CN103869208B - The three-phase inverter open fault detection method of phase redundancy fault-tolerant architecture - Google Patents

Abstract

The invention discloses the three-phase inverter open fault detection method of a kind of phase redundancy fault-tolerant architecture, expect that voltage is normalized the detection variable d obtaining three-phase expectation voltage initially with three-phase_n, and expect that according to three-phase the mean value calculation of the absolute value of voltage obtains detection variable a_n, by detection variable d_nWith detection variable a_nThreshold value k_mAnd k_dJudge to obtain indicating fault D_nAnd A_n, according to indicating fault D_nAnd A_nThe switching tube of Search and Orientation generation open fault in fault location table one.For fault location table one exists the fault of three kinds of likelihood of failure, it is possible to carry out substitution method by the 4th brachium pontis of the brachium pontis redundancy by determining the switching tube place that open fault occurs and carry out fault location further.The present invention is applied to the three-phase inverter open fault detection in electric vehicle drive system, it is possible to achieve maximum 27 kinds of open faults detections, and faults-tolerant control and troubleshooting for system provide accurate foundation.

Description

The three-phase inverter open fault detection method of phase redundancy fault-tolerant architecture

Technical field

The invention belongs to three-phase inverter fault detection technique field, more specifically say, relate to the three-phase inverter open fault detection method of a kind of phase redundancy fault-tolerant architecture.

Background technology

In recent years, voltage source inverter the motor driven systems powered obtains extensive application on electric automobile, but inverter therein but very easily breaks down.In order to improve the safety and reliability of electric automobile, it is necessary to the fault of inverter is carried out effective detection, location and isolation in real time, and takes faults-tolerant control.

In order to not reduce systematic function, currently used most commonly used be three-phase inverter adopt phase redundancy fault-tolerant architecture.Fig. 1 is the three-phase inverter schematic diagram of phase redundancy fault-tolerant architecture.As shown in Figure 1, in the three-phase inverter of phase redundancy fault-tolerant architecture, six switching tube composition three-phase inverters of T1～T6, T7, T8 form the 4th brachium pontis 11 of redundancy, for three bidirectional thyristors 12 of isolated fault phase, it is used for switching three bidirectional thyristors 13 of the 4th brachium pontis.During three-phase inverter normal operation, the 4th brachium pontis is not involved in work；When breaking down, take over fault phase with the 4th brachium pontis 11 and work on.Fig. 2 is based on the system block diagram of the motor drive controller of phase redundancy fault-tolerant architecture.As shown in Figure 2, motor drive controller based on phase redundancy fault-tolerant architecture includes, vector control module 21, SVPWM (SpaceVectorPulseWidthModulation, space vector pulse width modulation) modulation module 22, phase redundancy Fault tolerant inverter 23, motor 24, velocity sensor 25, current sensor 26 and open fault detection module 27.

The premise realizing faults-tolerant control is that fault of converter is detected.At present; substantial amounts of substantive work is had been carried out for inverter switching device tube short circuit fault; and the open fault of switching tube does not obtain due attention; because open fault can't cause after occurring that system is shut down at once; but it may result in the secondary failure of other inverter assemblies, finally bring the maintenance cost of great number to system.

For the open fault of inverter switching device pipe, one of research direction currently mainly is based on the fault detection method of voltage.Fig. 3 is based on the inverter switching device tube open circuit fault detection method schematic diagram of voltage.As it is shown on figure 3, the inverter switching device tube open circuit fault detection method based on voltage comprises the following steps:

(1) by the reference voltage u under biphase rest frame_α、u_β(generally expected rotating speed by motorTheoretical conversion obtains) it is converted into three-phase reference voltage u through Clark coordinate transform_a、u_b、u_c, by the expectation voltage under biphase rest frame(expected rotating speed by vector control module according to motorMotor actual speedMotor three-phase current obtains) it is converted into three-phase expectation voltage through Clark coordinate transform

$\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{cc}1& 0\\ -\frac{1}{2}& \frac{\sqrt{3}}{2}\\ -\frac{1}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{u}_{\mathrm{\α}}\\ u_{\mathrm{\β}}\end{array}\right],\left[\begin{array}{c}{u}_a^{*}\\ u_b^{*}\\ u_c^{*}\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{cc}1& 0\\ -\frac{1}{2}& \frac{\sqrt{3}}{2}\\ -\frac{1}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{u}_{\mathrm{\α}}^{*}\\ u_{\mathrm{\β}}^{*}\end{array}\right]$

