Grid-Connected Converter Control for High-Voltage Ride-Through
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Solution Overview
Problem
Grid-connected converters face challenges in high voltage ride-through scenarios, where excessive grid-connected currents can trigger an off-grid state due to reverse voltage differences across filtering inductors, leading to potential damage and instability.
Innovation Solution
A method and system for controlling a grid-connected converter that detects high voltage ride-through conditions, controls the inverting circuit to enter an off state, and adjusts the direct-current bus voltage using a converting circuit to reduce reverse voltage differences and prevent off-grid states, by determining when to cease the off state based on grid-connected current thresholds and stability of the direct-current bus voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the voltage of the direct-current bus is controlled to be an addition of a certain voltage and a peak of a line voltage of a grid-connected point, then the grid-connected inverter can operate normally under normal conditions, but during high voltage ride-through, the filtering inductor is under reverse voltage difference causing excessive grid-connected current
Solution Approach 1:
The patent dynamically adjusts the control mode of the converting circuit based on real-time detection of grid voltage conditions. During high voltage ride-through, the control mode switches from normal voltage control to direct-current bus voltage control, making the system adaptive to changing conditions and resolving the contradiction between normal operation reliability and protection against reverse voltage difference harm
Solution Approach 2:
The patent changes the control parameter from controlling voltage as sum of certain voltage and peak line voltage to directly controlling the direct-current bus voltage during high voltage ride-through. This parameter change allows the system to maintain proper voltage levels even when grid voltage exceeds normal ranges, preventing excessive current flow through the filtering inductor
2Reliability
If the grid voltage significantly exceeds the rated voltage (greater than 1.25 times), then the grid-connected inverter must withstand the high voltage, but the filtering inductor experiences long-term reverse voltage difference causing overcurrent protection trigger and off-grid state
Solution Approach 1:
The patent implements preliminary detection of high voltage ride-through conditions and preemptively switches the converting circuit to direct-current bus voltage control mode before excessive current can develop. This preliminary action prevents the filtering inductor from experiencing prolonged reverse voltage difference, avoiding overcurrent protection triggers while maintaining high voltage ride-through capability
Solution Approach 2:
The patent uses real-time feedback from grid voltage detection to dynamically adjust the converting circuit's control mode. When high voltage ride-through is detected, the feedback triggers a switch to direct-current bus voltage control, continuously monitoring and adjusting to maintain proper voltage levels and minimize the duration of reverse voltage difference across the filtering inductor
3Object-affected harmful factors
If the inverting circuit is controlled to enter off state during high voltage ride-through, then the reverse voltage difference is reduced, but the converting circuit must quickly compensate to maintain direct-current bus voltage stability
Solution Approach 1:
The patent extracts the voltage control function from the inverting circuit during high voltage ride-through by switching it to off state, and assigns this function to the converting circuit. This separation allows the inverting circuit to avoid reverse voltage difference harm while the converting circuit, operating in direct-current bus voltage control mode, compensates to maintain voltage stability
Data Source
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AI summary
A grid-connected converter and a method for controlling a high-voltage ride-through for a grid-connected converter are provided in the present disclosure. The method includes: obtaining detection data of a voltage of a grid-connected point of the grid-connected converter; determining, based on the detection data of a voltage of the grid-connected point, whether the grid-connected converter enters a high voltage ride-through mode; and controlling an inverting circuit of the grid-connected converter to enter an off state, and controlling a converting circuit connected to a direct-current bus to switch to a state of controlling a voltage of the direct-current bus, in a case that the grid-connected converter enters the high voltage ride-through mode.