Inverter-Fed Polyphase Machine Control via Lookup Table Optimization
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Solution Overview
Problem
Existing systems for operating inverter-fed electrical induction machines are inefficient in terms of energy usage, as they do not effectively minimize power losses during steady-state operation.
Innovation Solution
The system determines a stator voltage space vector using detected motor current and voltage values, which are transformed into a rotor flux-oriented coordinate system to optimize energy usage by selecting operating points that minimize power losses, with the help of an observer and transformation elements, and utilizes controllers to manage torque and speed setpoints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional control methods are used for inverter-fed electrical induction machines, then the system operates with standard control quality, but energy consumption is high due to ineffective minimization of power losses
Solution Approach 1:
The system pre-calculates and stores optimal voltage space vectors in a lookup table based on torque and speed values before operation. During runtime, the control unit simply retrieves pre-computed values from the table based on current torque and speed demands, eliminating the need for complex real-time optimization calculations while achieving minimum power loss operation
Solution Approach 2:
The patent introduces an intermediate coordinate transformation system that converts voltage space vectors from the stationary coordinate system to the rotor flux-oriented coordinate system. This intermediary transformation enables precise control of power losses by decoupling the control of torque and flux components, allowing the system to minimize losses while maintaining required torque and speed
2Loss of energy
If the system determines operating points to minimize power losses, then energy efficiency improves, but the complexity of determining optimal voltage space vectors increases
Solution Approach 1:
The system pre-calculates and stores optimal voltage space vectors in a lookup table based on torque and speed values before operation. During runtime, the control unit simply retrieves pre-computed values from the table based on current torque and speed demands, eliminating the need for complex real-time optimization calculations while achieving minimum power loss operation
Solution Approach 2:
The patent creates a simplified model of the complex power loss minimization problem by storing pre-computed optimal voltage space vectors in a lookup table. Instead of solving the full optimization problem in real-time, the system uses this tabulated copy of optimal solutions, which can be retrieved instantly without complex calculations
3Productivity
If rapid determination of operating points is implemented, then control response speed increases, but precision in minimizing power losses may be compromised
Solution Approach 1:
The system pre-calculates and stores optimal voltage space vectors in a lookup table based on torque and speed values before operation. During runtime, the control unit simply retrieves pre-computed values from the table based on current torque and speed demands, eliminating the need for complex real-time optimization calculations while achieving minimum power loss operation
Solution Approach 2:
The patent transforms the continuous optimization problem into a discrete parameter selection problem by using a lookup table with predefined torque and speed values. The system changes from solving continuous equations to selecting from discrete pre-computed parameters, enabling rapid determination while maintaining accuracy through fine discretization of the parameter space
Data Source
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AI summary
A system for operating an inverter-fed polyphase electric machine, wherein the motor current is detected and, from this, a stator current phasor is determined, wherein the stator voltage phasor is determined from at least one detected voltage value, in particular an intermediate-circuit voltage value, in particular and possibly from a pulse width modulation signal, in particular pulse width modulation component, output by the inverter, wherein the stator current phasor and the stator voltage phasor are supplied to an observer, which, from this, firstly determines a reference angle and secondly a rotation speed actual value, which is supplied to a determination means, which, taking into consideration the reference angle, determines a voltage phasor which is transformed by a transformation element into another coordinate system, in particular into a rotor flux-oriented coordinate system, and this transformed voltage phasor is then made available to the inverter as manipulated variable.