Permanent magnet synchronous motor control using DC-Link current regulation

Using a shunt resistor sensor in the DC-Link of inverters, instead of three Hall-Effect sensors for measuring stator currents, results in cost saving and volume reduction in AC motor drives. This approach is followed in the current paper in permanent magnet synchronous (PMS) motor drives, without the common practice of stator current reconstruction. It is shown that motor line currents can be controlled indirectly by regulating the DC-Link current. To obtain sufficient information for motor control from the DC-Link, new voltage vectors are defined. Each new vector is synthesized by two original active vectors. Then a command is calculated for DC-Link current based on the motor set-points and maximum torque per Ampere (MTPA) strategy. Finally, a simple control law for voltage vector selection based on the DC-Link current error is presented. The proposed method shows similar performance to Direct Torque Control (DTC) method, while its implementation is easier due to the employment of a few simple equations. Therefore, the method is fitting for low cost but high performance applications that do not use powerful processors. The validity of the proposed method is verified by simulation of a 370-W PMS motor.