Control method for obtaining maximum efficiency torque ratio of built-in permanent magnet synchronous motor based on loss discrimination standard

Abstract

The invention provides a method for controlling the maximum efficiency torque ratio of a built-in permanent magnet synchronous motor based on a loss discrimination standard. The method comprises the following steps: acquiring an indirect discrimination standard equation F of maximum efficiency torque ratio control based on an IPMSM mathematical model considering the influence of iron loss; performing integral accumulation on the indirect discrimination standard equation F controlled by the maximum efficiency torque ratio by using an integrator, and when the output of the integrator is zero, outputting a corresponding d-axis current as a set d-axis current reference value; and setting a q-axis current reference value according to the IPMSM mathematical model considering the iron loss influence and motor parameters of the built-in permanent magnet synchronous motor. According to the method, the setting of the current reference value becomes easy to implement, the approximate simplification of the solving of the d-axis current reference value with the optimal efficiency is avoided, the accuracy of the setting of the current reference value is improved, and the setting of the current reference value meets the requirements of the optimal efficiency and the torque control precision.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet synchronous motor control technology, and in particular to a maximum efficiency torque ratio control method for a built-in permanent magnet synchronous motor. Background Art

[0002] The cruising range of electric vehicles is closely related to the efficiency of the motor. How to maximize the efficiency of the motor is of great significance to increasing the cruising range of new energy vehicles and reducing energy consumption per 100 kilometers.

[0003] Torque control accuracy is a key indicator for measuring the operating performance of electric vehicles. Torque control accuracy affects the acceleration time from 0 to 100 km / h on the one hand, and the driving safety level on the other. The setting of the d-axis and q-axis current reference values ​​is an intrinsic factor that affects the operating efficiency and torque control accuracy of the built-in permanent magnet synchronous motor. Therefore, the setting of the d-axis and q-axis current reference values ​​of the built-in permanent magnet synchronous motor that takes into account both efficiency and torque control accuracy is of great significance to the efficient and reliable operation of electric vehicles.

[0004] There are two main types of current reference value allocation strategies for the d-axis and q-axis currents: one is the maximum torque-to-current ratio control (MTPA), and the other is the minimum loss control (LMC) based on the iron loss mathematical model.

[0005] For MTPA control, according to different constraints, it can be divided into: MTPA with current amplitude as constraint and MTPA with output torque as constraint. According to different implementation methods, it can be subdivided into: analytical method, search method, table lookup method and signal injection method. Although the MTPA control method can improve the efficiency of the built-in permanent magnet synchronous motor (IPMSM) to a certain extent. However, this method does not take into account the influence of iron loss, which is also a key factor affecting motor efficiency and torque output. Therefore, MTPA control cannot achieve the maximum efficiency output and the most accurate torque control of IPMSM.

[0006] Similarly, according to different constraints, LMC can be divided into two types. One is the current amplitude as the constraint, which is currently widely referred to as the maximum efficiency current ratio control (MEPA). The other is the torque constraint. In order to distinguish it from MEPA, this paper refers to the LMC with torque as the constraint as the maximum efficiency torque ratio control (MEPT). According to different implementation methods, LMC can be subdivided into: model method, search method and pseudo-search method. The model method is to establish a mathematical model containing the motor iron loss and derive the d and q axis current reference values ​​that can minimize the loss through approximate processing. However, the model method has good speed, but the accurate solution of the current reference value is difficult, and the approximate processing will bring certain errors. The search method is to scan the current vector angle and search for the minimum current reference or the minimum bus input power online to achieve minimum loss control. However, this method requires the input power to be detected and requires additional hardware circuits. The pseudo-search method is a method that combines the motor loss model and the search method. Compared with the model method, this method adds the iterative search process of the optimal d-axis current reference value, avoiding the complex solution of the current reference value; compared with the search method, this method does not require the input power to be detected. In view of these advantages, the pseudo-search method has attracted widespread attention from many scholars.

