Modular Inverter Harmonic Cancellation via Transformer Coupling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing inverter systems for photovoltaic power conversion lack modularity and efficiency, particularly in accommodating additional PV strings and inverter modules, which limits design flexibility and increases costs as they strive to achieve a pure sinusoidal output.
Innovation Solution
A modular multi-pulse inverter system that operates at line frequency, featuring a configuration with multiple inverter modules and transformers to cancel harmonic components, allowing easy addition of PV strings and inverter modules, thereby optimizing power efficiency and design flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional inverter systems use cascaded electronic switching devices to generate stepped waveforms, then the inverter can convert DC to AC power, but the system becomes more expensive as the output voltage approaches a pure sinusoid
Solution Approach 1:
The patent divides the inverter system into multiple independent inverter modules (first inverter, second inverter, etc.), each generating voltage signals with predetermined harmonic components. These modules operate independently and can be easily added or removed, avoiding the complexity of a single large inverter while maintaining good sinusoidal output quality through harmonic cancellation.
Solution Approach 2:
The patent converts the harmful harmonic components generated by each inverter module into a beneficial effect by using transformer coupling with specific winding configurations. The harmonics from multiple inverters are combined through the transformers to cancel each other out, while the fundamental frequency components add constructively to produce a clean sinusoidal output.
2Power
If inverter systems are designed for medium power applications with fixed configurations, then the system can achieve adequate power output, but the system lacks flexibility to accommodate additional PV strings and modules
Solution Approach 1:
The patent implements a modular architecture where the inverter system is divided into independent inverter modules that can be individually added or removed. Each module includes its own inverter and transformer, allowing the system to be easily expanded by simply adding more modules in parallel without redesigning the entire system.
Solution Approach 2:
The patent designs universal inverter modules that can handle multiple functions and configurations. Each module is capable of operating independently and can be connected to different numbers of PV strings, allowing the same module design to serve various power levels and application requirements.
3Reliability
If inverter systems use traditional topologies with decoupling capacitors, then the system can handle voltage variations, but the capacitors must be relatively large and the system lacks modularity
Solution Approach 1:
The patent eliminates the need for large decoupling capacitors by segmenting the system into multiple inverter modules with transformer coupling. Each module maintains voltage stability independently through its own transformer, and the transformer coupling provides natural decoupling between modules, removing the requirement for large bulk capacitors while maintaining system reliability.
Solution Approach 2:
The patent introduces transformers as intermediary elements between inverter modules and the grid. These transformers serve as mediators that provide electrical isolation, voltage transformation, and harmonic filtering, replacing the need for large decoupling capacitors while maintaining voltage stability and improving system modularity.
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 improved power efficiency and cost-effectiveness by canceling harmonic distortions and allowing flexible system expansion, accommodating various power requirements with enhanced modularity and simplicity.
Implementation Method 1
at least one transformer module includes at least one first primary winding coupled to the first inverter and at least one second primary winding coupled to the second inverter. The transformer module further includes at least one secondary winding coupled to the at least one first primary winding, the at least one second primary winding and the AC power grid
Data Source
AI summary
A system connected to an AC power grid having an AC phase signal includes an inverter module including a first inverter coupled to a DC voltage, actuated based on the AC phase signal. The first inverter provides a first voltage signal having predetermined harmonic components. A second inverter includes second switch elements coupled to the DC voltage and actuated by a second set of control signals phase delayed with respect to the first control signals. A transformer module has first and second primary windings coupled to the first and second inverters. The transformer module further includes a secondary winding coupled to first primary winding, the second primary winding, and the AC power grid. The secondary winding is configured to provide a secondary output voltage to the AC power grid by combining the first voltage signal and the second voltage signal such that the predetermined harmonic components are substantially cancelled.