Virtual Synchronous Machine Control for Grid Voltage Error Tolerance
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Solution Overview
Problem
Existing virtual synchronous machines (VSMs) are sensitive to grid voltage measurement errors and delays, leading to distortions and loss of synchronization, especially at low power, and struggle with precise control as renewable energy sources become more prevalent, causing unacceptable power fluctuations.
Innovation Solution
A model of the VSM that includes virtual current control loops and virtual capacitors to reduce measurement errors and delays, with a mechanism for smooth start-up, emulating frequency and voltage droop functionality of synchronous generators to maintain grid stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional VSM control is used, then the system is simple to implement, but it is sensitive to grid voltage measurement errors and delays causing loss of synchronization
Solution Approach 1:
The patent introduces virtual capacitors as intermediary elements in the control model. These virtual capacitors filter measurement errors and delays by modeling capacitive behavior that smooths out voltage sensing inaccuracies, thereby maintaining synchronization stability without requiring complex hardware modifications
Solution Approach 2:
The patent implements feedback mechanisms through virtual current control loops that continuously monitor and adjust the VSM operation. The control model uses feedback from grid voltage measurements to dynamically compensate for measurement errors and maintain accurate synchronization, improving reliability through closed-loop control
2Measurement precision
If virtual current control loops are added to reduce measurement errors, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent creates virtual copies of physical components through mathematical models. Virtual capacitors and virtual current control loops are implemented as software-based models that replicate the electrical behavior of physical components, providing measurement error filtering without adding physical complexity to the hardware architecture
Solution Approach 2:
The patent replaces physical measurement filtering hardware with virtual control mechanisms. Instead of using complex analog filtering circuits to reduce measurement errors, the invention uses digital virtual capacitors and control algorithms to achieve the same error reduction, substituting mechanical/electrical complexity with computational simplicity
Data Source
AI summary
Electrical apparatus (20) includes an inverter (24) having input terminals for receiving DC input power and output terminals for coupling to an AC power grid. A pulse-width modulation (PWM) generator and drivers (26) drive the switches so as to control respective amplitudes, frequencies, and phases of the output current waveforms of the inverter. Control circuitry (28) receives measurements of respective time-varying voltages and currents on the input and output terminals, computes a model (40) that includes three virtual currents flowing in a synchronous machine that is emulated by the apparatus, wherein the three virtual currents are associated respectively with the three output current waveforms, and controls the PWM generator and drivers responsively to the three virtual currents so as to synchronize the amplitudes, frequencies, and phases of the three output current waveforms of the inverter with the three phases of the AC power grid.