CN103986361B - Method for space vector pulse width modulation of two-level converter - Google Patents

Abstract

The invention relates to a method for space vector pulse width modulation of a two-level converter and belongs to the technical field of power electronics and conversion. The method includes the steps that according to sampling values of a three-phase reference voltage, the maximum value and the minimum value of the three-phase reference voltage are calculated, connection time of a three-phase switching device in a sampling period is obtained through direct calculation, and therefore a control signal of each switching device is obtained. According to the method, coordinate transformation and sector judgment are not needed, operations of irrational numbers and trigonometric functions are avoided, the switching control signals of the devices can be obtained only by a small number of comparison operations and simple four arithmetic operations, an algorithm flow is simple and easy to achieve, the calculated amount is small, optimal control over midpoint electric potential low-frequency components on the direct current side can be achieved, cost of a processor in the space vector pulse width modulation technology is reduced, and generality of the space vector pulse width modulation technology is improved.

Description

A kind of space vector width pulse modulation method of two level current transformers

Technical field

The present invention relates to a kind of space vector width pulse modulation method of two level current transformers, belong to power electronics and unsteady flow skill Art field.

Background technology

Pulse modulation technology is the key technology realizing electric energy conversion based on the current transformer of power electronic devices, current two electricity The pulse modulation technology that flat current transformer (its circuit diagram is as shown in Figure 1) is commonly used includes SPWM Technique and space vector arteries and veins Two kinds of wide modulation technique.Compared with SPWM Technique, space vector pulse width modulation has fast response time, direct current Voltage utilization is high, the advantages of be easy to Digital Implementation, thus obtained extensive research and applied.

Traditional space vector pulse width modulation needs three-phase reference voltage to be carried out with abc- α β coordinate transform, according to α β The phase angle of voltage vector under coordinate system, judges voltage vector place sector (as shown in Figure 2), and passes through trigonometric function operation, obtains To the action time of two adjacent basic vectors of voltage vector, and then obtain each switching device of three-phase within a sampling period ON time, and finally obtain the switch controlling signal of each switching device.Due to needing to carry out coordinate transform, sector judges, Calculate vector action time and it needs to carry out substantial amounts of irrational number and trigonometric function operation, therefore traditional space vector pulse width Modulation technique algorithm is complicated, operand is big, and this proposes higher requirement to the operational performance of digital processing unit, also improves place The cost of reason device.For realizing the rapid computations of space vector pulse width modulation, Chinese scholars propose some method for simplifying, But it is mainly reflected in simplification sector judgment principle, reduces the aspects such as trigonometric function operation, and algorithm remains a need for carrying out coordinate in itself Conversion and sector judge, containing substantial amounts of judgement branch and trigonometric function operation, arithmetic speed lifting is simultaneously inconspicuous.Document [1] (Zhou Weiping, Wu Zhengguo, Tang Jingsong wait the equivalent algorithm of .svpwm and the essential connection [j] of svpwm and spwm. Chinese motor work Journey journal, 2006,1 (2): 133-137.) a kind of simplification algorithm of svpwm is proposed, this simplification algorithm does not substantially need to carry out Coordinate transform, but need to carry out sector judgement, algorithm is realized still more complicated.Document [2] (Fang Sichen, Li Dan, cycle, etc. new Type no sector spatial vector pulse width modulation algorithm [j]. Proceedings of the CSEE, 2008,28 (30): 35-40.) by setting up It is proposed that one kind no sector svpwm algorithm, this algorithm does not need to carry out sector judgement to two 120 ° of phase space coordinate systems, and algorithm is real Existing relatively simple, but need to carry out coordinate transform computing twice, the operand of irrational number and trigonometric function is still larger.

Content of the invention

The purpose of the present invention is to propose to a kind of space vector width pulse modulation method of two level current transformers, existing space is sweared Amount pulse duration modulation method improves, and saves the coordinate transform in existing method and sector judges, to simplify space vector pulse width Modulation, shortens operation time, reduces storage, improves versatility.

