CN103888005A - Compensation voltage algorithm of inverter dead zone in motor control system and interpolation method - Google Patents

Abstract

The invention discloses a compensation voltage algorithm of an inverter dead zone in a motor control system and an interpolation method. The compensation voltage algorithm calculates the inverter dead zone effect error time Terr, equivalent error time Tave caused by conduction and voltage reduction of a power transistor and a diode in one PWM cycle is included, U-phase output end voltage error Vao_err caused by the Tave equivalent error time in one PWM cycle is calculated, three-phase voltage error of the inverter is thus obtained, and the compensation voltage of the inverter dead zone is obtained by the phase voltage error. According to the interpolation method, through sampling three-phase current of the inverter and carrying out filter processing by a current sensor, clark conversion, park conversion, inverted park conversion and inverted clark conversion are respectively carried out on the three-phase current after filter, three-phase current signals after filter are obtained, a zero-crossing threshold is set, and inverter compensation voltage interpolation can be carried out when the absolute value of the three-phase current is more than the threshold. With the algorithm, the compensation voltage can be obtained, and by adopting the interpolation method, the inverter dead zone effect can be avoided.

Description

Bucking voltage algorithm and the interpolating method of Inverter Dead-time in electric machine control system

Technical field

The present invention relates to bucking voltage algorithm and the interpolating method of Inverter Dead-time in a kind of electric machine control system.

Background technology

In the time of motor low cruise, especially, in the time of underloading, because Inverter Dead-time effect causes phase current and phase voltage to distort and produces zero current clamp phenomenon, increase the current harmonic content of frequency converter output; This current harmonic content has increased magnetic linkage distortion and the torque pulsation of motor.In current electric machine control system, before space vector pulse width modulation (SVPWM) is controlled, how inverter obtains three-phase voltage U accurately _a, U _b, U _c, to avoid Inverter Dead-time effect, mainly contain following method: utilize merely PID to regulate and control, directly by i _d, i _qcarry out pi adjusting and obtain u _d, u _q, then obtain U through contrary park conversion and contrary clark conversion _a, U _b, U _c; But the error voltage that this kind of method can not full remuneration causes due to Inverter Dead-time effect, its reason comprise following some: first, due to the restriction of electric machine control system software or hardware, current sample has certain bandwidth, governing speed is restricted, secondly, it is a time delay or single order link that electric current regulates, and the frequency-domain expression that current PI regulates is generally

k _pfor the proportionality coefficient of PID adjuster, k _ifor the integral coefficient of pi regulator, T _sfor the sampling time, z is complex variable, the pull-type conversion of sampled signal is transplanted to represent to the z conversion of discrete-time signal, and the impact of electric current governing speed, and Inverter Dead-time effect can not be compensated completely.

Be illustrated in figure 1 the schematic diagram that Inverter Dead-time effect produces, in motor actual motion, inverter output current is subject to dead band delay time, power device make-and-break time, the impacts such as the conduction voltage drop of power device and diode and DC power supply pulsation.Wherein, T _onfor power tube service time, T _offfor power tube turn-off time, T _dfor dead band delay time, U _tfor power tube conduction voltage drop, U _dfor diode current flow pressure drop.

Summary of the invention

Technical problem to be solved by this invention is to provide bucking voltage algorithm and the interpolating method of Inverter Dead-time in a kind of electric machine control system, this algorithm can obtain the bucking voltage of Inverter Dead-time, utilize this interpolating method effectively to avoid the dead time effect of inverter, dynamic response can improve maximum speed that motor can reach and motor low speed time, reduces the harmonic content of electric machine control system.

