CN104253550B - Dead-time compensation method for NPC-based three-level SVPMW (space vector pulse width modulation) rectifier - Google Patents

Abstract

The invention discloses a dead zone compensation method based on NPC three-level SVPWM rectifier. The method firstly calculates the general expression of the reconstructed voltage impulse without and with tube voltage drop without and with dead zones, and obtains Reconstruct the general expression of the voltage impulse compensation amount; then, according to the current direction of each phase and the voltage sequence state, select the general expression of the reconstructed voltage impulse compensation amount corresponding to the three-phase voltage, and calculate the voltage compensation amount; finally, Feedback the calculated voltage compensation amount to the reference voltage vector before reconstruction for compensation. The present invention adopts a new compensation amount selection method, calculates the compensation amount during the voltage reconstruction process, and compensates and participates in the control of the reference voltage; the present invention fully considers the dead time and tube voltage drop, and solves the problem based on NPC The problem of voltage and current distortion caused by dead-time effects in three-level rectifiers improves system performance.

Description

A dead zone compensation method based on NPC three-level SVPWM rectifier

technical field

The invention relates to a dead zone compensation method of a frequency converter, in particular to a dead zone compensation method based on an NPC three-level SVPWM rectifier, and belongs to the field of power electronics and power transmission.

Background technique

In actual rectifier and inverter control, in order to avoid a type of shoot-through short circuit, dead time must be added to prevent power device shoot-through. For the moment of dead zone action, since the potential of each phase on the AC side will fluctuate according to the current direction, it will affect the output voltage and reduce the control accuracy of the rectifier and inverter. Therefore, it is necessary to compensate for the dead zone effect.

For dead zone compensation, there are two main current methods: one is hardware compensation, by adding a hardware circuit to compare the actual output voltage with the voltage reference value, directly dynamically adjust the SVPWM output modulation wave, that is, directly change Ta, Tb, Tc The action time is used to compensate the dead zone, but this method requires hardware to detect the positive and negative of the current online, and the operating cost is relatively high. The second is software compensation. By controlling the dead zone compensation algorithm, there is no need to increase hardware, and the flexibility is strong. However, the selection of compensation amount in the existing software compensation method ignores the conduction voltage drop of power devices such as switch tubes and diodes. The error effect brought by it will lead to large voltage and current distortion and low compensation accuracy.

Contents of the invention

Aiming at the problems existing in the prior art, the present invention provides a dead-zone compensation method based on NPC three-level SVPWM rectifier. While compensating the dead-zone effect, the method takes into account the conduction voltage of power devices such as switching tubes and diodes. The error effect caused by the drop. In order to achieve the above object, the technical solution of the present invention is: a kind of dead zone compensation method based on NPC three-level SVPWM rectifier, its steps are:

(1) Regardless of the voltage drop of the switching tube, freewheeling diode and embedded pull diode, the voltage is reconstructed, and the general expression of the reconstructed voltage impulse without dead zone is calculated under ideal conditions;

(2) Consider the voltage drop of the switching tube, freewheeling diode and embedded pull diode, reconstruct the voltage, and calculate the general expression of the reconstructed voltage impulse with dead zone under actual conditions;

(3) The general expression for calculating the compensation amount of reconstructed voltage impulse;

(4) Carry out coordinate transformation on the three-phase current based on the NPC three-level SVPWM rectifier, and judge the direction of each phase current according to the sector where the synthesized vector is located;

(5) Judging the voltage sequence state of the three-phase bridge arm according to the sector where the reference voltage vector is located;

(6) According to the current direction and voltage sequence state of each phase, select the general expression of the reconstructed voltage impulse compensation amount corresponding to the three phases a, b, and c, and calculate the voltage compensation amount;

(7) Feedback the calculated voltage compensation amount to the reference voltage vector before reconstruction for compensation.

The method for reconstructing the voltage in the steps (1) and (2) is to simplify the three-level voltage reconstruction to two-level sectors for processing, and locate the voltage vectors to be reconstructed in small The hexagon is processed, and then the components of the center of the small hexagon on the A, B, and C axes are used as the compensation amount. The output reconstruction phase voltage of the three-level converter is:

in are the corresponding compensation voltages of the three phases.

The general expression of the reconstructed voltage impulse without dead zone in the step (1) under ideal conditions is:

in, is the switch conduction duty cycle, is the switching period.

The general expression of the reconstructed voltage impulse with dead zone in the step (2) is:

in, is the dead time, is the IGBT voltage drop, is the diode voltage drop, switching cycle, is the duty cycle of the switch.

The general expression of the reconstructed voltage impulse compensation amount in the step (3) is:

in, is the dead time, is the IGBT voltage drop, is the diode voltage drop, switching cycle, for switch conduction

duty cycle.

