Variable Speed Drive Power Cell Rectified Voltage Control
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Solution Overview
Problem
Existing variable speed drive systems face challenges in accurately controlling output voltage to electrical devices due to variations in rectified voltages across power cells, leading to errors and requiring additional sensors for correction, which complicates diagnosis and maintenance.
Innovation Solution
A method is introduced to determine rectified voltages of power cells by activating and deactivating cells in a controlled manner, measuring output voltages, and storing these values to access each rectified voltage without additional sensors, allowing for precise control and adaptive duty cycle determination, enabling minimal correction and predictive maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If motor voltage measurements are used to compensate for rectified voltage errors, then output voltage control accuracy is improved, but device complexity increases due to additional sensors and corrector dynamics
Solution Approach 1:
The system uses the electrical device itself as a measurement tool by measuring the voltage it consumes during iterative activation of power cells. This self-service approach eliminates the need for separate sensors to measure rectified voltages, reducing device complexity while maintaining measurement accuracy for control purposes
Solution Approach 2:
The electrical device acts as an intermediary medium that enables indirect measurement of rectified voltages. By measuring the voltage across the electrical device terminals during controlled activation sequences, the system obtains rectified voltage information without direct sensing, simplifying the overall measurement system
2Reliability
If additional sensors are provided for power cell diagnosis, then diagnostic capability is improved, but device complexity and cost increase
Solution Approach 1:
The voltage measurement system serves multiple functions: it controls output voltage by determining rectified voltages and simultaneously provides diagnosis for all power cells. This multi-functionality eliminates the need for separate diagnostic sensors, reducing device complexity while improving reliability through comprehensive monitoring
Solution Approach 2:
The system diagnoses power cell status by measuring voltages across the electrical device during iterative activation. Each power cell's health is assessed through its contribution to the overall voltage measurement, enabling self-diagnosis without external diagnostic equipment
3Measurement precision
If iterative power cell activation is performed to determine rectified voltages, then measurement precision is improved, but productivity decreases due to repeated activation cycles
Solution Approach 1:
The system performs preliminary characterization of rectified voltages during iterative activation cycles. Once characterized, this information is stored and reused for subsequent control operations, eliminating the need for repeated iterative measurements and improving productivity while maintaining measurement precision
Solution Approach 2:
The iterative activation and measurement process is performed periodically rather than continuously. Rectified voltage values are determined at regular intervals and then used for control between updates, balancing measurement precision with productivity by minimizing the frequency of disruptive activation cycles
Data Source
AI summary
A method for controlling a variable speed drive comprising Ni low-voltage power cells connected in series for each phase among multiple phases, i being a phase index. The method comprises repeating P iterations comprising: activating at least one cell of one or more phases and deactivating the other power cells of the variable speed drive, wherein the at least one activated cell is selected on the basis of predefined activation controls depending on an iteration index; and receiving at least one output voltage of the variable speed drive across the terminals of the electrical device for at least one phase. The method further comprises, at the end of the P iterations, determining, from the measured output voltages, values of rectified voltage at the output of respective rectification stages of the power cells, and storing the rectified voltages obtained, which are respectively associated with the power cells.