CN108761351B

CN108761351B - Three-phase rectifier open-circuit fault diagnosis method based on SVPWM sector number

Info

Publication number: CN108761351B
Application number: CN201810617759.2A
Authority: CN
Inventors: 邱颖宁; 孙超; 冯延晖; 秦伟; 黄凯
Original assignee: Nanjing University of Science and Technology
Current assignee: Nanjing University of Science and Technology
Priority date: 2018-06-15
Filing date: 2018-06-15
Publication date: 2020-06-09
Anticipated expiration: 2038-06-15
Also published as: CN108761351A

Abstract

The invention discloses a three-phase rectifier open-circuit fault diagnosis method based on SVPWM sector numbers, which extracts an abnormal sector number when a fault occurs from sector number signals of SVPWM by collecting the sector number signals of SVPWM, and realizes rectifier open-circuit fault detection and fault switch tube positioning by combining the corresponding relation between the sector number and each power switch tube. The invention can detect the open circuit fault of the rectifier in time and accurately position the single tube or the multiple tubes with the open circuit fault; in addition, the method is simple and easy to implement, has good dynamic performance, does not need additional hardware facilities and additional calculation methods, and has strong transportability.

Description

Three-phase rectifier open-circuit fault diagnosis method based on SVPWM sector number

Technical Field

The invention relates to a three-phase rectifier open-circuit fault diagnosis method based on SVPWM sector numbers, and belongs to rectifier open-circuit fault diagnosis technologies.

Background

With the development of power electronic technology, the three-phase PWM rectifier has the characteristics of sinusoidal input current, bidirectional energy flow, adjustable direct-current voltage and the like, and is widely applied to the fields of medium and high-power occasions such as offshore wind power generation, new energy electric vehicles and the like. In the reliability research of the wind power generation system, relevant research shows that the power rectifier is the most prone device to failure due to the long-time continuous operation of the power rectifier under the severe environment and the unreliability of the gate signals of the power rectifier. Power rectifier faults are classified as gate signal loss faults, short circuit faults, and open circuit faults. Gate loss of signal faults are generally intermittent and may result in short-circuit faults or open-circuit faults; the short-circuit fault can generate a current surge phenomenon, and a quick fuse is generally connected in series in a circuit, so that the short-circuit fault is changed into an open-circuit fault, and the damage to a system is reduced; although the open-circuit fault does not cause instantaneous damage to the system, the open-circuit fault causes problems such as three-phase current distortion and direct-current side voltage pulsation. Therefore, no matter which fault occurs to the power rectifier, the power rectifier is finally converted into an open-circuit fault, and the system is required to be capable of quickly and accurately detecting the open-circuit fault and positioning a fault switch tube.

Most of the existing power rectifier open-circuit fault diagnosis methods can only realize fault diagnosis under the condition of constant wind speed or stability, and have poor positioning effect on multi-tube faults, and the method can be divided into the following steps from the angle of detection variables: a diagnostic method based on a current amount and a diagnostic method based on a voltage amount. Although the diagnosis method based on the current amount does not need to add extra hardware equipment, the diagnosis method is greatly influenced by loads, and can not make better judgment on some small-current systems, so that the diagnosis method generally needs to be improved by an extra algorithm or a control method; voltage-based diagnostic methods, while able to react faster, typically require additional hardware facilities such as voltage sensors, increasing the cost and structural complexity of the system. Therefore, for the open-circuit fault of the power rectifier in a complex environment (such as in a wind power generation system), a new method needs to be developed, and the problems of poor dynamic performance, complex algorithm, large load influence, high hardware cost and the like of the existing diagnosis method are solved.

Disclosure of Invention

Aiming at the problems that the existing rectifier open-circuit fault diagnosis method can only detect single-tube faults, has poor dynamic performance, large calculation amount, high cost, large load influence and the like, the invention provides the three-phase rectifier open-circuit fault diagnosis method based on the SVPWM sector number, which reduces algorithm complexity and hardware cost, and improves the dynamic performance of diagnosis and the robustness to loads.

The technical solution for realizing the purpose of the invention is as follows: a three-phase rectifier open-circuit fault diagnosis method based on SVPWM sector numbers comprises the following steps:

step 1, collecting an N value (generated by a control algorithm for generating an IGBT gate signal) corresponding to the SVPWM sector number.

