Master-Slave PV Converter Control for N-Wire Current Limiting

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Solution Overview

Problem

The increasing voltage levels in photovoltaic systems pose challenges for the withstand voltage of power devices, particularly inverters, necessitating improved control of current through the N wire to comply with safety standards and minimize power consumption.

Innovation Solution

A photovoltaic system incorporating a master DC/DC converter, a slave DC/DC converter, a master DC/AC converter, and a slave DC/AC converter, with the master DC/AC converter controlling the slave DC/AC converter to manage current through the N wire by adjusting input voltages and current instruction values, ensuring the current remains below a preset level.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the voltage level of the photovoltaic system is increased, then the power generation capacity is improved, but the withstand voltage requirement of power devices becomes more difficult to meet

Engineering Contradiction:

Improvepower generation capacityVSAvoidwithstand voltage requirement

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent divides the single inverter system into a master inverter and a slave inverter, each handling a portion of the total power. The master inverter processes the positive direct current bus, while the slave inverter processes the negative direct current bus, allowing each device to operate within its voltage withstand capacity while collectively handling higher system voltages.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an N wire as an intermediary element that connects the master and slave inverters. This N wire serves as a common reference that allows the two inverters to operate in parallel without requiring each device to withstand the full system voltage, effectively mediating the voltage distribution across the system.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If the current through the N wire is increased, then the power consumption of the N wire increases, but the voltage level enhancement is achieved

Engineering Contradiction:

Improvevoltage levelVSAvoidpower consumption of N wire

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The master inverter detects the voltage between the positive direct current bus and the N wire, then sends a current instruction value to the slave inverter based on this detection. The slave inverter adjusts its output current according to this instruction, creating a feedback control mechanism that minimizes the current through the N wire while maintaining the enhanced voltage level.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent dynamically adjusts the output current parameter of the slave inverter based on the detected voltage conditions and the current instruction value from the master inverter. This parameter adjustment ensures that the N wire current is minimized, reducing power consumption while maintaining the desired voltage level enhancement.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12597845B2Photovoltaic system having master and slave converters and control method of the same

Publication Date: 2026.04.07 SUNGROW POWER SUPPLY CO LTD

AI summary

A photovoltaic system and a control method. The photovoltaic system includes a master DC/DC converter; a slave DC/DC converter; a master DC/AC converter; and a slave DC/AC converter. The master DC/AC converter is configured to send a current instruction value and an input voltage of the master DC/AC converter to the slave DC/AC converter; and the slave DC/AC converter is configured to control an output current, based on an input voltage of the slave DC/AC converter, the current instruction value, and the input voltage of the master DC/AC converter, so that a current through the N wire is less than a preset current.