsp controller has been widely used in the inverter control, the programmable dead band control that it carries can be inserted the dead band easily in pwm signal, this paper has proposed a kind of more effective dead area compensation strategy in conjunction with current main-stream motor control chip TSM320F2812 and according to the dead band genesis mechanism, and has verified the validity of the method by asynchronous motor speed-regulating system.

Summary of the invention

Technical problem to be solved by this invention is: a kind of dead-zone compensation method of DSP-based control device is provided, and it is equal to ideal and turns on and off moment point according to the principle of the dead time effect moment point that turns on and off to the switching tube that works.This method is more convenient.

The technical solution adopted in the present invention is: a kind of dead-zone compensation method of DSP-based control device comprises: at first dsp chip is configured, so that the comparison value that calculates in the cycle interruption works after timer returns zero, and the comparison value that interrupts calculating in underflow works after timer reaches periodic quantity; Then judge the direction of phase current, and calculate a t that opens of desirable drive waveforms ₁With pass breakpoint t ₂Carry out shifting processing according to the direction of phase current to comparing register at last.

Advantage of the present invention: realize that with current main-stream motor control chip DSP2812 total digitalization realizes, more obvious than current dead-zone compensation method effect.

Description of drawings

Fig. 1 is three-phase inverter bridge circuit.

Fig. 2 is the inversion waveform behind the adding dead band.

Fig. 3 is the actual drive waveforms (electric current is greater than 0) that turns on and off behind the dead area compensation.

Fig. 4 is the dead area compensation flow chart.

Fig. 5 is the contrast of conventional method and new method.

Embodiment

The present invention is the mechanism that produces in conjunction with the dead band, and the moment point that turns on and off of switching tube is compensated.

The dead band mechanism of production: as shown in Figure 1, in the bridge type inverse system, two switching tubes under the perfect condition on the same brachium pontis are operated in complementary state, consider the time-delay that turns on and off of device itself, general turn off delay time t _OffGreater than opening time-delay t _On, in order to prevent up and down two bridge arm direct pass, need to drive the enough Dead Times of adding between signal at PWM.In dsp system, when counter and comparand register coupling, level overturns, if do not consider the time-delay that turns on and off of dead band and device, its ideal waveform is shown in Fig. 2 a, if consider both factors, then insert in the driving signal of last two IGBT (insulated gate bipolar transistor) behind the waveform of dead band up and down shown in the following Fig. 2 b of drive waveforms of two brachium pontis, high level represents open-minded among the figure, owing to turn on and off time-delay, after adding Dead Time, power device to turn on and off moment point obviously different from perfect condition.

Can be got by Fig. 2, the size of comparator registers has determined the width of effective drive waveforms, but when comparison value very little or very large because the introducing in dead band may make the output significant level lose.

Mutually as example, as shown in Figure 1, T1～T6 is IGBT take three-phase inverter bridge circuit a, and D1～D6 is fly-wheel diode.If the electric current of flow direction motor winding is positive direction, the sense of current that flows to inverter is negative direction.Work as i _a＞0 o'clock, two kinds of operating states are arranged, a kind of is normal operating conditions, and upper pipe T1 is open-minded, and lower pipe T4 turn-offs, and electric current flows through the T1 flow direction motor; And when T1 turn-offed, this moment, electric current was finished afterflow by the antiparallel sustained diode 2 of lower pipe, kept the current direction motor.Work as i _a, two kinds of operating states are equally also arranged at＜0 o'clock: normal T1 turn-offs, and T4 is open-minded, and electric current flows through T4 and forms passage, and when T4 turn-offs, by 1 afterflow of upper pipe inverse parallel sustained diode, keeps electric current to form path.

So according to the dead time effect analysis, work as i _a＞0 o'clock, only have upper bridge-arm tube T1 to work, and work as i _a, only have lower bridge-arm tube T4 to work at＜0 o'clock.The target of this paper compensation is how to make the moment point that turns on and off of the switching tube that works be equal to ideal and turn on and off moment point.Must must separate configuration open constantly and turn-off moment point in ascent stage and the decline stage of triangular carrier like this.In the hardware configuration system of DSP2812, current ripple count mode is set for increasing continuously/subtract counting according to SVPWM seven segmentation waveforms, the fully loaded transportation condition of comparand register is that the value of current counter is 0 or heavy duty when equaling the value of cycle stockpile device, and current ripple timer cycle interruption and underflow are interrupted all effective.The comparison value that calculates in cycle interruption like this can work after timer returns 0, and the comparison value that interrupts calculating in underflow can work after timer reaches periodic quantity.

