High performance sensor-less V/f control of surface PMSM in voltage vector plane with ZVV injection and SMO-based position estimation method

In this work, a high performance sensor-less V/f control technique for surface permanent magnet synchronous motors is developed by realizing the control in voltage vector plane. To achieve this, the torque expression is derived in voltage vector plane. Thereafter, the equation is modified considering d-axis voltage as zero. It establishes a direct relationship of torque with q-axis voltage and amplitude of speed voltage. To maintain the d-axis voltage at zero, the stator voltage vector is positioned orthogonal to the rotor direct-axis. The technique requires rotor position and speed information. Here, a sensor-less hybrid position and speed estimation technique is developed by combining “Zero Voltage Vector (ZVV)” injection-based method and “Sliding Mode Observer (SMO )based method” for position and speed estimation throughout the entire speed zone. ZVV-based estimator is capable to estimate rotor position and speed during zero and low speed region. However, in medium and high speed it’s performance degrades. Hence, SMO-based estimation technique is used in medium and high speed zone. A speed-dependent weighted sum-based transition method is used for smooth transition from ZVV to SMO-based method. The dynamic performance of the developed drive for its entire speed range is better than existing V/f drive and comparable to sensor-less vector control drive. Extensive simulation and experimental study is carried to ensure stable operation and high dynamic performance in all operating conditions.