Mischa Steurer

Integration of a bi-directional dc-dc converter model into a large-scale system simulation of a shipboard MVDC power system

To improve energy flexibility and deal with peak energy demand in shipboard power system, a bi-directional dc/dc converter is investigated for a notional U.S. Navy Medium Voltage DC (MVDC) shipboard power system. Surplus energy due to light electric load or ship-speed variation can be captured by energy storages distributed in 800 V load zones and during heavy load or black starting condition, supplied to the rest of the 5 kV MVDC system through the bi-directional dc/dc converters. This paper presents the controller optimization process using the particle swarm optimization for an isolated-type bi-directional dc-dc converter. The control performance of the proposed controller is evaluated using small-signal average models and a large-scale simulation of the notional U.S. Navy MVDC system using the real-time digital simulator.

Power hardware-in-the-loop testing of a 500 kW photovoltaic array inverter

The testing of a 500 kW photovoltaic array inverter using power hardware-in-the-loop simulation is described. A real-time simulator is used with a DC amplifier in order to emulate a photovoltaic (PV) array and an AC amplifier to emulate a power grid. The test setup is described in detail and a range of tests that were conducted on the inverter are summarized.

Development of a smart-grid cyber-physical systems testbed

Emerging future smart grids will substantially increase the sophistication and diversity of control, communications, and power systems technologies. While many of these technologies are well established in their particular area, the interactions that result when combining them into a fully functioning cyber-physical system can result in many unexpected behaviors. Therefore, appropriate test platforms will become necessary to evaluate the performance of these systems in order to reveal unintended and potentially harmful interactions between subsystems before deploying such technologies in the field. In this paper, we discuss the design and development of a testbed to evaluate various smart-grid based control technologies through the use of controller hardware-in-the-Ioop real-time simulation. In particular, the focus of this testbed is to examine various “intelligent” and distributed control algorithms. The relevance of the testbed is illustrated through a case-study of a smart-grid solution known as the Distributed Grid Intelligence (DGI), which is part of the Future Renewable Electrical Energy Delivery and Management (FREEDM) project. In this case-study, we describe the impacts of various interactions such as communication timings, available computational resources, and distribution and decentralization of higher-level control on a microgrids operations. Based on the case study, this paper concludes with recommendations for future expansion and improvements to the test bed in order to better serve the smart grid research community.

Controller hardware-in-the-loop validation for a 10 MVA ETO-based STATCOM for wind farm application

This paper reports experimental validation of a Static Synchronous Compensation (STATCOM) by controller hardware-in-the-loop (CHIL) testing with a real-time digital simulator (RTDS). The controller is designed and developed for a 10 MVA STATCOM for voltage regulation at the PCC of a 50 MW wind farm connected to a 69kV utility grid. Emitter Turn-off (ETO) thyristors are switching devices in the multilevel inverter. The STATCOM controller was developed for a cascade multilevel inverter and has been validated on a laboratory test-bench. The CHIL testing of the controller is done with detailed scaled model of the 50 MW wind farm and 69kV utility system. The experimental results from the RTDS for both steady state and dynamic changes in the STATCOM output validate the STATCOM controller design and performance.

An Induction Machine Emulator for High-Power Applications Utilizing Advanced Simulation Tools With Graphical User Interfaces

In this paper, a method is presented for removing the risk associated with the testing and development of novel drive system topologies, prototype electrical machines, advanced control system strategies, or a combination of the aforementioned without using any real motors/generators. The test platforms for low-power machines are relatively inexpensive and accessible; however, as power levels increase into the upper kilowatt and megawatt range, validation of prototype machines and drives becomes costly. The proposed induction machine emulator (IME) platform utilizes the power hardware-in-the-loop concept in conjunction with a high-fidelity machine model and load dynamics. The electrical machine and its load dynamics are simulated with a real-time digital simulator, which generates appropriate control commands to a power electronics-based voltage amplifier that interfaces to a variable speed drive (VSD). Specifically, the current draw is recreated by altering the phase and magnitude of a voltage amplifier connected to a VSD under test via a unique transformer-based LCL-type coupling network. Based on the proposed concept, the use of a multiwinding, tap-changing transformer establishes a truly versatile and universal test platform for a wide range of power levels. In addition, this paper presents a control strategy in the synchronously rotating reference frame in dq coordinates for the power electronic converters in IME operation. Experimental results at the 25-kVA power level validate the feasibility and highly dynamic performance of the proposed test platform.

