Inverter Bus Balancing Control for Unbalanced Load Support

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Inverters used in photovoltaic power generation systems face high design costs and significant losses due to the complexity of balancing circuits required to manage unbalanced alternating current loads, especially when the local power grid is faulty.

Innovation Solution

The inverter system incorporates a two-level balancing circuit with a bus capacitor and a two-level switching transistor bridge arm, along with a filter inductor, to reduce voltage fluctuations and support unbalanced loads, while the control method adjusts current proportions to minimize the balancing circuit's output, thereby reducing design requirements and losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a balancing circuit is designed in the inverter to support unbalanced loads during grid faults, then the power supply capability and reliability are improved, but the device complexity and design costs increase

Engineering Contradiction:

Improvepower supply capabilityVSAvoidbalancing circuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The inverter circuit is designed to perform both inversion function and balancing function using the same hardware components. The inverter circuit can operate in multiple modes: normal grid-connected mode, off-grid mode with balanced load, and off-grid mode with unbalanced load, eliminating the need for dedicated balancing circuit hardware

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent combines the balancing circuit functionality with the inverter circuit by electrically connecting the inverter circuit between the positive and negative direct current buses. The control unit coordinates both circuits to work together, merging their functions into a unified system that reduces overall device complexity while maintaining reliability

Inventive Principle:

Principle #5Merging (Combining)

2Adaptability or versatility

If a balancing circuit is designed in the inverter to provide balancing capability for unbalanced loads, then the adaptability is improved, but the device complexity and design costs increase

Engineering Contradiction:

Improvebalancing capabilityVSAvoidbalancing circuit complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The control unit dynamically adjusts the operation mode based on real-time conditions. It determines whether to operate in grid-connected mode, off-grid mode with balanced load, or off-grid mode with unbalanced load by detecting grid status and load characteristics, allowing the system to adapt flexibly without complex hardware switches

Inventive Principle:

Principle #15Dynamics

3Reliability

If the balancing circuit works to provide balancing capability, then the reliability is improved, but the energy loss increases

Engineering Contradiction:

Improveoperation stabilityVSAvoidbalancing circuit loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The control unit periodically detects the working status of the power grid and load, and dynamically switches between different operation modes. The balancing function is activated only when needed (during off-grid operation with unbalanced loads), and deactivated during grid-connected operation, reducing unnecessary energy consumption while maintaining reliability when required

Inventive Principle:

Principle #19Periodic action

4Adaptability or versatility

If the inverter supports off-grid operation to independently support user loads, then the adaptability is improved, but the device complexity increases

Engineering Contradiction:

Improveoff-grid operating functionVSAvoidinverter circuit complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

Inventive Principle:

Principle #15Dynamics

Data Source

PatentEP4429090A1Inverter and inverter control method

Publication Date: 2024.09.11 HUAWEI DIGITAL POWER TECH CO LTD

Figure 1
Figure 2
Figure 3

AI summary

This application provides an inverter and an inverter control method. The inverter includes an inverter system and a controller. The inverter system includes an inverter circuit, positive and negative direct current buses, a bus capacitor, and a balancing circuit. The inverter is configured to: when a user connects to an unbalanced load, control the balancing circuit based on different magnitudes of voltage fluctuation generated by the unbalanced load for the bus capacitor, to implement a function of jointly sharing current fluctuation by the bus capacitor and the balancing circuit, and reduce design costs of the bus capacitor and the balancing circuit. Effect is significant and applicability is good.