Fault-tolerant control method for dual-channel electric drive multiplexing type vehicle-mounted charging system

Abstract

The invention discloses a fault-tolerant control method for a dual-channel electric drive multiplexing type vehicle-mounted charging system. Firstly, three-phase power grid voltage is collected, and a phase angle is obtained; secondly, collecting charging current and voltage of the double battery packs, and calculating an x-y plane reference current amplitude through constant-voltage and constant-current control to obtain an x-y plane reference current expression; then, according to the open-circuit fault condition of the six-phase symmetric motor winding, obtaining an alpha-beta plane reference current flow formula; then, under the condition that the instantaneous charging torque is zero, a reference current expression of an alpha-beta plane is determined according to the position angle of a motor rotor; and finally, obtaining a six-phase winding reference current value and an actual current value according to VSD inverse transformation, obtaining a six-phase reference voltage value through a PR controller, and generating a switch tube driving signal through SPWM modulation. According to the open-circuit fault condition of the winding, the position angle of the motor rotor is combined, alpha-beta plane current is injected, it is guaranteed that the instantaneous torque is zero in the charging process, and online fault-tolerant control is achieved.

Description

Technical Field

[0001] The present invention relates to a power electronics and electric drive control method, and in particular to a fault-tolerant control method for a dual-channel electric drive multiplexing on-board charging system. Background Art

[0002] The lack of charging infrastructure is still one of the key factors restricting the popularization of electric vehicles. Traditional on-board charging systems mostly adopt a single-channel design, which can only charge a single battery pack and cannot meet the demand for efficient charging in high-power scenarios. To solve this problem, a dual-channel electric drive multiplexing on-board charging system came into being. The system introduces two independent charging channels to achieve simultaneous charging of dual battery packs, improving charging speed and system reliability.

[0003] However, when the system is running at high power for a long time, the multi-phase motor winding is prone to open circuit failure. Although the dual-channel electric drive multiplexing on-board charging system has a certain fault tolerance capability, when one of the channels has an open circuit winding failure, it is immediately cut off, and the other channel can still take on the charging task. However, this will cause the faulty channel and its corresponding battery pack to be idle, and the system can only rely on the remaining channel to charge a battery pack, which cannot give full play to the characteristics of the dual-channel design, resulting in reduced charging efficiency and range. Summary of the invention

[0004] Purpose of the invention: In view of the above-mentioned prior art, a fault-tolerant control method for a dual-channel electric drive multiplexing on-board charging system is proposed to achieve online fault-tolerant control of system winding open-circuit faults.

[0005] Technical solution: A fault-tolerant control method for a dual-channel electric drive multiplexing on-board charging system. First, the three-phase grid voltage is collected and the phase angle is obtained through a phase-locked loop; secondly, the charging current and voltage of the dual battery pack are collected, and the xy plane reference current amplitude is calculated through battery constant voltage and constant current control, and then the xy plane reference current expression is obtained; then, a mathematical model is built according to the open circuit fault of the six-phase symmetrical motor winding, and the α-β plane reference current general formula is obtained; then, under the condition that the instantaneous charging torque is zero, the reference current expression of the α-β plane under the condition that the instantaneous charging torque is zero is determined according to the motor rotor position angle; finally, the six-phase winding reference current value and actual current value are obtained according to the VSD inverse transformation, and the six-phase reference voltage value is obtained through the PR controller, and then the switch tube drive signal is generated through SPWM modulation.

[0006] Beneficial effect: The fault-tolerant control method of a dual-channel electric drive multiplexed vehicle charging system of the present invention injects α-β plane current according to the system winding open circuit fault condition and the motor rotor position angle to ensure that the instantaneous torque is zero during the charging process and realize online fault-tolerant control. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a dual-channel electric drive multiplexing on-board charging system circuit topology;

[0008] Figure 2 This is a control block diagram of a fault-tolerant control method for a dual-channel electric drive multiplexing vehicle charging system;

[0009] Figure 3 The circuit topology formed by the channel after the B phase of the winding is open circuit fault;

