CN204231220U - The inverter that two-phase brachium pontis runs is proceeded to during tri-level single-phase-bridge arm fault - Google Patents

Abstract

Proceed to the inverter that two-phase brachium pontis runs during tri-level single-phase-bridge arm fault, belong to the inverter of three level fault two-phase operation.The DC side of this inverter connects the equal electric capacity of two capacitances; The normal brachium pontis of two-phase is in parallel, and each brachium pontis has four switching devices and two switches to be connected in series, equal reverse parallel connection diode on the switching device of each brachium pontis.Load side joint three phase alternating current motor, after a phase brachium pontis breaks down, excised by this phase brachium pontis, three phase alternating current motor accesses two normal brachium pontis mid points and DC bus capacitor mid point respectively; By the corresponding adjustment to space vector modulation algorithm (SVPWM), make it adapt to two bridge arm topologicals, inverter still can operate in a low voltage state, and can be implemented in three-level inverter single-phase brachium pontis when breaking down, and still can ensure motor rotation.

Description

The inverter that two-phase brachium pontis runs is proceeded to during tri-level single-phase-bridge arm fault

Technical field

The utility model relates to the inverter of three level fault two-phase operation, specifically proceeds to the inverter that two-phase brachium pontis runs during a kind of tri-level single-phase-bridge arm fault.

Background technology

In AC Motor Control system, inverter plays an important role in the entire system, maintains the running of motor.But in actual motion, the fault of inverter can cause output waveform to distort, and makes motor to run well.Relying on the industry of motor, such as mine hoist, the maintenance down that the fault of inverter causes can cause economic being badly damaged, more may threat to life safety.Therefore, needing to adopt an effective measure when making fault of converter still can maintain inverter output waveforms correctly, thus ensures the operation of motor.

From the eighties in 20th century, along with the development of Large Copacity high-voltage inverter, the advantage of multi-level frequency conversion device shows gradually, becomes the focus of motors transmission field.The basic circuit topology of the multi-electrical level inverter that people commonly use has three kinds: striding capacitance clamped multi-level inverter, cascade multilevel inverter, diode-clamped multi-electrical level inverter.

It is exactly the technology that pulse-width carries out modulating that PWM (Pulse Width Modulation) controls, and is used for obtaining required waveform equivalently.Space vector PWM (SVPWM) control strategy controls frequency converter according to frequency converter space voltage (electric current) vectors switching.Voltage space vector PWM control strategy is that Japanese scholars proposed for ac motor speed control by variable frequency in the eighties in 20th century, adopts the switching of inverter space voltage vector to obtain quasi-circular rotating magnetic field.SVPWM can improve the voltage utilization of voltage source inverter and the dynamic response performance of motor, can also reduce the torque pulsation of motor simultaneously.According to the movement locus of the flux linkage space vector that will follow the tracks of, select the switch form of inverter, make inverter export the voltage of suitable waveform, the general principle of Here it is SVPWM.

Summary of the invention

The purpose of this utility model proceeds to the inverter that two-phase brachium pontis runs when being to provide the tri-level single-phase-bridge arm fault that a kind of structure is simple, cost is low, reliability is high.

The purpose of this utility model is achieved in that adopted technical scheme is: the three-phase brachium pontis of this inverter has 12 switching devices, each brachium pontis has 4 switching devices and two switches are connected in series; Reverse parallel connection diode on each switching device, two switches are all connected to switching device from phase line; Main topology adopts diode clamp, and mains side is the electric capacity that two capacitances are equal; 4 switching devices of each brachium pontis are divided into 2 groups of two adjacent switch devices, and the tie point of interior two the adjacent switch devices of each group is connected to DC bus capacitor mid point respectively by clamping diode; DC side mid point is connected to by switch at the tie point of 2 groups of switching devices of each brachium pontis; After detecting that in three-level inverter A, B, C phase brachium pontis, a certain phase brachium pontis breaks down, this phase brachium pontis is excised, its output is directly accessed the midpoint of inverter, adopt the two-phase brachium pontis of non-faulting to replace three-phase brachium pontis to continue to run; By six clamping diode clampers, adjustment 3 level space vector modulation algorithm (SVPWM), can increase level number effectively, reduces voltage harmonic, output voltage electric current is exported close to sinusoidal three-phase more, still can operate in a low voltage state.

