Double-neutral-point series power supply dual-motor control system

Abstract

The invention provides a dual-neutral-point series power supply dual-motor control system. The dual-neutral-point series power supply dual-motor control system comprises a boost controller, a boost distributor, a first driving controller, a second driving controller, a first modulator and a second modulator, the boost controller outputs an equivalent duty ratio by tracking a target DC bus voltage; the boost distributor uses a preset distribution strategy to distribute the equivalent duty ratio as the average duty ratio of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor; the two driving controllers respectively generate driving control quantities of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor; the two modulators respectively generate actual control signals of the two permanent magnet synchronous motors and carry out closed-loop control on inverters of the two permanent magnet synchronous motors. According to the dual-motor control system provided by the invention, linkage closed-loop control can be carried out on the two permanent magnet synchronous motors of which the double neutral points are connected in series for power supply.

Description

Technical Field

[0001] The present application belongs to the field of electric vehicle electric drive control technology, and relates to dual-motor drive control technology. Specifically, a dual-motor control system with dual neutral point series power supply is provided. Background Art

[0002] Dual-motor drive is a new type of electric drive mode for electric vehicles. When dual-motor drive is used, the sum of the power of the two permanent magnet synchronous motors does not need to reach the power of a single motor to exceed the performance of a single motor. Different coupling methods (torque, speed, dual coupling) can be used to significantly expand the high efficiency range of the system, thereby improving the efficiency of the motor under high speed and light load conditions. In addition, since the two permanent magnet synchronous motors can independently drive the wheels on both sides, the speed difference between the wheels and the power distribution adjustment can be used to assist the vehicle steering, thereby greatly improving the sport characteristics.

[0003] Most of the existing dual-motor drive solutions currently use DC / DC converters to boost the power supply voltage. The boosting principle of this solution is intuitive and easy to implement, but it will add additional devices such as switching tubes and inductors, resulting in an increase in the complexity and size of the dual-motor drive system. In addition, a dual-neutral point series power supply topology can also be used to achieve dual-motor drive. However, the existing research has not conducted in-depth research on its boosting mechanism, so the control of the three-phase current of the two motors uses simple open-loop control, and it cannot guarantee independent and stable torque control of the two motors while boosting the voltage. Summary of the invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the present application provides a dual-motor control system with dual neutral point series power supply, which is used to perform closed-loop joint control on a first permanent magnet synchronous motor and a second permanent magnet synchronous motor using dual neutral point series power supply, wherein the positive and negative poles of the power supply are respectively connected to the neutral points of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor, and the two permanent magnet synchronous motors have the same DC bus voltage. The control system includes:

[0005] A boost controller, a boost distributor, a first drive controller, a second drive controller, a first modulator and a second modulator;

[0006] The boost controller outputs an equivalent duty cycle by tracking the target DC bus voltage;

[0007] The boost distributor distributes the equivalent duty cycle as an average duty cycle of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor using a preset distribution strategy;

[0008] The first drive controller and the second drive controller respectively generate drive control quantities of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor by tracking the target torque;

[0009] The first modulator and the second modulator respectively generate actual control signals of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor based on the average duty cycle and the drive control amount, and use the actual control signals to perform closed-loop control on the inverters of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor respectively.

[0010] Furthermore, the boost controller is a voltage-current dual-loop controller, and its control parameters are determined by the following steps:

[0011] S1, establish the boost expression under the double neutral point series power supply structure;

[0012] S2, establishing an equivalent boost model under a double neutral point series power supply structure based on the boost expression;

[0013] S3, obtaining a small signal mathematical model of the equivalent boost model;

[0014] S4, determining voltage loop control parameters and current loop control parameters of the boost controller based on the small signal mathematical model of the equivalent boost model.

[0015] Furthermore, the voltage boost expression under the double neutral point series power supply structure is established through the following steps:

[0016] Based on the circuit topology and average theory of the double neutral point series power supply structure, the 0-axis voltage expression of the two permanent magnet synchronous motors is determined:

[0017]

[0018] Among them, u bus is the DC bus voltage, N 1 、N 2 are the neutral points of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor respectively, O is the grounding point, R S1 are the 0-axis duty cycle, 0-axis voltage, neutral point potential, 0-axis current, 0-axis inductance and stator resistance of the first permanent magnet synchronous motor, respectively. R S2 are the 0-axis duty cycle, 0-axis voltage, neutral point potential, 0-axis current, 0-axis inductance and stator resistance of the second permanent magnet synchronous motor respectively;

[0019] Based on equal power conversion, the expression of the relationship between the 0-axis current and the neutral line current of the two permanent magnet synchronous motors and the expression of the relationship between the average duty cycle of the three-phase inverter and the 0-axis duty cycle are determined:

[0020]

[0021] Among them, i Nis the neutral current, are the average duty cycles of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor respectively;

[0022] The expression for determining the neutral point potential of two permanent magnet synchronous motors is:

[0023]

[0024] The expression of the power supply voltage under the double neutral point series power supply structure is established as shown in the following formula:

[0025]

[0026] Among them, u in is the power supply voltage;

[0027] Ignoring the differential term and stator resistance voltage drop in steady state, the boost expression under the double neutral point series power supply structure is obtained as shown in the following formula:

[0028]

[0029] where Δα h is the equivalent duty cycle.

