A Diagnostic Method for Open-Circuit Fault of Windings in a Six-Phase Reconfigured On-Vehicle Charging System

Abstract

The present invention discloses a method for diagnosing winding open - circuit faults in a six - phase reconstructed in - vehicle charging system, including a fault detection part and a fault location part after the fault. The fault detection part performs coordinate transformation on the current flowing through the asymmetric six - phase permanent - magnet synchronous motor winding through space vector decoupling. After the transformation, α‑β the sub - plane contains fault information, and fault detection is realized through the numerical change of the current vector angle transformation rate; the sampling flag bit of the fault location part is to mark the current in each winding within each sampling period. After sampling for a period of time, the arithmetic mean value of all the sampling flag bits is calculated. Through the magnitude relationship between the arithmetic mean value of the sampling flag bits of each winding and the set threshold, the location of the faulty winding is realized. The present invention provides a method for diagnosing winding open - circuit faults in a six - phase reconstructed in - vehicle charging system. This method avoids complex motor mathematical models and cumbersome operations, and improves the fast response ability of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of power fault diagnosis, and particularly to a method for diagnosing winding open - circuit faults in a six - phase reconfigured on - vehicle charging system. Background Art

[0002] The reconfigured on - vehicle charging system can achieve high - power - factor charging for electric vehicles by sharing the reconfigured electric drive system, and has now been favored by scholars at home and abroad. Considering that most power grids are three - phase, the existing research results of reconfigured on - vehicle charging systems mainly focus on three - phase and multi - three - phase (six - phase, nine - phase, etc.) electric drive systems. As one of the main faults of the six - phase reconfigured on - vehicle charging system, the winding open - circuit fault has received extensive research and attention. The research focus is mainly on how to achieve the safe operation of the system through corresponding control strategies after the fault occurs, but the most basic and important part of the entire system, that is, the fault diagnosis part, is rarely mentioned. Currently, the mainstream winding open - circuit diagnosis scheme for six - phase reconfigured on - vehicle charging systems requires additional sensors and complex mathematical models as well as signal - processing algorithms, which cannot meet the requirements of less data volume and fast response speed in practice. Summary of the Invention

[0003] Object of the Invention: Aiming at the above - mentioned existing technology, a method for diagnosing winding open - circuit faults in a reconfigured on - vehicle charging system is proposed, which avoids complex motor mathematical models and cumbersome operations and improves the fast - response ability of the system.

[0004] Technical Solution: A method for diagnosing winding open - circuit faults in a six - phase reconfigured on - vehicle charging system, where the six - phase reconfigured on - vehicle charging system includes a three - phase power source, windings ABC and windings UVW of an asymmetric six - phase permanent - magnet synchronous motor, a dual - three - phase voltage - source inverter, a DC - side voltage - stabilizing capacitor C1, a battery B1, and switching elements K1, K2, K3, K4; among them, the first ends of winding A and winding U are connected to the voltage e of the three - phase power source ga , the first ends of winding B and winding W are connected to the voltage e of the three - phase power source gb , the first ends of winding C and winding V are connected to the voltage e of the three - phase power source gc ; the switching element K1 is connected in parallel between the first ends of winding A and winding B, the switching element K2 is connected in parallel between the first ends of winding B and winding C, the switching element K3 is connected in parallel between the first ends of winding U and winding V, and the switching element K4 is connected in parallel between the first ends of winding V and winding W; the second ends of winding ABC are connected to the output end of the first inverter in the dual - three - phase voltage - source inverter, the second ends of winding UVW are connected to the output end of the second inverter in the dual - three - phase voltage - source inverter, and the input ends of the first inverter and the second inverter are connected in parallel; the DC - side voltage - stabilizing capacitor C1 and the battery B1 are connected in parallel between the input ends of the first inverter and the second inverter;

[0005] The winding open - circuit fault diagnosis method for a six - phase reconfigured on - vehicle charging system includes:

[0006] Step 1: Calculate the change rate of the current vector angle to achieve fault detection;

[0007] Adopt the vector space decoupling coordinate transformation method to map the six - phase current flowing through the asymmetric six - phase permanent - magnet synchronous motor winding to three mutually orthogonal sub - spaces. Among them, the current in the α - β sub - plane is calculated by Equation (1):

[0008]

[0009] In the formula, I α , I β are the currents in the α - β plane, I g is the grid - side current, and θ g is the grid - side voltage phase;

[0010] Obtain the angle θ of the current vector in the α - β sub - plane according to Equation (2), and calculate the angle change rate d according to Equation (3);

[0011]

[0012]

[0013] When it is detected that the angle change rate d satisfies d>1, it is determined that a winding open - circuit fault has occurred;

[0014] Step 2: Calculate the average polarity of the winding current to achieve post - fault location;

[0015] Sample the current non - negative flag bit T j (k) as shown in Equation (4), and calculate the arithmetic mean value F j (k) of the current non - negative flag bit T j :

[0016]

[0017]

[0018] In the formula, j = A, B, C, U, V, W, and k is the sampling count; realize the fault winding location by judging the numerical value of F j : When the value exceeds the set threshold, the winding number at the j position is the fault winding number.