Under two bridge arm structures, load side joint three phase alternating current motor, three phase alternating current motor accesses two normal brachium pontis mid points and DC bus capacitor mid point respectively; Adopt space vector modulation algorithm (SVPWM), it is adjusted, makes it adapt to two bridge arm topologicals, when three-level inverter breaks down at single-phase brachium pontis, still can ensure motor rotation; Concrete steps are as follows:

(1) analyze the basic vector figure not having out of order three-level inverter to export, according to fault phase brachium pontis, basic vector is screened, basic vector figure new after obtaining fault;

(2) judge the position of reference vector after a failure in basic vector figure, according to voltage-second balance principle, basic vector is adjusted action time;

(3) determine the sequence of operation of basic vector, action time switching device is controlled in conjunction with vector.

Beneficial effect: owing to have employed such scheme, the equal electric capacity of two capacitances is connected in DC side, the normal brachium pontis of A, B two-phase is made up of four switching device anti-paralleled diodes respectively, 1,2 switching devices centres on every phase brachium pontis and the middle mid point being connected to DC side by clamping diode of 3,4 switching devices, directly connect DC side mid point after C phase brachium pontis failure removal; Load side joint three phase alternating current motor, three phase alternating current motor accesses two normal brachium pontis mid points and DC bus capacitor mid point respectively.

After detecting that in three-level inverter A, B, C phase brachium pontis, a certain phase brachium pontis breaks down, this phase brachium pontis is excised, its output is directly accessed the midpoint of inverter.The output of each brachium pontis of three-level inverter originally can export three kinds of level, is respectively P, O, N, and after fault phase output access mid point, output can only export O level.Traditional algorithm basic vector has 27 kinds, after fault, and because fault phase can only export O level, therefore basic vector reduces to 7 kinds, and zoning plan is as 5.Utilize this 7 basic vectors, by the adjustment to SVPWM modulation algorithm, can ensure to maintain output waveform sine under pressure-lowering condition.

When C phase brachium pontis fault, by C phase output terminal access three-level inverter mid point, A phase can be P, O, N with the output of B phase, and the output of C phase is O; The fault handling method of this inverter, structure is more simple, and implementation method is simple.

Accompanying drawing explanation

Fig. 1 is the three-level inverter topology figure that can excise fault brachium pontis.

Fig. 2 is the topological diagram that after C phase fault, the utility model adopts.

Fig. 3 is that A, B brachium pontis exports phase voltage state principle figure.

Fig. 4 is basic vector figure when not having fault.

Fig. 5 a is the basic vector figure after C phase fault.

Fig. 5 b is the se ctor partition figure after C phase fault.

Fig. 6 is the exploded view of the 3rd sector reference vector.

Embodiment

Below to being further described embodiment of the present utility model by reference to the accompanying drawings:

The three-phase brachium pontis of the utility model inverter has 12 switching devices, each brachium pontis has 4 switching devices and two switches are connected in series; Reverse parallel connection diode on each switching device, two switches are all connected to switching device from phase line; Main topology adopts diode clamp, and mains side is the electric capacity that two capacitances are equal; 4 switching devices of each brachium pontis are divided into 2 groups of two adjacent switch devices, and the tie point of interior two the adjacent switch devices of each group is connected to DC bus capacitor mid point respectively by clamping diode; DC side mid point is connected to by switch at the tie point of 2 groups of switching devices of each brachium pontis; After detecting that in three-level inverter A, B, C phase brachium pontis, a certain phase brachium pontis breaks down, this phase brachium pontis is excised, its output is directly accessed the midpoint of inverter, adopt the two-phase brachium pontis of non-faulting to replace three-phase brachium pontis to continue to run; By six clamping diode clampers, adjustment 3 level space vector modulation algorithm (SVPWM), can increase level number effectively, reduces voltage harmonic, output voltage electric current is exported close to sinusoidal three-phase more, still can operate in a low voltage state.

