PV Converter Modules With Partial-Power Isolation for MV Grid Links
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Solution Overview
Problem
Existing PV power plants face challenges in efficiently connecting to medium voltage (MV) and high voltage (HV) grids due to high power losses and inefficiencies in full-power converters, while requiring galvanic isolation and cost-effective solutions for maximum energy yield.
Innovation Solution
A photo-voltaic power conversion arrangement using partial-power DC/DC topology with a dedicated control strategy, incorporating Cascaded H-bridge and Modular-multilevel converter architectures, provides galvanic isolation and efficient energy yield by segregating DC-links and using high-frequency isolated DC/DC converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If full-power converters are used to connect PV power plants to MV/HV grids, then galvanic isolation is achieved, but power losses increase and efficiency decreases
Solution Approach 1:
The patent segments the power conversion function into two separate stages: a partial-power DC-DC converter for voltage matching and power optimization, and a full-power AC-AC converter for galvanic isolation and grid connection. This segmentation allows each converter to operate at optimal efficiency points, reducing overall power losses while maintaining galvanic isolation through the AC-AC stage.
Solution Approach 2:
The patent introduces an intermediate DC link between the partial-power DC-DC converter and the full-power AC-AC converter. This intermediate DC link serves as a mediator that decouples the DC voltage regulation function from the AC grid connection function, enabling efficient power transfer with reduced losses while maintaining galvanic isolation through the isolated AC-AC converter stage.
2Ease of manufacture
If full-power converters are used for PV grid connection, then galvanic isolation is provided, but cost-effectiveness decreases
Solution Approach 1:
The patent segments the power conversion system to use a partial-power DC-DC converter instead of a full-power converter. Since the DC-DC converter only needs to handle the difference between PV array power and DC link power requirements, its size and cost are significantly reduced compared to a full-power converter, while the galvanic isolation function is maintained by the AC-AC converter stage.
Solution Approach 2:
The patent changes the power handling parameter of the first converter from 100% (full-power) to a partial percentage (e.g., 30-70% depending on operating conditions). This parameter change allows the use of smaller, less expensive components in the DC-DC converter stage while maintaining system functionality and galvanic isolation through the AC-AC converter.
3Productivity
If conventional PV architectures are used, then simple structure is maintained, but maximum energy yield cannot be ensured
Solution Approach 1:
The patent implements dynamic Maximum Power Point Tracking (MPPT) control in the partial-power DC-DC converter stage, allowing the system to continuously adapt to changing PV array conditions (irradiance, temperature) and extract maximum available power. This dynamic control capability increases energy yield despite the added complexity of the two-stage converter architecture.
Solution Approach 2:
The patent incorporates feedback control mechanisms in both the DC-DC and AC-AC converter stages, with the DC-DC converter using feedback to maintain optimal operating point for maximum power extraction, and the AC-AC converter using feedback to synchronize with grid conditions. This feedback control ensures maximum energy yield while managing system complexity through coordinated control strategies.
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 higher overall efficiency, reduced power losses, and cost-effectiveness by optimizing power transfer and ensuring maximum power extraction from PV panels, even in long transmission lines, with flexible MPPT tracking and galvanic isolation.
Implementation Method 1
a plurality of photo-voltaic panels (110) of a photo-voltaic arrangement (101)
Implementation Method 2
a first DC-DC converter stage (130) configured to convert the first DC voltage (113) into an intermediate DC voltage (135)
Implementation Method 3
a second DC-DC converter stage (150) configured to provide the second DC voltage (123) based on a conversion of the first DC voltage (113) and the intermediate DC voltage (135), wherein the second DC-DC converter stage (150) is configured to galvanically isolate the first terminal (111) from the second terminal (121)
Data Source
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AI summary
A photo-voltaic (PV) power conversion arrangement for connecting a plurality of PV panels via a transmission line to a power grid network comprises a plurality of PV converter modules connected in series. Each PV converter module comprises a plurality of parallel connected DC-DC converter cells. Each DC-DC converter cell comprises: a first terminal for connecting the DC-DC converter cell to a respective PV panel associated with the DC- DC converter cell, the first terminal being configured to provide a first DC voltage; a second terminal for connecting the DC-DC converter cell to the transmission line, the second terminal being configured to provide a second DC voltage; a first DC-DC converter stage configured to convert the first DC voltage into an intermediate DC voltage, wherein a power converted by the first DC-DC converter stage corresponds to a partial power processing provided by the respective PV panel; and a second DC-DC converter stage configured to provide the second DC voltage based on a conversion of the first DC voltage and the intermediate DC voltage. The second DC-DC converter stage is configured to galvanically isolate the first terminal from the second terminal.