Synchronous motor driving system analysis method and device

Abstract

The invention relates to the technical field of motor systems, in particular to a synchronous motor driving system analysis method and device, and can solve the problems that an existing method relates to an optimization process, so that the calculated amount is generally large, the requirement for a processor is high, and part of technologies need to identify motor electromagnetic parameters, so that the cost is low to a certain extent. And the requirement of the control strategy on the computing power is increased. The method comprises the following steps: constructing a motor system coupling model; analyzing the loss of the motor system based on the coupling model; calculating the loss of the motor system under different switching frequencies according to the loss analysis of the motor system; selecting a series of working condition points, and respectively simulating and acquiring the operation efficiency of the motor and the inverter under the control of different switching frequencies; according to the motor efficiency and the inverter efficiency, the overall efficiency of the motor driving system is calculated, and the switching frequency value when the efficiency of the motor driving system is the highest on each working condition point is obtained, namely, the optimal switching frequency corresponding to the working condition point is obtained.

Description

Technical Field

[0001] The present application relates to the technical field of motor systems, and in particular to a method and device for analyzing a synchronous motor drive system. Background Art

[0002] Motor systems are widely used in industry, agriculture, construction, transportation and other fields, and they play an important role in national economic production. Improving the efficiency of motor systems is of great significance for saving energy and protecting the environment. The power supply is supplied to the motor after being processed by the inverter, and then converted into mechanical energy output on the shaft through electromechanical energy. The inverter and the motor body are two key devices for the motor system to realize energy transmission and conversion. Their efficiency directly determines the overall conversion efficiency of the system.

[0003] The inverter and the motor have a direct electrical connection and a deep coupling relationship, that is, the working characteristics influence each other. For example, the harmonic components of the inverter power supply to the motor will significantly affect the motor's mechanical and electrical characteristics, especially the losses. At the same time, the motor parameters are related to the operating conditions and are not constants, which will affect the inverter's power supply characteristics. In order to meet the optimal energy efficiency requirements of the motor system, existing efficiency optimization control technologies are mostly achieved by optimizing current, without exploring more control degrees of freedom, and the optimization goal of some technologies is to optimize the efficiency of the motor itself, or even to reduce specific loss components such as the core loss of the motor itself.

[0004] However, since the existing methods involve an optimization process, the amount of calculation is generally large and the requirements for the processor are high. In addition, some technologies require the identification of the electromagnetic parameters of the motor, which increases the computing power requirements of the control strategy. Summary of the invention

[0005] In order to solve the problem that the existing methods involve an optimization process, and thus the amount of calculation is generally large and the requirements for the processor are high, and some technologies require the identification of motor electromagnetic parameters, which increases the requirements of the control strategy for computing power, the present application provides a synchronous motor drive system analysis method and device.

[0006] The embodiment of the present application is implemented as follows:

[0007] In a first aspect, the present application provides a synchronous motor drive system analysis method, comprising:

[0008] Construct motor system coupling model;

[0009] Analyzing the losses of the motor system based on the coupling model;

[0010] According to the motor system loss analysis, the motor system loss at different switching frequencies is calculated;

[0011] Select a series of operating points to simulate and obtain the operating efficiency of the motor and inverter under different switching frequency control;

[0012] According to the motor efficiency and inverter efficiency, the overall efficiency of the motor drive system is calculated, and the switching frequency value when the electric drive system has the highest efficiency at each operating point is obtained, which is the optimal switching frequency corresponding to the operating point.

[0013] In a possible implementation, the motor system coupling model is established by coupling based on the motor electromagnetic field model, the external circuit model, the control system model and the motion model;

[0014] The control equation of the motor electromagnetic field model is:

[0015]

[0016] Where θ is the magnetic resistivity, σ is the electrical conductivity, A is the vector magnetic potential, and J s is the current density; μ0 is the vacuum magnetic permeability, M r is the magnetization vector;

[0017] The control equation of the external circuit model is:

[0018]

[0019] Among them, R s is the stator resistance of the motor; s is the cross-sectional area of ​​the stator winding; L e is the inductance of the armature winding end; l a is the axial length of the core; U s and i s are the phase voltage and phase current of the stator respectively; Ω + and Ω - They are the total areas of the single-phase winding coil in the positive direction and the negative direction in the solution area respectively;

[0020] The control model adopts motor vector control including maximum torque current ratio control and flux weakening control;

[0021] The motion model control equation is:

[0022]

[0023] Among them, J m Expressed as the moment of inertia of the motor; ω m Expressed as the mechanical angular velocity of the motor rotor; T e and T L Expressed as electromagnetic torque and load torque.

[0024] In a possible implementation, the motor system loss analysis includes motor driver loss calculation and motor body loss calculation;

[0025] The power switch in the motor driver includes an IGBT chip and a reverse parallel diode (FWD) chip, and the loss of the power switch includes IGBT turn-on loss, IGBT turn-off loss, diode turn-off loss and IGBT and diode conduction loss;

[0026] The motor body loss includes core loss, winding loss and permanent magnet eddy current loss.

