Grid-Forming Converter Coefficient Testing Using Frequency Injection
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Solution Overview
Problem
Existing methods for testing the inertia and damping coefficients of grid-forming converters are complex and difficult to implement, lacking clear definitions and requiring access to internal parameters, which hinders accurate assessment and compliance with power grid standards.
Innovation Solution
A method involving obtaining filter capacitor voltage, inverter-side and output-side currents, and output voltage, followed by frequency and phase signal output, PWM control, and active power calculation to determine inertia and damping coefficients without complex mathematical models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing methods use complex mathematical models and algorithms to test inertia and damping coefficients, then measurement precision can be achieved, but device complexity and difficulty of operation increase significantly
Solution Approach 1:
The patent segments the test system into independent functional modules: a signal injection module that injects frequency deviation signals, a data acquisition module that collects voltage and current signals, and a calculation module that computes coefficients using simplified formulas. This modular segmentation eliminates the need for complex mathematical models while maintaining measurement precision through standardized measurement procedures.
Solution Approach 2:
The patent replaces complex mathematical calculation systems with a simplified measurement system based on direct signal injection and standard formulas. Instead of using particle swarm optimization algorithms or second-order rotor angle transfer functions, the system directly measures frequency deviation signals and calculates coefficients using straightforward mathematical relationships, thereby reducing computational complexity.
2Measurement precision
If existing methods require access to internal parameters and complex mathematical models, then theoretical accuracy can be achieved, but ease of operation and implementation feasibility deteriorate
Solution Approach 1:
The patent enables the grid-forming converter to serve its own testing needs by implementing a self-contained test system that uses the converter's own output voltage and current signals. The system injects frequency deviation signals into the converter and measures the resulting responses, eliminating the need for external complex test equipment or access to internal parameters. The converter effectively tests itself using standardized measurement procedures.
3Reliability
If comprehensive signal processing and control are implemented to accurately measure coefficients, then measurement reliability improves, but loss of time and operational complexity increase
Solution Approach 1:
The patent employs periodic frequency deviation signals with specific frequencies (e.g., 0.1Hz, 0.2Hz, 0.5Hz) to stimulate the grid-forming converter. By using periodic signals with known characteristics, the system can reliably measure inertia and damping coefficients through standard frequency response analysis, reducing the need for extended testing periods or complex transient analysis while maintaining measurement reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables simple and effective testing of inertia and damping coefficients, facilitating accurate measurement and compliance with power grid standards, promoting stability and economic efficiency.
Implementation Method 1
outputting a pulse width modulation (PWM) control signal based on the phase output signal, the filter capacitor voltage, and the inverter-side current, to control turn-on time of a power semiconductor switch
Implementation Method 2
obtaining a filter capacitor voltage in a three-phase inductor-capacitor-inductor (LCL) filter
Data Source
AI summary
Provided are a method, an apparatus, and a system for testing an inertia coefficient and a damping coefficient of a grid-forming converter. The method includes: obtaining a filter capacitor voltage in a three-phase inductor-capacitor-inductor (LCL) filter, an inverter-side current, an output-side current, and an output three-phase voltage; outputting a frequency output signal and a phase output signal through frequency control; outputting a pulse width modulation (PWM) control signal based on the phase output signal, the filter capacitor voltage, and the inverter-side current, to control turn-on time of a power semiconductor switch; outputting an active power signal; processing the output three-phase voltage to obtain a real-time output frequency; obtaining the damping coefficient of the grid-forming converter based on the active power signal, the frequency output signal, and a related setting parameter; and obtaining the inertia coefficient of the grid-forming converter.