CN103259478A - Optimizing and modulating method of five-axle arm inverter - Google Patents

Abstract

The invention discloses an optimizing and modulating method of a five-axle arm inverter, and belongs to the field of control of power electronics and electric drive. Due to the fact that the zero-vector overlapping time of the five-axle arm inverter is fully used for conducting optimization and adjustment on voltage vectors and is used for conducting modulation on a primary idle inverter, voltage using ratio of the five-axle arm inverter is effectively improved and loading-on capacity of the five-axle arm inverter is improved. Re-distribution is conducted on the voltage vectors of the five-axle arm inverter, times of simultaneous motion of a plurality of switches at a zero-vector moment are reduced, backward voltages of voltages of an output line of the inverter are effectively reduced, higher harmonic is lowered, and therefore voltage waveform quality of the output line of the five-axle arm inverter is improved.

Description

The optimization modulator approach of five leg inverters

Technical field

The present invention relates to the control method of converters, relate in particular to and improve the control method that five leg inverters drive two asynchronous machine performances, particularly improve the PWM modulator approach of five leg inverter voltage utilizations and the PWM modulator approach of optimization five leg inverter line voltages output.

Background technology

Simple electric drive system mainly drives a motor bringing onto load speed governing operation by an inverter, yet in many industrial application such as weaving, papermaking, oil recovery, automobile, space flight, need multiple electric motors to be with carrying to change simultaneously mostly, for demands such as performance index, system redundancy, economic actual effects, tend to adopt the multimachine drive system.Studies show that five leg inverters are connected to a public brachium pontis simultaneously as drive source can drive two asynchronous motors independent operating simultaneously on two motors.Compare traditional two inverter parallel-connection structures, five leg inverters not only can reduce the fault-tolerant operation pattern that the system hardware cost also can be used as Double-motor System, can improve the reliability of two asynchronous motor speed-regulating systems effectively.But there are shortcomings such as voltage utilization is low, output line voltage waveform difference in five traditional leg inverter modulation strategies, have limited the application of the two asynchronous machines of five leg inverters driving.

Fig. 1 is that five leg inverters drive two asynchronous machine system topologies, comprises input dc bus (1), five leg inverters (2), 2 asynchronous motors M1 and M2 (3).Wherein (2) comprise five brachium pontis totally 10 switching device S _Ij(i=1,2,3,4,5; J=1,2).I represents the i brachium pontis; Brachium pontis in the j=1 representative, the j=2 representative is brachium pontis down.For ease of hereinafter analyzing, brachium pontis such as Fig. 1 of five leg inverters is divided into two groups: No. 1, No. 2, No. 3 brachium pontis is designated as inverter A, in order to drive M1; No. 3, No. 4, No. 5 brachium pontis is designated as inverter B, in order to drive M2.Wherein No. 3 brachium pontis are connected to the public phase c (c of two motors simultaneously as the public brachium pontis of inverter A and inverter B ₁With c ₂), and all the other brachium pontis are connected to a phase of motor separately.

Fig. 2 is five leg inverter sampling period division tables.

Fig. 3 is the corresponding contravarianter voltage vector of two motors composite diagram.u _R1Corresponding inverter A, u _R2Corresponding inverter B.Suppose the space vector of voltage u of two motors _R1With u _R2Separate and respectively with angular velocity omega 1 and ω 2 motions in the same coordinate system.

For realizing the independent control of two motors, need carry out independent control to each brachium pontis of inverter.Because 2 inverters have a public brachium pontis, so can't directly use traditional SVPWM algorithm.Therefore in order effectively to utilize the public brachium pontis can both operate as normal by inverter A and inverter B, the amplitude of zero vector and the concept that phase place is zero non-productive work state in the control strategy of five leg inverters, have been utilized, with sampling period segmentation modulation as shown in Figure 2: inverter A controls by direct employing SVPWM in preceding half sampling period, and inverter B is operated in zero vector state, and namely No. 4 brachium pontis and No. 5 brachium pontis on off states are consistent with No. 3 brachium pontis all the time.Half sampling period of back, namely inverter B directly adopted the SVPWM modulation in contrast, and inverter A is operated in zero vector state, and No. 1 brachium pontis and No. 2 brachium pontis on off states keep equal state with No. 3 brachium pontis all the time.So just realized in the same sampling period the independent of two motors being controlled.

