A dual-vector MPC method for six-phase electric drive reconfigurable on-board charging system

Abstract

The application provides a kind of six-phase electric drive reconfiguration type vehicle charging system double-vector MPC method, belongs to the field of power electronics and electric drive technology.Solve the problem of heavy computing burden, low voltage utilization rate.The technical scheme is as follows:including the following steps:S1: according to the acquisition value and through MPPT controller and speed controller, the current given value is obtained;S2: the current value of each axis at time k is obtained by decoupling;S3: the voltage vector group of double vector model predictive controller is established, and the predicted current is calculated;S4: select the voltage vector used in the next cycle, realize six-phase electric drive reconfiguration type vehicle charging system side running while charging control.The beneficial effects of the application are:the application can improve the current and torque control accuracy, reduce the current and torque ripple, reduce the system computing burden, improve the voltage utilization rate, and has wide application prospect.

Description

Technical Field

[0001] This invention relates to the fields of power electronics and electric drive technology, and in particular to a dual-vector MPC method for a six-phase electric drive reconfigurable on-board charging system. Background Technology

[0002] With the increasing prominence of traffic environment problems, electric vehicles have received widespread attention in road transportation in recent years. However, due to the limited energy density of batteries and the low deployment density of high-power fast electric vehicle charging piles, the unsatisfactory driving range and inconvenient charging remain the main obstacles to the promotion of electric vehicles. The paper: Feng Yu, Zhihao Zhu, Xing Liu and Zhen Zhang. Electric-Drive-Reconstructed Onboard Charger for Solar-Powered Electric Vehicles Incorporating Six-Phase Machine[J].IEEE Transactions on Power Electronics,2022,37(6):6544-6555. records that the continuous expansion of the applicability of photovoltaic energy has made it possible to apply photovoltaic power generation technology to the field of electric vehicles. However, the integration of photovoltaic charging mode not only requires additional power devices to match the voltage level of the power battery, but also increases the complexity of the control algorithm. Therefore, the research on the control algorithm of onboard charging system is indispensable.

[0003] In multiphase electric drive reconfigurable on-board charging systems, while traditional charging control methods can effectively adapt to photovoltaic charging modes, Multi-Planetary Charge (MPC) is generally considered a more competitive method due to its advantages such as fast response, ease of incorporating nonlinearity, and flexible design. MPC primarily controls the current in multiple subspaces simultaneously through a cost function, but inevitably comes at the cost of increased computation time and additional parameters to suppress harmonics. Furthermore, to improve the evaluation performance of the cost function, the design of weight factor adjustment needs to be considered. The patent title, "A Unified Single / Dual Vector MPC Method and Device for Permanent Magnet Motors" (CN106357188B), describes a single-vector MPC that operates on only one optimal voltage vector in a single sampling period. While the algorithm is simple and has a fast response, its current tracking accuracy is poor because it can only select control quantities from the inherent basic voltage vector, and it cannot guarantee that the optimal voltage vector remains optimal after incorporating the duty cycle.

[0004] Therefore, to address the challenges of multi-parameter tuning difficulties, excessive computation time, and the need to control multiple subspaces inherent in the single-vector MPC method, a dual-vector MPC strategy is introduced. This strategy selects two voltage vectors simultaneously in each control cycle, thereby improving current and torque control accuracy and reducing ripple. The commonly used dual-vector MPC strategy helps improve the dynamic and steady-state control performance of permanent magnet synchronous motors when applied in multiphase electric drive reconfigurable on-board charging systems, but it also suffers from high computational complexity. Summary of the Invention

[0005] The purpose of this invention is to provide a dual-vector MPC method for a six-phase electric drive reconfigurable on-board charging system. This method can improve the accuracy of current and torque control, reduce the work of PI parameter optimization and tuning, reduce current and torque ripple, alleviate the system's computational burden, and improve voltage utilization.

[0006] To achieve the above-mentioned objectives, the present invention employs the following technical solution: the positive terminal of the photovoltaic panel is connected to the neutral point O1 of the winding phases ABC of the six-phase symmetrical permanent magnet synchronous motor, the negative terminal of the photovoltaic panel is connected to the neutral point O2 of the winding phases UVW of the six-phase symmetrical permanent magnet synchronous motor, a mode switch SW is connected between the positive terminal of the photovoltaic panel and the neutral point O1 of the motor, the winding ports of the six-phase symmetrical permanent magnet synchronous motor are connected to the six-phase inverter, and the six-phase inverter is controlled by a dual-vector model predictive controller.