For solving the problems of the technologies described above, in electric machine control system of the present invention, the bucking voltage algorithm of Inverter Dead-time comprises the steps:

Step 1, at taking into account inverter dead band delay time T _d, inverter power pipe service time T _on, turn-off time T _off, power tube conduction voltage drop and diode current flow pressure drop influence condition under, take inverter U mutually as example, within a PWM cycle, according to desirable and actual weber area equate to calculate Inverter Dead-time effect errors time T _errfor:

T _err＝(T _d+T _on-T _off+T _ave)*sgn(i _U) (1)

Wherein $T_{\mathrm{ave}}=\left\{\begin{array}{c}\frac{T_{\mathrm{on}}{U}_d+T_{\mathrm{off}}{U}_T}{T_S},i_U>0\\ \frac{T_{\mathrm{off}}{U}_d+T_{\mathrm{on}}{U}_T}{T_S},i_U<0\end{array}\right\}---\left(2\right)$

In formula (1) and formula (2), T _sbe sampling time, a U in the PWM cycle _dfor diode current flow pressure drop, U _tfor power tube conduction voltage drop, i _ufor inverter U phase current, T _aveit is power tube and the caused equivalent error time of diode current flow pressure drop in the PWM cycle;

Step 2, calculating T _avethe U phase output terminal voltage error U that the equivalent error time causes within a PWM cycle _{ao_err},

$U_{\mathrm{ao}\_\mathrm{err}}=-\frac{T_{\mathrm{err}}}{T_S}{U}_{\mathrm{dc}}\&CenterDot;\mathrm{sgn}\left(i_U\right)---\left(3\right)$

From formula (3) and formula (2), U phase output terminal voltage error U _{ao_err}be subject to sampling time T _sand DC bus-bar voltage U _dcimpact;

Step 3, according to the calculating of inverter U phase output terminal voltage error in step 1 and step 2, push away to such an extent that the phase voltage error of inverter three-phase is:

$U_{\mathrm{an}\_\mathrm{err}}=-\frac{T_{\mathrm{err}}}{T_s}{U}_{\mathrm{dc}}\left[\frac{2\mathrm{sgn}\left(i_U\right)-\mathrm{sgn}\left(i_V\right)-\mathrm{sgn}\left(i_W\right)}{3}\right]---\left(4\right)$

$U_{\mathrm{bn}\_\mathrm{err}}=-\frac{T_{\mathrm{err}}}{T_s}{U}_{\mathrm{dc}}\left[\frac{2\mathrm{sgn}\left(i_V\right)-\mathrm{sgn}\left(i_U\right)-\mathrm{sgn}\left(i_W\right)}{3}\right]---\left(5\right)$

$U_{\mathrm{cn}\_\mathrm{err}}=-\frac{T_{\mathrm{err}}}{T_s}{U}_{\mathrm{dc}}\left[\frac{2\mathrm{sgn}\left(i_W\right)-\mathrm{sgn}\left(i_U\right)-\mathrm{sgn}\left(i_V\right)}{3}\right]---\left(6\right)$

In formula (4), formula (5), formula (6), U _{an_err}for U phase output terminal error voltage, U _{bn_err}for V phase output terminal error voltage, U _{cn_err}for W phase output terminal error voltage, i _ufor inverter U phase current, i _vfor inverter V phase current, i _wfor inverter W phase current, U _dcfor DC bus-bar voltage;

Step 4, according to the each phase output terminal error voltage of inverter of formula (4), formula (5) and formula (6), the bucking voltage that can obtain Inverter Dead-time is respectively:

U _{un_comp}＝-U _{an_err} (7)

U _{vn_comp}＝-U _{bn_err} (8)

U _{wn_comp}＝-U _{cn_err} (9)

Wherein: U _{un_comp}for the bucking voltage of inverter U phase, U _{vn_comp}for the bucking voltage of inverter V phase, U _{wn_comp}for the bucking voltage of inverter W phase.