(2) open fault detection variable d is calculated_n:

First three-phase reference voltage and the difference of three-phase expectation voltage are calculated:

$e_n=u_n-u_n^{*}$

Wherein, n ∈ { a, b, c}；

The impact brought to get rid of load to change, adopts DC bus-bar voltage to be normalized, and finally averaging obtains detection variable:

$d_n=<\frac{e_n}{V_{DC}}>$

Under normal circumstances, < e in the cycle_n> ≈ 0, so d_n≈0.When fault of converter, the motor three-phase current of output can produce change, thus causing three-phase reference voltage and the poor e of three-phase expectation voltage_nProduce change, make the detection variable d in the cycle_nProduce change, therefore can pass through detection variable d_nValue carry out failure judgement.

(3) judge and position concrete open fault:

Table 1 is fault of converter judgement table.Wherein, k_dFor predetermined threshold value.

Open fault switching tube	da	db	dc
				T1	> kd
T2	<-kd
				T3		> kd
T4		<-kd
				T5			> kd
T6			<-kd

But the fault detection method being based on voltage has the disadvantage in that

(1) open fault of single switching transistor can only be detected and position, and multiple switching tubes occur open fault just helpless simultaneously；

(2) the reference voltage u under biphase rest frame required for_α、u_βGeneral control system needs independent calculating, therefore will increase amount of calculation；

(3) impact brought to open fault detection to eliminate load to change, the method adopts DC bus-bar voltage to be normalized, and this is accomplished by busbar voltage Acquisition Circuit, and part control system is added cost.

Summary of the invention

It is an object of the invention to overcome the deficiencies in the prior art, it is provided that the three-phase inverter open fault detection method of a kind of phase redundancy fault-tolerant architecture, it is possible to achieve 27 kinds of open fault detections, faults-tolerant control and troubleshooting for system provide accurate foundation.

For achieving the above object, the three-phase inverter open fault detection method of phase redundancy fault-tolerant architecture of the present invention, comprise the following steps:

S1: obtain expectation voltage from motor driven systems closed-loop control systemThen willIt is converted into three-phase expectation voltage through Clark coordinate transform

S2: calculate detection variable d_n:

$d_n=\frac{<u_n^{*}>}{<\left|u_n^{*}\right|>}$

Wherein,It is three-phase expectation voltageMeansigma methods,It is three-phase expectation voltageThe meansigma methods of absolute value；

S3: calculate detection variable a_n:

$a_a=\frac{2<\left|u_a^{*}\right|>}{<\left|u_b^{*}\right|>+<\left|u_c^{*}\right|>}$

$a_b=\frac{2<\left|u_b^{*}\right|>}{<\left|u_a^{*}\right|>+<\left|u_c^{*}\right|>}$

$a_c=\frac{2<\left|u_c^{*}\right|>}{<\left|u_a^{*}\right|>+<\left|u_b^{*}\right|>}$

S4: set detection variable d_nWith detection variable a_nThreshold value k_mAnd k_d, it is judged that obtain indicating fault D_nAnd A_n:

$D_n=\left\{\begin{array}{cc}N& d_n\&le;-k_m\\ 0& \left|d_n\right|<k_m\\ P& d_n\&GreaterEqual;k_m\end{array}\right.$

$A_n=\left\{\begin{array}{cc}H& a_n>k_d\\ L& a_n\&le;k_d\end{array}\right.$

S5: according to the indicating fault D obtained_nAnd A_nThe switching tube of Search and Orientation generation open fault in fault location table one.

Further, the fault that there are three kinds of likelihood of failure in fault location table one adopts following methods to carry out further fault location:

The 4th brachium pontis determining the brachium pontis redundancy at the switching tube place that open fault occurs is substituted, reacquires expectation voltage calculating and obtain indicating fault D '_n, switching tube according to the fault location table two Search and Orientation generation open fault comprising 12 kinds of open faults.