[0007] Reference [C.Cavallaro,AODi Tommaso,R.Miceli,A.Raciti,GRGalluzzo andM.Trapanese,“Efficiency enhancement of permanent-magnet synchronous motordrives by online loss minimization approaches,”IEEE Trans.Ind.Electron.,vol.52,no.4,pp.1153-1160,Aug.2005] uses the dichotomy method and the established mathematical model of motor loss to realize the online search of the current vector angle that satisfies the minimum loss constraint. Reference [M.Sreejeth,M.Singh and P.Kumar,“Particle swarm optimisation in efficiency improvement of vector controlledsurface mounted permanent magnet synchronous motor drive,”IET PowerElectronics.,vol.8,no.5,pp.760-769,2015.] uses the ant colony algorithm to search for the d-axis current when the motor efficiency is the highest. The literature [R.Ni,D.Xu,G.Wang,L.Ding,G.Zhang,and L.Qu,“Maximum efficiency perampere control of permanent-magnet synchronous machines,”IEEE Trans.Ind.Electron.,vol.62,no.4,pp.2135-2143,April 2015.] scans the current vector angle and uses the established motor loss model to online calculate the motor loss generated to obtain the current vector angle that meets the minimum loss constraint.Reference [M.Li, S.Huang, X.Wu, K.Liu, X.Peng, and G.Liang, “A virtual HF signalinjection based maximum efficiency per ampere tracking control for IPMSMdrive,” IEEE Trans.Power Electron., vol.35, no.6, pp.6102-6113, Jun.2020.] uses virtual square wave signal injection to calculate the motor loss before and after signal injection, and then extracts the derivative information of efficiency with respect to the current vector angle. Finally, the extracted derivative information is used to realize the setting of the d-axis current reference value. However, the existing pseudo-search method is only applicable to the maximum efficiency current ratio control (MEPA) control, and cannot be applied to the control with torque as the constraint condition. Therefore, the pseudo-search method that takes into account both the optimal motor efficiency and the torque control accuracy needs to be further studied. Based on the above analysis, in applications where the internal permanent magnet synchronous motor (IPMSM) is required to work in the torque control mode, how to set the d and q axis current reference values ​​is a very meaningful and challenging task. Summary of the invention

[0008] In view of the technical problem that the prior art cannot take into account both the optimal motor efficiency and the torque control accuracy, the present invention proposes a maximum efficiency torque ratio control method for a built-in permanent magnet synchronous motor based on a loss discrimination standard. In order to distinguish it from the maximum efficiency current ratio control (MEPA) control, the LMC with torque as the constraint condition is called the maximum efficiency torque ratio control (MEPT). According to the mathematical model of the IPMSM motor considering iron loss, the present invention establishes an extreme value solution condition that satisfies the torque control accuracy and the minimum loss, and proposes an indirect discrimination standard F that reflects the loss of the built-in permanent magnet synchronous motor (IPMSM). Then, based on the indirect discrimination standard F, a current reference value setting method that satisfies the maximum efficiency torque ratio control (MEPT) control is designed, thereby improving the accuracy of the current reference value setting.

[0009] In order to achieve the above object, the technical solution of the present invention is achieved as follows:

[0010] A method for controlling the maximum efficiency torque ratio of a built-in permanent magnet synchronous motor based on a loss discrimination standard comprises the following steps:

[0011] S1: Obtain the indirect judgment standard equation F of maximum efficiency torque ratio control based on the IPMSM motor mathematical model considering the influence of iron loss;

[0012] S2: using an integrator to integrate and accumulate the indirect judgment standard equation F of the maximum efficiency torque ratio control. When the integrator output is zero, the output value is used as the d-axis current reference value;

[0013] S3: Set the q-axis current reference value according to the IPMSM motor mathematical model considering the influence of iron loss.

[0014] Furthermore, the method for obtaining the indirect judgment standard equation F for maximum efficiency torque ratio control is: obtaining the preliminary judgment standard equation for maximum efficiency torque ratio control based on the mathematical model of the IPMSM motor taking into account the influence of iron loss; simplifying the preliminary judgment standard equation to obtain the direct judgment standard equation F0 for maximum efficiency torque ratio control; and simplifying the parameters of the direct judgment standard equation F0 for maximum efficiency torque ratio control to obtain the indirect judgment standard equation F for maximum efficiency torque ratio control.

[0015] Furthermore, the torque equation of the IPMSM motor mathematical model considering the influence of iron loss is:

[0016]

[0017] Among them, i dt 、i qt are the d-axis and q-axis current torque components that actually generate torque in the stator d-axis and q-axis currents, respectively. d , L q are the d-axis and q-axis inductances, respectively, T e is the electromagnetic torque, λ f is the permanent magnet flux, n p is the number of pole pairs of the motor.

[0018] Further, the method for obtaining the preliminary judgment standard equation of the maximum efficiency torque ratio control according to the IPMSM motor mathematical model considering the influence of iron loss is specifically as follows: according to the IPMSM motor mathematical model considering the influence of iron loss, the current torque component i is obtained. dt 、i qt and d and q axis current i d 、i q According to the relationship A among them, the loss equation and the extreme value solution equation and constraint conditions of the maximum efficiency torque ratio control are simplified by implicit function derivation to obtain the preliminary judgment standard equation of the maximum efficiency torque ratio control.

