Power System Stabiliser Capability of Offshore Wind Power Plants

Copenhagen, 16th April 2012

José Luis Domínguez-GarcíaOriol Gomis-Bellmunt

Fernando BianchiAndreas Sumper

Antoni Sudrià-Andreu

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Overview

· Introduction

· Power system stability background

· Objectives

· Power System Stabiliser for Wind Turbine

· System simulations

· Comparison of different PSS schemes

· Effect of the cable length on the PSS capability

· Conclusions

Power system stability background

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- Rotor angle stability maintain or restore the equilibrium between the electromagnetic torque and the mechanical torque.- Small Signal stability A power system under a small disturbance is considered in small signal stability. A small disturbance can be, for example, minor changes in load or in generation on the power system.

Power SystemStability

FrequencyStability

VoltageStability

Rotor AngleStability

Small SignalStability

TransientStability

Non-oscillatory mode

Oscillatory mode - Inter-area modes [0.1 – 0.7] Hz - Local or Intra-area modes [0.7- 2] Hz

Problem solved by PSS

Objectives

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Wind Power has rapidly increased its penetration to power systems reducing the global inertia of the system.

Source: Wind in Power (2012) EWEA

Offshore is growing faster in the last years.

Source: Wind in Power (2012) EWEA

Data in GW

Data in MW

Objectives

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TSO are requiring some support,• Fault Ride Through• Reactive Power regulation• Frequency Support• Damp Power System Oscillations (In a Future)

Since Offshore Wind Power Plants are far from the shore and Wind Power are connected far from conventional generation.

OWPP can only affect to inter-area oscillation modes

Objectives

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Wind Power neither engage nor induce oscillation modes to power systems, because of their technologies both FSWT and VSWT.

FSWT Can contribute with their inertia. (Limited Regulation)VSWT Can regulate the power delivered by the converter.

OWPP Communication required (to any signal non-local)

OWPP + PSS controller with using local signals

Power System Stabiliser for Wind Turbine

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Lead/LagBPFInput Output

K

Conventional PSS scheme for Synchronous machines

Inputs: Any signal affected by the oscillation.

- Active Power,- Frequency,- Angle synch. generators- Voltages

Outputs: Any signal capable to vary the power flow of the power system

- Active Power on the WT- Reactive Power on the WT- Voltage on WT terminal or CCP

Simplifications: WT does not need to fix exactly the phase of the Synch. Generators because it affects the power flows.

Power System Stabiliser for Wind Turbine

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Input:

OWPP terminal voltage Local Signal

No WAMS communications required

Output:

Active Power and/or Reactive Power reference of the OWPP

Power System Stabiliser for Wind Turbine

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Parameter Design

Band Pass Filter

Proportional Controller

Limiter

Δxmin = -0.15 p.u

Δxmax = 0.15 p.uFor all the controllers

Ƭm= 0.1

Ƭwh= 2[0.1-1.5Hz]

Kp = 104

Kq = -105Designed to obtain good response

System under study

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OWPP Aggregate model

2 synchronous generation areas

2 large tie-lines connecting areas

OWPP connected to 1 tie-line

FAULT Three-Phase fault in 1 ofthe connection tie-lines with the following line disconnection

Case I: Comparison of different PSS schemes

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Active Power flowing among areas Voltage mag. at the OWPP terminal

Assuming a constant location of the OWPP, different PSS schemes have been compared

Pwt delivered by the OWPP Qwt delivered by the OWPP

Case II: Effect of the cable length on the PSS capability

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Active Power flowing among areas Voltage mag. at the Area 1 Bus

Assuming a the same PSS scheme on the OWPP (PQ-PSS), under various OWPP cable connection length

Pwt delivered by the OWPP Qwt delivered by the OWPP

Conclusions

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• PSS controllers have shown promising damping properties

• PQ – PSS presented the best damping behaviour

• The length of the cable reduces the observability of the

oscillation

• Even in case of long cable, OWPP-PSS provides satisfactory

damping capability

• PSS schemes without communications can provide good

damping to the system, even being far away from the point of

interaction

Thank you for your attention!

Questions?