Grid-Connected Inverter Switchable AC Filter Modules
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Grid-connected inverters, especially photovoltaic inverters, face issues with excessive harmonic content and reduced conversion efficiency at low load factors due to low modulation ratios and increased no-load losses, failing to meet stringent harmonic standards and degrading energy quality.
Innovation Solution
A grid-connected inverter with a parallel AC output filter comprising multiple switchable filtering modules of varying power capacities, monitored and controlled by a real-time monitoring module and control circuit to select the appropriate filtering module based on output power, ensuring compliance with harmonic standards and optimizing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single AC output filter designed for rated output power is used, then harmonic distortion meets standards at rated power, but harmonic content exceeds standards and conversion efficiency decreases at low load factors
Solution Approach 1:
The AC output filter is segmented into multiple switchable filtering modules with different power capacities (e.g., first filtering module for high power, second filtering module for low power). Each module is independently switchable, allowing the system to select the appropriate module based on the current load factor, thereby maintaining harmonic distortion compliance across all operating conditions.
Solution Approach 2:
The filtering module configuration is made dynamic through real-time switching control based on monitored output power. The control circuit dynamically selects which filtering module to activate according to the current load factor, enabling the system to adapt its filtering characteristics to match the actual operating conditions and maintain optimal performance.
2Power
If a single AC output filter designed for rated output power is used, then filtering capability is sufficient at high power, but no-load loss increases proportionally at low output power
Solution Approach 1:
The filter is divided into multiple power-grade modules (e.g., high-power module and low-power module). When the inverter operates at low output power, only the corresponding low-power module is activated, significantly reducing the no-load loss compared to activating the full-rated-power filter. This segmentation allows the system to match filter capacity with actual power output.
Solution Approach 2:
The system changes the operating parameters of the filter by switching between different filtering modules with different power capacities. Based on the monitored output power, the control circuit selects the appropriate module, effectively changing the filter's power parameter to match the load, thereby minimizing no-load losses while maintaining sufficient filtering capability.
3Adaptability or versatility
If filtering module switching is implemented, then performance is optimized across load factors, but device complexity increases
Solution Approach 1:
While segmentation into multiple modules does increase structural complexity, it enables the system to achieve optimal filtering performance across all load factors. The segmented design allows each module to be specifically tuned for its power range, improving overall adaptability and harmonic distortion compliance.
Solution Approach 2:
The control circuit implements feedback control by continuously monitoring the output power and automatically switching between filtering modules based on the current load factor. This feedback mechanism simplifies the operation for the user while managing the complexity internally, as the system autonomously selects the appropriate filter configuration without requiring manual intervention.
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The present invention discloses a grid-connected inverter and a method for filtering AC output thereof. The grid-connected inverter comprises an AC output filter (40) which includes two or more switchable filtering modules (110, 120), power capacity of each filtering modules corresponding to a different output power of the grid-connected inverter; a monitoring module (50) which is used to perform realtime monitoring on voltage and current outputted by the grid-connected inverter; and a control circuit (60) which is used to calculate an output power grade of the grid-connected inverter according to the voltage and the current monitored by the monitoring module and control switching to the filtering module having a corresponding power capacity according to the power grade, the power grade being selected from a plurality of power grades which are divided according to power capacities of the filtering modules (110, 120). With the present invention, total harmonic distortion (THD) of the output current waveform of the grid-connected inverter can meet the requirements of relevant standards, and conversion efficiency of the grid-connected inverter in the case of a low load factor can be improved.