Single-Stage Multi-Path DC Converter for Independent MPPT
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Solution Overview
Problem
Existing photovoltaic inverters with a two-stage structure suffer from lower transmission efficiency due to their design, which complicates control and increases system complexity.
Innovation Solution
A single-stage multi-path DC access converter is introduced, featuring AC-side and DC-side conversion circuits connected through transformers, allowing independent MPPT control and AC frequency conversion, with transformers' secondary windings connected in parallel to an AC-side conversion circuit to achieve power decoupling and efficient conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a two-stage structure is used with isolated DC converter and inverter circuit, then control is simplified and module-level operation is achieved, but transmission efficiency decreases and system complexity increases
Solution Approach 1:
The patent combines the isolated DC converter and inverter circuit into a single integrated converter structure. The single-stage converter integrates the functions of both stages, eliminating the intermediate bus capacitor and reducing the number of switching operations. This merging approach directly addresses the technical contradiction by maintaining control simplicity while significantly improving transmission efficiency through reduced energy losses at conversion interfaces.
Solution Approach 2:
The single-stage converter is designed to perform multiple functions simultaneously: it achieves isolated DC-DC conversion, AC-DC conversion, MPPT control, and grid synchronization within a unified structure. This multi-functionality allows the system to maintain the operational flexibility of module-level control while eliminating the efficiency penalties associated with cascaded conversion stages.
2Productivity
If a two-stage structure with isolated DC converter is used, then MPPT and busbar boosting are achieved, but the upper limit of transmission efficiency is reduced
Solution Approach 1:
The patent merges the MPPT function and transmission conversion into a single integrated stage. The single-stage converter performs maximum power point tracking while simultaneously executing the power conversion function, eliminating the need for separate MPPT preprocessing. This integration ensures that power is converted directly from the photovoltaic module at optimal efficiency points without intermediate energy losses.
3Adaptability or versatility
If multiple converters are used for multi-path DC access, then independent control is achieved, but device complexity and manufacturing cost increase
Solution Approach 1:
The single-stage converter is designed as a universal platform that can handle multiple independent DC input paths through a unified control architecture. Each input path maintains independent MPPT control capability, while the shared conversion stage reduces overall system complexity. This approach allows multi-path access without requiring separate converter units for each path.
Solution Approach 2:
The converter structure segments the input paths while integrating the conversion function. Multiple independent DC inputs are processed through separate input stages that feed into a common conversion mechanism, allowing independent control of each path while sharing the complex conversion and grid interface functions. This segmentation reduces device complexity compared to having fully independent converters for each path.
4Reliability
If a two-stage structure is implemented, then isolated DC conversion is achieved, but the number of components increases and heat dissipation becomes more difficult
Solution Approach 1:
The patent merges the isolation function with the conversion function in a single integrated stage. The single-stage converter achieves galvanic isolation between the photovoltaic side and grid side while eliminating the need for separate isolation components and intermediate energy storage elements. This integration maintains reliability through isolation capability while significantly reducing the total component count.
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 conversion efficiency by enabling independent MPPT control and reducing system complexity, facilitating heat dissipation and cost reduction through component sharing.
Implementation Method 1
transformers corresponding to the at least two DC-side conversion circuits; AC-sides of the DC-side conversion circuits are respectively connected to primary windings of the corresponding transformers; secondary windings of the transformers are connected in parallel to a first side of the AC-side conversion circuit
Data Source
AI summary
A single-stage multi-path direct current access converter and a control method thereof are provided. The single-stage multi-path direct current access converter includes an AC-side conversion circuit; at least two DC-side conversion circuits; and transformers corresponding to the at least two DC-side conversion circuits. AC sides of the at least two DC-side conversion circuits are respectively connected to primary windings of the corresponding transformers; secondary windings of the transformers are connected in parallel to a first side of the AC-side conversion circuit; each of the at least two DC-side conversion circuits is configured to invert DC power received by the DC-side conversion circuit, or to rectify AC power received by the DC-side conversion circuit; and the AC-side conversion circuit is configured to perform AC frequency conversion.