[0010] Figure 4 Simulate the waveforms of the grid b-phase voltage and three-phase grid current in the normal working mode of the system;

[0011] Figure 5 The simulation waveform of the six-phase symmetrical motor winding current in the normal working mode of the system;

[0012] Figure 6 Simulate the waveforms α-β, xy and zero-sequence plane current in the normal working mode of the system;

[0013] Figure 7 Simulate the waveforms of the dual battery pack charging current and the motor instantaneous torque in the normal working mode of the system;

[0014] Figure 8 Simulate the waveforms of the grid b-phase voltage and three-phase grid current in the fault-tolerant working mode of the system;

[0015] Fig. 9 The current simulation waveforms of phase A, phase B and phase C of the motor winding are provided for the system in the fault-tolerant working mode;

[0016] Fig.10 Simulation waveform α-β and xy plane current simulation waveform for the system in fault-tolerant working mode;

[0017] Fig.11 Simulate the waveforms of the dual battery pack charging current and motor instantaneous torque in the fault-tolerant working mode of the system. DETAILED DESCRIPTION

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and by way of examples. The following examples are intended to explain the present invention but the present invention is not limited to the following examples.

[0019] like Figure 1 As shown in the figure, the circuit topology of the dual-channel electric drive multiplexing on-board charging system, the six-phase symmetrical motor windings are reused as filter inductors, and the two inverters are reused as three-phase voltage-type rectifiers. The six-phase windings of the motor are divided into two sets, which are connected to two inverters to form a dual channel, powered by a three-phase grid, and charge the dual battery packs at the same time.

[0020] like Figure 2 As shown, a fault-tolerant control method for a dual-channel electric drive multiplexing vehicle charging system includes the following steps:

[0021] Step 1: Collect the three-phase grid voltage value u gabc , the grid voltage phase angle θ is obtained through the phase-locked loop g .

[0022] Step 2: Collect the charging current i of the dual battery pack dc1 、i dc2 And the charging voltage u dc1 、u dc2 , the xy plane reference current amplitude I is calculated by the battery constant voltage and constant current control m1 ,I m2 , combined with the grid voltage phase angle θ g , after calculation, the reference current expression in the xy plane is obtained.

[0023] Specifically, the xy plane reference current amplitude I m1 ,I m2 The relationship that needs to be satisfied is:

[0024]

[0025] In addition, the phases of the reference currents in the xy plane are 90° apart, and the phase of the reference current on the x-axis is consistent with the phase of the grid voltage. At this time, the expression of the reference current in the xy plane is:

[0026]

[0027] In the formula, and are the x-axis and y-axis reference currents, θ g is the grid voltage phase angle.

[0028] Step 3: When the system is in normal working mode, set the α-β plane and zero-sequence plane reference current to 0. Combined with the xy plane reference current expression, further calculation using VSD transformation can obtain the same phase angle of the grid voltage and current, ensuring the minimum reactive power when the system is working.

[0029] Among them, the VSD transformation matrix T of the six-phase symmetrical permanent magnet synchronous motor is:

[0030]

[0031] Wherein, θ=60°.

[0032] In the fault-tolerant working mode, the system performs a topological analysis on the system after the fault based on the open-circuit fault of the six-phase symmetrical motor winding. Figure 3As shown, taking the case of an open circuit of winding B phase as an example, the circuit topology formed by the channel after the fault can be equivalent to a single-phase rectifier circuit. In order to ensure effective rectification, the following conditions need to be met:

[0033] i A +i C =0 (4)

[0034] In the formula, i A and i C They are the A-phase and C-phase currents of winding respectively.

[0035] Since the sum of the six-phase winding currents of the motor is 0, then 0 2 Shaft current i 02 It can be expressed as:

[0036]

[0037] Accordingly, 0 1 Shaft current i 01 It can be expressed as:

[0038]

[0039] Through the above analysis, the zero-sequence plane reference current of the system in fault-tolerant working mode satisfies:

[0040]

[0041] In the formula, and 0 1 Axis and 0 2 Axis reference current.