[0030] Preferably, the equivalent boost model under the double neutral point series power supply structure includes an equivalent resistor R, an equivalent capacitor C, a first equivalent inverter unit, a second equivalent inverter unit, a first equivalent zero axis resistor R 1 , the second equivalent zero axis resistance R 2 , the first equivalent zero-axis inductance L 1 and the second equivalent zero-axis inductance L 2 ;

[0031] The first equivalent inverter unit includes a first upper switch tube A H and the first lower switch tube A L The second equivalent inverter unit includes a second upper switch tube B H And the second lower switch tube B L ;

[0032] Among them, the first end of the equivalent resistor R, the first end of the equivalent capacitor C, the first upper switch tube A H The first end of the second upper switch B H The first ends of the tubes are connected to each other, the second end of the equivalent resistor R, the second end of the equivalent capacitor C, the first lower switch tube A L The second end of the second lower switch tube B L The second ends of the

[0033] The first upper switch tube A H The second end of the first lower switch tube A LThe first end is connected to the second upper switch tube B H The second end of the second lower switch tube B L The first end is connected to the first equivalent zero axis resistor R 1 , the first equivalent zero-axis inductance L 1 , the second equivalent zero-axis inductance L 2 , the second equivalent zero axis resistance R 2 The transistors are connected in series between the second end of the first upper switch tube and the second end of the second upper switch tube.

[0034] Furthermore, step S3 performs instantaneous value averaging operation, disturbance separation operation and linearization operation on the equivalent boost model under the double neutral point series power supply structure to obtain a small signal mathematical model of the equivalent boost model as shown in the following formula:

[0035]

[0036] in, are the AC components of the DC bus voltage, DC bus current, power supply voltage, duty cycle of the first equivalent inverter unit, and duty cycle of the second equivalent inverter unit in the small signal mathematical model, V, I, and D 1 , D 2 are the DC bus voltage, DC bus current, the first equivalent inverter unit duty cycle, and the DC component of the second equivalent inverter unit duty cycle in the small signal mathematical model, and V is the same as the power supply voltage V in the small signal mathematical model. g The following relations are satisfied:

[0037]

[0038] Further, step S4 includes the following steps:

[0039] The small signal mathematical model of the equivalent boost model is Laplace transformed:

[0040]

[0041] Where s is the independent variable of Laplace transform;

[0042] Based on the result of pull-type conversion, the transfer function G from the output voltage to the difference in duty cycle of the two inverter units is obtained as shown in the following formula: vd (s), and the transfer function G from the power supply current to the difference in duty cycle of the two inverter units id (s):

[0043]

[0044] make Determine the output voltage to supply current transfer function G as shown below vi(s):

[0045]

[0046] Establish the current loop open-loop transfer function G as shown below 1 (s) and the voltage loop open-loop transfer function G 2 (s):

[0047]

[0048] Set the desired crossover frequency f c_i 、f c_v and phase margin Solve the following equation to obtain the voltage loop control parameter k of the boost controller: v_p , k v_i and current loop control parameter k i_p , k i_i :

[0049]

[0050] Here, j is an imaginary unit.

[0051] Preferably, the equivalent duty cycle is allocated as an average duty cycle of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor using a preset allocation strategy, specifically:

[0052] Centered on 0.5, the average duty cycle of the first permanent magnet synchronous motor and the average duty cycle of the second permanent magnet motor They are respectively distributed as 0.5+Δα h / 2 and 0.5-Δα h / 2.

[0053] Furthermore, the actual control signal of the first permanent magnet synchronous motor is shown in the following formula:

[0054]

[0055] in, are respectively actual duty cycle signals for controlling phases A, B, and C of the inverter of the first permanent magnet synchronous motor, A, B, and C phase drive control quantities of the inverter of the first permanent magnet synchronous motor generated by the first drive controller respectively;

[0056] The actual control signal of the second permanent magnet synchronous motor is shown as follows:

[0057]

[0058] in, are respectively actual duty cycle signals for controlling phases A, B, and C of the inverter of the second permanent magnet synchronous motor, The A, B, and C phase drive control quantities of the inverter of the second permanent magnet synchronous motor are respectively generated by the second drive controller.

