CN101882884B - Method for modulating generalized vector of three-phase three-wire two-level inverter - Google Patents

Abstract

The invention discloses a method for modulating a generalized vector of a three-phase three-wire two-level inverter. The method comprises the following steps: (1) obtaining a space vector expected to be output by an inverter control system, wherein the space vector is named as a reference space vector Vref; (2) determining a large sector and small sector in which the Vref is positioned; (3) calculating the action time of a vector participating in synthesis; and (4) selecting a vector modulation method to synthetize a three-phase PWM signal according to the calculated action time of the space vector and needs. Compared with the existing generalized discontinuous vector modulation concept, the invention has the biggest differences that the novel generalized vector modulation method provided by the invention can be used for realizing the switching among various vector modulation methods, does not only refer to the switching among discontinuous vector modulation methods; and all the modulation methods can be unified into one method; different vector modulation methods can be realized by only amending two vector values, thus realizing the slip form switching among different modulation methods.

Description

Method for modulating generalized vector of three-phase three-wire two-level inverter

Technical field

The present invention relates to the inverter field, particularly three-phase three-wire two-level inverter field, specifically a kind of method for modulating generalized vector of three-phase three-wire two-level inverter.The method can be applicable to all power inverters and the derived product thereof of three-phase three-wire two-level inverter topological structure, comprises photovoltaic DC-to-AC converter, wind electric converter, UPS, frequency converter and active filter etc.

Background technology

For the inverter of 100kVA power and above grade, owing to three-phase three-phase two level topologys are used widely than three-phase three-wire three-level is more ripe.Today that New Energy Industry develops increasingly, the pollution level that the efficient of power inverter reaches electrical network more and more comes into one's own.From the modulator approach angle, different modulator approaches is than in the situation, different on the impact of THDi and efficient in different power grades and different modulating.So can select suitable modulator approach by optimum organization, to obtain more excellent performance in good time.

Based on this, A.H.Hava, R.J.Kerkman, T.A.Lipo, A High Performance Generalized Discontinuous PWM Algorithm, IEEE Applied Power Electronics Conference, Vol.2, Atlanta, Geogia, February, 1997 have proposed a kind of broad sense discontinuous vector PWM(Pulse Width Modulation of starting phase angle thought of movement-based zero sequence modulation product) modulator approach, the method has only comprised all interrupted vector modulation methods, does not comprise continuous vector modulation method, so when needs switched between continuous and discontinuous vector modulation method, this algorithm was helpless.K.S.Gowri, B.Reddy, C.S.Babu, High-Performance Generalized ADPWM Algorithm for VSI Fed IM Drives for Reduced Switching Losses, Internation Journal of Recent Trends in Engineering, 2 (5), Nov.2009 adopts the thought of cutting apart zero vector, equally also realized broad sense discontinuous vector PWM modulator approach, but still can not switch continuously and between the discontinuous vector modulation method.

For the optimization system performance, the modulator approach of combination not only need to be switched between interrupted modulator approach, more will switch in continuous and interrupted modulation, and existing modulator approach obviously can't satisfy this requirement.

Summary of the invention

What the present invention will solve is for three-phase three-wire two-level inverter, existing broad sense discontinuous vector modulation method can't realize that continuous Vector Modulation is to the problem of the sliding formwork switching of discontinuous vector modulation, aim to provide a kind of new generalized vector modulation concept, on this basis, be easy to realize that the sliding formwork between the different modulation switches.

