CN104597370A - State observer-based detection method of open-circuit fault of IGBT (insulated gate bipolar transistor) of MMC (modular multilevel converter) - Google Patents

Abstract

The invention relates to the field of fault detection of power electronic and flexible HVDC (high voltage direct current), discloses a state observer-based detection method of an open-circuit fault of an IGBT (insulated gate bipolar transistor) of an MMC (modular multilevel converter) and aims to quickly diagnose reason and position of the open-circuit fault of the IGBT of the MMC. The state observer-based detection method includes as an error of an estimation value and a test value of bridge arm circulation excesses a threshold value for the moment of DeltaT1, judging that the fault occurs; comparing estimation values and actual values of the bridge arm current and output current and judging the bridge arm which the fault occurs to and fault type; monitoring voltage of capacitors of submodules, and in case that the voltage of the capacitor of one submodule is higher than the voltage threshold value for the moment of DeltaT2, judging that the fault occurs to the corresponding IGBT of the submodule. In this way, the state observer is provided for the output current and circulation of the MMC, and the submodule which the fault occurs is accurately positioned.

Description

Based on the detection method of the modularization multi-level converter IGBT open fault of state observer

Technical field

The present invention relates to Power Electronic Technique, flexible DC power transmission field of fault detection, be specifically related to a kind of detection method of the modularization multi-level converter Neutron module IGBT open fault based on state observer.

Background technology

Modularization multi-level converter (modular multilevel converter, MMC) obtain the extensive concern of people owing to having the plurality of advantages such as very high conversion efficiency, extremely low harmonic wave of output voltage content, very little wave filter volume, modularization feature, installation and maintenance are easy, make it be very suitable for the occasion of the high pressure high-power power conversion such as flexible DC power transmission.

The topological structure of modularization multi-level converter is that identical submodule unit is stacking forms by several, and the power component in submodule adopts insulated gate bipolar transistor (Insulated gate bipolar transistor, IGBT) usually.Owing to often adopting up to a hundred submodules in modularization multi-level converter in practical application, thus IGBT becomes the element of the fault that its most probable occurs.The fault of IGBT can classify as two classes: short trouble and open fault.Although the harm of IGBT short trouble is comparatively large, detection and the defencive function of perfect short trouble in the integrated drive of current IGBT, are all equipped with, by this IGBT quick closedown in several microseconds that can occur in fault.But the open fault of IGBT then often can keep not being found for a long time.For modularization multi-level converter, if the IGBT in a submodule there occurs open fault, the output voltage current waveform of whole transverter will be caused to distort, even can cause other more serious faults such as overvoltage, overcurrent.

Therefore, when IGBT open fault occurs certain submodule in modularization multi-level converter, quick diagnosis must have the generation of this fault, while, accurately can orient the submodule that breaks down and by its bypass, ensure the stable operation of other normal modules.Such technical scheme is not provided in prior art.

Summary of the invention

The object of this invention is to provide a kind of detection method detection method of IGBT open fault (in a kind of modularization multi-level converter) of the modularization multi-level converter IGBT open fault based on state observer, with for IGBT open fault contingent in MMC, quick diagnosis can have the generation of this fault, can accurately orient the position of breaking down simultaneously.

The present invention solves the problems of the technologies described above the technical scheme taked to be:

The detection method of IGBT open fault in a kind of modularization multi-level converter, this MMC transverter each comprise upper and lower two brachium pontis mutually, each brachium pontis is in series by the submodule that inductor is identical with several structures, each submodule comprises a half-bridge power unit and a capacitor, and each half-bridge power unit forms S by two IGBT ₁, S ₂; Described IGBT open fault detection method is as follows:

(1) the bridge arm current i of every mutually upper and lower brachium pontis, is detected respectively _uwith i _l, and calculate output current i _owith brachium pontis circulation i _c:

i _o＝i _u-i _l

$i_c=\frac{1}{2}(i_u+i_l)$

(2), according to output current and brachium pontis circulation, the dynamic circuit equation of modularization multi-level converter is built:

$2L\frac{{\mathrm{di}}_c}{\mathrm{dt}}+2R{i}_c=U_{\mathrm{dc}}-u_u-u_l$

$L\frac{{\mathrm{di}}_o}{\mathrm{dt}}+{\mathrm{Ri}}_o=u_l-u_u-2u_o$

In formula, U _dcrepresent DC voltage, u _lfor lower bridge arm voltage, u _ufor upper bridge arm voltage, u _ofor output voltage, R represents bridge arm equivalent resistance, and L represents brachium pontis inductance value;