Initially with three-phase, the three-phase inverter open fault detection method of phase redundancy fault-tolerant architecture of the present invention, expects that voltage is normalized the detection variable d obtaining three-phase expectation voltage_n, and expect that according to three-phase the mean value calculation of the absolute value of voltage obtains detection variable a_n, by detection variable d_nWith detection variable a_nThreshold value k_mAnd k_dJudge to obtain indicating fault D_nAnd A_n, according to indicating fault D_nAnd A_nThe switching tube of Search and Orientation generation open fault in fault location table one.For fault location table one exists the fault of three kinds of likelihood of failure, it is possible to carry out substitution method by the 4th brachium pontis of the brachium pontis redundancy by determining the switching tube place that open fault occurs and carry out fault location further.

The method have the advantages that

(1) can orienting 27 kinds of open faults, faults-tolerant control or troubleshooting for system provide foundation more accurately；

(2) input quantity used in the present invention can directly obtain from driving control system for electric machine, therefore need not increase extra sensor or other hardware circuits；

(3) algorithm is simple, overall calculation amount is little；

(4) by the reasonable setting of detection variable threshold value, it is possible to the detection variable fluctuation that tolerance motor speed change or load change cause, it is to avoid fault misdescription.

Accompanying drawing explanation

Fig. 1 is the three-phase inverter schematic diagram of phase redundancy fault-tolerant architecture；

Fig. 2 is based on the system block diagram of the motor drive controller of phase redundancy fault-tolerant architecture；

Fig. 3 is based on the inverter switching device tube open circuit fault detection method schematic diagram of voltage；

Fig. 4 is the three-phase inverter open fault detection method schematic diagram of phase redundancy fault-tolerant architecture of the present invention；

Fig. 5 is the motor three-phase current of example 1, detection variable d_nAnd a_nOscillogram；

Fig. 6 is the motor three-phase current of example 2, detection variable d_nAnd a_nOscillogram；

Fig. 7 is motor three-phase current, detection variable d in motor speed change procedure_nAnd a_nOscillogram；

Fig. 8 is motor three-phase current, detection variable d in load change procedure_nAnd a_nOscillogram.

Detailed description of the invention

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described, in order to those skilled in the art is more fully understood that the present invention.Requiring particular attention is that, in the following description, when perhaps the detailed description of known function and design can desalinate the main contents of the present invention, these descriptions here will be left in the basket.

Embodiment

Fig. 4 is the three-phase inverter open fault detection method schematic diagram of phase redundancy fault-tolerant architecture of the present invention.As shown in Figure 4, the three-phase inverter open fault detection method of phase redundancy fault-tolerant architecture of the present invention comprises the following steps:

S1: obtain expectation voltage from motor driven systems closed-loop control systemThen willIt is converted into three-phase expectation voltage through Clark coordinate transform

S2: calculate detection variable d_n.Unlike the prior art, the present invention directly adopts three-phase expectation voltageThe meansigma methods of absolute valueBeing normalized, thus eliminating load to change the impact brought, computational methods are:

$d_n=\frac{<u_n^{*}>}{<\left|u_n^{*}\right|>}$

Wherein,It is three-phase expectation voltageMeansigma methods,It is three-phase expectation voltageThe meansigma methods of absolute value, computing formula is:

$\left(u_n^{*}\right)=\frac{w}{2\mathrm{\&pi;}}\underset{0}{\overset{\frac{2\mathrm{\&pi;}}{w}}{\&Integral;}}{u}_n^{*}dt$

$<\left|u_n^{*}\right|>=\frac{w}{2\mathrm{\&pi;}}\underset{0}{\overset{\frac{2\mathrm{\&pi;}}{w}}{\&Integral;}}\left|u_n^{*}\right|dt$

Wherein, w represents the stator current angular frequency of motor.

