Photovoltaic system and carrier wave signal synchronization method
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Solution Overview
Problem
In photovoltaic systems, unsynchronized carrier wave signals between multiple inverters can lead to circulation currents, causing increased component losses, potential overcurrent protection issues, and false leakage current detection, which existing methods struggle to effectively suppress without modifying the system.
Innovation Solution
A photovoltaic system with a controller that synchronizes carrier wave signals by identifying the inverter with the largest output current and adjusting its carrier wave phase, implementing closed-loop suppression of circulation currents without requiring changes to the existing system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carrier wave signals of multiple inverters are not synchronized, then the system can operate independently without complex control, but circulation current is generated causing component losses and reliability issues
Solution Approach 1:
The patent implements closed-loop carrier wave signal synchronization by using the detected circulation current as feedback to adjust the phase of carrier wave signals. The controller continuously monitors the circulation current and dynamically adjusts the phase difference between carrier waves of different inverters to minimize or eliminate the circulation current, thereby improving system reliability through active feedback control.
2Loss of energy
If hardware cables are added to connect positive and negative buses in parallel, then bus voltages become consistent reducing circulation current, but system complexity and cost increase
Solution Approach 1:
The patent changes the phase parameter of carrier wave signals to achieve synchronization. By adjusting the phase difference between carrier waves of different inverters, the system eliminates circulation current and reduces component losses without adding any physical hardware connections. This parameter-based approach avoids the complexity of additional hardware while achieving the same energy loss reduction.
3Ease of operation
If open-loop control is used to adjust DC bus voltage, then implementation is simple, but large sampling errors still result in large circulation currents
Solution Approach 1:
The patent employs closed-loop feedback control where the circulation current is detected and used as feedback to adjust the carrier wave phase. This feedback mechanism compensates for sampling errors in DC bus voltage by directly responding to the actual circulation current condition, thereby maintaining ease of operation while significantly improving measurement precision and reducing circulation current.
4Reliability
If carrier wave phase is adjusted based on DC bus voltage sampling, then synchronization is attempted, but large power grid voltage sampling errors lead to large carrier wave synchronization errors
Solution Approach 1:
The patent uses circulation current detection as feedback to directly adjust carrier wave phase, bypassing the unreliable DC bus voltage sampling path. By monitoring the actual circulation current caused by phase mismatch and using this as feedback for phase adjustment, the system achieves reliable carrier wave synchronization that is insensitive to power grid voltage sampling errors.
Data Source
AI summary
This application discloses a photovoltaic system and a carrier wave signal synchronization method. The photovoltaic system includes a plurality of inverters and a controller. Each inverter in the photovoltaic system inverts a direct current into an alternating current based on a received carrier wave signal, and transmits the alternating current to a power grid. The controller obtains first output currents of the plurality of inverters in an adjustment period, so that the controller can obtain first output current valid values of the plurality of inverters based on the first output currents of the plurality of inverters.