CN104320012A - Five-level simplified algorithm based on three levels - Google Patents

Abstract

The invention mainly discloses a five-level simplified algorithm based on three levels. According to the five-level simplified algorithm, five-level space vectors are simplified based on the three levels. The five-level simplified algorithm mainly includes the following steps that (1), a five-level space vector diagram is regarded as being composed of six three-level vector diagrams; (2), reference vectors are modified; (3), three-level sector vectors are determined; (4), three-level sectors are divided; (5), a time calculation method is used; (6), time state assignment is carried out. The five-level space vectors can be simplified through the six steps. The algorithm is intuitive and effective, and the simplified five-level algorithm can effectively keep details of the original five-level space vectors; as the modification of the five-level space vectors is not involved in the algorithm, the algorithm is concise and high in stability and can be effectively applied to the algorithm field of the five-level space vectors.

Description

A kind of five level shortcut calculations based on three level

Technical field

The present invention have studied topological structure and the operation principle thereof of diode clamp formula five-electrical level inverter, essentially discloses a kind of five level shortcut calculations based on three level.

Background technology

The present invention is carrying out simplify processes based on the basis of three level to five level space vectors.

Summary of the invention

The present invention have studied topological structure and the operation principle thereof of diode clamp formula five-electrical level inverter, essentially discloses a kind of five level shortcut calculations based on three level; The present invention is carrying out simplify processes based on the basis of three level to five level space vectors; It mainly comprises the steps: 1) five level space vector figure are regarded as be made up of 6 three level polar plots, 2) correction, 3 of reference vector) determination, 4 of three level sector vector) three level se ctor partition, 5) Time Calculation, 6) time state distributes.

Further, the topological structure of five-electrical level inverter: as shown in Figure 1, in figure, C1, C2, C3 and C4 are dc-link capacitance to the single armed topological structure of diode clamp type Five-level converter, and capacitance voltage value is 1/4th DC bus-bar voltage.8 switching power devices (S1 ~ S8) series connection of every phase brachium pontis, S1 and S5, S2 and S6, S3 and S7 during normal work, and the complementary conducting of S4 and S8, and often kind of level has the conducting simultaneously of 4 device for power switching.VD1, VD2, VD3, VD4, VD5 and VD6 are clamp diode.

Further, the operation principle of five-electrical level inverter: the every phase brachium pontis of five-electrical level inverter has 5 operating states, has 5 altogether ³=125 operating states, if with 0,1,2,3, the 4 output level 1/2V representing every phase brachium pontis respectively _dc, 1/4V _dc, 0 ,-1/4V _dc,-1/2V _dc, then according to space-vector definitions, the output voltage three dimensional vector diagram of five-electrical level inverter can be obtained, as shown in Fig. 2 left side.125 space voltage vector 61 positions in figure, wherein 1 zero vector position corresponds to 5 redundant vectors, and all the other 60 non-zero positions correspond to 120 redundant vectors.The voltage magnitude that in figure, each vector position is corresponding is respectively: 2/3V _dc, $\sqrt{13}/{6V}_{\mathrm{dc}},1/\sqrt{3}{V}_{\mathrm{dc}},1/2V_{\mathrm{dc}},\sqrt{7}/{6V}_{\mathrm{dc}},$ $1/3V_{\mathrm{dc}},1/\sqrt{3}{V}_{\mathrm{dc}},1/6V_{\mathrm{dc}},0.$ And as can be seen from Figure, along with the increase of voltage vector magnitude, redundancy voltage vector quantities corresponding is with it fewer.On outermost regular hexagon, the redundancy voltage vector of each voltage vector position only has one.

Further, based on as follows to the detailed step of five level space vectors simplification on the basis of three level:

Step 1) five level space vector figure are regarded as be made up of, as Fig. 26 three level polar plots.Its basic skills establishes space vector V _refbe θ with the angle of α axle, three level polar plot be numbered N, then define:

According to V _α, V _βand the relational expression between θ this relational expression is substituted in definition, specifically judge the numerical value of N.

Step 2) correction of reference vector is to V according to N value _refcarry out mid point translation, make the starting point of reference voltage vector move to the mid point of each little three level polar plot.Concrete translation is as table 1.After translation, U _dc1=U _dc/ 2.

Reference voltage vector correction during table 1 different N value

Step 3) determine the vector of three level sector after five level vector median filters to three level vector, three level polar plot to be divided into 6 large sectors, as shown in Figure 3; If revised space vector V ' _refbe θ with the angle of α axle ₁, three level polar plot sector be numbered N ₁, then define:

According to V _α, V _βand the relational expression between θ this relational expression is substituted in definition, specifically judges N ₁numerical value.

