Single-Stage Solid State Transformer With Harmonic Current Control
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Solution Overview
Problem
Prior implementations of solid state transformers have lower efficiency due to series losses from multiple power stages, and they lack a single stage design with isolated current and voltage controlled line connections and isolated DC ports.
Innovation Solution
A single stage solid state transformer system is developed using a current controlled bridge and a voltage controlled bridge coupled by a transformer and resonant impedance, with a synchronous average harmonic current (SAHC) compensator to control line current and transformer current, and a pulse width modulated voltage applied to the load, achieving power factor correction and isolated DC to DC conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If multiple power stages (AC/DC rectification, DC/DC conversion, DC/AC inversion) are used in solid state transformers, then bidirectional power transfer and voltage regulation are achieved, but efficiency decreases due to series losses from multiple stages
Solution Approach 1:
The patent combines multiple power conversion functions (AC/DC rectification, DC/DC conversion, DC/AC inversion) into a single integrated solid state transformer stage. This merging eliminates the series losses that occur when power passes through multiple separate stages, thereby improving overall efficiency while maintaining bidirectional power transfer capability and voltage regulation through the unified resonant power converter architecture
2Object-generated harmful factors
If conventional resonant architecture with inductive phase shift control is used, then bidirectional power transfer is supported, but distortion increases and requires additional filtering
Solution Approach 1:
The patent employs a synchronous average harmonic current (SAHC) compensator that uses feedback control to actively reduce distortion in the power transfer. The compensator monitors the current and applies corrective control actions to minimize harmonic distortion, eliminating the need for additional filtering components while maintaining bidirectional power transfer capability
Solution Approach 2:
The patent changes the control parameter from conventional inductive phase shift control to synchronous average harmonic current control. This parameter change enables direct distortion reduction through active control of the resonant power converter, improving power quality without requiring additional filtering hardware
3Adaptability or versatility
If large energy storage elements are omitted and inductive elements are added for current-fed arrangement, then bidirectional power transfer is enabled, but device size and complexity increase
Solution Approach 1:
The patent creates a universal resonant power converter architecture that can operate in bidirectional mode without requiring separate inductive elements or large energy storage components. The resonant converter itself provides the necessary functionality for bidirectional power transfer, eliminating the need for additional inductive elements and simplifying the overall device structure while maintaining adaptability for both power storage and generative loads
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 design enhances efficiency by reducing distortion and achieving power factor correction, isolated DC to DC conversion, and regulated inverter output, while maintaining a compact size similar to conventional transformers.
Implementation Method 1
a current controlled bridge and a voltage controlled bridge coupled by a transformer and resonant impedance
Implementation Method 2
resonant network (205) to align with the switching frequency
Data Source
AI summary
An input line connected current controlled bridge is dynamically coupled to an output line connected voltage controlled bridge of a single stage bidirectional isolated resonant power supply using a synchronous average harmonic current controller. A bridge current sensor measures low frequency and switching current across nodes of the current controlled bridge. Synchronous average harmonic bridge current is controlled using superimposed non-modulated and modulated feedback respectively to track a line current command and linearize coupling to the voltage controlled bridge. A power factor correction signal drives the line current command to regulate DC voltage busses. A feedforward and feedback trim circuit generates a command to the voltage controlled bridge to track input line voltage with attenuated harmonics. The single stage power supply has a defined interface to synchronize and regulate power sharing for one or more modules.