[0019] Furthermore, the extreme value solution equation and constraint conditions of the maximum efficiency torque ratio control are:

[0020]

[0021] Among them, P loss is the total loss, P cuis the copper loss, P Fe is the iron loss, st represents the constraint condition, i d 、i q are the d-axis and q-axis currents of the stator winding respectively;

[0022] The method for simplifying the extreme value solution equation by derivative of implicit function is:

[0023] When IPMSM is in torque control mode, the actual output torque T e Equal to the given torque T e_ref , according to the constraints of maximum efficiency torque ratio control, the total loss P loss The premise for obtaining the minimum value is that the torque satisfies the function According to the relation A and the loss equation, the extreme value solution equation and constraint conditions of the maximum efficiency torque ratio control are further expressed as:

[0024]

[0025] The extreme point of total loss is at the total loss P loss The d-axis current torque component i dt When the partial derivative of is zero, the extreme value solution equation is fully differentially expanded to obtain the total differential equation I:

[0026]

[0027] Function Regarding the d-axis current torque component i dt Taking the derivative of the implicit function, we get the total differential equation II:

[0028]

[0029] According to total differential equation I and total differential equation II, the preliminary judgment standard equation of maximum efficiency torque ratio control is obtained:

[0030]

[0031] Further, the method of simplifying the preliminary judgment standard equation to obtain the direct judgment standard equation F0 of the maximum efficiency torque ratio control is specifically as follows: the preliminary judgment standard equation of the maximum efficiency torque ratio control is fully differentially expanded to obtain the total differential equation III, and the mathematical model expression of the motor under steady-state conditions is obtained according to the torque equation, loss equation, and relation A of the mathematical model of the IPMSM motor considering the influence of iron loss; the direct judgment standard equation F0 that satisfies the maximum efficiency torque ratio control is obtained according to the preliminary judgment standard equation of the maximum efficiency torque ratio control, the total differential equation III, and the mathematical model expression of the motor under steady-state conditions:

[0032]

[0033] Among them, R s is the resistance of the stator winding, R Fe is the iron loss resistance, ω e is the electrical angular velocity.

[0034] Furthermore, the method of performing parameter simplification on the direct judgment standard equation F0 for maximum efficiency torque ratio control to obtain the indirect judgment standard equation F for maximum efficiency torque ratio control is specifically as follows: the mathematical relationship related to the motor parameters is obtained according to the steady-state voltage equation of the IPMSM motor mathematical model considering the influence of iron loss; the indirect judgment standard equation F for maximum efficiency torque ratio control is obtained by combining the mathematical relationship related to the motor parameters and the direct judgment standard equation F0 for maximum efficiency torque ratio control.

[0035] The indirect judgment standard equation F of the maximum efficiency torque ratio control is:

[0036]

[0037] The method for setting the q-axis current reference value described in step S3 is: according to the torque equation of the IPMSM motor mathematical model considering the influence of iron loss, a q-axis current reference value setting formula II including the derivative of the torque with respect to the q-axis current torque component is obtained, and the derivative expression of the torque with respect to the q-axis current torque component is obtained by combining the mathematical relationship related to the motor parameters and the torque equation of the IPMSM motor mathematical model considering the influence of iron loss, and the motor parameters are set using the derivative expression of the torque with respect to the q-axis current torque component, and finally the q-axis current reference value is set using the q-axis current reference value setting formula II.

[0038] Furthermore, the q-axis current reference value setting formula is:

[0039]

[0040] in, i qref Indicates the q-axis current reference value.

[0041] The beneficial effects of the present invention are as follows: the method not only avoids the complex solution process of high-order nonlinear equations in the efficiency optimization of the internal permanent magnet synchronous motor (IPMSM), making the current reference value setting easy to implement, but also avoids the approximate simplification of the solution of the current reference value for optimal efficiency, thereby improving the accuracy of the current reference value setting, so that the setting of the current reference value takes into account the requirements of optimal efficiency and torque control accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 It is a schematic diagram of the process of the present invention.

[0044] Figure 2 This is a block diagram of the current reference value setting of the present invention.

[0045] Figure 3 It is a variation trend diagram of the judgment standard F and the total loss of the present invention as the d-axis current changes.

