Interleaved Inverter Topology for High-Density Grid Conversion
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Solution Overview
Problem
Existing string inverters face challenges in achieving high power density, efficiency, and cost-effectiveness due to limitations in switching frequency and the size of reactive elements, particularly when using silicon insulated-gate bipolar transistors (Si IGBTs).
Innovation Solution
The use of wide bandgap materials such as silicon carbide (SiC) MOSFETs allows for higher switching frequencies, reducing the size of reactive elements and improving power density. A converter circuit is optimized to minimize the size and cost of magnetics, capacitors, and semiconductor devices, enabling a modular approach for further power rating increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If Si IGBTs are used for switching, then cost is reduced and reliability is improved, but switching frequency is limited to 1-10 kHz which increases the size of reactive elements
Solution Approach 1:
The patent changes the material parameter of the switching device from silicon (Si) to wide bandgap materials (SiC, GaN), enabling operation at higher switching frequencies (hundreds of kHz to MHz) which directly reduces the size of reactive elements while maintaining system reliability
Solution Approach 2:
The patent employs composite material structures including wide bandgap semiconductor materials (SiC MOSFETs, GaN HEMTs) combined with planar magnetic elements and integrated capacitor designs, creating a hybrid system that achieves high power density while managing the trade-offs between switching frequency and component size
2Power
If switching frequency is increased beyond Si IGBT capabilities, then power density is improved, but Si IGBTs cannot operate at these frequencies
Solution Approach 1:
The patent fundamentally changes the material parameter from silicon to wide bandgap materials (SiC, GaN) which have higher breakdown fields and faster switching capabilities, enabling operation at frequencies in the hundreds of kHz to MHz range while maintaining device reliability
Solution Approach 2:
The patent replaces the mechanical/physical limitations of Si IGBT switching with wide bandgap semiconductor physics, utilizing the superior electron mobility and breakdown characteristics of SiC and GaN materials to achieve higher switching speeds without mechanical wear or thermal degradation
3Power
If wide bandgap transistors like SiC MOSFETs are used, then switching frequency is increased to several hundred kHz improving power density, but cost increases significantly
Solution Approach 1:
The patent segments the inverter into modular phases, each with its own fast-switching half-bridge module, allowing independent optimization and manufacturing of each module. This modular approach enables economies of scale and standardized production processes that reduce overall system cost despite using expensive wide bandgap devices
Solution Approach 2:
The patent merges multiple functions into integrated planar structures where magnetics and capacitors are combined in a single planar element, reducing the total component count and assembly cost. The interleaved configuration of multiple phases also merges their reactive elements to cancel harmonics, reducing the need for additional filtering components
4Power
If conventional wound magnetics are used at 10 kHz, then reliability is maintained, but size and cost are quite large requiring manual insertion
Solution Approach 1:
The patent replaces traditional wound magnetic components with planar magnetic structures fabricated using PCB-like techniques. This substitution transforms a mechanical assembly process (manual insertion of large inductors) into a automated electronic fabrication process, enabling high-volume manufacturing with standard SMT equipment
Solution Approach 2:
The patent transitions from three-dimensional wound magnetic cores to two-dimensional planar magnetic structures that are integrated directly into the circuit board. This dimensional reduction allows automated manufacturing and significantly decreases the overall size of the inverter while maintaining the required inductance values at higher switching frequencies
Data Source
AI summary
Inverters that interface dc and ac power sources and loads are provided. An example application is solar power systems, in which a dc source of power is an array of solar panels; the inverter converts the dc power supplied by these panels to ac power that is fed into the utility grid. Another example is battery energy storage; the inverter changes the dc power of the batteries into ac power that is fed into the grid, and also can convert (rectify) ac power from the grid for charging the batteries. In one embodiment, for example, an inverter comprises slow switches that generate a three-level ac voltage, followed by a plurality of fast-switching half-bridges that introduce high-frequency pulse-width modulation into a plurality of ac output voltages.