The technical scheme that addresses the above problem employing is: method for modulating generalized vector of three-phase three-wire two-level inverter is characterized in that may further comprise the steps:

(1) can be obtained the space voltage vector of desired output by the three-phase three-wire two-level inverter control system, be called reference space voltage vector Vref;

(2) determine residing large sector and the little sector by dividing with laxative remedy of described reference space voltage vector Vref

(2.1) on off state changes to space voltage vector

The topological structure of three-phase three-wire two-level inverter is comprised of three switch brachium pontis, and the complementary conducting of the upper and lower switching tube of each switch brachium pontis is with the three-phase symmetric voltage v of inversion output _AN, v _BN, v _CNBe converted into a space voltage vector on α β complex plane

$V=\frac{2}{3}(v_{\mathrm{aN}}+\mathrm{\α}{v}_{\mathrm{bN}}+{\mathrm{\α}}^2{v}_{\mathrm{cN}})---\left(1\right)$

In the formula, α=e ^{J2 π/3}, α ²=e ^{J4 π/3}Represent, j is imaginary unit;

Definition switching variable S _a, S _b, S _cThe output state of three switch brachium pontis of expression, when

Switching tube conducting in the expression, corresponding switch brachium pontis output for the voltage of bus mid point O is+V _Bus/ 2, wherein, V _BusBe the input direct voltage of three-phase three-wire two-level inverter, when

The lower switching tube conducting of expression, corresponding switch brachium pontis output to the voltage of bus mid point O is-V _Bus/ 2; Because the necessary complementary conducting of the upper and lower switching tube of each switch brachium pontis, so, three-phase three-wire two-level inverter co-exists in eight kinds of switch combinations; Phase voltage sum take the O point as reference potential is not equal to zero, and the output of the three-phase take line voltage neutral point N as reference potential symmetrical voltage satisfies equilibrium condition, can get

$\left\{\begin{array}{c}{v}_{\mathrm{aN}}=v_{\mathrm{aO}}+v_{\mathrm{ON}}\\ v_{\mathrm{bN}}=v_{\mathrm{bO}}+v_{\mathrm{ON}}\\ v_{\mathrm{cN}}=v_{\mathrm{cO}}+v_{\mathrm{ON}}\end{array}\right.---\left(2\right)$

By v _AN+ v _BN+ v _CN=0, can get v _ON=-1/3 (v _AO+ v _BO+ v _CO), can get thus

$\left\{\begin{array}{c}{v}_{\mathrm{aN}}=1/3(2v_{\mathrm{aO}}-v_{\mathrm{bO}}-v_{\mathrm{cO}})\\ v_{\mathrm{bN}}=1/3(2v_{\mathrm{bO}}-v_{\mathrm{aO}}-v_{\mathrm{cO}})\\ v_{\mathrm{cN}}=1/3(2v_{\mathrm{cO}}-v_{\mathrm{aO}}-v_{\mathrm{bO}})\end{array}\right.---\left(3\right)$

For different switch combinations, three-phase three-wire two-level inverter utilizes formula (1) and formula (3) with regard to exportable 8 kinds of voltage statuss combination, can get 8 space voltage vector V shown in the following table 1 ₀To V ₇:

Table 1

In the table 1, V _αThe component of representation space voltage vector on the α axle of α β complex plane; V _βThe component of representation space voltage vector on the β axle of α β complex plane;

(2.2) determine the residing zone of described reference space voltage vector Vref

Take non-zero vector as the border, space voltage vector figure is divided into 6 large sectors, again described 6 large sectors are divided separately the one-tenth 1. with the 2. two little sectors, determine the residing large sector of described reference space voltage vector Vref and little sector, and then determine to participate in synthetic space voltage vector;

(3) calculate the action time that participates in synthetic space voltage vector according to the synthetic weber balance principle of space voltage vector;

(4) according to the action time of the space voltage vector that calculates, carry out by the following method Vector Modulation, synthetic three-phase PWM signal;

Minimum as principle take switch motion when the sector switch, determine the sequence of movement of space voltage vector; Defining each large sectors zero vector action time is tz=T-t1-t2, be tz1=k1*tz the action time at 1. little sector definition zero vector V0,0≤k1≤1 is tz2=k2*tz in the action time of the 2. little sector definition zero vector V0 of identical large sector, 0≤k2≤1; Give k1 and k2 assignment, can obtain the vector modulation method of broad sense; Wherein T is half switch periods of switching tube, and t1 and t2 are the action time of two non-zero vectors in this large sector, and k1 and k2 are the zero vector weight coefficient of action time.

