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Power-Hardware-in-the-Loop Test of VSC HVDC Connection for Offshore Wind PowerPlants

Cha, Seung-Tae; Sharma, Ranjan; Wu, Qiuwei; Østergaard, Jacob

Publication date:2012

Document VersionPublisher's PDF, also known as Version of record

Link back to DTU Orbit

Citation (APA):Cha, S-T., Sharma, R., Wu, Q., & Østergaard, J. (2012). Power-Hardware-in-the-Loop Test of VSC HVDCConnection for Offshore Wind Power Plants [Sound/Visual production (digital)].

Power-Hardware-in-the-Loop Test of VSC HVDC Connection for Offshore Wind Power Plants

Presenter : Seung Tae Cha (ST) Centre for Electric Technology (CET) Technical University of Denmark (DTU) June 26, 2012 @ DONG Energy

Contributors of the work Ranjan Sharma, Qiuwei Wu & Jacob Østergaard

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Outline

• Introduction • HVDC Transmission System • PHIL Platform • Experiemt Results • Conclusion • Energy Storage Simulation Case

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Introduction

• Many future WPPs will be commissioned as offshore - With longer transmission distances - Higher installed capacity

Power Transmission Options

HVAC Vs. HVDC

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Critical Issues

Cost

Energy Losses

Resonance

System services

Conditions of the grid at the PCC

Control options and requirements

Some case specific issues, for e.g., environmental issues

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• An off-shore wind power plant (WPP) interconnected to the on-shore grid via VSC-HVDC

• To verify the H/W interaction & the control co-ordination between the WPP and the VSC of the HVDC

• To provide a FRT response during the grid faults

• Technical challenges still remain

: Detailed WPP representation with cables

: Inclusion of both end VSCs

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HVDC Transmission System

Electrical Structure of an Offshore WPP

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Real Time Simulation Platform

What is Real Time Simulation: –By using the RTDS Simulator, a system’s

response over 1 second is computed in exactly 1 second.

–For a given time step of say 50 microseconds, all calculations required to determine the power system’s state are solved in precisely that amount of time. Sustain real time operation

•RTDS is a power system simulator that solves electromagnetic transients in real time

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Wind Turbine Model

Implemented in a Real time digital simulator (RTDS)

Full converter based on permanent magnet generator

No gear-box – direct drive type

Power rating – 2 MW

During the AC side voltage dip situation, the excess of wind power is dissipated into a DC chopper resistor

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Power-Hardware-In-the-Loop (PHIL) Test

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Important aspects

Startup – energize the HVDC link and the offshore grid

Steady state operation

– active power transfer

– frequency and voltage control at PCC

Fault handling

- Low Voltage Ride Through

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Fault handling

Low voltage ride through

Use chopper - simple and robust; the physical size of a DC chopper and the efforts to remove the heat is enormous

AC voltage immitation technique may be used - most modern full-converter based wind turbines are already equipped with LV-FRT mode; do not have to seperate or distinguish between grid side faults and the collector network side faults

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The main function of the WPP side VSC of the HVDC link is to provide synchronizing voltages to the wind turbines

A DC voltage feedback control is implemented to ensure regulated AC voltage magnitude at the collector network

When a fault occurs at the grid end (the HVDC voltage level exceeds beyond a threshold level), a FRT mode is activated

During the FRT mode, the WPP side VSC is taken into DC voltage control mode which allows the collector network AC voltage to drop

WPP Side VSC

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PHIL Experiment Results

Steady State Operation

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Under Disturbances

PHIL Experiment Results (continue)

During any disturbances at the grid side, the WPP side VSC is set to a FRT mode AC voltage magnitude at the collector network is reduced accordingly Wind turbine responds by lowering the active power output Power balance is thus maintained in the system

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Under Disturbances

PHIL Experiment Results (continue)

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This particular experiment contribute towards building in-depth knowledge on the steady-state and dynamic behavior of WPPs connected through VSC-HVDC links, and in order to provide recommendation for future developments. The results confirm a good co-ordination between the wind turbine and the WPP side VSC.

The response from the wind turbine is very identical to the situation when it is connected to a strong AC super grid, as the WPP side VSC is able to provide a stable voltage regulation at the collector network.

Conclusion