Parallel Inverter Startup Using Pre-Charge to Limit Circulating Power
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Solution Overview
Problem
Existing inverter systems face challenges during startup, especially when multiple inverters are connected to create a higher power DC power supply, leading to inefficiencies and increased losses due to power circulation between inverters.
Innovation Solution
The implementation of an AC 'pre-charge' circuit or a DC 'jump-start' circuit for the startup of multiple inverters connected together, allowing for the generation of a DC voltage that can synchronize with the mains grid and facilitate connection to it.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple inverters are connected together to create higher power output, then the power supply capability is improved, but power circulation losses between inverters increase
Solution Approach 1:
The patent applies preliminary action by implementing a pre-charge circuit that charges the DC link capacitor before the inverter is fully connected to the grid. This preliminary charging action prevents power circulation losses by ensuring the DC link is already charged when the inverter connects, eliminating the need for power to flow back and forth during startup. The pre-charge contactor closes first to charge the capacitor through a dedicated pre-charge resistor, then the main breaker closes to connect the inverter to the grid, preventing circulation losses while enabling multiple inverters to operate at higher power levels.
2Adaptability or versatility
If multiple inverters are connected together to share loads, then the load sharing capability is improved, but the startup complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the startup process into distinct sequential stages: first the pre-charge contactor closes to charge the DC link capacitor, then the main breaker closes to connect the inverter to the grid. This segmentation of the startup process into separate, controlled steps simplifies the overall complexity by providing a clear, repeatable sequence that can be easily implemented across multiple inverters. Each inverter follows the same segmented startup procedure, making load sharing straightforward while maintaining manageable complexity.
3Device complexity
If inverters are started without pre-charge circuits, then the device complexity is reduced, but the startup reliability deteriorates
Solution Approach 1:
The patent implements preliminary action through the pre-charge circuit that charges the DC link capacitor before the inverter connects to the grid. This preliminary charging action significantly improves startup reliability by ensuring the DC link is already charged when the inverter connects, preventing startup failures and power circulation issues. The pre-charge contactor and resistor provide a dedicated charging path that reliably charges the capacitor to the required voltage level before main operation begins, making the startup process more reliable despite the added circuit complexity.
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
This solution enables efficient startup of multiple inverters, allowing them to share loads and reduce losses, thereby achieving a higher power output than individual inverters and ensuring stable operation.
Implementation Method 1
an AC 'pre-charge' circuit and/or a DC jump-start circuit is used for startup of two or more inverters connected to one another that are being used as a power supply. Both the AC pre-charge and the DC jump-start systems and methods can generate a DC voltage on the inverter that can be used for generating a mains synchronized AC voltage
Implementation Method 2
generate a DC voltage on the inverter that can be used for generating a mains synchronized AC voltage and connect the inverter to the mains grid
Data Source
AI summary
Electrical power system and methods for operating the power systems are disclosed. Embodiments include power systems configured for connection to loads that include green energy systems, such as hydrogen electrolyzers. Embodiments include multiple subcomponents, for example inverters, that alone produce insufficient power for the load but together produce sufficient power for the load. Embodiments include power systems with subcomponent input ports connected in parallel and output ports connected in parallel. Embodiments minimize the flow of electrical power between subcomponents during startup, and still further embodiments delay connection to the load until sufficient power is available to power the load. Additional embodiments allow two or more connected subcomponents to share a load larger than either of the subcomponents is capable of handling alone.