Synchronous Motor Startup Control for Rotor Oscillation Damping
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Solution Overview
Problem
Synchronous motor startup from standstill often results in rotor speed oscillations due to weak natural damping, and existing methods fail to minimize these oscillations and reduce startup time effectively.
Innovation Solution
A method involving a controller that applies reference stator voltages determined from a reference current vector and rotor speed, with measured stator currents used to estimate rotor flux and position, and a PI controller to adjust the current vector, reducing speed and position errors to minimize oscillations and shorten startup time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a rotating stator current vector is applied to start the synchronous motor, then the rotor is forced to follow the stator current vector, but this results in speed oscillations of the rotor due to very weak natural damping
Solution Approach 1:
The patent implements a feedback mechanism by continuously detecting the actual rotor speed and comparing it with the reference speed to generate a speed error signal. This error signal is then fed into a PI controller that adjusts the stator current vector to minimize the speed error, thereby damping oscillations and stabilizing rotor speed during startup.
Solution Approach 2:
The patent dynamically changes the parameters of the stator current vector based on the detected rotor speed and position. By adjusting the amplitude and phase of the stator current components in the rotating coordinate system according to the speed error and position error, the system optimizes torque production while minimizing oscillations during the startup transient.
2Stability of the object's composition
If additional damping is achieved by modifying the stator current vector, then rotor speed oscillations are reduced, but the startup procedure becomes longer
Solution Approach 1:
The patent employs dynamic control strategies where the stator current vector is continuously adjusted based on real-time rotor position and speed detection. The PI controller dynamically modifies the current components to provide optimal damping at each instant of the startup process, achieving a balance between oscillation reduction and startup speed rather than using fixed conservative parameters.
Solution Approach 2:
The patent replaces mechanical damping mechanisms with an electrical control solution. Instead of adding physical damping elements to the motor, the system uses electronic modification of the stator current vector through PI control to achieve the desired damping effect, thereby avoiding the time penalties associated with mechanical damping approaches.
3Productivity
If the startup procedure is made as short as possible, then productivity is improved, but rotor speed oscillations increase due to insufficient damping
Solution Approach 1:
The real-time feedback from rotor position and speed detection enables the controller to apply precisely timed and sized damping torques throughout the startup process. This feedback mechanism allows for aggressive yet controlled acceleration profiles that minimize startup time while preventing excessive oscillations through continuous correction.
Solution Approach 2:
The patent applies preliminary damping action by detecting rotor position and pre-calculating the appropriate stator current vector components before the rotor reaches critical speed ranges. This proactive control approach prepares the damping torque in advance, allowing for faster startup while maintaining stability during the transient phases.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method significantly reduces rotor speed oscillations and shortens startup time to approximately 1 second, ensuring a smooth transition to normal operation mode without sensors or encoders.
Implementation Method 1
A rotor position and speed of a synchronous motor, such as a permanent-magnet synchronous motor (PMSM), may be detected without using any sensors or encoders. For starting a synchronous motor from standstill, a rotating stator current vector may be applied, which creates electromagnetic torque forcing the rotor to follow the stator current vector.
Implementation Method 2
measuring stator currents used to estimate rotor flux and position, and a PI controller to adjust the current vector
Data Source
Figure 1
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Figure 3~4
AI summary
The invention relates to a method (600) for starting a synchronous motor (102). The synchronous motor (102) comprises a rotor (112) for creating a first magnetic field and a stator (108) with stator windings (110) connected to an electrical energy converter (104) for converting a supply voltage (Vcc) into a stator voltage (Vsx, Vsy, Vsz) to be applied to the stator windings (110) to create a rotating second magnetic field interacting with the first magnetic field. The method (600) comprises the following steps: applying (610) reference stator voltages ([ Vsx* Vsy* Vsz*]) to the stator windings (110), wherein the reference stator voltages ([ Vsx* Vsy* Vsz*]) are determined from a reference current vector ([ isd** isq**]) and a reference rotor speed ( ωr**); measuring (620) stator currents (isx, isy) in the stator windings (110); calculating (630) an estimated rotor speed (ω̃r) and an estimated rotor position (θ̃r) of the rotor (112) from the applied stator voltages (Vsx, Vsy, Vsz) and the measured stator currents (isx, isy); calculating (640) a speed error (ωe) by subtracting the estimated rotor speed (ω̃r) from the reference rotor speed ( ωr**); determining (650) a reference torque producing current component ( isq**) from the speed error (ωe) and modifying the reference current vector isd**isq** with the reference torque producing current component ( isq**); calculating (660) a position error (θe) by subtracting the estimated rotor position (θ̃r) from a reference rotor position ( θr*), wherein the reference rotor position ( θr*) is determined from the reference rotor speed ( ωr**) and a reference rotor speed correction (ωc), wherein the reference rotor speed correction (ωc) increases and decreases with the position error (θe); correcting (670) the reference current vector isd**isq** by transforming the reference current vector isd**isq** into a corrected reference current vector isd*isq* by the position error (θe), wherein a rotating coordinate system (dq) of the corrected reference current vector isd*isq* is aligned with the estimated rotor position (θ̃r); determining (680) switching signals (s1, s2, s3) for the electrical energy converter (104) from the reference stator voltages Vsx*Vsy*Vsz* and applying the switching signals (s1, s2, s3) to the electrical energy converter (104).