Gas Compressor Inverter Control for Discharge Pressure Stability
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Solution Overview
Problem
Existing gas compressor control methods fail to adequately manage discharge pressure variations, leading to excessive pressure increases when air usage decreases sharply, without timely inverter-based rotational speed control.
Innovation Solution
A gas compressor system with multiple compressor units, each driven by a motor controlled by an inverter, where a control device adjusts the drive frequency to predict and manage pressure changes by stopping units when a threshold is exceeded, thereby maintaining stable discharge pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inverter-based rotational speed control is used to maintain constant discharge pressure, then the discharge pressure can be kept stable, but when the amount of used air sharply decreases, the discharge pressure rises more than necessary and exceeds the upper-limit pressure before the control responds in time
Solution Approach 1:
The control device performs preliminary action by calculating the prediction time for discharge pressure to reach the stopping pressure before it actually exceeds the upper limit. This allows the system to take preventive measures (stopping a compressor body) before the pressure control failure occurs, rather than reacting after the pressure has already risen excessively.
Solution Approach 2:
The control device continuously monitors the drive frequency and discharge pressure, and uses this feedback information to calculate the prediction time. When the prediction time falls below the threshold, the system automatically adjusts the number of operating compressor bodies, creating a closed-loop control system that responds to changing conditions in real-time.
2Loss of energy
If the number of operating compressor bodies is reduced to match decreased air usage, then energy consumption is reduced, but the discharge pressure may rise excessively before the control system responds
Solution Approach 1:
The system calculates the prediction time in advance to determine when reducing the number of compressor bodies is necessary, before the pressure control failure actually occurs. This preliminary calculation allows for smooth, planned transitions in the number of operating units rather than sudden reductions that could cause pressure instability.
Solution Approach 2:
The control system dynamically adjusts the number of operating compressor bodies based on real-time calculation of prediction time. Rather than using fixed thresholds or static control rules, the system adapts its operation continuously based on the calculated time-to-failure metric, optimizing both energy efficiency and pressure stability.
Data Source
AI summary
The purpose of the present invention is to provide a gas compressor capable of reducing variation in discharge pressure through control of the number of compressor bodies and a control method for the gas compressor. In order to solve the problem, this gas compressor includes a plurality of compressor units each having a compressor body, a motor for driving the compressor body, and an inverter for controlling a rotational speed of the motor, and a control device for controlling the inverters. Discharge pipes of the compressor bodies converge on one main discharge pipe. A drive frequency of the motor of each compressor body is controlled by the corresponding inverter, whereby a pressure of each discharge pipe is controlled and a discharge pressure of the main discharge pipe is controlled. When the discharge pressure of the main discharge pipe has increased in a period of reduction in the drive frequency of the motor of the compressor body before the drive frequency reaches a lower-limit frequency, the control device calculates a prediction time for reaching a stopping pressure. The control device stops one of the compressor bodies when the prediction time is less than a threshold value.