Under two bridge arm structures, load side joint three phase alternating current motor, three phase alternating current motor accesses two normal brachium pontis mid points and DC bus capacitor mid point respectively; Adopt space vector modulation algorithm (SVPWM), it is adjusted, makes it adapt to two bridge arm topologicals, when three-level inverter breaks down at single-phase brachium pontis, still can ensure motor rotation; Concrete steps are as follows:

(1) analyze the basic vector figure not having out of order three-level inverter to export, according to fault phase brachium pontis, basic vector is screened, basic vector figure new after obtaining fault;

(2) judge the position of reference vector after a failure in basic vector figure, according to voltage-second balance principle, basic vector is adjusted action time;

(3) determine the sequence of operation of basic vector, action time switching device is controlled in conjunction with vector.

Embodiment 1: as shown in Figure 1, for excising the main topology of diode neutral point clamp (NPC) the type three-level inverter of fault brachium pontis.The three-phase brachium pontis of inverter has 12 switching devices, each brachium pontis has 4 switching devices.Each switching device reverse parallel connection diode.Main topology adopts diode clamp, and mains side is the electric capacity that two capacitances are equal, is connected to DC bus capacitor mid point in the middle of each brachium pontis 1,2 switching device and in the middle of 3,4 switching devices respectively by diode.By six diode clamps, effectively can increase level number, reduce voltage harmonic, make output voltage electric current more close to sinusoidal.In Fig. 1, when three-level inverter normally runs, switch S ₁₁, S ₁₂, S ₂₁, S ₂₂, S ₃₁and S ₃₂be in closure state, switch S ₁₃, S ₂₃, S ₃₃be in off-state.

When the C phase brachium pontis of three-level inverter breaks down, by S ₃₁and S ₃₂switch disconnects to excise C phase brachium pontis, and by S ₃₃the closed C phase output terminal that makes of switch accesses DC side mid point.Like this, topological diagram can be converted into structure chart as shown in Figure 2, Fig. 2 is structure structure chart when the utility model one phase brachium pontis breaks down.

Detailed analysis is carried out below by this structure.

In three-level inverter topology as shown in Figure 2, A phase and B phase are the two-phase brachium pontis normally worked, and explain normal brachium pontis operation principle for A phase.

VT ₁₁, VT ₁₂, VT ₁₃and VT ₁₄be 4 IGBT device in A phase, according to the switch combination mode of following table, three kinds of phase voltage states can be obtained, be respectively U _d/ 2,0 and-U _d/ 2, three kinds of states can represent with P, O and N.

Table 1 three level brachium pontis Switch State Combination in Power Systems table

Phase voltage export P, O and N tri-kinds of state of switch states as shown in Figure 3:

(1) during P-state, VT ₁₁and VT ₁₂conducting, VT ₁₃and VT ₁₄turn off.In this case, A phase output terminal is exactly the anode being directly connected to DC bus.Definition O point is ground reference, then A phase output voltage is U _d/ 2, be positive voltage.

(2) during O state, VT ₁₂and VT ₁₃conducting, VT ₁₁and VT ₁₄turn off.In this case, A phase output terminal is exactly the mid point being directly connected to DC bus, is connected with the mid point of two electric capacity.Electric current is by diode VD ₁₅and VD ₁₂flow out, then A phase output voltage is 0, is no-voltage.

(3) during N state, VT ₁₃and VT ₁₄conducting, VT ₁₁and VT ₁₂turn off.In this case, A phase output terminal is exactly the negative terminal being directly connected to DC bus, then A phase output voltage is-U _d/ 2, be negative voltage.

In like manner, B phase is also the same analytical method.According to Fig. 2, can find out that C phase directly accesses mid point, the state that therefore C phase exports only has O state.

First analyze basic vector when three-level inverter does not break down.

Owing to not having fault, A phase, B phase and C phase can produce three kinds of different level, combine with the level of three-phase, can obtain 19 basic voltage vectors.

The three-phase synthesis space vector of voltage of three level can represent with following formula:

u _s＝u _a+ρu _b+ρ ²u _c(1)

Wherein, for phasor operator; u _sit is stator space voltage vector; u _a, u _band u _cthree-phase voltage respectively.