S3: in order to detect multiple switching tube open fault simultaneously, present invention also adds a new detection variable a_n:

$a_a=\frac{2<\left|u_a^{*}\right|>}{<\left|u_b^{*}\right|>+<\left|u_c^{*}\right|>}$

$a_b=\frac{2<\left|u_b^{*}\right|>}{<\left|u_a^{*}\right|>+<\left|u_c^{*}\right|>}$

$a_c=\frac{2<\left|u_c^{*}\right|>}{<\left|u_a^{*}\right|>+<\left|u_b^{*}\right|>}$

Under normal circumstances, in the cycleSo d_n≈ 0, a_n≈1。

S4: set detection variable d_nWith detection variable a_nThreshold value k_mAnd k_d, it is judged that obtain indicating fault D_nAnd A_n:

$D_n=\left\{\begin{array}{cc}N& d_n\&le;-k_m\\ 0& \left|d_n\right|<k_m\\ P& d_n\&GreaterEqual;k_m\end{array}\right.$

$A_n=\left\{\begin{array}{cc}H& a_n>k_d\\ L& a_n\&le;k_d\end{array}\right.$

In motor actual moving process, due to motor speed change or load change, detection variable d can be made_nWith detection variable a_nProduce certain fluctuation, therefore threshold value k_mAnd k_dSetting be required to tolerance normal fluctuation.

S5: according to the indicating fault D obtained_nAnd A_nThe switching tube of Search and Orientation generation open fault in fault location table one.Table 2 is fault location table one.

Table 2

Wherein, [Tx] represents switch transistor T x it may happen that open fault, it is also possible to normal；(Tx/Ty) representing in switch transistor T x and Ty and have at least an open fault occurs, x, y represent switching tube sequence number, and " " represents that this indicating fault can be arbitrary value, and namely no matter why this indicating fault is worth, and does not affect the judgement of this fault.

From fault location table one it can be seen that now according to indicating fault D_nAnd A_nCan orient 21 kinds of open faults, though have some cannot completely specified fault, but interpretable open fault quantity is far more than prior art.And the present invention can also adopt the phase redundancy fault-tolerant architecture that three-phase inversion becomes device further the fault (fault 10 to fault 15) that there are three kinds of likelihood of failure to be carried out fault location, namely the 4th brachium pontis utilizing redundancy substitutes the fault phase that open fault occurs, and again positions fault according to indicating fault.Method particularly includes:

The 4th brachium pontis determining the brachium pontis redundancy at the switching tube place that open fault occurs is substituted, reacquires expectation voltage calculating and obtain indicating fault D '_n.With fault 10:T1, T4 and T1, the T5& [T4] in fault location table one for example, for the failure condition that both is possible, it is possible to open fault occurs switch transistor T 1 certainly.Therefore the 4th brachium pontis is used to replace the brachium pontis (i.e. T1 and T2) at T1 place that three-phase inverter is reconstructed, may determine that after reconstruct that T1 and the T2 after replacing it is normal, so Resurvey data can obtain indicating fault, judge that T4 occurs open fault, T5 that open fault occurs or open fault occurs T4 and T5 according to fault location table two simultaneously.The switching tube quantity of open fault is occurred to reduce due in now three-phase inverter, it is only necessary to adopt an indicating fault D '_nCan judging fault, therefore fault location table two is greatly simplified compared to fault location table one.Table 3 is fault location table two.

Fault sequence number	The switching tube of open fault	D′a	D′b	D′c
					1	T1	P	0	0
2	T2	N	0	0
					3	T3	0	P	0
4	T4	0	N	0
					5	T5	0	0	P 6 -->
6	T6	0	0	N
					7	T1,T4	P	N	—
8	T2,T3	N	P	—
					9	T1,T6	P	—	N
10	T2,T5	N	—	P
					11	T3,T6	—	P	N
12	T4,T5	—	N	P

Table 3

Visible, occur the fault phase of open fault to re-start fault location by utilizing the 4th brachium pontis of redundancy to substitute, it is possible to fault 10 to the fault 16 in fault location table one is positioned further, thus realizing amounting to the location of 27 kinds of open faults.

The fault location effectiveness of the present invention is described with several instantiations below.

Example 1:

Ac three-phase asynchronous motor rated power 1.1kW, rated speed 1390rpm, nominal torque 7.6Nm, rated current 2.89A, load torque is the nominal load of 50%.Detection variable threshold value k is set_m=0.08, k_d=0.93.Fig. 5 is the motor three-phase current of example 1, detection variable d_nAnd a_nOscillogram.As it is shown in figure 5, this example 1 arranges three-phase inverter 3 faults occur: during time t=1.6s, open fault occurs T2；During t=1.8s, there is open fault in T1 and T2 simultaneously；During t=2s, there is open fault in T1, T2 and T4 simultaneously.

