Three-Phase Micro-Inverter Circuit Topology for Current Balance

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Solution Overview

Problem

Existing solar photovoltaic power generation systems using three-phase micro-inverters are complex and costly due to the need for balanced current amplitudes between phases, which is difficult to maintain, especially in large-scale systems with varying environmental conditions.

Innovation Solution

A solar photovoltaic three-phase micro-inverter design that integrates three single-phase inverter circuits with adjacent DC photovoltaic assemblies, allowing for balanced AC current output by adjusting power conversion through a shared control circuit, eliminating the need for excessive elements and simplifying system design and installation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If three single-phase micro-inverters are connected in series as three groups to form a three-phase system, then the system can provide three-phase AC power grid connection, but the device complexity increases due to the need for multiple identical micro-inverters and DC photovoltaic assemblies to ensure current balance

Engineering Contradiction:

Improvethree-phase power grid connection capabilityVSAvoidnumber of electronic elements

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent divides the three-phase inverter function into three independent single-phase inverter circuits, each handling one phase independently. This segmentation allows each circuit to operate autonomously while collectively providing three-phase power grid connection capability, reducing the complexity of managing a unified three-phase system.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by allowing each single-phase inverter circuit to have different electronic element configurations based on local requirements. Each phase can be independently designed and adjusted, enabling flexibility in component selection while maintaining overall system functionality.

Inventive Principle:

Principle #3Local quality

2Reliability

If three groups of single-phase micro-inverters are used with the same micro-inverters and DC photovoltaic assemblies to ensure current balance, then the current amplitudes between phases are balanced, but the manufacturing cost increases

Engineering Contradiction:

Improvecurrent balance between phasesVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent employs parameter changes by allowing each single-phase inverter circuit to independently adjust its operating parameters (such as switching frequency, pulse width modulation duty cycle) to achieve current balance. This eliminates the need for identical hardware configurations across all phases, reducing manufacturing costs while maintaining reliability.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If three groups of single-phase micro-inverters are required to have the same configuration to ensure current balance, then the current amplitudes are balanced, but the difficulty of design and installation increases

Engineering Contradiction:

Improvecurrent balanceVSAvoiddesign and installation difficulty

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent applies dynamics by enabling each single-phase inverter circuit to dynamically adjust its output characteristics independently. This dynamic adjustment capability allows the system to maintain current balance without requiring identical static configurations, significantly simplifying design and installation processes.

Inventive Principle:

Principle #15Dynamics

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 ensures balanced three-phase AC current output to the power grid, reducing system complexity and cost while maintaining reliability and efficiency.

Implementation Method 1

three single-phase inverter circuits having input terminals coupled respectively with the three DC photovoltaic assemblies via the DC terminals, for converting the DC currents generated by the three DC photovoltaic assemblies to AC currents

Methodology Applied

Scientific EffectPower conversion:

Data Source

PatentUS9520721B2Solar photovoltaic three-phase micro-inverter and solar photovoltaic power generation system

Publication Date: 2016.12.13 ALTENERGY POWER SYST

AI summary

A solar photovoltaic three-phase micro-inverter comprises: DC terminals, coupled with three DC photovoltaic assemblies adjacent to each other; three single-phase inverter circuits having input terminals coupled respectively with the three DC photovoltaic assemblies via the DC terminals, for converting the DC currents generated by the three DC photovoltaic assemblies to AC currents, respectively; AC terminals coupled with a three-phase AC power grid; wherein output terminals of each single-phase inverter circuit are coupled respectively with a neutral wire and one of the three phases of the three-phase AC power grid. A solar photovoltaic power generation system is also provided. The three single-phase inverter circuits can be integrated as above Because the three DC photovoltaic assemblies on one three-phase micro-inverter are disposed adjacently and have similar environment conditions, such as illumination, temperature, etc., the three-phase AC current can be well balanced.