Xavier Guillaud

High Wind Power Penetration in Isolated Power Systems—Assessment of Wind Inertial and Primary Frequency Responses

Grid operational challenges are significant to increase securely the wind penetration level. New embedded control functions are therefore required in order to make participate wind generators in power system management. In this paper the implementation of inertial response and primary frequency control in a wind turbine controller are investigated. Main factors affecting the performances of the frequency regulation are identified and characterized. The influence of control parameters and the turbine operating point on the inertial response are analyzed through obtained performances in an islanded power system. The combined control scheme using both controllers is also developed and the potential of the obtained grid service at partial load is discussed.

Method for small signal stability analysis of VSC-MTDC grids

This paper deals with small signal stability analysis of Voltage Source Converter based Multitermial HVDC grids (VSC-MTDC). First, a simplified model is used to predict the voltage dynamic behavior. Next, a modular method to build the state space model of the overall MTDC system is described. Model validation is achieved in time domain by a comparison with an electromagnetic simulation in EMTP-rv. As concrete example of effective application, a parametric study on the droop value is carried on a 3-terminal meshed HVDC grid. This example attests to the effect of the droop parameter on the stability of the overall system.

Methods for Assessing Available Wind Primary Power Reserve

To ensure power system security with very high wind generation (WG) penetration, the participation of wind generators in primary frequency control is essential. Previous studies have shown the technical capability of wind turbines to participate in primary frequency regulation at a wind farm level. In order to analyze, the contribution of wind power to primary frequency regulation at system level one needs to quantify the amount of primary reserve from conventional sources that can be displaced. This amount of reserve depends on the aggregated variability of WG during each reserve provision time-interval. This paper presents a statistical approach to assess the impact of intrahour wind power variability on the volume of primary reserve that can be provided from WG. Furthermore, the effectiveness of different reserve allocation strategies is compared. The proposed approach is applied to a case study based on real-wind data measurements from the French island of Guadeloupe. Results show that for a small isolated system neglecting WG intrahourly variability leads to an overestimation of its contribution to primary reserve.

Hardware-in-the-loop simulation of different wind turbines using Energetic Macroscopic Representation

A hardware-in-the-loop (HIL) simulation of a wind energy conversion system has been developed using energetic macroscopic representation. Wind, turbine and mechanical power train are emulated by controlled DC drive to impose the dynamical behavior of the actual process on the generator shaft. In this paper, this HIL simulation is extended to two different wind turbines. The first one leads to extract a rated power of 900 kW using fixed blades. The second turbine leads to extract a rated power of 2 MW using adjustable blades. Experimental results are provided on reduced power experimental set-up for both wind turbines

Real-time simulation of a medium scale distribution network: Decoupling method for multi-CPU computation

The paper proposes a methodology to model and simulate a medium scale distribution network with several feeders in a real-time multi-core environment. Due to the small length of the lines, this type of simulation is still quite challenging especially when several cores are addressed to compute the simulation. Problems of model conditioning for multi-core computing are discussed. Validation results are then presented. The data of the considered medium scale distribution network are related to a real French 20 kV power system. The used realtime simulator is RT-LAB.

Real-time simulation: The missing link in the design process of advanced grid equipment

This paper describes a design process of advanced grid equipment including both dynamic simulations and power-hardware- in-the-loop. A case study concerning the insertion of an energy storage system in a large isolated grid is used as an illustrative example. First, the methodology developed to achieve a real-time simulation of the studied grid from its original dynamic model is presented. The real-time platform used within the framework of this project is based on the RT-LAB environment and is interfaced with real ultracapacitors through a power amplifier. Some experimental results are analyzed in the final part. The advantages of this methodology including power-hardware- in-the-loop are emphasized by illustrating its contribution to dynamic model validation and the obtained improvement in control system performances.

Generalized Gain Scheduling for Deloaded Wind Turbine Operation

The ability to produce less power than what is available from a wind source, a condition known as deloaded operation, is needed for a wind turbine to reproduce synchronous machine behavior in terms of inertial response and frequency droop regulation. Deloaded operation requires the ability to regulate both power production and rotor speed under any wind speed conditions. In this paper, a novel controller for deloaded wind turbine operation is presented. This controller is made possible by a Cp table inversion procedure allowing generalized gain scheduling for linearization of the pitch response. After introducing the wind turbine models, a review of classical turbine control principles and the proposed deloaded wind turbine control architecture is presented. A discussion of wind turbine non linearity and linearization principles follows. Simulation results are shown for stability, immunity to icing and performance. The advantages of generalized gain scheduling over classical gain scheduling are demonstrated by simulation results.

Investigation on interactions between AC and DC grids

In this paper, interactions between AC and DC systems are investigated with theoretical proof. Results are assessed by modal analysis, using participation factor to retrieve the eigenvalues origin among system states. A simple system is studied to present basics of AC/DC interaction studies. Such an example allows an in depth analysis, a very helpful step for understanding more complex systems. Observations were confirmed by time domain simulations comparison with EMT models. The DC part is a Multi-terminal HVDC grid controlled by the voltage droop method. Finally, a case with grid side Voltage Source Converters participating to the primary frequency control is considered.

Small-signal state-space modeling of an HVDC link with modular multilevel converters

The Modular Multilevel Converter (MMC) represents the recent development among the diverse available topologies of VSC and is allegedly the most suitable solution for converters in HVDC transmissions. This paper presents an Average Value Model (AVM) of the MMC that still includes the characteristic internal dynamics that are non-existent in traditional 2-level VSCs. This AVM and its control are described and linearized in order to obtain a state-space model of the MMC that can easily be used as a subsystem for multi-terminal HVDC (MTDC) grids. A case study showing a 401-level MMC-based HVDC link simulated in the EMTP-RV software validates the proposed state-space representation of the MMC.

Coupling between the frequency droop and the voltage droop of an AC/DC converter in an MTDC system

MTDC systems are required to be reliable, and in certain cases, should participate in the AC grids frequency regulation. This can be achieved by providing AC/DC converters with a dual controller combining both the voltage-droop and the frequency-droop control techniques. In this paper, the coupling between the two droops is theoretically investigated and quantified for both a DC side fault and an AC side fault. A 5-terminal HVDC grid is simulated to validate the theoretical results.