When needs switch to another kind of modulator approach with a kind of modulator approach, can adopt two kinds of methods: the 1st kind of method, directly revise k ₁And k ₂Value is the required numerical value of target modulation method.The 2nd kind of method, k ₁And k ₂Value slowly changes to the required numerical value of target modulation method, k according to certain track ₁And k ₂The preferential straight line path of selecting.

From different being of existing broad sense discontinuous vector modulation concept maximum, new method for modulating generalized vector proposed by the invention can be realized the switching between the various vector modulation methods, and not only refers to the switching between the discontinuous vector modulation method.All modulator approaches all can be unified into a kind of method, only need to revise two variate-values and just can realize different vector modulation methods.

Description of drawings

Below in conjunction with accompanying drawing, the invention will be further described.

Fig. 1 is the three-phase three-wire two-level inverter topological diagram.

Fig. 2 is the space voltage vector distribution map.

Fig. 3 is the space voltage vector distribution map that is divided into behind the little sector.

Fig. 4 is the 3rd sector switching sequence figure, and wherein (1) is the district switching sequence figure that 1. distinguishes, and (2) are the district switching sequence figure that 2. distinguishes.

Fig. 5 is the evolution diagram between the different SVM methods.

Fig. 6 is the Vector Modulation oscillogram after sliding formwork switches, and the vector transfer sequence is A → B → C → B → A.

Fig. 7 is the Vector Modulation oscillogram after sliding formwork switches, and the vector transfer sequence is A → B → C → A → B.

Embodiment

1. space voltage vector modulation principle

1.1 on off state changes to space voltage vector

The three-phase three-wire two-level topological structure as shown in Figure 1, this circuit is comprised of three switch brachium pontis, the complementary conducting of the upper and lower switching tube of each switch brachium pontis.The three-phase symmetric voltage v of inversion output _AN, v _BN, v _CNCan change into a space voltage vector on α β complex plane

$V=\frac{2}{3}(v_{\mathrm{aN}}+\mathrm{\α}{v}_{\mathrm{bN}}+{\mathrm{\α}}^2{v}_{\mathrm{cN}})---\left(4\right)$

In the formula, α=e ^{J2 π/3}, α ²=e ^{J4 π/3}Represent, j is imaginary unit.

Definition switching variable S _a, S _b, S _cThe output state of three switch brachium pontis of expression, when

Switching tube conducting in the expression, corresponding switch brachium pontis output for the voltage of bus mid point O is+V _Bus/ 2, when

The lower switching tube conducting of expression, corresponding switch brachium pontis output to the voltage of bus mid point O is-V _Bus/ 2.Because the necessary complementary conducting of the upper and lower switching tube of each switch brachium pontis, so, three-phase three-wire two-level inverter co-exists in eight kinds of switch combinations.Phase voltage sum take the O point as reference potential is not equal to zero, does not namely satisfy condition of three-phase balance, and the output of the three-phase take line voltage neutral point N as reference potential symmetrical voltage satisfies equilibrium condition, so need pass through v _AN, v _BN, v _CN, derive v _AO, v _BO, v _COCan get according to circuit diagram 1

$\left\{\begin{array}{c}{v}_{\mathrm{aN}}=v_{\mathrm{aO}}+v_{\mathrm{ON}}\\ v_{\mathrm{bN}}=v_{\mathrm{bO}}+v_{\mathrm{ON}}\\ v_{\mathrm{cN}}=v_{\mathrm{cO}}+v_{\mathrm{ON}}\end{array}\right.---\left(5\right)$

By v _AN+ v _BN+ v _CN=0, can get v _ON=-1/3 (v _AO+ v _BO+ v _CO), can get thus

$\left\{\begin{array}{c}{v}_{\mathrm{aN}}=1/3(2v_{\mathrm{aO}}-v_{\mathrm{bO}}-v_{\mathrm{cO}})\\ v_{\mathrm{bN}}=1/3(2v_{\mathrm{bO}}-v_{\mathrm{aO}}-v_{\mathrm{cO}})\\ v_{\mathrm{cN}}=1/3(2v_{\mathrm{cO}}-v_{\mathrm{aO}}-v_{\mathrm{bO}})\end{array}\right.---\left(6\right)$

For different switch combinations, three-phase three-wire two-level inverter utilizes formula (4) and formula (6) with regard to exportable 8 kinds of voltage statuss combination, the space voltage vector relation table shown in can table 1.