In electric machine control system, the bucking voltage interpolating method of Inverter Dead-time comprises the steps:

Step 1, from bucking voltage algorithm, bucking voltage is relevant with inverter three-phase current polarity, by the current sensor inverter three-phase current i obtaining respectively that samples _u, i _vand i _w, and to inverter three-phase current i _u, i _vand i _wcarry out clark and park conversion and obtain direct current i _d, i _q;

Step 2, to direct current i _d, i _qcarry out single order low-pass filtering treatment, obtain three-phase current i after filtering _u0, i _v0, i _w0, by three-phase current i after filtering _u0, i _v0, i _w0carry out contrary park and obtain three-phase current i against clark conversion _u, i _v, i _w, the three-phase current i now obtaining _u, i _v, i _wit is the current signal after after filtering;

Step 3, setting three-phase current i _u, i _v, i _wthe threshold value of zero crossing is i _threshold,

When | i _u| > i _thresholdtime, inverter interpolation U phase bucking voltage,

When | i _v| > i _thresholdtime, inverter interpolation V phase bucking voltage,

When | i _w| > _thresholdtime, inverter interpolation W phase bucking voltage;

Step 4, inverter U/V/W phase bucking voltage obtain U through clark conversion _{an_comp}and U _{bn_comp}, and regulate and control the V obtaining with PID respectively _d, V _qthrough the V of contrary park conversion output _a, V _bbe added, the voltage that is added gained can be obtained to U phase phase voltage U through contrary clark conversion _u, V phase phase voltage U _v, W phase phase voltage U _w, U _uu _vu _wthe input voltage that three-phase phase voltage is controlled as inverter SVPWM.

Because bucking voltage algorithm and the interpolating method of Inverter Dead-time in electric machine control system of the present invention have adopted technique scheme, this bucking voltage algorithm is, according to desirable and actual weber area equate calculating Inverter Dead-time effect errors time T _err, wherein comprise power tube and the caused equivalent error time T of diode current flow pressure drop in the PWM cycle _ave, calculate T _avethe U phase output terminal voltage error U that the equivalent error time causes within a PWM cycle _{ao_err}, pushing away accordingly to obtain the phase voltage error of inverter three-phase, the error of known inverter phase current is the ratio of phase voltage error and impedance, is obtained the bucking voltage of Inverter Dead-time by phase voltage error.This interpolating method is by the sample inverter three-phase current that obtains respectively make single order low-pass filtering treatment of current sensor, three-phase current after filtering is made respectively clark, park conversion and contrary park, converted against clark, obtain three-phase current signal after filtering, the threshold value of three-phase current zero crossing after setting filtering, in the time that three-phase current absolute value is greater than this threshold value after filtering, carry out the interpolation of inverter bucking voltage.This algorithm obtains the bucking voltage of Inverter Dead-time, and adopts this interpolating method effectively to avoid the dead time effect of inverter, the dynamic response when maximum speed that raising motor can reach and motor low speed, the harmonic content of minimizing electric machine control system.

Accompanying drawing explanation

Below in conjunction with drawings and embodiments, the present invention is described in further detail:

Fig. 1 is the schematic diagram that Inverter Dead-time effect produces;

Fig. 2 is the flow chart of interpolating method of the present invention;

Fig. 3 is external characteristic curve comparison diagram before and after the compensation of Inverter Dead-time;

Fig. 4 is the phase current waveform figure of not compensated voltage interpolation;

The phase current waveform figure that Fig. 5 is is 3.464us through bucking voltage interpolation and make-up time;

The phase current waveform figure that Fig. 6 is is 6.5us through bucking voltage interpolation and make-up time.

Embodiment

In electric machine control system of the present invention, the bucking voltage algorithm of Inverter Dead-time comprises the steps:

Step 1, at taking into account inverter dead band delay time T _d, inverter power pipe service time T _on, turn-off time T _off, power tube conduction voltage drop and diode current flow pressure drop influence condition under, take inverter U mutually as example, within a PWM cycle, according to desirable and actual weber area equate to calculate Inverter Dead-time effect errors time T _errfor:

T _err＝(T _d+T _on-T _off+T _ave)*sgn(i _U) (1)

Wherein $T_{\mathrm{ave}}=\left\{\begin{array}{c}\frac{T_{\mathrm{on}}{U}_d+T_{\mathrm{off}}{U}_T}{T_S},i_U>0\\ \frac{T_{\mathrm{off}}{U}_d+T_{\mathrm{on}}{U}_T}{T_S},i_U<0\end{array}\right\}---\left(2\right)$