The below discusses the change (take a mutually as example) of compensation rear drive waveform in two kinds of situation:

Work as current i _a＞0 o'clock, the T4 pulse can be ignored, if guarantee T1 after overcompensation actual turn on and off a little a little consistent with turning on and off of desirable drive waveforms.In Fig. 2, the T1 pipe is opened moment point than a t that opens of desirable drive waveforms ₁Delayed t _d+ t _OnTime, because it reacts on the cycle interruption of a carrier cycle, can be with comparand register CMPR reach, that is:

In cycle interruption, have: CMPR=t ₁-T _d-T _On

In like manner in interrupting, underflow has: CMPR=t ₂+ T _Off

Consider that then dead band and device turn on and off the delay and running waveform as shown in Figure 3.

Work as i _a＜0 o'clock, all the time not conducting of T1, so the T1 pulse can ignore, as long as guarantee that the T4 pulse duration after overcompensation is consistent with T4 ideal pulse width, namely has:

In cycle interruption, have: CMPR=t ₁-T _Off

In like manner in interrupting, underflow has: CMPR=t ₂+ T _On+ T _d

Then interrupt respectively by cycle interruption and underflow that configuration turns on and off a little, make the moment point that turns on and off to the switching tube that works be equal to ideal and turn on and off moment point.

By top discussion as can be known, this dead-zone compensation method depends on the sense of current, in the motor driven systems of SVPWM control, differ a power-factor angle by space voltage vector and Space current vector in phase place, then be easy to obtain the space angle of Space current vector, can obtain the direction of every phase phase current under the current voltage space vector by the relation of coordinate transform, this method can effectively be eliminated the impact of real-time current detection drift.Its realization flow is illustrated in fig. 4 shown below, and in the test, comparison point must be done amplitude limiting processing.

The compensation method of current routine be in an effective impulse compensation because the impact of Dead Time and device time-delay, as shown in Figure 2, namely a PWM cycle internal loss T=T _d+ T _On-T _Off, namely by judging that current polarity makes comparison point reach or the hysteresis of effective switching tube But this method makes PWM ripple hysteresis ideal waveform.

Embodiment:

Present embodiment IGBT module adopts FS150R12KT3, and motor is 22KW, given dead band T _d=3 μ s, the typical case turns on and off to delay time and is T in the time of 25 ℃ _On=0.26 μ s, T _Off=0.42 μ s, carrier frequency f _c=2k, test is at 30H _zCompared behind the conventional dead area compensation shown in the no-load current waveform and harmonic analysis figure below 5, had figure as can be known, adopted its voltage distortion rate of this test method THD=2.4%, its effect is apparent.

Claims (2)

1. the dead-zone compensation method of a DSP-based control device, it is characterized in that comprising: at first dsp chip is configured, so that the comparison value that calculates in the cycle interruption works after timer returns zero, and the comparison value that interrupts calculating in underflow works after timer reaches periodic quantity; Then judge the direction of phase current, and calculate opening a little of desirable drive waveforms

With the pass breakpoint

Carry out shifting processing according to the direction of phase current to comparing register at last;

The method that dsp chip is configured comprises: current ripple count mode is set for increasing continuously/subtract counting according to SVPWM seven segmentation waveforms, the fully loaded transportation condition of comparand register is that the value of current counter is 0 or heavy duty when equaling the value of cycle stockpile device, and current ripple timer cycle interruption and underflow are interrupted all effective;

The method of judging the direction of phase current comprises: the power-factor angle that differs in phase place according to space voltage vector and Space current vector, obtain the space angle of Space current vector, then obtained the direction of every phase phase current under the current voltage space vector by the relation of coordinate transform;

The method of carrying out shifting processing to comparing register comprises:

Work as phase current

The time,

In cycle interruption, have:

,

In interrupting, underflow has:

Work as phase current

The time,

In cycle interruption, have:

,

In interrupting, underflow has:

Wherein CMPR is comparand register, T _dBe Dead Time, T _OnFor opening time-delay, T _OffBe turn off delay time.

2. method according to claim 1 is characterized in that: described dsp chip employing TMS320F2812.

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