[0042] At this time, using VSD inverse transformation, the six-phase winding current i A 、i B 、i C 、i U 、i V 、i W It can be expressed as:

[0043]

[0044] In the formula, i α 、i β 、i x 、i y They are α-axis, β-axis, x-axis, and y-axis currents respectively.

[0045] When the winding B phase is open, the winding B phase current i B for:

[0046]

[0047] At this time, the current i B and i W The synthesized grid phase b current i gb will change, resulting in an unbalanced grid current. It can be found from equation (8) that injecting current into the α-axis and β-axis can compensate for the grid b-phase current. In order to ensure that the average torque of the motor is zero after the current is injected, the reference current in the α-β plane is set to:

[0048]

[0049] In the formula, and are the reference currents of α-axis and β-axis respectively, l 1 , l 2 , l are constants and l 1 Not 0.

[0050] Substituting equation (10) into equation (9), we can obtain the general formula of the α-β plane reference current:

[0051]

[0052] Similarly, the open circuit faults of all windings of the six-phase symmetrical motor are analyzed. When the open circuit faults occur in the winding phases A, B, C, U, V, and W, the α-β plane reference current formula is specifically:

[0053]

[0054] In the table, k 1 , k 2 , k 3 , k 4 , k 5 , k 6 are constants and k 2 , k 3 , k 4 , k 6 Both are not 0.

[0055] Step 4: To ensure that the instantaneous charging torque is zero when the system is running, the relationship between the motor rotor position angle and the α-β plane current is constructed, and the α-β plane reference current expression is determined based on the rotor position angle.

[0056] Specifically, the d-axis inductance L of the six-phase symmetrical permanent magnet synchronous motor used in the present invention is d and q-axis inductance L q The axes are equal, then the instantaneous torque of the motor during charging is T e It is expressed as:

[0057] T e =3p n iq ψ f =0 (12)

[0058] In the formula, p n is the number of pole pairs of the motor, i q is the q-axis current of the motor, ψ f is the permanent magnet flux of the motor.

[0059] To make the instantaneous torque T e is 0, it is only necessary to ensure that the q-axis current i q is 0, the q-axis current can be expressed as:

[0060] i q =-i α sinθ e +i β cosθ e =0 (13)

[0061] In the formula, θ e is the motor rotor position angle.

[0062] Substituting equation (12) into equation (13), we can get the relationship between the motor rotor position angle and the α-β plane current as follows:

[0063]

[0064] Step 5: Set the reference current values ​​of the three planes and the actual current value i α 、i β 、i x 、i y 、i 01 、i 02 The six-phase winding reference current value is obtained through VSD inverse transformation and the actual current value i A 、i B 、i C 、i U 、i V 、i W , compare the six-phase winding reference current value with the actual current value, and the difference is used by the PR controller to obtain the six-phase reference voltage value d 1 ,d 2 ,d 3 ,d 4 ,d 5 ,d 6 .

[0065] Step 6: Generate the driving signal S of the switch tube by SPWM modulation of the six-phase reference voltage value 1 ~S 12, and then control the on-off, realizing fault-tolerant control of the dual-channel electric drive multiplexing on-board charging system.

[0066] In the simulation model of this embodiment, the effective value of the grid voltage is set to 40V, the grid frequency is set to 50Hz, the rated voltage of the dual battery packs is 144V, the rated capacity is 30Ah, and the initial power is 95%.

[0067] The system is in normal working mode:

[0068] like Figure 4 As shown, the three-phase grid current i ga 、i gb 、i gc It is in the shape of a sine wave with equal amplitude and a phase difference of 120°, which satisfies the current balance of the power grid; the voltage and current of phase b of the power grid are in phase, indicating that the power grid side operates at unity power factor.

[0069] like Figure 5 As shown, the current waveforms of the six-phase symmetrical motor windings are all sinusoidal, and the current i A and i V The waveforms overlap, and the current i B and i W The waveforms overlap, and the current i C and i U Waveforms overlap.