In formula (1) and formula (2), T _sbe sampling time, a U in the PWM cycle _dfor diode current flow pressure drop, U _tfor power tube conduction voltage drop, i _ufor inverter U phase current, T _avebe power tube and the caused equivalent error time of diode current flow pressure drop in the PWM cycle, sgn (i _u) be i _usign function, work as i _uwhen > 0, the value of function sgn is 1, works as i _uwhen < 0, the value of function sgn is-1, works as i _uwithin=0 o'clock, function sgn value is 0;

Step 2, calculating T _avethe U phase output terminal voltage error U that the equivalent error time causes within a PWM cycle _{ao_err},

$U_{\mathrm{ao}\_\mathrm{err}}=-\frac{T_{\mathrm{err}}}{T_S}{U}_{\mathrm{dc}}\&CenterDot;\mathrm{sgn}\left(i_U\right)---\left(3\right)$

From formula (3) and formula (2), U phase output terminal voltage error U _{ao_err}be subject to sampling time T _sand DC bus-bar voltage U _dcimpact;

Step 3, according to the calculating of inverter U phase output terminal voltage error in step 1 and step 2, push away to such an extent that the phase voltage error of inverter three-phase is:

$U_{\mathrm{an}\_\mathrm{err}}=-\frac{T_{\mathrm{err}}}{T_s}{U}_{\mathrm{dc}}\left[\frac{2\mathrm{sgn}\left(i_U\right)-\mathrm{sgn}\left(i_V\right)-\mathrm{sgn}\left(i_W\right)}{3}\right]---\left(4\right)$

$U_{\mathrm{bn}\_\mathrm{err}}=-\frac{T_{\mathrm{err}}}{T_s}{U}_{\mathrm{dc}}\left[\frac{2\mathrm{sgn}\left(i_V\right)-\mathrm{sgn}\left(i_U\right)-\mathrm{sgn}\left(i_W\right)}{3}\right]---\left(5\right)$

$U_{\mathrm{cn}\_\mathrm{err}}=-\frac{T_{\mathrm{err}}}{T_s}{U}_{\mathrm{dc}}\left[\frac{2\mathrm{sgn}\left(i_W\right)-\mathrm{sgn}\left(i_U\right)-\mathrm{sgn}\left(i_V\right)}{3}\right]---\left(6\right)$

In formula (4), formula (5), formula (6), U _{an_err}for U phase output terminal error voltage, U _{bn_err}for V phase output terminal error voltage, U _{cn_err}for W phase output terminal error voltage, i _ufor inverter U phase current, i _vfor inverter V phase current, i _wfor inverter W phase current, U _dcfor DC bus-bar voltage;

Step 4, according to the each phase output terminal error voltage of inverter of formula (4), formula (5) and formula (6), the bucking voltage that can obtain Inverter Dead-time is respectively:

U _{un_comp}＝-U _{an_err} (7)

U _{vn_comp}＝-U _{bn_err} (8)

U _{wn_comp}＝-U _{cn_err} (9)

Wherein: U _{un_comp}for the bucking voltage of inverter U phase, U _{vn_comp}for the bucking voltage of inverter V phase, U _{wn_comp}for the bucking voltage of inverter W phase.

As shown in Figure 2, in electric machine control system, the bucking voltage interpolating method of Inverter Dead-time comprises the steps:

Step 1, from bucking voltage algorithm, bucking voltage is relevant with inverter three-phase current polarity, by the current sensor inverter three-phase current i obtaining respectively that samples _u, i _vand i _w, and to inverter three-phase current i _u, i _vand i _wcarry out clark and park conversion and obtain direct current i _d, i _q;

