Current Source Inverter Drive System with Equivalent DC-Machine Control Characteristics

Current source inverters (CSIs) present several advantages over voltage source inverters (VSIs) in drive system applications, particularly when supplying motor windings. CSIs inherently feature integrated output capacitors that deliver smooth voltages to the motor windings, effectively eliminating issues such as interturn overvoltages, insulation degradation due to large <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{d}v/\mathrm{d}t$</tex>, bearing currents, and electromagnetic interference. With the recent advancements in monolithic bidirectional switches, CSIs have become an increasingly attractive option for drive systems. However, CSIs are more complex to modulate and control compared to VSIs, which poses a challenge to their widespread adoption in the industry, where engineers are typically more familiar with VSI PWM techniques. To address this, we propose the Equivalent DC Machine (E-DCM) concept. In this concept, the CSI operates in open loop with a fixed modulation index, relieving the user of any need to manage the CSI. The user can directly control the PMSM torque through the DC link current. As a result, the E-DCM concept enables the CSI-supplied PMSM to behave like a traditional DC machine, offering the simplicity of control without the issues associated with commutation and maintenance. To validate the proposed E-DCM concept, we provide transient time-domain simulations demonstrating its performance as it accelerates from zero to nominal speed.