[0027] In a possible implementation, the conduction loss of the IGBT and the diode is determined by multiplying the current of the device in the on state by the conduction voltage drop corresponding to the on current:

[0028] P con,T / D =v c,T / D (t)·i c,T / D (t);

[0029] Among them, P con,T / D is the conduction loss of IGBT and diode; v c,T / D (t) represents the instantaneous on-state voltage drop; i c,T / D (t) represents the instantaneous on-current;

[0030] The switching loss of the switching device can be expressed as:

[0031]

[0032] Among them, V dc is the DC bus voltage; V ref is the reference voltage; E sw,T / D (t) is the test reference loss; T sw is the switching action time of the switching device;

[0033] The switching loss calculation formula of IGBT is:

[0034]

[0035] Among them, T on 、T off It is expressed as the time of IGBT’s turn-on and turn-off action, and Eon and Eoff are single switching losses;

[0036] The switching loss of the diode is:

[0037]

[0038] Among them, T offis the turn-off time of the diode, Ere is the reverse turn-off loss;

[0039] The total loss caused by the power module can be expressed as:

[0040] P loss_IGBT =P con,T +P con,D +P sw,T +P sw,D .

[0041] In a possible implementation, the core loss calculation can be expressed as:

[0042]

[0043] Among them, B rm Expressed as the amplitude of the radial component of magnetic flux density; B tm Expressed as the amplitude of the magnetic osculating component; k h is the hysteresis loss coefficient; k c is the eddy current loss coefficient; k e is the additional loss coefficient; f is the frequency;

[0044] The calculation formula of the motor winding loss is:

[0045] P Cu =mI 2 R;

[0046] Wherein, m is the number of phases of the stator winding; I is the effective value of the current flowing through the stator winding, in A; R is the equivalent resistance of each phase winding, in Ω;

[0047] The calculation formula of the permanent magnet eddy current loss is:

[0048]

[0049] Among them, V pm is the volume of permanent magnet; σ pm is the electrical conductivity of the permanent magnet; J is the eddy current density in the permanent magnet.

[0050] In a possible implementation, the calculating the loss of the motor system at different switching frequencies according to the motor system loss analysis further includes:

[0051] The motor drive system is operated at a rated speed of 1500rpm and a load of 10Nm. The inverter is controlled at switching frequencies of 1kHz, 2kHz, 4kHz, 8kHz, and 16kHz, and the single-phase current waveform output is observed.

[0052] The inverter IGBT loss, diode and total loss were observed when the inverter switching frequency was 1kHz, 2kHz, 4kHz, 8kHz, 16kHz and 20kHz respectively;

[0053] When the switching frequencies are 1kHz, 2kHz, 4kHz, 8kHz, 16kHz and 20kHz respectively, the motor stator core loss, rotor core loss, permanent magnet eddy current loss, winding copper loss and total motor loss are observed.

[0054] In a possible implementation, the series of operating points are combinations of multiple motor speeds and load torques.

[0055] In a possible implementation, the step of obtaining the switching frequency value when the efficiency of the electric drive system is the highest at each operating point, that is, the optimal switching frequency corresponding to the operating point, further includes:

[0056] When selecting the optimal switching frequency, ensure that the switching frequency is more than 10 times the motor frequency to ensure motor control performance;

[0057] Through comparison, the switching frequency that makes the electric drive system achieve the highest efficiency is selected.

[0058] In a possible implementation, after the step of calculating the overall efficiency of the motor drive system according to the motor efficiency and the inverter efficiency, and obtaining the switching frequency value when the electric drive system has the highest efficiency at each operating point, that is, the optimal switching frequency corresponding to the operating point, the method further includes:

[0059] Under each specific operating condition, an optimal switching frequency can be determined based on the efficiency of the electric drive system;

[0060] The optimal switching frequency within the motor speed range under different load torque conditions is extracted into a switching frequency query control table, and the switching frequency query control table can specify a corresponding optimal switching frequency for each working condition according to a predetermined speed range and load torque range, forming a switching frequency matrix;

[0061] Based on the switching frequency selection, a corresponding triangular carrier signal is generated to maximize the efficiency of the motor drive system.

[0062] In a second aspect, the present application provides a synchronous motor drive system analysis device, comprising:

[0063] Model building module, used to build motor system coupling model;

[0064] A loss analysis module, used for analyzing the motor system loss based on the coupling model;

[0065] A loss calculation module, used to calculate the loss of the motor system at different switching frequencies according to the motor system loss analysis;

[0066] The efficiency simulation module is used to select a series of operating points to simulate and obtain the operating efficiency of the motor and inverter under different switching frequency control;

[0067] The efficiency calculation module is used to calculate the overall efficiency of the motor drive system based on the motor efficiency and the inverter efficiency, and obtain the switching frequency value when the electric drive system has the highest efficiency at each operating point, which is the optimal switching frequency corresponding to the operating point.

