Parallel Generator Synchronization Using a Virtual AC Reference
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Solution Overview
Problem
Existing methods for synchronizing synchronous electric machines are time-consuming and often require sequential operation, leading to prolonged power loss events and potential damage from unsynchronized generators.
Innovation Solution
The system performs synthetic synchronization by mechanically rotating the synchronous generator to a predetermined speed and using an external clock signal to generate a target output, allowing multiple generators to synchronize simultaneously and independently of bus voltage, frequency, or phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sequential synchronization of generators is performed, then each generator can be synchronized individually to the AC bus, but the total time for power restoration is prolonged
Solution Approach 1:
The system divides the synchronization task into independent segments by having each generator synchronize to a common virtual generator rather than requiring sequential connection to the AC bus. Each generator operates independently with its own breaker, allowing parallel synchronization without interfering with others.
Solution Approach 2:
Generators are synchronized to the virtual generator in advance before the AC bus is energized. The virtual generator serves as a preliminary reference that allows all generators to be prepared and ready simultaneously, eliminating the sequential wait time required in conventional methods.
2Productivity
If multiple generators are synchronized in parallel to a virtual generator, then power restoration time is reduced, but the system complexity increases
Solution Approach 1:
A virtual generator is created as a software-based copy of a physical generator's electrical characteristics (voltage, frequency, phase). This virtual reference allows multiple physical generators to synchronize without requiring complex interconnections or coordination between them, simplifying the overall control architecture.
Solution Approach 2:
The virtual generator acts as an intermediary reference that mediates between multiple physical generators and the AC bus. Instead of generators directly interacting with each other or the bus during synchronization, they all reference the virtual generator, which simplifies control logic and reduces system complexity.
3Adaptability or versatility
If generators synchronize independent of bus voltage, frequency, or phase, then synchronization can occur in parallel, but the requirement for precise voltage and frequency matching must be met
Solution Approach 1:
Each generator independently controls its own voltage and frequency to match the virtual generator's reference values. The excitation control system and prime mover control system of each generator automatically adjust parameters without requiring manual coordination or complex inter-generator communication, enabling parallel synchronization with precise matching.
Data Source
AI summary
The present disclosure contemplates a method for synchronizing a large number of generators on an AC bus by synchronizing each generator's output to a nominal output that is generated from a common external source. For example, each generator, using a high speed communication signal, can synchronize to a nominal output provided by a master generator, or centralized command module. In another example, each generator can generate its own nominal output referenced to a common external time signal, such as a global positioning system (GPS) signal, or other reference. By synchronizing independently of bus voltage and frequency, the generators are able to synchronize in parallel, instead of serially.