(3), by dynamic circuit equation be organized into matrix form, obtain:

$\left\{\begin{array}{c}\stackrel{\·}{x}=\mathrm{Ax}+\mathrm{Bu}+\mathrm{De}\\ y=\mathrm{Cx}\end{array}\right.$

Wherein,

$x=y=\left(\begin{array}{c}{i}_c\\ i_o\end{array}\right),u=\left(\begin{array}{c}{u}_l\\ u_u\end{array}\right),e=\left(\begin{array}{c}{U}_{\mathrm{dc}}\\ u_o\end{array}\right),$

$A=\left(\begin{array}{cc}-\frac{R}{L}& 0\\ 0& -\frac{R}{L}\end{array}\right),B=\left(\begin{array}{cc}-\frac{1}{2L}& -\frac{1}{2L}\\ \frac{1}{L}& -\frac{1}{L}\end{array}\right),C=\left(\begin{array}{cc}1& 0\\ 0& 1\end{array}\right),D=\left(\begin{array}{cc}\frac{1}{2L}& 0\\ 0& -\frac{2}{L}\end{array}\right);$

(4), according to the output current i that obtains in the dynamic circuit equation of step (3) and step (1) _owith brachium pontis circulation i _c, build the state observer of output current and brachium pontis circulation respectively, obtain the estimated value of output current and brachium pontis circulation:

$\left\{\begin{array}{c}\stackrel{\·}{\hat{x}}=A\hat{x}+\mathrm{Bu}+\mathrm{De}+K(y-\hat{y})\\ \hat{y}=C\hat{x}\end{array}\right.$

Wherein, " ^ " means the estimated value of this physical quantity, and K is enlargement factor matrix, and its value is:

$K=\left(\begin{array}{cc}k& 0\\ 0& k\end{array}\right)$

(5) when the estimated value of brachium pontis circulation and error detection value exceed threshold value I _thand continue Δ T ₁time, then can failure judgement occur;

(6), after detecting that fault occurs, compare the magnitude relationship between the estimated value of bridge arm current and output current and actual value respectively, fault can be determined and occur in which brachium pontis, and the type (S of fault IGBT ₁or S ₂);

(7) voltage of each submodule capacitor is monitored, if certain submodule capacitor is higher than voltage threshold U _th, and continue Δ T ₂time, then the IGBT that finally can locate respective type in this submodule there occurs fault;

After the open fault of IGBT being detected, by this fault submodule bypass, ensure that the work of all the other submodules is unaffected.

In step (4), the effect of state observer to calculate the estimated value of output current and brachium pontis circulation, to be used for comparing with actual current value.

Time delay Δ T in step (5) ₁object be prevent from causing erroneous judgement because of interference.Under the prerequisite guaranteeing the generation of accurate failure judgement, Δ T ₁should be little as far as possible.

Time delay Δ T in step (7) ₂object be prevent from causing erroneous judgement because of interference.Under the prerequisite guaranteeing accurate localizing faults, Δ T ₂should be little as far as possible.

Time delay Δ T in step (5) ₁value is 1 ~ 3 millisecond.

Time delay Δ T in step (7) ₂value is 5 ~ 10 milliseconds.

The invention has the beneficial effects as follows:

In the methods of the invention, state observer is built to the output current of modularization multi-level converter and circulation.

When there is IGBT open fault, the result generation difference that the estimated value of state observer will detect with reality, according to brachium pontis and the type at this difference condition and diagnosable place of being out of order.And by monitoring the voltage of each submodule capacitor of this brachium pontis further, can accurately orient the submodule broken down.

The invention has the advantages that and do not need extra fault detection device is installed, by means of only the generation can judging IGBT open fault to the Detection Information of bridge arm current and submodule capacitor voltage, and the submodule broken down can be oriented.

Accompanying drawing explanation

Fig. 1 is the structural drawing of Modular multilevel converter; In figure, SM represents submodule;

Fig. 2 is the structural drawing of each submodule in Modular multilevel converter;

Fig. 3 is Modular multilevel converter submodule IGBT open fault schematic diagram, and in figure, (a) is S ₁open fault, (b) is S ₂open fault;

Fig. 4 is the equivalent circuit diagram of a circuitry phase in Modular multilevel converter;

Fig. 5 is the process flow diagram of open fault detection method in the present invention;

Fig. 6 is the process flow diagram of fault submodule location in the present invention;

Fig. 7 is an embodiment oscillogram of the present invention, and in figure: the abscissa representing time of a, ordinate represents output current and estimated value thereof; The abscissa representing time of b, ordinate represents brachium pontis circulation and estimated value thereof; The abscissa representing time of c, ordinate represents each submodule capacitor voltage of brachium pontis and estimated value thereof.