[0068] The technical solution provided by this application can at least achieve the following beneficial effects:

[0069] The synchronous motor drive system analysis method provided in the present application realizes accurate simulation of the losses of the drive system under different operating conditions by utilizing the motor drive system coupling model, evaluates the influence of the switching frequency on the losses of the inverter and the motor body and the system efficiency, clarifies the optimal switching frequency for each operating condition and forms a queryable table. The inverter dynamically switches the switching frequency following the changes in the operating conditions of the motor drive system to achieve optimal system energy efficiency. Based on the detailed analysis of the motor system losses, the influence of the control parameters on the losses of each component of the system can be intuitively presented, and the optimal control parameters are obtained only by table lookup, without involving iterative links such as optimization, etc. The calculation amount is small and has higher real-time performance, and the processor requirements are low, which can reduce the cost required for function implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0071] Figure 1 is a flow chart of a synchronous motor drive system analysis method shown in an exemplary embodiment of the present application;

[0072] Figure 2 is a schematic diagram of a motor system connection shown in an exemplary embodiment of the present application;

[0073] Figure 3 is a schematic diagram of a motor system coupling model shown in an exemplary embodiment of the present application;

[0074] Figure 4 It is a schematic diagram of the speed, three-phase stator current and torque waveform of the permanent magnet synchronous motor coupling simulation shown in an exemplary embodiment of the present application;

[0075] Figure 5 1 is a schematic diagram of a current waveform of an upper bridge arm of phase A shown in an exemplary embodiment of the present application;

[0076] Figure 6 It is a partially enlarged schematic diagram of the conduction current waveform of the upper bridge arm of phase A shown in an exemplary embodiment of the present application;

[0077] Figure 7 is a schematic diagram of inverter loss calculation shown in an exemplary embodiment of the present application;

[0078] Figure 8 It is a schematic diagram of orthogonal decomposition components of magnetic flux density at a certain location of the stator core and magnetic flux density rotation change trajectory shown in an exemplary embodiment of the present application;

[0079] Fig. 9 is a schematic diagram of single-phase current waveforms at different switching frequencies shown in an exemplary embodiment of the present application;

[0080] Fig.10 is a schematic diagram of inverter losses at different switching frequencies shown in an exemplary embodiment of the present application;

[0081] Fig.11 is a schematic diagram of motor losses at different switching frequencies shown in an exemplary embodiment of the present application;

[0082] Fig.12 is a schematic diagram of inverter efficiency distribution under various operating conditions at different switching frequencies shown in an exemplary embodiment of the present application;

[0083] Fig.13 is a schematic diagram of motor efficiency distribution under various operating conditions at different switching frequencies shown in an exemplary embodiment of the present application;

[0084] Fig.14 is a schematic diagram of selecting the optimal switching frequency of a motor drive system shown in an exemplary embodiment of the present application;

[0085] Fig.15 is a schematic diagram of motor speed, three-phase current, torque and switching frequency curves under six groups of working conditions shown in an exemplary embodiment of the present application;

[0086] Fig.16 is a structural schematic diagram of a synchronous motor drive system analysis device shown in an exemplary embodiment of the present application;

[0087] Fig.17 It is a schematic diagram of the a-phase current waveform and pulse signal under some working conditions shown in an exemplary embodiment of the present application.

[0088] Reference numerals:

[0089] 1. Model building module; 2. Loss analysis module; 3. Loss calculation module; 4. Efficiency simulation module; 5. Efficiency calculation module. DETAILED DESCRIPTION

[0090] In order to make the purpose, implementation mode and advantages of the present application clearer, the exemplary implementation mode of the present application will be clearly and completely described below in conjunction with the drawings in the exemplary embodiments of the present application. Obviously, the described exemplary embodiments are only part of the embodiments of the present application, not all of the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0091] It should be noted that the brief description of terms in this application is only for the convenience of understanding the embodiments described below, and is not intended to limit the embodiments of this application. Unless otherwise specified, these terms should be understood according to their common and usual meanings.

[0092] The terms "first", "second", "third", etc. in the specification and claims of this application and the above drawings are used to distinguish similar or similar objects or entities, and do not necessarily mean to limit a specific order or sequence, unless otherwise noted. It should be understood that the terms used in this way can be interchangeable under appropriate circumstances.

[0093] The terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover but not exclude inclusion, for example, a product or device comprising a list of components is not necessarily limited to all the components expressly listed but may include other components not expressly listed or inherent to such product or device.

[0094] Before explaining the synchronous motor drive system analysis method provided in the embodiment of the present application, the application scenario and implementation environment of the embodiment of the present application are first introduced.

[0095] Motor systems are widely used in industry, agriculture, construction, transportation and other fields, and they play an important role in national economic production. Improving the efficiency of motor systems is of great significance for saving energy and protecting the environment.

[0096] The power supply is processed by the inverter and then supplied to the motor, which is then converted into mechanical energy output on the shaft through electromechanical energy. The inverter and the motor body are two key devices for the motor system to realize energy transmission and conversion. Their efficiency directly determines the overall conversion efficiency of the system.

[0097] The inverter and the motor have a direct electrical connection and a deep coupling relationship, that is, the working characteristics affect each other. For example, the harmonic components of the inverter's power supply to the motor will significantly affect the motor's mechanical and electrical characteristics, especially the losses. At the same time, the motor parameters are related to the operating conditions and are not constants, which will affect the inverter's power supply characteristics.

[0098] In response to the demand for optimal energy efficiency of motor systems, existing efficiency optimization control technologies are mostly achieved by optimizing current, without exploring more control degrees of freedom. In addition, the optimization goals of some technologies are to optimize the efficiency of the motor itself, or even to reduce specific loss components such as the core loss of the motor itself.

[0099] Since the existing methods involve an optimization process, the amount of calculation is generally large and the requirements for the processor are high. In addition, some technologies require the identification of the electromagnetic parameters of the motor, which increases the computing power requirements of the control strategy.

