Power Conversion Control System Phase Compensation
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Solution Overview
Problem
Conventional power conversion control systems, particularly those using phase-locked-loop (PLL) circuits, fail to respond quickly enough during transient conditions such as Low Voltage Ride Through (LVRT), Zero Voltage Ride Through (ZVRT), or High Voltage Ride Through (HVRT), leading to potential reversed active power flow and inappropriate reactive power control.
Innovation Solution
A multi-phase power distribution system incorporating a phase-locked-loop (PLL) circuit and a phase compensation circuit that tracks phase displacement between the grid's instantaneous reference phase and the synchronized phase signal, sending a phase compensation signal when the displacement exceeds a threshold, ensuring smooth control during transient conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional PLL circuit is used for generating synchronized phase and frequency signals, then the system works well under steady operating conditions, but the response speed is too slow during transient conditions such as LVRT, ZVRT, or HVRT
Solution Approach 1:
The control system is segmented into two parallel pathways: a conventional PLL circuit for steady-state operation and a phase displacement detection circuit for transient conditions. Each pathway operates independently and can be selectively activated based on system conditions, allowing the system to leverage the reliability of PLL during normal operation while gaining fast response capability during transients through the alternative detection pathway.
2Device complexity
If the PLL circuit is used during transient conditions, then the system structure remains simple, but the phase displacement tracking is insufficient leading to reversed active power flow or inappropriate reactive power control
Solution Approach 1:
A phase displacement detection circuit acts as an intermediary component that specifically monitors phase displacement during transient conditions. This intermediary circuit works in parallel with the PLL circuit and provides supplementary phase information when needed, enabling accurate tracking during transients without replacing the entire control system structure.
Solution Approach 2:
The system dynamically switches between or combines the outputs of the PLL circuit and the phase displacement detection circuit based on operating conditions. During steady-state operation, the PLL circuit dominates; during transient conditions, the phase displacement detection circuit becomes active to provide fast response. This dynamic adaptation allows the system to maintain simplicity during normal operation while achieving high reliability during transients.
Data Source
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AI summary
A power distribution system (10) comprises a power conversion module (12) for performing power conversion between a DC voltage at a DC side (14) and an AC power at an AC side (16), and a conversion control system. The AC side of the power conversion module is electrically coupled to a grid (18). The conversion control system includes a phase-locked-loop circuit (32) for receiving a multi-phase reference signal (40) of a grid voltage and for generating a synchronized signal (42), a regulator (52) for receiving reference commands, a two-phase grid feedback signal, and the synchronized signal and for generating a control signal for the power conversion module, and a phase compensation circuit (64) for receiving the synchronized signal and the multi-phase reference signal of the grid voltage, for obtaining a phase displacement signal (70), and for generating a phase compensation signal (66) for compensating the reference commands or for compensating the synchronized signal when the phase displacement signal exceeds a threshold value.