DC Microgrid Stability Monitoring via Signal Injection
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Solution Overview
Problem
Existing methods for stabilizing DC microgrids are computationally intensive and require additional converters for analysis, making them inefficient for systems with multiple sources and loads, and often result in overdesign with oversized filters and slow controllers.
Innovation Solution
A monitoring loop and dynamic virtual impedance (DVI) system that injects periodic signals into the control loop of a switching power converter to measure and stabilize the DC power system stability, using sensor circuits to monitor voltage and current, and adjust the frequency and amplitude of the signals to match the system's minor loop gain crossover frequency, allowing for continuous stability monitoring and virtual impedance emulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional methods are used to handle all possible scenarios, then system stability is improved, but the system becomes overdesigned with oversized filters and slow controllers
Solution Approach 1:
The patent implements adaptive tuning techniques that dynamically adjust controller parameters based on real-time system conditions. The digital controllers of converters are automatically tuned online to match actual operating scenarios, replacing static overdesign with dynamic adaptation. This allows the system to maintain stability for all possible scenarios without permanently oversized components.
Solution Approach 2:
The invention changes controller parameters adaptively based on measured system characteristics. By continuously measuring system impedances and health parameters, the controllers adjust their gain and phase margins to maintain optimal stability performance. This eliminates the need for conservative fixed parameter designs while ensuring stability across varying operating conditions.
2Measurement precision
If wideband perturbation methods are used to measure impedances, then system stability measurement is achieved, but computational complexity increases
Solution Approach 1:
The patent uses periodic signal injection at specific frequencies to measure system impedances. Instead of continuous wideband perturbation, the system injects periodic signals at the operating frequency and measures the response. This reduces computational complexity by focusing measurements only at relevant frequencies rather than sweeping through all frequencies continuously.
Solution Approach 2:
The measurement system uses the existing converter controllers and measurement infrastructure to perform impedance measurements. The converters themselves generate the test signals through their normal switching operation, and the control systems process the measurement data. This eliminates the need for separate dedicated measurement hardware and reduces overall system complexity.
3Measurement precision
If wideband perturbation methods are used for impedance measurement, then stability analysis is achieved, but additional converters are required
Solution Approach 1:
The patent makes existing converter controllers perform dual functions: normal power conversion control and stability measurement. The same digital controllers that regulate power flow also execute impedance measurement algorithms and stability assessment. This eliminates the need for separate dedicated measurement converters while maintaining comprehensive stability monitoring capability across the microgrid.
Data Source
AI summary
An apparatus monitoring system stability of a DC power system includes a switching power converter with a control loop. The converter is connected to a DC bus of the system. A monitoring loop injected into the control loop includes a sensor circuit monitoring voltage and current of the DC bus and a small signal injector producing a periodic signal with variable amplitude and frequency and injects the periodic signal on a reference signal of the control loop. The monitoring loop includes a stability measurement circuit that varies a frequency input to the small signal injector until the periodic signal has a frequency equal to a system minor loop gain crossover frequency of an impedance ratio of a converter closed loop output impedance and an impedance of the DC power system. The monitoring loop includes a measurement output circuit that outputs a DC power system stability margin at the crossover frequency.