Abstract: Based on the mathematical model of an elevator asynchronous motor in a synchronous rotating coordinate system considering iron loss, this paper studies the relationship between motor loss and rotor flux under different operating conditions to achieve optimized control of a vector-controlled variable frequency speed regulation asynchronous motor. To further improve the motor's speed regulation performance, based on the basic principles of motor vector control, a hardware implementation of vector control is presented using a digital signal processor and intelligent power module, and the software implementation method of the system is described. Experiments show that the vector control variable frequency speed regulation system for elevator asynchronous motors can operate smoothly and has good static and dynamic characteristics, and can be widely applied to the electrical drive system driven by elevator motors. Keywords: Elevator asynchronous motor; Vector control; Iron loss; Optimal control [b][align=center]Optimal Control of VVVF Speed ​​Regulation Motor for Elevator based on DSP&IPM[/align][/b] 0 Introduction With the development of urban construction, the requirements for the motor speed regulation system of elevators in high-rise buildings are becoming increasingly stringent. Due to the limitations of digital analysis methods and tools, iron loss is usually ignored when establishing dynamic mathematical models and simulation models of elevator asynchronous motors. Iron loss in the asynchronous motor of the elevator does exist, which will cause the output torque to deviate and affect the control accuracy [1]. At the same time, since the implementation of vector control requires real-time completion of multiple functions such as coordinate transformation, current and speed detection, flux estimation, PWM signal generation and fault protection, the control algorithm involves a large amount of real-time calculation. In the past, the implementation structure of such high-performance AC elevator asynchronous motor control system was quite complex [2]. In recent years, due to the progress of microelectronics and computer technology, especially the emergence of digital signal processors (DSP) and intelligent power modules (1PM) with strong computing power, it has become possible to design a simple vector system. This paper elaborates on the hardware composition of the vector control system and the software design method of the optimization algorithm. Experimental results show that the implementation of the vector control system has excellent dynamic and static speed regulation performance. It is a speed regulation system with strong real-time performance and excellent performance. The variable frequency speed regulation elevator has the advantages of energy saving, fast lifting speed, accurate leveling and good comfort, which provides power guarantee. 1 Control Principle 1.1 Mathematical Model of Elevator Asynchronous Motor in Synchronous Rotating Coordinate System dq Axis Considering Iron Loss According to AC motor theory, elevator asynchronous motor can be equivalently transformed into a two-phase motor model in synchronous rotating coordinate system dq axis through coordinate transformation. Compared with the conventional dq axis motor model, two iron loss equivalent windings are added to the stator. Thus, the equivalent circuit of asynchronous motor in synchronous rotating coordinate system dq axis considering iron loss can be obtained as shown in Figure 1 [3]. [align=center] Figure 1 Equivalent circuit of asynchronous motor in synchronous rotating coordinate system dq axis considering iron loss[/align] Take the rotational speed of dq axis as equal to the synchronous angular velocity of stator ω[sub]1[/sub], the angular speed of rotor as ω[sub]r[/sub], and the angular velocity of dq axis relative to rotor as ω[sub]s[/sub]=ω[sub]1[/sub]-ω[sub]r[/sub], that is, slip. Based on the above equivalent circuit, the mathematical model of the asynchronous motor in any two-phase synchronous rotating coordinate system is derived: Equations (a) to (e) constitute the dynamic mathematical model of the asynchronous motor in any synchronous rotating coordinate system when considering iron loss. 1.2 Magnetic flux optimization module Since the total loss of the motor is equal to the difference between the input power and the output power, it can be seen from the above equation that, assuming the motor parameters remain unchanged, under certain rotor angular frequency and certain load torque Te conditions, the controllable loss of the asynchronous motor is related to the size of the rotor magnetic flux. Ignoring mechanical loss and stray loss, the asynchronous motor has the highest efficiency when the loss is minimized when the output power is constant [4]. The loss is a convex function, so by differentiating the above equation and setting it to zero, the optimal magnetic flux with the minimum loss can be obtained; where 2 is the system hardware design based on DSP & IPM The hardware structure of the asynchronous motor vector control system for elevators is shown in Figure 2. The whole system is mainly composed of three modules: the main circuit power conversion module with the intelligent power module PS21867 as the core; the operation control module with DSP as the main component; and the signal detection module composed of incremental photoelectric encoder, Hall sensor, etc. [align=center]Figure 2 Hardware Structure Diagram of the Asynchronous Motor Control System for Elevators[/align] 2.1 Power Conversion Module The main circuit of the system adopts an AC-DC-AC voltage source frequency converter circuit. The selected inverter power device is a small dual in-line package IPM (PS21867) from Mitsubishi Corporation. This new DIP-IPM utilizes the latest 5th generation IGBT technology, which greatly improves its static and dynamic performance compared to the past. Furthermore, due to the adoption of the most advanced submicron power chip design technology and optimized module design technology and packaging process, it can not only be directly connected to the control MCU terminals and use a single power supply for bootstrapping, but also change its input logic from low-level active to high-level active. This greatly simplifies the interface circuit design and improves the cost-effectiveness of the inverter system. 2.2 Operation and Control Unit The control system uses a digital signal processor TMS320F2407A to control the asynchronous motor for elevators. The TMS320F240 is a new generation of microcontroller designed specifically for motor control. It has a high-performance C2xLP core with a maximum computing power of 40MIPS. It adopts an improved Harvard architecture and a four-stage pipeline operation. The on-chip integrated event manager includes three independent bidirectional timers, each with a separate comparison register, which supports the generation of PWM output with programmable dead time. Two of the four capture ports can be directly connected to the quadrature encoding pulses from the photoelectric encoder. Two independent 10-bit 16-channel A/D converters can simultaneously and in parallel complete the conversion of two analog inputs. The on-chip integrated serial communication interface (SCI) and serial peripheral interface (SPI) can be used for communication with the host computer, peripherals and multiprocessors. These excellent features of the TMS320F240 provide an ideal solution for high-performance motor control [2]. 