WO2021078083A1

WO2021078083A1 - Real-time detection method for t-type three-phase four-wire rectifier open circuit fault

Info

Publication number: WO2021078083A1
Application number: PCT/CN2020/121779
Authority: WO
Inventors: 赵金; 吴祉汐; 刘洋
Original assignee: 华中科技大学
Priority date: 2019-10-22
Filing date: 2020-10-19
Publication date: 2021-04-29
Also published as: CN110687479B; CN110687479A

Abstract

A real-time detection method for a T-type three-phase four-wire rectifier open circuit fault, which belongs to the online detection field. The method comprises: calculating the number of sampling points L in a sliding window according to the frequency f of the three-phase power supply and sampling frequency v; calculating the centroid distance Δ in the diagnosis period of two capacitor voltages according to the sampling voltages of the two capacitors; calculating the operating domain size D of the centroid distance Δ according to the diameter of the operating track in the diagnosis period of two capacitor sampling voltages; judging whether the centroid distance Δ exceeds the operating domain size D, if so, the T-type three-phase four-wire rectifier has an open circuit fault; otherwise, no open circuit fault occurs. Compared with the certain characteristic fault manifestations in the whole period of the power supply voltage, the method detects the capacitor voltage fault manifestations of a bus in a 1/3 of the power supply voltage period, and has better real-time performance, thereby achieving rapid detection of system faults. In the method, fault detection is designed by balancing the two capacitor voltages of the bus, and improves the robustness of fault detection.

Description

A T-type three-phase four-wire rectifier open-circuit fault real-time detection method

【Technical Field】

The invention belongs to the field of online detection, and more specifically, relates to a real-time detection method for open-circuit faults of a T-type three-phase four-wire rectifier.

【Background technique】

In recent years, with the rapid development of new energy technologies, more and more new energy vehicles have appeared one after another. As an important charging module for charging piles for new energy vehicles, the stability of the rectifier is an important indicator to consider the quality of the system. In the rectifier, the power tube can easily cause open-circuit faults due to high-frequency turn-on and turn-off, which directly affects the normal operation of the system. The T-type three-phase four-wire rectifier is applied to the rectifier module of the charging pile due to its superior performance, and belongs to one of the three-phase three-level rectifier topologies. A real-time and effective diagnosis method is proposed for the open-circuit fault of the T-type three-phase four-wire rectifier, which provides real-time and effective information for subsequent fault-tolerant control strategies, which has important engineering application value for improving the reliability of the system.

In the prior art, most of the real-time detection methods for open faults of three-phase three-level rectifiers are based on signal processing methods such as Fourier transform and wavelet transform, and then optimize the combination of feature quantities to achieve fault diagnosis. There are some complicated calculations and unobvious features. , Threshold selection is not robust and other issues. Especially the switch tube fault of the middle bridge arm is more difficult to detect due to the zero voltage fault feature provided.

[Summary of the invention]

Aiming at the problems of insufficient real-time performance and weak robustness of fault detection in the prior art, the present invention provides a T-type three-phase four-wire rectifier open-circuit fault real-time detection method, which aims to improve the existing power tube bridge arm open-circuit fault Real-time detection algorithm improves detection speed, enhances algorithm robustness, and reduces detection cost.

In order to achieve the above objective, according to the first aspect of the present invention, a real-time detection method for an open circuit fault of a T-type three-phase four-wire rectifier is provided. The method includes the following steps:

S1. Calculate the number of sampling points L in the sliding window according to the frequency f and sampling frequency v of the three-phase power supply;

S2. According to the sampled L sampling voltages of the first capacitor of the rectifier DC bus and L sampling voltages of the second capacitor, calculate the centroid distance Δ of the two capacitor voltage diagnosis periods;

S3. Calculate the size D of the operating domain of the centroid distance Δ according to the diameter of the operating track during the diagnostic cycle of the first capacitor and the second capacitor of the DC bus of the rectifier;

S4. Determine whether the centroid distance Δ exceeds the operating domain size D. If so, the T-type three-phase four-wire rectifier has an open circuit fault, otherwise, no open circuit fault has occurred.

Specifically, the calculation formula for the number of sampling points L is as follows:

Specifically, the sampling frequency v is set to 10 kHz.