The coordinate transformation of the three-phase current in the step (4) is a clack transformation, that is, a 3/2 stationary coordinate system transformation.

The selection of the general expression of the reconstructed voltage impulse compensation amount in the step (6) is judged according to the initial small vector.

The voltage compensation amount in step (7) is Amount of voltage compensation in the coordinate system.

Compared with the prior art, the present invention has the following beneficial effects:

(1) Compensation is performed on the basis of the existing control algorithm, no need to increase hardware, low operating cost, and strong flexibility;

(2) The three-level voltage reconstruction can also be simplified to two-level sectors for processing, and the voltage vectors to be reconstructed are respectively positioned in small hexagons for processing, and then the center of the small hexagons is placed in the The components on the A, B, and C axes are used as the compensation amount. This reconstruction method works well and has good real-time performance;

(3) A new type of compensation amount selection method is adopted, the compensation amount is calculated during the voltage reconstruction process, and the reference voltage is compensated and participated in the control. This method is simple to calculate and has a good compensation effect;

(4) While compensating for the dead zone effect, it also takes into account the error effect caused by the conduction voltage drop of the IGBT and the diode, which reduces the voltage and current distortion problems and improves the system performance.

Description of drawings

Fig. 1 is a flowchart of the dead zone compensation method based on the NPC three-level SVPWM rectifier of the present invention.

Fig. 2 is the main circuit topology of the present invention based on the NPC three-level SVPWM rectifier dead zone compensation method.

Fig. 3 is the area division of the optimized three-level method based on the NPC three-level SVPWM rectifier dead zone compensation method in the present invention.

Fig. 4 is the simulation result of the voltage vector reconstruction method of the present invention.

Fig. 5 is a diagram of the voltage vector feedback system based on the NPC three-level SVPWM rectifier dead zone compensation method in the present invention.

Fig. 6 is a circuit diagram of a-phase bridge arm based on the NPC three-level SVPWM rectifier dead zone compensation method of the present invention.

Fig. 7 is a waveform diagram of the phase voltage of the AC side of the dead zone effect relative to the midpoint when the voltage sequence state of the present invention is 0——1—0.

Fig. 8 is a waveform diagram of the phase voltage on the AC side of the dead zone effect relative to the midpoint when the voltage sequence state of the present invention is 0-1-0.

Fig. 9 is a diagram of current direction determination based on current synthesis vector in the present invention.

Fig. 10 is a compensation voltage vector judgment diagram of the present invention.

Fig. 11 is _a harmonic analysis diagram of i a at 0.5s without dead zone compensation in the present invention.

Fig. 12 is _a harmonic analysis diagram of i a after 0.5s when dead zone compensation is performed in the present invention.

detailed description

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings. However, the content disclosed below is the principle of the present invention, and is not limited to this example.

Fig. 1 is a flow chart of the dead zone compensation method based on the NPC three-level SVPWM rectifier of the present invention.

Figure 2 is the main circuit topology diagram for the NPC-based three-level SVPWM rectifier. The neutral-point clamped three-phase three-level rectifier includes A, B, and C three-phase bridge arms, and each phase bridge arm consists of four switching tubes, Composed of 4 freewheeling diodes and two clamping diodes, O in the figure represents the midpoint; a, b, c represent the AC side input of the three-phase bridge arm; Sa1, Sa2, Sa3, Sa4 represent the 4 switch tubes of the A phase , Da1 and Da2 represent 2 clamping diodes of A phase.

The three-level PWM calculation simplifies the three-level to two-level through coordinate translation to perform sector judgment and time calculation. Similarly, the three-level voltage reconstruction can also be simplified to two-level sectors for processing, and the voltage vectors to be reconstructed are respectively positioned in small hexagons for processing, and then the center of the small hexagons is placed in the The components on the A, B, and C axes can be used as the compensation amount. The sector corresponding to S is shown in Figure 3, and the three-phase output voltage reconstruction compensation voltage under different S values is shown in the following table:

Therefore, it can be simply obtained that the output reconstruction phase voltage of the three-level converter is:

in are the corresponding compensation voltages of the three phases.

When both the upper and lower DC buses are 75V, the output side of the inverter is connected to a star-shaped resistor load of 10 ohms. The given modulation degree of the open loop voltage is 0.65. Figure 4 shows the output actual phase voltage, the output actual phase voltage through the filter, the reconstructed phase voltage through the filter waveform, and the estimated error. It can be seen from the figure that the error is within 3%, indicating that this reconstruction method works well and has good real-time performance.

Using the voltage compensation strategy, the dead zone effect compensation amount is introduced into the feedforward voltage given command as the variation of the reconstructed voltage, and its system function is shown in Figure 5.

