Stabilizing Grids and Enabling Renewable Power Generation of Wind Turbine

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Introduction

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Introduction

Power Electronics:

Application of solid-state electronics for efficient control andconversion of electrical power

Often employed whenever there is a need to modify a form ofelectrical energy (either changing its voltage, current or frequency)

Potential to make a huge contribution to the low carbon economy

Technology where Malaysia has a high growth and high value,making a significant contribution to exports and the wealth of thenation, as well as providing high-quality employment.

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Technical

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Technical: Overview Wind Turbine


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Use a Squirrel Cage Induction Generator Directly connected to grid (through a soft starter) Needs capacitor banks for reactive power

compensation

Fixed Speed Technology

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Doubly Fed Technology

Doubly fed asynchronous generator Stator directly connected to the grid, power converter in

the rotor circuit Allows for variable speed, hence better caption of

energy from wind


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Full Scale Converter Technology

Many type of generators can be used, e.g. (PM) Synchronous generator, Asynchronous generator

With and without gearbox depending on generator design

Full power converter between the generator and the grid


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Problem Statement

The operation of an ac power transmission line is generally constrained by limitations one or more network parameters (e.g line impedance) and operating variables (e.g voltage and current)

As a result, the power line is unable to transfer power among generation stations. Therefore, other parallel transmission lines that have an adequate capability of carrying additional amount of power may not be able supply the power demand.

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Large loads consume huge amounts of power and cause an excessive voltage drop which at the extreme becomes a complete collapse of the voltage.

In the other direction load shedding of a capacitive line or heavily compensated line can cause over voltages.

Switching of loads or power factor capacitors causes steps in voltage (inrush current factor 5…9 of rated power)

Rapidly varying loads or pulsing (choppering) cause voltage flickers.

Industrial grids (plants) with many different participants (loads) have network specific harmonics

Problem Concern

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Technical: Overview FACTS

FACTS Definition

Flexible Alternating Current Transmission System (FACTS) is newemerging technology and its principal role is to enhance controllabilityand power transfer capability in ac systems.

FACTS is defined by the IEEE as a power electronic based system andother static equipment that provide control of one or more ACtransmission system parameters to enhance controllability andincrease power transfer capability.

FACTS controllers are capable of controlling the interrelated lineparameters and other operating variables that govern the operation oftransmission lines series impedance, shunt impedance, current,voltage, phase angle and damping oscillation at various frequencybelow rated frequency.

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FACTS

Shunt Compensation

TSC

TCR

SVC

STATCOM

Series Compensation

TSSC

TCSC

FCSC

SSVC

SSTATCOM

Phase-Angle Compensation

UPFC

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FACTS Comparison

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Technical: STATCOM Solution

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Static synchronous compensators (STATCOMs) are part of the flexiblealternating current transmission systems (FACTS) device family.

Their primary purpose is to supply a fast-acting, precise, and adjustableamount of reactive power to the ac power system to which they areconnected.

STATCOMs achieve this by adjusting the magnitude and polarity(phase) of the reactive component of the current flowing through theirac side.

This enables STATCOMs to control the amount and direction of flow ofthe reactive power exchanged with the ac power system.

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STATCOMs can be used for voltage compensation at the receiver end of ac transmission lines, thus replacing banks of shunt capacitors.

When used for this purpose, STATCOMs offer a number of advantages over banks of shunt capacitors, such as much tighter control of the voltage compensation at the receiver end of the ac transmission line and increased line stability during load variations.

STATCOMs are also commonly used for dynamic power factor correction (i.e., dynamic reactive power compensation) in industrial plants operating with large random peaks of reactive power demand.

STATCOMs increase the power factor of the plant, minimize the voltage fluctuations at the plant input (which prevents damage to the equipment), and reduce the plant’s operating costs.

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Technical: STATCOM Principle

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Technical: STATCOM Principle The STATCOM current amplitude is defined by the voltageacross the transformer. The maximum voltage supporting current is defined by the maximum STATCOM converter output voltage. The maximum voltage suppressing current is defined by the maximum converter current

Each voltage drop/swell of Upoc causes an inherent, immediate reactivecurrent over the transformer which works against the disturbance. Reactive power injection after STATCOM voltage increase, Uconv will starting within <10ms.

Ugrid=UpocUcompensator=Uconv

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Technical: STATCOM Principle

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Technical: STATCOM Location

Where to install the STATCOM?

Key factors to be considered for location of STATCOM:Access (Offshore vs Onshore)Maintenance (Offshore vs Onshore)Losses (Power System Study)Capital (Project Stage)Operating Costs (Operation Stage)

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Technical: STATCOM Location1) Wind Turbine Level

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Technical: STATCOM Location2) Wind Farm Level (Collector Point)

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Technical: STATCOM Location3) Wind Farm Level

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Technical: STATCOM Location4) Wind Farm Level *

* Offshore Application

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Technical: STATCOM Application

Reactive power compensation solution should be selecteddepending on the application.

If static response and no continuously adjustable response is required, switched passive components are sufficient

Passive components: Transient when switched on or off Slow response time

If dynamic response and continuously adjustable response is required, STATCOM is more suitable

STATCOM components:Requires filtering in some casesVery fast response time

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Technical: STATCOM ApplicationSwitched Capacitors / Reactors

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Technical: STATCOM ApplicationSTATCOM

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The continuous increase of installed wind turbine seen during recent years has forced the transmission system operators (TSO) to tighten their grid connection rules which also known as Grid Code.

A grid code is a technical specification which defines the parameters a facility connected to a public electric network has to meet to ensure safe, secure and economic proper functioning of the electric system.

The Grid Code is very important in order to limit the effects of wind turbine farm on network quality and stability.

1) Grid Code Compliant

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Technical: STATCOM Application1) Grid Code Compliant

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Key issues are steady state and dynamic reactive power capability, continuously acting voltage control and fault ride through behavior.

STATCOM (Static Synchronous Compensator) technology which adds the missing functionality to wind turbine in order to become Grid Code compliant.

1) Grid Code Compliant

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Resonance issues arise in wind power plants because wind power plants contain both inductive source characteristics and capacitive elements.

Feeder line and cable capacitance and the substation reactive compensation equipment can create significant parallel resonance interaction with the main transformer.

2) Resonant Damping

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Technical: STATCOM Application2) Resonant Damping

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Technical: STATCOM Application3) Active Harmonic Filtering

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Technical: STATCOM Application4) Reactive Power (Q) demand during starting

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Conclusion

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Conclusion

STATCOM must be installed in order for wind turbine farm before can get connected to national grid due to stringent Grid Code applied.

STATCOM have vital roles to enable the renewable energy generation combination on national grid. Without STATCOM, wind turbine can only work in isolated network.

STATCOM offer optimisation of power output, reduce harmonic and ensure continuous stability to power system regardless the compensation demand whether static response or dynamic response.

The effectiveness of STATCOM can be further improved by introducing the energy storage devices such as BESS or DynaPeaQ system.

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Question?

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Stabilizing Grids and Enabling Renewable Power Generation of Wind Turbine