Table 1 switch combination and phase voltage corresponding relation

Can get vector distribution map shown in Figure 1 according to table 1.

1.2 reference vector is synthetic

For synthetic given reference voltage vector, need to determine the position of reference vector.Take non-zero vector as the border, can be divided into 6 sectors to space voltage vector figure, as shown in Figure 2.At any time, reference vector all will be in (satisfying linear modulation) in the middle of in these triangles one.The three-phase reference voltage of any balance all can represent with a space voltage vector on space voltage vector figure.Less for the harmonic wave that makes output voltage, reduce the switch motion number of times, at each PWM control cycle T _sIn, reference vector can synthesize with space voltage vector corresponding to its residing sector.

Suppose that the vector that need synthesize is in the 3rd sector as shown in Figure 2, then uses vector V ₀, V ₇, V ₄, V ₆Come the synthesized reference vector V _Ref=V _RefP(cos θ+jsin θ).The weber balance principle synthetic according to space voltage vector can get

$\left\{\begin{array}{c}{V}_{\mathrm{ref}}{T}_s=V_4{\mathrm{<figure-callout\; id="4"\; label="t"\; filenames="HSA00000167139600012.png"\; state="\{\{state\}\}">t</figure-callout>}}_4+V_6{t}_6\\ T_s={\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="HSA00000167139600022.png,HSA00000167139600031.png"\; state="\{\{state\}\}">t</figure-callout>}}_0+t_7+{\mathrm{<figure-callout\; id="4"\; label="t"\; filenames="HSA00000167139600012.png"\; state="\{\{state\}\}">t</figure-callout>}}_4+t_6\end{array}\right.---\left(7\right)$

In the formula, t ₀, t ₇, t ₄, t ₆Be respectively vector V ₀, V ₇, V ₄, V ₆Action time, Vrefp is the peak value of reference vector.After vector substitution formula (7), solving equations can get

$\left\{\begin{array}{c}{\mathrm{<figure-callout\; id="4"\; label="t"\; filenames="HSA00000167139600012.png"\; state="\{\{state\}\}">t</figure-callout>}}_4=\frac{\sqrt{3}{T}_s\left|V_{\mathrm{ref}}\right|}{V_{\mathrm{Bus}}}\cos (\mathrm{\&theta;}+\mathrm{\&pi;}/6)\\ {\mathrm{<figure-callout\; id="6"\; label="t"\; filenames="HSA00000167139600012.png"\; state="\{\{state\}\}">t</figure-callout>}}_6=\frac{\sqrt{3}{T}_s\left|V_{\mathrm{ref}}\right|}{V_{\mathrm{Bus}}}\cos (\mathrm{\&theta;}+3\mathrm{\&pi;}/2)\\ {\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="HSA00000167139600022.png,HSA00000167139600031.png"\; state="\{\{state\}\}">t</figure-callout>}}_0+t_7=T_s-t_4-t_6\end{array}\right.---\left(8\right)$

In like manner, when reference vector is positioned at other sector, also can calculate the action time of the synthetic vector of parameter vector.

1.3 determine the vector sequence of operation

In order to realize discontinuous vector modulation and the continuously switching of the sliding formwork between the Vector Modulation, a kind of generalized vector modulation concept has been proposed.In order to explain, provide as shown in Figure 3 vector distribution map, Fig. 3 be exactly on Fig. 2 basis 1,2,3,4,5,6 six large sectors, again each large sector is divided into separately 1. with 2. two little sectors.For so that during sector switch, switch motion is minimum, the circular arc arrow is expressed the sequence of movement of vector among the figure.For example in the 3rd sector, arrange first vector [100], arrange again vector [110].[V7] can see in 1. district in the 1st sector, is illustrated in this district and only uses vector V 7 as zero vector; [V0] can see in 2. district in the 1st sector, is illustrated in this district and only uses vector V 0 as zero vector.

