Current-Impressing Inverter Instantaneous Reserve via PLL Phase Error
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Solution Overview
Problem
Current-impressing inverters in power supply networks react to frequency changes with significant delays, making it impossible to provide instantaneous reserve, which is crucial for maintaining grid stability as rotating generators are phased out and replaced by decentralized renewable sources.
Innovation Solution
A method that utilizes a Phase-Locked-Loop (PLL) control loop to generate an instantaneous reserve setpoint signal from phase error signals, allowing current-impressing inverters to provide instantaneous active power changes without the need for new hardware, by integrating the signal directly into existing systems through software updates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage-impressing inverters are used to provide instantaneous reserve, then instantaneous reserve can be provided, but the system cost increases and electrical decoupling is required
Solution Approach 1:
The patent copies the instantaneous reserve provision capability from voltage-impressing inverters to current-impressing inverters by utilizing the existing PLL control loop structure. Instead of replacing the inverter type, the invention repurposes the existing control infrastructure to achieve the same functional outcome, thereby avoiding the complexity and cost associated with voltage-impressing inverters while maintaining the ability to provide instantaneous reserve.
2Ease of manufacture
If current-impressing inverters are used, then existing systems can be maintained, but instantaneous reserve cannot be provided due to delayed response to frequency changes
Solution Approach 1:
The invention makes the current-impressing inverter self-sufficient for providing instantaneous reserve by utilizing its existing PLL control loop. The PLL control loop, which is already present in current-impressing inverters for synchronization purposes, is repurposed to generate the instantaneous reserve signal. This self-service approach eliminates the need for external complex control systems or hardware modifications while achieving the required fast response capability.
3Reliability
If synchronous machines are used to provide instantaneous reserve, then frequency stability is maintained, but the systems become uneconomical and require replacement
Solution Approach 1:
The invention changes the operational parameters and control strategy of current-impressing inverters to enable them to provide instantaneous reserve. By modifying how the existing PLL control loop is utilized and interpreting its output signals differently, the system achieves frequency stability functionality previously only available from synchronous machines. This parameter change approach allows renewable energy sources to replace conventional synchronous machines economically while maintaining grid stability.
Data Source
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AI summary
The invention relates to a method for providing current reserves in an electric energy supply network by means of a current-impressing inverter. A current controller of the inverter is directly or indirectly supplied with a current reserve target value signal which is generated by means of a PLL control loop that is supplied with the measured alternating voltages of the energy supply network or signals transformed therefrom as input signals, wherein the current reserve target value signal is generated from a phase error signal of the PLL control loop. The invention additionally relates to a computer program for carrying out such a method and to a current-impressing inverter for dispensing alternating currents to an energy supply network in a controlled manner.