Step 4) three level se ctor partition is that each sector is divided into 6 zonules, as Fig. 4, for N by the segmentation of sector, 6 in three level ₁=1 segments, and region is denoted as N ₂.Work as θ ₁≤ 30 °, V ' _refin the middle of zonule 1 or 3 or 5.Successively concrete discriminatory analysis is carried out to this below:

1.. the judgement of zonule 1: consider V ' _refprojection on 30 degree of directions, as shown in Figure 5.At θ ₁≤ 30 ° lower time, if meet will by restriction relation formula: V ' _β=V ' _refsin θ ₁, V ' _α=V ' _refcos θ ₁, carried out that abbreviation obtains during this relational expression, N can be judged ₂=1.

2.. the judgement of zonule 5: as Fig. 6, consider V ' _refwith the size of 0A length, A point position V ' _refin the marginal intersection point in region 3 and region 5.At θ ₁≤ 30 ° lower time, if meet will

$\left|\stackrel{\→}{O}A\right|\≤V_{\mathrm{ref}}^{\′}$

By restriction relation formula: V ' _β=V ' _refsin θ ₁, V ' _α=V ' _refcos θ ₁, carried out that abbreviation obtains

$\sqrt{3}{V}_{\mathrm{\α}}^{\′}-V_{\mathrm{\β}}^{\′}\≥\frac{1}{\sqrt{3}}{U}_{\mathrm{dc}1}$

During this relational expression, N can be judged ₂=1.

3.. the judgement in region 3: under 30 degree, the first sector, the judgement in region 3 directly uses exclusive method, neither meets $\sqrt{3}{V}_{\mathrm{\α}}^{\′}+V_{\mathrm{\β}}^{\′}\≤\frac{1}{\sqrt{3}}{U}_{\mathrm{dc}1}$ Also do not meet $\sqrt{3}{V}_{\mathrm{\α}}^{\′}-V_{\mathrm{\β}}^{\′}\≥\frac{1}{\sqrt{3}}{U}_{\mathrm{dc}1}$ Time, then between judging that reference voltage is in area 3.

4. as 30 °≤θ ₁≤ 60 °, V ' _refin the middle of zonule 2 or 4 or 6; Concrete determination methods and θ ₁≤ 30 ° is similar, wherein region 4, determines by first determining that region 2 and 6 carries out getting rid of.

5. N is worked as ₁=2,3,4,5, when 6, judge method and the N of zonule ₁=1 is similar.

Step 5) Time Calculation method is behind the region judging reference voltage vector place, according to the rule of NTV, can find three basic vector V of synthesized reference voltage vector ₁, V ₂, V ₃, together with reference voltage vector V ' _ref, substitute into voltage-second balance equation group:

$\left\{\begin{array}{c}{T}_1{V}_1+T_2{V}_2+T_3{V}_3=T_s{V}_{\mathrm{ref}}^{\′}\\ T_1+T_2+T_3=T_s\end{array}\right.$

Solve T ₁, T ₂, T ₃namely traditional three level SVPWM algorithm is completed to the calculating of fundamental space vector action time.According to relational expression in like manner can obtain reference voltage vector when other regions, the action time of basic vector.Table 2 provides N ₁=1 illustrates each basic vector action time.

Table 2 N ₁=1 basic vector table action time

Step 6) time state distributes is adopt centrosymmetric seven segmentation SVPWM waveforms to be distributed to corresponding vector state the action time of basic vector, as can be seen from three level SVPWM fundamental space polar plot, vector and on off state one_to_one corresponding in large vector, the corresponding 2 groups of on off states of short vector, zero vector has 3 groups of on off states.Due in the on off state that occurs within each sampling period, on off state corresponding to short vector often, therefore selects short vector as the start vector in each sampling period.Zero vector can be chosen according to the order of action of on off state.The order of action of each group of on off state will follow such principle: the change of primary voltage vector can only have the switch motion of a brachium pontis arbitrarily, namely in binary vector represents, only has one to change or not change.Table 3 gives N ₁with n, o, p, each vector race-card when=1, wherein represents that corresponding three-phase is for low level, zero level, high level respectively.With N ₁=1, N ₂=1 is example, and the corresponding relation of basic vector action time and vector state as shown in Figure 7.

