Fiber Optic Wind Turbine and Wind Farm Applications



Introduction

Global warming and climate changes from CO2 emissions of traditional energy sources, such as those powered by fossil fuels, have created huge markets for alternative power generation. Wind turbine energy has become a popular alternative to meet the fast growing energy demand. Unlike fossil fuels, which are a limited and diminishing resource, wind energy is limitless and readily available.

Conversion of wind energy into utility grade AC power requires power electronics, such as rectifiers and inverters. In a high power generation system, galvanic insulation becomes very important to ensure the quality and reliability of the power generation.

Fiber optic components offer protection by providing insulation from high-voltage glitches and unwanted signals in power electronic devices.

Avago Technologies offers highly reliable industrial fiber optic components for data-acquisition/control and isolation in the power generation market. Featuring outstanding performance in high insulation voltage and high immunity to EMI, these products can be installed to operate in close proximity to power-carrying conduits which emit disruptive electrical interference. As the demand for renewable energy grows globally, wind turbine designs are becoming larger and larger. Avago Technologies’ industrial fiber products offer a wide range of data-rate and link lengths for many applications in this power generation market.

Key applications for industrial fiber optic components in a wind turbine system include:

  • Power electronic gate driver for rectifiers and inverters
  • Control and communication boards
  • Turbine control units
  • Condition monitoring systems
  • Wind farm networking
Figure1
  • Figure 1. Wind Turbine Power Generation Block Diagram

  • WIND TURBINE POWER GENERATION

    Wind turbine power is used to convert kinetic energy into electrical energy through the use of a generator. As wind conditions vary, the electrical energy created from the generator needs to be converted for usability. A rectifier, inverter, transformer and filter are needed within the wind turbine for utility-grade AC power to be transmitted over long distances (Figure 1).

    A transformer is usually installed at the bottom of the tower to provide voltage conversion from the low voltage generated by the wind turbine, to medium/high voltage for transmission.

    RECTIFIER AND INVERTER

    The rectifier and inverter are key components in the wind turbine system. The rectifier converts noisy AC power to DC power, while the inverter converts DC power to clean and reliable AC power. The switching of these devices is usually controlled by a DSP-embedded controller via a fiber optic link, to provide efficient and reliable switching control with high galvanic isolation capability.

    There are numerous rectifier and inverter control switches available:
    • Insulated Gate Bipolar Transistor (IGBT)
    • Gate Turn Off Thyristor (GTO)
    • Integrated Gate Commutated Thyristor (IGCT)
    • Symmetrical Gate Commutated Thyristor (SGCT)
    • Emitter Turn Off Thyristor (ETO)
    Figure2-3
  • Figure 2. IGBT Gate Driver Block Diagram
  • Figure 3. ETO Two-Level Voltage Source Converter Phase Leg Block Diagram

  • Fiber optic components are commonly used to control a high voltage and current switching device, with reliable control and feedback signals (Figures 2 and 3).

    CONDITION MONITORING SYSTEM

    Most modern wind turbines have intelligent features to monitor and control the system to accommodate varying wind conditions. For example, atmospheric sensors detect wind speed and direction. Other sensors monitor the condition and strength of the turbine’s parts to avoid run-to-failure.

    Wind turbines need to withstand extreme weather conditions, such as storms and lightning. In these conditions, it is important to ensure that the turbine’s monitoring system is designed to provide high voltage and current isolation. Fiber optics becomes a preferred choice of medium as it offers much higher voltage and current isolation properties compared to optocouplers and other similar components.

    Figure4
  • Figure 4. Elements within a Wind Turbine Nacelle Requiring Fiber Communications.
    Wind Turbine Development: Location of Manufacturing Activity, S. George and S. Matt, “Renewable Energy Policy Project”, September 2004

  • In the nacelle of the wind turbine (Figure 4), short link distances using fiber optics can utilize POF (plastic optical fiber) and Avago Technologies’ HFBR-0500Z products. Designers can select from connectors with snap-in, latching, and screw-in designs. Avago Technologies’ versatile link sub-family allows field connector capabilities for POF and the associated connectors, allowing for field repairs, maintenance, and installation.

    Besides good isolation properties, these products provide excellent signal integrity as they are immune to electro-magnetic interference (EMI). They are an excellent solution for monitoring system communica- tions over long distances with reliable data transmission in high voltage/current applications.

    For greater ESD and EMI protection, Avago Technologies’ HFBR-0506AMZ series offers a metalized packaging that provides excellent shielding. The SMA-styled connector also works well in areas with vibration and mechanical shocks.

    WIND TURBINE AND WIND FARM NETWORKING

    Data collected from the condition monitoring systems, with the use of short-link POF fiber links in individual wind turbines, are typically multiplexed into HCS (hard-clad silica) or multi-mode fiber cables. The longer link distances of HCS and multi-mode fiber may be needed if wind turbine towers are greater than 100 meters in height. Fiber cables are both robust, offer greater resistance to harsh environmental elements, and are lightweight. All of these are requirements for vertical cabling in wind turbine towers.

    Industry standard connectors like the ST/ST-thread and SMA are all available from Avago Technologies. The HF-BR-0400Z series operates over both HCS and multi-mode fiber, which offer greater bandwidth and link distance compared to the POF solution. These parts are commonly used in wind turbine towers and over long distance wind farm networks.

    Avago Technologies has developed a series of fiber optic transmitters, receivers, and transceivers for wind turbine monitoring systems and networking applications and offers parts from 650nm, 820nm, or 1300nm, which have data rates up to 160MBd to meet customer needs over various link distances.

    For more information about Avago Technologies and fiber optic products for wind farm applications go to www.avagotech.com.