Inverter Carrier Phase Synchronization via Harmonic Feedback
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Solution Overview
Problem
In distributed power supply systems, the lack of carrier synchronization between parallel inverters leads to harmonic currents, compromising the stability and quality of electric energy output, as existing methods based on zero sequence currents are ineffective in reducing harmonic current impacts.
Innovation Solution
An apparatus and method that adjust the phase of an input carrier based on trends in harmonic current amplitudes and phases to minimize harmonic current output, using a modulation unit, current processing unit, and control unit to generate switch signals and control the inverter, thereby improving stability without relying on zero sequence current synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If parallel inverters are connected without communications cable in a distributed power supply system, then field cabling complexity is reduced and ease of operation is improved, but carrier synchronization becomes difficult to implement and system stability deteriorates
Solution Approach 1:
The patent implements feedback control by detecting harmonic current amplitudes and using this information to dynamically adjust carrier phases. The control unit continuously monitors harmonic current levels and modifies carrier phase shifts accordingly, creating a closed-loop system that automatically maintains synchronization without requiring communication cables between inverters.
Solution Approach 2:
The patent changes the parameter of carrier phase shift dynamically based on harmonic current conditions. By adjusting the phase shift parameter of carriers in parallel inverters according to detected harmonic current amplitudes, the system adapts to varying operating conditions and maintains stability without fixed communication infrastructure.
2Device complexity
If carrier synchronization is not implemented in parallel inverters, then device complexity is reduced, but harmonic current increases and manufacturing precision deteriorates
Solution Approach 1:
The system performs self-service by using its own output harmonic current as the feedback signal for synchronization control. Each inverter detects the harmonic current and autonomously adjusts its carrier phase based on this self-generated feedback, eliminating the need for external communication systems while maintaining electric energy quality.
3Reliability
If zero sequence current-based carrier synchronization is used in distributed power supply systems, then carrier synchronization can be achieved, but it is ineffective in reducing harmonic current impact and system stability deteriorates
Solution Approach 1:
The patent inverts the traditional synchronization approach by using harmonic current (the harmful effect) as the control signal instead of zero sequence current. Rather than trying to eliminate harmonic current after generation, the system uses harmonic current amplitude directly to adjust carrier phases, turning the harmful feedback into a useful control mechanism that simultaneously achieves synchronization and reduces harmonic impact.
Data Source
AI summary
This application discloses an apparatus, an inverter system, and a method for synchronizing carriers. The apparatus includes a modulation unit, a current processing unit, and a control unit. The control unit can adjust, based on a change trend between an amplitude of a first harmonic current and an amplitude of a second harmonic current and a change trend between a phase of a first carrier and a phase of a second carrier, a phase of an input carrier input into the modulation unit, to decrease an amplitude of a harmonic current output by an inverter and improve stability of a distributed power supply system. Further, a prior-art problem that impact of a harmonic current on a power supply system cannot be reduced by synchronizing carriers in a process of synchronizing carriers based on a zero sequence current is avoided, thereby improving the stability of the distributed power supply system.