Step 2, because the current sensor three-phase current obtaining of sampling exists burr and high-frequency harmonic, easily cause erroneous judgement, thereby need carry out filtering processing, directly phase current is done can cause time delay after single order low-pass filtering, make the phase voltage after compensation produce distortion, therefore can not directly carry out voltage compensation according to phase current, therefore to direct current i _d, i _qcarry out single order low-pass filtering treatment, obtain three-phase current i after filtering _u0, i _v0, i _w0, by three-phase current i after filtering _u0, i _v0, i _w0carry out contrary park and obtain three-phase current i against clark conversion _u, i _v, i _w, the three-phase current i now obtaining _u, i _v, i _wit is the current signal after after filtering;

Step 3, i obtained above _u, i _v, i _wcan not directly be used for carrying out the polarity judgement of phase current, affected by current sensor direct current offset, zero current clamp phenomenon, PWM noise and A/D conversion accuracy etc., phase current has certain fluctuation near zero-crossing point, its polarity is difficult to correct judgement, the judged result of mistake can cause compensation effect to decline, so in actual applications, set three-phase current i _u, i _v, i _wthe threshold value of zero crossing is i _threshold, the judging area of detecting to expand phase current zero crossing polarity,

When | i _u| > i _thresholdtime, inverter interpolation U phase bucking voltage,

When | i _v| > i _thresholdtime, inverter interpolation V phase bucking voltage,

When | i _w| > i _thresholdtime, inverter interpolation W phase bucking voltage;

Step 4, inverter U/V/W phase bucking voltage obtain U through clark conversion _{an_comp}and U _{bn_comp}, and regulate and control the V obtaining with PID respectively _d, V _qthrough the V of contrary park conversion output _a, V _bbe added, the voltage that is added gained can be obtained to U phase phase voltage U through contrary clark conversion _u, V phase phase voltage U _v, W phase phase voltage U _w, U _uu _vu _wthe input voltage that three-phase phase voltage is controlled as inverter SVPWM.

While the present invention is directed in electric machine control system motor low cruise, especially in the time of underloading, Inverter Dead-time effect causes electric machine phase current and phase voltage to distort and produces zero current clamping phenomenon, increase the current harmonic content of inverter output, this current harmonic content has increased magnetic linkage distortion and the torque pulsation of motor, has therefore proposed a kind of bucking voltage algorithm and interpolating method of Inverter Dead-time.

The torque pulsation of motor can, by the formula of this algorithm steps three (4), formula (5) and formula (6) are done respectively to the processing of Fourier's functional transformation, obtain respectively:

$U_{\mathrm{an}\_\mathrm{err}}\left(\mathrm{wt}\right)=\frac{-4\frac{T_{\mathrm{err}}}{T_S}{U}_{\mathrm{dc}}}{\mathrm{\&pi;}}\sin \left(\mathrm{wt}\right)+\underset{n=6k\&PlusMinus;1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{-4\frac{T_{\mathrm{err}}}{T_S}{U}_{\mathrm{dc}}}{\mathrm{n\&pi;}}\sin n\left(\mathrm{wt}\right)---\left(10\right)$

$U_{\mathrm{bn}\_\mathrm{err}}\left(\mathrm{wt}\right)=\frac{-4\frac{T_{\mathrm{err}}}{T_S}{U}_{\mathrm{dc}}}{\mathrm{\&pi;}}\sin (\mathrm{wt}-\frac{2\mathrm{\&pi;}}{3})+\underset{n=6k\&PlusMinus;1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{-4\frac{T_{\mathrm{err}}}{T_S}{U}_{\mathrm{dc}}}{\mathrm{n\&pi;}}\sin \left[n(\mathrm{wt}-\frac{2\mathrm{\&pi;}}{3})\right]---\left(11\right)$

$U_{\mathrm{cn}\_\mathrm{err}}\left(\mathrm{wt}\right)=\frac{-4\frac{T_{\mathrm{err}}}{T_S}{U}_{\mathrm{dc}}}{\mathrm{\&pi;}}\sin (\mathrm{wt}+\frac{2\mathrm{\&pi;}}{3})+\underset{n=6k\&PlusMinus;1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{-4\frac{T_{\mathrm{err}}}{T_S}{U}_{\mathrm{dc}}}{\mathrm{n\&pi;}}\sin \left[n(\mathrm{wt}+\frac{2\mathrm{\&pi;}}{3})\right]---\left(12\right)$

In formula (10), formula (11), formula (12), k get positive integer as 1,2,3,4...... is for calculating harmonic number, wt is current rotor angle, n is harmonic number, as n=5, represent 5 subharmonic values of current first-harmonic value.