Taking phase a as an example to analyze the principle of the dead zone compensation control method, the topology of the phase a bridge arm of the three-phase three-level SVPWM rectifier is shown in Figure 6. In this paper, seven-segment and low-level active modulation are used, and the vector synthesis is small vector -> main vector -> sub vector -> small vector -> sub vector -> main vector -> small vector. Therefore, the voltage state timing of the three bridge arms of a, b, and c can only be relatively high-relatively low-relatively high (1-0-1 or 0--1-0), so in all vector regions a There are only two kinds of time series of the voltage state of , b, c relative to point O: "0--1-0" and "1-0-1". It is agreed that flag=1 when the current flows out of the bridge arm, and flag=-1 when the current flows into the bridge arm.

Figure 7 shows the dead zone effect when the voltage state sequence is "0--1-0", and Figure 8 shows the dead zone effect when the voltage state sequence is "1-0-1". Among them, broken line 2 is an ideal graph without dead zone, and broken line 1 is a graph with dead zone, a1, a2, a3, and a4 represent the control pulses of phase a switching devices Sa1, Sa2, Sa3, and Sa4 respectively, and DT is the dead zone time , vs is the IGBT voltage drop, vd is the diode voltage drop, Ts switching period, D is the switch conduction duty cycle (if a1 conduction duty cycle is 0, then D is a2 conduction duty cycle, if a1 is not 0, then D is a1 conduction duty cycle). Vx* is the impulse without dead zone (x=1, 2, 3, 4) in the ideal situation, Vx is the impulse with dead zone in the actual situation (x=1, 2, 3, 4), and ΔVx is dead The voltage impulse required for zone effect compensation (x=1, 2, 3, 4).

When the voltage state sequence is "0—-1—0":

Impulse when flag=1

(regardless of tube pressure drop and dead zone)

(considering tube pressure drop and dead zone)

Impulse when flag=-1

(regardless of tube pressure drop and dead zone)

(considering tube pressure drop and dead zone)

. When the voltage state sequence is "1-0-1":

Impulse when flag=1

(regardless of tube pressure drop and dead zone)

(considering tube pressure drop and dead zone)

Impulse when flag=-1

(regardless of tube pressure drop and dead zone)

(considering tube pressure drop and dead zone)

.

Assuming that the three-phase currents are ia, ib, and ic, the three-phase currents are transformed by the 3/2 static coordinate system to obtain the current vectors i_alfa and i_beta. The vectors rotate counterclockwise, and the angle between the current vector and the A axis is j. First, the sector where the current vector is located can be calculated according to the angle j, and then the current direction of each phase can be determined according to the sector, and the corresponding situation is shown in Figure 9.

For the judgment of the voltage timing state and the selection of the voltage impulse compensation amount, this paper adopts seven-segment and low-level active modulation, and the vector synthesis is small vector->main vector->sub-vector->small vector->sub-vector- > main vector -> small vector. Therefore, the voltage state timing of the three bridge arms a, b, and c can only be relatively high-relatively low-relatively high (1-0-1 or 0--1-0). The switch state can be judged by the starting vector. And because the example of the present invention simplifies the three-level voltage reconstruction into two-level voltage reconstruction, the sector represented by s takes the small vector in the sector as the starting vector, as shown in FIG. 3 . For example, the sequence of vectors in the sector of s=1 is: "100-10-1-1-1-1-0-1-1-1-1-1-10-1-100" starting with "100", a Phase starts with "1", then the voltage state sequence of phase a is "1-0-1". Phase b starts with "0", and the voltage state sequence of phase b is "0—-1—0". Phase c starts with "0", and the voltage state sequence of phase c is "0—-1—0".

Select when the voltage state sequence is "0—-1—0" and flag=1:

Select when the voltage state sequence is "0—-1—0" and flag=1:

Select when the voltage state sequence is "0—-1—0" and flag=-1:

Select when the voltage state sequence is "1-0-1" and flag=1:

Select when the voltage state sequence is "1—0—1" and flag=-1:

The selection of voltage impulse compensation for each sector is shown in Figure 10.

According to the current direction judgment diagram and the selection diagram of the voltage impulse compensation amount, the final compensation voltage impulse compensation amount can be determined .

For the above voltage impulse compensation , the voltage compensation factor can be obtained .

can also be found .

right Perform clack transformation to get the feedback value shown in Figure 5 .

in Transformation matrix for clack.

Simulation parameters: DC side voltage , DC side capacitance , the switching frequency is 10k, and the dead time DT is 8µs. Voltage loop PI's , , the two current loops PI , .

The a-phase current before compensation is shown in Figure 11, and the a-phase current after compensation is shown in Figure 12. Taking a cycle at 0.5s for comparison, it can be seen that THD=3.72% before compensation and THD=1.99% after compensation, achieving a better compensation effect.