[0100] Defects of the existing technology:

[0101] 1. The existing technical solutions only consider optimizing the current to reduce the motor and system losses to improve the system efficiency, but do not consider the switching frequency, which is a key control degree of freedom.

[0102] 2. Existing technical solutions mostly involve iterative steps such as optimization, which require large amounts of calculations and high processor performance.

[0103] 3. The existing technical solutions do not pay attention to the distribution of losses of different devices in the motor system and lack flexibility.

[0104] Based on this, the present application provides a synchronous motor drive system analysis method and device, which uses the motor drive system coupling model to realize accurate simulation of the losses of the drive system under different operating conditions, evaluates the impact of the switching frequency on the inverter and motor body losses and system efficiency, and clarifies the optimal switching frequency for each operating condition to form a queryable table. The inverter follows the changes in the motor drive system operating conditions to achieve dynamic switching of the switching frequency to achieve optimal system energy efficiency.

[0105] Next, the technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems will be described in detail through embodiments and in combination with the accompanying drawings. The embodiments may be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. Obviously, the described embodiments are part of the embodiments of the present application, not all of them.

[0106] Figure 1 It is a flowchart of a synchronous motor drive system analysis method shown in an exemplary embodiment of the present application.

[0107] In an exemplary embodiment, Figure 1 As shown, a synchronous motor drive system analysis method is provided, which may include the following steps:

[0108] Step 100: Construct a motor system coupling model.

[0109] Step 200: Analyze the losses of the motor system based on the coupling model.

[0110] Step 300: According to the motor system loss analysis, the motor system loss at different switching frequencies is calculated.

[0111] Step 400: Select a series of operating points to simulate and obtain the operating efficiency of the motor and the inverter under different switching frequency control.

[0112] Step 500: Calculate the overall efficiency of the motor drive system based on the motor efficiency and the inverter efficiency, and obtain the switching frequency value when the motor drive system has the highest efficiency at each operating point, which is the optimal switching frequency corresponding to the operating point.

[0113] Figure 2 is a schematic diagram of a motor system connection shown in an exemplary embodiment of the present application, Figure 3 is a schematic diagram of a motor system coupling model shown in an exemplary embodiment of the present application, Figure 4 1 is a schematic diagram of the speed, three-phase stator current and torque waveforms of a permanent magnet synchronous motor coupling simulation shown in an exemplary embodiment of the present application. Figure 5 : is a schematic diagram of the conduction current waveform of the upper bridge arm of phase A shown in an exemplary embodiment of the present application, Figure 6 1 is a schematic diagram of a partial enlargement of the on-current waveform of the upper bridge arm of phase A shown in an exemplary embodiment of the present application. Figure 7 is a schematic diagram of inverter loss calculation shown in an exemplary embodiment of the present application, Figure 8 is a schematic diagram of orthogonal decomposition components of magnetic flux density at a certain location of the stator core and magnetic flux density rotation change trajectory shown in an exemplary embodiment of the present application, Fig. 9 is a schematic diagram of single-phase current waveforms at different switching frequencies shown in an exemplary embodiment of the present application, Fig.10 is a schematic diagram of inverter losses at different switching frequencies shown in an exemplary embodiment of the present application, Fig.11 is a schematic diagram of motor losses at different switching frequencies shown in an exemplary embodiment of the present application, Fig.12 is a schematic diagram of inverter efficiency distribution under various operating conditions at different switching frequencies shown in an exemplary embodiment of the present application, Fig.13 is a schematic diagram of motor efficiency distribution under various operating conditions at different switching frequencies shown in an exemplary embodiment of the present application, Fig.14 is a schematic diagram of selecting the optimal switching frequency of a motor drive system shown in an exemplary embodiment of the present application, Fig.15 It is a schematic diagram of the motor speed, three-phase current, torque and switching frequency curves under six groups of working conditions shown in an exemplary embodiment of the present application.

[0114] In a possible implementation, the specific implementation scheme of the synchronous motor drive system analysis method is as follows:

[0115] 1: Motor system coupling model

[0116] When the motor drive system is actually running, the control system outputs a gate trigger signal to the insulated gate bipolar transistor (IGBT) of the inverter power switch device, which is referred to as the external circuit because it is the external circuit of the motor, and transmits the modulated three-phase voltage source excitation to the motor; the speed, rotor position, stator current and other information of the motor during operation are detected by photoelectric encoders, Hall sensors, etc., and then converted into analog and digital form and fed back to the control system, such as Figure 2 shown.

[0117] The physical model of the motor system includes: motor electromagnetic field model, external circuit model, control system model and motion model.

[0118] The motor electromagnetic field control equation is:

[0119]

[0120] Where, is the magnetoresistance, σ is the conductivity, A is the vector magnetic potential, J s is the current density; μ0 is the vacuum magnetic permeability, M r is the magnetization vector.

[0121] The control equation of the external circuit model is:

[0122]

[0123] Among them, R s is the stator resistance of the motor; s is the cross-sectional area of ​​the stator winding; L e is the inductance of the armature winding end; l a is the axial length of the core; U s and i s are the phase voltage and phase current of the stator respectively; Ω + and Ω - The total area of ​​the single-phase winding coil in the positive direction and the negative direction in the solution area are respectively obtained. The control model adopts motor vector control including maximum torque current ratio control and weak magnetic control.