Table 3 N ₁=1 vector state race-card

N 2	Vector state race-card
		1	onn?oon?ooo?poo?ooo?oon?onn
2	oon?ooo?poo?ppo?poo?ooo?oon
		3	onn?oon?pon?poo?pon?oon?onn
4	oon?pon?poo?ppo?poo?pon?oon
		5	onn?pnn?pon?poo?pon?pnn?onn
6	oon?ooo?opo?ppo?opo?ooo?oon

[0036]beneficial effect

Algorithm of the present invention is intuitively effective, five level algorithms after simplification effectively can keep the details of original five level space vectors, and this algorithm is not owing to relating to the amendment of five level space vectors, make this algorithm succinct and have good stability, can effectively be applied in the algorithm of five level space vectors.

Accompanying drawing explanation

Fig. 1 is the single-phase topology diagram of diode clamp type Five-level converter

Fig. 2 is five level polar plots and simplifies three level polar plot

Fig. 3 is three level polar plot

Fig. 4 is N ₁when=1, the division of sector is with reference to figure

Fig. 5 is N ₂the judgement of=1 with reference to figure

Fig. 6 N ₂the judgement of=5 with reference to figure

Fig. 7 N ₁=1, N ₂the reference of=1 vector action time and vector state corresponding relation is schemed

Embodiment

Be the single armed topology diagram of diode clamp type Five-level converter as shown in Figure 1, in figure, C1, C2, C3 and C4 are dc-link capacitance, and capacitance voltage value is 1/4th DC bus-bar voltage.8 switching power devices (S1 ~ S8) series connection of every phase brachium pontis, S1 and S5, S2 and S6, S3 and S7 during normal work, and the complementary conducting of S4 and S8, and often kind of level has the conducting simultaneously of 4 device for power switching.VD1, VD2, VD3, VD4, VD5 and VD6 are clamp diode.

The every phase brachium pontis of five-electrical level inverter has 5 operating states, has altogether 53=125 operating state, if with 0, and 1,2,3, the 4 output level 1/2V representing every phase brachium pontis respectively _dc, 1/4V _dc, 0 ,-1/4V _dc,-1/2V _dc, then according to space-vector definitions, the output voltage three dimensional vector diagram of five-electrical level inverter can be obtained, as shown in Fig. 2 left side.125 space voltage vector 61 positions in figure, wherein 1 zero vector position corresponds to 5 redundant vectors, and all the other 60 non-zero positions correspond to 120 redundant vectors.The voltage magnitude that in figure, each vector position is corresponding is respectively: 2/3V _dc, and as can be seen from Figure, along with the increase of voltage vector magnitude, redundancy voltage vector quantities corresponding is with it fewer.On outermost regular hexagon, the redundancy voltage vector of each voltage vector position only has one.

Based on as follows to the detailed step of five level space vectors simplification on the basis of three level:

Step 1), as Fig. 2, five level space vector figure are regarded as and is made up of 6 three level polar plots.Its basic skills establishes space vector V _refbe θ with the angle of α axle, three level polar plot be numbered N, then define:

Judge that the concrete grammar of N is as follows, be described for N=1.According to V _α, V _βand the relation between θ: when satisfied (2) can judge N=1.

Other values of N can be determined by (1) equally.

Step 2) correction of reference vector is to V according to N value _refcarry out mid point translation, make the starting point of reference voltage vector move to the mid point of each little three level polar plot.Concrete translation is as table 1.After translation, U _dc1=U _dc/ 2.

Reference voltage vector correction during table 1 different N value

Step 3) determination of three level sector vector is by after five level vector median filters to three level vector, three level polar plot can be divided into 6 large sectors, as shown in Figure 3.If revised space vector V ' _refbe θ with the angle of α axle ₁, three level polar plot sector be numbered N ₁, then define:

Judge N ₁concrete grammar as follows, with N ₁=1 is described for example.According to V ' _α, V ' _βand θ ₁between relation when satisfied (4) can judge N ₁=1.

N ₁other values can be determined by (3) equally.

Step 4) three level se ctor partition: by the sector segmentation of 6 in three level, each sector is divided into 6 zonules, as Fig. 4, for N ₁=1 segments, and region is denoted as N ₂.

Work as θ ₁≤ 30 °, V ' _refin the middle of zonule 1 or 3 or 5.Successively concrete discriminatory analysis is carried out to this below:

1) judgement of zonule 1: consider V ' _refprojection on 30 degree of directions, as shown in Figure 5.

