Parallel Inverter Current Sharing for Stable Islanded Power
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing parallel inverter systems face challenges with unequal current distribution and instability due to independent voltage regulation, leading to excessive DC currents and transient AC currents, particularly in islanding systems relying on renewable energy sources, which are exacerbated by the lack of a centralized control mechanism, resulting in inefficiency and instability, especially in islanding systems, which existing technologies fail to address effectively.
Innovation Solution
A decentralized control system for parallel inverter modules that adjusts output currents based on internal measurements and a target current value, ensuring equal current distribution and stability without requiring high-speed communication networks, using a control module to synchronize and calibrate each inverter's output current and voltage, ensuring consistent voltage alignment, thereby enhancing responsiveness, and reducing dependency on centralized control module, the responsiveness, and enhancing responsiveness, thereby enhancing responsiveness, and reducing dependency on centralized control module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a plurality of inverters are connected in parallel to increase power output, then the system can meet higher power demands, but unequal current distribution and instability occur due to independent voltage regulation
Solution Approach 1:
The patent implements a feedback mechanism where each inverter measures its own output current and communicates this information to other inverters in the parallel system. Each inverter adjusts its output based on feedback from others, creating a self-regulating system that equalizes current distribution without requiring centralized control. This resolves the contradiction by maintaining system stability through decentralized feedback while preserving the increased power capability of parallel connection.
Solution Approach 2:
The patent enables each inverter to autonomously regulate its own output current based on measurements from the shared bus and internal sensing. Each inverter independently adjusts its voltage and current to match the target values derived from the average system output, eliminating the need for external coordination. This self-service approach maintains reliability while allowing parallel inverters to collectively deliver higher power.
2Ease of operation
If each inverter independently regulates voltage to meet load demand, then each inverter operates autonomously, but excessive DC currents and transient AC currents arise due to voltage discrepancies
Solution Approach 1:
Each inverter continuously measures its output current and the shared bus voltage, using this feedback to adjust its regulation strategy. By comparing its output with the average system output, each inverter can make real-time corrections to prevent voltage discrepancies that would otherwise cause excessive DC currents and transient AC currents, while maintaining autonomous operation.
Solution Approach 2:
The patent dynamically changes the operating parameters (voltage and current references) of each inverter based on real-time measurements. By adjusting these parameters according to the average system output and individual measurements, the system prevents harmful current flows while preserving autonomous operation of each inverter unit.
3Reliability
If a centralized control unit is used to coordinate inverters, then current distribution can be equalized, but high-speed communication networks and real-time monitoring are required, introducing delays and complexity
Solution Approach 1:
The patent divides the control function into segments distributed across each inverter unit rather than concentrating it in a central controller. Each inverter performs local measurements and adjustments based on simple communication with neighboring inverters through the shared bus. This segmentation achieves current equalization while eliminating the need for complex high-speed communication networks and real-time centralized monitoring.
Solution Approach 2:
Each inverter serves itself by autonomously measuring its output, calculating the target current based on average system output, and adjusting its own operation accordingly. This self-service approach achieves reliable current distribution equality without requiring centralized control infrastructure, high-speed communication networks, or real-time monitoring systems.
4Device complexity
If inverters operate without coordination in islanding systems, then system simplicity is maintained, but instability and potential conflicts in voltage regulation occur
Solution Approach 1:
The patent introduces minimal feedback mechanisms where each inverter measures its output current and shares this information with others through the existing power bus. This feedback enables automatic coordination and equalization of current distribution while maintaining the overall simplicity of the islanding system architecture. The feedback is implemented through simple measurements and adjustments rather than complex control infrastructure.
Solution Approach 2:
Each inverter autonomously regulates its own output based on local measurements and simple calculations of the average system output. This self-service approach provides voltage regulation stability without requiring complex centralized coordination systems, thereby maintaining system simplicity while preventing instability and conflicts in the islanding configuration.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention relates to parallel inverter systems for use in standalone power systems or electrical grids, particularly in higher power or current applications. The invention addresses challenges arising from the parallel operation of islanding or grid-connected inverters, such as current imbalance and instability. An aspect of the present invention relates to a system comprising a plurality of inverter modules connected in parallel via an electrical power distribution network and communicatively linked to a master control module. Each inverter module is configured to measure its output current and transmit the measurement to the master control module. The master control module determines a common target current value and transmits it to the inverter modules, which then adjust their respective output currents to match the target value. This coordinated control enables stable and balanced operation of multiple inverter modules operating in parallel.