Inverter Control for Real-Time Current Setpoints Under DC Bus Limits
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Solution Overview
Problem
Existing methods for controlling synchronous electrical machines, such as permanent magnet synchronous and synchronous reluctance machines, face challenges in achieving real-time optimal current setpoints and efficient use of DC bus voltage, leading to potential over- or under-utilization and suboptimal performance.
Innovation Solution
A method and control system that calculates optimal current setpoints using a recursive algorithm and feedback loop, considering torque and speed setpoints, and correcting operating variables to ensure robust use of DC bus voltage, applicable to all types of electrical machines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If MTPA method with offline data tables is used to determine current components, then the control accuracy is improved, but the real-time computational capability deteriorates and robustness to DC bus voltage limit is reduced
Solution Approach 1:
The patent implements a feedback mechanism where the actual DC bus voltage is continuously monitored and compared with the maximum threshold. Based on this feedback, the control method dynamically adjusts the current setpoints using a voltage error feedback loop, allowing the system to adapt to voltage constraints in real-time without relying solely on pre-computed offline data tables.
Solution Approach 2:
The control method transitions from static offline data tables to a dynamic real-time optimization approach. The current setpoints are continuously adjusted based on the actual operating conditions, particularly the DC bus voltage level, enabling the system to adapt dynamically to changing constraints while maintaining optimal performance.
2Productivity
If MTPA method with voltage error feedback is used, then the DC bus voltage utilization is improved, but the robustness to DC bus voltage limit deteriorates
Solution Approach 1:
The patent employs a robust feedback mechanism that continuously monitors the actual DC bus voltage and compares it with the maximum threshold. When the voltage limit is approached or exceeded, the system automatically adjusts the current setpoints through a voltage error feedback loop, ensuring the system remains reliable under varying voltage conditions rather than relying on fixed MTPA trajectories.
Solution Approach 2:
The control method dynamically changes the current setpoint parameters based on the actual DC bus voltage level. When voltage constraints are detected, the system modifies the current references in real-time through optimization algorithms, allowing the machine to operate reliably across different voltage conditions without being constrained by fixed MTPA curves.
3Productivity
If simplified real-time optimization algorithms with independent inductances are used, then the computational speed is improved, but the accuracy of current setpoints deteriorates
Solution Approach 1:
The patent incorporates the actual operating conditions, particularly the DC bus voltage level, as dynamic parameters in the optimization algorithm. Rather than using fixed independent inductance values, the system adjusts the optimization parameters in real-time based on the actual voltage constraints, maintaining both computational speed and accuracy by adapting the algorithm to current operating conditions.
Data Source
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AI summary
The present invention relates to a method and a system for controlling an inverter (OND) of an electric machine (MEL), which implement a control model (MOD) that calculates the optimal current setpoints as a function of the torque setpoint (Cem*) or the speed setpoint and other operating variables (VAF), including a corrected operating variable (VARcorr). The correction of this operating variable is implemented by means of a feedback loop controlling the control voltage of the electric machine.