System and method for an inverter for self-excitation of an induction machine

A method of controlling an inverter coupled to a generator, the method comprising:

• measuring an observed voltage across direct current voltage terminals;
• determining a voltage difference between the observed voltage and a reference DC bus voltage;
• generating, by a controller, a reference q-axis current command (Iqref) based on the voltage difference;
• measuring a q-axis current (Iqmeasured);
• determining a current difference between the measured q-axis command current and the reference q-axis current command (Iqref);
• outputting, by a current regulator, a q-axis voltage command (Vq) based on input of the current difference;
• determining a d-axis residual voltage (Vdresidual) in accordance with a following equation:
• V
• d
• residual
• =
• (
• m
• ⁢
• ⁢
• V
• D
• ⁢
• ⁢
• C
• measured
• )
• 2
• 3
• -
• V
• q
• 2
• ,
• where:
• m is a modulation index,
• VDCmeasured is the measured voltage of or between the direct current terminals, and
• Vq is the quadrature-axis voltage command;
• determining d-axis reference current (Idref) for the corresponding residual d-axis voltage (Vdresidual) based on a magnetizing curve or K-factor lookup table stored in a data storage device;
• determining, by a current regulator, the commanded d-axis voltage (Vd) based on a measured d-axis current (Idmeasured) and the determined d-axis reference current (Idref);
• and
• providing phase voltage commands (Va,Vb,Vc) based on inverse parks transform of the commanded voltages (Vd and Vq).

A system of controlling an inverter coupled to a generator, the system comprising:

• a voltage sensor for measuring an observed voltage across direct current voltage terminals;
• a voltage difference module for determining a voltage difference between the observed voltage and a reference DC bus voltage;
• a first current regulator outputting a q-axis voltage command (Vq) based on a current difference derived from the voltage difference;
• a second current regulator for determining a commanded d-axis voltage (Vd) based on a measured d-axis current (Idmeasured) and a determined d-axis reference current (Idref) derived from a mathematical relationship between d-axis residual voltage (Vdresidual), the observed voltage (VDCmeasured) and the commanded q-axis voltage (Vq) in which the d-axis residual voltage is proportional to a function of the observed voltage (VDCmeasured) and the commanded q-axis voltage (Vq);
• and
• an inverse Parks transformation module for providing phase voltage commands (Va,Vb,Vc) based on inverse Parks transform of the commanded voltages (Vd and Vq).

A system of controlling an inverter coupled to a generator, the system comprising:

• a voltage sensor for measuring an observed voltage across direct current voltage terminals;
• a voltage difference module for determining a voltage difference between the observed voltage and a reference DC bus voltage;
• a controller for generating a reference q-axis current command (Iqref) based on the voltage difference;
• a current sensor for measuring a q-axis current (Iqmeasured);
• a current difference module for determining a current difference between measured q-axis current and the reference q-axis current command (Iqref);
• a first current regulator for outputting a q-axis voltage command (Vq) based on input of the current difference;
• a data processor for determining a d-axis residual voltage (Vdresidual) in accordance with a following equation (to fully use of the DC bus and makes the self-excitation robust):
• V
• d
• residual
• =
• (
• m
• ⁢
• ⁢
• V
• D
• ⁢
• ⁢
• C
• measured
• )
• 2
• 3
• -
• V
• q
• 2
• ,
• where:
• Vdresidual is the residual d-axis current,
• m is the modulation index,
• VDCmeasured is the measured voltage of or between the direct current terminals, and
• Vq is the quadrature-axis voltage command;
• the data processor determining d-axis reference current (Idref) for a corresponding residual d-axis voltage (Vdresidual) based on a magnetizing curve or K-factor lookup table stored in a data storage device;
• a second current regulator for determining the commanded d-axis voltage (Vd) based on the measured d-axis current (Idmeasured) and the determined d-axis reference current (Idref);
• and
• an inverse Parks transformation module for providing phase voltage commands (Va,Vb,Vc) based on inverse parks transform of the commanded voltages (Vd and Vq).