High-Impedance Master Serial Communication for PV Inverter Interference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In photovoltaic systems, the presence of an inverter as a low-impedance interference source complicates communication by superimposing its output signals with the voltage signals from PV modules, making it difficult to distinguish interference from useful signals, especially when trying to communicate from the PV module to the master, as existing filtering methods are ineffective in this frequency range.
Innovation Solution
A serial communication system is designed with a high-impedance master unit, low-impedance slave units (photovoltaic modules), and a low-impedance inverter connected in series, where the master unit acts as a current source and the slave units as voltage sources, utilizing synchronization units to separate interference signals by synchronizing communication using alternating and direct current signals, enabling both half-duplex and full-duplex operations with high interference suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the inverter operates as a voltage source with low impedance in the communication line, then power conversion function is achieved, but the inverter's output signals superimpose with PV module voltage signals making communication difficult or impossible
Solution Approach 1:
The patent changes the impedance parameter of the master unit from low (conventional) to high impedance. This parameter change allows the master unit to detect voltage signals from slave units even when the inverter is actively switching, because the high impedance minimizes loading effects and allows the detection of small voltage variations superimposed on the larger inverter signals.
Solution Approach 2:
The patent introduces a synchronization unit as an intermediary component that coordinates the timing between master and slave units. This synchronization mechanism allows the system to distinguish between inverter switching signals and communication signals by timing, enabling reliable communication despite the inverter's presence in the communication line.
2Measurement precision
If filtering methods are used to separate interference from useful signals, then signal separation may be achieved, but filtering is ineffective in the frequency range of inverter output signals
Solution Approach 1:
The synchronization unit acts as a temporal intermediary that coordinates signal transmission and detection timing. By synchronizing the slave units' communication transmissions with periods when the inverter is not switching, or by synchronizing detection with specific phases of the inverter cycle, the system can distinguish communication signals from inverter interference without requiring frequency filtering.
Solution Approach 2:
The system employs periodic synchronization signals and timed communication windows. The master unit and slave units operate in synchronized periodic cycles, allowing communication to occur in designated time slots that are coordinated with the inverter's switching pattern. This periodic timing structure enables signal separation through time-domain multiplexing rather than frequency filtering.
3Loss of information
If the master unit uses a current source for communication, then communication from master to slave is enabled, but the inverter's low impedance interferes with voltage signal detection from slaves to master
Solution Approach 1:
The patent changes the impedance parameter of the master unit to high impedance, which enables the master unit to detect voltage signals from slave units. This parameter change creates an asymmetry in the communication system where the master can both source current for outbound communication and detect voltage for inbound communication, depending on the operational mode.
Solution Approach 2:
The master unit dynamically switches between current sourcing mode (for master-to-slave communication) and voltage detection mode (for slave-to-master communication). The high impedance configuration enables the master to function as a voltage detector, and the system dynamically adapts the master's role based on the direction of communication needed at any given time.
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 configuration effectively separates interference from useful signals, allowing secure communication even in challenging conditions, with minimal hardware changes and cost, and supports a wide range of applications by enhancing the two-wire system with high interference suppression.
Implementation Method 1
the master unit and the at least one slave unit each have a synchronization unit which are set up to synchronize the communication between the slave unit and the master unit
Implementation Method 2
the current of the current source of the master unit is an alternating current and the voltage source of the slave unit is a direct current voltage source, so that the alternating current is superimposed on the direct current signal of the slave unit
Data Source
Figure 1
Figure 2~3
AI summary
Described is a serial communications system (2) comprising a high-impedance master unit (6), at least one low-impedance slave unit (4), and a low-impedance interference source (3). The master unit (6) and the at least one slave unit (4) are each equipped with a synchronizing unit (8) designed to synchronize communication between the slave unit (4) and the master unit (6).