Jakob Bærholm Glasdam

Harmonic Stability Analysis

This chapter presents the harmonic stability evaluation in offshore wind power plants (OWPPs) employing power electronic devices (PEDs) in the transmission system. The primarily focus of the analysis is the evaluation of conventional and linearized frequency domain analysis methods such as the Nyquist stability criterion against the full time domain model realised in PSCAD/EMTDC. The comparison of the two domains is done for a voltage sourced converter high-voltage direct current (VSC-HVDC) grid connected OWPP, where the validated model of the controllable grid interface (CGI) is used to emulate the HVDC system. Additionally, an analysis of the harmonic stability in a high-voltage alternating direct current (HVAC) grid connected OWPP with a static compensator (STATCOM) located at the grid connection point is carried out in the time domain.

Overview of the Modular Multi-level Cascaded Converters

This chapter presents and describes some of the various modular multi-level cascaded converter (MMCC) systems, which are commercially available and considered within the research project. An overview of the previous two- and three-level voltage-sourced converter high-voltage direct current (VSC-HVDC) is briefly presented. The review will focus on the technology evolvement, industrial installations, and the working principles of the MMCCs. The review is done on the evolvement of the VSC-HVDC and the static compensator (STATCOM).

Multi-level Converter Modelling and Evaluation

This chapter present the time domain models of the modular multi-level cascaded converter (MMCC) implemented in PSCAD/EMTDC. The chapter focusses on generic modelling of the commercial available voltage-sourced high-voltage direct current (VSC-HVDC) and the static compensator (STATCOM) described in Chaps. 3 and 4. The detailed equivalent modelling technique proposed in Chap. 4 is considered in the representation of the MMCCs. The low level control, ensuring the stabilisation of the distributed sub-module (SM) voltages in the MMCCs are described and implemented. The generic modelling approach taken is evaluated based on comparison with the field measurements at London Array offshore wind power plant (OWPP).

Evaluation of the Time Domain Models of the Wind Turbine Generator and the Power Electronic Grid Simulator

The system description of the controllable grid interface (CGI) and the commercial multi-megawatt sized type 4 wind turbine generator (WTG) installed at the National Renewable Energy Laboratory (NREL) was presented in Chap. 7. Detailed, generic electromagnetic transient (EMT) models of the CGI and the WTG were developed in Chap. 8. The purpose of this chapter is the evaluation of said models. The models are implemented in PSCAD/EMTDC and evaluated for steady-state operating conditions and for various transients (including balanced and unbalanced low and high voltage ride-through (LVRT and HVRT, respectively)).

Recommended Practice for Harmonic Stability Evaluation in Wind Power Plants

The scope of this Industrial PhD project has primarily been to investigate the best possible way(s) to perform the harmonic stability studies in high-voltage alternating and direct current (HVAC and HVDC, respectively) grid connected offshore wind power plants (OWPPs). This chapter outlines the various OWPP system design studies and put forward a proposal for a “best practice” in the harmonic stability evaluation in OWPPs. The best practice is based on the knowledge sharing available when working with colleagues at DONG Energy Wind Power (DEWP), as well as the experience gained working on this project. These findings/recommendation can be incorporated in the design of future OWPPs employing power electronic devices (PEDs) in the transmission system.

Power Electronic Device Modelling in the Frequency Domain

The power electronic devices (PEDs) considered in this work have been described in the previous chapters. The PEDs have been modelled in the time domain and the models have successfully been evaluated based on comparison with measurement data. This chapter presents the frequency domain modelling of the PEDs. The comparison of the simulated results in time and frequency domain related to the harmonic stability evaluation in offshore wind power plants (OWPPs) is given in Part III.

Modelling of the Passive Power System Components

The main scope of this research project is the evaluation of the frequency and time domain harmonic stability evaluation methods in converter rich offshore wind power plants (OWPPs). In order to do this it is considered sensible to make identical representations of the passive components such as the export cable and the external power system in the two domains. This ensures that the possible discrepancies in the obtained results are related to the way the power electronic devices (PED), including their respective control systems, are represented in the two domains. The purpose of this chapter is to develop suitable methods for modelling the passive components in the two domains as a number of challenges were encountered in the preparation of this work.

Modelling of the Wind Turbine Generator and the Power Electronic Grid Simulator

The description of the National Renewable Energy Laboratory’s (NREL’s) grid simulator (referred to as controllable grid interface, CGI) and the commercial multi-megawatt sized type 4 wind turbine generator (WTG) was given in Chap. 7. This chapter focusses on the time domain modelling of the CGI and the WTG. The models of the power electronic devices (PEDs) are implemented in PSCAD/EMTDC. The obtained test results are used to evaluate the time domain models of NREL’s test setup including the PEDs in Chap. 9.

Power Electronic Grid Simulator for Wind Turbine Generator Compliance Testing

The author has had the pleasure of being a guest researcher at the National Renewable Energy Laboratory (NREL) in Colorado, US. NREL commissioned an advanced multi-megawatt sized power electronic grid simulator test system during the author’s stay-abroad. An overview of the test system is presented in this chapter. The obtained test results are used to develop and evaluate time domain models of the grid simulator (referred to as controllable grid interface, CGI) and a commercial multi-megawatt sized type 4 wind generator turbine (WTG) in Chaps. 8 and 9.

Measurement Campaign at London Array Offshore Wind Power Plant

Real life measurement data constitute an important part in industry-oriented research. The purpose of this chapter is to describe the measurement campaign realised on a state-of-the-art static compensator (STATCOM) located at the onshore grid connection point of London Array offshore wind power plant (LAOWPP).