2.3 Signal detection module Since the controlled motor adopts a star connection, only the two-phase current needs to be detected ( ) [2]. Considering conversion speed and accuracy, the system uses Hall effect sensors to measure the stator currents i_a and i_b of the motor. i_a and i_b are converted into voltage signals, which are then fed into a level offset circuit to convert the bipolar current signal into a 0-3.3V unipolar level. This level is then sampled by the A/D converter ports ADCIN2 and ADCIN3 of the TMS320LF2407A, converting the analog signal into a digital signal for data processing. The detection circuit uses a two-stage operational amplifier LM358. In the speed sampling system, an incremental encoder with an accuracy of 1024 p/r is used to detect the rotor position. The two quadrature pulse signals output by the photoelectric encoder are differentially amplified and directly connected to QEP1 and QEP2 of the DSP. 3. System Software Implementation The main circuit of the system is relatively simple after adopting the intelligent power module. All control algorithms can be completed in real time in the TMS320LF2407A DSP. The software for the LF2407A DSP control section of this system is written in assembly language under the DSP integrated development environment CCS. The entire software mainly includes an initialization program and an underflow interrupt service subroutine. Its software structure is shown in Figures 5 and 6. The initialization program completes the initialization of DSP hardware and software variables and enables interrupts. The interrupt service program consists of multiple functional modules, including current and speed detection signal processing, speed and flux adjustment, flux estimation, coordinate transformation, and PWM signal generation. Each functional module executes in a certain order within a fixed time period, and the program is started by the underflow interrupt of T1CNT. [align=center] Figure 3 Initialization Program Flowchart Figure 4 Underflow Interrupt Service Subroutine Flowchart[/align] 3.1 PI Regulator Design PI regulation is one of the most commonly used controllers in motor control systems. The purpose of the regulator is to eliminate the deviation between the output and the input. Its digital implementation, after discretization, has the following algorithm: Where KP is the proportional gain, KI is the integral gain, and T is the sampling time. Its principle is shown in Figure 5. [align=center]Figure 5 Anti-integral saturation PI regulator[/align] 3.2 Optimized controller design The output of the optimized controller is as follows. Since it involves division, square root and other operations, in order to improve program efficiency, C and assembly mixed programming is adopted. The division and square root subroutines are written in assembly language. First, the optimal magnetic flux is obtained, and then the optimal excitation current is obtained according to the steady state. 3.3 Rotor flux position calculation The control performance of the vector control system is largely determined by the accuracy of the magnetic field orientation. The current speed model under the rotor flux coordinate system is used in the system to estimate the rotor flux position angle, so as to achieve the correct magnetic field orientation. The flux observation model equation is: where is the rotor time constant, Fs is the ratio of the rotor flux angular frequency to the rated angular frequency, ωn is the rated angular frequency, and n is the ratio of the actual rotor speed to the rated speed. 3.4 SVPWM module Each event manager of TMS320LF2407A has 3 full comparator units to output 6 channels of PWM waveforms with programmable dead time. When the components of the stator phase voltage vector and the number of sectors they belong to are known, the inverter can be controlled by generating a PWM control signal through the voltage space vector SVPWM technology. 4. Experimental Results and Analysis The experimental prototype was a 2.2kW vector control variable frequency drive elevator asynchronous motor speed control system. Steady-state operation experiments were conducted on it using an efficiency optimization control strategy. In this experiment, the motor ran under no-load, with an initial speed set at 1600 r/min, and after 1.4s of stable operation, it was set to 1400 r/min. Figures 6 and 7 show the experimental waveforms of the output line current and output line voltage, respectively. [align=center] Figure 6 Output Line Current Figure 7 Output Line Voltage[/align] From the experimental results in Figures 6 and 7, it can be seen that the output current is a good sinusoidal waveform, and the output voltage is a sine wave modulated by pulse width modulation, with the fundamental wave being the dominant component and harmonic components being relatively few. This proves the effectiveness and feasibility of the control method proposed in this paper. 5. Conclusion Based on the analysis of the mathematical model and flux linkage optimization algorithm for asynchronous motors considering iron losses, the vector control variable frequency speed regulation system composed of DSP and IPM as its core can effectively solve the real-time problem caused by the large amount of computation in actual vector control implementation. The control system has a simple, stable, and reliable hardware structure, and boasts advantages such as fast dynamic response and high control accuracy. It is an ideal vector control implementation scheme and can be widely applied in electrical drives using elevator motors as drive devices, thereby achieving high-precision speed control performance and providing power guarantees for elevator energy saving, fast lifting speed, accurate leveling, and good comfort. References [1] Kouki Matsuse, Taniguchi S, Yoshizumi T. A speed-sensorless vector control of induction motor operating at high efficiency taking core loss into account. IEEE Trans. on Ind. Appl, 2001 37(2): 548-557. [2] Wang Xiaoming, Wang Ling. DSP control of electric motors [M]. Beijing: Beijing University of Aeronautics and Astronautics Press, 2004. [3] Li Ying, Shi Weiguo. Research on operating efficiency and energy-saving control of variable frequency speed control motors [J]. Electrical Drive Automation, 1999, 21(1): 21-25. [4] Cui Naxin. Research on minimum loss fast response control of variable frequency drive asynchronous motors [D]. [Doctoral dissertation]. Shandong: School of Control Science and Engineering, Shandong University, 2005.