[0019] Furthermore, the threshold is taken as 0.7.

[0020] Beneficial effects: A method for diagnosing open - circuit faults in the windings of a six - phase reconfigured in - vehicle charging system according to the present invention includes a fault detection part and a post - fault location part. The fault detection part performs coordinate transformation on the current flowing through the windings of an asymmetric six - phase permanent - magnet synchronous motor (ASPMSM) through space vector decoupling (VSD). After transformation, the fault information is contained in the α - β sub - plane. Fault detection is achieved through the numerical change of the current vector angle transformation rate. The sampling flag bit of the fault location part is to mark the current in each winding within each sampling period (1 for non - negative and 0 for the rest). After sampling for a period of time, the arithmetic mean of all sampling flag bits is calculated. The location of the faulty winding is achieved through the relationship between the arithmetic mean of the sampling flag bits of each winding and the set threshold. The present invention provides a method for diagnosing open - circuit faults in the windings of a six - phase reconfigured in - vehicle charging system, which avoids complex motor mathematical models and cumbersome operations and improves the system's fast response ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the topology diagram of the six - phase reconfigured in - vehicle charging system.

[0022] Figure 2 is the flowchart of fault detection.

[0023] Figure 3 is the detection schematic diagram.

[0024] Figure 4 is the flowchart of fault location.

[0025] Figure 5 is the waveform schematic diagram of fault location. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The following further explains the present invention with reference to the accompanying drawings.

[0027] As Figure 1 shown, the six - phase reconfigured in - vehicle charging system includes a three - phase power source, two sets of windings ABC and UVW of an asymmetric six - phase permanent - magnet synchronous motor (ASPMSM), a dual - three - phase voltage - source inverter, a DC - side voltage - stabilizing capacitor C1, a battery B1, and switching elements K1, K2, K3, K4. Among them, the first ends of winding A and U are connected to the voltage e ga of the three - phase power source, the first ends of winding B and W are connected to the voltage e gb of the three - phase power source, and the first ends of winding C and V are connected to the voltage e gcThrough this connection method, the phase sequences of the currents flowing through the two sets of windings are opposite, and the generated rotating magnetic fields cancel each other out. The switching element K1 is connected in parallel between the first ends of winding A and winding B, the switching element K2 is connected in parallel between the first ends of winding B and winding C, the switching element K3 is connected in parallel between the first ends of winding U and winding V, and the switching element K4 is connected in parallel between the first ends of winding V and winding W. The second ends of windings ABC are connected to the output end of the first inverter in the dual three-phase voltage source inverter, and the second ends of windings UVW are connected to the output end of the second inverter in the dual three-phase voltage source inverter. The input ends of the first inverter and the second inverter are connected in parallel; the DC-side voltage stabilizing capacitor C1 and the battery B1 are connected in parallel between the input ends of the first inverter and the second inverter. When the switching elements K1, K2, K3, and K4 are disconnected, the system operates in the charging mode at this time. The two sets of windings ABC and UVW of the six-phase permanent magnet synchronous motor are used as filter inductors, and the three-phase power charges the battery B1 through the windings; if the three-phase power supply is disconnected and the switching elements are all closed, the system operates in the electric drive mode at this time. At this time, the battery B1 is used as a power source to drive the normal operation of the six-phase permanent magnet synchronous motor.

[0028] Figure 2 It is a flowchart for fault detection. The specific steps of the open-circuit fault diagnosis method for the windings of the six-phase reconfigurable on-vehicle charging system are as follows:

[0029] Adopt the vector space decoupling (VSD) coordinate transformation method to map the six-phase current flowing through the windings of the asymmetric six-phase permanent magnet synchronous motor to three mutually orthogonal subspaces. The current in the α-β sub-plane is calculated by Equation (1):

[0030]

[0031] In the formula, I α , I β are the currents in the α-β plane, I g is the grid-side current, and θ g is the phase of the grid-side voltage.

[0032] According to Equation (2), obtain the angle θ of the current vector in the α-β sub-plane, and then calculate the angle change rate d according to Equation (3);

[0033]

[0034]

[0035] Figure 3 It is a detection schematic diagram. Among them, Figure (a) is a schematic diagram of the current vector trajectory in the α-β plane in the healthy mode, Figure (b) is a schematic diagram of the current vector trajectory in the α-β plane after the fault, Figure (c) is a schematic diagram of the angle θ of the current vector in the healthy mode, and Figure (d) is a schematic diagram of the angle change rate d of the current vector in the healthy mode.

