Parallel Inverter Power Control via Split Command Values
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power converter systems face challenges in accurately supplying power to loads due to output errors from individual inverters, making it difficult to increase the accuracy of power delivery.
Innovation Solution
A power converter system with inverters connected in parallel, where a controller determines two power command values – one lower and one higher than a proportional division value – to control the output powers of the inverters, ensuring the total output power is closest to the required value, thereby improving accuracy and preventing rapid power fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If power converters are controlled using conventional methods (random selection, proportional division, or simple maximization), then the control system remains simple, but the accuracy of power supplied to the load deteriorates due to output errors from each inverter
Solution Approach 1:
The control system segments the power command determination into two distinct parts: a first power command value (lower than proportional division) and a second power command value (higher than proportional division). This segmentation allows the system to select from multiple discrete power levels, thereby improving the accuracy of total power supply by better compensating for individual inverter output errors.
Solution Approach 2:
The control system dynamically adjusts the power command values based on the number of operating inverters and their individual characteristics. By determining the first and second power command values according to actual operating conditions rather than using fixed proportional division, the system adapts to variations in inverter performance, thereby improving power supply accuracy.
2Productivity
If the number of operating inverters is controlled to maximize AC output power, then productivity is improved, but the accuracy of power supply deteriorates due to inability to precisely match required power value
Solution Approach 1:
The control system changes the power command parameters by establishing two distinct power command values (first and second) rather than using a single proportional division value. This parameter change enables the system to achieve more precise control over the total output power, allowing it to closely match the required power value while maintaining high productivity.
Solution Approach 2:
The control system uses feedback from the actual operating state of inverters to determine appropriate power command values. By considering the number of operating inverters and their individual output characteristics, the system adjusts the first and second power command values to achieve both high productivity and high accuracy in power supply.
3Device complexity
If inverters are controlled to output power at proportional division values, then device complexity remains low, but rapid power fluctuations occur that exceed permissible output change rates
Solution Approach 1:
The control system performs preliminary determination of the first and second power command values before actual power adjustment. By pre-calculating appropriate power command levels based on the number of operating inverters and their characteristics, the system can smoothly transition between power levels without causing rapid fluctuations that would exceed permissible output change rates.
Solution Approach 2:
The control system dynamically determines the first and second power command values based on actual operating conditions, creating a flexible control mechanism that adapts to system state changes. This dynamic approach allows the system to maintain stability by adjusting power commands in a controlled manner rather than making abrupt changes, thereby preventing excessive power fluctuations.
Data Source
Figure 1~2
Figure 3~4
AI summary
A power conversion system (10) includes inverters (INV1 to INVn), AC sides of the inverters (INV1 to INVn) being connected in parallel, and a controller (1) which controls the inverters (INV1 to INVn) through division into a set value (CL) and a set value (CH) which are respectively lower and higher than a value obtained by dividing a required power value (DM) required as total output power (PQt) of the inverters (INV1 to INVn) by the number n.