[0124] The control equation of the motion model is:

[0125]

[0126] Among them, J m Expressed as the moment of inertia of the motor; ω m Expressed as the mechanical angular velocity of the motor rotor; T e and T L It is expressed as electromagnetic torque and load torque. Based on the coupling of the independent models of each part, the motor system coupling model is established. The principle block diagram is as follows Figure 3 shown.

[0127] In the coupling model, the gate drive signal generated by the control strategy is transmitted to the switching device in the circuit model, the DC bus voltage is modulated into a three-phase voltage source excitation, and transmitted to the motor electromagnetic analysis model to calculate the motor performance parameters, and the motor rotor position, phase current and other signals required by the control system are obtained. These signals are immediately fed back to the control system as feedback signals for the next time step calculation.

[0128] Based on this coupling model, the starting and sudden loading process of the permanent magnet synchronous motor is simulated. The motor speed is 1200rpm, the switching frequency is 10kHz, and a 6Nm load is suddenly added at 20ms. The motor speed, three-phase stator current, and torque waveforms are as follows: Figure 4 shown.

[0129] 2. Motor system loss analysis

[0130] (I) Calculation of motor drive losses

[0131] The power switching components in the motor driver include IGBT chips and reverse parallel diode (FWD) chips.

[0132] There are five main types of power switch losses: IGBT turn-on loss, IGBT turn-off loss, diode turn-off loss, and IGBT and diode conduction loss.

[0133] The transient current flowing through the device is analyzed to accurately calculate the conduction loss and switching loss of the switching device.

[0134] The conduction loss can be determined by multiplying the current in the device in the on state by the voltage drop corresponding to the on current:

[0135] P con,T / D =v c,T / D (t)·i c,T / D (t).

[0136] Where: P con,T / D is the conduction loss of IGBT and diode; v c,T / D (t) represents the instantaneous on-state voltage drop; i c,T / D (t) represents the instantaneous on-current. Calculated according to each switching action process,

[0137] The switching loss of the switching device can be expressed as:

[0138]

[0139] Where: V dc is the DC bus voltage; V ref is the reference voltage; Esw,T / D (t) is the test reference loss; T sw is the switching action time of the switching device. For IGBT devices, the switching loss includes turn-on loss and turn-off loss.

[0140] The calculation formula for IGBT switching loss is:

[0141]

[0142] Where: T on 、T off It is expressed as the time of IGBT's turn-on and turn-off actions, Eon and Eoff are single switching losses. For diodes, the switching loss includes reverse turn-off loss.

[0143] The switching loss of the diode is:

[0144]

[0145] Where: T off is the turn-off time of the diode, and Ere is the reverse turn-off loss. The total loss generated by the power module can be expressed as:

[0146] P loss_IGBT =P con,T +P con,D +P sw,T +P sw,D .

[0147] In order to achieve accurate simulation calculation of real-time power switching device losses, the constructed calculation model needs to identify the time when each loss occurs in order to accurately trigger the switching loss and conduction loss calculation of IGBT and diode.

[0148] like Figure 5 As shown, it is the conduction current i of the upper bridge arm of phase A under the field-circuit coupling model simulation. c (t) Waveform diagram, partial enlargement diagram see Figure 6 .

[0149] Taking the upper bridge arm of phase A as an example, when the conduction current i c When (t)>0, the IGBT is in the on state; when the on current i c (t)<0, the diode is in the on state, so by judging i c (t) is compared with 0, that is, the conduction type can be determined. Similarly, when the conduction current i c When (t)>0 and a rising edge signal is present, the IGBT is turned on and generates a turn-on loss E on ; When the conduction current i c When (t)>0 and a falling edge signal is present, the IGBT turns off and generates a turn-off loss E off; When the conduction current i c When (t)<0 and a falling edge signal is presented, the diode generates reverse turn-off loss E rec From this, the timing control module can determine the type of loss.

[0150] Based on the inverter loss model, the loss calculation block diagram is shown in Figure 7. The model consists of two core parts: the loss calculation module and the timing control module. The timing control module is responsible for generating trigger signals, while the loss calculation module determines and calculates the corresponding loss type based on these signals. The model strictly follows the actual timing of the loss and performs online calculation of each instantaneous loss value.

[0151] (II) Calculation of motor body loss

[0152] The motor body loss mainly includes core loss, winding loss, permanent magnet eddy current loss, etc. Considering that the magnetic field inside the motor is a rotating magnetic field, the magnetic field decomposition is used to perform orthogonal decomposition of the rotating magnetic field represented by the Cartesian coordinate system in the radial and tangential directions.

[0153]

[0154] Among them, B r , B t They are respectively expressed as the amplitude of the positive and tangential components after orthogonal decomposition of the magnetic flux density. The orthogonal decomposition vector diagram of the radial and tangential components of the magnetic flux density at a certain point in the core changing with time is shown in Figure 8 shown.