Fig. 4 divides according to the sampling period shown in the table 1 to obtain five traditional leg inverter modulation strategy space vector of voltage distribution maps.α wherein ₁And β ₁Be respectively synthetic inverter A output voltage vector u in preceding half sampling period _R1Two nonzero voltage space vectors.α ₂And β ₂Be respectively the back and synthesize inverter B output voltage vector u in half sampling period _R2Two nonzero voltage space vectors.α ₁, β ₁, α ₂, β ₂Can calculate the action time in a sampling period according to the SVPWM modulation principle.

Determine to need to determine behind the voltage vector in each sampling period the action time of each voltage vector.Each section non-zero vector duty cycle computing formula is as follows in the application SVPWM modulation principle calculating chart 4:

$\left\{\begin{array}{c}{d}_{\mathrm{\α}1}=\frac{1}{2}{m}_1\sin (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_1)\\ d_{\mathrm{\β}1}=\frac{1}{2}{m}_1\sin {\mathrm{\θ}}_1\\ d_{01}=0.5-d_{\mathrm{\α}1}-d_{\mathrm{\β}1}\\ d_{\mathrm{\α}2}=\frac{1}{2}{m}_2\sin (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_2)\\ d_{\mathrm{\β}2}=\frac{1}{2}{m}_2\sin {\mathrm{\θ}}_2\\ d_{02}=0.5-d_{\mathrm{\α}2}-d_{\mathrm{\β}2}\end{array}\right.---\left(1\right)$

m ₁, m ₂---the modulation ratio of inverter A and inverter B, 0＜m ₁≤ 1,0＜m ₂≤ 1;

θ ₁, θ ₂---the sector angle of inverter A and inverter B.

After calculating the duty ratio of each voltage vector, be the action time that can calculate each vector in a sampling period:

$\left\{\begin{array}{c}{T}_{\mathrm{\α}1}=\frac{1}{2}{m}_1\sin (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_1)T,\\ T_{\mathrm{\β}1}=\frac{1}{2}{m}_1\sin {\mathrm{\θ}}_{1}T,\\ T_{01}=\frac{T,}{2}-T_{\mathrm{\α}1}-T_{\mathrm{\β}1}\\ T_{\mathrm{\α}2}=\frac{1}{2}{m}_2\sin (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_2)T,\\ T_{\mathrm{\β}2}=\frac{1}{2}{m}_2\sin {\mathrm{\θ}}_{2}T,\\ T_{02}=\frac{T,}{2}-T_{\mathrm{\α}2}-T_{\mathrm{\β}2}\end{array}\right.---\left(2\right)$

According to weber the balance principle amplitude of calculating the voltage vector of inverter A be

$U_{r1}=U_{\mathrm{\α}1}{d}_{\mathrm{\α}1}\cos {\mathrm{\θ}}_1+U_{\mathrm{\β}1}{d}_{\mathrm{\β}1}\cos (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_1)---\left(3\right)$

Wherein

$U_{\mathrm{\α}1}=U_{\mathrm{\β}1}=\frac{2}{3}{U}_d,$ $U_{r1}=\frac{1}{\sqrt{3}}{U}_{0L1}---\left(4\right)$

The line voltage magnitude that formula (1) (4) substitution formula (3) is calculated inverter A output is

$U_{0L1}=\sqrt{3}\·[\frac{2}{3}{U}_d\·\frac{1}{2}{m}_1\sin (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_1)\·\cos {\mathrm{\θ}}_1+\frac{2}{3}{U}_d\·\frac{1}{2}{m}_1\sin {\mathrm{\θ}}_1\cos (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_1)]$

$=\frac{1}{2}{m}_1{U}_d---\left(5\right)$

The amplitude that in like manner can calculate the line voltage of inverter B output is

$U_{0L2}=\frac{1}{2}{m}_2{U}_d---\left(6\right)$

Voltage utilization is defined as the ratio of inverter output line voltage fundametal compoment amplitude and DC bus-bar voltage amplitude:

$p=\frac{U_{\mathrm{\α}1}}{U_d}---\left(7\right)$

Therefore, can calculate and adopt the voltage utilization of conventional P WM modulation strategy five leg inverters to be

$\left\{\begin{array}{c}{p}_1=\frac{1}{2}{m}_1\\ p_2=\frac{1}{2}{m}_2\end{array}\right.---\left(8\right)$

Voltage utilization direct ratio and the modulation ratio of five leg inverters are because 0＜m ₁≤ 1,0＜m ₂≤ 1, so voltage utilization is up to 50%.