[0059] An embodiment of the present application provides a dual-motor control system with dual neutral point series power supply. First, the target DC bus voltage is tracked through a boost controller to output an equivalent duty cycle. Since the equivalent duty cycle is related to the difference between the average duty cycles of the inverters on both sides, a wider boost range can be obtained compared to a single neutral point boost structure. Then, a boost distributor is used to distribute the equivalent duty cycle as the average duty cycle of the two permanent magnet synchronous motors, and combined with the drive control quantity generated by the drive controller, finally realizing the linkage closed-loop control of the two permanent magnet synchronous motors with dual neutral point series power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 A schematic diagram of a dual-motor DC / DC boost drive structure;

[0061] Figure 2 It is a schematic diagram of a dual-neutral-point series power supply structure for dual motors;

[0062] Figure 3 It is a schematic diagram of the architecture of a dual-neutral-point series-powered dual-motor control system provided according to an embodiment of the present application;

[0063] Figure 4 A flowchart for determining control parameters of a boost controller according to an embodiment of the present application;

[0064] Figure 5 A schematic diagram of an equivalent boost model of a double neutral point series power supply structure provided according to an embodiment of the present application;

[0065] Figure 6 It is a current schematic diagram of an equivalent boost model of a double neutral point series power supply structure provided according to an embodiment of the present application in the 11 and 00 switching states;

[0066] Figure 7 It is a current schematic diagram of an equivalent boost model of a double neutral point series power supply structure provided according to an embodiment of the present application in the 10 and 01 switching states;

[0067] Figure 8 A switch state distribution time diagram of an equivalent boost model of a double neutral point series power supply structure provided according to an embodiment of the present application;

[0068] Fig. 9 A schematic diagram of voltage-current dual-loop control of a boost controller provided according to an embodiment of the present application;

[0069] Fig.10 It is a schematic diagram of the principle of dq axis drive control provided according to an embodiment of the present application;

[0070] Fig.11 The output results of the torque and speed of the two motors in Example 1 of the present application;

[0071] Fig.12 The output results of the three-phase current, neutral current and bus voltage of the two motors in Example 1 of the present application;

[0072] Fig.13 This is the change of bus voltage, neutral current and three-phase current of two motors in Example 2 of the present application. DETAILED DESCRIPTION

[0073] Hereinafter, the present application will be further described based on preferred embodiments with reference to the accompanying drawings.

[0074] In the description of the embodiments of the present application, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the products of the embodiments of the present application are usually placed when in use, it is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, in the description of the present application, in order to distinguish different units, the words first, second, etc. are used in this specification, but these are not limited by the order of manufacture, nor can they be understood as indicating or implying relative importance, and their names may be different in the detailed description and claims of the present application.

[0075] The vocabulary in this specification is used to illustrate the embodiments of the present application, but is not intended to limit the present application. It should also be noted that, unless otherwise clearly specified and limited, the terms "disposed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, an indirect connection through an intermediate medium, or a connection between the two elements. For those skilled in the art, the specific meanings of the above terms in this application can be specifically understood.

[0076] As described in the background technology, the current dual-motor drive solution for electric vehicles can be adopted Figure 1 The DC / DC boost drive architecture shown and Figure 2The dual neutral point power supply drive architecture shown in the figure. In the dual motor DC / DC boost drive topology, two inverters and motors are the working loads. The boost principle is used to boost the inverter working voltage from the smaller battery voltage to the target voltage. Although the boost principle is intuitive and easy to operate, an additional pair of power devices such as switching tubes and inductors will be added to the hardware architecture, resulting in an increase in the complexity of the dual motor drive and the system volume.

[0077] Figure 2 In the double neutral point series power supply structure (DNPSS) shown, the positive and negative poles of the power supply are respectively connected to the neutral points of the two permanent magnet synchronous motors (in the embodiment of the present application, for the convenience of description, the permanent magnet synchronous motor corresponding to the neutral point connected to the positive pole of the power supply is identified as the first permanent magnet synchronous motor, and the permanent magnet synchronous motor corresponding to the neutral point connected to the negative pole of the power supply is identified as the second permanent magnet synchronous motor), and the two permanent magnet synchronous motors have the same DC bus voltage.

[0078] The dual-motor drive structure can achieve torque output by controlling the dq-axis current of the three-phase inverter on both sides, and stabilize the bus voltage at the desired value by controlling the size of the zero-axis duty cycle on both sides. The drive and boost control can be regarded as decoupled, and the structure can also reduce the neutral line current ripple compared to the single neutral point power supply structure, so it has good application prospects.

[0079] However, for this structure, existing research has not clearly explained its boost mechanism, and the control of the three-phase current uses simple open-loop control, which cannot guarantee stable torque control of the two motors while boosting the voltage.

[0080] To this end, the present application provides a dual-motor control system with double neutral point series power supply to achieve closed-loop joint control of the two permanent magnet synchronous motors with double neutral point series power supply. Figure 3 A schematic diagram of the framework of a dual-motor control system with dual neutral point series power supply provided in this application.

[0081] like Figure 3 As shown, the dual-motor control system includes a boost controller, a boost distributor, two drive controllers (a first drive controller and a second drive controller) and two modulators (a first modulator and a second modulator).