[0007] A dual-vector MPC method for a six-phase electric drive reconfigurable on-board charging system includes the following steps:

[0008] S1: Collects the output voltage V of the photovoltaic panel P With output current I P The setpoint value i of the 01 axis current is calculated by the MPPT controller. 01 * Control the 01 axis current to stably charge the battery; according to the motor speed set value n * The actual motor speed n is collected, and the q-axis current setpoint i is obtained by the speed controller. q * Controlling the q-axis current stabilizes the rotational speed;

[0009] S2: The actual phase current I of the six-phase symmetrical motor will be collected. A I B I C I U I V I W By decoupling coordinate transformations in vector space, the d-axis, q-axis, and 0 / 1-axis current values ​​i at time k are obtained. d (k), i q (k), i 01(k) provides prerequisites for calculating the predicted current;

[0010] S3: Use the base voltage vector and the virtual vector as the voltage vector group of the two-vector model predictive controller, and use the current value i at the current moment. d (k), i q (k), i 01 (k) is input into the dual-vector model predictive controller, and the predicted current i corresponding to each voltage vector is calculated using the discretization formula. d (k+1),i q (k+1),i 01 (k+1) is used as the calibration for the current value at the next moment;

[0011] S4: Compare the different predicted currents with the given reference value i q * , i 01 * The input is fed into the value function to select the base voltage vector or virtual voltage vector to be used in the next cycle, thereby obtaining the on / off state of the switching transistors in the next cycle. This is used as the drive signal for the six-phase inverter, ultimately realizing the integration of the charging mode, drive mode and on-the-go charging mode of the six-phase electric drive reconfigurable on-board charging system.

[0012] As a preferred embodiment of the present invention, in step S3, the voltage vector group in the dual-vector model predictive controller consists of the zero vector V0, the base voltage large vector V0, and the base voltage large vector V0. Li With virtual vector V Si Composition, due to the spatially adjacent base voltage large vector V of the six-phase symmetrical permanent magnet synchronous motor Li The projections in the xy subspace are of equal size and opposite direction, therefore the virtual vector V Si The large vector V of two spatially adjacent base voltages with the same duration of action Li Obtained through synthesis.

[0013] As a preferred embodiment of the present invention, in step S4, the voltage vector selected in the dual-vector model does not contain harmonic components of the xy subspace, and the 0-axis and 1-axis currents need to be controlled. Therefore, the value function is modified to be expressed as:

[0014]

[0015] In the formula, i q * , i 01 * Provide current values ​​for the d-axis, q-axis, and 0 / 1-axis, where i d * Always keep it at 0; i d(k+1),i q (k+1),i 01 (k+1) represents the predicted current corresponding to each voltage vector; m is the value weight coefficient, and its value ranges from 0 to 1.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] (1) Compared with the traditional SVPWM control scheme, which is more complicated to control multiple subspaces in a six-phase electric drive reconfigurable vehicle charging system and requires parameter tuning of multiple PI controllers, the dual vector MPC scheme adopted in this invention uses only one PI regulator in the speed controller and can use the value function to control multiple subspaces, simplifying the control process and shortening the parameter tuning time.

[0018] (2) Compared with the traditional single-vector MPC, which has problems such as heavy computational burden and low voltage utilization, the dual-vector MPC used in this invention uses a voltage vector group composed of a basic voltage large vector and a virtual vector. The harmonic components in the xy subspace are equivalent to 0, and only 13 voltage vectors need to be selected, which greatly reduces the complexity of the algorithm and effectively reduces the computational burden, thereby improving the steady-state performance of the system.

[0019] (3) The dual-vector MPC method of the six-phase electric drive reconfigurable on-board charging system proposed in this invention has two voltage vectors with equal durations acting within one control cycle when the system is running in the state of running and charging. This overcomes the defect of traditional model predictive control methods that require calculation of vector action time when synthesizing virtual vectors, simplifies the control difficulty, and improves the versatility and practicality of model predictive control methods. It is an important improvement to the existing technology. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0021] Figure 1 This is a block diagram illustrating the principle of a dual-vector MPC method for a six-phase electric drive reconfigurable on-board charging system according to the present invention.

