Dual-channel electric drive multiplexing type vehicle-mounted charging system unbalanced current suppression method

Abstract

The invention discloses a dual-channel electric drive multiplexing type vehicle-mounted charging system unbalanced current suppression method, which comprises the following steps of: firstly, popularizing and applying a positive and negative sequence separation method for decoupling a dual-synchronous coordinate system to a dual-channel six-phase motor, and calculating positive and negative sequence components of a dq axis of a dual-channel system under a current unbalanced working condition; utilizing Park and VSD transformation to map the data to an alpha beta xy0102 sub-plane; secondly, setting a positive-sequence current given value and a negative-sequence current given value to be 0 by using a six-phase current distribution method for minimizing electromagnetic torque; then, independent PI control is carried out on each sub-plane; and finally, correspondingly adding the output quantities of the positive sequence current and the negative sequence current of each sub-plane, returning to a natural coordinate system through TVSD-1, and then outputting SPWM, thereby realizing a three-phase charging working condition. According to the method, the suppression of the negative-sequence current can be realized, the sine degree of the power grid current is improved, the torque ripple is suppressed, and the system safety is guaranteed.

Description

Technical Field

[0001] This invention relates to a method for suppressing unbalanced current in a dual-channel electric drive multiplexing on-board charging system, belonging to the field of power electronics and electric transmission. Background Technology

[0002] Electric drive reuse-type on-board charging systems, as an emerging charging technology, achieve charging functionality by reconfiguring motor windings and reused electric drive inverters. This addresses the drawbacks of traditional on-board charging systems, such as large size, high cost, and complex structure, making it a research hotspot and attracting widespread attention. To further improve the operational reliability of electric vehicles, a dual-channel electric drive reuse-type on-board charging system has been proposed. In this system, the electric drive system is modularized into multiple channels, each consisting of three symmetrical windings and equipped with a three-phase inverter drive unit powered by an independent battery pack. However, when a motor winding fault occurs, the resistance on one phase increases, causing an imbalance in the winding current, further affecting the grid current and increasing torque ripple. Therefore, the analysis and suppression of unbalanced current under three-phase charging conditions are indispensable.

[0003] Existing technologies only analyze the current control method for dual-channel electric drive multiplexed on-board charging systems under conventional three-phase charging conditions. However, under conditions where the resistance of one phase winding suddenly increases, the current flowing through the six-phase motor windings becomes unbalanced, resulting in harmonics in the grid current and a deterioration in power quality. No existing technology has yet provided an analysis of this aspect. Furthermore, the torque pulsation caused by the unbalanced current affects the charging safety of electric vehicles. Summary of the Invention

[0004] Purpose of the invention: To address the above-mentioned problems, a method for suppressing unbalanced current in a dual-channel electric drive multiplexing on-board charging system is proposed.

[0005] Technical solution: A method for suppressing unbalanced current in a dual-channel electric drive multiplexing on-board charging system, comprising:

[0006] Step 1: Based on the positive and negative sequence separation method of decoupling the dual synchronous coordinate system of the three-phase motor, the positive and negative sequence separation formula of the dual-channel six-phase motor is obtained. The positive and negative sequence of the dq axis current components of the dual-channel system under the condition of unbalanced charging current of the six phases is calculated using this formula.

[0007] Step 2: Use Park transform and VSD transform to convert the positive and negative order of the two sets of dq axis components to the αβxy0102 subplane;

[0008] Step 3: Set the positive sequence current setpoint using the six-phase current distribution method that minimizes electromagnetic torque, and set the negative sequence current setpoint to 0.

[0009] Step 4: Use a PI controller to independently control the positive and negative sequence currents of each subplane;

[0010] Step 5: Add the corresponding positive and negative sequence current outputs of each subplane, and then use T... VSD -1 After transforming to the natural coordinate system, input SPWM to realize the three-phase charging condition.