[0046] Figure 4 This is a control block diagram of efficiency optimization of a built-in permanent magnet synchronous motor based on maximum efficiency torque ratio control according to the present invention.

[0047] Figure 5 This is a mathematical model diagram of the IPMSM motor of the present invention taking into account the influence of iron loss.

[0048] Figure 6 The figure is a curve diagram showing the change of the motor iron loss resistance with the rotation speed ω according to the present invention.

[0049] Figure 7 The efficiency line graphs obtained by different methods are shown when the motor of the present invention is at different torques of 1000 r / min.

[0050] Figure 8 The efficiency line graphs obtained by different methods when the motor of the present invention is at different torques of 1500r / min.

[0051] Fig. 9 The efficiency line graphs obtained by different methods are shown when the motor of the present invention is at different torques of 2000 r / min.

[0052] Fig.10 The experimental results of d-axis current and phase current of the motor of the present invention are shown in different methods with given torques of 2Nm, 4Nm, 6Nm and 8Nm at 1000r / min. (a) is the maximum torque current ratio MTPA method; (b) is the maximum efficiency current ratio method; (c) is the method of the present invention.

[0053] Fig.11From top to bottom, they are the experimental result diagrams of the d-axis current, q-axis current, indirect discrimination mark F and phase current of the present invention at different speeds for given torques of 2Nm, 4Nm, 6Nm and 8Nm, (a) is 1000r / min; (b) is 1500r / min; (c) is 2000r / min. DETAILED DESCRIPTION

[0054] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] A maximum efficiency torque ratio control method for an interior permanent magnet synchronous motor based on loss discrimination criteria is provided. Figure 1 As shown, the steps include:

[0056] S1: Based on the IPMSM motor mathematical model considering the influence of iron loss, the indirect judgment standard equation F of maximum efficiency torque ratio control is obtained. Figure 5 As shown in Figure 1, the mathematical model of the IPMSM motor considering the influence of iron loss is shown in Figure 1. The corresponding steady-state voltage equation and torque equation are shown in Figure 1.

[0057] Steady-state voltage equation:

[0058]

[0059] Torque equation:

[0060]

[0061] The model parameters are as follows: d 、u q are the d-axis and q-axis voltages of the stator winding, respectively, dt 、i qt are the d-axis and q-axis current torque components that actually generate torque in the d-axis and q-axis currents, respectively. s is the resistance of the stator winding, R Fe is the iron loss resistance, ω e is the electrical angular velocity, p is the differential operator, L d , L q The d and q axis inductances, T e is the electromagnetic torque, λ f is the permanent magnet flux.

[0062] Among them, the resistance of the stator winding R s , iron loss resistor R Fe , permanent magnet flux λf 、Number of motor pole pairs n p and d and q axis inductance L d , L q are the motor parameters.

[0063] Furthermore, the d-axis and q-axis current torque components i are obtained according to the IPMSM motor mathematical model considering the influence of iron loss. dt 、i qt and d and q axis current i d 、i q The relationship between them is A:

[0064]

[0065] The extreme value solution equations and constraints of the maximum efficiency torque ratio control (MEPT) are:

[0066]

[0067] The loss equation is:

[0068]

[0069] Among them, P loss is the total loss, P cu is the copper loss, P Fe is the iron loss, and st represents the constraint condition.

[0070] Furthermore, when the IPMSM is in torque control mode, the actual output torque T e Equal to the given torque T e_ref According to formula (5), the total loss P loss The premise for obtaining the minimum value is that the torque satisfies the following function:

[0071]

[0072] From the relation A (3) and the loss equation (6), we know that the total loss P loss Can represent i dt and i qt As a function of, the extreme value solution equation and constraint conditions of maximum efficiency torque ratio control can be further expressed as:

[0073]

[0074] Torque T e At a certain time, qt It can be expressed as the d-axis current torque component i dt The function of the total loss is the extreme point of the total loss P loss The d-axis current torque component i dtWhen the partial derivative is zero, the extreme value of the loss is solved and the total differential equation is expanded to obtain the total differential equation I:

[0075]

[0076] Function Regarding the d-axis current torque component i dt By taking the derivative of the implicit function, we can get the total differential equation II:

[0077]

[0078] Combining total differential equation I, equation (7), and total differential equation II, equation (8), we get the preliminary judgment standard equation for maximum efficiency torque ratio control:

[0079]