At θ ₁≤ 30 ° lower time, if meet relational expression:

Restriction relation formula: V ' _β=V ' _refsin θ ₁, V ' _α=V ' _refcos θ ₁, abbreviation is carried out to (5) and obtains:

$\sqrt{3}{V}_{\mathrm{\α}}^{\′}+V_{\mathrm{\β}}^{\′}\≤\frac{1}{\sqrt{3}}{U}_{\mathrm{dc}1}---\left(6\right)$

Meet (6) formula, can N be judged ₂=1

2) judgement of zonule 5: as shown in Figure 6, considers V ' _refwith the size of 0A length, A point position V ' _refin the marginal intersection point in region 3 and region 5.

At θ ₁≤ 30 ° lower time, if meet relational expression:

$\left|\stackrel{\→}{O}A\right|\≤V_{\mathrm{ref}}^{\′}---\left(7\right)$

Restriction relation formula: V ' _β=V ' _refsin θ ₁, V ' _α=V ' _refcos θ ₁, abbreviation is carried out to (7) and obtains:

$\sqrt{3}{V}_{\mathrm{\α}}^{\′}-V_{\mathrm{\β}}^{\′}\≥\frac{1}{\sqrt{3}}{U}_{\mathrm{dc}1}---\left(9\right)$

Meet (9) formula, can N be judged ₂=1.

3) judgement in region 3: under 30 degree, the first sector, the judgement in region 3 directly uses exclusive method, does not namely meet (6), time (9), between judging that reference voltage in area 3.

4) as 30 °≤θ ₁≤ 60 °, V ' _refin the middle of zonule 2 or 4 or 6.Concrete determination methods and θ ₁≤ 30 ° is similar, wherein region 4, determines by first determining that region 2 and 6 carries out getting rid of.

5) N is worked as ₁=2,3,4,5, when 6, judge method and the N of zonule ₁=1 is similar.

Step 5) Time Calculation method is behind the region judging reference voltage vector place, according to the rule of NTV (Nearest Triangle Vectors), can find three basic vector V of synthesized reference voltage vector ₁, V ₂, V ₃, together with reference voltage vector V ' _ref, substitute into voltage-second balance equation group:

$\left\{\begin{array}{c}{T}_1{V}_1+T_2{V}_2+T_3{V}_3=T_s{V}_{\mathrm{ref}}^{\′}\\ T_1+T_2+T_3=T_s\end{array}\right.---\left(10\right)$

Solve T ₁, T ₂, T ₃namely traditional three level SVPWM algorithm is completed to the calculating of fundamental space vector action time.With N ₁=1, N ₂=4 derivations carrying out the time:

$V_1=\frac{1}{3}{U}_{\mathrm{dc}1}{e}^{j\frac{\mathrm{\π}}{3}},V_2=\frac{1}{\sqrt{3}}{U}_{\mathrm{dc}1}{e}^{j\frac{\mathrm{\π}}{6}},V_3=\frac{1}{3}{U}_{\mathrm{dc}1}$

Substituted into voltage-second balance equation group to obtain:

$\begin{array}{c}\frac{1}{3}{U}_{\mathrm{dc}1}{T}_3+\frac{1}{\sqrt{3}}{V}_{\mathrm{dc}1}(\cos \frac{\mathrm{\π}}{6}+j\sin \frac{\mathrm{\π}}{6})T_2+\frac{1}{3}{V}_{\mathrm{dc}1}(\cos \frac{\mathrm{\π}}{3}+j\sin \frac{\mathrm{\π}}{3})T_1\\ =V_{\mathrm{ref}}^{\′}({\cos \mathrm{\θ}}_1+j\sin {\mathrm{\θ}}_1)T_s\end{array}---\left(11\right)$

Equation launches according to real part and imaginary part:

$\left\{\begin{array}{c}\frac{1}{2}{V}_{\mathrm{dc}1}{T}_3+\frac{1}{\sqrt{3}}{U}_{\mathrm{dc}1}\cos \frac{\mathrm{\π}}{6}{T}_2+\frac{1}{3}{V}_{\mathrm{dc}1}\cos \frac{\mathrm{\π}}{3}{T}_1=V_{\mathrm{ref}}^{\′}\cos \left({\mathrm{\θ}}_1{T}_s\right)\\ \frac{1}{\sqrt{3}}{U}_{\mathrm{dc}1}\sin \frac{\mathrm{\π}}{6}{T}_2+\frac{1}{3}{V}_{\mathrm{dc}1}{T}_1{V}_{\mathrm{ref}}^{\′}\sin \left({\mathrm{\θ}}_1{T}_s\right)\end{array}\right.---\left(12\right)$