The space vector width pulse modulation method of two level current transformers proposed by the present invention, comprises the following steps:

(1) in a sampling period t_sStart time t₀, the three-phase reference voltage of two level current transformers is sampled, Obtain t₀The three-phase reference voltage in moment, is designated as u respectively_a(t₀)、u_b(t₀) and u_c(t₀), by three-phase reference voltage u_a(t₀)、u_b (t₀) and u_c(t₀) in maximum be designated as u_max(t₀), minima is designated as u_min(t₀), measure t simultaneously₀Moment two level current transformer DC voltage u_dc；

(2) pass through following formula, calculate above-mentioned sampling period t_sOn the three-phase of interior two level current transformers during the conducting of brachium pontis switch Between length t_a、t_bAnd t_c:

$t_a=\frac{t_s}{u_{\mathrm{dc}}}[u_a\left(t_0\right)-u_{\min }\left(t_0\right)+l],$

$t_b=\frac{t_s}{u_{\mathrm{dc}}}[u_b\left(t_0\right)-u_{\min }\left(t_0\right)+l],$

$t_c=\frac{t_s}{u_{\mathrm{dc}}}[u_c\left(t_0\right)-u_{\min }\left(t_0\right)+l],$

Wherein, l=k [u_dc-u_max(t₀)+u_min(t₀)], k is for accounting for whole zero vector effects zero vector (111) action time The ratio of time, the span of k is k ∈ [0,1]；

(3) utilize following formula, be calculated brachium pontis on the three-phase of two level current transformers and switch in sampling period t_sInterior conducting Moment t_aon、t_bonAnd t_con:

$t_{\mathrm{aon}}=t_0+\frac{1}{2}(t_s-t_a),$

$t_{\mathrm{bon}}=t_0+\frac{1}{2}(t_s-t_b),$

$t_{\mathrm{con}}=t_0+\frac{1}{2}(t_s-t_c),$

And turn off moment t_aoff、t_boffAnd t_coff:

$t_{\mathrm{aoff}}=t_0+\frac{1}{2}(t_s+t_a),$

$t_{\mathrm{boff}}=t_0+\frac{1}{2}(t_s+t_b),$

$t_{\mathrm{coff}}=t_0+\frac{1}{2}(t_s+t_c);$

(4) utilize following formula, obtain control signal s of brachium pontis switch on the three-phase of two level current transformers_ap(t)、s_bp(t) and s_cp(t):

$s_{\mathrm{ap}}\left(t\right)=\left\{\begin{array}{c}1,t\&element;[t_{\mathrm{aon}},t_{\mathrm{aoff}}]\\ 0,t\&notelement;[t_{\mathrm{aon}},t_{\mathrm{aoff}}]\end{array}\right.,$

$s_{\mathrm{bp}}\left(t\right)=\left\{\begin{array}{c}1,t\&element;[t_{\mathrm{bon}},t_{\mathrm{boff}}]\\ 0,t\&notelement;[t_{\mathrm{bon}},t_{\mathrm{boff}}]\end{array}\right.$

$s_{\mathrm{cp}}\left(t\right)=\left\{\begin{array}{c}1,t\&element;[t_{\mathrm{con}},t_{\mathrm{coff}}]\\ 0,t\&notelement;[t_{\mathrm{con}},t_{\mathrm{coff}}]\end{array}\right.$

(5) utilize following formula, obtain control signal s of brachium pontis switch under the three-phase of two level current transformers_an(t)、s_bn(t) and s_cn(t):

$s_{\mathrm{an}}\left(t\right)=\left\{\begin{array}{c}0,t\&element;[t_{\mathrm{aon}}-\mathrm{\δt},t_{\mathrm{aoff}}+\mathrm{\δt}]\\ 1,t\&notelement;[t_{\mathrm{aon}}-\mathrm{\δt},t_{\mathrm{aoff}}+\mathrm{\δt}]\end{array}\right.,$

$s_{\mathrm{bn}}\left(t\right)=\left\{\begin{array}{c}0,t\&element;[t_{\mathrm{bon}}-\mathrm{\δt},t_{\mathrm{boff}}+\mathrm{\δt}]\\ 1,t\&notelement;[t_{\mathrm{bon}}-\mathrm{\δt},t_{\mathrm{boff}}+\mathrm{\δt}]\end{array}\right.$

$s_{\mathrm{cn}}\left(t\right)=\left\{\begin{array}{c}0,t\&element;[t_{\mathrm{con}}-\mathrm{\δt},t_{\mathrm{coff}}+\mathrm{\δt}]\\ 1,t\&notelement;[t_{\mathrm{con}}-\mathrm{\δt},t_{\mathrm{coff}}+\mathrm{\δt}]\end{array}\right.$

Wherein, δ t is Dead Time, and span is 1-10 microsecond.