[0080] However, the above equation is not easy to solve because the total loss P loss is the sum of copper loss and iron loss, and the copper loss is most simply expressed as a function of the stator current. Therefore, it can be simplified as follows. The preliminary judgment standard equation (9) for maximum efficiency torque ratio control is expanded step by step, and the total loss P is loss Expanded into a function of copper loss and iron loss, we can further obtain and The result of total differential expansion is total differential equation III:

[0081]

[0082] Furthermore, in order to obtain the derivative information in the expansion, according to the torque equation (2), the relationship A (3) and the loss equation (6), the following mathematical model expression of the motor in steady state can be obtained:

[0083]

[0084] Furthermore, by combining the preliminary judgment standard equation of maximum efficiency torque ratio control, namely equation (9), the total differential equation III, namely equation (10), and the mathematical model expression of the motor under steady-state conditions, namely equation (11), the direct judgment standard equation F0 that satisfies the maximum efficiency torque ratio control can be obtained. The specific formula is as follows:

[0085]

[0086] Furthermore, in order to avoid the influence of motor parameters (permanent magnet flux λ f and q-axis inductance L q ), according to the steady-state voltage equation of the IPMSM motor mathematical model considering the influence of iron loss, the following mathematical relationship related to the motor parameters is obtained:

[0087]

[0088] Furthermore, the mathematical relationship (13) related to the motor parameters is substituted into the direct judgment standard equation F0 of the maximum efficiency torque ratio control, that is, equation (12), to obtain the indirect judgment standard equation F that ultimately satisfies the maximum efficiency torque ratio control:

[0089]

[0090] The simplified indirect judgment criteria for the maximum efficiency torque ratio control only include the motor parameter d-axis inductance L d , stator winding resistance R s and iron loss resistor R Fe , reducing the permanent magnet flux λ f and q-axis inductance L q , thereby reducing the dependence of the indirect judgment standard equation F on the motor parameters.

[0091] The indirect judgment standard equation F has the characteristics of crossing zero and the zero point corresponds to the lowest point of total loss. It reflects the loss of the interior permanent magnet synchronous motor (IPMSM), such as Figure 3 As shown in the figure, it is a trend diagram of the indirect judgment standard equation F and the total loss with the change of d-axis current under a certain constant torque. It can be seen from the figure that as the d-axis current changes, the value of the indirect judgment standard equation F changes in a linear function, and when the total loss of the motor is the smallest, the value of the indirect judgment standard equation F is zero. Therefore, the indirect judgment standard equation F can be used as a judgment standard to reflect the total loss of the built-in permanent magnet synchronous motor, and the method of giving the design current reference value of the indirect judgment standard equation F can be used to achieve the optimization of the efficiency of the built-in permanent magnet synchronous motor.

[0092] S2: The indirect judgment standard equation F of the maximum efficiency torque ratio control is integrated and accumulated by using an integrator. When the integrator output is zero, the output value is used as the d-axis current reference value.

[0093] The setting method of d-axis current reference value is as follows: Figure 2 As shown, the d and q axis voltages u of the built-in permanent magnet synchronous motor are obtained in real time. d 、u q ; d, q axis current i d 、i q ; and the motor parameters (including the stator winding resistance R s , iron loss resistor R Fe and d-axis inductance L d) is substituted into the indirect judgment standard formula of maximum efficiency torque ratio control. In this embodiment, it is realized by using an integrator to perform real-time calculation in DSP. When F≠0, under the action of the integrator, the d-axis current reference value will be gradually adjusted until F=0. At this time, the d-axis current reference value point under the efficiency optimal control is reached.

[0094] S3: Set the q-axis current reference value according to the IPMSM motor mathematical model considering the influence of iron loss.

[0095] Setting method of q-axis current reference value: In order to ensure the torque output accuracy, according to the torque equation in the IPMSM motor mathematical model considering the influence of iron loss, the q-axis current reference value setting formula I is:

[0096]

[0097] Among them, i qFe is the q-axis current component that causes iron loss, T e_ref It is the given value of the output torque when IPMSM is in torque control mode.

