Isolated Three-Phase Inverter Circuits for Load Balancing
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Solution Overview
Problem
Inverter systems regulating line to line voltage face challenges with unbalanced loads, requiring high-voltage DC buses, large and costly capacitors, and high-voltage switches, which complicate control and reduce efficiency, whereas line to neutral regulation offers better load balancing and reduced component costs but introduces complexity with isolated DC busses and potential circulating currents.
Innovation Solution
Implementing isolated inverter circuits with dedicated isolated DC busses generated from isolated energy sources, such as batteries or solar arrays, to reduce the need for high-voltage components and transformers, allowing for individual phase control and improved efficiency by using lower-rated switches and capacitors, and providing isolation to prevent circulating currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If line to line voltage regulation is implemented, then voltage control capability is improved, but device complexity increases due to requiring high-voltage DC buses and large capacitors
Solution Approach 1:
The patent divides the three-phase inverter system into three separate single-phase inverter circuits, each with its own isolated DC bus. This segmentation allows each phase to be controlled independently while reducing the voltage rating requirements for individual components, thereby lowering overall system complexity despite maintaining voltage control capability.
Solution Approach 2:
The patent introduces isolated DC-DC converters as intermediary devices between the energy sources and the inverter circuits. These converters provide galvanic isolation and generate the required DC bus voltages for each phase, enabling voltage control while using lower-voltage rated components and reducing the complexity associated with direct high-voltage handling.
2Power
If high-voltage DC buses are used for line to line regulation, then voltage control is improved, but component costs increase due to requiring high-voltage switches and large capacitors
Solution Approach 1:
By segmenting the inverter into three independent single-phase circuits with isolated DC buses, the patent reduces the voltage rating requirements for switches and capacitors in each circuit. This allows the use of lower-cost, lower-voltage rated components while maintaining the overall voltage control capability of the three-phase system.
Solution Approach 2:
The isolated DC-DC converters act as intermediaries that step down or isolate the voltage from energy sources to appropriate levels for each phase. This enables the use of cost-effective lower-voltage components in the inverter circuits while still achieving the required voltage control performance.
3Ease of operation
If isolated DC busses are implemented for line to neutral regulation, then load balancing is improved, but device complexity increases due to potential circulating currents
Solution Approach 1:
The patent extracts and eliminates the circulating current issue by using isolated DC-DC converters for each phase. The galvanic isolation provided by these converters prevents circulating currents between phases while maintaining the load balancing benefits of isolated DC buses, thereby improving ease of operation without proportionally increasing device complexity.
4Device complexity
If non-isolated inverter circuits are used, then device complexity is reduced, but reliability decreases due to susceptibility to electrostatic discharge and poor electromagnetic immunity
Solution Approach 1:
The patent introduces isolated DC-DC converters as intermediary devices that provide galvanic isolation between energy sources and inverter circuits. This isolation protects the system from electrostatic discharge and improves electromagnetic immunity, enhancing reliability while adding manageable complexity through standardized isolation modules.
Data Source
AI summary
An isolated bus inverter system including inverter circuits and a controller. The inverter circuits include a switching array to provide a polyphase alternating current (AC) signal to an output. Each of the inverter circuits includes an energy source isolated from the other inverter circuits of the inverter circuits or a reference isolated from the other inverter circuits of the inverter circuits. The controller is configured to generate timing signals for the inverter circuits to generate the AC signals for the output based on DC signals received from one or more rectifier circuits.