PV Module Voltage Limiting for Higher Series String Count

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Solution Overview

Problem

Conventional photovoltaic power generation systems face limitations in the number of components that can be connected in series due to voltage constraints, leading to low direct voltage utilization and inefficient PV-to-inverter conversion ratios.

Innovation Solution

A method and system for controlling photovoltaic cells to operate in a voltage-limited mode, using pulse width modulation (PWM) or complete-short modes, to reduce output voltage and increase the number of series connections while maintaining voltage within safe limits, and resuming normal output when necessary.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If more photovoltaic modules are connected in series to increase system power, then system power increases, but the maximum voltage limit of 1500V restricts the number of modules that can be connected

Engineering Contradiction:

Improvesystem powerVSAvoidvoltage limitation constraint

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The photovoltaic module is divided into multiple independently controllable photovoltaic cell strings. Each string can be controlled to operate in different modes (normal mode or voltage-limited mode) through separate switching circuits, allowing flexible voltage management while maintaining overall system power output.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically adjusts the operating mode of individual photovoltaic cell strings based on real-time voltage conditions. When the DC bus voltage exceeds the threshold, specific strings are switched to voltage-limited mode; when voltage is sufficient, strings resume normal mode to maximize power generation.

Inventive Principle:

Principle #15Dynamics

2Productivity

If the direct voltage of the system is increased to improve PV-to-inverter ratio, then conversion efficiency improves, but the voltage exceeds the maximum limit of 1500V

Engineering Contradiction:

ImprovePV-to-inverter ratioVSAvoidovervoltage condition

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

Different parts of the photovoltaic system (individual cell strings) are assigned different operating characteristics. Some strings operate in normal mode to maintain high voltage for good PV-to-inverter ratio, while others operate in voltage-limited mode to prevent overvoltage, creating local quality differences that resolve the global contradiction.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The operating parameters of photovoltaic cell strings are dynamically changed between normal mode and voltage-limited mode. This parameter switching allows the system to adapt voltage levels according to grid conditions, maintaining optimal PV-to-inverter ratio while preventing harmful overvoltage conditions.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If photovoltaic cells are controlled to operate in voltage-limited mode to reduce output voltage, then voltage safety is ensured, but power output is reduced

Engineering Contradiction:

Improvevoltage safetyVSAvoidpower output

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

Instead of limiting the voltage of the entire photovoltaic system, only the necessary portion (specific cell strings) is controlled to operate in voltage-limited mode. This partial action maintains voltage safety while minimizing the impact on overall power output, as other strings continue to operate at full capacity.

Inventive Principle:

Principle #16Partial or excessive action

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 approach allows for increased series connections, reducing system costs and improving direct voltage utilization and PV-to-inverter conversion efficiency.

Implementation Method 1

A photovoltaic power generation system mainly includes a photovoltaic module and an inverter

Methodology Applied

Scientific EffectPhotovoltaic effect: Photovoltaic Effect

Implementation Method 2

The direct voltage is converted into an alternate voltage by the inverter

Methodology Applied

Scientific EffectElectromagnetic conversion: Electromagnetic Induction

Data Source

PatentUS12081167B2Method for limiting voltage of module, and apparatus and system for applying the same

Publication Date: 2024.09.03 SUNGROW POWER SUPPLY CO LTD

AI summary

A method for component voltage limitation, and an apparatus and a system for applying the same. At least one photovoltaic cell in a photovoltaic-cell string is controlled to operate in a voltage-limited mode, in response to receiving an instruction for enabling voltage limitation. Thereby, the voltage of the photovoltaic-cell string is reduced. A quantity of photovoltaic modules connected in series can be increased, while a highest voltage of the system is guaranteed not to exceed a corresponding requirement. A system cost is reduced. The photovoltaic cell operating in the voltage-limited mode is controlled to resume a normal output, in response to receiving the instruction for suspending voltage limitation. The output voltage of the photovoltaic-cell string is increased. Thereby, a rate of utilization on a direct voltage, and a PVIR of DC/AC are improved for the photovoltaic system.