Solve T ₁, T ₂, T ₃be respectively,

$\left\{\begin{array}{c}{T}_1=T_s[1-2k\sin (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_1)]\\ T_2=T_s[2k\sin (\frac{\mathrm{\π}}{3}+{\mathrm{\θ}}_1)-1]\\ T_3=T_s[1-2k\sin {\mathrm{\θ}}_1]\end{array}\right.---\left(13\right)$

in like manner can obtain reference voltage vector when other regions, the action time of basic vector.Table 2 provides N ₁=1 illustrates each basic vector action time.

Table 2 N ₁=1 basic vector table action time

Step 6) time state distributes is as can be seen from three level SVPWM fundamental space polar plot, and vector and on off state one_to_one corresponding in large vector, short vector correspondence 2 groups of on off states, zero vector has 3 groups of on off states.Due in the on off state that occurs within each sampling period, on off state corresponding to short vector often, therefore selects short vector as the start vector in each sampling period.Zero vector can be chosen according to the order of action of on off state.

The order of action of each group of on off state will follow such principle: the change of primary voltage vector can only have the switch motion of a brachium pontis arbitrarily, namely in binary vector represents, only has one to change or not change.Table 3 gives N ₁with n, o, p, each vector race-card when=1, wherein represents that corresponding three-phase is for low level, zero level, high level respectively.

Table 3 N ₁=1 vector state race-card

N 2	Vector state race-card
		1	onn?oon?ooo?poo?ooo?oon?onn
2	oon?ooo?poo?ppo?poo?ooo?oon
		3	onn?oon?pon?poo?pon?oon?onn
4	oon?pon?poo?ppo?poo?pon?oon
		5	onn?pnn?pon?poo?pon?pnn?onn
6	oon?ooo?opo?ppo?opo?ooo?oon

Centrosymmetric seven segmentation SVPWM waveforms are adopted to be distributed to corresponding vector state the action time of basic vector, with N ₁=1, N ₂=1 is example, and the corresponding relation of basic vector action time and vector state as shown in Figure 7.The similar derivation in other regions.

Embodiment recited above is only be described the preferred embodiment of the present invention, not limits the spirit and scope of the present invention.Under the prerequisite not departing from design concept of the present invention; the various modification that this area ordinary person makes technical scheme of the present invention and improvement; all should drop into protection scope of the present invention, the technology contents of request protection of the present invention, all records in detail in the claims.

Claims (3)

1. five level shortcut calculations based on three level; The present invention is carrying out simplify processes based on the basis of three level to five level space vectors; Obtain detailed simplification step by the topological structure of five-electrical level inverter and the operation principle of five-electrical level inverter, it mainly comprises the steps:

1) regarded as by five level space vector figure and be made up of 6 three level polar plots, its basic skills establishes space vector V _refbe θ with the angle of α axle, three level polar plot be numbered N, then define:

According to V _α, V _βand the relational expression between θ this relational expression is substituted in definition, specifically judge the numerical value of N;

2) correction of reference vector is to V according to N value _refcarry out mid point translation, make the starting point of reference voltage vector move to the mid point of each little three level polar plot; After making translation, U _dc1=U _dc/ 2;

3) determine the vector of three level sector, after five level vector median filters to three level vector, three level polar plot can be divided into 6 large sectors, then establish revised space vector V ' _refbe θ with the angle of α axle ₁, three level polar plot sector be numbered N ₁, then define:

According to V _α, V _βand the relational expression between θ this relational expression is substituted in definition, specifically judge the numerical value of N1;

4) three level se ctor partition is that each sector is divided into 6 zonules, for N by the sector segmentation of 6 in three level ₁=1 segments, and region is denoted as N ₂;

Work as θ ₁≤ 30 °, V ' _refin the middle of zonule 1 or 3 or 5; Successively concrete discriminatory analysis is carried out to this below:

1.. the judgement of zonule 1: consider V ' _refprojection on 30 degree of directions, at θ ₁≤ 30 ° lower time, if meet will by restriction relation formula: V ' _β=V ' _refsin θ ₁, V ' _α=V ' _refcos θ ₁, carried out that abbreviation obtains during this relational expression, N can be judged ₂=1;

2.. the judgement of zonule 5: consider V ' _refwith the size of 0A length, A point position V ' _refin the marginal intersection point in region 3 and region 5.At θ ₁≤ 30 ° lower time, if meet will