Specifically, the calculation formula of the centroid distance Δ in the diagnosis period of the two capacitor voltages is as follows:

Among them, U _c1m represents the m-th sampling point of the first capacitor voltage U _c1 _{, U c2n} represents the n-th sampling point of the second capacitor voltage U _c2 , m,n=1, 2,...,L.

Specifically, the diameter of the running track during the diagnosis period of the first capacitor sampling voltage of the DC bus of the rectifier

Diameter of the running track during the diagnosis cycle of the second capacitor sampling voltage of the rectifier DC bus

Among them, U _cij represents the j-th sampling point of the i-th capacitor voltage U _ci , i=1, 2, j=1,2,...,L.

Specifically, the operating domain size of the centroid distance Δ is D=max(D _uc1 , D _uc2 ).

In order to achieve the above object, according to the second aspect of the present invention, a computer-readable storage medium is provided, and a computer program is stored on the computer-readable storage medium. When the computer program is executed by a processor, the first aspect is implemented. The described T-type three-phase four-wire rectifier open circuit fault real-time detection method.

In general, through the above technical solutions conceived in the present invention, the following beneficial effects can be achieved:

(1) Aiming at the problem of poor real-time performance of fault detection in the prior art, the present invention detects open-circuit faults through the cycle of the voltage fluctuations of the two capacitors of the bus. The bus capacitor voltage fault performance is detected, and the real-time performance is better, so as to realize the rapid detection of system faults.

(2) Aiming at the problem of poor robustness of fault detection in the prior art, the present invention designs fault detection by balancing the voltages of the two capacitors of the bus. Because the voltages of the two capacitors of the bus are in a balanced state under normal conditions, when the system is abnormal, the voltages of the two capacitors of the bus are unbalanced , Thereby improving the robustness of fault detection.

【Explanation of the drawings】

Figure 1 shows the topology of the T-type three-phase four-wire rectifier with a fault diagnosis module provided by this embodiment;

Fig. 2 is a flow chart of a real-time detection method for an open-circuit fault of a T-type three-phase four-wire rectifier provided by this embodiment.

【Detailed ways】

In order to make the objectives, technical solutions, and advantages of the present invention clearer, the following further describes the present invention in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

The present invention performs fault detection based on the symmetry of the bus capacitor voltage, and only needs to add a capacitor voltage sensor to collect variables U _c1 and U _c2 in real time (the control circuit has two bus capacitor voltages and sensors), using 1/3 phase The sliding window of the voltage cycle analyzes the voltages of the two capacitors for fault detection. Due to the three-phase symmetry, the bus capacitance fluctuation period is 1/3 of the phase voltage period. By detecting the deviation of the two capacitor voltages in the fluctuation period, the system fault can be detected more quickly.

As shown in Figure 1, the T-type three-phase four-wire rectifier consists of power tubes (S _A1 , S _A21 , S _A22 , S _A3 , S _B1 , S _B21 , S _B22 , S _B3 , S _C1 , S _C21 , S _C22 , S _C3 ) corresponding to the diode (D _A1 , D _A21 , D _A22 , D _A3 , D _B1 , D _B21 , D _B22 , D _B3 , D _C1 , D _C21 , D _C22 , D _C3 ), bus storage capacitor (C1 , C2), U _c1 and U _c2 are two capacitor voltages respectively, U _d is the DC bus voltage, and i _A , i _B and i _C are three-phase currents. U _d , i _A , i _B , and i _C provide feedback information for the control system. In the fault diagnosis method, the variables U _c1 and U _c2 collected in real time by the capacitance voltage sensor are used.

As shown in Figure 2, the present invention proposes a real-time detection method for open-circuit faults of a T-type three-phase four-wire rectifier. The method includes the following steps:

Step S1. Calculate the number of sampling points L in the sliding window according to the frequency f and the sampling frequency v of the three-phase power supply.

The frequency of the three-phase power supply is f. Due to the symmetry of the three-phase power supply, the voltage fluctuation frequency of the two capacitors of the DC bus is 3f. The AD sampling frequency v is generally set to about 10kHz. The sliding window represents a diagnosis cycle.

Step S2. Calculate the centroid distance Δ of the two capacitor voltage diagnosis cycles according to the sampled L sampling voltages of the first capacitor of the rectifier DC bus and L sampling voltages of the second capacitor.

