Phase-Locked Loop for Utility Parallel-Connection Synchrony
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional utility electricity parallel-connection systems face issues with oscillations and phase delays due to voltage distortion and frequency variations, making it difficult for inverter circuits to achieve precise synchrony with utility electricity.
Innovation Solution
A phase-locked loop method that generates conversion signals using sine and cosine functions, calculates error values, and adjusts frequencies to produce synchronous signals, effectively eliminating distortion and frequency variations through a proportional integrator and angle signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low-pass filter is used to improve waveform quality, then signal oscillation is reduced, but phase delay occurs making the system inapplicable for large voltage frequency variations
Solution Approach 1:
The patent implements a phase-locked loop with feedback mechanism where the detected utility electricity voltage is continuously compared with the inverter output voltage. The phase difference and frequency difference are detected and fed back to adjust the inverter output, enabling the system to automatically track and adapt to utility electricity frequency variations without fixed phase delay constraints
Solution Approach 2:
The system transitions from a static filtering approach to a dynamic phase-locked loop control system. The low-pass filter is replaced with active feedback control that continuously adjusts the inverter output frequency and phase to match the utility electricity, enabling real-time adaptation to frequency variations while maintaining signal stability
2Reliability
If magnetic hysteresis comparator is used to alleviate signal oscillation, then zero-crossing detection stability is improved, but phase delay occurs reducing response speed
Solution Approach 1:
The patent uses feedback control to detect phase difference between utility electricity voltage and inverter output voltage. Instead of relying on hysteresis comparator with inherent phase delay, the system continuously measures the actual phase difference and actively compensates for it, achieving both stability and fast response
Solution Approach 2:
The mechanical hysteresis comparator approach is replaced with an electronic feedback control system. The phase-locked loop uses digital or analog feedback mechanisms to detect and correct phase differences, eliminating the inherent phase delay of hysteresis comparators while maintaining detection stability
3Productivity
If conventional digital control is used for inverter circuit, then power flow control is achieved, but oscillation occurs due to utility electricity voltage distortion
Solution Approach 1:
The patent implements a phase-locked loop feedback system that continuously detects voltage distortion and frequency variations in utility electricity. The feedback mechanism adjusts the inverter output in real-time to compensate for distortions, maintaining stable power flow control while eliminating oscillations caused by utility voltage variations
Solution Approach 2:
The phase-locked loop acts as an intermediary between the utility electricity and the inverter circuit. It detects disturbances in the utility voltage and generates corrective control signals that mediate the power flow, preventing oscillations from propagating through the system while maintaining effective power control
Data Source
AI summary
A phase-locked loop method for use in utility electricity parallel-connection system is introduced. The phase-locked loop method comprises a conversion signal generating step, an error calculating step, a frequency correction signal obtaining step, an angle signal obtaining step, and a synchronous signal generating step to not only calculate an error value by detecting a utility electricity voltage, but also reduce or return-to-zero the error value by proportional integral adjustment. With the steps, the phase-locked loop method achieves synchrony precisely by eliminating input utility electricity voltage distortion and frequency variation. Furthermore, the phase-locked loop method advantageously features quick response and a wide frequency range and therefore is effective in tracking power generation facilities, such as a diesel generator, and expanding inverters.