A) t=1.4～1.6s, as it is shown in figure 5, motor three-phase current is the sine wave of symmetry, d_n≈ 0, a_n≈ 1, inverter normal operation, indicating fault D_a=D_b=D_c=0, A_a=A_b=A_c=H, does not have switching tube generation open fault as seen according to fault location table one, and three-phase inverter is working properly；

B) t=1.6～1.8s, as it is shown in figure 5, negative half-wave occurs in phase current Ia, when t=1.641s, detection variable d_a≤-0.08, | d_b| < 0.08, | d_c| < 0.08, a_a> 0.93, a_b> 0.93, a_c> 0.93；Indicating fault D can be obtained_a=N, D_b=0, D_c=0, A_a=A_b=A_c=H, according to fault location table one, orients switch transistor T 2 and open fault occurs；

C) t=1.8～2s, as it is shown in figure 5, phase current Ia is close to zero, when t=1.828s, detection variable | d_a| < 0.08, | d_b| < 0.08, | d_c| < 0.08, a_a> 0.93, a_b≤ 0.93, a_c> 0.93；Indicating fault D can be obtained_a=D_b=D_c=0, A_a=H, A_b=L, A_c=H.According to fault location table one, orient switch transistor T 1 and open fault occurs T2 simultaneously；

D) t=2～2.2s, as it is shown in figure 5, phase current Ia close to zero, Ib occur that negative half-wave occur in positive half-wave, Ic, when t=2.041s, detection variable | d_a| < 0.08, d_b≤-0.08, d_c>=0.08, a_a> 0.93, a_b≤ 0.93, a_c> 0.93；So D_a=0, D_b=N, D_c=P, A_a=H, A_b=L, A_c=H.According to fault location table one, it is possible to orient switch transistor T 1, T2, and in T4 and T5, open fault occurs at least one simultaneously.

Example 2:

Ac three-phase asynchronous motor rated power 1.1kW, rated speed 1390rpm, nominal torque 7.6Nm, rated current 2.89A, load torque is the nominal load of 50%.Detection variable threshold value k is set_m=0.08, k_d=0.93.Fig. 6 is the motor three-phase current of example 2, detection variable d_nAnd a_nOscillogram.As shown in Figure 6, this example 1 arranges three-phase inverter 3 faults occur: during t=1.6s, open fault occurs T1；During t=1.8s, there is open fault in T1 and T4 simultaneously；During t=2s, there is open fault in T1, T4 and T5 simultaneously.

E) t=1.4～1.6s, as shown in Figure 6, motor three-phase current is the sine wave of symmetry, d_n≈ 0, a_n≈ 1, indicating fault D_a=D_b=D_c=0, A_a=A_b=A_c=H, does not have switching tube generation open fault as seen according to fault location table one, and three-phase inverter is working properly；

F) t=1.6～1.8s, as shown in Figure 6, there is negative half-wave in phase current Ia, when t=1.649s, detection variable d_a>=0.08, | d_b| < 0.08, | d_c| < 0.08, a_a> 0.93, a_b> 0.93, a_c> 0.93；So indicating fault D_a=P, D_b=0, D_c=0, A_a=A_b=A_c=H, according to fault location table one, orients switch transistor T 1 and open fault occurs；

G) t=1.8～2s, as shown in Figure 6, phase current Ia occurs that positive half-wave occur in the half-wave born, Ib, when t=1.827s, detection variable d_a>=0.08, d_b≤-0.08, | d_c| < 0.08, a_a> 0.93, a_b> 0.93, a_c> 0.93；So indicating fault D_a=P, D_b=N, D_c=0, A_a=A_b=A_c=H.According to fault location table one, it may be possible to T1, T4 or T1, T5 or T1, T4, there is open fault in T5 simultaneously.At this moment, it was determined that switch transistor T 1 there occurs fault certainly, utilizing the 4th brachium pontis to replace the brachium pontis at T1 place, then reconstruct inverter detects again.Now, only there is positive half-wave in phase current Ib, detection variable | d_a| < 0.08, d_b≤-0.08, | d_c| < 0.08, indicating fault D '_a=0, D '_b=N, D '_c=0, according to fault location table two, it may be determined that T4 there occurs open fault.Arrive this, it may be determined that be that open fault occurs switch transistor T 1, T4 simultaneously before.

