Variable-Speed Pumping Control for Power Input Deviation
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Solution Overview
Problem
Conventional variable speed pumping systems experience deviations between power input commands and actual power inputs due to pump turbine performance errors, device aging, and uneven flow distribution, leading to continuous differences between power input commands and actual power inputs.
Innovation Solution
A variable speed pumping system that includes a power control correction signal generator which subtracts the actual power input from the power input command, adds a gain to the difference between the power input command and actual power input, and inputs this value to an integration control element to generate a power control correction signal, ensuring the power input command aligns with the actual power input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If speed control is performed to match rotational speed with rotational speed command in pumping mode, then rotational speed followability is improved, but power input deviation from power input command occurs due to pump turbine performance conversion errors and device aging
Solution Approach 1:
The patent implements a dual feedback control mechanism: (1) speed feedback that compares actual rotational speed with rotational speed command to generate speed control signals, and (2) power feedback that compares actual power input with power input command to generate power control correction signals. The power control correction signal generator integrates the power deviation signal and applies it to adjust the rotational speed command, creating a closed-loop feedback system that simultaneously maintains rotational speed followability and power input accuracy despite pump turbine performance degradation over time
Solution Approach 2:
The patent dynamically adjusts the rotational speed command parameter based on power deviation. The power control correction signal generator calculates the difference between power input command and actual power input, integrates this deviation over time, and adds a corrected value to the rotational speed command. This parameter transformation allows the system to compensate for pump turbine performance conversion errors and aging effects by modifying the speed setpoint to achieve the desired power input
2Speed
If integration control element accumulates control value to eliminate rotational speed deviation, then rotational speed matching is improved, but power input command and actual power input difference accumulates in steady state
Solution Approach 1:
The patent introduces a power feedback loop that operates parallel to the speed feedback loop. The power control correction signal generator continuously monitors the difference between power input command and actual power input, integrates this power deviation, and uses it to correct the rotational speed command. This dual feedback approach ensures that while the integration element maintains rotational speed matching, the power deviation is simultaneously compensated through rotational speed command adjustment
Solution Approach 2:
The patent segments the control function into two independent but interacting control loops: a speed control loop that handles rotational speed matching through integration of speed deviation, and a power control loop that handles power input accuracy through integration of power deviation. The power control correction signal generator acts as an interface between these two loops, allowing each loop to optimize its function without interfering with the other's stability
3Device complexity
If conventional speed control is used without power deviation consideration, then system simplicity is maintained, but power input command and actual power input difference occurs due to pump turbine performance errors and uneven flow distribution
Solution Approach 1:
The patent makes the power control correction signal generator perform multiple functions: it calculates rotational speed deviation, integrates speed deviation for speed control, calculates power deviation, integrates power deviation, and generates corrected rotational speed commands. This multi-functional approach adds power input accuracy capability to the existing speed control system without requiring a completely separate control system, thereby limiting the increase in device complexity while significantly improving measurement precision
Data Source
AI summary
A variable speed pumping system includes a generator motor including a frequency converter, in which the variable speed pumping system, in the pumping mode, supply a power command to the generator motor to perform power control, and the power control correction signal generator adds a value obtained by multiplying a signal based on a difference between the power input command and an actual power input measured by a power detector in the pumping mode by a constant gain to a signal based on the deviation and inputs the added value to an integration control element to generate the power control correction signal based on an output signal of the integration control element.