[0082] The input of the boost controller includes the target DC bus voltage with u bus By comparing the difference between the two, the target DC bus voltage is achieved. Real-time tracking and output of equivalent duty cycle (i.e. αh1 -α h2 ), the equivalent duty cycle is distributed by the boost distributor according to a preset distribution strategy as the average duty cycle α of the first permanent magnet synchronous motor h1 and the average duty cycle α of the second permanent magnet synchronous motor h2 .

[0083] The first drive controller (such as Figure 3 The upper left dashed box shows the target torque Te of the first permanent magnet synchronous motor. 1 And track it in real time to generate the drive control quantity of the first permanent magnet synchronous motor Accordingly, the second drive controller (such as Figure 3 The dotted line box on the upper right side receives the target torque Te of the second permanent magnet synchronous motor 2 And track it in real time to generate the drive control quantity of the second permanent magnet synchronous motor

[0084] The first modulator (as shown in the box below the first driving controller) receives the α h1 , Generate the actual control signal of the first permanent magnet synchronous motor according to the preset modulation strategy (such as ZSVIPWM modulation strategy) The above actual control signal is specifically to switch the first permanent magnet synchronous motor inverter ( Figure 3 The duty cycle signal of the switching state of each phase power device of the inverter 1) is used to control the switching state of each phase power device by using the above actual control signal to realize the closed-loop control of the inverter of the first permanent magnet synchronous motor; accordingly, the second modulator (as shown in the box below the second drive controller) receives the α h2 , Generate the actual control signal of the second permanent magnet synchronous motor according to the preset modulation strategy The above actual control signal is used to implement closed-loop control of the inverter (inverter 2) of the second permanent magnet synchronous motor.

[0085] The specific implementations of the above-mentioned functional units are described in detail below in conjunction with the accompanying drawings.

[0086] [Boost Driver and Its Design Process]

[0087] It is known that when a single permanent magnet synchronous motor is powered by a neutral point power supply topology, different multiples of boost effects can be achieved by changing the duty cycle of the switch signal of each switch tube of the three-phase inverter. Figure 2As shown in the figure, the neutral point is connected to the positive and negative poles of the power supply respectively. The boost mechanism is more complicated than the single motor neutral point power supply topology. Therefore, it is necessary to construct an effective boost model based on the clear boost mechanism of the topology structure to ensure the reasonable setting of the boost driver control parameters so that it can accurately adjust the DC bus voltage.

[0088] In some embodiments of the present application, Figure 4 As shown, its control parameters are determined by the following steps:

[0089] S1, establish the boost expression under the double neutral point series power supply structure;

[0090] S2, establishing an equivalent boost model under a double neutral point series power supply structure based on the boost expression;

[0091] S3, obtaining a small signal mathematical model of the equivalent boost model;

[0092] S4, determining voltage loop control parameters and current loop control parameters of the boost controller based on the small signal mathematical model of the equivalent boost model.

[0093] a. Derivation of the boost expression for the DNPSS structure

[0094] according to Figure 2 The topological structure of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor can be expressed by equations (1) and (2):

[0095]

[0096] Among them, Figure 2 As shown, subscript O represents the grounding point, subscript N 1 、N 2 Represent the neutral points of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor, respectively, with subscript A 1 , B 1 , C 1 They represent the connection points of the upper and lower switches of each phase of the first permanent magnet synchronous motor inverter, with the subscript A 2 , B 2 , C 2 They respectively represent the connection points of the upper and lower switching tubes of each phase of the second permanent magnet synchronous motor inverter.

[0097] Then, we can get equations (3) and (4) from the coordinate transformation formula:

[0098]

[0099] Among them, the subscript d 1 ,q 1 , 0 1They represent the d-axis, q-axis, and 0-axis components of the first permanent magnet synchronous motor, respectively. 2 ,q 2 , 0 2 They respectively represent the d-axis, q-axis, and 0-axis components of the second permanent magnet synchronous motor.

[0100] Then the 0-axis voltage of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor can be expressed by equations (5) and (6):

[0101]

[0102] in, R S1 are the 0-axis duty cycle, 0-axis current, 0-axis inductance and stator resistance of the first permanent magnet synchronous motor, R S2 They are respectively the 0-axis duty cycle, 0-axis current, 0-axis inductance and stator resistance of the second permanent magnet synchronous motor.

[0103] According to the equal power conversion, the 0-axis current of the two permanent magnet synchronous motors shown in formula (7-1) can be obtained: With the neutral current i N The relationship between the two permanent magnet synchronous motors and the average duty cycle of the inverter is shown in formula (7-2). Duty cycle with 0 axis Relationship:

[0104]

[0105]

[0106] The potentials of the two neutral points can be expressed by equations (8) and (9):

[0107]

[0108]

[0109] According to (8) and (9), we can get the power supply voltage u in The expression (10) is:

[0110]

[0111] In steady state, ignoring the differential term and stator resistance voltage drop, the self-power supply voltage u can be obtained under the double neutral point power supply topology: in Boost to DC bus voltage u bus The boost expression (11) is:

[0112]

[0113] Δα in the above formula h It is defined as the equivalent duty cycle. From equation (11), it can be seen that for the topology of double neutral point series power supply, by controlling the equivalent duty cycle Δα h , which is the average duty cycle of the inverters of the two permanent magnet synchronous motors and The difference between the two can control the boost multiple of the DC bus voltage, that is, when the differential term, i.e. the stator resistance voltage drop, is ignored. Overall, it has characteristics equivalent to the boost duty cycle under the single-motor neutral point boost drive architecture.

