Voltage Source Converter Emulating Synchronous Machine Stability
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Solution Overview
Problem
The increasing number of converter-interfaced electricity sources in power systems reduces necessary stability mechanisms, leading to power system stability problems as the relative amount of synchronous generators decreases, which existing technologies fail to adequately address.
Innovation Solution
A control system methodology for Voltage Source Converters (VSCs) that emulates the inherent response of synchronous machines, including stability mechanisms, allowing for fast and decoupled following of active and reactive power set points, and enabling inertial response, frequency control, and automatic load sharing, without the need for Phase-Locked Loop (PLL) and with tunable dynamic behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a complete two-axis dynamic mathematical model of synchronous machine is used (VISMA), then the stability mechanisms and grid operation capability are improved, but the computational complexity and response speed are worsened
Solution Approach 1:
The patent extracts only the essential stability mechanisms (inertial response, frequency control, voltage control) from the complete synchronous machine model, implementing them through simplified control algorithms rather than the full two-axis dynamic model. This extraction maintains the beneficial stability functions while eliminating unnecessary computational complexity.
Solution Approach 2:
The patent creates a simplified virtual model that copies only the critical dynamic behaviors of synchronous machines (inertia, damping, voltage-frequency characteristics) without replicating the complete mathematical model. This virtual representation provides adequate stability support with reduced computational burden.
2Reliability
If the complete synchronous machine model is used, then the analogy with conventional synchronous machines is improved, but the response time and set point following speed are worsened
Solution Approach 1:
The patent implements dynamic control algorithms that adapt the level of emulation detail based on operating conditions. During transient events, the system provides strong inertial and frequency support analogous to synchronous machines. During steady-state operation, the system transitions to faster power electronics control mode, maintaining the ability to follow set points rapidly while preserving synchronous machine-like behavior when needed.
3Ease of operation
If virtual torque and excitation voltage control is used, then the active and reactive power control is improved, but the computational requirements and system complexity are worsened
Solution Approach 1:
The patent replaces the mechanical virtual torque concept with direct electromagnetic control algorithms in the power electronic converter. Instead of simulating mechanical rotor dynamics, the system directly controls active power output through improved PWM control strategies. Similarly, virtual excitation voltage control is replaced with direct reactive power control through converter switching, maintaining power control capability while eliminating mechanical analogy complexity.
Data Source
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AI summary
The present invention relates to electric energy sources, such as a single wind power turbine or wind power plant, that are interfaced with the utility grid through power electronic converters. In particular, the present invention relates to specific techniques and methodologies for power electronic converters for stabilizing the utility grid during transient conditions and for providing similar stability mechanisms that are inherently present in electric synchronous generators while maintaining the possibility for fast and decoupled following of set points for generated active and/or reactive powers.