Parallel Inverter Droop Control With PI Feedback for Power Sharing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional droop control methods for parallel inverters face challenges with voltage steady-state error, power allocation error, and slow response speed due to the use of proportional droop control, which limits their effectiveness in achieving reliable and efficient power distribution.
Innovation Solution
The proposed droop control method incorporates proportional integral control on RMS voltage and power error values, introduces an average active power loop, and eliminates the RMS loop to improve response speed and reduce steady-state power allocation errors, using a droop coefficient and unit sine function to calculate an alternating current voltage reference value for duty cycle control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If proportional droop control is used, then the control structure is simple, but voltage steady-state error and steady-state power allocation error occur
Solution Approach 1:
The patent changes the control parameter from simple proportional control to proportional-integral (PI) control, introducing an integral term that accumulates voltage errors over time. This parameter change eliminates steady-state voltage errors while maintaining reasonable control structure complexity through the use of standard PI controller blocks.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the output voltage and power of each inverter, comparing them with reference values, and using the error signals through PI controllers to adjust the duty cycle. This closed-loop feedback mechanism eliminates steady-state errors that open-loop proportional control cannot correct.
2Device complexity
If proportional droop control is used, then the control structure is simple, but steady-state power allocation error occurs
Solution Approach 1:
The patent implements feedback control by continuously monitoring the output voltage and power of each inverter, comparing them with reference values, and using the error signals through PI controllers to adjust the duty cycle. This closed-loop feedback mechanism eliminates steady-state errors that open-loop proportional control cannot correct.
Solution Approach 2:
The patent changes the control parameter from simple proportional control to proportional-integral (PI) control, introducing an integral term that accumulates power errors over time. This parameter change eliminates steady-state power allocation errors while maintaining reasonable control structure complexity through the use of standard PI controller blocks.
3Device complexity
If conventional droop control method is used, then the control method is simple, but response speed is slow
Solution Approach 1:
The patent applies preliminary action by using the PI controller to anticipate and correct errors before they become significant. The integral term continuously accumulates past errors and proactively adjusts the control output, enabling the system to respond more quickly to disturbances and reach steady-state faster compared to reactive proportional control.
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
Provided is a droop control method for parallel inverters, including, for each inverter: performing proportional integral control on an RMS voltage error value and a power error value to obtain an integral error value; obtaining an RMS voltage target value based on the integral error value and a droop value of an output power of a corresponding inverter; converting the RMS voltage target value to an alternating current value to obtain an alternating current voltage reference value; and obtaining, based on the alternating current voltage reference value, a duty cycle for controlling an output of the corresponding inverter.