Microgrid Inverter Mode Switching With DC Bus Power Buffering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power distribution systems in microgrids experience undesirable power fluctuations and thermal stress during transitions between grid-following and grid-forming modes, leading to inefficiencies and degradation of distributed energy resources like fuel cell systems.
Innovation Solution
Implementing a DC braking module and energy storage module in conjunction with a site controller to regulate DC bus voltage, dissipate excess energy, and supply power as needed during mode transitions, ensuring smooth transitions and reduced thermal stress on distributed energy resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the multi-mode inverter system transitions between grid-following and grid-forming modes, then the power distribution system can adapt to grid availability changes, but power fluctuations and thermal stress occur on distributed energy resources
Solution Approach 1:
The patent introduces a DC bus as an intermediary energy buffer between the distributed energy resources and the multi-mode inverter system. During mode transitions, the DC bus absorbs or supplies energy to smooth out power fluctuations, preventing direct transmission of shocks to the DERs. This mediator role allows the system to adapt between grid-following and grid-forming modes while maintaining power stability for the connected DERs.
2Adaptability or versatility
If the distributed energy resources operate in grid-forming mode, then they can function independently during grid outages, but thermal stress and degradation occur due to mode transitions
Solution Approach 1:
The patent implements energy buffering capability on the DC bus that acts as a cushion before mode transitions complete. When transitioning to or from grid-forming mode, the DC bus pre-charges or discharges energy to cushion the thermal and electrical shocks that would otherwise directly affect the distributed energy resources. This beforehand cushioning reduces degradation and extends equipment longevity while maintaining independent operation capability.
3Speed
If the system transitions quickly between operating modes, then response time to grid changes is improved, but power fluctuations increase causing thermal stress
Solution Approach 1:
The DC bus serves as a mediator that decouples the speed of mode transitions from the magnitude of power fluctuations transmitted to DERs. The system can transition modes quickly for fast response to grid changes, while the DC bus intermediary absorbs the resulting power fluctuations and prevents them from causing thermal stress on the distributed energy resources.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides momentary power buffering and graceful transitions between operating modes, enhancing the reliability and longevity of distributed energy resources by minimizing power fluctuations and thermal shocks.
Implementation Method 1
The DC braking module is configured to dissipate excess energy, via energy dissipating circuitry, from the DC bus when the DC voltage value is greater than a threshold voltage value
Implementation Method 2
The energy storage module is configured to supply power to the DC bus for supporting the at least one load, when the DC voltage value in the DC bus is less than the load operating input
Data Source
AI summary
Systems and methods for microgrid-power distribution management when distributed energy resources transition between operating modes. The system includes a fuel cell system that generates DC power and a multi-mode inverter system that operates in one of the operating modes based on an availability status of grid, a site controller that receives electrical signal(s) facilitates the multi-mode inverter system to transition between the operating modes, generates a control signal based at least on an load operating input and transitioning of the multi-mode inverter system, a DC braking module that turns ON in response to receipt of the control signal, dissipates excess energy from the DC bus when the DC voltage value is greater than a threshold voltage value and energy storage module that turns ON in response to receipt of the control signal, supplies power to the DC bus, when the DC voltage value is less than the load operating input.