And 2, counting the continuous and unchangeable N values (1-6) to obtain a diagnosis variable.

And 3, judging whether the diagnosis variable exceeds a set threshold value, if so, setting the mark position corresponding to the N value to be 1, and otherwise, setting the mark position to be 0.

Step 4, repeating the steps 1-3 in a three-phase voltage fundamental wave period of system operation, determining an abnormal N value (1-6) through six zone bits when the system operates to a period, and using N^*Record (0-6, if N)^*Is zeroThen a fault free region is indicated, i.e., no flag position 1) and the diagnostic variables and flag bits are cleared.

Step 5, the abnormal N value (namely N) is obtained through the corresponding relation between the N value and the sector number^*Value) to an abnormal sector number (0-6, where 0 represents a no-fault region).

And 6, accurately positioning the single tube or the multiple tubes with the open-circuit fault through the corresponding relation table between the sector numbers and the power switch tubes. And entering the next system three-phase voltage fundamental wave period.

Compared with the prior art, the invention has the following remarkable advantages: 1) the detection variable is an N value corresponding to the sector number, and the N value is generated by a control algorithm for generating an IGBT gate signal by the system, so that an additional detection algorithm and additional hardware equipment are not needed; 2) the invention adopts a periodic diagnosis method, the dynamic tracking performance is better, and the running state of the power rectifier can be automatically updated in each period; 3) the invention only needs to process the acquired N value, so the fault positioning algorithm is very simple; 4) according to the corresponding relation among the N value, the sector number and the fault switch tube, the single-tube open-circuit fault and the multi-tube open-circuit fault can be accurately and quickly positioned.

Drawings

FIG. 1 is a side structure view of the direct drive permanent magnet synchronous wind power generation system of the present invention.

FIG. 2 is a block diagram of machine side control and fault diagnosis of the direct drive permanent magnet synchronous wind power generation system of the present invention.

FIG. 3 is a diagram of the basic space voltage vectors and sectors in the α, β two-phase stationary coordinate system of the present invention.

Fig. 4 is a flowchart of the open-circuit fault diagnosis method of the three-phase rectifier based on the SVPWM sector number.

FIG. 5 is a wind speed variation curve according to the present invention.

FIG. 6 is an N-valued image, abnormal N, of the present invention during normal operation 1 second ago^*The method comprises the following steps of (a) acquiring a waveform of an N value; (b) is an abnormal N-value curve (namely N) after being judged by a threshold value^*Value, 0 represents no abnormal N value); (c)is an abnormal sector number curve (0-6, 0 represents no abnormal sector number); (d) and the fault positioning result is obtained.

FIG. 7 is an N-value image and abnormal N value of the single-tube open circuit fault of the S1 switch tube at 1 second in the invention^*The method comprises the following steps of (a) acquiring a waveform of an N value; (b) is an abnormal N-value curve (namely N) after being judged by a threshold value^*Value, 0 represents no abnormal N value); (c) is an abnormal sector number curve (0-6, 0 represents no abnormal sector number); (d) and the fault positioning result is obtained.

FIG. 8 is an N-value image and abnormal N values of the switch tubes S1 and S3 in 2 seconds of the present invention when a multi-tube open circuit fault occurs^*The method comprises the following steps of (a) acquiring a waveform of an N value; (b) is an abnormal N-value curve (namely N) after being judged by a threshold value^*Value, 0 represents no abnormal N value); (c) is an abnormal sector number curve (0-6, 0 represents no abnormal sector number); (d) and the fault positioning result is obtained.

FIG. 9 shows that S1 and S3 recover normal operation in 3 seconds, and N value image and abnormal N occur when single tube open fault occurs in S5^*The method comprises the following steps of (a) acquiring a waveform of an N value; (b) is an abnormal N-value curve (namely N) after being judged by a threshold value^*Value, 0 represents no abnormal N value); (c) is an abnormal sector number curve (0-6, 0 represents no abnormal sector number); (d) and the fault positioning result is obtained.

FIG. 10 is an N-value image and abnormal N values of 4 seconds after all the switching tubes are restored to normal operation^*The method comprises the following steps of (a) acquiring a waveform of an N value; (b) is an abnormal N-value curve (namely N) after being judged by a threshold value^*Value, 0 represents no abnormal N value); (c) is an abnormal sector number curve (0-6, 0 represents no abnormal sector number); (d) and the fault positioning result is obtained.