The space vector width pulse modulation method of two level current transformers proposed by the present invention, its advantage is:

The space vector width pulse modulation method of two level current transformers of the present invention, the directly sampling according to three-phase reference voltage Value calculates threephase switch device ON time within the sampling period and, it is not necessary to carry out coordinate transform and sector judgement, realizes process In be not required to carry out trigonometric function operation, thus also need not store trigonometric table, only need to carry out a small amount of comparison operation and simple Four arithmetic operation can get the switch controlling signal of device, method flow is simple, it is easy to accomplish, amount of calculation is little, required calculating Time and memory space greatly reduce, and reduce the processor cost of space vector pulse width modulation, and improve space arrow The versatility of amount pulse modulation technology.Additionally, this inventive method is complete with traditional spatial vector pulse width modulation algorithm effect Identical, can reduce by two electricity by suitably distributing the action time of zero vector, to reduce the switching frequency of two level current transformers The harmonic content of voltage and current in flat current transformer, reduces the electromagnetic noise of two level current transformers, thus improving two level unsteady flows The service behaviour of device.

Brief description

Fig. 1 is the circuit theory diagrams of two level current transformers being related in the inventive method.

Fig. 2 is space vector pulse width modulation space vector of voltage and sector scattergram.

Fig. 3 is the control signal schematic diagram of brachium pontis switch on three-phase in the inventive method.

Fig. 4 is the modulation effect comparison diagram of one embodiment of the present of invention and traditional method.

Specific embodiment

The space vector width pulse modulation method of two level current transformers proposed by the present invention, comprises the following steps:

(1) in a sampling period t_sStart time t₀, the three-phase reference voltage of two level current transformers is sampled, Obtain t₀The three-phase reference voltage in moment, is designated as u respectively_a(t₀)、u_b(t₀) and u_c(t₀), by three-phase reference voltage u_a(t₀)、u_b (t₀) and u_c(t₀) in maximum be designated as u_max(t₀), minima is designated as u_min(t₀), measure t simultaneously₀Moment two level current transformer DC voltage u_dc；

(2) pass through following formula, calculate above-mentioned sampling period t_sOn the three-phase of interior two level current transformers during the conducting of brachium pontis switch Between length t_a、t_bAnd t_c:

$t_a=\frac{t_s}{u_{\mathrm{dc}}}[u_a\left(t_0\right)-u_{\min }\left(t_0\right)+l],$

$t_b=\frac{t_s}{u_{\mathrm{dc}}}[u_b\left(t_0\right)-u_{\min }\left(t_0\right)+l],$

$t_c=\frac{t_s}{u_{\mathrm{dc}}}[u_c\left(t_0\right)-u_{\min }\left(t_0\right)+l],$

Wherein, l=k [u_dc-u_max(t₀)+u_min(t₀)], k is for accounting for whole zero vector effects zero vector (111) action time The ratio of time, the span of k is k ∈ [0,1].As shown in Figure 3, wherein k value and zero vector t action time₇And t₀Pass It is to beBy the suitable value selecting k, it is possible to achieve the different optimization of two level space vector pulsewidth modulations Target.For example, if to reduce switching frequency as optimization aim, k=0；If to reduce harmonic content as optimization aim,If to reduce electromagnetic noise as optimization aim, k takes the random number between [0,1], the k value in (n+1)th sampling period Can be produced by following ordered series of numbers recursion: k (n+1)=4k (n) [1-k (n)], wherein k (0)=0.1

(3) utilize following formula, be calculated brachium pontis on the three-phase of two level current transformers and switch in sampling period t_sInterior conducting Moment t_aon、t_bonAnd t_con:

$t_{\mathrm{aon}}=t_0+\frac{1}{2}(t_s-t_a),$

$t_{\mathrm{bon}}=t_0+\frac{1}{2}(t_s-t_b),$

$t_{\mathrm{con}}=t_0+\frac{1}{2}(t_s-t_c),$

And turn off moment t_aoff、t_boffAnd t_coff:

$t_{\mathrm{aoff}}=t_0+\frac{1}{2}(t_s+t_a),$

$t_{\mathrm{boff}}=t_0+\frac{1}{2}(t_s+t_b),$

$t_{\mathrm{coff}}=t_0+\frac{1}{2}(t_s+t_c);$

(4) utilize following formula, obtain control signal s of brachium pontis switch on the three-phase of two level current transformers_ap(t)、s_bp(t) and s_cp(t):

$s_{\mathrm{ap}}\left(t\right)=\left\{\begin{array}{c}1,t\&element;[t_{\mathrm{aon}},t_{\mathrm{aoff}}]\\ 0,t\&notelement;[t_{\mathrm{aon}},t_{\mathrm{aoff}}]\end{array}\right.,$

$s_{\mathrm{bp}}\left(t\right)=\left\{\begin{array}{c}1,t\&element;[t_{\mathrm{bon}},t_{\mathrm{boff}}]\\ 0,t\&notelement;[t_{\mathrm{bon}},t_{\mathrm{boff}}]\end{array}\right.$

$s_{\mathrm{cp}}\left(t\right)=\left\{\begin{array}{c}1,t\&element;[t_{\mathrm{con}},t_{\mathrm{coff}}]\\ 0,t\&notelement;[t_{\mathrm{con}},t_{\mathrm{coff}}]\end{array}\right.$

(5) utilize following formula, obtain control signal s of brachium pontis switch under the three-phase of two level current transformers_an(t)、s_bn(t) and s_cn(t):

$s_{\mathrm{an}}\left(t\right)=\left\{\begin{array}{c}0,t\&element;[t_{\mathrm{aon}}-\mathrm{\δt},t_{\mathrm{aoff}}+\mathrm{\δt}]\\ 1,t\&notelement;[t_{\mathrm{aon}}-\mathrm{\δt},t_{\mathrm{aoff}}+\mathrm{\δt}]\end{array}\right.,$

$s_{\mathrm{bn}}\left(t\right)=\left\{\begin{array}{c}0,t\&element;[t_{\mathrm{bon}}-\mathrm{\δt},t_{\mathrm{boff}}+\mathrm{\δt}]\\ 1,t\&notelement;[t_{\mathrm{bon}}-\mathrm{\δt},t_{\mathrm{boff}}+\mathrm{\δt}]\end{array}\right.$

$s_{\mathrm{cn}}\left(t\right)=\left\{\begin{array}{c}0,t\&element;[t_{\mathrm{con}}-\mathrm{\δt},t_{\mathrm{coff}}+\mathrm{\δt}]\\ 1,t\&notelement;[t_{\mathrm{con}}-\mathrm{\δt},t_{\mathrm{coff}}+\mathrm{\δt}]\end{array}\right.$

Wherein, δ t is Dead Time, and span is 1-10 microsecond.

One embodiment of the inventive method introduced below:

In the present embodiment, the circuit diagram of two level current transformers with resistance sense load is as shown in figure 1, its structural parameters and operation Condition is as follows:

(1) in a sampling period t_sThe start time t of=0.2ms₀, the three-phase reference voltage of two level current transformers is entered Row sampling, obtains t₀The three-phase reference voltage in moment is u_a(t₀)、u_b(t₀) and u_c(t₀), by three-phase reference voltage u_a(t₀)、u_b (t₀) and u_c(t₀) in the maximum be designated as u_max(t₀), reckling is designated as u_min(t₀), measure t simultaneously₀Moment two level current transformer DC voltage u_dc=0.73kv；

(2) pass through following formula, calculate above-mentioned sampling period t_sOn the three-phase of interior two level current transformers during the conducting of brachium pontis switch Between t_a,t_b,t_cFor:

$\left[\begin{array}{c}{t}_a\\ t_b\\ t_c\end{array}\right]=\frac{t_s}{u_{\mathrm{dc}}}\left[\begin{array}{c}{u}_a\left(t_0\right)-u_{\min }\left(t_0\right)+l\\ u_b\left(t_0\right)-u_{\min }\left(t_0\right)+l\\ u_c\left(t_0\right)-u_{\min }\left(t_0\right)+l\end{array}\right]$

Wherein, l=k [u_dc-u_max(t₀)+u_min(t₀)], k is for accounting for whole zero vector effects zero vector (111) action time The ratio of time, the span of k is k ∈ [0,1], in an embodiment, takes k=0 and k=0.5 checking respectively set forth herein calculating The modulation effect of method.

(3) utilize following formula, be calculated brachium pontis on the three-phase of two level current transformers and switch in sampling period t_sInterior is open-minded Moment t_aon,t_bon,t_con:

$\left[\begin{array}{c}{t}_{\mathrm{aon}}\\ t_{\mathrm{bon}}\\ t_{\mathrm{con}}\end{array}\right]=\left[\begin{array}{c}{t}_0\\ t_0\\ t_0\end{array}\right]+\frac{1}{2}\left[\begin{array}{c}{t}_s-t_a\\ t_s-t_b\\ t_s-t_c\end{array}\right],$

With shutoff moment t_aoff,t_boff,t_coff:

$\left[\begin{array}{c}{t}_{\mathrm{aoff}}\\ t_{\mathrm{boff}}\\ t_{\mathrm{coff}}\end{array}\right]=\left[\begin{array}{c}{t}_0\\ t_0\\ t_0\end{array}\right]+\frac{1}{2}\left[\begin{array}{c}{t}_s+t_a\\ t_s+t_b\\ t_s+t_c\end{array}\right]$

(4) calculated open moment t by above-mentioned_aon,t_bon,t_conWith shutoff moment t_aoff,t_boff,t_coffAs two electricity The control signal of brachium pontis switch on the three-phase of flat current transformer, negates to the control signal of upper brachium pontis switch, obtains lower brachium pontis switch Control signal.Wherein, negate and refer to that the switching signal of lower brachium pontis can be obtained with 1 switching signal deducting upper brachium pontis；Negating When, certain Dead Time should be suitably added when upper and lower brachium pontis on off state switches, dead band time setting is 3 μ s, in dead band In time, the switching signal of upper and lower brachium pontis is 0.

Fig. 4 is the modulation effect figure of above-described embodiment, in figure u_aoFor two level current transformer AC phase voltages, u_abFor two Level current transformer AC line voltage, i_aFor two level current transformer AC phase currents and t_aFor brachium pontis on two level current transformers ON time within a sampling period for the switching device.Wherein, Fig. 4 (a) is using Traditional Space Vector Pulse Width Modulation algorithm And in k=0.5 above-mentioned each amount oscillogram, Fig. 4 (b) is using above-mentioned each amount waveform during inventive algorithm and in k=0.5 Figure, Fig. 4 (c) is above-mentioned each amount oscillogram using Traditional Space Vector Pulse Width Modulation algorithm and in k=0, and Fig. 4 (d) is employing Above-mentioned each amount oscillogram during inventive algorithm and in k=0.As seen from Figure 4, the two level unsteady flows being obtained using the inventive method Device AC phase voltage, line voltage, phase current waveform, two level identical with traditional spatial vector pulse width modulation algorithm On current transformer, ON time within a sampling period for the brachium pontis switching device is also identical, and the inventive method and tradition are described Spatial vector pulse width modulation algorithm modulation effect identical.