The content of the subharmonic such as phase voltage error amount first-harmonic 5,7,11,13 will be increased by formula (10), formula (11) and the known Inverter Dead-time of formula (12) latter half effect, by electric circuit knowledge i=u/z, (i is the electric current of impedance of flowing through in loop, u is the voltage at middle impedance two ends, loop, z is the impedance in loop) known inverter phase current error is the ratio of phase voltage error and phase of impedance, also will increase the content of the subharmonic such as phase current error value first-harmonic 5,7,11,13 thereby can release Inverter Dead-time effect.By formula T=3/2n _p[ψ i _q+ (l _d-l _q) i _di _q] (T is motor output torque, n _pfor motor number of pole-pairs, ψ is rotor magnetic linkage, l _dl _qfor rotor d axle and q axle inductance value, i _di _qfor the current value of flow through motor d axle and q axle) known, the harmonic content that phase current increases will be aggravated the torque pulsation of drive motors after inverter is defeated by motor.

Obtain the bucking voltage of Inverter Dead-time by this algorithm, and select carry out interpolation suitable opportunity, thereby improved voltage utilization, as shown in Figure 3, visible by the motor external characteristic curve before and after interpolation, improve the maximum speed that system can reach, as being increased to speed n2 from speed n1; As shown in Figure 4, there is zero current clamping in the phase current waveform of not compensated voltage interpolation, and the sine of waveform is poor; As shown in Figure 5 and Figure 6, disappear through the phase current waveform zero current clamping of bucking voltage interpolation, and waveform more levels off to sine wave, and dynamic response while having improved motor low speed, reduce the harmonic content of system, thereby reduced the torque pulsation of motor.Through reality test, when electric machine control system line voltage U dc=336v, Inverter Dead-time time are while being 7.5us, under the identical operating mode of motor, before and after bucking voltage interpolation, obtain following table in addition:

As seen from the table, under the identical operating mode of motor before and after the bucking voltage interpolation, its electronic vdq value has reduced about 5v, and the busbar voltage utilance of hence one can see that electric machine control system is improved.

Claims (2)

1. a bucking voltage algorithm for Inverter Dead-time in electric machine control system, is characterized in that this algorithm comprises the steps:

Step 1, at taking into account inverter dead band delay time T _d, inverter power pipe service time T _on, turn-off time T _off, power tube conduction voltage drop and diode current flow pressure drop influence condition under, take inverter U mutually as example, within a PWM cycle, according to desirable and actual weber area equate to calculate Inverter Dead-time effect errors time T _errfor:

T _err＝(T _d+T _on-T _off+T _ave)*sgn(i _U) (1)

Wherein $T_{\mathrm{ave}}=\left\{\begin{array}{c}\frac{T_{\mathrm{on}}{U}_d+T_{\mathrm{off}}{U}_T}{T_S},i_U>0\\ \frac{T_{\mathrm{off}}{U}_d+T_{\mathrm{on}}{U}_T}{T_S},i_U<0\end{array}\right\}---\left(2\right)$

In formula (1) and formula (2), T _sbe sampling time, a U in the PWM cycle _dfor diode current flow pressure drop, U _tfor power tube conduction voltage drop, i _ufor inverter U phase current, T _aveit is power tube and the caused equivalent error time of diode current flow pressure drop in the PWM cycle;

Step 2, calculating T _avethe U phase output terminal voltage error U that the equivalent error time causes within a PWM cycle _{ao_err},

$U_{\mathrm{ao}\_\mathrm{err}}=-\frac{T_{\mathrm{err}}}{T_S}{U}_{\mathrm{dc}}\&CenterDot;\mathrm{sgn}\left(i_U\right)---\left(3\right)$

