Single Phase Control for Three Phase Inverter Current Sharing
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Solution Overview
Problem
Current inverter parallel systems face challenges in effectively controlling current sharing and reducing circulating currents between phases, leading to resource consumption and complexity due to the coupling of three phases.
Innovation Solution
A single phase controlling method is applied to a three phase inverting device, involving a de-coupling procedure to calculate a switching duty ratio using an average voltage, dividing the electric output into excitation and demagnetization states, and integrating these states to obtain a new switching duty ratio for the three phase switch, allowing for independent control of each phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If common controlling methods (centralized, client-server, circular track, distributed logic, wireless automatic) are used for current sharing in inverter parallel systems, then current sharing can be achieved, but the control complexity increases and resource consumption increases due to the coupling of three phases
Solution Approach 1:
The patent segments the three-phase control problem into three independent single-phase control problems. By treating each phase separately with independent single-phase controllers, the complex coupled three-phase control is divided into simpler uncoupled single-phase controls, reducing control complexity while maintaining current sharing performance
Solution Approach 2:
The patent introduces a single-phase equivalent circuit as an intermediary model to simplify the three-phase inverter control. This equivalent circuit serves as a mediator that translates the complex three-phase coupled system into a manageable single-phase system, enabling simpler control implementation
2Object-generated harmful factors
If common methods for reducing circulating currents (hardware reducing method, synchronous controlling method, switch modulating method) are applied, then circulating currents can be reduced, but the control complexity increases due to the coupling of three phases
Solution Approach 1:
The patent applies segmentation by treating circulating current reduction as three independent single-phase problems rather than one coupled three-phase problem. Each phase's circulating current is controlled independently through its own single-phase controller, simplifying the overall control complexity while effectively reducing circulating currents
Solution Approach 2:
The patent extracts the circulating current issue from the complex three-phase coupled system and addresses it separately in each phase. By taking out the circulating current problem from the global three-phase control and handling it at the single-phase level, the solution becomes simpler and more manageable
3Reliability
If three single phase inverters are used instead of one three phase inverter, then system reliability improves through parallel operation, but the voltage ripple increases and more switches are required leading to higher power loss and manufacturing cost
Solution Approach 1:
The patent makes each single-phase inverter module universal by enabling it to function independently while also being capable of parallel operation. The single-phase equivalent circuit control method allows each module to maintain its own current sharing and circulating current reduction capabilities, making the system equally efficient whether operating as one unit or multiple parallel units
Solution Approach 2:
Each single-phase inverter module performs self-service by independently controlling its own current sharing and circulating currents through the single-phase equivalent circuit method. This self-control capability eliminates the need for additional switches and complex coordination, reducing power loss while maintaining reliability through parallel operation
Data Source
AI summary
A three phase inverting device includes a three phase inverter module and a three phase filter module. The three phase inverter module includes a plurality of switches, each two switches are connected for forming a bridge arm, an input end of each of the bridge arm are coupled for forming a DC end, the DC end is connected to a DC load. The three phase filter module is connected to the three phase inverter module, wherein the three phase filter module includes a plurality of inductances and a plurality of capacitances, the inductances are connected at one side of the capacitances, a portion of the capacitances are connected to a output end of each of the bridge arm of the three phase inverter module, a portion of the inductances are connected to an AC end.