[0098] From the torque equation, formula (2), it can be seen that the denominator of formula (15) is the derivative of the torque with respect to the torque component of the q-axis current. Therefore, the q-axis current reference value setting formula II is:

[0099]

[0100] Where i qFe is the iron loss component of the q-axis current:

[0101]

[0102] Furthermore, the torque equation in the mathematical model of the IPMSM motor considering the influence of iron loss is combined with the mathematical relationship (13) related to the motor parameters, and the derivative of the torque in the q-axis current reference value setting formula (16) to the q-axis current torque component is It can be further expressed as the derivative expression of the torque to the q-axis current torque component:

[0103]

[0104] like Figure 2 As shown, the d and q axis voltages u of the built-in permanent magnet synchronous motor are obtained in real time. d 、u q ; d, q axis current i d 、i q ; and the motor parameters (including the stator winding resistance R s , iron loss resistor R Fe) is substituted into the derivative expression of the torque with respect to the q-axis current torque component, i.e., equation (18), and the q-axis current reference value setting formula II, i.e., equation (16), is used to realize the online setting of the q-axis current reference value. This embodiment is realized by real-time calculation in DSP.

[0105] like Figure 4 As shown, by setting the d-axis current reference value and the q-axis current reference value, the maximum efficiency torque ratio control of the built-in permanent magnet synchronous motor is realized. In order to conveniently explain how to realize the maximum efficiency torque ratio control of the built-in permanent magnet synchronous motor, the process is briefly described below.

[0106] 1. Sample the three-phase current i of abc at the motor end a 、i b 、i c Electrical angular velocity ω e , and then the d and q axis voltages and currents are obtained through Clark, Park transformation and PI controller. The d and q axis voltages used need to consider the influence of digital control delay and inverter nonlinear voltage and need to be compensated;

[0107] 2. Substitute the d-axis and q-axis voltage and current, stator resistance, and iron loss resistance into the indirect judgment standard F and implement the d-axis current reference value setting in the DSP through the integrator. The q-axis current reference value is obtained by formula (16), thereby realizing the online setting of the d-axis current reference value and the q-axis current reference value under the minimum loss of the built-in permanent magnet synchronous motor;

[0108] 3. The d and q current reference values ​​are converted into d and q axis voltages by PI controller, which are then input into space vector pulse width modulation (SVPWM) after inverse park transformation to generate a control signal acting on the inverter. The modulation signal controls the motor by controlling the three-phase voltage generated by the inverter.

[0109] The above process is not the focus of the present invention, and is only a brief description of the process.

[0110] In order to verify the feasibility of the proposed method, an experimental system was built. The parameters of the built-in permanent magnet synchronous motor are shown in Table 1. In the experimental system, the control unit uses TMS320F28335. The sampling frequency of the control system is 10kHz, the control cycle is 100μs, and the dead time is set to 2.6μs. During the experiment, the motor under test is in torque control mode, and the towing motor is in speed control mode.

[0111] The input power of the motor under test is measured by an integrated high-sensitivity voltage probe, high-precision current clamp and MDA805A electric drive analyzer, and the output power is measured by a torque sensor.

[0112] Table 1 Parameters of built-in permanent magnet synchronous motor

[0113]

[0114] In order to avoid the influence of motor parameters, the iron loss resistor R Fe The measured curve of the iron loss resistance of the tested motor changing with the speed ω is as follows: Figure 6 As shown. The resistance of the stator winding R s It is obtained through the built-in thermistor of the motor and the relationship between the thermistor resistance and temperature. The specific relationship is as follows:

[0115] R s =R s0 (1+k(T-T0));

[0116] Where k is the temperature coefficient, R s0 is the stator winding resistance value at temperature T0, T is the current motor temperature. d-axis inductance L d The values ​​obtained by finite element analysis are obtained by curve fitting.

[0117] In order to verify the efficiency optimization effect of the proposed method, the optimal efficiency value and the corresponding d-axis current value were measured by a power analyzer when the motor torque was 2Nm, 4Nm, 6Nm, 8Nm and the speed was 1000r / min, 1500r / min and 2000r / min.

[0118] Then, under the same working conditions, the motor is controlled using the MTPA control method, the maximum efficiency current ratio algorithm proposed in literature A [Z.Xinghua and C.Pengfei, “Efficiency optimization of direct torque controlled interior permanent magnet motor considering iron losses,” IEEE 19th Int.Conf.Elect.Mach.Syst., pp.1–5, 2016.], and the method proposed in the present invention. The motor efficiency, d-axis current value, and related waveforms under different control methods are recorded. Table 2 shows the efficiency comparison of different methods, and Table 3 shows the d-axis current reference values ​​obtained by different methods.

[0119] Figure 7 The efficiency line graphs obtained by different methods when the motor is at different torques of 1000r / min; Figure 8 The efficiency line graphs obtained by different methods when the motor is at different torques of 1500r / min; Fig. 9 The efficiency line graphs obtained by different methods when the motor is at different torques of 2000r / min are shown in the figure. Figure 7 , Figure 8 and Fig. 9 It can be seen that the method of the present invention can achieve higher efficiency compared with other methods.