[0070] like Figure 6 As shown, the xy plane current i x and i y The amplitudes are equal and the phases are 90° apart. The α-β plane currents i α and i β and zero sequence plane current i 01 and i 02 Both are 0, which is consistent with the theory.

[0071] like Figure 7 As shown, the charging current i of the dual battery pack is dc1 and i dc2 The motor can follow the given value and remain stable, meeting the charging requirements. When the system is running, the instantaneous torque T e When it is 0, the motor rotor remains stationary.

[0072] The system is in fault-tolerant working mode, with winding B phase open, and the motor rotor position angle θ e Take 120° as an example:

[0073] like Figure 8 As shown, the three-phase grid current i after fault tolerance ga 、i gb 、i gcThe waveform quality is good, sinusoidal, with equal amplitude and 120° phase difference, which meets the current balance of the power grid; the voltage and current of phase b of the power grid are in phase, indicating that the power grid side operates at unity power factor.

[0074] like Fig. 9 As shown, the motor winding phase A and phase C current i A and i C The amplitude is the same and the phase difference is 180°. The current i B is 0, which is consistent with the theory.

[0075] like Fig.10 As shown, the xy plane current i x and i y The amplitudes are equal and the phases are 90° apart. The α-β plane currents i α and i β The phase difference is 180°, which is consistent with the theory.

[0076] like Fig.11 As shown in the figure, due to the influence of the winding open circuit fault, the charging current i dc1 and i dc2 There is a certain amount of ripple, but it remains stable; when the system is running, the instantaneous torque of the motor T e When it is 0, the motor rotor remains stationary.

[0077] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A fault-tolerant control method for a dual-channel electric drive multiplexing vehicle charging system, characterized in that: The steps include: Step S1: Collect the voltage value of the three-phase grid and obtain the grid voltage phase angle through a phase-locked loop; Step S2: collecting the charging current and charging voltage of the dual battery pack, calculating the xy plane reference current amplitude through the battery constant voltage and constant current control, and combining the grid voltage phase angle to calculate the xy plane reference current expression; Step S3: When the system is in the normal working mode, the α-β plane and the zero-sequence plane reference currents are both set to 0; when the system is in the fault-tolerant working mode, when an open-circuit fault occurs in the winding of the six-phase symmetrical motor, the zero-sequence plane reference current is 0, and the α-β plane reference current general formula is obtained by calculating the fault-tolerant current; Step S4: determining a reference current expression in the α-β plane under the condition that the instantaneous charging torque is zero according to the rotor position angle; Step S5: obtaining six-phase winding reference current values ​​and actual current values ​​according to VSD inverse transformation, and obtaining six-phase reference voltage values ​​through a PR controller; Step S6: The six-phase reference voltage values ​​are modulated by SPWM to generate driving signals for the switch tubes, thereby realizing fault-tolerant control of the dual-channel electric drive multiplexing on-board charging system.

2. The fault-tolerant control method for a dual-channel electric drive multiplexing vehicle charging system according to claim 1, characterized in that: In step S2, the xy plane reference current amplitude I is calculated by constant voltage and constant current control of the battery. m1 and I m2 In the equation, two amplitudes need to satisfy: The xy plane reference current expression is: In the formula, and are the x-axis and y-axis reference currents, θ g is the grid voltage phase angle.

3. The fault-tolerant control method for a dual-channel electric drive multiplexing vehicle charging system according to claim 1, characterized in that: In step S3, when the system is in a fault-tolerant working mode, the α-β plane reference current general formula is specifically: Phase A open circuit: Phase B open circuit: Phase C is open: U phase open circuit: V phase open circuit: W phase open circuit: In the formula, and are the reference currents of the α-axis and β-axis respectively, k1, k2, k3, k4, k5, and k6 are all constants, and k2, k3, k4, and k6 are not 0.

4. The fault-tolerant control method for a dual-channel electric drive multiplexing vehicle charging system according to claim 1, characterized in that: In step S4, under the condition that the instantaneous charging torque is zero, the relationship between the motor rotor position angle and the α-β plane current is specifically: In the formula, θ e is the motor rotor position angle.

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