[0114] b. Establish an equivalent boost model

[0115] According to the above boost expression (11), the relationship between the DC bus voltage and the difference in the average duty cycle of the inverters on both sides is reflected. Obviously, unlike the neutral point boost method of a single motor, the closer the average duty cycle of the inverters on both sides is, the higher the boost effect can be obtained. Therefore, compared with the single neutral point boost structure, this topology can obtain a wider boost range.

[0116] In addition, in the actual control process, in order to achieve a better response effect, it is necessary to determine the type and control parameters of the boost controller according to the above-mentioned boost mechanism. Therefore, it is necessary to first establish an equivalent boost model under the double neutral point series power supply structure.

[0117] In some embodiments, Figure 5 As shown, the equivalent boost model under the double neutral point series power supply structure includes equivalent resistance R, equivalent capacitance C, first equivalent inverter unit, second equivalent inverter unit, first equivalent zero axis resistance R 1 , the second equivalent zero axis resistance R 2 , the first equivalent zero-axis inductance L 1 and the second equivalent zero-axis inductance L 2 .

[0118] Specifically, the first equivalent inverter unit includes a first upper switch tube A H and the first lower switch tube A L The second equivalent inverter unit includes a second upper switch tube B H And the second lower switch tube B L ; Among them, the first end of the equivalent resistor R, the first end of the equivalent capacitor C, the first upper switch tube A H The first end of the second upper switch B H The first ends of the tubes are connected to each other, the second end of the equivalent resistor R, the second end of the equivalent capacitor C, the first lower switch tube A L The second end of the second lower switch tube B L The second ends of the first upper switch tube A are connected to each other; HThe second end of the first lower switch tube A L The first end is connected to the second upper switch tube B H The second end of the second lower switch tube B L The first end is connected to the first equivalent zero axis resistor R 1 , the first equivalent zero-axis inductance L 1 , the second equivalent zero-axis inductance L 2 , the second equivalent zero axis resistance R 2 The transistors are connected in series between the second end of the first upper switch tube and the second end of the second upper switch tube.

[0119] Figure 5 In the equivalent boost model shown, A H A L , B H B L The two are complementary and symmetrical. For example, 1 represents the upper tube on, and 0 represents the lower tube on (for example, 10 represents the switch state, and 0 represents the lower tube on). H and B L If the MOSFET is turned on, there are four switch states: 11, 00, 10, and 01.

[0120] c. Derive the small signal mathematical model of the equivalent boost model

[0121] According to the above equivalent boost model, its small signal mathematical model can be established, and based on this, a voltage and current dual-loop controller can be designed to improve the boost dynamic performance.

[0122] The establishment of small signal model is generally divided into three steps: instantaneous value averaging, separation of disturbances and linearization.

[0123] 1. Instantaneous value averaging, that is, for various variables x(t), as shown in formula (12), the instantaneous value is replaced by the average value of a switching cycle Ts to eliminate high-frequency switching ripple:

[0124]

[0125] like Figure 6 As shown, in the 11 and 00 switch states, the corresponding circuits in the two switch states are exactly the same. According to Kirchhoff's voltage law and current law, the following equations (13) and (14) can be established:

[0126]

[0127] Among them, v(t), i(t), v g (t), i C (t) are the DC bus voltage, power supply current, power supply voltage and the current of capacitor C respectively.

[0128] Similarly, if Figure 7As shown in the figure, in the 10 and 01 states, the corresponding circuits in the two switching states are basically the same, except that the capacitance directions are opposite, and can be analyzed in the same way. When the carriers of the permanent magnet synchronous motors on both sides are in phase, the 01 state does not appear. Here we only analyze the circuit in the 10 state, and we can establish equations (15) and (16):

[0129]

[0130]

[0131] 2. Separation disturbance:

[0132] Consider the DC and AC quantities separately. Figure 8 Taking the case of the carrier in phase as shown in the figure, the switching time of each state is calculated to obtain equation (17):

[0133]

[0134] Among them, D 1 , D 2 They respectively represent the DC components of the duty cycle of the first equivalent inverter unit and the duty cycle of the second equivalent inverter unit in the small signal mathematical model.

[0135] Divide the variables of interest into DC and AC quantities:

[0136]

[0137] Among them, capital letters represent the DC components of various variables, and lowercase letters with ^ represent the AC components of various variables.