The voltage error caused by the dead zone effect of the three-level rectifier is related to the dead zone time DT and the switching period Ts, and the square of the current determines the positive or negative of the error. This paper simulated the voltage compensation method separately, and achieved good compensation results, which proved the correctness and effectiveness of the method.

Finally, it should also be noted that the above embodiments are only used to illustrate the present invention, not to limit the present invention. The contents not described in detail in the description of the present invention belong to the prior art known to those skilled in the art.

Claims (7)

1. A method based on NPC three-level SVPWM rectifier dead zone compensation, is characterized in that: the method may further comprise the steps: (1) Regardless of the voltage drop of the switching tube, freewheeling diode and embedded pull diode, the voltage is reconstructed, and the general expression of the reconstructed voltage impulse without dead zone is calculated under ideal conditions; (2) Considering the voltage drop of the switching tube, the freewheeling diode and the embedded pull diode, the voltage is reconstructed, and the general expression of the reconstructed voltage impulse with a dead zone is calculated in the actual situation; (3) Calculate the general expression of the reconstruction voltage impulse compensation, the compensation of the reconstruction voltage impulse is equal to the reconstruction voltage impulse of step (1) minus the reconstruction voltage impulse of step (2); (4) Carry out coordinate transformation based on the a, b, c three-phase current of the NPC three-level SVPWM rectifier, and judge the direction of each phase current according to the sector where the synthetic vector is located; (5) Judging the sequential state of the three-phase bridge arm voltage of a, b, and c according to the sector where the reference voltage vector is located; (6) According to the current direction and voltage sequence state of each phase, select the general expression of the reconstructed voltage impulse compensation amount corresponding to the three phases a, b, and c, and calculate the voltage compensation amount; (7) Feedback the calculated voltage compensation amount to the reference voltage vector before reconstruction for compensation; Wherein, the method for reconstructing the voltage in the steps (1) and (2) is to simplify the three-level voltage reconstruction to two-level sectors for processing, and respectively locate the voltage vectors that need to be reconstructed Process it in the small hexagon, and then take the components of the center of the small hexagon on the A, B, and C axes as the compensation amount, and reconstruct the phase voltage as: $\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\\ {\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\\ {\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; u</span>}\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}\left[\begin{array}{ccc}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 3</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 3</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 3</span>}\\ <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 3</span>}& \mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 3</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 3</span>}\\ <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 3</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 3</span>}& \mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 3</span>}\end{array}\right]<span\; class="notranslate">\; *</span>\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\\ {\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\\ {\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\end{array}\right]<span\; class="notranslate">\; *</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}<span\; class="notranslate">\; +</span>\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; m</span>}}\\ {\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; m</span>}}\\ {\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; m</span>}}\end{array}\right]$ Where V _{a_com} , V _{b_com} , and V _{c_com} are respectively the corresponding compensation voltages of the three phases. 2. based on the NPC three-level SVPWM rectifier dead zone compensation method according to claim 1, it is characterized in that: the general expression of the reconstructed voltage impulse without dead zone in described step (1) under ideal conditions is: ${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}$ Among them, u _dc is the DC side voltage, D is the switch conduction duty cycle, and T _s is the switching period. 3. based on NPC three-level SVPWM rectifier dead zone compensation method according to claim 1, it is characterized in that: described step (2) has the general expression of the reconstructed voltage impulse of dead zone under actual conditions: ${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span><span\; class="notranslate">\; \&lsqb;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; \&rsqb;</span>$ Among them, DT is the dead time, v _s is the IGBT voltage drop, v _d is the diode voltage drop, T _s switching period, D is the switch conduction duty cycle. 4. based on NPC three-level SVPWM rectifier dead zone compensation method according to claim 1, it is characterized in that: the general expression of described step (3) reconstruction voltage impulse compensation amount is: ${\mathrm{<span\; class="notranslate">\; \&Delta;V</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; T</span>}$ Among them, DT is the dead time, v _s is the IGBT voltage drop, v _d is the diode voltage drop, T _s switching period, D is the switch conduction duty cycle. 5. The dead zone compensation method based on NPC three-level SVPWM rectifier according to claim 1, characterized in that: the coordinate transformation of the step (4) three-phase current is clack transformation, that is, 3/2 static coordinate system transformation. 6. based on NPC three-level SVPWM rectifier dead zone compensation method according to claim 1, it is characterized in that: the selection of the general expression of described step (6) reconstruction voltage impulse compensation amount is based on initial small vector judge. 7. The dead-zone compensation method based on NPC three-level SVPWM rectifier according to claim 1, characterized in that: the voltage compensation amount in the step (7) is the voltage compensation amount in the α, β coordinate system.