Motor-Driven Pump Frequency Control for Pressure Stability
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Solution Overview
Problem
Conventional PID control methods for motor-driven pumps in fluid systems are slow to respond to instantaneous changes in pressure or flow rate, leading to potential shutdowns due to transiently high flow rates exceeding pressure limits.
Innovation Solution
A method that dynamically adjusts the motor frequency by calculating a target frequency based on the outlet equivalent diameter and target pressure, using polynomial interpolation to determine maximum and minimum operating frequencies, and adjusting the motor frequency accordingly, with the option to return fluid to a liquid source if the target frequency exceeds these limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If PID control is used to maintain pressure setpoint, then pressure stability is improved, but response speed to instantaneous changes deteriorates
Solution Approach 1:
The system performs preliminary action by calculating target frequency in advance based on the relationship between outlet diameter, target pressure, and flow rate. When an outlet is selected, the controller pre-determines the required frequency adjustment, allowing the motor to respond immediately without waiting for PID error accumulation, thus resolving the contradiction between pressure stability and response speed.
2Speed
If motor frequency is adjusted rapidly to meet instantaneous pressure changes, then response speed is improved, but system stability deteriorates
Solution Approach 1:
The system implements feedback by continuously monitoring the actual pressure and comparing it with the target pressure. The controller adjusts the motor frequency based on the difference between actual and target values, ensuring that rapid adjustments are made only when necessary and that the system returns to stable operation once the pressure setpoint is achieved, thus maintaining both response speed and system stability.
3Productivity
If pump operates at high flow rate to meet demand, then productivity is improved, but pressure control accuracy deteriorates
Solution Approach 1:
The system applies dynamics by making the motor frequency adjustable and variable based on operating conditions. Instead of fixed-speed operation, the controller dynamically changes the frequency to match the required flow rate and pressure conditions, allowing the pump to operate efficiently at high flow rates while maintaining precise pressure control through real-time frequency adjustment.
Data Source
AI summary
A method for controlling a motor-driven pump in communication with a fluid system is provided. Preferably the method employs a frequency drive system to control the motor-driven pump. The control method is characterized in that the operating frequency of the motor can be adjusted very quickly and it is ensured to be operated in a safe frequency range no more than a rated current.