Abstract : This paper presents some important simulation results and reviews the new sensorless vector control inverter technology for asynchronous motor proposed in reference [1]. Keywords : Sensorless vector control AC drive Introduction Reference [2 ] introduced the stator flux observation method of reference [4] based on the self-correction of stator side resistance through online stator flux closed loop proposed in reference [3] and combined it with the stator flux orientation vector control inverter speed regulation, so that the motor stator flux value is kept at a given value and is not affected by the change of motor stator side resistance and rotor time constant, achieving significant results [5]; it can operate without a speed sensor, and can obtain a high starting torque and a small starting current, thus greatly reducing the current capacity of the inverter and significantly reducing the product cost. Reference [1] further added important links such as speed closed loop, speed estimation, slip calculation and commonly used torque current limiting on the basis of Reference [2], which greatly broadened the application function, and thus proposed a new type of high-performance sensorless stator flux orientation vector control variable frequency speed controller for the first time. The simulation results are introduced below. 2 Simulation results The following are some important simulation results. In the simulation curves of Figures 1-4: Iq* is the torque current given value of the speed closed loop output; Iq is the actual value of the motor torque current; Il is the load torque converted into current value; Figure 1 Il=12A, K=33.3 K represents the ratio of the load flywheel inertia on the motor shaft to the set flywheel inertia. In the simulation: the difference between Iq* and Iq is obtained by integrating the speed estimate through the integral link related to the set flywheel inertia. The set speed value and the speed estimate form the speed closed loop. The difference between Iq and Il is obtained by integrating the speed estimate through the integral link related to the load wheel inertia on the motor shaft. 3. Simulation Results Review As shown in Figures 1-4: (1) Except for a slight overshoot in the first waveform during startup, the actual motor speed follows the set value, i.e., the given speed, very well in all other cases. [align=center] Figure 2 Il = 0.3A, K = 33.3 Figure 3 Il = 12A, K = 0.83 Figure 4 Il = 0.3A, K = 0.83[/align] (2) Except for the transition zone of speed increase and decrease, in other steady speed zones, Iq*, Iq, and Il are all equal. (3) When the adjustment parameters of the speed closed loop and the set flywheel inertia remain unchanged, the motor can work normally when Il changes by 40 times (= l2 / 0.3) and the flywheel inertia on the motor shaft changes by 40 times (= 33.3 / 0.83). 4. Conclusion In variable frequency speed control of asynchronous motors, the most important issue is how to maintain the motor flux linkage at a given value without being affected by changes in motor operating temperature, specifically, without being affected by the temperature variations of stator resistance R1 and rotor time constant T2. However, achieving this requirement has remained difficult for decades. For example, the rotor flux linkage observation formula in the sensorless rotor flux linkage orientation vector control method disclosed in US Patent No. US2003/0015988A1 (publication date: January 23, 2003) includes R1 and T2, but no corresponding measures are provided to eliminate the influence of changes in R1 and T2. For example, in the stator flux observer formula of sensorless direct torque control (DTC), R1 is also included, but there is a lack of corresponding measures to eliminate the influence of R1 changes; in terms of establishing the motor terminal voltage, the vector voltage drop factor on R1 that should be included at low speed is not taken into account; in addition, it is difficult to combine a limited number of voltage space vectors and simultaneously meet the requirements of flux closed loop and torque closed loop, resulting in frequent losses and torque pulsation; all of these factors lead to a decrease in performance in the low-speed range, including starting. In reference [2], R1 is the object of stator flux closed loop self-correction to achieve the purpose of keeping the motor stator flux value at a given value, and even if T2 changes over a large range, it will not affect the above self-correction process, thus eliminating the influence of motor operating temperature changes, and solving the long-standing problem for the first time. The basic variable Z of the stator flux observer formula plays a key role. The problem left by the new sensorless asynchronous motor vector control variable frequency speed controller is that the speed accuracy at low speed is not high; the research on the improvement of this problem has achieved results, and its contents will be disclosed in the form of patents. The new sensorless asynchronous motor vector control variable frequency speed controller has near closed-loop performance, high starting torque, wide speed range, and small inverter current capacity, resulting in low product cost. In addition to being widely used in low-voltage motors, if it is combined with high-voltage variable frequency speed controllers, the two will complement each other. References [1] Lu Ji. Sensorless asynchronous motor vector control variable frequency speed regulation method. Patent No.: 02l14389.7, Publication Date: March 17, 2004. [2] Lu Ji. Sensorless variable frequency speed controller. Patent No.: ZL02223487. Authorization Date: May 7, 2003. [3] Lu Ji. A stator flux corrector for variable frequency speed control of asynchronous motor. Patent No.: ZL00225853.6, Authorization Date: September 19, 2001. [4] Lu Ji. Observation method for parameters containing basic variables in variable frequency speed control of asynchronous motor. Patent No.: 0l106851.5, Publication Date: September 4, 2002. [5] Lu Ji. Online self-correction technology for stator resistance in variable frequency speed control of high performance vector control asynchronous motor. Variable Frequency World, 2004, (6). About the author: Professor Lu Ji, a senior engineer, once served as a professional consultant for the Electrical Bureau of the Ministry of Machinery Industry and worked in variable frequency speed control at BBC (now renamed ABB) in Switzerland for one year.