[0011] Furthermore, step 1 specifically includes:

[0012] The dual-channel symmetrical six-phase motor has two sets of three-phase windings with a phase difference of 60°. The two sets of windings are coupled to each other. The decoupling formula for the dual-synchronous coordinate system of the dual-channel symmetrical six-phase motor is expressed as follows:

[0013] First winding:

[0014]

[0015]

[0016] Second set of windings:

[0017]

[0018]

[0019] Eliminating the two pulses, we get:

[0020] First winding:

[0021]

[0022]

[0023] Second set of windings:

[0024]

[0025]

[0026] In the formula, This is the positive-sequence current with two pulsations along the dq axis. The negative sequence current with two pulsations along the dq axis. Here is the Park transformation matrix. Angular velocity, For the αβ plane current component, For the positive sequence components of the αβ plane current. This represents the negative sequence component of the αβ plane current. To eliminate the positive-sequence DC component after two pulsations on the dq axis. The negative sequence DC component after eliminating two pulsations on the dq axis. This is the positive sequence rotor position angle. This is the negative sequence rotor position angle. ; where the subscript "*" takes the value 1 or 2, the parameter corresponds to the first set of windings and the second set of windings, respectively.

[0027] Furthermore, step 2 specifically includes:

[0028] The positive and negative sequences of the two sets of channel dq-axis currents are converted into the positive and negative sequences of the six-phase winding currents through inverse Park transformation, as expressed by the formula:

[0029] First set of windings in the forward sequence:

[0030]

[0031] The second set of windings in the forward sequence:

[0032]

[0033] The first set of negative sequence windings:

[0034]

[0035] The second set of negative sequence windings:

[0036]

[0037] The positive and negative sequence of the six-phase winding currents is transformed to the αβxy0102 subplane via VSD, and the transformation matrix is ​​used. for:

[0038]

[0039] In the formula, , , These are the positive sequence components of the current in phases A, B, and C, respectively. , , These are the negative sequence components of the current on phases A, B, and C, respectively. , , These are the positive sequence components of the current on the U, V, and W phase windings, respectively. , , These are the negative sequence components of the current on the U, V, and W phase windings, respectively. This is the positive sequence rotor position angle. This is the negative sequence rotor position angle. , To eliminate the positive-sequence DC component after two pulsations along the d-axis. To eliminate the positive-sequence DC component after two pulsations on the q-axis. To eliminate the negative sequence DC component after two pulsations along the d-axis. The negative sequence DC component after eliminating two pulsations on the q-axis is used; where the subscript "*" is 1 and 2, the parameters correspond to the first set of windings and the second set of windings, respectively.

[0040] Furthermore, in step 3, the given values ​​for the positive and negative sequence of the αβxy0102 subplane current are expressed as follows:

[0041]

[0042] In the formula, This is the setpoint value for the output of the preceding voltage and current loop. This is the given value for the α-axis positive sequence current. This is the given value for the β-axis positive sequence current. This is the given value for the positive sequence current along the x-axis. This is the given value for the positive sequence current along the y-axis. This is the given value for the positive sequence current of the 0-1 axis. The given value for the positive sequence current is 02.

[0043] Beneficial effects: The method of this invention derives and calculates the positive and negative sequence of the current under the unbalanced current condition of the winding current of a six-phase motor by decoupling the positive and negative sequence of the three-phase motor dual synchronous coordinate system. Based on the calculated positive and negative sequence components, a PI controller is used to control the current, thereby suppressing the unbalanced current, improving the sinusoidal nature of the grid current, suppressing torque ripple, improving the steady-state performance of the system, and ensuring the safety of the system. Attached Figure Description

[0044] Figure 1 This is a topology diagram of a dual-channel electric drive multiplex vehicle charging system.

[0045] Figure 2 This is a control block diagram of the method of the present invention;

[0046] Figure 3 The positive and negative sequence currents separated from the first set of winding currents under current imbalance conditions without the introduction of a suppression strategy;

[0047] Figure 4 The three-phase grid current and phase A grid voltage are given without the introduction of a suppression strategy.

