Synchronous Machine Control with Non-Sinusoidal Current Profiles
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Solution Overview
Problem
Conventional closed-loop control systems for synchronous machines face challenges in handling non-sinusoidal currents, leading to torque variations and noise generation, especially at low rotational speeds, due to the limitations of transformation equations based on sinusoidal signal curves.
Innovation Solution
The method involves adapting the transformation between stator-oriented and field-oriented coordinate systems to convert desired non-sinusoidal controlled variables into pure zero-frequency variables, allowing for the direct calculation of non-sinusoidal manipulated variables without requiring high-frequency modulation, thus maintaining the simplicity and efficiency of conventional field-oriented control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If sinusoidal current control is used in conventional field-oriented control systems, then the control structure remains simple and efficient, but torque variations and noise generation occur especially at low rotational speeds
Solution Approach 1:
The patent changes the functional form of the manipulated variables from sinusoidal to non-sinusoidal curves in the stator-oriented coordinate system. This parameter change in the current waveform shape eliminates torque variations and noise while maintaining simple field-oriented control structure, directly resolving the technical contradiction.
2Object-generated harmful factors
If non-sinusoidal currents are fed into the synchronous machine, then torque constancy and low-noise operation are achieved, but complex modulation of alternating components is required
Solution Approach 1:
The patent defines non-sinusoidal manipulated variable curves (i_d,a0(φ_el), i_q,a0(φ_el)) as functions of rotor angle that directly produce constant torque. By changing the current waveform parameters and using adapted transformation equations, the system achieves torque constancy without requiring complex high-frequency modulation, thus resolving the contradiction between performance and complexity.
Solution Approach 2:
The patent pre-defines the non-sinusoidal current curves as functions of rotor angle before control execution. These predetermined current profiles are stored and applied based on rotor position, eliminating the need for real-time complex modulation calculations and simplifying the controller dynamics.
3Productivity
If sinusoidal transformation equations are used between coordinate systems, then the transformation is simple and efficient, but non-sinusoidal controlled variables cannot be properly handled
Solution Approach 1:
The patent modifies the transformation equations between stator-oriented and field-oriented coordinate systems to accommodate non-sinusoidal variables. The adapted transformation uses rotor-angle-dependent functions instead of pure sinusoidal relationships, maintaining computational efficiency while enabling proper handling of non-sinusoidal controlled variables.
Solution Approach 2:
The transformation equations are made dynamic by introducing rotor angle dependence. The transformation matrices and equations adapt their parameters based on the instantaneous rotor position, allowing efficient transformation of non-sinusoidal variables while maintaining the simplicity and speed of field-oriented control.
Data Source
AI summary
The present invention provides control of a synchronous machine with non-sinusoidal current-voltage profiles. The synchronous machine is controlled in a field-oriented coordinate system. In this case, the transformation between field-oriented coordinate system and stator-oriented coordinate system is effected by specific, adapted transformations which take account of the non-sinusoidal signal profiles during the driving of the synchronous machine, such that the latter correspond to current-voltage profiles progressing in a constant fashion in the field-oriented coordinate system. What is achieved thereby is that the non-sinusoidal current-voltage profiles need not be taken into account in any way in the design of the control system in the field-oriented coordinate system.