[0022] Figure 2 This is a simplified circuit topology diagram of the six-phase electric drive reconfigurable on-board charging system in this invention;

[0023] Figure 3 This is a vector diagram of 64 voltages in the α-β subspace of the six-phase inverter in this invention;

[0024] Figure 4 This is a schematic diagram of the virtual vector synthesized in this invention;

[0025] Figure 5 This refers to the voltage vector group of the dual-vector model predictive controller in this invention;

[0026] Figure 6 This is a schematic diagram of the simulation results of motor speed and torque in this invention;

[0027] Figure 7 This is a schematic diagram of the simulation results of the photovoltaic panel output voltage and current in this invention;

[0028] Figure 8 This is a schematic diagram of the simulation results of the d-axis and q-axis currents in this invention;

[0029] Figure 9 This is a schematic diagram of the battery capacity simulation results in this invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Of course, the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0031] Example 1

[0032] The present invention provides a technical solution as follows: a model of a six-phase electric drive reconfigurable on-board charging system, the principle block diagram of which is shown below. Figure 1 As shown, the positive terminal of the photovoltaic panel is connected to the neutral point O1 of the winding phases ABC of the six-phase symmetrical permanent magnet synchronous motor, and the negative terminal of the photovoltaic panel is connected to the neutral point O2 of the winding phases UVW of the six-phase symmetrical permanent magnet synchronous motor. A mode switch SW is connected between the positive terminal of the photovoltaic panel and the neutral point O1 of the motor. The winding ports of the six-phase symmetrical permanent magnet synchronous motor are connected to the six-phase inverter, and the six-phase inverter is controlled using the MPC method.

[0033] like Figure 1 As shown, a dual-vector MPC method for a six-phase electric drive reconfigurable on-board charging system includes the following steps:

[0034] Step 1: Collect the output voltage V of the photovoltaic panel P With output current I P The setpoint value i of the 01 axis current is calculated by the MPPT controller. 01 * According to the motor speed setting value n * The actual motor speed n is collected, and the q-axis current setpoint i is obtained by the speed controller. q * Specifically:

[0035] The output voltage V of the solar panel P Output current IP The input is fed into the MPPT controller, where the optimal output current value of the photovoltaic panel is obtained through a maximum power point tracking algorithm based on the perturbation and observation method. This current value is then used as the 0-axis and 1-axis current setpoint i. 01 * The speed setpoint n of the six-phase symmetrical permanent magnet synchronous motor. * The difference between the collected six-phase symmetrical permanent magnet synchronous motor speed n and the actual speed n is used by a speed PI controller to obtain the real-time q-axis current setpoint i. q * .

[0036] Step 2: Collect the actual phase current I of the six-phase symmetrical motor A I B I C I U I V I W By decoupling coordinate transformations in vector space, the d-axis, q-axis, and 0 / 1-axis current values ​​i at time k are obtained. d (k), i q (k), i 01 (k), specifically:

[0037] The actual phase current of a six-phase symmetrical motor is represented by vector space decoupling coordinate transformation, transforming the various variables of the natural coordinate system into components of the α-β axis, xy axis, and 01 axis as follows:

[0038]

[0039] In the formula, the transformation matrix T VSD Represented as:

[0040]

[0041] To control the electromechanical energy of the motor, it is necessary to simplify the transformation from the stationary coordinate system to the synchronous coordinate system, thus obtaining the components of the dq subspace as follows:

[0042] [i d i q ] T =T dq [i α i β ] T (2)

[0043] In the formula, the Park transformation matrix T dq Represented as:

[0044]

[0045] Where, θ e The value is the electrical angle of the rotor position.

[0046] Based on this, the current obtained through vector space decoupled coordinate transformation and Park transformation is used as the d-axis, q-axis, and 0 / 1-axis current values ​​i at time k. d (k), i q (k), i 01 (k), the obtained current value will be updated at the beginning of each control cycle.

[0047] Step 3: Combine the base voltage vector and the virtual vector as the voltage vector group of the dual-vector model predictive controller, and set the current value i at the current moment. d (k), i q (k), i 01 (k) is input into the dual-vector model predictive controller, and the predicted current i corresponding to each voltage vector is calculated using the discretization formula. d (k+1),i q (k+1),i 01 (k+1), specifically:

[0048] The six-phase symmetrical permanent magnet synchronous motor used in this invention has two sets of windings with a spatial offset angle difference of 60°, and each bridge arm of the six-phase inverter has two operating states, for a total of 64 operating states. The 64 voltage vectors of the six-phase inverter in the α-β subspace are as follows: Figure 3 As shown. Among them, the base voltage large vector V Li There are 6 in total, namely V7, V14, V28, V35, V49, and V56, represented as follows:

