Externally Excited Synchronous Motor Setpoints Under Power Limits
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Solution Overview
Problem
Existing methods for operating separately excited synchronous motors (FESM) are not optimal, particularly in real-time conditions, and do not effectively minimize losses across all operating conditions, often requiring extensive offline preparation and being inflexible to changes in machine parameters.
Innovation Solution
An operating method that determines a current vector through real-time optimization, considering constraints on motor current, excitation current, and motor voltage, using a decision tree to efficiently solve optimization problems, ensuring minimal copper losses and real-time capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If existing methods for operating FESM are used, then the motor can operate with basic control, but losses are not minimized and real-time optimization is not achieved
Solution Approach 1:
The patent pre-calculates and stores optimal current vectors in lookup tables before operation. During real-time control, the controller simply retrieves pre-computed values based on operating conditions (torque demand and speed), avoiding complex real-time optimization calculations while achieving minimal losses.
Solution Approach 2:
The patent introduces lookup tables as an intermediary between the control system and the motor. These tables store pre-computed optimal current vectors that mediate between the control inputs (torque demand, speed) and the motor actuation, enabling real-time optimal control without complex real-time calculations.
2Productivity
If real-time optimization is implemented, then minimal losses are achieved, but extensive calculations are required that may not be computable in real-time
Solution Approach 1:
The patent performs the computationally intensive optimization calculations offline before operation, storing results in lookup tables. During real-time operation, only simple table lookups are required, achieving real-time control capability without requiring extensive real-time computational resources.
3Ease of operation
If offline-optimized lookup tables are used, then real-time operation is enabled, but the solution is inflexible to changes in machine parameters
Solution Approach 1:
The patent makes the lookup tables dynamic by allowing them to be regenerated when machine parameters change. The system detects parameter changes and automatically updates the lookup tables with new pre-computed optimal current vectors, maintaining both real-time operation capability and adaptability to parameter changes.
Solution Approach 2:
The patent enables the system to adapt to parameter changes by regenerating lookup tables with updated machine parameters. When parameters such as resistance or inductance change, the optimization is re-performed with new parameters and the lookup tables are updated, allowing the system to maintain optimality under varying conditions.
4Loss of energy
If current components are determined independently, then the control structure is simple, but the solution is suboptimal and does not minimize losses effectively
Solution Approach 1:
The patent merges the determination of field-generating and torque-generating current components into a unified optimization problem. Instead of determining current components independently through separate controllers, the system solves a single optimization problem that simultaneously determines all current components to minimize total copper losses while meeting torque and voltage constraints.
Data Source
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AI summary
A setpoint value determining unit (10) checks whether a requested power (P) of an externally excited synchronous motor (1), the power being given by the product of an instantaneous rotation speed (n) and a setpoint torque (M*) to be applied, exceeds a maximum value (Pmax) for the power (P). In one case, the setpoint value determining unit (10) addresses a first optimization problem (O1) for a current vector (i) and solves it in real time, and in the other case addresses a second optimization problem (O2). In order to solve the first optimization problem (O1), the setpoint value determining unit (10) determines a current vector (i), which comprises the field-forming component (Id) and the torque-forming component (Iq) of the motor current (I) and comprises the field current (Ie), in such a way that the setpoint torque (M*) is reached and the losses (V) of the synchronous motor (1) are minimized. In the other case, the setpoint value determining unit (10) determines the current vector (i) in such a way that the resulting actual torque (M) is maximized. In all cases, the setpoint value determining unit (10) takes into account the boundary conditions according to which the magnitude of the motor current (I) reaches at most the maximum value (Imax) for the motor current (I), the magnitude of the field current (Ie) reaches at most the maximum value (Iemax) for the field current (Ie) and the magnitude of the motor voltage (U) reaches at most the maximum value (Umax) for the motor voltage (U). The setpoint value determining unit (10) prespecifies the determined current vector (i), as setpoint values, to a power control device (9), which drives a converter device (8) in a corresponding manner.