Dual-Active-Bridge Micro-Inverter Modulation for Lower Transformer Current

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Solution Overview

Problem

Existing micro-inverters face inefficiencies due to high transformer secondary side current values and inadequate optimization of transformer magnetic element parameters, particularly in dual-active-bridge-type micro-inverters, which affect overall efficiency and performance.

Innovation Solution

Implement a power modulation mode switching method for dual-active-bridge-type micro-inverters, utilizing internal and external phase shift angles to adjust modulation modes, and perform hybrid optimization of transformer turn ratio and leakage inductance to minimize conduction losses and improve efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If dual-active-bridge-type micro-inverter uses fixed modulation mode, then control is simplified, but transformer secondary side current effective value increases and efficiency decreases

Engineering Contradiction:

Improvecontrol complexityVSAvoidtransformer secondary side current loss

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent implements dynamic modulation mode switching based on operating conditions. The system transitions from fixed modulation mode to dynamic mode selection, where the controller adjusts the modulation mode according to real-time power flow direction and magnitude, thereby optimizing transformer current and improving efficiency without excessive control complexity

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the modulation mode parameter dynamically based on operating conditions. By switching between different modulation modes (e.g., DAB mode 1, DAB mode 2, phase-shifted full-bridge mode) according to power flow direction and magnitude, the system optimizes transformer secondary current and reduces energy losses

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If transformer turn ratio and leakage inductance are not optimized, then device complexity is reduced, but conduction losses increase and efficiency decreases

Engineering Contradiction:

Improvetransformer parameter optimization complexityVSAvoidconduction loss

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent performs preliminary optimization of transformer parameters (turn ratio and leakage inductance) during the design stage. By pre-calculating and selecting optimal parameter values based on expected operating conditions, the system minimizes conduction losses without adding operational complexity or control burden

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces empirical transformer design with calculated optimization. Instead of relying on standard transformer designs, the system uses analytical methods to determine optimal turn ratio and leakage inductance values that minimize conduction losses for specific operating conditions

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If micro-inverter does not perform mode switching, then control is simpler, but efficiency under varying load conditions deteriorates

Engineering Contradiction:

Improvecontrol operation simplicityVSAvoidefficiency under varying loads

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

The patent implements feedback-based modulation mode selection. The controller monitors operating conditions (power flow direction, power magnitude) and automatically selects the appropriate modulation mode, providing adaptive efficiency improvement across varying load conditions while maintaining automated control simplicity

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent creates a universal control strategy that handles multiple operating conditions with a single integrated system. The modulation mode switching mechanism provides multi-functionality, adapting to different power flow directions and load conditions without requiring separate control systems for each scenario

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS20250239945A1Method for improving efficiency of micro-inverter and dual-active-bridge-type micro-inverter

Publication Date: 2025.07.24 SHANGHAI JIAOTONG UNIV

AI summary

The disclosure provides a method for improving the efficiency of a micro-inverter, and a dual-active-bridge-type micro-inverter. The method including: performing power modulation mode switching of a dual-active-bridge-type micro-inverter, such that the power is bi-directionally transmitted from a direct-current side to an alternating-current side and from the alternating-current side to the direct-current side, thereby reducing an effective value of a secondary side current of a transformer; and according to the modulation mode switching characteristic of the dual-active-bridge-type micro-inverter within a power frequency period, performing hybrid optimization on the turn ratio of a primary side to a secondary side and a transformer leakage inductance of a high-frequency transformer of the dual-active-bridge-type micro-inverter.