Three-Phase Inverter Reactive Current Control for LVRT Overvoltage
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Solution Overview
Problem
Conventional three-phase inverters experience operational issues and hardware damage due to excessively high output voltages during low voltage ride-through in power grid failures, affecting normal operation and stability of the power supply system.
Innovation Solution
A controller for the three-phase inverter adjusts the output by providing a second positive-sequence reactive current when voltages exceed a preset threshold, reducing the voltage at the output end to prevent damage and ensure system stability, using a power conversion circuit to manage the reactive current based on determined voltage differences and correlations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the three-phase inverter provides reactive power for the power grid during low-voltage failure, then the voltage support capability is improved, but the output voltage becomes excessively high causing hardware damage
Solution Approach 1:
The patent implements dynamic adjustment of the reactive current output by the three-phase inverter based on real-time voltage monitoring. When the output voltage exceeds a preset threshold during low-voltage ride-through, the controller dynamically reduces the reactive current magnitude, transforming the static reactive power injection into a dynamic, adaptive process that prevents voltage escalation while maintaining support capability
Solution Approach 2:
The patent employs a feedback control mechanism where the controller continuously monitors the output voltage of the three-phase inverter and adjusts the reactive current accordingly. When voltage exceeds the threshold, the feedback signal triggers a reduction in reactive current injection, creating a closed-loop control system that automatically regulates voltage levels and prevents hardware damage
2Stability of the object's composition
If the three-phase inverter continuously operates during low-voltage failure, then the system stability is improved, but the hardware may be damaged due to high voltage
Solution Approach 1:
The patent enables the three-phase inverter to continuously operate during low-voltage failures by implementing dynamic reactive current adjustment. The system adapts its operating parameters in real-time, reducing reactive current when voltage thresholds are exceeded, thereby maintaining continuous operation for stability while protecting hardware from voltage-induced damage
Solution Approach 2:
The patent applies beforehand cushioning by setting preset voltage thresholds and preparing control strategies in advance. When voltage approaches critical levels during low-voltage ride-through, the pre-established control mechanism activates to reduce reactive current, cushioning the system against voltage spikes that could damage hardware before they occur
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 reduces output voltages to prevent damage and maintain system stability by dynamically adjusting reactive currents in response to voltage thresholds, enhancing the operational safety and efficiency of the power supply system.
Implementation Method 1
The power conversion circuit converts the direct current into the three alternating currents
Data Source
AI summary
A power supply system, a three-phase inverter, and a controller and a control method for a three-phase inverter. In the power supply system, after a low-voltage failure occurs in a power grid, a three-phase inverter outputs a first positive-sequence reactive current to the power grid through low voltage ride-through. When a voltage of at least one of three alternating currents output by the three-phase inverter is greater than a preset threshold, the three-phase inverter outputs a small second positive-sequence reactive current to the power grid through the three alternating currents, to reduce a voltage at an output end of the three-phase inverter and improve stability of the entire power supply system.