[0049]

[0050] In the formula, V Li This represents the components of the six fundamental voltage vectors along the α-β axis, x-y axis, and 0-1 axis, i = 1, 2, ..., 6, V DC V represents the voltage across the battery terminals. p S(j,i) represents the voltage across the photovoltaic panel, and S(j,i) represents the selected voltage vector V. i The corresponding six-phase inverter switching states are represented as follows:

[0051]

[0052] After calculation using formula (3), the component of the base voltage vector in the xy subspace is 0. Therefore, in the following calculations, the component on the xy axis will no longer be controlled.

[0053] The virtual vector V Si The large vector V of two spatially adjacent base voltages with the same duration of action Li The synthesized i = 1, 2, ..., 6, with Figure 4 For example, virtual vector V S6 It is synthesized based on the large vectors of the base voltages V49 and V56. According to formula (3), the large vectors of the base voltages V49 and V56 can be expressed as follows:

[0054]

[0055] According to formula (4), the duration of action of the two base voltage vectors is the same within one control cycle. The virtual vector synthesized using the parallelogram principle is represented as follows:

[0056]

[0057] According to formulas (3), (4), and (5), the representations of the six virtual vectors can be obtained. These six virtual vectors, the six basic voltage vectors, and one zero vector form a voltage vector group, as shown below. Figure 5 As shown, it serves as the voltage vector selection group for the dual-vector model predictive controller.

[0058] Formula (5) clearly shows that the synthesized virtual vector has zero components in the xy subspace, meaning that the application of the virtual vector will not generate a large number of harmonics that would affect the electromechanical energy of the motor. When the photovoltaic panel is not connected to the neutral point of the motor, the virtual vector has zero components in the zero-sequence space and will not affect the normal operation of the motor.

[0059] The current value i at the current moment d (k), i q (k), i 01 (k) After inputting into the dual-vector model predictive controller, since the vectors used have no components in the xy subspace, there is no need to solve for the predicted current value in the xy subspace. Then, the predicted current i corresponding to each voltage vector is calculated using the current discretization formula. d (k+1),i q (k+1),i 01 (k+1), represented as:

[0060]

[0061] In the formula, R s The stator internal resistance of a six-phase symmetrical permanent magnet synchronous motor; L d The d-axis inductance of a six-phase symmetrical permanent magnet synchronous motor; L q L0 is the q-axis inductance of the six-phase symmetrical permanent magnet synchronous motor; L0 is the leakage inductance of the six-phase symmetrical permanent magnet synchronous motor; ω e The electric angular velocity of the three-phase permanent magnet synchronous motor; Indicates permanent magnet flux linkage; T s Indicates the sampling period. u d uq u 01 This represents the reference voltage values ​​for the d-axis, q-axis, and 01-axis corresponding to each voltage vector.

[0062] Step 4: Compare the different predicted currents with the given reference value i q * , i 01 * The input is fed into the value function to select the base voltage vector or virtual voltage vector for the next cycle, thereby obtaining the on / off state of the switching transistors in the next cycle. This is then used as the drive signal for the six-phase inverter, ultimately integrating the charging mode, drive mode, and on-the-go charging mode of the six-phase electric drive reconfigurable on-board charging system. Specifically:

[0063] The predicted current corresponding to each voltage vector is compared with the given reference value i. q * , i 01 * The input is fed into the value function, and the value result of the voltage vector is calculated by formula (7). The voltage vector corresponding to the minimum value is selected as the voltage vector acting in the next cycle, and then the switching state of the switch tube in the next cycle is obtained. It is used as the driving signal of the six-phase inverter, thereby realizing the control of the d-axis, q-axis and 01-axis in the six-phase electric drive reconfigurable vehicle charging system.

[0064]

[0065] In the formula, i q * , i 01 * Provide current values ​​for the d-axis, q-axis, and 0 / 1-axis, where Always keep it at 0; i d (k+1),i q (k+1),i 01 (k+1) represents the predicted current corresponding to each voltage vector; m is the value weight coefficient, and its value ranges from 0 to 1.

[0066] When the system is operating in normal driving mode, the value weight coefficient is 0; when the system is operating in running-while-charging mode or charging mode, the value weight coefficient is between 0 and 1.