Summary of the invention

The present invention is directed to that there is the low shortcoming of voltage utilization in five leg inverter conventional modulated strategies in the background technology, a kind of new modulation strategy is proposed, five leg inverter voltage vectors are optimized adjustment, and the overlapping time of zero vector that takes full advantage of five leg inverters modulates the idle inverter of script; This method comprises the steps:

Step (1) analyzes interior two inverters each voltage vector separately of one-period in the five leg inverter PWM modulation strategies, the action time of each voltage vector, and overlapping time of the zero vector of two inverters;

Step (2), at above-mentioned zero vector in the overlapping time, to in half sampling period originally all idle inverter modulate, according to the resultant vector position of this inverter in this sampling period, adopt the SVPWM technology to choose voltage vector and insert above-mentioned zero vector respectively in the overlapping time;

Step (3) is drawn interior new voltage vector distribution map of sampling period of five leg inverters according to the voltage vector in selected voltage vector in the step (2) and the step (1);

Step (4), duty ratio and the action time of calculating each voltage vector in the described new voltage vector distribution map;

Step (5) is according to generating action time of each voltage vector described in the step (4) five leg inverter pwm control signals.

Further, step (1) is specially: two inverters are respectively inverter A and inverter B, in preceding half sampling period, inverter A are carried out the SVPWM modulation, and inverter B is operated in zero vector state, and each voltage vector of inverter A is α ₁, zero vector and β ₁, be respectively T its action time _{α 1}, T ₀₁And T _{β 1}, α wherein ₁And β ₁Be respectively inverter A synthesising output voltage vector u in preceding half sampling period _R1Two nonzero voltage space vectors, T ₀₁Be the SVPWM modulation zero vector action time of inverter A in preceding half sampling period, at T ₀₁Interior inverter A and inverter B all are in zero vector during this period of time, do not have the output of line voltage; In back half sampling period, inverter B is carried out the SVPWM modulation, inverter A is operated in zero vector state, and each voltage vector of inverter B is α ₂, zero vector and β ₂, be respectively R its action time _{α 2}, T ₀₂And T _{β 2}, α wherein ₂And β ₂Be respectively the half interior inverter B synthesising output voltage vector u of sampling period in back _R2Two nonzero voltage space vectors, T ₀₂Be the SVPWM modulation zero vector action time of the half interior inverter B of sampling period in back, at T ₀₂Interior inverter A and inverter B all are in zero vector during this period of time, do not have the output of line voltage; Therefore two overlapping times of inverter zero vector are T in the one-period ₀₁And T ₀₂

Further, step (2) is specially: in the overlapping time T of zero vector ₀₁In, the inverter B that is in zero vector in preceding half sampling period is originally carried out the SVPWM modulation, adopt the SVPWM technology to choose voltage vector, i.e. zero vector, α ₂, and β ₂Insert T ₀₁In; In the overlapping time T of zero vector ₀₂In, the inverter A that is in zero vector in back half sampling period is originally carried out the SVPWM modulation, adopt the SVPWM technology to choose voltage vector, i.e. zero vector, α ₁And β ₁Insert T ₀₂In.

The present invention is directed to five leg inverter conventional modulated strategies in the background technology and have the shortcoming of output line voltage waveform difference, a kind of new modulation strategy is proposed, distribution redistributes and has reduced the number of times that a plurality of brachium pontis of the zero vector moment move simultaneously to voltage vector, the reverse voltage of line voltage is significantly reduced, effectively reduce high order harmonic component and improve the quality of power supply.This method comprises the steps:

Step (1) is analyzed when on off state switches in each sampling period in all sector combination the number of times that a plurality of brachium pontis move simultaneously and number;

Step (2) is listed effective on off state of five leg inverters, sets up finite state machine;

Step (3) is chosen corresponding voltage vector according to the position of two inverter resultant vectors;

Step (4) to selected voltage vector in the step (3), is followed the state transitions trajectory diagram that each on off state switches the principle drafting finite state machine of the switch motion of having only a brachium pontis;

The voltage vector distribution map is adjusted and drawn to step (5) according to the state transitions trajectory diagram to a sampling period voltage vector distribution;

Step (6), duty ratio and the action time of each voltage vector in the calculating voltage vector distribution map;

Step (7) is according to generating action time of described each voltage vector of step (6) five leg inverter pwm control signals.

Description of drawings

Fig. 1 is the topological structure that the present invention's five leg inverters drive two asynchronous machine systems.

Fig. 2 is five leg inverter sampling period division tables.

Fig. 3 is the synthetic schematic diagram of the voltage vector of the corresponding inverter of two motors.

Fig. 4 is conventional modulated strategy voltage vector distribution map.

Fig. 5 is the modulation strategy voltage vector distribution map that improves voltage utilization.