H) t=2～2.2s, as shown in Figure 6, phase current Ia occurs that negative half-wave, Ib occur that negative half-wave occur in positive half-wave, Ic.Detection variable d_a>=0.08, d_b≤-0.08, | d_c| < 0.08, a_a> 0.93, a_b> 0.93, a_c> 0.93；So indicating fault D_a=P, D_b=N, D_c=0, A_a=A_b=A_c=H.According to fault location table one, it may be possible to T1, T4 or T1, T5 or T1, T4, there is open fault in T5 simultaneously.Likewise it is possible to it is confirmed that switch transistor T 1 there occurs fault certainly, replace the brachium pontis at T1 place hence with the 4th brachium pontis, then reconstruct inverter detects again.Now, there is positive half-wave in phase current Ib, and negative half-wave, detection variable d occurs in Ic_b≤-0.08, d_c>=0.08, indicating fault D '_b=N, D '_c=P, according to fault location table two, it may be determined that T4, T5 there occurs open fault simultaneously.Arrive this, it may be determined that being switch transistor T 1, T4, open fault occurs T5 simultaneously before.

In motor actual moving process, rotating speed or load can change, and the expectation voltage that vector control module obtains also can change.The present invention is based on expectation voltage to carry out fault detect, but the phenomenon of wrong report fault will not occur in motor speed change procedure or load change procedure.

Fig. 7 is motor three-phase current, detection variable d in motor speed change procedure_nAnd a_nOscillogram.As it is shown in fig. 7, t=1.2～1.4s, rotating speed is 1000rpm；T=1.5～1.6s, rotating speed becomes 1390rpm；T=1.8～2s, rotating speed becomes 1000rpm.And in whole rotation speed change process, although there is certain fluctuation in indicating fault, but will not deviation normal value even more than threshold value, the phenomenon of wrong report fault will not be produced.

Fig. 8 is motor three-phase current, detection variable d in load change procedure_nAnd a_nOscillogram.As shown in Figure 8, t=1～1.4s, system does not load, for Light Condition；T=1.4s, system is loaded into suddenly nominal load；T=1.8s, the unexpected variable load of system is Light Condition.In whole load change procedure, although indicating fault exists certain fluctuation, but will not deviation normal value even more than threshold value, the phenomenon of wrong report fault will not be produced.

Although above the illustrative detailed description of the invention of the present invention being described; so that those skilled in the art understand the present invention; it is to be understood that; the invention is not restricted to the scope of detailed description of the invention; to those skilled in the art; as long as various changes limit and in the spirit and scope of the present invention determined, these changes are apparent from, and all utilize the innovation and creation of present inventive concept all at the row of protection in appended claim.

Claims (4)

1. the three-phase inverter open fault detection method of a phase redundancy fault-tolerant architecture, it is characterised in that comprise the following steps:

S1: drive closed-loop control system from motor and obtain expectation voltageThen willIt is converted into three-phase expectation voltage through Clark coordinate transform

S2: calculate detection variable d_n:

Wherein, n ∈ a, b, c},It is three-phase expectation voltageMeansigma methods,It is three-phase expectation voltageThe meansigma methods of absolute value；

S3: calculate detection variable a_n:

S4: set detection variable d_nWith detection variable a_nThreshold value k_mAnd k_d, it is judged that obtain indicating fault D_nAnd A_n:

S5: according to the indicating fault D obtained_nAnd A_nThe switching tube of Search and Orientation generation open fault in fault location table one.

2. three-phase inverter open fault detection method according to claim 1, it is characterised in that the fault that there are three kinds of likelihood of failure in described fault location table one adopts following methods to position further:

The 4th brachium pontis determining the brachium pontis redundancy at the switching tube place that open fault occurs is substituted, reacquires expectation voltage calculating and obtain indicating fault D '_n, switching tube according to fault location table two Search and Orientation generation open fault.

3. three-phase inverter open fault detection method according to claim 1, it is characterised in that described three-phase expectation voltageMeansigma methodsThree-phase voltageThe meansigma methods of absolute valueComputing formula be:

Wherein, w represents the stator current angular frequency of motor.

4. three-phase inverter open fault detection method according to claim 1, it is characterised in that described detection variable threshold value k_m=0.08, k_d=0.93.