$\left|\stackrel{\→}{\mathrm{QA}}\right|{\≤V}_{\mathrm{ref}}^{\′}$

By restriction relation formula: V ' _β=V ' _refsin θ ₁, V ' _α=V ' _refcos θ ₁, carried out that abbreviation obtains during this relational expression, N can be judged ₂=1;

3. the judgement in region 3: under 30 degree, the first sector, the judgement in region 3 directly uses exclusive method, neither meets $\sqrt{3}{V}_{\mathrm{\α}}^{\′}+V_{\mathrm{\β}}^{\′}\≤\frac{1}{\sqrt{3}}{U}_{\mathrm{dc}1}$ Also do not meet $\sqrt{3}{V}_{\mathrm{\α}}^{\′}-V_{\mathrm{\β}}^{\′}\≥\frac{1}{\sqrt{3}}{U}_{\mathrm{dc}1}$ Time, then between judging that reference voltage is in area 3;

4. as 30 °≤θ ₁≤ 60 °, V ' _refin the middle of zonule 2 or 4 or 6; Concrete determination methods and θ ₁≤ 30 ° is similar, wherein region 4, determines by first determining that region 2 and 6 carries out getting rid of;

5. N is worked as ₁=2,3,4,5, when 6, judge method and the N of zonule ₁=1 is similar;

5) Time Calculation method is behind the region judging reference voltage vector place, according to the rule of NTV, can find three basic vector V of synthesized reference voltage vector ₁, V ₂, V ₃, together with reference voltage vector V ' _ref, substitute into voltage-second balance equation group:

$\left\{\begin{array}{c}{T}_1{V}_1+T_2{V}_2+T_3{V}_3=T_S{V}_{\mathrm{ref}}^{\′}\\ T_1+T_2+T_3=T_s\end{array}\right.$

Solve T ₁, T ₂, T ₃namely traditional three level SVPWM algorithm is completed to the calculating of fundamental space vector action time; According to relational expression in like manner can obtain reference voltage vector when other regions, the action time of basic vector;

6) time state distributes is adopt centrosymmetric seven segmentation SVPWM waveforms to be distributed to corresponding vector state the action time of basic vector, as can be seen from three level SVPWM fundamental space polar plot, vector and on off state one_to_one corresponding in large vector, the corresponding 2 groups of on off states of short vector, zero vector has 3 groups of on off states; Due in the on off state that occurs within each sampling period, on off state corresponding to short vector often, therefore selects short vector as the start vector in each sampling period; Zero vector can be chosen according to the order of action of on off state.The order of action of each group of on off state will follow such principle: the change of primary voltage vector can only have the switch motion of a brachium pontis arbitrarily, namely in binary vector represents, only has one to change or not change.

2. the five level shortcut calculations based on three level according to claim 1, it is characterized in that: the topological structure of described five-electrical level inverter: the single armed topological structure of diode clamp type Five-level converter: C1, C2, C3 and C4 are dc-link capacitance, and capacitance voltage value is 1/4th DC bus-bar voltage; 8 switching power devices (S1 ~ S8) series connection of every phase brachium pontis, S1 and S5, S2 and S6, S3 and S7 during normal work, and the complementary conducting of S4 and S8, and often kind of level has the conducting simultaneously of 4 device for power switching; VD1, VD2, VD3, VD4, VD5 and VD6 are clamp diode.

3. the five level shortcut calculations based on three level according to claim 1, it is characterized in that: the operation principle of described five-electrical level inverter: the every phase brachium pontis of five-electrical level inverter has 5 operating states, there is altogether 53=125 operating state, if with 0,1,2,3, the 4 output level 1/2V representing every phase brachium pontis respectively _dc, 1/4V _dc, 0 ,-1/4V _dc,-1/2V _dc, then according to space-vector definitions, the output voltage three dimensional vector diagram of five-electrical level inverter can be obtained, as shown in Fig. 2 left side; 125 space voltage vector 61 positions in figure, wherein 1 zero vector position corresponds to 5 redundant vectors, and all the other 60 non-zero positions correspond to 120 redundant vectors; The voltage magnitude that in figure, each vector position is corresponding is respectively: 2/3V _dc, 1/2V _dc, 1/3V _dc, 1/6V _dc, 0; And as can be seen from Figure, along with the increase of voltage vector magnitude, redundancy voltage vector quantities corresponding is with it fewer; On outermost regular hexagon, the redundancy voltage vector of each voltage vector position only has one.