Self-Excited Reactive Power Compensation Control
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Solution Overview
Problem
Self-excited reactive power compensation apparatuses face challenges in responding quickly to sudden voltage fluctuations, leading to overcurrent issues and inadequate suppression of overvoltage in power systems, particularly after system troubles are resolved.
Innovation Solution
A self-excited reactive power compensation apparatus with a control device that includes a voltage detector, current detector, and a control system with a reactive current detecting unit, voltage control unit, and a selecting unit to generate drive signals for switching elements, allowing for the selection of voltage references to manage reactive current output and suppress overvoltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If feedback control is used to control system reactive power, then the control is simple to implement, but the response speed is slow and cannot follow sudden voltage fluctuations
Solution Approach 1:
The patent applies feedforward control by calculating the output voltage command based on the phase and amplitude of the set alternating current before the control action is executed. This preliminary calculation allows the system to anticipate and respond to voltage fluctuations without waiting for feedback, thereby improving response speed while maintaining manageable system complexity through the use of pre-computed control signals.
2Speed
If feedforward control is applied to improve response speed, then the system can respond quickly to voltage changes, but the apparatus may output the same voltage as the overvoltage that occurs at the power system
Solution Approach 1:
The patent combines feedforward control with feedback control in a hybrid control system. The feedforward component provides quick response by calculating output voltage based on set current parameters, while the feedback component continuously monitors the actual output voltage and system voltage, detecting overvoltage conditions and correcting the control signal accordingly. This dual-control approach maintains fast response speed while preventing harmful overvoltage output.
3Reliability
If the apparatus follows sudden voltage fluctuations during system trouble, then system stability is enhanced, but overcurrent may flow through the converter
Solution Approach 1:
The patent implements dynamic control by continuously adjusting the output voltage command based on real-time detection of system voltage and current conditions. The control system dynamically modifies the reactive current command and output voltage amplitude according to the instantaneous system state, allowing the apparatus to follow voltage fluctuations and maintain system stability while dynamically preventing overcurrent by adjusting the converter output within safe operating limits.
Data Source
AI summary
A control device of a self-excited reactive power compensation apparatus controls a reactive current output from a self-excited converter to a power system. The control device includes a first reference generating unit, a second reference generating unit, and a selecting unit. The first reference generating unit generates a first voltage reference of an output voltage output from the self-excited converter, such that the reactive current detected by a reactive current detecting unit follows a current reference. The second reference generating unit generates a second voltage reference of the output voltage output from the self-excited converter, such that a value of the reactive current becomes a predetermined value. The selecting unit selects a maximum value from the first and second voltage references.