The reference numbers in the figures illustrate: 6 power switch tubes in the S1-S6 three-phase PWM rectifier, 6 fly-wheel diodes in the D1-D6 three-phase PWM rectifier, 6 thermal fuses in the three-phase PWM rectifier F1-F6, and a filter capacitor on the direct current side C. Three-phase current i_a,i_b,i_cThree-phase current, v, generated for a permanent-magnet synchronous generator_wIs fromThe wind speed, ω_mFor the angular velocity, T, of a permanent-magnet synchronous generator_mTorque provided to the wind wheel, theta being the three-phase current electrical angle, i_d,i_qA given value of current under a dq two-phase rotating coordinate system,

is a current feedback value under a dq two-phase rotating coordinate system,

is a feedback value of the torque of the motor,

the target voltage is α, β two-phase stationary coordinate system.

Detailed description of the invention

The invention is further illustrated by the following examples in conjunction with the accompanying drawings.

FIG. 1 is a side structure diagram of a direct-drive permanent magnet synchronous wind power generation system, which considers that only a power switch tube has a fault and a default diode connected in anti-parallel with the power switch tube still works normally, FIG. 2 shows a side control and fault diagnosis block diagram of the direct-drive permanent magnet synchronous wind power generation system, and a target αβ plane voltage

Based on the above theory, the invention provides a three-phase rectifier open-circuit fault diagnosis method based on SVPWM sector numbers, which carries out fault diagnosis and positioning by detecting the N value corresponding to the sector numbers, and the flow is as shown in FIG. 4, the steps are as follows:

step 1, collecting N values corresponding to SVPWM sector numbers, wherein the N values are generated by a control algorithm for generating IGBT gate signals, and a part of SVPWM control algorithms for generating the N values are as follows:

a linear transformation is defined:

wherein U is_a、U_b、U_cThe motor control part measures the parameters of the three-phase voltage of the stator, so that extra hardware equipment is not required to be added for measuring the open-circuit fault diagnosis. Three symbolic functions are defined A, B, C, taking 1 or 0. When U1>When 0, A is 1, otherwise, it is 0; when U2>When 0, B is 1, otherwise, B is 0; when U3>When 0, C is 1, otherwise, it is 0. Thus, 6 states can be combined (the case where ABC is 1 or 0 at the same time does not exist), and the expression defining the value of N is:

N＝A+2B+4C

the value of N is preferably an integer of 1 to 6.

And 2, counting the continuous and unchangeable N values (1-6) to obtain a diagnosis variable. The value of N is changed along with the change of the running state of the synchronous motor, but the sampling time of the value of N is very short, so the running state of the synchronous motor is considered to be unchanged within one sampling time of the value of N, and the value of N is continuously the same.

And 3, judging whether the diagnosis variable (counting value) exceeds a set threshold value. If so, let the flag corresponding to the value of N be set to 1, otherwise set to 0. Compared with the normal operation, when the power switch tube has an open-circuit fault, the counting of the continuous same N value is more than 3 times because the voltage vector cannot be compensated. The most direct reaction is that in the N-value waveform diagram, when the power switch tube has an open-circuit fault, the N-value image has a longer waveform, as shown in fig. 6 to 10. The threshold value can be selected according to

Selection is made, where t_sIs the same duration of N value in normal operation, S is the total value of the count of all N values in one period, T_sIs a period duration. The threshold selected by the present invention is 500.

And 4, repeating the steps 1-3 in a three-phase voltage fundamental wave period of system operation, determining abnormal N values (1-6) through six zone bits when the system operates to one period, recording the abnormal N values (0-6, and if N is zero, indicating a fault-free area, namely a non-zone position 1), and clearing the diagnosis variables and the zone bits.

And 5, converting the abnormal N value (namely the N value) into the abnormal sector number (0-6, wherein 0 represents a non-fault area) through the corresponding relation between the N value and the sector number. The correspondence between the N value and the sector number is shown in table 1.