Claims (1)

1. a kind of space vector width pulse modulation method of two level current transformers, comprises the following steps:

(1) in a sampling period t_sStart time t₀, the three-phase reference voltage of two level current transformers is sampled, obtains t₀The three-phase reference voltage in moment, is designated as u respectively_a(t₀)、u_b(t₀) and u_c(t₀), by three-phase reference voltage u_a(t₀)、u_b(t₀) and u_c(t₀) in maximum be designated as u_max(t₀), minima is designated as u_min(t₀), measure t simultaneously₀The direct current of moment two level current transformer Side voltage u_dc；

(2) pass through following formula, calculate above-mentioned sampling period t_sThe ON time length of brachium pontis switch on the three-phase of interior two level current transformers t_a、t_bAnd t_c:

$t_a=\frac{t_s}{u_{dc}}\[u_a\left(t_0\right)-u_{\min }\left(t_0\right)+l\],$

$t_b=\frac{t_s}{u_{dc}}\[u_b\left(t_0\right)-u_{\min }\left(t_0\right)+l\],$

$t_c=\frac{t_s}{u_{dc}}\[u_c\left(t_0\right)-u_{min}\left(t_0\right)+l\],$

Wherein, l=k [u_dc-u_max(t₀)+u_min(t₀)], k is for accounting for whole zero vector action time zero vector (111) action time Ratio, the span of k is 0 < k < 1；

(3) utilize following formula, be calculated brachium pontis on the three-phase of two level current transformers and switch in sampling period t_sInterior turn-on instant t_aon、t_bonAnd t_con:

$t_{aon}=t_0+\frac{1}{2}(t_s-t_a),$

$t_{bon}=t_0+\frac{1}{2}(t_s-t_b),$

$t_{\mathrm{con}}=t_0+\frac{1}{2}(t_s-t_c),$

And turn off moment t_aoff、t_boffAnd t_coff:

$t_{aoff}=t_0+\frac{1}{2}(t_s+t_a),$

$t_{boff}=t_0+\frac{1}{2}(t_s+t_b),$

$t_{coff}=t_0+\frac{1}{2}(t_s+t_c);$

(4) utilize following formula, obtain control signal s of brachium pontis switch on the three-phase of two level current transformers_ap(t)、s_bp(t) and s_cp (t):

$s_{ap}\left(t\right)=\{\begin{array}{c}1,t\&element;\&lsqb;t_{aon},t_{aoff}\&rsqb;\\ 0,t\&notelement;\&lsqb;t_{aon},t_{aoff}\&rsqb;\end{array},$

$s_{bp}\left(t\right)=\left\{\begin{array}{c}1,t\&element;\&lsqb;t_{bon},t_{boff}\&rsqb;\\ 0,t\&notelement;\&lsqb;t_{bon},t_{boff}\&rsqb;\end{array}\right.$

$s_{cp}\left(t\right)=\left\{\begin{array}{c}1,t\&element;\&lsqb;t_{con},t_{coff}\&rsqb;\\ 0,t\&notelement;\&lsqb;t_{con},t_{coff}\&rsqb;\end{array}\right.$

(5) utilize following formula, obtain control signal s of brachium pontis switch under the three-phase of two level current transformers_an(t)、s_bn(t) and s_cn (t):

$s_{an}\left(t\right)=\left\{\begin{array}{c}0,t\&element;\&lsqb;t_{aon}-\mathrm{\&delta;}t,t_{aoff}+\mathrm{\&delta;}t\&rsqb;\\ 1,t\&notelement;\&lsqb;t_{aon}-\mathrm{\&delta;}t,t_{aoff}+\mathrm{\&delta;}t\&rsqb;\end{array}\right.,$

$s_{bn}\left(t\right)=\left\{\begin{array}{c}0,t\&element;\&lsqb;t_{bon}-\mathrm{\&delta;}t,t_{boff}+\mathrm{\&delta;}t\&rsqb;\\ 1,t\&notelement;\&lsqb;t_{bon}-\mathrm{\&delta;}t,t_{boff}+\mathrm{\&delta;}t\&rsqb;\end{array}\right.$

$s_{cn}\left(t\right)=\left\{\begin{array}{c}0,t\&element;\&lsqb;t_{con}-\mathrm{\&delta;}t,t_{coff}+\mathrm{\&delta;}t\&rsqb;\\ 1,t\&notelement;\&lsqb;t_{con}-\mathrm{\&delta;}t,t_{coff}+\mathrm{\&delta;}t\&rsqb;\end{array}\right.$

Wherein, δ t is Dead Time, and span is 1-10 microsecond.