Fig. 6 is inverter A and inverter B resultant vector when being in I sector and V sector respectively, and voltage vector distributes and on off state figure under the conventional modulated strategy.

Fig. 7 is inverter A and inverter B resultant vector when being in I sector and V sector respectively, improves that voltage vector distributes and on off state figure under the modulator approach of voltage utilization.

Fig. 8 is the effective workshation state tables of five leg inverters.

Fig. 9 is inverter A and inverter B resultant vector when all being in the I sector, the state transitions trajectory diagram of finite state machine.

Figure 10 is inverter A and inverter B voltage vector when all being in the I sector, and the method voltage vector of optimizing the line voltage waveform distributes and on off state figure.

Embodiment

1. improve five leg inverter voltage utilization modulator approaches

Technical problem to be solved by this invention is, a kind of control strategy that is applicable to foregoing circuit is provided, and effectively improves the voltage utilization of five leg inverters, improves the load capacity of five leg inverters.The present invention is that to solve the problems of the technologies described above the technical scheme that adopts be to utilize inverter A and overlapping time of inverter B zero vector in the conventional modulated strategy, and the inverter that is in zero vector is originally carried out the SVPWM modulation.

As can be seen in preceding half sampling period, inverter A carries out the SVPWM modulation in the five traditional leg inverter PWM modulation strategies shown in Figure 4, and inverter B remains zero vector.Inverter A work can be divided into α ₁, β ₁With three sections of zero vectors.T ₀₁The SVPWM modulation zero vector action time of corresponding inverter A, d ₀₁Be its duty ratio, during this period of time inverter A and inverter B all are in zero vector, do not have the output of line voltage.This moment, inverter A was in the principle of zero vector state when then inverter B worked in the satisfied five leg inverter modulation strategies, can not cause interference to the normal modulation of inverter A if inverter B is modulated.Therefore, can utilize the overlapping time T of this section zero vector ₀₁B modulates to inverter.In like manner, can be at T in half sampling period of back ₀₂In time period inverter A is modulated.Inverter A has made T than conventional modulated strategy multiplex (MUX) respectively with inverter B in the sampling period ₀₁With T ₀₂Time, therefore the line voltage of output can be improved.

Fig. 5 is that the five leg inverter modulator approach voltage vectors that improve voltage utilization distribute.α ₁, β ₁, α ₂, β ₂Selection principle and traditional PWM modulation strategy in full accord, α ₁And β ₁Be respectively synthetic inverter A output voltage vector u in preceding half sampling period _R1Two nonzero voltage space vectors.α ₂And β ₂Be respectively the back and synthesize inverter B output voltage vector u in half sampling period _R2Two nonzero voltage space vectors.The duty ratio of each vector in a sampling period can calculate according to the SVPWM modulation principle.D among the figure _{α 1}, d _{β 1}And d ₀₁Be respectively the corresponding α of inverter A in preceding half sampling period ₁, β ₁Duty ratio with zero vector; And

Be respectively corresponding d ₀₁The duty ratio of the voltage vector of inverter B in time.d _{α 2}, d _{β 2}And d ₀₂Be respectively the half corresponding α of interior inverter B of sampling period in back ₂, β ₂Duty ratio with zero vector.

And Be respectively corresponding d ₀₂The duty ratio of the voltage vector of inverter A in time.

d _{α 1}, d _{β 1}, d _{α 2}, and d _{β 2}Duty ratio calculate can be referring to formula (1), action time can be referring to formula (2).It is as follows that application SVPWM modulation principle calculates all the other each section voltage vector duty ratio computing formula:

$\left\{\begin{array}{c}{d}_{\mathrm{\α}2}^{\′}=\frac{1}{2}{m}_2\sin (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_2)d_{01}\\ =\frac{1}{2}{m}_2\sin (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_2)[1-m_1\sin ({\mathrm{\θ}}_1+\frac{\mathrm{\π}}{3})]\\ d_{\mathrm{\β}2}^{\′}=\frac{1}{2}{m}_2\sin {\mathrm{\θ}}_2{d}_{01}\\ =\frac{1}{2}{m}_2\sin {\mathrm{\θ}}_2[1-m_1\sin ({\mathrm{\θ}}_1+\frac{\mathrm{\π}}{3})]\\ d_{02}^{\′}=d_{01}-d_{\mathrm{\α}2}^{\′}-d_{\mathrm{\β}2}^{\′}\\ d_{\mathrm{\α}1}^{\′}=\frac{1}{2}{m}_1\sin (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_1)d_{02}\\ =\frac{1}{2}{m}_1\sin (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_1)[1-m_2\sin ({\mathrm{\θ}}_2+\frac{\mathrm{\π}}{3})]\\ d_{\mathrm{\β}1}^{\′}=\frac{1}{2}{m}_1\sin {\mathrm{\θ}}_1{d}_{02}\\ =\frac{1}{2}{m}_1\sin {\mathrm{\θ}}_1[1-m_2\sin ({\mathrm{\θ}}_2+\frac{\mathrm{\π}}{3})]\\ d_{01}^{\′}=d_{02}-d_{\mathrm{\α}1}^{\′}-d_{\mathrm{\β}1}^{\′}\end{array}\right.---\left(9\right)$