[0120] Fig.10 The d-axis current and phase current of the proposed method under the given torque of 2Nm, 4Nm, 6Nm and 8Nm for the motor at 1000r / min. (a) Maximum torque current ratio MTPA method; (b) Maximum efficiency current ratio method; (c) The method proposed by the present invention.

[0121] Combined with Table 3, it can be seen that at 1000r / min given torques of 2Nm, 4Nm, 6Nm, and 8Nm, compared with the maximum torque current ratio and the maximum efficiency current ratio comparison algorithms, the proposed algorithm can more accurately track the d-axis current corresponding to the maximum efficiency point. Combined with Table 2, it can be concluded that the motor efficiency of the proposed algorithm is higher than that of the comparison algorithm.

[0122] Fig.11 From top to bottom, the d-axis current, q-axis current, indirect discrimination mark F, and phase current of the proposed method under given torques of 2Nm, 4Nm, 6Nm, and 8Nm are shown in order. (a) 1000r / min; (b) 1500r / min; (c) 2000r / min.

[0123] Combined with Table 3, it can be seen that the proposed algorithm can accurately track the d-axis current corresponding to the maximum efficiency point at different speeds of 1000r / min, 1500r / min, 2000r / min and given torques of 2Nm, 4Nm, 6Nm, and 8Nm. Combined with Table 2, it can be seen that the proposed algorithm can more accurately track the maximum efficiency point of the motor under different working conditions.

[0124] Table 2

[0125]

[0126] Table 3

[0127]

[0128] The phase current is minimum under MTPA control, but the motor efficiency is not optimal, because MTPA control ignores the influence of iron loss. In addition, the efficiency obtained by the method proposed in the document A deviates from the maximum efficiency point of the motor, because although the method takes into account the motor iron loss, the simplified calculation formula is used to solve the d-axis current at the maximum efficiency. The method proposed in the present invention takes into account the influence of motor iron loss, and uses the judgment standard reflecting the loss of the built-in permanent magnet synchronous motor to realize the setting of the d-axis current reference value. At the same time, the method not only avoids the complex solution process of high-order nonlinear equations in the efficiency optimization of the built-in permanent magnet synchronous motor, but also avoids the approximate simplification of the solution of the d-axis current reference value with the best efficiency, and improves the accuracy of the current reference value setting. Therefore, the method proposed in the present invention has a good efficiency optimization effect.

[0129] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling the maximum efficiency torque ratio of an interior permanent magnet synchronous motor based on a loss discrimination standard, characterized in that: Includes steps: S1: Obtain the indirect judgment standard equation F of maximum efficiency torque ratio control based on the IPMSM motor mathematical model considering the influence of iron loss; S2: using an integrator to integrate and accumulate the indirect judgment standard equation F of the maximum efficiency torque ratio control. When the integrator output is zero, the output value is used as the d-axis current reference value; S3: Set the q-axis current reference value according to the IPMSM motor mathematical model considering the influence of iron loss.

2. The maximum efficiency torque ratio control method of an interior permanent magnet synchronous motor based on loss discrimination criteria according to claim 1 is characterized in that: The method for obtaining the indirect judgment standard equation F of the maximum efficiency torque ratio control is: obtaining the preliminary judgment standard equation of the maximum efficiency torque ratio control according to the IPMSM motor mathematical model considering the influence of iron loss; The preliminary judgment standard equation is simplified to obtain the direct judgment standard equation F0 of the maximum efficiency torque ratio control; the direct judgment standard equation F0 of the maximum efficiency torque ratio control is simplified by parameters to obtain the indirect judgment standard equation F of the maximum efficiency torque ratio control.

3. The maximum efficiency torque ratio control method of an interior permanent magnet synchronous motor based on loss discrimination criteria according to claim 2 is characterized in that: The torque equation of the IPMSM motor mathematical model considering the influence of iron loss is: Among them, i dt 、i qt are the d-axis and q-axis current torque components that actually generate torque in the stator d-axis and q-axis currents, respectively. d , L q are the d-axis and q-axis inductances, respectively, T e is the electromagnetic torque, λ f is the permanent magnet flux, n p is the number of pole pairs of the motor.