Embodiment

1 ~ 6 describe the specific embodiment of the present invention in detail by reference to the accompanying drawings, but the present invention does not limit by described instantiation:

The topological structure of three-phase modular multilevel inverter as shown in Figure 1.Wherein each is made up of upper and lower two brachium pontis, and each brachium pontis is formed by several submodules are stacking, as shown in Figure 2.Two IGBT (S are contained by each submodule ₁with S ₂) and a capacitor C, the open fault of submodule may have S ₁fault and S ₂fault two kinds of situations, as shown in Figure 3.In the control block diagram of open fault detection method of the present invention, concrete steps are as follows:

(1) the bridge arm current i of every mutually upper and lower brachium pontis is detected respectively _uwith i _l, and calculate output current i _owith brachium pontis circulation i _c:

i _o＝i _u-i _l

$i_c=\frac{1}{2}(i_u+i_l)$

(2) according to the one phase equivalent circuit model shown in Fig. 4, the dynamic circuit equation of modularization multi-level converter is built:

$2L\frac{{\mathrm{di}}_c}{\mathrm{dt}}+2R{i}_c=U_{\mathrm{dc}}-u_u-u_l$

$L\frac{{\mathrm{di}}_o}{\mathrm{dt}}+{\mathrm{Ri}}_o=u_l-u_u-2u_o$

In formula, U _dcrepresent DC voltage, u _lfor lower bridge arm voltage, u _ufor upper bridge arm voltage, u _ofor output voltage, R represents bridge arm equivalent resistance, and L represents brachium pontis inductance value.

(3) dynamic circuit equation is organized into matrix form, obtains:

$\left\{\begin{array}{c}\stackrel{\·}{x}=\mathrm{Ax}+\mathrm{Bu}+\mathrm{De}\\ y=\mathrm{Cx}\end{array}\right.$

Wherein,

$x=y=\left(\begin{array}{c}{i}_c\\ i_o\end{array}\right),u=\left(\begin{array}{c}{u}_l\\ u_u\end{array}\right),e=\left(\begin{array}{c}{U}_{\mathrm{dc}}\\ u_o\end{array}\right),$

$A=\left(\begin{array}{cc}-\frac{R}{L}& 0\\ 0& -\frac{R}{L}\end{array}\right),B=\left(\begin{array}{cc}-\frac{1}{2L}& -\frac{1}{2L}\\ \frac{1}{L}& -\frac{1}{L}\end{array}\right),C=\left(\begin{array}{cc}1& 0\\ 0& 1\end{array}\right),D=\left(\begin{array}{cc}\frac{1}{2L}& 0\\ 0& -\frac{2}{L}\end{array}\right).$

(4) according to the output current i that obtains in the dynamic circuit equation of step (3) and step (1) _owith brachium pontis circulation i _c, build the state observer of output current and brachium pontis circulation respectively, obtain the estimated value of output current and brachium pontis circulation:

$\left\{\begin{array}{c}\stackrel{\·}{\hat{x}}=A\hat{x}+\mathrm{Bu}+\mathrm{De}+K(y-\hat{y})\\ \hat{y}=C\hat{x}\end{array}\right.$

Wherein, " ^ " means the estimated value of this physical quantity, and K is enlargement factor matrix, and its value is:

$K=\left(\begin{array}{cc}k& 0\\ 0& k\end{array}\right)$

(5) as shown in Figure 5, when the estimated value of brachium pontis circulation and error detection value exceed threshold value I _thand continue Δ T ₁time, then can failure judgement occur;

(6), after detecting that fault occurs, compare the magnitude relationship between the estimated value of bridge arm current and output current and actual value respectively, according to table 1, fault can be determined and occur in which brachium pontis, and the type (S of fault IGBT ₁or S ₂).

Table 1 abort situation judges table

(7) as shown in Figure 6, the voltage of each submodule capacitor is monitored, if certain submodule capacitor is higher than voltage threshold U _th, and continue Δ T ₂time, then the IGBT that finally can locate respective type in this submodule there occurs fault.

(8) by this fault submodule bypass, ensure that the work of all the other submodules is unaffected.

What more than enumerate is only a specific embodiment of the present invention; the invention is not restricted to above embodiment; many distortion can also be had, all distortion that those of ordinary skill in the art can directly derive from content disclosed by the invention or associate, all should protection scope of the present invention be thought.

