Power Converter Transient Ride-Through Control
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Solution Overview
Problem
Solar power conversion systems face challenges during transient events, such as damage to DC-AC converters due to excessive current and power imbalances at the DC bus, caused by variations in grid voltage and frequency.
Innovation Solution
A power conversion system with a voltage source control structure, incorporating a current limiter algorithm and voltage limiter, which limits current and DC bus voltage within predefined boundaries, and an anti-windup feature to protect semiconductor devices and maintain system stability during transient events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the DC-AC converter operates without current limiting during transient events, then the power conversion capability is maximized, but the converter may be damaged due to excessive current exceeding hardware limitations
Solution Approach 1:
The control system applies preliminary anti-action by detecting transient events (voltage sags, swells, or frequency deviations) and activating current limiting control before the converter can be damaged. The controller preemptively restricts current to safe levels while maintaining power conversion functionality, preventing the harmful overcurrent condition from occurring in the first place
Solution Approach 2:
The system dynamically switches between normal operation mode and transient event mode based on real-time grid conditions. During transient events, the control strategy transitions from maximum power conversion to current-limited operation, and then back to normal operation after the event, allowing the system to adapt its behavior to changing conditions while maintaining both power capability and reliability
2Adaptability or versatility
If the output power of the grid varies significantly due to change of grid voltage and frequency during transient events, then the system responds to grid conditions, but a power imbalance appears at the DC bus
Solution Approach 1:
The control system employs feedback mechanisms by continuously monitoring DC bus power balance and adjusting the DC-AC converter output accordingly. When a power imbalance is detected at the DC bus during transient events, the controller uses feedback signals to modify the converter's operation, ensuring that power input from the PV arrays matches power output to the grid, thereby maintaining DC bus stability despite varying grid conditions
Solution Approach 2:
The system maintains power balance by dynamically changing operating parameters including converter output power, voltage, and frequency in response to grid conditions. During transient events, the controller adjusts these parameters to match the varying grid capacity, allowing the system to adapt to changing grid voltage and frequency while preventing DC bus power imbalance through coordinated parameter modification
Data Source
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AI summary
A power conversion system is disclosed including a DC bus for receiving DC power; a line side converter electrically coupled to the DC bus for converting the DC power to AC power; and a voltage source controller to provide control signals to enable the line side converter to regulate the AC power. The voltage source controller comprises a signal generator to generate the control signals based at least in part on a power command signal and a power feedback signal. The voltage source controller further comprises a current limiter to, during a transient event, limit the control signals based at least in part on an electrical current threshold. The voltage source controller further comprises a voltage limiter to, during the transient event, limit the control signals based at least in part on a DC bus voltage feedback signal and a DC boundary voltage threshold.