From formula (3) and formula (2), U phase output terminal voltage error U _{ao_err}be subject to sampling time T _sand DC bus-bar voltage U _dcimpact;

Step 3, according to the calculating of inverter U phase output terminal voltage error in step 1 and step 2, push away to such an extent that the phase voltage error of inverter three-phase is:

$U_{\mathrm{an}\_\mathrm{err}}=-\frac{T_{\mathrm{err}}}{T_s}{U}_{\mathrm{dc}}\left[\frac{2\mathrm{sgn}\left(i_U\right)-\mathrm{sgn}\left(i_V\right)-\mathrm{sgn}\left(i_W\right)}{3}\right]---\left(4\right)$

$U_{\mathrm{bn}\_\mathrm{err}}=-\frac{T_{\mathrm{err}}}{T_s}{U}_{\mathrm{dc}}\left[\frac{2\mathrm{sgn}\left(i_V\right)-\mathrm{sgn}\left(i_U\right)-\mathrm{sgn}\left(i_W\right)}{3}\right]---\left(5\right)$

$U_{\mathrm{cn}\_\mathrm{err}}=-\frac{T_{\mathrm{err}}}{T_s}{U}_{\mathrm{dc}}\left[\frac{2\mathrm{sgn}\left(i_W\right)-\mathrm{sgn}\left(i_U\right)-\mathrm{sgn}\left(i_V\right)}{3}\right]---\left(6\right)$

In formula (4), formula (5), formula (6), U _{an_err}for U phase output terminal error voltage, U _{bn_err}for V phase output terminal error voltage, U _{cn_err}for W phase output terminal error voltage, i _ufor inverter U phase current, i _vfor inverter V phase current, i _wfor inverter W phase current, U _dcfor DC bus-bar voltage;

Step 4, according to the each phase output terminal error voltage of inverter of formula (4), formula (5) and formula (6), the bucking voltage that can obtain Inverter Dead-time is respectively:

U _{un_comp}＝-U _{an_err} (7)

U _{vn_comp}＝-U _{bn_err} (8)

U _{wn_comp}＝-U _{cn_err} (9)

Wherein: U _{un_comp}for the bucking voltage of inverter U phase, U _{vn_comp}for the bucking voltage of inverter V phase, U _{wn_comp}for the bucking voltage of inverter W phase.

2. a bucking voltage interpolating method for Inverter Dead-time in electric machine control system, is characterized in that this method comprises the steps:

Step 1, from bucking voltage algorithm, bucking voltage is relevant with inverter three-phase current polarity, by the current sensor inverter three-phase current i obtaining respectively that samples _u, i _vand i _w, and to inverter three-phase current i _u, i _vand i _wcarry out clark and park conversion and obtain direct current i _d, i _q;

Step 2, to direct current i _d, i _qcarry out single order low-pass filtering treatment, obtain three-phase current i after filtering _u0, I _v0, i _w0, by three-phase current i after filtering _u0, i _v0, i _w0carry out contrary park and obtain three-phase current i against clark conversion _u, i _v, i _w, the three-phase current i now obtaining _u, i _v, i _wit is the current signal after after filtering;

Step 3, setting three-phase current i _u, i _v, i _wthe threshold value of zero crossing is i _threshold,

When | i _u| > i _thresholdtime, inverter interpolation U phase bucking voltage,

When | i _v| > i _thresholdtime, inverter interpolation V phase bucking voltage,

When | i _w| > i _thresholdtime, inverter interpolation W phase bucking voltage;

Step 4, inverter U/V/W phase bucking voltage obtain U through clark conversion _{an_comp}and U _{bn_comp}, and regulate and control the V obtaining with PID respectively _d, V _qthrough the V of contrary park conversion output _a, V _bbe added, the voltage that is added gained can be obtained to U phase phase voltage U through contrary clark conversion _u, V phase phase voltage U _v, W phase phase voltage U _w, U _uu _vu _wthe input voltage that three-phase phase voltage is controlled as inverter SVPWM.

Images