Be without loss of generality the explanation Generalized S VM concept as an example of the 3rd sector example.The sequence of operation of vector has been mentioned in the front, and in the 3rd sector, if adopt the SVPWM method, then action sequence as shown in Figure 4.Suppose that half switch periods is T, [100] vector and [110] vector are respectively t1 and t2 action time in half period, and definition zero vector action time is tz=T-t1-t2.Be tz1=k1*tz the action time at the 1. area definition zero vector V0 of the 3rd sector, 0≤k1≤1; Similarly, be tz2=k2*tz the action time that is defined in the 2. area definition zero vector V0 of the 3rd sector, 0≤k2≤1, and k1 and k2 are the zero vector weight coefficient of action time.Allow k1 and k2 get different values, can obtain the space voltage vector adjustment method of broad sense.

For example, when k1=k2=0.5, can obtain the SVPWM method; Work as k1=0, during k2=0, then can obtain the DPWMMIN method; Work as k1=1, during k2=0, can obtain the DPWM1 method.These three kinds of methods available three coordinate points under k1 and k2 coordinate represent, as shown in Figure 5.Each point represents a kind of SVM method among the figure, and for example the A point is the SVPWM method, and the B point is the DPWMMIN method, and the C point is the DPWM1 method.As seen, the Generalized S VM method that proposes has comprised existing SVM method.

If current modulator approach is the A point, in the time of need to switching to the B point, two kinds of changing methods are arranged.The 1st kind, directly revise k1 and the k2 value is B point coordinates value, this method is called direct-cut operation; The 2nd kind, allow k1 and k2 value slowly be reduced to B point coordinates value, this method is called sliding formwork and switches.Sliding formwork switches a lot of paths, and straight line path is selected in suggestion, such as AB among Fig. 5 and BC straight line.

2. new space voltage vector is modulated performing step

(1) can be obtained the space voltage vector of desired output by the three-phase three-wire two-level inverter control system, be called reference space voltage vector Vref;

(2) determine large sector and the little sector of described reference space voltage vector;

(3) calculate the action time that participates in synthetic vector;

(4) according to action time and the required selection vector modulation method of the space voltage vector that calculates, give k1 and k2 assignment, synthetic three-phase PWM signal.

3. simulating, verifying

Method for modulating generalized vector of the present invention is carried out simulating, verifying, and the result as shown in Figure 6 and Figure 7.As can be seen from the figure, realized that the sliding formwork between continuous Vector Modulation and the discontinuous vector modulation switches.

What should be understood that is: above-mentioned example is just to explanation of the present invention, rather than limitation of the present invention, and any innovation and creation that do not exceed in the connotation scope of the present invention all fall within protection scope of the present invention.

Claims (5)

1. method for modulating generalized vector of three-phase three-wire two-level inverter is characterized in that may further comprise the steps:

(1) can be obtained the space voltage vector of desired output by the three-phase three-wire two-level inverter control system, be called reference space voltage vector Vref;

(2) determine residing large sector and the little sector by dividing with laxative remedy of described reference space voltage vector Vref;

(2.1) on off state changes to space voltage vector

The topological structure of three-phase three-wire two-level inverter is comprised of three switch brachium pontis, and the complementary conducting of the upper and lower switching tube of each switch brachium pontis is with the three-phase symmetric voltage of inversion output Be converted into a space voltage vector on α β complex plane

In the formula, α=e ^{J2 π/3}, α ²=e ^{J4 π/3}Represent, j is imaginary unit;

Definition switching variable S _a, S _b, S _cThe output state of three switch brachium pontis of expression, when