If DC terminal voltage is U _d, after electric capacity, the output voltage of each brachium pontis has three kinds of possibility: U _d/ 2,0 and-U _d/ 2.The amplitude of each basic vector can by calculating, and computational methods can be carried out with reference to formula below:

Definition switching variable S _a, S _band S _c, represent the output state of A phase brachium pontis, B phase brachium pontis and C phase brachium pontis respectively, so, the voltage of each phase can be expressed as:

$u_a=\frac{1}{2}{U}_d{S}_a,u_b=\frac{1}{2}{U}_d{S}_b,u_c=\frac{1}{2}{U}_d{S}_c---\left(2\right)$

Wherein, when xth exports positive level mutually, S _x=1; When xth exports zero level mutually, S _x=0; When xth exports negative level mutually, S _x=-1.(x is a, b or c).

Employing amplitude is constant, and getting coefficient is 2/3, can show that space voltage vector is:

$u_K=\frac{2}{3}\×\frac{1}{2}{U}_d(S_a+{\mathrm{\ρS}}_b+{\mathrm{\ρ}}^2{S}_c)=\frac{1}{6}{U}_d[({2S}_a-S_b-S_c)+j\sqrt{3}(S_b-S_c)]---\left(3\right)$

Wherein, K is basic vector number.

Just can obtain the amplitude of 19 basic voltage vectors according to this formula, can polar plot be obtained, as shown in Figure 4.

According to the difference of vector magnitude, these 19 kinds of basic voltage vectors can be classified as: long vector, middle vector, small vector and zero vector.The Classifying Sum form of three level voltage vector is as follows.Above for there is no the three-level inverter analysis under failure condition.

Table 2 three level voltage vector Classifying Sum table

When C phase breaks down, after changing topology, because the output of C phase can only be O, operable vector only has 9 kinds, as following table.As shown in Figure 5 a, be the polar plot of these 9 basic vectors.Remove two middle vector NPO and PNO, orthohexagonal polar plot 5b can be obtained.Can find out, new hexagonal region diminishes.In order to obtain sinusoidal waveform, the voltage of output also will diminish thereupon.

Voltage vector summary sheet after table 3 fault

After C phase fault, space vector u _semploying amplitude is constant, and getting coefficient is 2/3, then inverter output voltage space vector can be expressed as:

$u_S=\frac{2}{3}(u_a+{\mathrm{\ρu}}_b+{\mathrm{\ρ}}^2{u}_c)---\left(4\right)$

Can find out from following table and have six nonzero voltage space vectors, due to | u _a|=U _d/ 2, | u _b|=U _d/ 2, | u _c|=0, then its mould is | u _s|=U _d/ 3 (U _dfor DC side voltage of converter); A Zero voltage vector is u ₀(000).New polar plot as shown in Figure 5 b.Reference vector U _refcan synthesize with adjacent basic vector, hypothetical reference vector u in III district, is then by u according to polar plot this vector known ₀, u ₄, u ₆synthesis.

Seven kinds of on off states of table 4 inverter

There is the analysis result of polar plot, needed to improve SVPWM modulation algorithm accordingly.

First the region judging reference vector is needed, with reference to vector U _refdecompose on α β coordinate system, so just can obtain U _αand U _β.If three variables A, B and C.If region decision variable is BS, according to BS=A+2B+4C, the position in region can be calculated.The corresponding relation in region as shown in Figure 5 b.

$\left\{\begin{array}{cccc}{u}_{\mathrm{\β}}>0& A=1& \mathrm{else}& A=0\\ \sqrt{3}{u}_{\mathrm{\α}}-u_{\mathrm{\β}}>0& B=1& \mathrm{else}& B=0\\ -\sqrt{3}{u}_{\mathrm{\α}}-u_{\mathrm{\β}}>0& C=1& \mathrm{else}& C=0\end{array}\right.---\left(5\right)$

After sector is determined, reference vector can utilize two basic vector synthesis in sector borders.After resolution of vectors, adopt voltage-second balance principle can calculate the action time of respective vectors, for the III sector shown in Fig. 6, by two basic vectors to α β axial projection, Ying You:

α axle: $u_{\mathrm{\α}}T=\left|u_4\right|T_4+\frac{1}{2}\left|u_6\right|T_6---\left(6\right)$

β axle: $u_{\mathrm{\β}}T=\frac{\sqrt{3}}{2}{u}_6{T}_6---\left(7\right)$

In formula, T _ifor corresponding vector u _iaction time (i=0 ~ 7); T is the sampling period, by the mould analyzing known basic vector is | u _s|=U _d/ 3, therefore in formula | u ₄|=| u ₆|=U _d/ 3, bring above formula into and can solve the corresponding time.The method for solving of vector action time in other intervals is also like this, sums up and obtains three basic time variables below.X, Y, Z and each sector vector T action time ₁, T ₂corresponding relation as shown in the table.The action time of zero vector can use formula T ₃=T-T ₁-T ₂calculate.

