Break-before-make ATS for Soft Grid Interconnection
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Solution Overview
Problem
The integration of distributed generation (DG) into existing power grids poses challenges due to increased fault currents, which can render traditional protective devices ineffective and necessitate costly grid upgrades, leading to delays and high interconnect fees for DG developers.
Innovation Solution
A system utilizing a break-before-make automatic transfer switch (ATS) and bidirectional converters to seamlessly transfer power between the utility grid and distributed generators, allowing for symmetrical high current capability without requiring grid-side substation upgrades, thereby maintaining power quality and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If distributed generation is integrated into existing power grids, then power generation capacity and energy distribution are improved, but fault current increases rendering traditional protective devices ineffective
Solution Approach 1:
The patent introduces a break-before-make automatic transfer switch as an intermediary device between the distributed generation source and the power grid. This ATS ensures that the DG source is completely disconnected before reconnection occurs, preventing fault current propagation and protecting existing protective devices from being rendered ineffective by the added generation capacity.
Solution Approach 2:
The system segments the power distribution network into distinct zones: the utility grid side, the ATS transfer mechanism, and the distributed generation side. This segmentation isolates fault currents to their respective zones, preventing them from affecting the entire system and maintaining the effectiveness of protective devices in each segment.
2Reliability
If grid infrastructure is upgraded to handle higher fault currents from distributed generation, then system safety is improved, but project cost and implementation time increase
Solution Approach 1:
The break-before-make ATS serves as a mediator that allows the system to achieve high safety standards without requiring expensive grid infrastructure upgrades. By controlling the disconnection and reconnection sequence, the ATS prevents fault current propagation, maintaining system safety while avoiding the need to upgrade protective devices, breakers, or other grid infrastructure.
Solution Approach 2:
Instead of upgrading the entire grid infrastructure to handle higher fault currents, the patent uses the ATS to create a controlled environment where fault currents are managed at the point of interconnection. This approach copies the safety function of upgraded infrastructure through a more economical control-based solution.
3Loss of energy
If grid interconnect fees are assessed to cover infrastructure upgrades, then utility revenue is improved, but distributed generation project profitability decreases
Solution Approach 1:
The patent replicates the safety and protection functions that would otherwise require expensive grid infrastructure upgrades through the use of a break-before-make ATS. By copying these protective functions at the interconnection point rather than upgrading the entire grid, the solution eliminates the need for high interconnect fees while maintaining utility revenue streams.
Solution Approach 2:
The ATS provides a cost-effective alternative to expensive, long-term grid infrastructure upgrades. Rather than investing in permanent upgrades to substations and protective devices, the system uses a relatively simple, economical ATS device that achieves the same safety objectives at a fraction of the cost, thereby improving project profitability.
4Reliability
If approval delays are extended to evaluate grid changes, then grid safety is improved, but distributed generation project deployment speed decreases
Solution Approach 1:
The break-before-make ATS is designed and pre-configured with built-in safety mechanisms that automatically prevent fault current propagation. This preliminary action embeds safety controls directly into the interconnection device, eliminating the need for lengthy utility evaluations and approval processes while ensuring grid safety is maintained from the outset.
Solution Approach 2:
The ATS performs self-validation of safety conditions through its break-before-make operation, automatically ensuring that fault currents are contained without requiring external utility evaluation. This self-service safety mechanism streamlines the interconnection approval process, reducing deployment time while maintaining rigorous safety standards.
Data Source
AI summary
A system includes a break-before-make automatic transfer switch (ATS) configured to selectively couple a utility grid and at least one distributed generator (e.g., a plurality of paralleled generators) to a load bus such that, in a state transition of the ATS, the utility grid and the at least one distributed generator are both disconnected from the load bus before the utility grid or the at least one distributed generator is connected to the load bus. The system further includes at least one converter configured to be coupled to the load bus and configured to provide power to the load bus during the state transition of the ATS.