[0138] According to equations (13), (15), (17), and (18), we can obtain equation (19) by partial integration:

[0139]

[0140] Let the corresponding DC quantities be equal, and we get formula (20):

[0141]

[0142] In steady state, the derivative is zero: V g -(D 1 -D 2 )V=0, we can get formula (21):

[0143]

[0144] This is consistent with the previously derived boost expression (11) for the DNPSS structure.

[0145] The corresponding alternating current quantities are equal, and we get formula (22):

[0146]

[0147] Similarly, for equations (14) and (16), the same treatment is performed to obtain equation (23):

[0148]

[0149] The corresponding DC quantities are equal, and we get formula (24):

[0150]

[0151] When the system differential is zero in steady state, we can obtain equations (25) and (26):

[0152]

[0153]

[0154] The corresponding alternating current quantities are equal, and we get formula (27):

[0155]

[0156] 3. Linearization:

[0157] When the amplitude of the small AC signal is much smaller than the DC value, the second-order differential in equations (23) and (27) can be discarded to obtain the following differential equation (28):

[0158]

[0159] d. Determine the control parameters of the boost controller

[0160] By establishing the above small signal mathematical model, the boost controller can be designed and its control parameters can be determined. Fig. 9 As shown in the figure, the boost controller adopts a voltage-current dual-loop controller architecture, and its control parameters can be determined based on the transfer function characteristics of its voltage outer loop and current inner loop.

[0161] First, perform Laplace transform on equation (28) to obtain equation (29):

[0162]

[0163] Where s is the independent variable of the Laplace transform.

[0164] The transfer function G of the difference in duty cycle between the two inverter units can be obtained by equation (29): vd (s), and the transfer function G from the power supply current to the difference in duty cycle of the two inverter units id (s):

[0165]

[0166]

[0167] According to equations (21) and (26), let The transfer function G from output voltage to power supply current can be obtained vi (s):

[0168]

[0169] The PI parameter tuning can be designed based on the expected crossover frequency and phase margin of the open-loop transfer function of the two control loops, where:

[0170] The open-loop transfer function of the current loop is shown in formula (33):

[0171]

[0172] The voltage loop open-loop transfer function is shown in formula (34):

[0173]

[0174] According to the open-loop transfer function, the desired crossover frequency f c_i 、f c_v and phase margin Design the PI parameters. Specifically, list the following equation (35) and solve it to obtain the voltage loop control parameter k of the boost controller: v_p , k v_i and current loop control parameter k i_p , k i_i :

[0175]

[0176] In the above formula, j is an imaginary unit.

[0177] [Distribution average duty cycle]

[0178] The boost controller outputs an equivalent duty cycle Δα by tracking the target bus DC voltage h Obviously, for every determined Δα h value, different values ​​can be assigned to the first permanent magnet synchronous motor and the second permanent magnet synchronous motor respectively. For example, when Δα h =0.3, you can choose or However, since the upper and lower limits of the average duty cycle of each permanent magnet synchronous motor are both [0,1], if the two permanent magnet synchronous motors are assigned Deviating from the midpoint, although it can satisfy However, it will cause the zero-sequence voltage of the motor on one side to be too large, reducing the utilization rate of the DC voltage of the corresponding motor, thereby reducing the power output capacity.

[0179] To this end, in some preferred embodiments of the present application, Figure 3 As shown, the preset allocation strategy adopted by the boost distributor is as follows: taking 0.5 as the center, the average duty cycle of the first permanent magnet synchronous motor is and the average duty cycle of the second permanent magnet motor Distributed as 0.5+Δα h / 2 and 0.5-Δα h / 2.

[0180] Through this allocation strategy, the duty cycle of the inverters on both sides is symmetrical about 0.5, and the zero-sequence voltage of the inverters on both sides is controlled to shift in opposite directions at the same speed. This is simple to operate and can achieve better control.

[0181] [Drive controller and its design process]

[0182] The first drive controller and the second drive controller are used to track the target torque Te of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor 1 、Te 2 And form the driving control quantity of the first permanent magnet synchronous motor, specifically, the torque command Te 1 Combined with the dq axis current distribution strategy, and Then compare it with the actual value and further obtain the control quantity u through PI control * d1 、u * q1 and u * d2 、u * q2 After coordinate transformation, the drive control quantity of each phase of the inverter of the two permanent magnet synchronous motors is obtained. and

[0183] Fig.10 In some embodiments, a schematic diagram of the principle of dq axis drive control is shown, such as Fig.10 As shown, the drive controller can adopt the traditional internal model controller architecture, and the transfer function of the PI controller is:

[0184]

[0185] Among them, K p_d , K p_qare the proportional gains of the d-axis and q-axis PI controllers, K i_d , K i_q are the integral gains of the d-axis and q-axis PI controllers respectively.

[0186] According to the principle of internal model control, the transfer function of the controller should be:

[0187]

[0188] Wherein, α is the control bandwidth of the dq axis current loop design.

