Lakshan Piyasinghe

Impedance Model-Based SSR Analysis for TCSC Compensated Type-3 Wind Energy Delivery Systems

Summary form only given. This paper employs impedance-model-based frequency domain analysis to detect subsynchronous resonances (SSR) in Type 3 wind farms with Thyristor Controlled Series Capacitor (TCSC). The contributions of this paper are (i) the derivation of dynamic phasor based TCSC impedance model and (ii) the application of such impedance model in Type 3 wind energy systems for SSR analysis. Impedance models for TCSC with constant firing angle control and impedance control are derived in this paper. With the derived impedance models, Nyquist-stability-criterion is applied to compare SSR stability in Type 3 wind farm with TCSC or with fixed capacitor compensation. This paper employs analytical models to demonstrate TCSCs capability in avoiding SSR in Type 3 wind generator interconnection systems. The analytical results obtained through impedance models are validated by detail model-based (with thyristor switch modeled) time-domain simulation in Matlab/SimPowerSystems.

Real-time digital simulation modeling of single-phase PV in RT-LAB

In this paper, the real-time simulation model of a single-phase single-stage Photovoltaic (PV) has been developed in RT-LAB. The model is composed of a detailed model of a PV with Maximum Power Point Tracking (MPPT), a Phase Locked Loop (PLL), a proportional resonance (PR) controller, and a full bridge inverter. As the RT-LAB works in discrete time domain, modifications have been applied to the MPPT and the PR controller. The paper presents the control structures in discrete domain. Two categories of case studies have been carried out. In the first case, an irradiance signal composed of a ramp and a step change was applied. In the second case, the irradiance was generated by a Chroma controllable voltage source to emulate the random irradiance and it has been sent to the RT-LAB as an input signal. Outputs from the RT-lab were captured in oscilloscopes. The paper demonstrates the use of the developed PV model for real-time digital simulation and for hardware integration.

Real-time simulation and hardware-in-the-loop tests of a battery system

In this paper, a real time model of the microgrid with an energy storage system has been implemented in RT-Lab. Coordinated control of the battery storage system with a PV system is simulated. To be more realistic, hardware-in-the-loop (HIL) testbed has been implemented with a real battery cell (3.2-V, 40-Ahr) connected to the real-time simulation model of the microgrid. A programmable current source (Magna) and programmable load (Bk 8500) have been used to create charging and discharging paths between the energy storage unit and the RT-LAB.

Dynamic phase based model of Type 1 wind generator for unbalanced operation

Dynamic phasor representation which is defined based on the Fourier series representation is capable of capturing the behavior of a system contained with different frequency components. This makes it ideal candidate for power electronics circuit modeling and machine modeling under unbalanced conditions. This paper deals with modeling of Type 1 wind generator for unbalanced operation using dynamic phasor representation. More detailed insight of the system is achieved through small signal analysis.

An optimal power flow algorithm considering wind power penetration

This paper presents a new approach to determine the power that can be extracted from a wind farm for a given wind speed, while dispatching the rest of the system to have minimum cost. Obtaining exact power output by considering the power losses inside wind turbine is a challenge in implementing a more accurate economic dispatch pattern. An iterative algorithm combining optimal power flow for minimum generation cost with steady state conditions of a Doubly-Fed Induction generator (DFIG) is proposed to overcome the above challenge. The method presented here can accommodate all the losses inside the wind farm hence more accurate results can be obtained.

Initialization of unbalanced radial distribution systems for small signal stability analysis

This paper investigates the application of sweeping method in initializing the state variables of an unbalanced radial distribution system for small signal analysis. The unbalance is caused by a single-phase PV system. The system is composed of a three-phase induction machine (IM), a single-phase PV, a load, and a power factor correction (PFC) unit. The IM is modeled in positive-, negative-, and zero- sequence dynamic phasors and then converted into in a abc dynamic phasors frame. The PV, load and PFC and radial network are all modeled in phase-based dynamic phasors. The sweeping method along with embedded Newton-Raphson iterations is implemented to find the equilibrium point for initialization. The iterative procedures are illustrated and demonstrated by case studies. A dynamic simulation case study is also presented.

Impedance model-based SSR analysis for TCSC compensated type-3 wind energy delivery systems

This paper employs impedance model-based frequency domain analysis to detect subsynchronous resonances (SSRs) in Type-3 wind farms with thyristor-controlled series capacitor (TCSC). The contributions of this paper are 1)the derivation of dynamic phasor-based TCSC impedance model and 2)the application of such an impedance model in Type-3 wind energy systems for SSR analysis. Impedance models for TCSC with constant firing angle control and impedance control are derived in this paper. With the derived impedance models, Nyquist stability criterion is applied to compare SSR stability in Type-3 wind farm with TCSC or with fixed capacitor compensation. This paper employs analytical models to demonstrate TCSCs capability in avoiding SSR in Type-3 wind generator interconnection systems. The analytical results obtained through impedance models are validated by detail model-based (with thyristor switch-modeled) time-domain simulation in MATLAB/SimPowerSystems.

Capacitor siting using benders decomposition

This paper presents an optimization problem of siting capacitors in a power network to achieve economic benefits. The formulated optimization problem is a nonlinear mixed integer programming problem. In order to find an approximate optimal solution, Benders decomposition is adopted. The optimization problem will be decomposed into a main problem and a subproblem. The subproblem determines dispatch patterns for generators to minimize an objective function if the sites of the capacitors are given. The subproblem is a conventional AC optimal power flow problem. Existing toolboxes such as MATPOWER is used to solve such problems. The subproblem helps to create Benders cuts for the main problem which decides where to put capacitors with a set of cuts introduced accumulatively from the subproblems at each iteration. The main problem is solved by MATLAB CVX toolbox. Numerical results for IEEE 118-bus system are given.