Grid-Forming Converter Phase Control Without Grid Voltage Sensors
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Solution Overview
Problem
Conventional grid-forming grid-connected converters require multiple voltage sensors to acquire and control AC capacitor voltage, leading to increased system volume, cost, and weight.
Innovation Solution
A grid-connected control method and system for a grid-forming converter that eliminates the need for grid-side voltage sensors by generating a stable phase of the grid voltage using a constructed phase, replacing the phase of the PLL, and performing coordinate transformation without the need for additional voltage sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage sensors are installed at the PCC to acquire grid voltage for phase-locked loop control, then the grid-forming converter can achieve stable phase locking and grid connection, but the system volume, cost, and weight increase due to requiring at least six AC voltage sensors
Solution Approach 1:
The patent extracts and removes the voltage sensors from the PCC side of the system. Instead of installing sensors at the grid connection point, the invention uses the existing capacitor voltage sensors to derive the necessary phase information through coordinate transformation and phase construction algorithms, eliminating the need for separate PCC voltage sensors while maintaining phase locking stability
Solution Approach 2:
The patent introduces an intermediary computational approach using coordinate transformation and phase construction algorithms. The capacitor voltage phase serves as an intermediary reference that is transformed and adjusted to generate the equivalent PCC voltage phase, allowing indirect acquisition of grid voltage information without direct sensing at the PCC
2Reliability
If voltage sensors are installed at the PCC to acquire grid voltage for phase-locked loop control, then the grid-forming converter can achieve stable phase locking and grid connection, but the system cost increases due to requiring at least six AC voltage sensors
Solution Approach 1:
The patent extracts and removes the voltage sensors from the PCC side of the system. Instead of installing sensors at the grid connection point, the invention uses the existing capacitor voltage sensors to derive the necessary phase information through coordinate transformation and phase construction algorithms, eliminating the need for separate PCC voltage sensors while maintaining phase locking stability
Solution Approach 2:
The patent makes the capacitor voltage sensors serve multiple functions. These sensors not only monitor the capacitor voltage for power control but also provide the phase reference for grid synchronization after coordinate transformation, eliminating the need for dedicated PCC voltage sensors and reducing overall system cost
3Reliability
If voltage sensors are installed at the PCC to acquire grid voltage for phase-locked loop control, then the grid-forming converter can achieve stable phase locking and grid connection, but the system structure becomes more complex
Solution Approach 1:
The patent merges the phase detection function into the existing control system. The coordinate transformation module and phase construction algorithm combine the capacitor voltage information with grid requirements to generate the equivalent PCC phase, eliminating separate PCC sensing hardware and simplifying the overall system structure while maintaining phase locking stability
Data Source
AI summary
The present disclosure pertains to the field of power electronics technologies, and provides a grid-connected control method and system for a grid-forming converter without a grid-side voltage sensor. The grid-connected control method includes: performing coordinate transformation on a phase of a three-phase capacitor voltage sampled by a phase-locked loop (PLL) to obtain a first phase; in response to control of a first pulse width modulation (PWM) pulse signal, introducing a reference phase, and performing negative feedback regulation on a difference between the reference phase and the first phase to obtain a second phase; and in response to control of a second PWM pulse signal, performing a modulo operation on a difference between the reference phase and the second phase to obtain a third phase, where the third phase is used to replace a phase of the PLL to perform coordinate transformation of a system.