$\begin{array}{ccc}X=\frac{2\sqrt{3}{u}_{\mathrm{\β}}T}{u_d}& Y=\frac{(\sqrt{3}{u}_{\mathrm{\β}}+{3u}_{\mathrm{\α}})\×T}{u_d}& Z=\frac{(\sqrt{3}{u}_{\mathrm{\β}}-{3u}_{\mathrm{\α}})\×T}{u_d}\end{array}---\left(8\right)$

Table 5T ₁, T ₂with X, the mapping table of Y

Then, the vector order of action determining each region is needed.Vector change order observes a principle, and being exactly, when changing voltage vector each time, can only have a brachium pontis transition state in three brachium pontis.State Z can be avoided like this to suddenly change the problem brought.Following table is the vector state race-card set up according to mentioned above principle.Wherein, the corresponding brachium pontis of N, O, P difference exports as low level, zero level and high level.Analyze basic vector, in conjunction with the principle switching vector order, the SVPWM of five-part form can be selected.Owing to only having a brachium pontis action in order to during satisfied each change voltage vector, subregion does not use zero vector starting, but when area transformation, still can ensure to only have a brachium pontis action at every turn, meet design principle.

Table 6 vector state order of action table

Vector state order of action combines basic vector T action time calculated ₁, T ₂, T ₃, can distribute action time the basic vector of each section in five-part form.Time devided modulation table is as follows:

Table 7 basic vector allocation table action time

The level state of brachium pontis can correspond to the on off state of switching device on brachium pontis, because only have A phase brachium pontis and B phase brachium pontis to have switching device, C phase brachium pontis directly exports O state, therefore can be determined the on off state of A phase and 8 switching devices of B phase brachium pontis by following table.In table, the level state of each brachium pontis represents with N, O, P, and corresponding negative level, zero level and positive level, represent switching device G on each brachium pontis with 1 and 0 respectively ₁, G ₂, G ₃, G ₄turn on and off.The signal of the switching device of correspondence is inputted in topology of the present utility model, can sine wave output be controlled.

Table 8 on off state is corresponding with level state to be shown

Be more than analysis during C phase fault, in like manner, if fault phase is A phase, then by S ₁₁, S ₁₂switch disconnects to excise A phase brachium pontis, by S ₁₃closing makes A phase access DC side mid point; If fault phase is B phase, then by S ₂₁, S ₂₂switch disconnects to excise B phase brachium pontis, and by S ₂₃closing makes B phase access DC side mid point.Both of these case also needs to change accordingly SVPWM algorithm, and the method for change is consistent with the analytical method of C phase fault.

Claims (1)

1. proceed to the inverter that two-phase brachium pontis runs during tri-level single-phase-bridge arm fault, it is characterized in that: the three-phase brachium pontis of this inverter has 12 switching devices each brachium pontis having 4 switching devices and two switches are connected in series; Reverse parallel connection diode on each switching device, two switches are all connected to switching device from phase line; Main topology adopts diode clamp, and mains side is the electric capacity that two capacitances are equal; 4 switching devices of each brachium pontis are divided into 2 groups of two adjacent switch devices, and the tie point of interior two the adjacent switch devices of each group is connected to DC bus capacitor mid point respectively by clamping diode; DC side mid point is connected to by switch at the tie point of 2 groups of switching devices of each brachium pontis; After detecting that in three-level inverter A, B, C phase brachium pontis, a certain phase brachium pontis breaks down, this phase brachium pontis is excised, its output is directly accessed the midpoint of inverter, adopt the two-phase brachium pontis of non-faulting to replace three-phase brachium pontis to continue to run; Obtain four clamping diode clampers by healthy phases, adjustment 3 level space vector modulation algorithm, effectively can maintain level number, reduce voltage harmonic, output voltage electric current is exported close to sinusoidal three-phase, still can operate in a low voltage state.