Single-Stage Solid-State Transformer With SAHC Power Factor 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 bus connections.
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 feedforward regulator for power factor correction and voltage regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple power stages are used in solid state transformers, then power factor correction and voltage regulation functions are achieved, but efficiency decreases due to series losses
Solution Approach 1:
The patent combines multiple power stages (rectification, DC-DC conversion, and inversion) into a single integrated solid state transformer stage. This merging eliminates the series connections between separate stages, thereby reducing cumulative series losses while maintaining all necessary power conversion functions through a unified resonant power converter architecture.
Solution Approach 2:
The single stage solid state transformer is designed to perform multiple functions simultaneously: power factor correction, voltage regulation, DC-DC conversion, and AC inversion. This multi-functionality is achieved through a universal resonant power converter topology that can operate in different modes to fulfill various power conversion requirements without requiring separate dedicated stages for each function.
2Loss of energy
If a single stage design is implemented, then efficiency is improved by reducing series losses, but the complexity of achieving isolated current and voltage controlled line connections increases
Solution Approach 1:
The single stage solid state transformer is segmented into distinct functional modules: a current controlled bridge for current controlled line connections, a voltage controlled bridge for voltage controlled line connections, and isolated DC ports. Each module handles specific control functions independently, which simplifies the overall control architecture while maintaining the benefits of a single stage design.
Solution Approach 2:
The patent introduces a transformer with resonant impedance as an intermediary element between the current controlled and voltage controlled bridges. This intermediary component enables galvanic isolation between the AC line connections and DC ports while facilitating controlled power transfer, thereby achieving the required isolated current and voltage controlled connections without adding excessive complexity to the single stage architecture.
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
The solution achieves efficient power factor correction, isolated DC to DC conversion, and regulated inverter output with reduced distortion, incorporating functions of a multi-stage system with fewer series parts, thereby enhancing efficiency and reducing series losses.
Implementation Method 1
a current controlled bridge and a voltage controlled bridge coupled by a transformer and resonant impedance
Implementation Method 2
The illustrated DC/DC converter (101) supports bidirectional power transfer through the use of inductive phase shift control. In prior art, the DC/DC converter may be configured to use a conventional resonant architecture which results in unity (or nearly constant) gain near resonance
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.