Medium-high Voltage PV System Grid Connection

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Solution Overview

Problem

Conventional medium-high voltage photovoltaic (PV) power generation systems have low efficiency due to the use of power booster transformers and high-frequency isolated DC/DC converters, which result in maximum efficiency of less than 98% and are bulky, making it difficult to improve further.

Innovation Solution

A medium-high voltage PV power generation system that uses a three-phase filter and phase circuits connected in a star or delta manner, with bridge arms and cascade modules, and insulators to elevate PV strings to a high voltage level, eliminating the need for power booster transformers and high-frequency isolated DC/DC converters, thereby improving efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If power booster transformer and high-frequency isolated DC/DC converter are used for two-stage transformation, then medium-high voltage grid connection is achieved, but system efficiency is reduced to below 98% and system becomes bulky

Engineering Contradiction:

Improvesystem efficiencyVSAvoidsystem structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent extracts and removes the power booster transformer and high-frequency isolated DC/DC converter from the system. By directly connecting the PV string output to the grid-connected inverter, the two-stage transformation components are eliminated, reducing energy losses and simplifying the system structure while achieving medium-high voltage grid connection through a single-stage transformation approach

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent merges the functions of multiple components into a streamlined configuration. The PV string is directly connected to the grid-connected inverter, combining the voltage transformation and grid connection functions into a more integrated system that eliminates the need for separate DC/DC conversion and transformer stages, thereby improving efficiency and reducing complexity

Inventive Principle:

Principle #5Merging (Combining)

2Loss of energy

If power booster transformer is used, then voltage matching for medium-high voltage grid is achieved, but system becomes bulky and efficiency improvement is difficult

Engineering Contradiction:

Improvesystem efficiencyVSAvoidsystem volume

Core Design Contradiction:

Loss of energyVSVolume of stationary object

Solution Approach 1:

The power booster transformer is extracted and removed from the system. The patent achieves voltage matching for medium-high voltage grid connection through the grid-connected inverter alone, eliminating the transformer and associated bulky infrastructure while improving system efficiency by removing the source of no-load losses

Inventive Principle:

Principle #2Taking out (Extraction)

3Loss of energy

If conventional two-stage transformation with DC/DC converter is used, then voltage conversion is achieved, but efficiency remains low due to wide voltage gain range requirements

Engineering Contradiction:

ImproveDC/DC converter efficiencyVSAvoidvoltage gain range

Core Design Contradiction:

Loss of energyVSAdaptability or versatility

Solution Approach 1:

The high-frequency isolated DC/DC converter is extracted and removed from the system. The patent achieves direct voltage conversion from the PV string to the grid level through the grid-connected inverter, eliminating the need for intermediate DC/DC conversion and its associated efficiency losses from wide voltage gain range requirements

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The voltage conversion function previously performed by the DC/DC converter is merged into the grid-connected inverter's operation. This integration eliminates the need for separate voltage conversion stages and their associated efficiency losses

Inventive Principle:

Principle #5Merging (Combining)

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 system achieves an efficiency improvement from 98% to 99% by directly connecting the PV strings to a 10 kV power grid without additional transformers, reducing no-load losses and leakage currents, and allowing for maximum power point tracking control, enhancing power generation and reducing maintenance costs.

Implementation Method 1

The PV string is insulated from a ground via the insulator. A height from the PV panel to the ground is greater than a preset height. The insulator is of a medium-high voltage withstanding level.

Methodology Applied

Scientific EffectElectrical insulation: Electrostatics

Implementation Method 2

a three-phase filter and three phase circuits connected in a star manner or a delta manner via the three-phase filter

Methodology Applied

Scientific EffectElectromagnetic filtering: Filter (electronic)

Implementation Method 3

The PV string includes multiple PV panels

Methodology Applied

Scientific EffectPhotovoltaic effect: Photovoltaic Effect

Data Source

PatentUS10938208B2Medium-high voltage photovoltaic power generation system

Publication Date: 2021.03.02 SUNGROW POWER SUPPLY CO LTD

AI summary

A medium-high voltage photovoltaic (PV) power generation system is provided. A PV string of the system is insulated from the ground via an insulator of a medium-high voltage withstanding level, so that the PV string is applicable under a high voltage level. The PV strings are connected to cascade modules. An output voltage of series-connected cascade modules is grid-connected to a 10 kV power grid through a three-phase filter, without a power booster transformer or a high-frequency isolated DC/DC converter in a conventional power station, thereby improving the system efficiency.