Mazheruddin H. Syed

A Novel Approach to Solve Power Flow for Islanded Microgrids Using Modified Newton Raphson With Droop Control of DG

The study of power flow analysis for microgrids has gained importance where several methods have been proposed to solve these problems. However, these schemes are complicated and not easy to implement due to the absence of a slack bus as well as the dependence of the power on frequency as a result of the droop characteristics. This paper proposes simple and effective modifications to the conventional method (Newton Raphson) to compute the power flow for microgrids. The presented method provides a simple, easy to implement, and accurate approach to solve the power flow equations for microgrids. The proposed method is applied to two test systems: a 6-bus system and a 38-bus system. The results are compared against simulation results from PSCAD/EMTDC which validate the effectiveness of the developed method. The proposed technique can be easily integrated in current commercially available power system software and can be applied for power system studies.

Novel Coordinated Voltage Control for Hybrid Micro-Grid With Islanding Capability

This paper proposes a new coordinated voltage control (CVC) method with reactive power management scheme (RPMS) for a hybrid micro-grid (MG). The CVC scheme, based on synchronizing the response speeds of different voltage regulating devices, is coordinated with novel RPMS. Two cases, with and without proposed CVC, were simulated in the power system computer aided design (PSCAD)/electromagnetic transients including dc (EMTDC) environment and compared against each other. The case with proposed CVC shows superior performance, when tested for fault triggered islanding, intentional islanding, and MG internal fault. Further, the proposed CVC with RPMS is compared to a voltage regulation method present in literature. The proposed CVC with RPMS provides better voltage regulation, maximizes the fast dynamic reactive power reserve, and improves the transient response and transient stability margin of the hybrid MG.

Ancillary service provision by demand side management: A real-time power hardware-in-the-loop co-simulation demonstration

The role of demand side management in providing ancillary services to the network is an active topic of research. However, their implementation is limited due to lack of practical demonstrations and tests that can rigorously quantify their ability to support the grids integrity. In this paper, provision of time critical frequency control ancillary service is demonstrated by means of integrating PowerMatcher, a well discussed demand side management mechanism in literature, with real-time power hardware. The co-simulation platform enables testing of demand side management techniques to provide ancillary services.

Grid code violation during fault triggered islanding of hybrid micro-grid

The major advantage of a micro-grid is its ability to run in both grid connected and islanded mode of operation providing higher flexibility and reliability. With increasing popularity of micro-grids and their existence becoming more and more prominent in existing power systems, more stringent adherence to frequency and voltage standards are being requested by Distribution Network Operators (DNOs) in order to maintain proper functionality of the grid. In case of any violations to the aforementioned standards, the distributed generation will have to be disconnected to ensure system security. Fault triggered islanding causes large excursions in system voltage and frequency which may lead to disconnection of DGs thereby threatening the grid integrity and strength. In this paper a review of IEEE standards and North American Electric Reliability Corporation suggested standards is presented. The use of dynamic voltage restorer as series compensation to ensure successful islanding without violating the standards is proposed. A comprehensive analysis is conducted by time domain simulations using Matlab/Simulink software.

Simulation-based validation of smart grids - status quo and future research trends

Smart grid systems are characterized by high complexity due to interactions between a traditional passive network and active power electronic components, coupled using communication links. Additionally, automation and information technology plays an important role in order to operate and optimize such cyber-physical energy systems with a high(er) penetration of fluctuating renewable generation and controllable loads. As a result of these developments the validation on the system level becomes much more important during the whole engineering and deployment process, today. In earlier development stages and for larger system configurations laboratory-based testing is not always an option. Due to recent developments, simulation-based approaches are now an appropriate tool to support the development, implementation, and roll-out of smart grid solutions. This paper discusses the current state of simulation-based approaches and outlines the necessary future research and development directions in the domain of power and energy systems.