In the formula, m ₁With m ₂Be respectively the modulation ratio of inverter A and inverter B, θ ₁With θ ₂Be respectively the sector angle of inverter A and inverter B.Calculating the action time that can further calculate each voltage vector after the duty ratio of each voltage vector is:

$\left\{\begin{array}{c}{T}_{\mathrm{\α}2}^{\′}=\frac{1}{2}{m}_2\sin (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_2)d_{01}T,\\ =\frac{1}{2}{m}_2\sin (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_2)[1-m_1\sin ({\mathrm{\θ}}_1+\frac{\mathrm{\π}}{3})]T,\\ T_{\mathrm{\β}2}^{\′}=\frac{1}{2}{m}_2\sin {\mathrm{\θ}}_2{d}_{01}T,\\ =\frac{1}{2}{m}_2\sin {\mathrm{\θ}}_2[1-m_1\sin ({\mathrm{\θ}}_1+\frac{\mathrm{\π}}{3})]T,\\ T_{02}^{\′}=T_{01}-T_{\mathrm{\α}2}^{\′}-T_{\mathrm{\β}2}^{\′}\\ T_{\mathrm{\α}1}^{\′}=\frac{1}{2}{m}_1\sin (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_1)d_{02}T,\\ =\frac{1}{2}{m}_1\sin (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_1)[1-m_2\sin ({\mathrm{\θ}}_2+\frac{\mathrm{\π}}{3})]T,\\ T_{\mathrm{\β}1}^{\′}=\frac{1}{2}{m}_1\sin {\mathrm{\θ}}_1{d}_{02}T,\\ =\frac{1}{2}{m}_1\sin {\mathrm{\θ}}_1[1-m_2\sin ({\mathrm{\θ}}_2+\frac{\mathrm{\π}}{3})]T,\\ T_{01}^{\′}=T_{02}-T_{\mathrm{\α}1}^{\′}-T_{\mathrm{\β}1}^{\′}\end{array}\right.---\left(10\right)$

According to weber the balance principle amplitude of calculating the voltage vector of inverter A be:

$U_{r1}=U_{\mathrm{\α}}{d}_{\mathrm{\α}1}\cos {\mathrm{\θ}}_1+U_{\mathrm{\β}}{d}_{\mathrm{\β}1}\cos (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_1)+U_{\mathrm{\α}}{d}_{\mathrm{\α}1}^{\′}\cos {\mathrm{\θ}}_1+U_{\mathrm{\β}}{d}_{\mathrm{\β}1}^{\′}\cos (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_1)---\left(11\right)$

The amplitude that composite type (1), (9), (11) and formula (4) arrangement can get inverter A output line voltage is:

$U_{0L1}=\sqrt{3}[U_{\mathrm{\α}}{d}_{\mathrm{\α}1}\cos {\mathrm{\θ}}_1+U_{\mathrm{\β}}{d}_{\mathrm{\β}1}\cos (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_1)+U_{\mathrm{\α}}{d}_{\mathrm{\α}1}^{\′}\cos {\mathrm{\θ}}_1+U_{\mathrm{\β}}{d}_{\mathrm{\β}1}^{\′}\cos (\frac{\mathrm{\π}}{3}-{\mathrm{\θ}}_1)]$

$=\frac{1}{2}{m}_1{U}_d[2-m_2\sin ({\mathrm{\θ}}_2+\frac{\mathrm{\π}}{3})]---\left(12\right)$

Owing to try to achieve inverter A line voltage magnitude with sector angle θ ₂Variation and change, so line voltage is averaged, being in first sector with output voltage vector is that the amplitude that example is calculated inverter A output line voltage is:

$U_{0L1}=\frac{{\∫}_0^{\frac{\mathrm{\π}}{3}}\frac{1}{2}{m}_1{U}_d[2-m_2\sin ({\mathrm{\θ}}_2+\frac{\mathrm{\π}}{3})]d{\mathrm{\θ}}_2}{\frac{\mathrm{\π}}{3}}=\frac{1}{2}{m}_1{U}_d(2-\frac{3}{\mathrm{\π}}{m}_2)---\left(13\right)$

