Variable Frequency Drive Thermal Modeling for Coolant Flow Estimation
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Solution Overview
Problem
Existing variable frequency drives (VFDs) face challenges in accurately determining and managing transient temperature behavior and coolant flow rates due to the impracticality of direct measurements and the inaccuracy of methods like differential pressure sensors, especially in complex systems with multiple power cells and non-uniform airflow.
Innovation Solution
The implementation of a response surface methodology using computational fluid dynamics simulations and time constants to create a multi-dimensional lookup table that correlates power input, coolant flow rate, and temperature, allowing for accurate estimation of coolant flow rates and transient temperature behavior without direct measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If differential pressure sensors are used to measure coolant flow rate, then flow rate measurement is achieved, but measurement precision deteriorates due to non-uniform airflow and complex system geometry
Solution Approach 1:
The patent replaces mechanical differential pressure sensors with a computational model based on electrical measurements. The control system uses measured electrical parameters (voltage, current, power) and stored time constants to calculate coolant flow rate through computational fluid dynamics correlations, eliminating the need for physical pressure sensors and their associated measurement errors in complex geometries.
Solution Approach 2:
The patent introduces time constants as intermediary parameters that link electrical measurements to thermal behavior. These time constants, stored in the control system, serve as mediators between the electrical domain (power input measurements) and the thermal-fluid domain (coolant flow rate and temperature calculations), enabling accurate indirect measurement without direct physical sensing of flow or temperature.
2Measurement precision
If direct temperature measurement is implemented in multiple power cells, then temperature monitoring is achieved, but device complexity increases due to multiple sensors and non-uniform airflow patterns
Solution Approach 1:
The patent replaces physical temperature sensors with a computational thermal model. The control system calculates transient temperature behavior in each power cell by processing electrical measurements (power input, current) through stored time constants and thermal correlations, eliminating the need for physical temperature sensors in each cell and reducing system complexity while maintaining measurement precision.
Solution Approach 2:
The patent divides the thermal modeling into separate segments for each power cell, using individual time constants for each cell. This segmentation allows the system to account for non-uniform airflow patterns and different thermal characteristics of each cell independently, enabling accurate temperature determination without requiring physical sensors in each location.
3Measurement precision
If computational fluid dynamics simulations are performed in real-time, then accurate coolant flow rate determination is achieved, but processing time increases
Solution Approach 1:
The patent performs comprehensive computational fluid dynamics simulations and thermal modeling in advance, storing the results as time constants and correlation data in the control system's memory. During operation, the system quickly retrieves these pre-computed values and applies them to real-time electrical measurements, achieving both high precision and fast response without performing full CFD simulations during operation.
Solution Approach 2:
The patent transforms complex spatial and temporal CFD simulation parameters into simplified time constant parameters that can be quickly processed. By changing the representation from detailed spatial distributions to aggregated time constants that capture essential thermal behavior, the system achieves rapid calculations while maintaining accuracy.
Data Source
AI summary
A variable frequency drive system includes a power converter with a plurality of power cells supplying power to one or more output phases, each power cell having multiple switching devices, a plurality of sensors monitoring values of the power converter, and a control system in communication with the power converter and controlling operation of the plurality of power cells, wherein the control system is configured via computer executable instructions to access and utilize a multi-dimensional response surface to obtain an internal coolant flow rate.