Frequency Restoration Reserves: Provision and activation using a multi-agent demand control system

In this work a control system for restoration reserve providers is proposed in which optimal biddings of restoration reserve capacity are made based on the predicted flexibility of the reserve resources within the portfolio of the reserve provider. It is assumed that the gate closure time for submitting reserve capacity bids is 1 hour before activation time. The reserve capacity bids need to be formed so that activation of the capacity is always feasible, irrespective of the consumption of the portfolio before an activation request. The determination of the optimal reserve capacity bids is only based on aggregated flexibility constraint information received by the individual flexible resources within the portfolio of the reserve provider. No further resource-specific information is used to determine the optimal reserve capacity bid. The activation and dispatch of the required power consumption at real time is done through a market-based multi-agent control system. A simulation example, in which the reserve capacity of a portfolio of batteries is simulated, proves the feasibility of the proposed approach and shows that a high precision of the portfolio response can be obtained.

Demand side participation for frequency containment in the web of cells architecture

A large number of demand side management schemes have been proposed in literature for provision of frequency control ancillary services to the network. However, it is assumed that all the flexible devices within the network are managed and controlled under one demand side management (DSM) scheme. In this paper, two independent demand side management schemes control the portfolio of flexible devices within a web of cells architecture. A methodology and scenarios for analysis of the performance of more than one DSM scheme within the same network have been realized using a real-time power hardware-in-the-loop co-simulation platform, and the paper presents this as a basis for investigations of such arrangements.

Tuningless Load Frequency Control Through Active Engagement of Distributed Resources

The increasing share of volatile and inverter-based energy sources render electric power grids increasingly susceptible to disturbances. Established Load Frequency Controls (LFC) schemes are rigid and require careful tuning, making them unsuitable for dynamically changing environments. In this paper, we present a fast and tuningless frequency control approach that tackles these shortcomings by means of modern grid monitoring and communications infrastructures in a twofold concurrent process. First, direct observation of supply and demand enables fast power balancing decoupled from the total system dynamics. Second, primary resources are actively involved in frequency restoration by systematic adjustment of their frequency reference setpoints. In contrast to the commonly used Automatic Generation Control (AGC), the proposed direct LFC does not require an integrator for frequency control in the closed loop even under partial grid observability. The approach is Lyapunov-stable for a wide range of system parameters, including ramping limits of controlled resources. A performance study against AGC has been conducted on a three-area power system in simulations as well as in a real-laboratory grid with an installed generation capacity of 110 kW.

Cyber-physical energy systems modeling, test specification, and co-simulation based testing

The gradual deployment of intelligent and coordinated devices in the electrical power system needs careful investigation of the interactions between the various domains involved. Especially due to the coupling between ICT and power systems a holistic approach for testing and validating is required. Taking existing (quasi-) standardised smart grid system and test specification methods as a starting point, we are developing a holistic testing and validation approach that allows a very flexible way of assessing the system level aspects by various types of experiments (including virtual, real, and mixed lab settings). This paper describes the formal holistic test case specification method and applies it to a particular co-simulation experimental setup. The various building blocks of such a simulation (i.e., FMI, mosaik, domain-specific simulation federates) are covered in more detail. The presented method addresses most modeling and specification challenges in cyber-physical energy systems and is extensible for future additions such as uncertainty quantification.

Controller HIL testing of real-time distributed frequency control for future power systems

With the evolution of power system components and structures driven mainly by renewable energy technologies, reliability of the network could be compromised with traditional control methodologies. Therefore, it is crucial to thoroughly validate and test future power system control concepts before deployment. In this paper, a Controller Hardware in the Loop (CHIL) simulation for a real-time distributed control algorithm concept developed within the ELECTRA IRP project is performed. CHIL allows exploration of many real-world issues such as noise, randomness of event timings, and hardware design issues that are often not present on a simulation-only system. Octave has been used as the programming language of the controller in order to facilitate the transition between software simulation and real-time control testing. The distributed controller achieved frequency restoration with a collaborative response between different controllers very fast after the unbalanced area is located.