[0189] Comparing equation (35) and equation (36), the parameters of the PI controller can be adjusted as follows:

[0190]

[0191] [Generate actual control signal]

[0192] The average duty cycle α of the first permanent magnet synchronous motor is obtained by the boost controller, the boost distributor and the two drive controllers. h1 and and the average duty cycle α of the second permanent magnet synchronous motor h2 and After that, the first modulator and the second modulator determine the actual control signals of each phase of the inverter of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor based on the following equations (38) and (39), respectively:

[0193]

[0194]

[0195] in, are respectively actual duty cycle signals for controlling phases A, B, and C of the inverter of the first permanent magnet synchronous motor, They are actual duty cycle signals for controlling phases A, B, and C of the inverter of the second permanent magnet synchronous motor respectively.

[0196] According to the above actual duty cycle signal, the switch tubes of the inverters of the two permanent magnet synchronous motors can be switched, thereby realizing the boost-drive control of the two permanent magnet synchronous motors.

[0197] [Example 1]

[0198] This embodiment is a simulation embodiment. Figure 3 The system architecture shown constructs a dual-motor control system with double neutral points in series, and the system simulation parameters are shown in Table 1.

[0199] Table 1 Simulation parameter settings for Example 1

[0200] parameter symbol Numeric unit Pole pairs p0 4 - Stator resistance Rs 0.07 Ω D-axis inductance Ld 1.7 mh Q-axis inductance Lq 3.4 mh 0 axis inductance L0 2.4 mh Permanent magnet flux ψf 0.0553 Wb Switching frequency f 10 kHz Supply voltage uin 60 V Target bus voltage transformation ubus 120 V

[0201] Fig.11 The output results of the torque and speed of the two motors are shown. Fig.11 It can be seen that the dual-motor control system provided in the present application can continuously and stably output torque and achieve good control of the motors on both sides.

[0202] Fig.12 The output results of the three-phase current, neutral current and bus voltage of the two motors are shown. Fig.12 It can be seen that the three-phase current has good sinusoidality and the neutral line current ripple amplitude is small, about 2A.

[0203] [Example 2]

[0204] This embodiment simulates the dual motor control during the dynamic adjustment of motor speed, wherein the input power u in is 60V, The target value is 120V, and the two motors experience acceleration and deceleration processes at 0.1s and 0.25s respectively. Fig.13 The bus voltage tracking, neutral current and three-phase current changes of the two motors are shown. Fig.13 As shown, the bus voltage remains stable throughout the process and the neutral current fluctuates very little.

[0205] The above is a detailed introduction to the specific implementation methods of the present application. For those skilled in the art, several improvements and modifications may be made to the present application without departing from the principles of the present application. These improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A dual-motor control system with dual neutral point series power supply, used for closed-loop joint control of a first permanent magnet synchronous motor and a second permanent magnet synchronous motor with dual neutral point series power supply, wherein the positive and negative poles of the power supply are respectively connected to the neutral points of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor, and the two permanent magnet synchronous motors have the same DC bus voltage, characterized in that: include: A boost controller, a boost distributor, a first drive controller, a second drive controller, a first modulator and a second modulator; The boost controller outputs an equivalent duty cycle by tracking the target DC bus voltage; The boost distributor distributes the equivalent duty cycle as an average duty cycle of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor using a preset distribution strategy; The first drive controller and the second drive controller respectively generate drive control quantities of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor by tracking the target torque; The first modulator and the second modulator respectively generate actual control signals of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor based on the average duty cycle and the drive control amount, and use the actual control signals to perform closed-loop control on the inverters of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor respectively.

2. The dual-motor control system with dual neutral point series power supply according to claim 1 is characterized in that: The boost controller is a voltage-current dual-loop controller, and its control parameters are determined by the following steps: S1, establish the boost expression under the double neutral point series power supply structure; S2, establishing an equivalent boost model under a double neutral point series power supply structure based on the boost expression; S3, obtaining a small signal mathematical model of the equivalent boost model; S4, determining voltage loop control parameters and current loop control parameters of the boost controller based on the small signal mathematical model of the equivalent boost model.

3. The dual-motor control system with dual neutral point series power supply according to claim 2 is characterized in that: The voltage boost expression under the double neutral point series power supply structure is established through the following steps: Based on the circuit topology and average theory of the double neutral point series power supply structure, the 0-axis voltage expression of the two permanent magnet synchronous motors is determined: Among them, u bus is the DC bus voltage, N1 and N2 are the neutral points of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor respectively, O is the grounding point, R S1 are the 0-axis duty cycle, 0-axis voltage, neutral point potential, 0-axis current, 0-axis inductance and stator resistance of the first permanent magnet synchronous motor, respectively. R S2 are the 0-axis duty cycle, 0-axis voltage, neutral point potential, 0-axis current, 0-axis inductance and stator resistance of the second permanent magnet synchronous motor respectively; Based on equal power conversion, the expression of the relationship between the 0-axis current and the neutral line current of the two permanent magnet synchronous motors and the expression of the relationship between the average duty cycle of the three-phase inverter and the 0-axis duty cycle are determined: Among them, i N is the neutral current, are the average duty cycles of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor respectively; The expression for determining the neutral point potential of two permanent magnet synchronous motors is: The expression of the power supply voltage under the double neutral point series power supply structure is established as shown in the following formula: Among them, u in is the power supply voltage; Ignoring the differential term and stator resistance voltage drop in steady state, the boost expression under the double neutral point series power supply structure is obtained as shown in the following formula: where Δα h is the equivalent duty cycle.

