Parallel Inverter Current Equalization for Stable Islanded Grids
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Solution Overview
Problem
The challenge of unequal current distribution and instability in parallel inverter systems due to independent voltage regulation, leading to excessive DC currents and transient AC currents, is exacerbated by the need for high-speed communication networks for centralized control, particularly in isolated renewable energy systems.
Innovation Solution
A system with a master module that monitors and adjusts the output currents of multiple inverter modules to equalize current distribution, using low-speed communication for decentralized control, allowing each inverter to adjust locally based on internal measurements and tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a centralized control unit is used to monitor and adjust inverter outputs, then current distribution can be equalized, but communication delays and system complexity increase
Solution Approach 1:
Each inverter module autonomously measures its own output current and compares it with the average current calculated from all modules. The inverter then self-adjusts its output current based on the difference between its measured current and the average current, eliminating the need for centralized control and high-speed communication networks.
Solution Approach 2:
The system implements a feedback mechanism where each inverter module receives information about the average output current of all modules and adjusts its own output accordingly. This distributed feedback approach allows current equalization without requiring a complex centralized control system, as each module independently responds to the collective system state.
2Productivity
If inverters independently regulate voltage to meet load demand, then power delivery is maximized, but current distribution becomes unequal causing instability
Solution Approach 1:
The system changes the control parameter from independent voltage regulation to current regulation based on the average current of all modules. Each inverter adjusts its output current to match the calculated average, transforming the control strategy to maintain both high power delivery and system stability through parameter coordination rather than independent optimization.
Solution Approach 2:
The invention creates an equipotential state for current distribution by having all inverter modules operate at the same current level (the average current). This equalization approach prevents circulating currents and instability while maintaining maximum power delivery capability, as all modules contribute equally to the load without voltage conflicts.
3Measurement precision
If high-speed communication networks are deployed for real-time monitoring, then control precision is improved, but system cost and complexity increase
Solution Approach 1:
Each inverter module independently measures its own output current with precise local instrumentation and uses this information to self-regulate. This eliminates the need for expensive high-speed communication infrastructure, as precision measurement is performed locally at each module rather than requiring centralized high-speed data collection and processing.
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 approach enhances stability and reliability by minimizing transient currents and ensuring seamless operation, even with varying inverter capabilities, while reducing the need for expensive high-speed communication networks, thus supporting scalability and resilience in renewable energy systems.
Implementation Method 1
the inverter module is configured to invert the supplied direct current into an alternating current(s), thereby forming an alternating current source
Data Source
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AI summary
The present invention relates to the field of renewable energy systems, specifically to islanding inverters used for higher power or current applications suitable for electrical grids or standalone power systems. The invention addresses the challenges associated with connecting multiple islanding or grid inverters in parallel, providing a method and system for coordinated control and equal current distribution among the inverters to enhance overall stability and efficiency. An aspect of the present invention relates to a system comprising a plurality of inverter modules connected to a master module that monitors each inverter module's output current(s) and subsequently instructs each inverter module to adjust its output current(s) value to match a target current value, resulting in similar output current(s) from each inverter module. This configuration allows any number of inverter modules to be controlled by a single master module, ensuring that the paralleled modules deliver approximately similar output currents.