Inverter Architecture for Reverse Current Protection in PV Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing photovoltaic systems face complexity and cost-intensiveness in preventing reverse currents and disconnecting from the grid when insufficient solar radiation is present, often requiring multiple AC low-voltage contactors and monitoring devices.
Innovation Solution
Directly connecting the medium-voltage transformer to the inverter's AC low-voltage output and maintaining connection to the photovoltaic generator on the DC side, eliminating the need for AC low-voltage contactors and allowing reverse currents to flow, with a coupling contactor used to disconnect from the grid if specified parameters are not met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AC low-voltage contactors are used to disconnect inverters from the grid when solar radiation is insufficient, then reverse current protection is achieved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and removes the AC low-voltage contactor from the system by redesigning the inverter's internal architecture. The inverter bridge is reconfigured to eliminate the need for external contactors, directly integrating the protection function into the inverter's switching mechanism. This extraction principle reduces device complexity while maintaining reverse current protection reliability.
Solution Approach 2:
The patent merges the reverse current protection function with the inverter's existing switching elements. By combining the protection function with the inverter bridge components, the system eliminates separate contactors and monitoring devices, thereby reducing overall system complexity while achieving the same protective effect.
2Reliability
If AC low-voltage contactors and monitoring devices are installed to disconnect inverters during grid feed-in parameter violations, then grid protection is improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent extracts unnecessary external monitoring devices and contactors by integrating all protection functions directly into the inverter unit. This eliminates the need for separate components, reducing both manufacturing cost and device complexity while maintaining grid protection reliability.
Solution Approach 2:
The inverter is designed with multi-functional capabilities, where the same switching elements perform both power conversion and protection functions. This universality eliminates the need for dedicated monitoring devices and contactors, reducing manufacturing costs while maintaining comprehensive grid protection.
3Reliability
If multiple AC low-voltage contactors are used for each inverter, then inverter disconnection from medium-voltage transformer is improved, but device complexity and cost-intensiveness worsen
Solution Approach 1:
The patent extracts and eliminates the AC low-voltage contactor from the system by redesigning the inverter architecture. The inverter bridge is reconfigured to provide direct disconnection capability without requiring external contactors, thereby reducing device complexity while maintaining reliable inverter disconnection from the medium-voltage transformer.
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 approach simplifies the system by reducing the need for multiple AC low-voltage contactors and DC switching elements, lowering costs and complexity while ensuring effective reverse current protection without damaging photovoltaic modules.
Implementation Method 1
a photovoltaic system with a photovoltaic generator (10) having a plurality of photovoltaic modules (11)
Implementation Method 2
at least one medium-voltage transformer (31) for feeding the electrical power into a medium-voltage grid (41)
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a method for operating a photovoltaic system for feeding into a medium-voltage network (41). The photovoltaic system has a photovoltaic generator (10) having a plurality of photovoltaic modules (11), at least one inverter (21), and at least one medium-voltage transformer (31). The medium-voltage transformer (31) is connected directly to an alternating-current low-voltage output (24) of the inverter (21) on the primary side. The inverter (21) is connected to the photovoltaic generator (10) by means of a direct-current input (22). The inverter (21) permits back currents from the alternating-current low-voltage output (24) to the direct-current input (22) due to the design. The method is characterized in that, if the generation of electrical power by the photovoltaic modules (11) is not sufficient for feed-in, the inverter (21) remains connected to the medium-voltage network (41) on the alternating-current side by means of the medium-voltage transformer (31) and remains connected to the photovoltaic generator (10) on the direct-current side. The invention further relates to a photovoltaic system designed to carry out the method, comprising a photovoltaic generator (10), within which a number of photovoltaic modules (11) is connected in series, said number being so large that a forward voltage of the photovoltaic modules (11) connected in series is greater than a voltage arising at the direct-current input (22) due to the back currents.