[0155] Then the core loss calculation can be expressed as:

[0156]

[0157] Among them: B rm Expressed as the amplitude of the radial component of magnetic flux density; B tm Expressed as the amplitude of the magnetic osculating component; k h is the hysteresis loss coefficient; k c is the eddy current loss coefficient; k e is the additional loss coefficient; f is the frequency. The motor winding loss is calculated using the following formula:

[0158] P Cu =mI 2 R

[0159] Where: m is the number of phases of the stator winding; I is the effective value of the current flowing through the stator winding, in A; R is the equivalent resistance of each phase winding, in Ω. The eddy current loss of the permanent magnet is calculated using the following formula:

[0160]

[0161] Where: V pm is the volume of permanent magnet; σ pm is the electrical conductivity of the permanent magnet; J is the eddy current density in the permanent magnet.

[0162] 3. System Energy Efficiency Optimization Variable Switching Frequency Permanent Magnet Synchronous Motor Drive System Control

[0163] Effect of switching frequency on losses and system efficiency

[0164] In the control link of the motor drive system, the switching frequency is a key parameter for adjusting the number of switching actions of the inverter and has a significant impact on the quality of the output current.

[0165] Considering the motor drive system running at a rated speed of 1500rpm and a load of 10Nm, the inverter outputs single-phase current waveforms at switching frequencies of 1kHz, 2kHz, 4kHz, 8kHz, and 16kHz. Fig. 9 As shown, from Fig. 9 It can be clearly observed that the current waveform contains obvious harmonic components, and the THD values ​​are 18.73%, 9.96%, 6.36%, 5.85%, and 5.66%, respectively. The stator current THD value decreases with the increase of the switching frequency, and the rate of decrease of the THD value gradually slows down. When the switching frequency is 20kHz, the current still contains harmonic components. The existence of harmonic components in the stator current is inevitable.

[0166] Fig.10 The bar graph and line graph of the inverter IGBT loss, diode and total loss are listed when the inverter switching frequency is 1kHz, 2kHz, 4kHz, 8kHz, 16kHz and 20kHz respectively. As the switching frequency increases, the total loss of the inverter increases significantly, among which the losses of IGBT and diode increase significantly.

[0167] Fig.11 The bar graph and line graph of the motor stator core loss, rotor core loss, permanent magnet eddy current loss, winding copper loss and total motor loss are shown when the switching frequency is 1kHz, 2kHz, 4kHz, 8kHz, 16kHz and 20kHz. As the switching frequency increases, the total motor loss decreases. Except for the small fluctuation of the rotor core loss, the stator core loss, permanent magnet eddy current loss and winding copper loss have all decreased significantly.

[0168] A series of operating points (motor speed and load torque combinations) are selected to simulate and obtain the operating efficiency of the motor and inverter under different switching frequency control. The relevant results are shown as follows Fig.12 and Fig.13 shown.

[0169] (II) System Energy Efficiency Optimization Variable Switching Frequency Permanent Magnet Synchronous Motor Drive System Control

[0170] After obtaining the motor efficiency and inverter efficiency, the overall efficiency of the motor drive system is calculated by multiplication. In addition, the switching frequency value when the electric drive system has the highest efficiency can be obtained at each operating point. This switching frequency is the optimal switching frequency corresponding to the operating point.

[0171] When selecting the optimal switching frequency, it is necessary to ensure that the switching frequency is more than 10 times the motor frequency to ensure the motor control performance. Therefore, this condition is taken into consideration when selecting the optimal switching frequency, and the switching frequency that makes the electric drive system most efficient is selected through comparison.

[0172] Fig.14 The switching frequency diagram for the optimal efficiency of the electric drive system of the permanent magnet synchronous motor under all working conditions is shown in Figure 1. Under each specific working condition, an optimal switching frequency can be determined based on the efficiency of the electric drive system. A variable switching frequency adjustment mechanism based on optimal system efficiency is further introduced, such as Fig.15 As shown. Fig.14 The optimal switching frequency within the motor speed range under different load torque conditions is displayed and extracted into a switching frequency query control table.

[0173] The table specifies a corresponding optimal switching frequency for each operating condition according to a predetermined speed range and load torque range, forming a switching frequency matrix.

[0174] In the actual operation of the motor, the speed range n t1 ~n ti , load torque range T t1 ~T tj , corresponding to an i×j switching frequency f swc The speed nref and the load torque Te are used as feedback quantities, and the optimal switching frequency suitable for the current working condition can be determined based on them.

[0175] Based on this switching frequency selection, a corresponding triangular carrier signal is generated to maximize the efficiency of the motor drive system. In this way, the switching frequency of the inverter can be optimized under different operating conditions, thereby improving the operating efficiency of the entire motor drive system.

[0176] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the instructions, these steps are not necessarily executed in sequence according to the order of the instructions. Unless there is a clear explanation in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the above-mentioned embodiments may include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of the steps or stages in other steps.

[0177] Corresponding to the aforementioned embodiment of the synchronous motor drive system analysis method and adopting the same technical concept, the present application also provides an embodiment of a synchronous motor drive system analysis device.

[0178] Fig.16 It is a structural schematic diagram of a synchronous motor drive system analysis device shown in an exemplary embodiment of the present application.