Embodiment or experiment

As Fig. 1 to Fig. 7, described modularization multi-level converter each comprise upper and lower two brachium pontis mutually, each brachium pontis is in series by the submodule that inductor is identical with several structures, each submodule comprises a half-bridge power unit and a capacitor, each half-bridge power unit contains two IGBT, is designated as S respectively ₁, S ₂; The topological structure of three-phase modular multilevel inverter as shown in Figure 1; Testing process is as follows,

The bridge arm current i of the every mutually upper and lower brachium pontis of step one, respectively detection _uwith i _l, and calculate output current i _owith brachium pontis circulation i _c:

i _o＝i _u-i _l

$i_c=\frac{1}{2}(i_u+i_l)$

Step 2, foundation output current and brachium pontis circulation, build the dynamic circuit equation of modularization multi-level converter:

$2L\frac{{\mathrm{di}}_c}{\mathrm{dt}}+2R{i}_c=U_{\mathrm{dc}}-u_u-u_l$

$L\frac{{\mathrm{di}}_o}{\mathrm{dt}}+{\mathrm{Ri}}_o=u_l-u_u-2u_o$

In formula, U _dcrepresent DC voltage, u _lfor lower bridge arm voltage, u _ufor upper bridge arm voltage, u _ofor output voltage, R represents bridge arm equivalent resistance, and L represents brachium pontis inductance value;

Step 3, described dynamic circuit equation is organized into matrix form, obtains:

$\left\{\begin{array}{c}\stackrel{\·}{x}=\mathrm{Ax}+\mathrm{Bu}+\mathrm{De}\\ y=\mathrm{Cx}\end{array}\right.$

Wherein,

$x=y=\left(\begin{array}{c}{i}_c\\ i_o\end{array}\right),u=\left(\begin{array}{c}{u}_l\\ u_u\end{array}\right),e=\left(\begin{array}{c}{U}_{\mathrm{dc}}\\ u_o\end{array}\right),$

$A=\left(\begin{array}{cc}-\frac{R}{L}& 0\\ 0& -\frac{R}{L}\end{array}\right),B=\left(\begin{array}{cc}-\frac{1}{2L}& -\frac{1}{2L}\\ \frac{1}{L}& -\frac{1}{L}\end{array}\right),C=\left(\begin{array}{cc}1& 0\\ 0& 1\end{array}\right),D=\left(\begin{array}{cc}\frac{1}{2L}& 0\\ 0& -\frac{2}{L}\end{array}\right).$

Step 4, according to the output current i obtained in the dynamic circuit equation of step 3 and step one _owith brachium pontis circulation i _c, build the state observer of output current and brachium pontis circulation respectively, obtain the estimated value of output current and brachium pontis circulation:

$\left\{\begin{array}{c}\stackrel{\·}{\hat{x}}=A\hat{x}+\mathrm{Bu}+\mathrm{De}+K(y-\hat{y})\\ \hat{y}=C\hat{x}\end{array}\right.$

Wherein, " ^ " means the estimated value of this physical quantity, and K is enlargement factor matrix, and its value is:

$K=\left(\begin{array}{cc}k& 0\\ 0& k\end{array}\right)$

State observer for calculating the estimated value of output current and brachium pontis circulation, to be used for comparing with actual current value;

Step 5, exceed threshold value I when the estimated value of brachium pontis circulation and error detection value _thand continue Δ T ₁the time of=5, then can failure judgement occur;

Step 6, detect that fault occurs after, compare the magnitude relationship between the estimated value of bridge arm current and output current and actual value respectively, fault can be determined and occur in which brachium pontis, and the type (S of fault IGBT ₁or S ₂);

Step 7, monitor the voltage of each submodule capacitor, if certain submodule capacitor is higher than voltage threshold U _th, and continue Δ T ₂the time of=7, then the IGBT that finally can locate respective type in this submodule there occurs fault; By this fault submodule bypass, ensure that the work of all the other submodules is unaffected.

Utilize said method detection module multilevel converter open fault, Fig. 7 is the oscillogram being depicted as the detection of modularization multi-level converter open fault, wherein engraves certain submodule in brachium pontis when 0.032s and there occurs S1 open fault.Figure is visible thus, and after fault occurs, output current and brachium pontis circulation all higher than estimated value, therefore will can judge this fault type according to table 1.In addition, the capacitance voltage of the submodule that breaks down can raise fast, then can orient this submodule.

