Inverter Control Method for Pump Pressure Transitions
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Solution Overview
Problem
Existing methods for controlling inverters in pump systems often result in sudden pressure changes that can damage pumps, as they fail to manage pressure transitions smoothly, leading to increased PID control burdens and pump damage.
Innovation Solution
A method for controlling an inverter that sets a pressure data reference and updates it periodically by a predetermined step when the difference between the reference and feedback pressure is less than a set value, allowing for gradual pressure adjustments and preventing sudden changes, thereby preventing pump damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If normal PID control is performed immediately after pre-PID, then response speed is improved, but pump damage occurs due to sudden pressure changes
Solution Approach 1:
The patent applies preliminary action by implementing a soft fill period before normal PID control. During this period, the reference pressure is gradually increased from the pre-PID pressure to the target pressure in predetermined steps, rather than immediately setting it to the target pressure. This gradual increase prevents sudden pressure changes that would damage the pump, while still maintaining relatively fast response through automated control.
Solution Approach 2:
The patent applies dynamics by making the reference pressure dynamic during the soft fill period. Instead of using a fixed reference pressure, the system dynamically adjusts the reference pressure in incremental steps based on the elapsed time and predetermined step values. This dynamic adjustment allows the system to adapt the pressure increase rate to prevent pump damage while maintaining control effectiveness.
2Productivity
If reference pressure is rapidly increased to target pressure, then productivity is improved, but pump damage occurs due to excessive pressure changes
Solution Approach 1:
The patent applies preliminary action by implementing a soft fill period before normal PID control. During this period, the reference pressure is gradually increased from the pre-PID pressure to the target pressure in predetermined steps, rather than immediately setting it to the target pressure. This gradual increase prevents sudden pressure changes that would damage the pump, while still maintaining relatively fast response through automated control.
Solution Approach 2:
The patent applies parameter changes by modifying the reference pressure parameter in a controlled manner during the soft fill period. The reference pressure is changed in predetermined steps rather than making a single large jump to the target pressure. This stepwise parameter change reduces the stress on the pump while still achieving the target pressure efficiently.
3Reliability
If pre-PID soft fill time is extended to prevent pump damage, then pump reliability is improved, but response time increases
Solution Approach 1:
The patent applies parameter changes by making the soft fill period adaptive rather than fixed. The reference pressure is increased in predetermined steps, and the system can adjust the number of steps and step sizes based on system conditions. This allows the soft fill period to be optimized - long enough to prevent pump damage but not excessively long to unduly delay the response.
Solution Approach 2:
The patent applies dynamics by making the reference pressure dynamic during the soft fill period. Instead of using a fixed reference pressure, the system dynamically adjusts the reference pressure in incremental steps based on the elapsed time and predetermined step values. This dynamic adjustment allows the system to adapt the pressure increase rate to prevent pump damage while maintaining control effectiveness.
Data Source
Figure 1a
Figure 1b
Figure 2~3
AI summary
A method for controlling an inverter is provided, the method including, setting, as a first reference, a pressure data returned from the pressure sensor when a pre-PID ends, updating the first reference that is increased by a predetermined step to a second reference, determining an output frequency of the inverter by performing a PID control using the second reference, and determining an output frequency of the inverter by performing the PID using a third reference set up by the user when the second reference or feedback pressure data is equal to a set value.