In like manner, can derive five leg inverter output line voltage vectors is in second to the 6th its amplitude of sector and is:

$\left\{\begin{array}{c}{U}_{0L1}=\frac{1}{2}{m}_1{U}_d(2-\frac{3}{\mathrm{\π}}{m}_2)\\ U_{0L2}=\frac{1}{2}{m}_2{U}_d(2-\frac{3}{\mathrm{\π}}{m}_1)\end{array}\right.---\left(14\right)$

Therefore, obtain adopting the voltage utilization of modulation strategy five leg inverters of proposition to be by formula (7):

$\left\{\begin{array}{c}{p}_1^{\′}=\frac{1}{2}{m}_1(2-\frac{3}{\mathrm{\π}}{m}_2)\\ p_2^{\′}=\frac{1}{2}{m}_2(2-\frac{3}{\mathrm{\π}}{m}_1)\end{array}\right.---\left(15\right)$

Motor adopts constant voltage and frequency ratio control among the present invention, so modulation ratio m direct ratio and inverter output frequency f, gets

$m=\frac{f}{50}---\left(16\right)$

Formula (16) substitution formula (8) can be tried to achieve the traditional PWM modulation strategy five leg inverter voltage utilizations of employing is:

$\left\{\begin{array}{c}{p}_1=\frac{f_1}{100}\\ p_2=\frac{f_2}{100}\end{array}\right.---\left(17\right)$

The voltage utilization that formula (16) substitution formula (15) can be tried to achieve five leg inverters under the PWM modulation strategy that adopts proposition is:

$\left\{\begin{array}{c}{p}_1^{\′}=\frac{f_1}{100}(2-\frac{{3f}_2}{50\mathrm{\π}})\\ p_2^{\′}=\frac{f_2}{100}(2-\frac{{3f}_1}{50\mathrm{\π}})\end{array}\right.---\left(18\right)$

Two kinds of modulation strategies raising degree that draws voltage utilization of comparing is:

$\left\{\begin{array}{c}{\mathrm{\Δp}}_1=p_1^{\′}-p_1=\frac{f_1}{100}(1-\frac{{3f}_2}{50\mathrm{\π}})\\ {\mathrm{\Δp}}_2=p_2^{\′}-p_2=\frac{f_2}{100}(1-\frac{{3f}_1}{50\mathrm{\π}})\end{array}\right.---\left(19\right)$

Δ p wherein ₁With Δ p ₂Be respectively the raising amount of inverter A and inverter B voltage utilization.

In real work was used, five leg inverters many times were used to drive two motors that stator frequency is identical, at this moment f ₁=f ₂, the voltage utilization that calculates five leg inverters according to formula (17) and formula (18) is:

$\left\{\begin{array}{c}{p}_1=p_2=\frac{f_1}{100}\\ p_1^{\′}=p_2^{\′}=\frac{f_1}{50}-\frac{{{3f}_1}^2}{5000\mathrm{\π}}\end{array}\right.---\left(20\right)$

The raising of voltage utilization

$\mathrm{\Δp}=p_1^{\′}-p_1=-\frac{{{3f}_1}^2}{5000\mathrm{\π}}+\frac{f_1}{100}---\left(21\right)$

2. optimize the modulator approach of five leg inverter line voltage waveforms

Technical problem to be solved by this invention is, a kind of control method that is applicable to foregoing circuit is provided, and reduces the reverse voltage pulse of five leg inverter output line voltages effectively, optimizes the line voltage waveform.The present invention is that to solve the problems of the technologies described above the technical scheme that adopts be that voltage vector is redistributed, and the number of times that a plurality of switches move simultaneously when reducing on off state and switching is to suppress the reverse voltage pulse on the line voltage.

The principle that each diverter switch state can only have a switch motion is followed in the SVPWM specification requirement, reduces switching loss and suppresses reverse voltage pulse on the line voltage with this.This is that all there is certain time-delay in each switching device when opening or turn-off because of power electronic device and non-ideal switches device in the practical application, and time-delay length is not quite similar.In addition, control signal also was difficult to guarantee fully synchronously from the time that controller is transferred to each switching device.Because switch is asynchronous, when two or three brachium pontis move simultaneously on the line voltage of inverter output reverse voltage pulse can appear, cause torque pulsation and the electromagnetic interference of motor.