[0179] In an exemplary embodiment, Fig.16 As shown, the synchronous motor drive system analysis device includes:

[0180] Model building module 1, used to build a motor system coupling model;

[0181] A loss analysis module 2, used for analyzing the motor system loss based on the coupling model;

[0182] A loss calculation module 3, used to calculate the loss of the motor system at different switching frequencies according to the motor system loss analysis;

[0183] The efficiency simulation module 4 is used to select a series of operating points to simulate and obtain the operating efficiency of the motor and the inverter under different switching frequency control;

[0184] The efficiency calculation module 5 is used to calculate the overall efficiency of the motor drive system according to the motor efficiency and the inverter efficiency, and obtain the switching frequency value when the electric drive system has the highest efficiency at each operating point, that is, the optimal switching frequency corresponding to the operating point.

[0185] For the specific definition of the synchronous motor drive system analysis device, please refer to the definition of the synchronous motor drive system analysis method above, which will not be repeated here. Each module in the above-mentioned synchronous motor drive system analysis device can be implemented in whole or in part by software, hardware and a combination thereof. The above-mentioned modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0186] Fig.17 It is a schematic diagram of the a-phase current waveform and pulse signal under some working conditions shown in an exemplary embodiment of the present application.

[0187] In order to verify this application, six groups of working conditions are selected to simulate and verify the control method, and the working conditions are: 500rpm / 5Nm, 750rpm / 5Nm, 1000rpm / 5Nm, 1000rpm / 10Nm, 750rpm / 10Nm, 500rpm / 10Nm. The simulation results are as follows Fig.15 As shown, the corresponding switching frequencies of the motors are 1450Hz, 1050Hz, 1200Hz, 2100Hz, 2050Hz, and 2350Hz. As the load and speed of the motor change, the switching frequency also changes accordingly.

[0188] Similarly, six groups of operating conditions, namely 500rpm / 5Nm, 750rpm / 5Nm, 1000rpm / 5Nm, 1000rpm / 10Nm, 750rpm / 10Nm, and 500rpm / 10Nm, were selected for experimental comparison. Considering that the optimal switching frequency increases with the increase of load torque at the same speed, two groups of operating conditions, 500rpm / 1.5Nm and 500rpm / 3Nm, were added to compare the optimal switching frequencies of different loads at the same speed and the current waveform with reduced harmonics as the switching frequency increases.

[0189] Fig.17 The a-phase current waveform ia and a-phase pulse signal under some working conditions of the motor are given. Under the working condition of 500rpm / 1.5Nm, the a-phase pulse count is about 24 times, and its switching frequency is 24×33.33Hz=800Hz; under the working condition of 500rpm / 3Nm, the a-phase pulse count is about 33 times, and its switching frequency is 32×33.33Hz=1100Hz; under the working condition of 500rpm / 5Nm, the a-phase pulse count is about 44 times, and its switching frequency is 44×33.33Hz=1467Hz; under the working condition of 500rpm / 10Nm, the a-phase pulse count is about 70 times, and its switching frequency is 2333Hz.

[0190] Under different working conditions, the switching frequency will also switch accordingly. When the permanent magnet synchronous motor is running, at 500rpm / 1.5Nm, the a-phase current THD is 13.23%; at 500rpm / 3Nm, the a-phase current THD is 9.7%; at 500rpm / 5Nm, the a-phase current THD is 7.72%; at 500rpm / 10Nm, the a-phase current THD is 5.90%. With the increase of load at the same speed, the optimal switching frequency selected based on system efficiency will also increase.

[0191] As a result, the pulse signal increases and the quality of the current waveform improves, which is manifested in the smoothing of the current waveform and the reduction of the current THD value. The experimental test values ​​of the motor drive system efficiency under the six selected working conditions are shown in Table 1. The variable switch control with the goal of optimizing the system energy efficiency has significantly improved efficiency compared to the constant switching frequency control.

[0192] Table 1 Comparison of efficiency of electric drive systems

[0193]

[0194]

[0195] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0196] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A synchronous motor drive system analysis method, characterized in that: include: Construct motor system coupling model; Analyzing the losses of the motor system based on the coupling model; According to the motor system loss analysis, the motor system loss at different switching frequencies is calculated; Select a series of operating points to simulate and obtain the operating efficiency of the motor and inverter under different switching frequency control; According to the motor efficiency and inverter efficiency, the overall efficiency of the motor drive system is calculated, and the switching frequency value when the electric drive system has the highest efficiency at each operating point is obtained, which is the optimal switching frequency corresponding to the operating point.

2. The synchronous motor drive system analysis method according to claim 1, characterized in that: The motor system coupling model is established by coupling based on the motor electromagnetic field model, the external circuit model, the control system model and the motion model; The control equation of the motor electromagnetic field model is: Where θ is the magnetic resistivity, σ is the electrical conductivity, A is the vector magnetic potential, and J s is the current density; μ0 is the vacuum magnetic permeability, M r is the magnetization vector; The control equation of the external circuit model is: Among them, R s is the stator resistance of the motor; s is the cross-sectional area of ​​the stator winding; L e is the inductance of the armature winding end; l a is the axial length of the core; U s and i s are the phase voltage and phase current of the stator respectively; Ω + and Ω - They are the total areas of the single-phase winding coil in the positive direction and the negative direction in the solution area respectively; The control model adopts motor vector control including maximum torque current ratio control and flux weakening control; The motion model control equation is: Among them, J m Expressed as the moment of inertia of the motor; ω m Expressed as the mechanical angular velocity of the motor rotor; T e and T L Expressed as electromagnetic torque and load torque.