4. The maximum efficiency torque ratio control method of an interior permanent magnet synchronous motor based on loss discrimination criteria according to claim 3 is characterized in that: The method for obtaining the preliminary judgment standard equation of the maximum efficiency torque ratio control according to the IPMSM motor mathematical model considering the influence of iron loss is specifically as follows: according to the IPMSM motor mathematical model considering the influence of iron loss, the current torque component i is obtained. dt 、i qt and d and q axis current i d 、i q According to the relationship A among them, the loss equation and the extreme value solution equation and constraint conditions of the maximum efficiency torque ratio control are simplified by implicit function derivation to obtain the preliminary judgment standard equation of the maximum efficiency torque ratio control.

5. The maximum efficiency torque ratio control method of an interior permanent magnet synchronous motor based on loss discrimination criteria according to claim 4 is characterized in that: The extreme value solution equation and constraint conditions of the maximum efficiency torque ratio control are: Among them, P loss is the total loss, P cu is the copper loss, P Fe is the iron loss, st represents the constraint condition, i d 、i q are the d-axis and q-axis currents of the stator winding respectively; The method for simplifying the extreme value solution equation by derivative of implicit function is: When IPMSM is in torque control mode, the actual output torque T e Equal to the given torque T e_ref , according to the constraints of maximum efficiency torque ratio control, the total loss P loss The premise for obtaining the minimum value is that the torque satisfies the function According to the relation A and the loss equation, the extreme value solution equation and constraint conditions of the maximum efficiency torque ratio control are further expressed as: The extreme point of total loss is at the total loss P loss The d-axis current torque component i dt When the partial derivative of is zero, the extreme value solution equation is fully differentially expanded to obtain the total differential equation I: Function Taking the implicit function derivative of the d-axis current torque component idt, we get the total differential equation II: According to total differential equation I and total differential equation II, the preliminary judgment standard equation of maximum efficiency torque ratio control is obtained:

6. The maximum efficiency torque ratio control method of an interior permanent magnet synchronous motor based on loss discrimination criteria according to claim 5 is characterized in that: The method of simplifying the preliminary judgment standard equation to obtain the direct judgment standard equation F0 of the maximum efficiency torque ratio control is specifically as follows: the preliminary judgment standard equation of the maximum efficiency torque ratio control is fully differentially expanded to obtain the total differential equation III, and the mathematical model expression of the motor under steady-state conditions is obtained according to the torque equation, loss equation, and relation A of the mathematical model of the IPMSM motor considering the influence of iron loss; the direct judgment standard equation F0 that satisfies the maximum efficiency torque ratio control is obtained according to the preliminary judgment standard equation of the maximum efficiency torque ratio control, the total differential equation III, and the mathematical model expression of the motor under steady-state conditions: Among them, R s is the resistance of the stator winding, R Fe is the iron loss resistance, ω e is the electrical angular velocity.

7. The maximum efficiency torque ratio control method of an interior permanent magnet synchronous motor based on loss discrimination criteria according to claim 6 is characterized in that: The method of performing parameter simplification on the direct judgment standard equation F0 for maximum efficiency torque ratio control to obtain the indirect judgment standard equation F for maximum efficiency torque ratio control is specifically as follows: obtaining the mathematical relationship related to the motor parameters based on the steady-state voltage equation of the IPMSM motor mathematical model considering the influence of iron loss; combining the mathematical relationship related to the motor parameters and the direct judgment standard equation F0 for maximum efficiency torque ratio control to obtain the indirect judgment standard equation F for maximum efficiency torque ratio control.

8. The maximum efficiency torque ratio control method of an interior permanent magnet synchronous motor based on loss discrimination criteria according to claim 7 is characterized in that: The indirect judgment standard equation F of the maximum efficiency torque ratio control is:

9. The maximum efficiency torque ratio control method for an interior permanent magnet synchronous motor based on loss discrimination criteria according to any one of claims 4 to 8, characterized in that: The method for setting the q-axis current reference value described in step S3 is: according to the torque equation of the IPMSM motor mathematical model considering the influence of iron loss, a q-axis current reference value setting formula II including the derivative of the torque with respect to the q-axis current torque component is obtained, and the derivative expression of the torque with respect to the q-axis current torque component is obtained by combining the mathematical relationship related to the motor parameters and the torque equation of the IPMSM motor mathematical model considering the influence of iron loss, and the motor parameters are set using the derivative expression of the torque with respect to the q-axis current torque component, and finally the q-axis current reference value is set using the q-axis current reference value setting formula II.

10. The maximum efficiency torque ratio control method of an interior permanent magnet synchronous motor based on loss discrimination criteria according to claim 9, characterized in that: The q-axis current reference value setting formula is: in, i qref Indicates the q-axis current reference value.

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