• Casper Vadstrup
4. semester, Energiteknik, Kandidat (Kandidatuddannelse)
Adjustable Speed Drives (ASD) with a Permanent Magnet Synchronous Machines (PMSM) are used extensively in the industry for various applications due to its high efficiency. PMSM are fed by pulse width modulated inverter drives. New power devices using wide band gap materials offers fast turn-on and turn-off times, and allows use of high switching frequency. However, these properties will generate high dV/dt, which requires filters to reduce due to losses, EMI and bearing current. These filters have normally been big and bulky, but the high switching frequency permits use of small filters with a high resonant frequency. These filters have potential to increase the system efficiency because the PMSM are fed with filtered voltages. The filter may influence the control of the PMSM, and it is therefore necessary to analyse the motor control stability when a filter is inserted.

An LC-filter design procedure has been proposed in this thesis to sufficiently reduce the dV/dt. The inductance and capacitance can be calculated based on the desired gain ($K$) at the switching frequency, and the current amplitude ($I_L$) of the frequency component at the switching frequency. The equations in the design procedure are based on transfer function of filter in the frequency domain. Simulations of the ASD with an LC-filter was compared to the equations and shows good match.

To realize control the PMSM a Field Oriented Control (FOC) system was designed. The parameters of the controller was calculated based on desired bandwidth of the current and the speed control loop. Position information is necessary in FOC, and a speed and position estimator was designed.

The LC-filter may influence the stability of FOC controlled ASD. A stability analysis has then been carried out. A range of LC-filter configurations have been simulated to find the upper and lower boundary of the current control bandwidth. It was shown that for designing an LC-filter with little impact on the control stability, the $K$ value should be 0.3 or lower for FOC with sensor and 0.2 or lower for sensorless FOC. Values of the current $I_L$ above 2 A ensured stability, but can be lowered if $K$ is lowered accordingly.
SpecialiseringsretningEffektelektronik og elektriske drivsystemer
Udgivelsesdato4 jun. 2013
Antal sider77
Udgivende institutionAalborg University
ID: 77234987