Boost-Isolated DC/DC MPPT Using Secondary-Side Current Sampling

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Solution Overview

Problem

Existing photovoltaic power generation systems face challenges in achieving accurate maximum power point tracking due to high cost, large volume, and signal delay or loss, particularly in micro single-phase inverters, where isolation sampling methods are costly and inefficient, and non-isolation sampling methods struggle to balance accuracy and loss in current sampling.

Innovation Solution

A power conversion device with a boost isolation DC/DC converter and a controller that moves the sampling circuit from the primary side of the transformer to the secondary side, using a non-isolation sampling method with a resistor and operational amplifier to accurately sample current and voltage, thereby reducing losses and delays, and a multi-channel boost isolation DC/DC converter system that improves power level and efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If isolation sampling method is used to sample photovoltaic component voltage and current, then safety and isolation are improved, but cost and device volume increase significantly

Engineering Contradiction:

Improveisolation safetyVSAvoiddevice volume

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent divides the sampling system into two independent parts: isolation sampling for voltage signals and non-isolation sampling for current signals. This segmentation allows each part to use the most appropriate sampling method, achieving both safety and cost-effectiveness.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent combines isolation sampling and non-isolation sampling methods into a unified control system. The controller integrates both sampling results to perform comprehensive maximum power point tracking, merging the advantages of both approaches.

Inventive Principle:

Principle #5Merging (Combining)

2Device complexity

If non-isolation sampling method is used to sample current, then cost is reduced, but sampling accuracy and power loss increase

Engineering Contradiction:

Improvesampling costVSAvoidcurrent sampling accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent applies different sampling qualities to different parameters: high-precision isolation sampling for voltage signals and cost-effective non-isolation sampling for current signals. This local differentiation optimizes overall system performance while controlling costs.

Inventive Principle:

Principle #3Local quality

3Power

If traditional boost circuit with high boost voltage ratio is used, then voltage conversion is achieved, but conversion efficiency decreases

Engineering Contradiction:

Improvevoltage conversion capabilityVSAvoidconversion efficiency

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The patent replaces the traditional single-stage boost circuit with a two-stage conversion system using high-frequency transformers. This substitution achieves voltage conversion through electromagnetic transformation rather than pure inductive boosting, reducing energy losses.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Device complexity

If one controller is used for both photovoltaic component control and inverter control, then device quantity is reduced, but control complexity and signal delay increase

Engineering Contradiction:

Improvecontroller quantityVSAvoidsignal delay

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The patent segments the control functions into separate controllers: one dedicated to photovoltaic component control and another to inverter control. This segmentation eliminates signal delays caused by isolation sampling and simplifies control logic in each controller.

Inventive Principle:

Principle #1Segmentation

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 high accuracy in current sampling with low loss and reduced design complexity, improving real-time control performance and reducing costs by eliminating the need for isolated sampling and minimizing the number of controllers and peripheral circuits.

Implementation Method 1

a first boost isolation DC/DC converter including a transformer

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

Photovoltaic components (also commonly known as solar photovoltaic panels) convert the received light into electrical energy in the form of direct current

Methodology Applied

Scientific EffectPhotovoltaic effect: Photovoltaic Effect

Data Source

PatentUS12149087B1Power conversion device and maximum power point tracking control method

Publication Date: 2024.11.19 FOXESS CO LTD

AI summary

A power conversion device for a photovoltaic system includes a first boost isolation DC/DC converter and a controller. The first boost isolation DC/DC converter includes a transformer, an input terminal of the first boost isolation DC/DC converter is connected to a first photovoltaic component, and an output terminal of the first boost isolation DC/DC converter is connected to a DC bus. The controller is configured to receive a bus voltage of the DC bus and a bus output current output by the first boost isolation DC/DC converter, and output, based on the bus voltage and the bus output current output by the first boost isolation DC/DC converter, a switch control signal that controls the first boost isolation DC/DC converter to perform maximum power point tracking control of the first photovoltaic component.