Impact of PV on distribution protection system

This paper investigates the impacts of PV interconnection on the protection systems of a distribution network, especially when power flow is reversed in high penetration scenarios. A Florida based substation and its six-feeders were selected for the study. The system was slightly modified to make it a notional system that still closely represents the actual system behavior from the point of view of system protection. The main modification is in the representations of loads, where all the loads were represented by fewer aggregated loads on each feeder. One of the feeders is 9 miles long and has a 12.6 MW (AC) PV plant connected to the primary side of the feeder at a distance of 4.8 miles from the substation. The feeder has an average load of approximately 11 MVA that makes it a contender for a high penetration (more than 100%) feeder when PV reaches its peak generation. The model of the entire substation, its feeders and protection system has been built using a high fidelity transient simulation tool RSCAD. Initial simulation results indicate that if protection devices are coordinated properly, a reverse power flow does not create any nuisance trip or malfunction of the protection system. However, based on the location of the PV plant with respect to the fault, slight change in the trip time of the time-overcurrent relays was observed.

Cross-platform validation of notional baseline architecture models of naval electric ship power systems

To support efforts in assessing the relative merit of alternative power system architectures for future naval combatants, the Electric Ship Research and Development Consortium (ESRDC) has developed notional baseline models for each of the primary candidate architectures currently considered, medium-voltage DC (MVDC), conventional 60 Hz medium-voltage (MVAC), and high-frequency medium-voltage (HFAC). Initial efforts have focused on the development of a consistent set of component models, of which the system models can be comprised, and the basic definition of the system models. The broader objectives of the consortium, however, go beyond the definition of the baseline models. The focus is on the process by which the models are implemented in software and validated, the process by which the performance of the disparate system models are objectively and quantitatively assessed and compared, and, ultimately, the process by which the relative merits of the architectures may be assessed. This paper focuses specifically on cross-platform component validation.

A secure and distributed control network for the communications in smart grid

The security of the control network has become a major concern since the wide deployment of smart grid systems. The functions of Intelligent Energy Management (IEM) highly depend on the communication techniques. The IEM is the service agent of smart grid communication network in a limited management zone for distributed and autonomous power system control and operations. In such a smart grid, the power flows are unpredictable. Therefore, the management nodes, i.e., IEM agents, form a communication network that has no fixed infrastructure. For this reason, the IEM network can be considered as an ad-hoc network. In this paper, the newly proposed TQOS (Trustworthiness-based Quality of Service) routing protocol is adopted to ensure that every power system communication session can be established through a secure route [1]. We calculate the performance cost of using certain encryption algorithm for building a secure route. By using Opnet simulator, we find the overall smart grid communication performance under different network conditions, by changing the network scales, packet generation size and rate, and the node processing capability. Our simulation results have demonstrated that the proposed secure and distributed network architecture can be applied to smart grid communications in practice.

Control design of STATCOM with superconductive magnetic energy storage

This paper describes the control design of a SMES power conditioning system for static reactive power compensation at distribution voltage levels. This system comprises a five-level voltage source inverter and a five-level two-quadrant chopper fed from SMES. Due to the high order nonlinear nature of multilevel converters, a multivariable control method is proposed to enable high-bandwidth control of power transfer to and from the SMES coil. Theoretical analysis of the controller design and the simulation results are presented.

A digital testbed for FREEDM system development

In this paper, a notional Future Renewable Electric Energy Delivery and Management (FREEDM) system has been developed based on a real distribution feeder. The goal is to develop a digital testbed which can be used to show capabilities of this system, and to help the development of especially the new system components and the control schemes for this system. Two digital testbeds have been developed, one to represent the small scale green hub that will be realized in the centers test facilities at North Carolina State University and the other is a more detailed notional system that can be used for large scale system level analysis and design.