[0036] In the healthy operation mode, the trajectory of the current vector in the α-β plane is a straight line, the system has no electromagnetic torque output, the angle θ of its current vector is a constant, and the rate of change of the angle d (i.e., the slope of the straight line) is 0. When a winding fault occurs, the current vector will rotate at this time, and its trajectory in the α-β plane changes. Therefore, it is possible to judge whether a fault occurs in the system by calculating the rate of change of the current vector angle.

[0037] When it is detected that the rate of change of the angle d satisfies d>1, it is determined that a winding open circuit fault has occurred.

[0038] Such as Figure 4 shown in the fault location flowchart, i j is the current in each winding, T j (k) is the non-negative flag bit of the sampled current, F j is the arithmetic mean, S j is the location threshold.

[0039] Figure 5 is the schematic diagram of the fault location waveform. Among them, Figure (a) is the schematic diagram of the current waveform in the A-phase winding in the healthy mode, Figure (b) is the schematic diagram of the non-negative flag bit value of the sampled current, Figure (c) is the schematic diagram of the current waveform in the A-phase winding after the fault, and Figure (d) is the schematic diagram of the non-negative flag bit value of the sampled current after the fault.

[0040] After detecting the occurrence of a fault, it is necessary to further locate the fault. It is necessary to calculate the average polarity of the current in a basic period, T j (k), F j is expressed as:

[0041]

[0042]

[0043] In the formula, j = A, B, C, U, V, W, and k is the sampling count. When the value exceeds the set threshold, the winding number at the j position is the fault winding number. Under the healthy operation condition, the current waveforms flowing through each winding are standard sine waveforms, and F j is close to 0.5. In the case of a winding open circuit, taking the A phase as an example, no current flows through the A-phase winding, T A (k) is often 1, and F A will be close to 1, greater than the set threshold of 0.7, then it can be judged that the A-phase winding is faulty. Through this method, the faulty winding can be quickly located.

[0044] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for diagnosing open-circuit faults in windings of a six-phase reconstructed in-vehicle charging system, characterized in that: The six-phase reconfigured on-vehicle charging system includes a three-phase power supply, two three-phase windings of an asymmetric six-phase permanent magnet synchronous motor, a dual-three-phase voltage source inverter, a DC-side voltage stabilizing capacitor C1, a battery B1, and switching elements K1, K2, K3, and K4. One set of three-phase windings consists of windings A, B, and C, and the other set of three-phase windings consists of windings U, V, and W. Among them, the first ends of winding A and U are connected to the voltage e of the three-phase power supply ga , the first ends of winding B and W are connected to the voltage e of the three-phase power supply gb , and the first ends of winding C and V are connected to the voltage e of the three-phase power supply gc ; The switching element K1 is connected in parallel between the first ends of winding A and winding B, the switching element K2 is connected in parallel between the first ends of winding B and winding C, the switching element K3 is connected in parallel between the first ends of winding U and winding V, and the switching element K4 is connected in parallel between the first ends of winding V and winding W; The second ends of windings A, B, and C are connected to the output end of the first inverter in the dual-three-phase voltage source inverter, and the second ends of windings U, V, and W are connected to the output end of the second inverter in the dual-three-phase voltage source inverter. The input ends of the first inverter and the second inverter are connected in parallel; The DC-side voltage stabilizing capacitor C1 and the battery B1 are connected in parallel between the input ends of the first inverter and the second inverter; The method for diagnosing the winding open - circuit fault of a six - phase reconfigured in - vehicle charging system includes: Step 1: Calculate the change rate of the current vector angle to achieve fault detection; Using the vector space decoupling coordinate transformation method, map the six - phase current flowing through the asymmetric six - phase permanent - magnet synchronous motor winding to three mutually orthogonal sub - spaces. Among them, the current in the α - β sub - plane is calculated by Equation (1): Where, I α , I β are the currents in the α-β plane, I g is the grid-side current, and θ g is the grid-side voltage phase; Obtain the angle θ of the current vector in the α - β sub - plane according to Equation (2), and calculate the change rate d according to Equation (3); When it is detected that the change rate d satisfies d > 1, it is determined that a winding open - circuit fault has occurred; Step 2: Calculate the average polarity of the winding current to achieve post - fault location; Sampling current non - negative flag bit T j (k) As shown in Equation (4), calculate the current non - negative flag bit T according to Equation (5) j (k) Arithmetic mean value F j : where j = A, B, C, U, V, W and k is the sampling count; the faulty winding is located by judging the value of F j : when the value exceeds the set threshold, the winding number at position j is the faulty winding number.

2. A method for diagnosing open - circuit faults in the windings of a six - phase reconfigured in - vehicle charging system according to claim 1, characterized in that: The threshold value is taken as 0.7.

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