TABLE 1N-VALUE AND FAN-NUMBER CORRESPONDING TABLE

N	1	2	3	4	5	6
							Sector number	2	6	1	4	3	5

And 6, accurately positioning the single tube or the multiple tubes with the open-circuit fault through the corresponding relation table between the sector numbers and the power switch tubes. The system enters the next system three-phase voltage fundamental wave period. When an open-circuit fault occurs, the faulty switch tube, the N value, the sector number, and the corresponding target state of the switch tube are shown in tables 2 and 3.

TABLE 2 corresponding relationship between fault switch tube, N value and sector number in case of single tube fault

Value of N	3,2	1,5	4,6	4,5	2,6	1,3
							Sector number	1,6	2,3	4,5	4,3	6,5	2,1
Fault switch tube	S1	S3	S5	S4	S6	S2

TABLE 3 correspondence of fault switch tube, N value, sector number in case of multiple tube fault

Value of N	Sector number	Fault switch tube
			2,3,4,5	6,1,3,4	S1, S4
1,2,5,6	2,3,5,6	S3, S6
			1,3,4,6	1,2,4,5	S5, S2
1,2,3,5	6,1,2,3	S1, S3
			2,3,4,6	4,5,6,1	S1, S5
1,4,5,6	2,3,4,5	S3, S5
			2,4,5,6	3,4,5,6	S4, S6
1,3,4,5	1,2,3,4	S4, S2
			1,2,3,6	5,6,1,2	S6, S2
2,3,6	5,6,1	S1, S6
			1,2,3	6,1,2	S1, S2
1,4,5	2,3,4	S3, S4
			1,3,5	1,2,3	S3, S2
4,5,6	3,4,5	S5, S4
			2,4,6	4,5,6	S5,S6

Example 1

In this embodiment, to embody the dynamic performance and stability of the present invention, the wind speed is set to be a variable wind speed, as shown in fig. 5, and the operating status of the system power switch tube is set as follows: in 0-1 second, 6 power switch tubes all work normally; 1-2 seconds, the S1 tube has single tube open circuit fault; 2-3 seconds, the S1 and S3 tubes have multi-tube open circuit faults; 3-4 seconds, the S1 and S3 tubes recover to work normally, and the S5 tube has single-tube open-circuit fault; and 4-5 seconds, all the power switch tubes recover to work normally. The method comprises the following specific steps:

0-1 second: the system normally operates, the N value is abnormal after the acquisition waveform and the threshold value are judged (namely N^*The value, 0 for no abnormal N value), abnormal sector number (0-6, 0 for no abnormal sector number), and fault location are shown in fig. 6. As can be seen from the figure, when the system is in normal operation, no longer N-value waveform appears, so N^*The value and the abnormal sector number are both 0, and the fault location shows 0, namely no open circuit fault occurs.

1-2 seconds: s1 switching tube has single tube open circuit fault, N value collection waveform, and abnormal N value (N is N value) after judgment of N value and threshold value^*The value, 0 for no abnormal N value), abnormal sector number (0-6, 0 for no abnormal sector number), and fault location are shown in fig. 7. It can be seen from the figure that when the S1 switching tube has an open-circuit fault, the N-value acquisition waveform has a longer waveform than the normal waveform, which is the abnormal N value, and N is used^*Values were recorded as: 2. 3; the corresponding abnormal sector numbers are: 1. 6; the fault location display 1 diagnoses the open circuit fault of the S1 tube.

2-3 seconds: the S1 tube is still in open-circuit fault state, and the S3 tube has open-circuit fault, the collection waveform of N value, and abnormal N value (namely N value after being judged by the N value and the threshold value)^*The value, 0 for no abnormal N value), abnormal sector number (0-6, 0 for no abnormal sector number), and fault location are shown in fig. 8. It can be seen that the abnormal N value is increased, while N is increased^*The value becomes: 1. 2, 3 and 5; the corresponding abnormal sector numbers are: 1. 2, 3 and 6; fault location display 13, i.e. diagnosing both S1 and S3 tubesAn open circuit fault occurs.

3-4 seconds: the S1 and S3 tubes recover to normal work, the S4 tube has single tube open circuit fault, the collection waveform of the N value and the abnormal N value (namely the N value after the judgment of the N value and the threshold value) occur^*The value, 0 for no abnormal N value), abnormal sector number (0-6, 0 for no abnormal sector number), and fault location are shown in fig. 9. It can be seen that the value of the anomaly N has changed, N^*The value becomes: 4. 6; the corresponding abnormal sector numbers are: 4. 5; the fault location shows 5, i.e. the open circuit fault of the S5 tube.