When the system is operating normally, the rectifier capacitor voltages U _c1 and U _c2 are cyclically sinusoidal, with opposite phases. The corresponding symmetry is shown as follows:

among them,

Indicates the quality of the running track of the capacitor C1 voltage,

Indicates the running track quality of the capacitor C2 voltage. The difference between the two is 0 when the system is running normally, and it is not equal to zero when the system is running abnormally.

The ratio of the accumulated capacitor voltage in a sliding window to the number of sampling points L is the centroid of the voltage running track. The formula for calculating the centroid distance Δ in the two capacitor voltage diagnostic cycles:

Step S3. Calculate the size D of the operating region of the centroid distance Δ according to the diameter of the operating track in the diagnostic cycle of the sampling voltage of the first capacitor and the second capacitor of the rectifier DC bus.

Diameter of the running track during the diagnosis cycle of the first capacitor sampling voltage of the rectifier DC bus

Calculate the size of the operating domain D=max (D _uc1 , D _uc2 ) of the centroid distance Δ.

Step S4. Determine whether the centroid distance Δ exceeds the operating domain size D. If so, the T-type three-phase four-wire rectifier has an open circuit fault; otherwise, no open circuit fault has occurred.

The fault detection is completed by the following formula:

As a fault judgment threshold, the size of the operating domain D changes adaptively with the capacitor voltage to ensure the robustness of the diagnosis. The diagnosis period is 1/3 of the power supply voltage period, and the real-time performance is better.

The invention can detect the open-circuit fault of the T-type three-phase four-wire rectifier in real time, and has guiding significance for the online detection of the open-circuit fault of the bridge arm of the multi-level rectifier system. The present invention is suitable for T-type three-phase four-wire rectifiers, and has low cost. The present invention performs fault detection based on the symmetry of the bus capacitor voltage, and only needs to add a capacitor voltage sensor; the detection accuracy is high, the speed is fast, and the real-time performance is high. The invention can quickly detect the open circuit fault of the bridge arm in the rectifier in real time and perform pre-positioning. Good robustness, strong anti-interference ability, dynamic processes such as rectifier startup, voltage transformation, and load change will not negatively affect the fault diagnosis result of the present invention; and the solution is insensitive to system internal parameters and has strong anti-disturbance ability. The realization is simple, and the present invention can be embedded into the control program as a subprogram without affecting or modifying the control program.

Those skilled in the art can easily understand that the above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modification, equivalent replacement and improvement, etc. made within the spirit and principle of the present invention, All should be included in the protection scope of the present invention.

Claims

A T-type three-phase four-wire rectifier open circuit fault real-time detection method is characterized in that the method includes the following steps:

S1. Calculate the number of sampling points L in the sliding window according to the frequency f and sampling frequency v of the three-phase power supply;

S2. According to the sampled L sampling voltages of the first capacitor of the rectifier DC bus and L sampling voltages of the second capacitor, calculate the centroid distance Δ of the two capacitor voltage diagnosis periods;

S3. Calculate the size D of the operating domain of the centroid distance Δ according to the diameter of the operating track during the diagnostic cycle of the first capacitor and the second capacitor of the DC bus of the rectifier;

S4. Determine whether the centroid distance Δ exceeds the operating domain size D. If so, the T-type three-phase four-wire rectifier has an open circuit fault, otherwise, no open circuit fault has occurred.
The method according to claim 1, wherein the calculation formula of the number of sampling points L is as follows:
The method according to claim 1 or 2, wherein the sampling frequency v is set to 10 kHz.
The method according to any one of claims 1 to 3, wherein the calculation formula of the centroid distance Δ in the diagnosis period of two capacitor voltages is as follows:

Among them, U c1m represents the m-th sampling point of the first capacitor voltage U c1 , U c2n represents the n-th sampling point of the second capacitor voltage U c2 , m,n=1, 2,...,L.
The method according to any one of claims 1 to 4, wherein the diameter of the running track during the diagnosis period of the first capacitor sampling voltage of the DC bus of the rectifier

Diameter of the running track during the diagnosis cycle of the second capacitor sampling voltage of the rectifier DC bus

Among them, U cij represents the j-th sampling point of the i-th capacitor voltage U ci , i=1, 2, j=1,2,...,L.
The method according to claim 5, characterized in that the size of the operating domain of the centroid distance Δ is D=max(D uc1 , D uc2 ).
A computer-readable storage medium, wherein a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the T-type according to any one of claims 1 to 6 is realized. Three-phase four-wire rectifier open circuit fault real-time detection method.