Self-Excited Power Converter Control for Isolated Grid Detection
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Solution Overview
Problem
Existing power converters fail to appropriately determine whether a generator is connected to an AC power system, especially when transitioning between interconnected and isolated systems.
Innovation Solution
A control device for a self-excited power converter that includes a phase error calculation unit and an isolated system determination unit to assess phase error and voltage magnitude, determining a shift from an interconnected system to an isolated system based on specific conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a power converter operates in an AC power system without a generator (isolated system), then the power converter must generate AC voltage on its own to supply power, but the control device cannot appropriately determine the generator connection status leading to operational errors
Solution Approach 1:
The control device monitors changes in system parameters (voltage, frequency, current) to detect transitions between interconnected and isolated system states. By detecting parameter variations that occur when a generator connects or disconnects, the control device can accurately determine the generator connection status and switch control modes accordingly, resolving the contradiction between operational adaptability and measurement precision.
2Reliability
If the control device switches between different operational modes based on generator connection status, then appropriate control can be applied for each mode, but complex control logic is required to accurately detect and respond to system state changes
Solution Approach 1:
The control device employs feedback mechanisms by continuously monitoring system parameters and comparing them against reference values or historical data. This feedback loop enables automatic detection of generator connection status and triggers appropriate control mode switches without requiring complex manual intervention or overly complicated control logic, thus improving reliability while managing device complexity.
Data Source
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AI summary
A control device (10) for controlling a self-excited power converter (20) connected to an alternating-current (AC) power system (101), includes: a phase error calculation unit (204) to calculate a phase error between a phase of a voltage command for the power converter (20) and a phase of a point-of-interconnection voltage at a point of interconnection between the AC power system (101) and the power converter (20); and an isolated system determination unit (211) to determine whether the AC power system (101) has shifted from an interconnected system to an isolated system, based on the phase error and a magnitude of the point-of-interconnection voltage, the interconnected system being the AC power system (101) connected to a generator (51), the isolated system being the AC power system (101) not connected to the generator. The isolated system determination unit (211) determines that the AC power system (101) has shifted from the interconnected system to the isolated system, when at least a first condition is met that the phase error is outside a reference range and the magnitude of the point-of-interconnection voltage is greater than a first voltage threshold.