[0048] Figure 5 The torque waveform without the introduction of a suppression strategy;

[0049] Figure 6 The positive and negative sequence currents separated from the first set of winding currents under current imbalance conditions when a suppression strategy is introduced;

[0050] Figure 7 The three-phase grid current and A-phase grid voltage when a suppression strategy is introduced;

[0051] Figure 8 Torque waveform when a suppression strategy is introduced. Detailed Implementation

[0052] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0053] A method for suppressing unbalanced current in a dual-channel electric drive multiplexing on-board charging system is proposed. The topology of the dual-channel electric drive multiplexing on-board charging system described in this method is as follows: Figure 1 As shown, the control block diagram of this method is as follows: Figure 2 As shown, it includes the following steps:

[0054] Step 1: Based on the decoupling of the positive and negative sequence separation method of the three-phase motor dual synchronous coordinate system, the positive and negative sequence separation formula of the dual-channel six-phase motor is derived, and the positive and negative sequence of the dq axis current components of the dual-channel system under the condition of unbalanced six-phase charging current is calculated using this formula, specifically including:

[0055] Traditional methods for decoupling the positive and negative sequence of a three-phase motor using a dual-synchronous coordinate system only apply to one set of three-phase windings. However, for a dual-channel symmetrical six-phase motor with two sets of three-phase windings differing by 60°, mutual coupling between the two sets of windings is considered. The decoupling formula for the dual-synchronous coordinate system of a dual-channel symmetrical six-phase motor can be expressed as:

[0056] First winding:

[0057] (1)

[0058] (2)

[0059] Second set of windings:

[0060] (3)

[0061] (4)

[0062] Eliminating the two pulses, we get:

[0063] First winding:

[0064] (5)

[0065] (6)

[0066] Second set of windings:

[0067] (7)

[0068] (8)

[0069] In the formula, This is the positive-sequence current with two pulsations along the dq axis. The negative sequence current with two pulsations along the dq axis. Here is the Park transformation matrix. Angular velocity, , For the αβ plane current component, For the positive sequence components of the αβ plane current. This represents the negative sequence component of the αβ plane current. To eliminate the positive-sequence DC component after two pulsations on the dq axis. The negative sequence DC component after eliminating two pulsations on the dq axis. This is the positive sequence rotor position angle. This is the negative sequence rotor position angle. ; where the subscript "*" takes the value 1 or 2, the parameter corresponds to the first set of windings and the second set of windings, respectively.

[0070] Step 2: Use Park transform and VSD transform to convert the positive and negative order of the two sets of dq axis components to the αβxy0102 subplane, specifically including:

[0071] The positive and negative sequences of the two sets of channel dq-axis currents are transformed into the positive and negative sequences of the six-phase winding currents through inverse Park transformation, which can be expressed by the formula:

[0072] First set of windings in the forward sequence:

[0073] (9)

[0074] The second set of windings in the forward sequence:

[0075] (10)

[0076] The first set of negative sequence windings:

[0077] (11)

[0078] The second set of negative sequence windings:

[0079] (12)

[0080] The positive and negative sequence of the six-phase winding currents is transformed to the αβxy0102 subplane via VSD, and the transformation matrix is ​​used. for:

[0081] (13)

[0082] In the formula, , , These are the positive sequence components of the current in phases A, B, and C, respectively. , , These are the negative sequence components of the current on phases A, B, and C, respectively. , , These are the positive sequence components of the current on the U, V, and W phase windings, respectively. , , These are the negative sequence components of the current on the U, V, and W phase windings, respectively. This is the positive sequence rotor position angle. This is the negative sequence rotor position angle. , To eliminate the positive-sequence DC component after two pulsations along the d-axis. To eliminate the positive-sequence DC component after two pulsations on the q-axis. To eliminate the negative sequence DC component after two pulsations along the d-axis. The negative sequence DC component after eliminating two pulsations on the q-axis is used; where the subscript "*" is 1 and 2, the parameters correspond to the first set of windings and the second set of windings, respectively.

