Virtual Generator Command Control for Microgrid Power Conversion
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Solution Overview
Problem
In microgrid or off-grid systems, the power conversion device connected to a bus experiences instability due to changes in load, leading to challenges in stabilizing power supply and demand, as existing techniques assume an infinite bus and fail to effectively control power conversion.
Innovation Solution
A command generation device and method that calculates a root-mean-square voltage value and phase of a virtual power generator using a rotor model, determines a phase difference angle, and generates control commands for the power conversion device based on these calculations to stabilize power conversion, ensuring stable operation despite changes in bus frequency and voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a control logic is modeled assuming an infinite bus (ideal power supply with constant frequency and voltage), then the control system is simplified, but the power conversion device cannot be stably controlled in microgrid or off-grid systems where bus power changes due to load variations
Solution Approach 1:
The patent introduces a virtual synchronous generator as an intermediary control model that bridges the simplified infinite bus assumption and the actual variable bus conditions. The virtual synchronous generator simulates the mechanical and electromagnetic characteristics of a real synchronous generator, providing a control framework that adapts to bus power changes while maintaining stable operation of the power conversion device
Solution Approach 2:
The patent changes the control parameters from fixed infinite bus assumptions to dynamic parameters that track the virtual synchronous generator's rotor speed, terminal voltage, and power output. By continuously adjusting these parameters based on load conditions, the system maintains stable control despite bus power variations
2Adaptability or versatility
If the bus power is allowed to change freely with load variations, then the system responds naturally to demand changes, but the power conversion device experiences instability and cannot maintain proper operation
Solution Approach 1:
The patent implements feedback control by continuously monitoring the bus power conditions and adjusting the virtual synchronous generator's output accordingly. The control system uses feedback from the actual bus state to modify the virtual generator's terminal voltage and power output, ensuring the power conversion device operates stably while adapting to load changes
Solution Approach 2:
The patent transitions from static infinite bus assumptions to dynamic modeling where the virtual synchronous generator's parameters (rotor speed, terminal voltage, power output) continuously adapt to changing load conditions. This dynamic approach allows the system to respond naturally to demand changes while maintaining stable power conversion device operation through real-time parameter adjustment
Data Source
AI summary
This command generation device generates a control command for a power conversion device which converts DC power outputted by a DC power supply device to AC power and supplies the same to a bus, and which converts AC power from the bus to DC power and supplies the same to the DC power supply device. Said command generation device comprises: a virtual power generation calculation unit which simulates the driving of a virtual power generator and, on the basis of a rotor model that calculates the rotational speed of the virtual power generator, calculates the root-mean-square voltage and phase of the virtual power generator; a bus calculation unit which calculates the voltage and phase at a point of contact between the power conversion device and the bus; a phase difference angle calculation unit which calculates the phase difference angle between the phase of the virtual power generator and the phase at the point of contact; a target power determination unit which determines a target value for the effective power of the power conversion device on the basis of the root-mean-square voltage of the virtual power generator, the voltage at the point of contact and the phase difference angle; and a command generation unit which generates a control command for the power conversion device on the basis of the determined target value for the effective power.