Variable Speed Pumped Storage Rotational Speed Control
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Solution Overview
Problem
Conventional variable-speed pumped storage power generation apparatuses experience disturbances in power systems due to sudden changes in power output commands, particularly at low head operations, and PID control leads to continuous guide vane opening corrections causing rotational speed overshoot, which can result in slip frequency approaching the variable speed range limits.
Innovation Solution
A variable-speed pumped storage power generation apparatus with a rotational speed controller incorporating proportional, integral, and differential control elements, and a power output command change rate limiter that adjusts the maximum change rate of the power output command based on the slip frequency deviation from the normal operating range to prevent sudden changes and disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If speed control is performed by pump turbine flow control, then the generator motor can respond quickly to power output commands, but rotational speed fluctuations and overshoot are inevitable
Solution Approach 1:
The patent implements a feedback control mechanism where the actual rotational speed is continuously measured and compared with the target rotational speed. Based on the speed deviation, the control system adjusts the guide vane opening of the pump turbine to correct speed fluctuations and prevent overshoot, thereby maintaining stable operation while responding to power output commands.
2Reliability
If protection control is applied by adding power output correction commands when slip frequency approaches limits, then the variable speed range is protected, but the power output command is disrupted causing disturbances to the power system
Solution Approach 1:
The patent applies preliminary action by setting maximum change rate limits on power output commands before the slip frequency reaches critical limits. The control system proactively restricts the rate of change of power output commands based on current operating conditions, preventing the slip frequency from approaching dangerous levels while avoiding sudden disruptions to the power system.
3Measurement precision
If PID control is used for rotational speed control, then the rotational speed can be precisely controlled, but continuous guide vane opening corrections cause rotational speed overshoot
Solution Approach 1:
The patent modifies the PID control by introducing a maximum change rate limit on the guide vane opening adjustments. Instead of allowing continuous full-strength corrections, the control system applies partial corrections that are constrained by predetermined rate limits, preventing excessive adjustments that would cause rotational speed overshoot while maintaining sufficient control precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively prevents power output disturbances in the power system by limiting the maximum change rate of the power output command, thereby maintaining stable operation within the predetermined speed range and reducing rotational speed overshoot.
Implementation Method 1
a variable speed generator motor 101 that has a primary side synchronously connected to a commercial power system 4 through a frequency converter 103 and a rotor 102 that rotates at a variable speed
Implementation Method 2
a pump turbine 102 that is directly connected to the rotor 102 of the variable speed generator motor 101 to drive the rotor 102 in a power generation mode and be driven by the rotor 102 in a pumping mode
Data Source
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AI summary
A variable-speed pumped storage power generation apparatus of the present invention includes a variable speed generator motor that has a primary side synchronously connected to a commercial power system though a frequency converter is included and a rotor rotates at a variable speed, and a pump turbine that is directly connected to the rotor of the variable speed generator motor to drive the rotor in a power generation mode and be driven by the rotor in a pumping mode. The variable-speed pumped storage power generation apparatus sets a maximum change rate of the power output command constant when a slip frequency is within a normal operating range, limits the maximum change rate of the power output command by multiplying the maximum change rate by a value in a range of one to zero when the slip frequency is within a range falling below a lower limit of the normal operating range by a predetermined value or less or within a range exceeding an upper limit of the normal operating range by a predetermined value or less, and limits the maximum change rate of the power output command by multiplying the maximum change rate by zero when the slip frequency is in a range falling below the lower limit by the predetermined value or more or in a range exceeding the upper limit by the predetermined value or more.