[0083] Step 3: Set the positive sequence current setpoint using the six-phase current distribution method that minimizes electromagnetic torque, and set the negative sequence current setpoint to 0. The positive and negative sequence setpoints for the subplane currents αβxy0102 can be expressed as:

[0084] Positive sequence given values ​​for αβxy0102 subplane currents:

[0085] (14)

[0086] In the formula, This is the setpoint value for the output of the preceding voltage and current loop. This is the given value for the α-axis positive sequence current. This is the given value for the β-axis positive sequence current. This is the given value for the positive sequence current along the x-axis. This is the given value for the positive sequence current along the y-axis. This is the given value for the positive sequence current of the 0-1 axis. The given value for the positive sequence current is 02.

[0087] Negative sequence given value of αβxy0102 subplane current:

[0088] (15)

[0089] Step 4: Use a PI controller to independently control the positive and negative sequence currents of each subplane.

[0090] Step 5: Add the corresponding positive and negative sequence current outputs of each subplane, and then use T... VSD -1 After transforming to the natural coordinate system, input SPWM to achieve three-phase charging operation.

[0091] The dual-channel three-phase charging control strategy includes two parts: constant voltage and constant current control of the battery and sub-plane current control. For example... Figure 2 As shown, the output value of the dual-channel constant voltage and constant current charging control is used as the amplitude of the sub-plane current setpoint. The positive sequence current setpoint is output through the current calculation module, while the negative sequence current setpoint is set to 0. Using a Park transformation and a dual synchronous coordinate system decoupling method for positive and negative sequence separation, the positive and negative sequences of the two winding dq-axis components are output separately. Then, through inverse Park transformation and VSD transformation, the current is transformed to the αβxy0102 sub-plane, and the positive and negative sequence currents are controlled to reach the setpoints through 12 current PI controllers. Finally, the inverse transformation matrix T... VSD -1 The voltage values ​​output by the 12 current PI controllers are transformed into a natural coordinate system, and the positive and negative values ​​are added together. The output values ​​are then modulated by PWM to generate gate drive signals.

[0092] To compare the grid current under three-phase charging conditions before and after applying positive and negative sequence current suppression, a simulation of the three-phase charging condition was performed in Simulink. The effective value of the grid voltage was set to 40V, the grid frequency to 50Hz, the rated voltage of both battery packs to 144V, the rated capacity to 30Ah, and the initial charge to 95% for both.

[0093] Figure 3 The positive and negative sequence currents separated from the first winding current under the current imbalance condition without the introduction of a suppression strategy are shown. It can be seen that both the positive and negative sequence currents of the dq axis have pulsations, and the negative sequence current is not 0.

[0094] Figure 4 The diagram shows the three-phase grid current and phase A grid voltage without the introduction of a suppression strategy. It can be seen that the phase A grid voltage and phase A grid current are in phase, and the three-phase grid currents A, B, and C have harmonics, and their amplitudes are no longer balanced.

[0095] Figure 5 The torque waveform without the introduction of a suppression strategy shows that the torque pulsation under unbalanced current has a third harmonic with an amplitude of approximately 0.5A.

[0096] Figure 6 The figure shows the positive and negative sequence currents separated from the first winding current under the current imbalance condition when the suppression strategy is introduced. As can be seen from the figure, the negative sequence current is 0, the current ripple is basically eliminated, and the current imbalance is suppressed.

[0097] Figure 7The figure shows the three-phase grid current and phase A grid voltage when the suppression strategy is introduced. As can be seen from the figure, the phase A grid voltage and phase A grid current are in phase, the harmonics of the three-phase grid A, B, and C are reduced, and the current amplitude is balanced.

[0098] Figure 8 The torque waveform is shown when the suppression strategy is introduced, and compared. Figure 5 It can be seen that the torque ripple is about 15% of the original value, and the ripple torque is basically eliminated, indicating that the positive and negative sequence current suppression strategy can effectively suppress torque ripple.