3. The synchronous motor drive system analysis method according to claim 1, characterized in that: The motor system loss analysis includes the motor driver loss calculation and the motor body loss calculation; The power switch in the motor driver includes an IGBT chip and a reverse parallel diode (FWD) chip, and the loss of the power switch includes IGBT turn-on loss, IGBT turn-off loss, diode turn-off loss and IGBT and diode conduction loss; The motor body loss includes core loss, winding loss and permanent magnet eddy current loss.

4. The synchronous motor drive system analysis method according to claim 3, characterized in that: The IGBT and diode conduction losses are determined by multiplying the current of the device in the on state by the conduction voltage drop corresponding to its conduction current: P con,T / D =v c,T / D (t)·i c,T / D (t); Among them, P con,T / D is the conduction loss of IGBT and diode; v c,T / D (t) represents the instantaneous on-state voltage drop; i c,T / D (t) represents the instantaneous on-current; The switching loss of the switching device can be expressed as: Among them, V dc is the DC bus voltage; V ref is the reference voltage; E sw,T / D (t) is the test reference loss; T sw is the switching action time of the switching device; The switching loss calculation formula of IGBT is: Among them, T on , T off It is expressed as the time of IGBT’s turn-on and turn-off action, and Eon and Eoff are single switching losses; The switching loss of the diode is: Among them, T off is the turn-off time of the diode, Ere is the reverse turn-off loss; The total loss caused by the power module can be expressed as: P loss_IGBT =P con,T +P con,D +P sw,T +P sw,D 。 5. The synchronous motor drive system analysis method according to claim 1, characterized in that: The core loss calculation can be expressed as: Among them, B rm Expressed as the amplitude of the radial component of magnetic flux density; B tm Expressed as the amplitude of the magnetic osculating component; k h is the hysteresis loss coefficient; k c is the eddy current loss coefficient; k e is the additional loss coefficient; f is the frequency; The calculation formula of the motor winding loss is: P Cu =mI 2 R; Wherein, m is the number of phases of the stator winding; I is the effective value of the current flowing through the stator winding, in A; R is the equivalent resistance of each phase winding, in Ω; The calculation formula of the permanent magnet eddy current loss is: Among them, V pm is the volume of permanent magnet; σ pm is the electrical conductivity of the permanent magnet; J is the eddy current density in the permanent magnet.

6. The synchronous motor drive system analysis method according to claim 5, characterized in that: The step of calculating the loss of the motor system at different switching frequencies according to the motor system loss analysis further includes: The motor drive system is operated at a rated speed of 1500rpm and a load of 10Nm. The inverter is controlled at switching frequencies of 1kHz, 2kHz, 4kHz, 8kHz, and 16kHz, and the single-phase current waveform output is observed. The inverter IGBT loss, diode and total loss were observed when the inverter switching frequency was 1kHz, 2kHz, 4kHz, 8kHz, 16kHz and 20kHz respectively; When the switching frequencies are 1kHz, 2kHz, 4kHz, 8kHz, 16kHz and 20kHz respectively, the motor stator core loss, rotor core loss, permanent magnet eddy current loss, winding copper loss and total motor loss are observed.

7. The synchronous motor drive system analysis method according to claim 1, characterized in that: The series of operating points are combinations of various motor speeds and load torques.

8. The synchronous motor drive system analysis method according to claim 1, characterized in that: The step of obtaining the switching frequency value when the efficiency of the electric drive system is the highest at each operating point, that is, the optimal switching frequency corresponding to the operating point, further includes: When selecting the optimal switching frequency, ensure that the switching frequency is more than 10 times the motor frequency to ensure motor control performance; Through comparison, the switching frequency that makes the electric drive system achieve the highest efficiency is selected.

9. The synchronous motor drive system analysis method according to claim 1, characterized in that: After the step of calculating the overall efficiency of the motor drive system according to the motor efficiency and the inverter efficiency, and obtaining the switching frequency value when the electric drive system has the highest efficiency at each operating point, that is, the optimal switching frequency corresponding to the operating point, the method further includes: Under each specific operating condition, an optimal switching frequency can be determined based on the efficiency of the electric drive system; The optimal switching frequency within the motor speed range under different load torque conditions is extracted into a switching frequency query control table, and the switching frequency query control table can specify a corresponding optimal switching frequency for each working condition according to a predetermined speed range and load torque range, forming a switching frequency matrix; Based on the switching frequency selection, a corresponding triangular carrier signal is generated to maximize the efficiency of the motor drive system.

10. A synchronous motor drive system analysis device, characterized in that: include: Model building module, used to build motor system coupling model; A loss analysis module, used for analyzing the motor system loss based on the coupling model; A loss calculation module, used to calculate the loss of the motor system at different switching frequencies according to the motor system loss analysis; The efficiency simulation module is used to select a series of operating points to simulate and obtain the operating efficiency of the motor and inverter under different switching frequency control; The efficiency calculation module is used to calculate the overall efficiency of the motor drive system based on the motor efficiency and the inverter efficiency, and obtain the switching frequency value when the electric drive system has the highest efficiency at each operating point, which is the optimal switching frequency corresponding to the operating point.

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