Microgrid Active Load Synchronization Without PLL Oscillation
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Solution Overview
Problem
Existing microgrid synchronization systems face challenges with stability due to the low inertia of inverter-based distributed generation units, particularly when dealing with constant power loads, which lead to frequency deviations and oscillatory responses, and traditional phase-locked loop (PLL) methods are inefficient and difficult to tune, impacting control performance.
Innovation Solution
A method that synchronizes an active load with a microgrid by obtaining reference frames for the active load and distributed generators, selecting a common reference frame, and tuning controller parameters to maintain predefined grid voltage, frequency, and phase values without using a PLL, thereby enhancing stability and control performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional phase-locked loop (PLL) methods are used for synchronization, then the microgrid can achieve grid connection, but the system experiences frequency deviations and oscillatory responses due to low inertia of inverter-based distributed generation units
Solution Approach 1:
The patent removes the traditional PLL synchronization unit from the microgrid system. By extracting this component, the system eliminates the oscillatory responses and frequency deviations that PLL introduces, particularly under low-inertia conditions with inverter-based distributed generation units. The microgrid operates without PLL-based synchronization, achieving improved frequency stability.
Solution Approach 2:
The patent changes the synchronization approach by abandoning PLL-based phase locking and instead using direct voltage and frequency matching between the microgrid and grid connection points. This parameter change in the synchronization methodology eliminates the oscillatory behavior inherent in PLL systems while maintaining effective grid connection capability.
2Ease of operation
If droop control scheme is employed to share power among DG units, then power sharing is achieved, but microgrid stability is affected by low inertia and generates frequency deviations
Solution Approach 1:
The patent introduces dynamic control mechanisms that adapt to the low-inertia characteristics of inverter-based DG units. By implementing dynamic frequency and voltage control strategies that respond to load changes and generation variations, the system maintains power sharing capability while compensating for the lack of mechanical inertia, thereby reducing frequency deviations and improving overall stability.
3Adaptability or versatility
If decentralized control schemes are used, then new DG units can be integrated without changing controller settings, but the system cannot manage operations with high levels of coordination
Solution Approach 1:
The patent segments the control functions into decentralized local controllers that maintain plug-and-play capability, while introducing a coordination layer that manages high-level operations. Each DG unit retains its independent controller settings, allowing easy integration, while the overall system achieves coordinated operation through distributed communication and control strategies that synchronize multiple units without requiring reconfiguration.
Data Source
AI summary
This disclosure presents a method, an apparatus, and a non-transitory computer readable medium to synchronize an active load with a microgrid having a plurality of distributed generators. The method comprises obtaining respective reference frames for the active load and each of the plurality of distributed generators. The method further comprises selecting the reference frame of a first distributed generator as a common reference frame for the microgrid. The method further comprises pooling the active load and the other distributed generators of the plurality of distributed generators on the common reference frame of the microgrid. The method further comprises tuning controller parameters of the active load and the plurality of distributed generators so that predefined grid voltage, frequency, and phase values of the microgrid are maintained.