PV Signal Decomposition for OLTC Wear Reduction
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Solution Overview
Problem
Existing methods for reactive power compensation in photovoltaic (PV) systems face challenges such as increased network losses and mechanical wear due to fast PV power variations, particularly with On-Load Tap Changing (OLTC) transformers, which require frequent tap changing and inject additional reactive power into the network, leading to inefficiencies and reduced transmission capacity.
Innovation Solution
A programmable filter is used to decompose PV output signals into low-frequency and high-frequency components, based on sun movement and cloud shading respectively, to generate a reactive power compensation reference signal, allowing for dynamic reactive power support by PV inverters, thereby reducing the burden on OLTCs and minimizing network losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If OLTC transformers are used for voltage regulation, then direct voltage regulation is achieved, but the mechanical tap changers experience increased wear and lifetime reduction due to frequent tap changing actions caused by fast PV power variations
Solution Approach 1:
The invention segments the voltage regulation function between two systems: fast reactive power compensation by PV inverters handles high-frequency voltage variations, while OLTC transformers handle only low-frequency voltage variations. This segmentation allows OLTC to operate less frequently, reducing mechanical wear and extending lifetime while maintaining effective voltage regulation.
Solution Approach 2:
The invention introduces a low-pass filter as an intermediary component that processes the voltage signal to separate low-frequency and high-frequency components. This filter mediates between the voltage measurement and the control systems, enabling the PV inverter to respond only to slow voltage variations and preventing it from reacting to fast PV power fluctuations, thereby reducing OLTC tap changing actions.
2Reliability
If reactive power compensation techniques are used to deal with voltage variations, then voltage regulation is achieved, but large amounts of reactive power are injected into the network leading to increased network losses
Solution Approach 1:
The invention implements dynamic reactive power compensation where the PV inverter adjusts its reactive power output based on the low-frequency component of voltage variations. By using a low-pass filter to determine the reactive power reference, the system dynamically responds only to slow voltage changes, avoiding unnecessary reactive power injection during fast PV power fluctuations, thereby reducing network losses while maintaining voltage stability.
Data Source
AI summary
A system for online filtering of photovoltaic (PV) output signals includes a programmable filter that is programmed to decompose measured PV output power into an estimated low-frequency signal component, based substantially on movement of the sun and an estimated high-frequency signal component, based substantially on cloud shading. An open loop controller generates a reactive power compensation signal based on at least one of the low-frequency signal component and the high-frequency signal component. The low-frequency signal component is defined by a positive portion of a sine curve that is based substantially on movement of the sun.