Virtual Synchronous Inertia Control for Renewable Power Conversion
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Solution Overview
Problem
The integration of renewable energy resources into power transmission networks faces instability due to power fluctuations, leading to divergence between input and output power, and instability in direct-current capacitor voltage, which existing solutions like virtual synchronous inertia control do not adequately address.
Innovation Solution
A power conversion apparatus that includes an inverter, PWM control, detecting units for voltage and current, a power change deciding unit, and a virtual synchronous inertia control unit to calculate and adjust the virtual inertia characteristic, thereby stabilizing output power and reducing voltage divergence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If virtual synchronous inertia control is implemented to improve power network stability, then the stability of the power network is improved, but very large divergence of energy between input power and output power occurs when renewable energy generation is suddenly lost
Solution Approach 1:
The patent applies dynamics by making the moment of inertia value variable rather than fixed. The control unit dynamically adjusts the moment of inertia based on the operational state of the power conversion apparatus, allowing the system to adapt between providing inertia support to the grid and minimizing energy divergence during sudden generation losses.
Solution Approach 2:
The patent changes the parameter of moment of inertia from a constant value to a dynamically adjustable parameter. By modifying the moment of inertia value according to system conditions, the control algorithm can optimize both grid stability support and energy balance, resolving the contradiction between these two requirements.
2Reliability
If output power is immediately limited to maintain power balance during sudden generation loss, then power balance is maintained, but the direct-current capacitor voltage deviates significantly from normal values
Solution Approach 1:
The patent applies preliminary action by having the control unit pre-calculate the appropriate moment of inertia value before power balance disruption occurs. This pre-calculated value is then applied to prevent both energy divergence and voltage deviation, addressing the contradiction before it manifests.
Solution Approach 2:
The system uses feedback by continuously monitoring the operational state and using this information to adjust the moment of inertia value. This feedback mechanism allows the system to maintain both power balance and voltage stability by adapting to changing conditions in real-time.
3Reliability
If the moment of inertia is increased to provide better inertia support to the power network, then the inertia support capability is improved, but the system complexity and control algorithm complexity increase
Solution Approach 1:
The patent uses copying by creating a virtual model of synchronous generator inertia behavior through control algorithms rather than physical inertia. This virtual inertia copying provides the necessary stability support without requiring complex mechanical systems, simplifying the overall device complexity while maintaining reliability.
Data Source
AI summary
An apparatus includes: an inverter converting generated power of renewable energy resources to predetermined alternating-current power for output to a power transmission network; a PWM control unit controlling the inverter; a first detecting unit detecting the input voltage and current to the inverter; a second detecting unit detecting the output voltage, current, and frequency of the inverter; a power change deciding unit calculating the input and output powers of the inverter and the difference therebetween from the voltage and current of each of the input and output detected by the detecting units, and calculating a correction output power command with reference to an output power command; and a virtual synchronous inertia control unit calculating a virtual inertia characteristic based on the voltage, current, and frequency of the output detected by the second detecting unit and the correction output power command, and outputting a reference command to a PWM control unit.