Active EMI Filter for PV Inverters Without Common Mode Chokes
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Solution Overview
Problem
Existing current compensation systems for solar generators are bulky and expensive due to the use of common mode chokes, which suffer from magnetic saturation in high power/high current systems, and require multiple connections for device quality inspection, leading to increased time and labor as well as cable damage.
Innovation Solution
An inverting system for solar generators utilizing an active EMI filter to reduce noise, which includes a noise sensing unit, an active circuit unit, a compensation unit, and a transmission unit, and a parameter measuring device that allows for automatic measurement of S parameters with a single connection, reducing the need for multiple connections and minimizing cable damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If common mode choke is used to reduce CM noise, then noise reduction performance is improved, but volume, area, and weight of the system increase
Solution Approach 1:
The patent changes the fundamental operating parameters of the EMI filter by transitioning from passive magnetic components (common mode chokes) to active electronic components. The active EMI filter uses operational amplifiers and feedback circuits to generate compensation currents that actively cancel noise, operating in the linear electronic domain rather than relying on magnetic saturation characteristics, thereby achieving noise reduction without the bulky magnetic components
Solution Approach 2:
The patent replaces the mechanical/magnetic system (common mode choke with magnetic core) with an active electronic system using operational amplifiers, feedback networks, and compensation circuits. This substitution eliminates the need for large magnetic components while achieving the same noise reduction function through electronic signal processing and active current compensation
2Object-affected harmful factors
If common mode choke is used to maintain noise reduction performance, then noise reduction performance is maintained, but price of the EMI filter increases
Solution Approach 1:
The patent changes the component type parameters from expensive high-power magnetic components to relatively inexpensive operational amplifiers and passive electronic components. The active EMI filter implementation uses standard electronic components that are mass-produced and cost-effective, eliminating the need for expensive custom magnetic components while maintaining noise reduction performance
Solution Approach 2:
The patent replaces expensive, bulky magnetic components with cheaper, compact electronic components. The active EMI filter uses operational amplifiers and standard electronic parts that are significantly less expensive than high-power common mode chokes, making the overall system more cost-effective while achieving the same functional performance
3Measurement precision
If multiple connections are made for S parameter measurement, then measurement completeness is improved, but time and labor consumption increase
Solution Approach 1:
The patent merges multiple separate measurement connections into a single integrated connection system. By using a multiplexer and switch matrix, the system can sequentially connect to multiple ports through one physical interface, allowing complete S parameter measurement to be achieved through a single connection while automatically switching between different measurement paths
Solution Approach 2:
The patent creates a universal measurement interface that can handle multiple measurement functions through a single connection. The multiplexer and control system enable one connection point to serve multiple measurement purposes by dynamically routing signals to different ports, making the measurement system multi-functional and eliminating the need for multiple dedicated connections
4Measurement precision
If multiple connections are made for S parameter measurement, then all S parameters can be measured, but cable damage rate increases
Solution Approach 1:
The patent combines multiple cable connection requirements into a single physical cable connection by implementing a multiplexer system. This single cable serves multiple measurement functions by electronically switching between different ports, thereby eliminating repeated plugging and unplugging of multiple cables and significantly reducing cable wear and damage
Solution Approach 2:
The patent creates a universal single cable interface that can perform multiple measurement functions. The single cable connection is equipped with a multiplexer and control system that enables it to access all necessary ports for complete S parameter measurement, making one cable replace multiple cables and improving overall system reliability by reducing connection points
Data Source
AI summary
Provided is a current compensation system for solar generators for compensating for noise using an active electromagnetic interference (EMI) filter. An inverting system for solar generators includes a solar inverter converting DC voltage to AC voltage, an EMI filter unit including an active EMI filter to reduce noise corresponding to the AC voltage, a power grid, and at least two or more through lines passing a second current from the power grid to the solar inverter and passing through the EMI filter unit, wherein the active EMI filter includes a noise sensing unit sensing a first current on the at least two or more through lines and generating an output signal corresponding to the first current, an active circuit unit amplifying the output signal to generate an amplified signal, a compensation unit generating a compensation current based on the amplified signal, and a transmission unit providing a path through which the compensation current flows to each of the at least two large current paths.