Power Conversion System for Rapid Grid Fault Response
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Solution Overview
Problem
Existing power conversion systems face challenges in reducing electric power generation quickly during grid faults, leading to potential power supply disruptions due to delays in detecting voltage fluctuations and the inertia of windmills, which results in operation stoppages and inability to reduce power generation in short time periods.
Innovation Solution
A power conversion system that includes AC/DC and DC/DC converters, controlled by a device to manage active and reactive current components and voltage, allowing for the suppression of incoming electric power from the generator during grid faults by adjusting command values, thereby stabilizing voltage fluctuations and ensuring operation continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pitch control and stall control of the windmill are used to reduce electric power generation during grid faults, then power generation can be reduced, but considerable delay time occurs from voltage fluctuation detection to command output, and the windmill's large inertia requires time to reduce rotation speed
Solution Approach 1:
The control device pre-calculates and stores optimal pitch angles corresponding to various active current command values before grid faults occur. When voltage fluctuations are detected, the control device immediately retrieves the pre-calculated pitch angle corresponding to the reduced active current command value, eliminating the need for real-time calculation and reducing response delay.
Solution Approach 2:
The invention replaces the mechanical control approach (direct windmill pitch control with slow response) with an electrical control system that rapidly adjusts the active current command value to the AC/DC converter. This electrical control signal is transmitted instantly, bypassing the slow mechanical response of windmill pitch adjustment and enabling rapid power generation reduction.
2Productivity
If the windmill rotation speed is reduced to decrease electric power generation, then power generation can be controlled, but the large inertia of the windmill makes it difficult to reduce power generation in a short time period
Solution Approach 1:
The invention introduces the AC/DC converter as an intermediary device between the windmill and the grid. Instead of directly controlling the windmill's mechanical parameters (pitch angle, rotation speed) which have slow response due to inertia, the control device rapidly adjusts the active current command value to the AC/DC converter. This intermediary electrical control enables fast power generation adjustment without being constrained by the windmill's mechanical inertia.
3Reliability
If conventional control methods are used during grid faults, then system operation may be stopped due to overvoltage protection, but this results in power supply disruption and loss of operation continuity
Solution Approach 1:
The control device continuously monitors the DC voltage level in the DC power grid and dynamically adjusts the active current command value to the AC/DC converter based on real-time voltage conditions. When voltage fluctuations are detected during grid faults, the control device rapidly reduces the active current command value to prevent overvoltage conditions, thereby avoiding operation stoppage by overvoltage protection and maintaining continuous power supply.
Data Source
AI summary
An AC/DC converter and a DC/DC converter are disposed corresponding to a power generator. The AC/DC converter converts AC power generated by the power generator into a generated voltage, and outputs the generated voltage to a power line. The DC/DC converter converts the generated voltage on the power line into a collection voltage, and outputs the collection voltage to a collection line. DC power in a DC voltage grid formed of the collection line is transmitted through a DC/AC converter to an AC power grid. When a short-circuit fault occurs in the DC power grid or the AC power grid, a control command value for the AC/DC converter or the DC/DC converter is adjusted so as to suppress incoming electric power flowing from the power generator in accordance with fluctuations of a collection voltage.