A power conversion system, comprising: an inverter comprising a DC input, an AC output, and a plurality of switching devices (S1-S6) coupled between the DC input and the AC output and operative according to inverter switching control signals to convert DC electrical power received at the DC input to provide AC electrical output power at the AC output to drive a motor through an intervening filter; and a controller configured to: compute motor current feedback values ( i a.m, i b.m, i c.m) for a current control cycle according to inverter output current values ( i u, i v, i w), capacitance values representing capacitances of filter capacitors ( c f) of the filter, filter output voltage values ( V ab, V bc, V ca) representing output voltages of the filter, and a speed reference or feedback value (Spfbk) of a previous control cycle, wherein the motor current feedback values ( i a.m, i b.m, i c.m) are computed as a difference between the inverter output current values ( i u, i v, i w) and computed filter capacitor current values ( i a.cf, i b.cf, i c.cf), compute a speed feedback value (Spfbk) for the current control cycle according to the motor current feedback values ( i a.m, i b.m, i c.m) and the filter output voltage values ( V ab, V bc, V ca), and control the inverter to regulate the rotational speed of the motor at least partially according to the speed feedback value (Spfbk) using vector control. an inverter comprising a DC input, an AC output, and a plurality of switching devices (S1-S6) coupled between the DC input and the AC output and operative according to inverter switching control signals to convert DC electrical power received at the DC input to provide AC electrical output power at the AC output to drive a motor through an intervening filter; and a controller configured to: compute motor current feedback values ( i a.m, i b.m, i c.m) for a current control cycle according to inverter output current values ( i u, i v, i w), capacitance values representing capacitances of filter capacitors ( c f) of the filter, filter output voltage values ( V ab, V bc, V ca) representing output voltages of the filter, and a speed reference or feedback value (Spfbk) of a previous control cycle, wherein the motor current feedback values ( i a.m, i b.m, i c.m) are computed as a difference between the inverter output current values ( i u, i v, i w) and computed filter capacitor current values ( i a.cf, i b.cf, i c.cf), compute a speed feedback value (Spfbk) for the current control cycle according to the motor current feedback values ( i a.m, i b.m, i c.m) and the filter output voltage values ( V ab, V bc, V ca), and control the inverter to regulate the rotational speed of the motor at least partially according to the speed feedback value (Spfbk) using vector control. compute motor current feedback values ( i a.m, i b.m, i c.m) for a current control cycle according to inverter output current values ( i u, i v, i w), capacitance values representing capacitances of filter capacitors ( c f) of the filter, filter output voltage values ( V ab, V bc, V ca) representing output voltages of the filter, and a speed reference or feedback value (Spfbk) of a previous control cycle, wherein the motor current feedback values ( i a.m, i b.m, i c.m) are computed as a difference between the inverter output current values ( i u, i v, i w) and computed filter capacitor current values ( i a.cf, i b.cf, i c.cf), compute a speed feedback value (Spfbk) for the current control cycle according to the motor current feedback values ( i a.m, i b.m, i c.m) and the filter output voltage values ( V ab, V bc, V ca), and control the inverter to regulate the rotational speed of the motor at least partially according to the speed feedback value (Spfbk) using vector control.