Five traditional leg inverter modulation strategies and improving in the modulation strategy of five leg inverter voltage utilizations, the switching of the each on off state particularly switching of zero vector all needs to move simultaneously to realize by the switch of a plurality of brachium pontis.Therefore when adopting above-mentioned modulation strategy, five leg inverters the potential pulse of mistake often occurs at the on off state switching instant, make the inverter output line voltage contain a large amount of reverse voltage pulse.

Fig. 6 is that an interior voltage vector of sampling period distributes and on off state in traditional five leg inverter PWM modulation strategies, and this moment, the voltage resultant vector of inverter A and inverter B laid respectively at I sector and V sector.As shown in Figure 6.As can be seen from the figure all have 3 switches to move simultaneously for inverter A and each sampling period of inverter B at the switching instant of zero vector, namely the situation that a plurality of switches move simultaneously can take place repeatedly in interior five leg inverters of sampling period.Voltage vector number in this modulation strategy in sampling period is less, in preceding half sampling period α is only arranged ₁And β ₁Two nonzero voltage space vectors only have α in half sampling week of back ₂And β ₂Therefore two nonzero voltage space vectors can't distribute the situation of avoiding 3 brachium pontis switches to move simultaneously by adjusting voltage vector, so reverse voltage pulse are difficult to overcome.

Fig. 7 is that the voltage vector that improves in the modulator approach of five leg inverter voltage utilizations in the sampling period distributes and on off state.This moment, the voltage resultant vector of inverter A and inverter B laid respectively at I sector and V sector.The as can be seen from the figure situation that still exists three switches to move simultaneously under this modulation strategy, therefore, the line voltage of inverter output is inevitable also to exist a large amount of reverse voltage pulse, brings significant damage to motor.For reducing the reverse voltage pulse of inverter output line voltage, need distribute to voltage vector and adjust.Because it is more that the voltage vector that comprises in sampling period in this modulation strategy is run off status quantity jointly, in forward and backward half sampling period α arranged all ₁, β ₁, α ₂And β ₂Therefore four nonzero voltage space vectors, the selection of zero vector is also more flexible, can consider to optimize the switch that reduces or suppress a plurality of brachium pontis and move simultaneously by the distribution of each voltage vector is adjusted.

According to the topological structure of five leg inverters as can be known, five leg inverters comprise 5 brachium pontis altogether 2 ⁵=32 kinds of on off states.Therefore the switching of the on off state of five leg inverters can be regarded one 2 as ⁵The finite state machine of dimension, the event that driving condition shifts is the switching of voltage vector.But circuit working can not travel through all states, but along certain bar orbiting motion of state space.According to the switching rule of five leg inverters, inverter circuit has only 14 kinds of effective operating states, as shown in Figure 8.The on off state of five leg inverters will be at I ₁～I ₁₄Switch between these 14 effective operating states.Therefore, the key of design is that control law in conjunction with five leg inverters is from I ₁～I ₁₄Select suitable operating state, satisfy the requirement of having only the switch motion of a brachium pontis when any on off state switches in the SVPWM technology.Simultaneously, five leg inverters can be worked normally, two motors all can safely and steadily run.

Improve in each switch periods of modulation strategy of five leg inverter voltage utilizations and have 10 operating states.Therefore need be from I ₁～I ₁₄The principle of picking out 10 corresponding with it operating states and the each state switch number of times minimum of basis reasonably distributes, and designs only state transitions trajectory diagram.

Fig. 9 is the state transitions trajectory diagram of finite state machine in the sampling period, and this moment, the voltage resultant vector of inverter A and inverter B all was positioned at the I sector.As can be seen, each state switching has only one to change from the state transitions trajectory diagram, and namely each state conversion all has only the switch of a brachium pontis to move for five leg inverters.This state transitions track meets in the SVPWM technology principle of each state switch number of times minimum, the situation of effectively having avoided the switch of a plurality of brachium pontis to move simultaneously.

Figure 10 is that the five leg inverter voltage vectors corresponding with Fig. 9 distribute and on off state.As can be seen from the figure all have only a switch to move for inverter A and the each state switching of inverter B, the state of two inverters switches all requirements of match state change over switch number of times minimum.

The output voltage vector position of every inverter is divided into 6 sectors, so there are 36 kinds of sector combination states in the output voltage vector position of five leg inverters.Under other each sector combination state, can adjust the optimization output voltage vector by above-mentioned improvement modulation strategy equally.But in some sector, owing to lack transition state, no matter which kind of adopts shift track, action when all can not avoid a plurality of switch fully, but the switch that adopts this modulation strategy can eliminate 3 brachium pontis fully moves simultaneously, and reduces the number of times that 2 brachium pontis switches move simultaneously as far as possible.Thereby reduce the reverse voltage pulse of output line voltage, suppress to avoid high-frequency harmonic distortion and electromagnetic interference, keep the stable operation of governing system.