Switching tube conducting in the expression, corresponding switch brachium pontis output for the voltage of bus mid point O is+V _Bus/ 2, wherein, V _BusBe the input direct voltage of three-phase three-wire two-level inverter, when

The lower switching tube conducting of expression, corresponding switch brachium pontis output to the voltage of bus mid point O is-V _Bus/ 2; Because the necessary complementary conducting of the upper and lower switching tube of each switch brachium pontis, so, three-phase three-wire two-level inverter co-exists in eight kinds of switch combinations; Phase voltage sum take the O point as reference potential is not equal to zero, and the output of the three-phase take line voltage neutral point N as reference potential symmetrical voltage satisfies equilibrium condition, can get

In the formula, v _ONVoltage between three-phase three-wire two-level inverter input direct voltage mid point O and the neutral point of electric network N;

By v _AN+ v _BN+ v _CN=0, can get v _ON=-1/3 (v _AO+ v _BO+ v _CO), can get thus

For different switch combinations, three-phase three-wire two-level inverter utilizes formula (1) and formula (3) with regard to exportable 8 kinds of voltage statuss combination, can get 8 space voltage vector V shown in the following table 1 ₀To V ₇:

Table 1 switch combination and phase voltage corresponding relation

In the table 1, V _αThe component of representation space voltage vector on the α axle of α β complex plane; V _βThe component of representation space voltage vector on the β axle of α β complex plane;

(2.2) determine the residing zone of described reference space voltage vector Vref

Take non-zero vector as the border, space voltage vector figure is divided into 6 large sectors, again described 6 large sectors are divided into separately the 1. with the 2. two little sectors, determine the residing large sector of described reference space voltage vector Vref and little sector, and then determine to participate in synthetic space voltage vector;

(3) calculate the action time that participates in synthetic space voltage vector according to the synthetic weber balance principle of space voltage vector;

(4) according to the action time of the space voltage vector that calculates, carry out by the following method Vector Modulation, synthetic three-phase PWM signal:

Minimum as principle take switch motion when the sector switch, determine the sequence of movement of space voltage vector; Defining each large sectors zero vector action time is tz=T-t1-t2, be tz1=k1*tz the action time at 1. little sector definition zero vector V0,0≤k1≤1 is tz2=k2*tz in the action time of the 2. little sector definition zero vector V0 of identical large sector, 0≤k2≤1; Give k1 and k2 assignment, can obtain the vector modulation method of broad sense; Wherein T is half switch periods of switching tube, and t1 and t2 are the action time of two non-zero vectors in this large sector, and k1 and k2 are the zero vector weight coefficient of action time.

2. method for modulating generalized vector of three-phase three-wire two-level inverter as claimed in claim 1, it is characterized in that allowing k1 and k2 get different values, can obtain different space voltage vector modulator approaches, when needs switch to another kind of modulator approach with a kind of modulator approach, directly revise k1 and k2 value and be the required numerical value of target modulation method.

3. method for modulating generalized vector of three-phase three-wire two-level inverter as claimed in claim 1; it is characterized in that allowing k1 and k2 get different values; can obtain different space voltage vector modulator approaches; when needs switched to another kind of modulator approach with a kind of modulator approach, k1 and k2 value slowly changed to the required numerical value of target modulation method according to certain track.

4. method for modulating generalized vector of three-phase three-wire two-level inverter as claimed in claim 3 is characterized in that k1 and k2 select straight line path.

5. such as any described method for modulating generalized vector of three-phase three-wire two-level inverter of claim 1-4, it is characterized in that carrying out sector switch by following vector sequence of movement: in the 1st large sector, arrange first vector [010], arrange again vector [110]; In the 2nd large sector, arrange first vector [100], arrange again vector [101]; In the 3rd large sector, arrange first vector [100], arrange again vector [110]; In the 4th large sector, arrange first vector [001], arrange again vector [011]; In the 5th large sector, arrange first vector [010], arrange again vector [011]; In the 6th large sector, arrange first vector [001], arrange again vector [101].

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