Claims (5)

1. the detection method based on the modularization multi-level converter IGBT open fault of state observer, described modularization multi-level converter each comprise upper and lower two brachium pontis mutually, each brachium pontis is in series by the submodule that inductor is identical with several structures, each submodule comprises a half-bridge power unit and a capacitor, each half-bridge power unit contains two IGBT, is designated as S respectively ₁, S ₂;

It is characterized in that: the implementation procedure of described method is:

The bridge arm current i of the every mutually upper and lower brachium pontis of step one, respectively detection _uwith i _l, and calculate output current i _owith brachium pontis circulation i _c:

i _o＝i _u-i _l

$i_c=\frac{1}{2}(i_u+i_l)$

Step 2, foundation output current and brachium pontis circulation, build the dynamic circuit equation of modularization multi-level converter:

$\frac{{\mathrm{di}}_c}{\mathrm{dt}}{2\mathrm{Ri}}_c=U_{\mathrm{dc}}-u_u-u_l$

$L\frac{{\mathrm{di}}_o}{\mathrm{dt}}+{\mathrm{Ri}}_o=u_l-u_u-2u_o$

In formula, U _dcrepresent DC voltage, u _lfor lower bridge arm voltage, u _ufor upper bridge arm voltage, u _ofor output voltage, R represents bridge arm equivalent resistance, and L represents brachium pontis inductance value;

Step 3, described dynamic circuit equation is organized into matrix form, obtains:

$\left\{\begin{array}{c}\stackrel{\·}{x}=\mathrm{Ax}+\mathrm{Bu}+\mathrm{De}\\ y=\mathrm{Cx}\end{array}\right.$

Wherein,

$x=y=\left(\begin{array}{c}{i}_c\\ i_o\end{array}\right),u=\left(\begin{array}{c}{u}_l\\ u_u\end{array}\right),e=\left(\begin{array}{c}{U}_{\mathrm{dc}}\\ u_o\end{array}\right),$

$A=\left(\begin{array}{cc}-\frac{R}{L}& 0\\ 0& -\frac{R}{L}\end{array}\right),B=\left(\begin{array}{cc}-\frac{1}{2L}& -\frac{1}{2L}\\ \frac{1}{L}& -\frac{1}{L}\end{array}\right),C=\left(\begin{array}{cc}1& 0\\ 0& 1\end{array}\right),D=\left(\begin{array}{cc}\frac{1}{2L}& 0\\ 0& -\frac{2}{L}\end{array}\right).$

Step 4, according to the output current i obtained in the dynamic circuit equation of step 3 and step one _owith brachium pontis circulation i _c, build the state observer of output current and brachium pontis circulation respectively, obtain the estimated value of output current and brachium pontis circulation:

$\left\{\begin{array}{c}\stackrel{\stackrel{\·}{^}}{x}=A\hat{x}+\mathrm{Bu}+\mathrm{De}+K(y-\hat{y})\\ \hat{y}=C\hat{x}\end{array}\right.$

Wherein, " ^ " means the estimated value of this physical quantity, and K is enlargement factor matrix, and its value is:

$K=\left(\begin{array}{cc}k& 0\\ 0& k\end{array}\right)$

In formula, K is enlargement factor;

Step 5, exceed threshold value I when the estimated value of brachium pontis circulation and error detection value _thand continue Δ T ₁time, then can failure judgement occur;

Step 6, detect that fault occurs after, compare the magnitude relationship between the estimated value of bridge arm current and output current and actual value respectively, fault can be determined and occur in which brachium pontis, and the type (S of fault IGBT ₁or S ₂);

Step 7, monitor the voltage of each submodule capacitor, if certain submodule capacitor is higher than voltage threshold U _th, and continue Δ T ₂time, then the IGBT that finally can locate respective type in this submodule there occurs fault.

2. the detection method of a kind of modularization multi-level converter IGBT open fault based on state observer according to claim 1, it is characterized in that, described method also comprises: step 8, by this fault submodule bypass, ensure that the work of all the other submodules is unaffected.

3. the detection method of a kind of modularization multi-level converter IGBT open fault based on state observer according to claim 1 and 2, it is characterized in that, in step 4, state observer is for calculating the estimated value of output current and brachium pontis circulation, to be used for comparing with actual current value.

4. the detection method of a kind of modularization multi-level converter IGBT open fault based on state observer according to claim 4, is characterized in that, time delay Δ T in step 5 ₁value is 1 ~ 3 millisecond.

5. the detection method of a kind of modularization multi-level converter IGBT open fault based on state observer according to claim 5, is characterized in that, time delay Δ T in step 7 ₂value is 5 ~ 10 milliseconds.