Claims (4)

1. PWM modulator approach that improves five leg inverter voltage utilizations is characterized in that: five leg inverter voltage vectors are optimized adjustment, and the overlapping time of zero vector that takes full advantage of five leg inverters modulates idle inverter originally; This method comprises the steps:

Step (1) analyzes interior two inverters each voltage vector separately of one-period in the five leg inverter PWM modulation strategies, the action time of each voltage vector, and overlapping time of the zero vector of two inverters;

Step (2), at above-mentioned zero vector in the overlapping time, to in half sampling period originally all idle inverter modulate, according to the resultant vector position of this inverter in this sampling period, adopt the SVPWM technology to choose voltage vector and insert above-mentioned zero vector respectively in the overlapping time;

Step (3) is drawn interior new voltage vector distribution map of sampling period of five leg inverters according to the voltage vector in selected voltage vector in the step (2) and the step (1);

Step (4), duty ratio and the action time of calculating each voltage vector in the described new voltage vector distribution map;

Step (5) is according to generating action time of each voltage vector described in the step (4) five leg inverter pwm control signals.

2. the PWM modulator approach of raising five leg inverter voltage utilizations according to claim 1, it is characterized in that: step (1) is specially: two inverters are respectively inverter A and inverter B, in preceding half sampling period, inverter A is carried out the SVPWM modulation, inverter B is operated in zero vector state, and each voltage vector of inverter A is α ₁, zero vector and β ₁, be respectively T its action time _{α 1}, T ₀₁Sharp T _{β 1}, α wherein ₁And β ₁Be respectively inverter A synthesising output voltage vector u in preceding half sampling period _R1Two nonzero voltage space vectors, T ₀₁Be the SVPWM modulation zero vector action time of inverter A in preceding half sampling period, at T ₀₁Interior inverter A and inverter B all are in zero vector during this period of time, do not have the output of line voltage; In back half sampling period, inverter B is carried out the SVPWM modulation, inverter A is operated in zero vector state, and each voltage vector of inverter B is α ₂, zero vector and β ₂, be respectively T its action time _{α 2}, T ₀₂And T _{β 2}, α wherein ₂And β ₂Be respectively the half interior inverter B synthesising output voltage vector u of sampling period in back _R2Two nonzero voltage space vectors, T ₀₂Be the SVPWM modulation zero vector action time of the half interior inverter B of sampling period in back, at T ₀₂Interior inverter A and inverter B all are in zero vector during this period of time, do not have the output of line voltage; Therefore two overlapping times of inverter zero vector are T in the one-period ₀₁And T ₀₂

3. the PWM modulator approach of raising five leg inverter voltage utilizations according to claim 1, it is characterized in that: step (2) is specially: in the overlapping time T of zero vector ₀₁In, in preceding half sampling period originally all idle inverter B modulate, employing SVPWM technology is chosen voltage vector, i.e. zero vector, α ₂, and β ₂Insert T ₀₁In; In the overlapping time T of zero vector ₀₂In, to back originally in half sampling period all idle inverter A modulate, adopt the SVPWM technology to choose voltage vector, i.e. zero vector, α ₁And β ₁Insert T ₀₂In.

4. optimize the PWM modulator approach that five leg inverter line voltages are exported for one kind, it is characterized in that: the voltage vector to five leg inverters is arranged again, reduce the number of times that a plurality of switches of the zero vector moment move simultaneously, improve five leg inverter output line voltage waveform qualities, this method comprises the steps:

Step (1) is analyzed when on off state switches in each sampling period in all sector combination the number of times that a plurality of brachium pontis move simultaneously and number;

Step (2) is listed effective on off state of five leg inverters, sets up finite state machine;

Step (3) is chosen corresponding voltage vector according to the position of two inverter resultant vectors;

Step (4) to selected voltage vector in the step (3), is followed the state transitions trajectory diagram that each on off state switches the principle drafting finite state machine of the switch motion of having only a brachium pontis;

The voltage vector distribution map is adjusted and drawn to step (5) according to the state transitions trajectory diagram to a sampling period voltage vector distribution;

Step (6), duty ratio and the action time of each voltage vector in the calculating voltage vector distribution map;

Step (7) is according to generating action time of described each voltage vector of step (6) five leg inverter pwm control signals.

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