[0099] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for suppressing unbalanced current in a dual-channel electric drive multiplex type vehicle-mounted charging system, characterized in that, Comprise: Step 1: the positive and negative sequence separation formula of the dual-channel six-phase motor is derived based on the positive and negative sequence separation method of the dual synchronous coordinate system decoupling of the three-phase motor, and the formula is used to calculate the positive and negative sequence of the dq axis current components of the dual-channel system under the unbalanced working condition of the six-phase charging current; Step 2: the positive and negative sequence of the two sets of dq axis components are converted to the αβxy0102 subplane by using Park transformation and VSD transformation; Step 3: the positive sequence current given value is set by using the six-phase current distribution method of electromagnetic torque minimization, and the given value of the negative sequence current is 0; Step 4: PI controllers are used to independently control the positive and negative sequence currents of each subplane; Step 5: The output of each sub-plane positive and negative sequence current is added to the corresponding phase, and the T VSD -1 After transformation to the natural coordinate system, input SPWM, and realize three-phase charging conditions.

2. The method according to claim 1, wherein, The step 1 specifically comprises: The dual-channel symmetric six-phase motor has two sets of three-phase windings with a phase difference of 60° angle, and the two sets of windings are coupled with each other, and the dual synchronous coordinate system decoupling formula of the dual-channel symmetric six-phase motor is expressed as: The first set of windings: (1) (2) The second set of windings: (3) (4) Eliminate 2 times pulsation, get: The first set of windings: (5) (6) The second set of windings: (7) (8) wherein is the positive sequence current with 2nd pulsation on dq axis, is the negative sequence current with 2nd pulsation on dq axis, is the Park transformation matrix, is the angular velocity, is the current component on αβ plane, is the positive sequence component on αβ plane, is the negative sequence component on αβ plane, is the positive sequence direct current component on dq axis after eliminating 2nd pulsation, is the negative sequence direct current component on dq axis after eliminating 2nd pulsation, is the positive sequence rotor position angle, is the negative sequence rotor position angle, ; wherein the subscript "*" takes 1 or 2, and the parameters correspond to the first set of windings and the second set of windings, respectively.

3. The method of claim 1, wherein the method is characterized by: The step 2 specifically comprises: The positive and negative sequence of the two sets of channel dq axis currents are converted to the positive and negative sequence of the six-phase winding current by inverse Park transformation, and the formula is expressed as: Positive sequence first set of windings: (9) Positive sequence second set of windings: (10) Negative sequence first set of windings: (11) Negative sequence second set of windings: (12) The positive and negative sequence of the six-phase winding current is converted to the αβxy 0102 sub-plane through the VSD, and the transformation matrix is: (13) wherein, , , are positive sequence components of the currents on the A, B, C phase windings, respectively, , , are negative sequence components of the currents on the A, B, C phase windings, respectively, , , are positive sequence components of the currents on the U, V, W phase windings, respectively, , , are negative sequence components of the currents on the U, V, W phase windings, respectively, is a positive sequence rotor position angle, is a negative sequence rotor position angle, , is a d-axis positive sequence direct current component after eliminating 2nd pulsation, is a q-axis positive sequence direct current component after eliminating 2nd pulsation, is a d-axis negative sequence direct current component after eliminating 2nd pulsation, is a q-axis negative sequence direct current component after eliminating 2nd pulsation; wherein the subscript "*" takes 1 or 2, and the parameters correspond to the first set of windings and the second set of windings, respectively.

4. The method of claim 1, wherein the method is characterized by: In the step 3, the given value of the αβxy0102 subplane current positive and negative sequence is expressed as: (14) wherein is a given value of the output of the front stage voltage current loop, is a given value of the α-axis positive-sequence current, is a given value of the β-axis positive-sequence current, is a given value of the x-axis positive-sequence current, is a given value of the y-axis positive-sequence current, is a given value of the 01-axis positive-sequence current, is a given value of the 02 positive-sequence current.

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