4-5 seconds: all switch tubes recover to work normally, and the acquired waveform of the N value and the abnormal N value (namely N) after the judgment of the N value and the threshold value^*The value, 0 for no abnormal N value), abnormal sector number (0-6, 0 for no abnormal sector number), and fault location are shown in fig. 10. It can be seen that there is no abnormal N value, N^*The value becomes: 0; the corresponding abnormal sector numbers are: 0; and (5) displaying 0 by fault location, namely recovering all the switch tubes to work normally.

According to the embodiment, the running state of the power switching tube can be tracked in time, the dynamic performance is good, and on one hand, after the power switching tube is repaired, whether the power switching tube works normally can be seen without restarting a system; on the other hand, whether the power switching tube has a permanent open-circuit fault or an intermittent open-circuit fault caused by gate signal loss can be judged, and maintenance personnel can conveniently make a maintenance scheme.

Claims

1. A three-phase rectifier open-circuit fault diagnosis method based on SVPWM sector numbers is characterized by comprising the following steps:

step 1, collecting an N value corresponding to an SVPWM sector number;

the N value of the step 1 is generated by a control algorithm for generating an IGBT gate signal, wherein a part of SVPWM control algorithm for generating the N value is as follows:

a linear transformation is defined:

wherein U is_a、U_b、U_cIs the stator three-phase voltage;

three symbolic functions are defined A, B, C: when U1 is greater than 0, A is 1, otherwise 0; when U2 is greater than 0, B is 1, otherwise is 0; when U3 is greater than 0, C is 1, otherwise 0, and the condition that ABC is 1 or 0 at the same time does not exist, so that 6 states can be combined;

the expression defining the value of N is:

N＝A+2B+4C

the value of N is preferably an integer of 1 to 6;

step 2, counting the continuous and unchangeable N values, and determining a diagnosis variable;

step 3, judging whether the diagnosis variable exceeds a set threshold value, if so, setting a mark position 1 corresponding to the N value, and otherwise, setting the mark position 0;

step 4, repeating the steps 1-3 in a three-phase voltage fundamental wave period of system operation, determining an abnormal N value through six zone bits when the system operates to a period, and using N^*Recording;

step 5, through the corresponding relation between the N value and the sector number, the N is calculated^*The value is converted to an abnormal sector number;

and 6, accurately positioning the single tube or the multiple tubes with the open-circuit fault through the corresponding relation table between the sector numbers and the power switch tubes.

2. The SVPWM sector number-based three-phase rectifier open-circuit fault diagnosis method of claim 1, wherein the threshold set in step 3 is

Wherein t is_sIs the same duration of N value in normal operation, S is the total value of the count of all N values in one period, T_sIs a period duration.

3. The SVPWM sector number-based three-phase rectifier open-circuit fault diagnosis method of claim 1, wherein the correspondence between N value and sector number in step 5 is shown in Table 1:

TABLE 1N-VALUE AND FAN-NUMBER CORRESPONDING TABLE

N 1 2 3 4 5 6 Sector number 2 6 1 4 3 5

4. The open-circuit fault diagnosis method for the three-phase rectifier based on the SVPWM sector number according to claim 1, wherein the correspondence relationship between the N value, the sector number and the fault switch tube in step 6 is shown in tables 2 and 3:

Value of N Sector number Fault switch tube 2,3,4,5 6,1,3,4 S1,S4 1,2,5,6 2,3,5,6 S3,S6 1,3,4,6 1,2,4,5 S5,S2 1,2,3,5 6,1,2,3 S1,S3 2,3,4,6 4,5,6,1 S1,S5 1,4,5,6 2,3,4,5 S3,S5 2,4,5,6 3,4,5,6 S4,S6 1,3,4,5 1,2,3,4 S4,S2 1,2,3,6 5,6,1,2 S6,S2 2,3,6 5,6,1 S1,S6 1,2,3 6,1,2 S1,S2 1,4,5 2,3,4 S3,S4 1,3,5 1,2,3 S3,S2 4,5,6 3,4,5 S5,S4 2,4,6 4,5,6 S5,S6