[0067] To verify the technical problem of the present invention, based on Figure 2The simplified circuit topology of the six-phase electric drive reconfigurable on-board charging system shown is presented. Simulation verification of the dual-vector MPC method for this proposed six-phase electric drive reconfigurable on-board charging system under a running-while-charging mode is performed. In this embodiment, the maximum output power of the solar panel is 800W, and a 50AH / 144V lithium battery is used. The motor speed is set from 500r / min to 1000r / min at 0.5s.

[0068] In this invention, the motor speed n and torque T are simulated. e The results are as follows Figure 6 As shown, the motor speed can quickly follow the given value at 0.5s and complete the speed adjustment within 0.03s. During the speed adjustment process, the motor output torque recovers rapidly, completing the motor speed adjustment. Under stable conditions, the motor output torque is constant at 2 N·m. Battery current I b Voltage V b 01 axis current i 01 Simulated waveforms such as Figure 7 As shown, throughout the process, the battery voltage V b A fluctuation occurs at 0.5s and returns to steady state within 0.02s. However, due to the increase in motor speed, the energy consumed by the motor increases, the battery charging current changes from -2A to 1.5A, and the battery transitions from a charging state to a discharging state. During the motor speed adjustment process, the fluctuation of the 01-axis current increases, and the steady-state performance of the 01-axis current changes with the increase in speed. The simulation diagrams of the d-axis and q-axis currents are shown below. Figure 8 As shown, under stable rotational speed conditions, the q-axis current i q Keep it at 0, d-axis current i d Maintaining an A of 3A, after an increase in rotational speed over 0.5 seconds, the d-axis and q-axis currents quickly return to their original values. The simulated battery capacity waveform is as follows: Figure 9 As shown, it can be seen that the battery capacity is constantly increasing when the motor is running normally. At this time, the photovoltaic panel charges the battery through the zero-sequence channel. After the speed increases in 0.5 seconds, the battery capacity decreases, indicating that the system can charge the battery in normal electric drive mode, realizing the system can run and charge at the same time.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dual-vector MPC method for a six-phase electric drive reconfigurable on-board charging system, characterized in that, Includes the following steps: S1: Collects the output voltage V of the photovoltaic panel P With output current I P The setpoint value i of the 01 axis current is calculated by the MPPT controller. 01 * According to the motor speed setting value n * The actual motor speed n is collected, and the q-axis current setpoint i is obtained by the speed controller. q * ; S2: The actual phase current I of the six-phase symmetrical motor will be collected. A I B I C I U I V I W By decoupling coordinate transformations in vector space, the d-axis, q-axis, and 0 / 1-axis current values ​​i at time k are obtained. d (k), i q (k), i 01 (k); S3: The six-phase inverter has 64 voltage vectors in the α-β subspace, including 6 basic large voltage vectors; these basic large voltage vectors and the virtual vectors are used as the voltage vector group of the dual-vector model predictive controller, and the current value i at the current moment is used as the voltage vector group. d (k), i q (k), i 01 (k) is input into the dual-vector model predictive controller, and the predicted current i corresponding to each voltage vector is calculated using the discretization formula. d (k+1),i q (k+1),i 01 (k+1); In step S3, the voltage vector group in the dual-vector model predictive controller consists of the zero vector V0, the base voltage large vector V0, and the base voltage large vector V0. Li With virtual vector V Si Composition; the virtual vector V Si The large vector V of two spatially adjacent base voltages with the same duration of action Li Obtained through synthesis; S4: Compare the different predicted currents with the given reference value i q * i d * i 01 * The input is fed into the value function to select the base voltage vector or virtual voltage vector to be used in the next cycle, thereby obtaining the on / off state of the switching transistors in the next cycle. This is used as the drive signal for the six-phase inverter, ultimately realizing the integration of the charging mode, drive mode and on-the-go charging mode of the six-phase electric drive reconfigurable on-board charging system.

2. The dual-vector MPC method for a six-phase electric drive reconfigurable on-board charging system according to claim 1, characterized in that, In step S4, the voltage vector selected in the dual-vector model does not contain harmonic components of the xy subspace, and the 0-axis and 1-axis currents need to be controlled. Therefore, the value function is expressed as: (1) In the formula, i q * i d * i 01 * These are the current setpoints for the q-axis, d-axis, and 0 / 1-axis, respectively, where i d * Always keep it at 0; i d (k+1),i q (k+1),i 01 (k+1) represents the predicted current corresponding to each voltage vector; m is the value weight coefficient, and its value ranges from 0 to 1.

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