Abb Oy

Abb Industry Oy

Markku Niemel&auml;

A method of correcting the stator flux estimate midpoint in alternating-current systems, the method comprising the step of determining a stator flux estimate (&PSgr;s, est&quest;). The method is characterized in steps of forming the sum of the squares of the rectangular components (&PSgr;sx, est&quest;, &PSgr;sy, est&quest;) of the stator flux estimate to obtain a reference variable (k), low-pass filtering the reference variable (k) in order to obtain a low-frequency component (k ) of reference variable, subtracting the low-frequency component (k ) from the reference variable (k) in order to obtain a difference variable (e), determining rectangular correction term components (&PSgr;sx, corr&quest;, &PSgr;sy, corr&quest;) of the stator flux estimate (&PSgr;s, est&quest;) by multiplying the difference variable (e) by the rectangular components (&PSgr;sx, est&quest;, &PSgr;sy, est&quest;) of the stator flux and a correction coefficient (K ), and forming a midpoint-corrected stator flux estimate (&PSgr;s, fin&quest;) by adding the correction term components to the components of the stator flux estimate.

Stator flux estimate midpoint correction

A method for controlling an electrical machine while it is connected to an inverter comprising phase-specific switching components generating an output voltage, an optimum switching table arranged to select a switching combination for the switching components on the basis of the stator flux and torque of the electrical machine, the method comprising steps of defining the stator current vector (i ) of the electrical machine, and determining the rotation speed of the electrical machine. The method also comprises the step of defining a switching combination for the switching components on the basis of the stator current vector (i ) and stator current reference vector (&psgr; ) of the electrical machine when the determined rotation speed is lower than a predefined limit.

Method for controlling an electrical machine and an inverter

The invention relates to a method of correcting the flux midpoint in flux-controlled alternating current systems, the method comprising the steps of determining a stator flux estimate (&psgr; ) and determining the magnitude of stator current (i ). The method is characterized by the steps of forming the scalar product between the stator flux estimate (&psgr; ) and the stator current (i ) in order to obtain a reference variable (k), low-pass filtering the reference variable (k) in order to obtain a low-frequency component (k ) of the reference variable (k), subtracting the low-frequency component (k ) from the reference variable (k) in order to obtain a difference variable (e), determining correction term components (&psgr; , &psgr; ) of the staror flux estimate (&psgr; ) by multiplying the difference variable (e) by the components (&psgr; , &psgr; ) of the stator flux and correction coeficient (K ), and forming a stator flux (&psgr; ) with a corrected midpooint on the basis of the components (&psgr; , &psgr; ) of the stator flux estimate and correction term components (&psgr; , &psgr; ).

Growing community of inventors

Lappeenranta, Finland

Markku Niemelä

Growing community of inventors

Lappeenranta, Finland

Markku Niemel&auml;

Markku Niemelä