Research On Pmsm Rotor Position Estimation Method Based On Zero Voltage Vector Current Derivative

In modern high performance electrical drive systems,Permanent Magnet Synchronous Motors are becoming the dominating control parts.This is due to the prominent advantages in dynamic performance,power density and efficiency of PMSMs.Besides,the vector control scheme is widely applied in control systems,because the aforementioned features of PMSMs can be made good use in a largest extent.In PMSM closed-loop control system,in order to attain a relatively higher dynamic performance,the rotor position is the most important as it can affect the regulation of rotor speed and stator current.The installation of rotor position resolver or encoder not only increases costs but also decreases the stability of the system.Therefore,the research in sensorless control of PMSM is imperative for improving the reliability of the control system and reducing additional cost.Firstly,the current research status of sensorless control of PMSMs is introduced in this dissertation,especially in low-speed and zero-speed region.Due to the low back EMF of PMSMs,sensorless control of PMSMs in low speeds is the most difficult parts and currently is the research focus.In this dissertation,the mathematical equations of PMSMs are established in order to analyze the operational status of PMSMs in different speed regions,and thus as the basis of researching for the sensorless control methods of PMSMs in low speeds.Secondly,a sensorless control method,which is based on current derivatives both in effective voltage vector and zero voltage vector regions,is analyzed in threephase axis.In low-speed and zero-speed regions,the effective voltage duration is very short,and the zero voltage vector duration will increase dramatically.Therefore,mathematical equations of motors in zero voltage vector period can be constructed.This dissertation proposes a zero-voltage vector based rotor position estimation scheme.In the proposed scheme,stator currents are only required to be sampled in zero-voltage vector every period and the current derivatives can be calculated without using any excessive current derivative detector.In order to improve the accuracy of estimated rotor position,the switching properties of IGBT and current in zero-voltage vector are researched and analyzed.A novel current sampling method which uses two phases current for Clarke and Park calculation is proposed.Finally,in order to verify the effectiveness of the proposed position estimation method,a 1.0k W PMSM drive testing bed is constructed.The experimental results show that the rotor position can be extracted in different load circumstance.Compared to traditional low speeds control methods,the proposed method has better performance in instantaneous response,especially the step load response in zero-speed condition.