Serhiy Bozhko

Control of Offshore DFIG-Based Wind Farm Grid With Line-Commutated HVDC Connection

The paper considers a control solution for integration of large offshore doubly fed induction generator based wind farms with a common collection bus, controlled by a static compensator, into the main onshore grid, using line-commutated high-voltage direct current connection. The papers main focus is a mathematically grounded study of the power system interactions. That study produced an appropriate plant model for formal control design. A design procedure is described and the controlled system is validated using power systems computer-aided design/electromagnetic transient program simulations, which confirm the high performance of the proposed control strategy in both normal operation and fault conditions

Large Offshore DFIG-Based Wind Farm With Line-Commutated HVDC Connection to the Main Grid: Engineering Studies

The paper considers a solution for integration of large offshore doubly fed induction generator-based wind farms with a common collection bus controlled by a STATCOM into the main onshore grid using line-commutated high-voltage dc connection. A design procedure is described and the controlled system is validated using PSCAD/EMTDC simulations confirming high performance of the proposed control strategy in both normal operation conditions and faults. Engineering issues related to STATCOM capacitor sizing and reduction of STATCOM rating are considered and their effectiveness is confirmed.

Frequency Control Design for Offshore Wind Farm Grid With LCC-HVDC Link Connection

This paper considers the formal design for the grid frequency control in an offshore wind farm connected with line-commutated converter high voltage dc (HVDC) link. The control paradigm is based on using the grid frequency control to regulate the HVDC rectifier firing angle or dc-link current and hence control the power flow in the system. The dynamic behaviors of the system are verified by comparing the response from derived transfer functions and PSCAD simulations; hence the grid frequency controllers are designed. The control system performance has been validated by simulations of normal operation and fault regimes. The work provides a good basis for wider research investigation into wind farm operation.

Stability Study for a Hybrid AC-DC More-Electric Aircraft Power System

The paper deals with the small-signal stability analysis of aircraft ac frequency-wild power systems representing a real ac-dc hybrid distribution architecture with a multiplicity of actuators, aircraft loads, and bus geometries. The dq modelling approach is applied to derive individual power system component models and to constitute the corresponding generalized power system model as a powerful and flexible stability analysis tool. The element models can be interconnected in an algorithmic way according to a variety of the architecture selected. Intensive time-domain simulation and experimental results are used to verify the theoretical results. It is also shown how the proposed approach can be used to predict instability due to possible variations in operating points and system parameters.

DQ-transformation approach for modelling and stability analysis of AC-DC power system with controlled PWM rectifier and constant power loads

In this paper a technique for analysing aircraft frequency wild power systems with constant power loads is developed and demonstrated. Power electronic based loads often behave as constant power loads, especially when feeding machine or actuator drives under current and speed control. The constant power (CP) loads can affect the stability of the power system. The problem is a particular issue in aircraft power systems as the proportion of CP loads increases with the advent of the more-electric aircraft. This paper deals with stability analysis of a three-phase frequency-wild AC power system with a CP load fed through a vector-controlled front-end PWM converter. The mathematical model suitable for stability analysis is derived using the DQ-transformation method. It is shown how the proposed approach can be applied to study the power system behaviour under different loads and parameters variations, as well as to assess the power system stability margins. The study is supported by intensive simulations that verify the reported theoretical results.

An overview of the more electrical aircraft

This article introduces the more electric aircraft concept and investigate the potential benefits of the technology for manned aircraft. Typical aircraft electrical power systems and loads are described as well as the exciting, future challenges for the aerospace industry. The importance of power electronics as an enabling technology for this step change in aircraft design are considered and examples of typical system designs are discussed.

Stability analysis and modelling of AC-DC system with mixed load using DQ-transformation method

Power electronic based loads often behave as constant power loads, especially when feeding machine or actuator drives under current and speed control. The constant power loads (CPL) can affect the stability of the power system. The problem is a particular issue in aircraft power systems as the proportion of CPLs increases with the advent of the more-electric aircraft. This paper deals with stability analysis of a three-phase frequency-wild AC power system with CPL fed through six-pulse diode rectifier. The mathematical model of the power system suitable for stability analysis is derived using DQ-transformation method. Simulation results are used to verify the theoretical results. It is also shown how the theory can be used to predict instability due to possible variations in system parameters.

Grid Frequency Control Design for Offshore Wind Farms with Naturally Commutated HVDC Link Connection

This paper considers the formal design for the offshore grid frequency control in an LCC HVDC connected wind farm. The control paradigm is based on using the grid frequency control to regulate the HVDC rectifier angle and hence control the power flow in the system. The dynamics of the system are derived and a grid frequency controller is designed. The mathematical analysis and the control design are verified through PSCAD simulation. Good modeling agreement is obtained for both open and closed loop systems and the work provides a good basis for wider research investigation into wind farm operation including fault behaviour.

Accelerated simulation of complex aircraft electrical power system under normal and faulty operational scenarios

The more-electric aircraft concept (MEA) is one of the major trends in modern aircraft electric power system (EPS) engineering. The concept results in a significantly increased number of onboard loads driven by power-electronics. Development of appropriate EPS architectures, ensuring the power system integrity and assessment of overall system quality and performance under possible normal and abnormal scenarios requires extensive simulation activity. At the same time, the increased use of tightly-controlled motor drives and power electronic converters can make the simulation of the large-scale EPS impractical due to enormous computation time or numerical non-convergence due to the model complexity. Hence, there is a strong demand for accurate but time-efficient modeling techniques for MEA EPS simulations. This paper reports the development of a functional models library capable of maintaining good accuracy up to a specified frequency range. The library is applied to study the performance of a twin-generator example EPS under both normal and faulty regimes. The attained improvement in simulation time confirms the performance of the developed functional models for the study of complex MEA EPS architectures.

Accelerated functional modeling of aircraft electrical power systems including fault scenarios

The more-electric aircraft concept is a fast-developing trend in modern aircraft power systems and will result in an increase in electrical loads fed by power electronic converters. Finalizing the architectural bus paradigm for the next generation of more-electric aircraft involves extensive simulations ensuring power system integrity. Since the possible number of loads in an on-board power system can be very large, the development of accurate, effective and computational time-saving models is of great importance. This paper focuses on development of a modeling approach based-on functional representation of individual power system units. This provides for possibility of fast simulation of a full generator-load power system under both normal and fault conditions. The paper describes the modeling principle, illustrates the acceleration attainable and shows how the functional representation can handle fault scenarios.