4. The dual-motor control system with dual neutral point series power supply according to claim 3 is characterized in that: The equivalent boost model under the dual neutral point series power supply structure includes an equivalent resistor R, an equivalent capacitor C, a first equivalent inverter unit, a second equivalent inverter unit, a first equivalent zero-axis resistor R1, a second equivalent zero-axis resistor R2, a first equivalent zero-axis inductor L1 and a second equivalent zero-axis inductor L2; The first equivalent inverter unit includes a first upper switch tube A H and the first lower switch tube A L The second equivalent inverter unit includes a second upper switch tube B H And the second lower switch tube B L ; Among them, the first end of the equivalent resistor R, the first end of the equivalent capacitor C, the first upper switch tube A H The first end of the second upper switch B H The first ends of the tubes are connected to each other, the second end of the equivalent resistor R, the second end of the equivalent capacitor C, the first lower switch tube A L The second end of the second lower switch tube B L The second ends of the ??are connected to each other; The first upper switch tube A H The second end of the first lower switch tube A L The first end is connected to the second upper switch tube B H The second end of the second lower switch tube B L The first end of the first equivalent zero-axis resistor R1, the first equivalent zero-axis inductor L1, the second equivalent zero-axis inductor L2, The second equivalent zero-axis resistor R2 is serially connected between the second end of the first upper switch tube and the second end of the second upper switch tube.

5. The dual-motor control system with dual neutral point series power supply according to claim 4, characterized in that: Step S3 performs instantaneous value averaging operation, disturbance separation operation and linearization operation on the equivalent boost model under the double neutral point series power supply structure to obtain a small signal mathematical model of the equivalent boost model as shown in the following formula: in, are the AC components of the DC bus voltage, DC bus current, power supply voltage, duty cycle of the first equivalent inverter unit, and duty cycle of the second equivalent inverter unit in the small signal mathematical model, respectively. V, I, D1, and D2 are the DC components of the DC bus voltage, DC bus current, duty cycle of the first equivalent inverter unit, and duty cycle of the second equivalent inverter unit in the small signal mathematical model, respectively. V is proportional to the power supply voltage V in the small signal mathematical model. g The following relations are satisfied:

6. The dual-motor control system with double neutral point series power supply according to claim 5, characterized in that: Step S4 further comprises the following steps: The small signal mathematical model of the equivalent boost model is Laplace transformed: Where s is the independent variable of Laplace transform; Based on the result of pull-type conversion, the transfer function G from the output voltage to the difference in duty cycle of the two inverter units is obtained as shown in the following formula: vd (s), and the transfer function G from the power supply current to the difference in duty cycle of the two inverter units id (s): make Determine the output voltage to supply current transfer function G as shown below vi (s): The current loop open-loop transfer function G1(s) and the voltage loop open-loop transfer function G2(s) are established as shown in the following equations: Set the desired crossover frequency f c_i 、f c_v and phase margin Solve the following equation to obtain the voltage loop control parameter k of the boost controller: v_p , k v_i and current loop control parameter k i_p , k i_i : Here, j is an imaginary unit.

7. The dual-motor control system with dual neutral point series power supply according to claim 3, characterized in that: The use of a preset allocation strategy to allocate the equivalent duty cycle as an average duty cycle of the first permanent magnet synchronous motor and the second permanent magnet synchronous motor is specifically: Centered on 0.5, the average duty cycle of the first permanent magnet synchronous motor and the average duty cycle of the second permanent magnet motor They are respectively distributed as 0.5+Δα h / 2 and 0.5-Δα h / 2.

8. The dual-motor control system with dual neutral point series power supply according to claim 3, characterized in that: The actual control signal of the first permanent magnet synchronous motor is shown as follows: in, are respectively actual duty cycle signals for controlling phases A, B, and C of the inverter of the first permanent magnet synchronous motor, A, B, and C phase drive control quantities of the inverter of the first permanent magnet synchronous motor generated by the first drive controller respectively; The actual control signal of the second permanent magnet synchronous motor is shown as follows: in, are respectively actual duty cycle signals for controlling phases A, B, and C of the inverter of the second permanent magnet synchronous motor, The A, B, and C phase drive control quantities of the inverter of the second permanent magnet synchronous motor are respectively generated by the second drive controller.

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