Method and system in connection with permanent magnet synchronous machines

1. A method in connection with a speed and position sensorless permanent magnet synchronous machine equipped with an output filter and driven by an inverter, wherein the method comprises the steps of

forming a speed-adaptive full-order observer based on the dynamic model of the combination of the permanent magnet synchronous machine (PMSM) and the output filter, the observer using inverter output current (i A ) as the measured feedback signal and an estimate for the electrical angular speed ({circumflex over (ω)} m ) of the motor and a speed correction term (ω ε ) for adaptation of the observer,

measuring the inverter output current (i A ),

estimating inverter output current (î A ) using the observer,

determining the estimate for the electrical angular speed ({circumflex over (ω)} m ) of the machine using the estimated inverter output current (î A ) and measured inverter output current (i A ) in an adaptation law,

injecting a voltage signal (u c ) into the inverter voltage reference (u A,ref 0 ) to obtain a modified voltage reference (u A,ref ) that is used to control of the inverter,

detecting an error signal (ε) from the measured inverter output current (i A ) originating from the injected voltage signal (u c ), and

calculating the speed correction term (ω ε ) used in the adaptation of the observer from the error signal (ε).

2. A method according to claim 1 , wherein the estimate for the electrical angular speed of the machine is determined using a PI controller algorithm where the error between the estimated inverter output current and the measured inverter output current is used as the error that is controlled to zero and the output of the controller provides the estimate for the angular speed of the machine.

3. A method according to claim 1 , wherein the speed correction term is calculated using a PI controller algorithm where the error signal is used as the error controlled to zero and the output of the controller provides the speed correction term.

4. A method according to claim 1 , wherein the speed adaptive observer has a correction term, which is based on the difference between the measured inverter output current and the estimated inverter output current, the estimated inverter output current being obtained from the observer.

5. A method according to claim 1 , wherein the speed correction term and the estimated rotor angular speed are used in the system matrix of the speed-adaptive observer.

6. A system in connection with a speed and position sensorless permanent magnet synchronous machine equipped with an output filter and driven by an inverter, wherein the system comprises

a speed-adaptive full-order observer based on the dynamic model of the combination of the permanent magnet synchronous machine (PMSM) and the output filter, the observer being adapted to use inverter output current (i A ) as the measured feedback signal and an estimate for the electrical angular speed ({circumflex over (ω)} m ) of the motor and a speed correction term (ω ε ) for adaptation of the observer,

means for measuring the inverter output current (i A ),

the observer being adapted to estimate inverter output current (î A ),

adaptation means adapted to determine the estimate for the electrical angular speed ({circumflex over (ω)} m ) of the machine using the estimated inverter output current (î A ) and measured inverter output current (i A ),

signal injection means adapted to inject a voltage signal (u c ) into the inverter voltage reference (u A,ref 0 ) to obtain a modified voltage reference (u A,ref ) that is used to control of the inverter,

detection means adapted to detect an error signal (ε) from the measured inverter output current (i A ) originating from the injected voltage signal (u c ), and

calculation means adapted to calculate the speed correction (ω ε ) term used in the adaptation of the observer from the error signal (ε).

7. A method according to claim 2 , wherein the speed correction term is calculated using a PI controller algorithm where the error signal is used as the error controlled to zero and the output of the controller provides the speed correction term.

8. A method according to claim 2 , wherein the speed adaptive observer has a correction term, which is based on the difference between the measured inverter output current and the estimated inverter output current, the estimated inverter output current being obtained from the observer.

9. A method according to claim 3 , wherein the speed adaptive observer has a correction term, which is based on the difference between the measured inverter output current and the estimated inverter output current, the estimated inverter output current being obtained from the observer.

10. A method according to claim 2 , wherein the speed correction term and the estimated rotor angular speed are used in the system matrix of the speed-adaptive observer.

11. A method according to claim 3 , wherein the speed correction term and the estimated rotor angular speed are used in the system matrix of the speed-adaptive observer.

12. A method according to claim 4 , wherein the speed correction term and the estimated rotor angular speed are used in the system matrix of the speed-adaptive observer.