Modular multilevel converter (MMC) is a highly suitable converter for medium- and high-voltage applications. Its structure is based on the series connection of many submodules (SMs). While the introduction of 10 kV SiC MOSFET modules has enabled higher voltage and switching frequencies for each SM using simple configurations, this also exacerbates operational challenges, including electrical stresses. Consequently, the design and evaluation of SMs under these conditions are crucial for ensuring reliable operation. This paper focuses on the electrical design and evaluation for a 10 kV SiC power module-based SM in a medium-voltage MMC with middle SMs. First, stray inductance of the PCB busbar with different connections are evaluated, providing guidance to select proper configuration with smaller stray inductance. Then, surface electric field intensity on the customized PCB busbar under various voltage stresses are evaluated to prevent partial discharge as much as possible. Finally, to evaluate the electric field distribution in the SM, electric fields of the entire core area of a SM, including the power module, gate drivers, PCB busbar, heatsink, and copper bars, are analyzed under full dc voltage and realistic switching stress with high dv/dt. The stray inductance and partial discharge characteristics of the PCB busbar are verified experimentally, which align with the design and evaluation results very well. The functionalities of all the individual SMs are experimentally verified by 55-min continuous operation under full voltage and rated output current. The functions of the SM were further confirmed in full-power tests of a downscaled 250 kVA MMC.

Although medium voltage dc (MVdc) power system is promising to provide flexible, robust, and highly power dense power distribution systems for various applications, the dc power systems suffer from short-circuit fault management issues. To solve the issue, a hybrid dc circuit breaker with piezoelectric actuated fast mechanical switch (FMS) and sequential metal oxide varistors insertion scheme has been developed. In the hybrid dc circuit breaker, to commutate fault current from the FMS to solid-state switches and then, keep zero current through the FMS, a gate voltage-based fault current commutation strategy was developed. The method regulates the current through FMS by adjusting the gate voltage of IGBTs and, thus, the voltage across the solid-state branch without switching of the IGBTs. The paper formulates a model of the de circuit breaker based on the gate voltage-based fault current commutation strategy. From the model, a sufficient condition for enabling the zero-current opening capability is identified, consequently determining the adjustment range of gate voltage-based method, i.e., the limits of voltage across the series of IGBTs. In addition, an analytical solution of the current through FMS is obtained and design guidelines for the gate voltage controller parameters are provided. The analytical solution matches SPICE simulation with detailed IGBT model very well, which verifies the effectiveness of gate voltage-based fault current commutation.

In this paper, we present a novel distributed state estimation approach in networked DC microgrids to detect the false data injection in the microgrid control network. Each microgrid monitored by a distributed state estimator will detect if there is manipulated data received from their neighboring microgrids for control purposes. A dynamic model supporting the dynamic state estimation will be constructed for networked microgrids. The optimal distributed state estimation, which is robust to load disturbances but sensitive to false data injected from neighboring microgrids will be presented. To demonstrate the effectiveness of the proposed approach, we simulate a 12kV three-bus networked DC microgrids in MATLAB/Simulink. Residual information corresponding to the false data injected from neighbors validates the efficacy of the proposed approach in detecting compromised agents of neighboring microgrids.

Power hardware-in-the-loop (PHIL) simulation is a technique whereby actual power hardware is interfaced to a virtual surrounding system, simulated in real-time, through PHIL interfaces making use of power amplifiers and/or actuators. A number of seemingly disparate interface algorithms (IA) have been proposed in the literature for achieving the virtual coupling between the simulated and physical portions of the system, with each presenting different strengths and shortcomings. In this work, a framework based on an architecture for bilateral teleoperation systems is described, which is suitable for the formulation of linear PHIL IAs, encompassing the majority of the existing IAs proposed in the literature. Formulations of a number of existing PHIL IAs are given in the context of the described framework. Requirements for achieving transparency with the IAs are described, and several of the existing IAs are discussed in terms of the framework, adherence to the transparency requirements, and performance. As the architecture also lends itself to the development of flexible IA modules for real-time simulators, the implementation and application of an IA module reflecting this architecture is also described.

An approach for testing the operation and coordination of medium-voltage dc solid state circuit breakers (SSCB) for shipboard power systems is described. For the considered application, the rate of rise of current during a short-circuit is limited primarily by a small cable inductance. This high rate of rise, coupled with the need to interrupt the current prior to exceeding the limits of the power electronic switches in the SSCBs, necessitates a coordinated protection scheme which can isolate the fault within a matter of microseconds. Challenges in such tests include the high-voltage, high current, high rates of change of current, and the interconnection of devices within a system. Testing of the SSCBs in a system context presents a challenge, as the MVDC system to which these are to be applied has not been realized in hardware. In order to verify the operation of the SSCBs within a system context, a combination of tests and analyses are employed, including off-line simulation, controller hardware-in-the-loop simulation, hardware testing of a single SSCB, and coordination testing with multiple SSCBs. Results are described for testing of 1 kV devices, but the approach is developed to allow for extension for devices of higher voltage ratings.

In this paper, we report on the utilization of advanced distributed control algorithms, deployed on physical controllers, for an Integrated Power and Energy System (IPES) energy management system. In addition, we provide an evaluation of the management system. Results from a hardware-in-the-Ioop experiment will be analyzed to show the effectiveness of the realtime control system. The goal of this paper is to provide valuable insights from a practical system controls the application of reasonable size and system complexity.

The area of modeling and simulation is a critical aspect in the basic research to commercialization and instantiation cycle. This paper reports on modeling and simulation in the context of verification, validation, and experimentation of power and energy systems and associated electrical apparatus via the utilization of power hardware in the loop (PHIL)-based strategies. PHIL is a powerful technique for testing and demonstration of systems in a rigorous and dynamic manner that is not achievable with other methodologies; however, it must only be conducted with foreknowledge of the technique and its challenges in order to realize its significant benefits. This paper reports on the state of the art in PHIL and its challenges and presents sample case studies illustrating its impact.

Three generations of medium voltage fault isolation devices (FID) for a power electronics based distribution system, the FREEDM System, are reported in this paper. In the Gen-I FID, three 6.5 kV silicon IGBTs are series connected to achieve 15 kV class distribution voltage blocking capability. Whereas in the Gen-II and the Gen-III FIDs, 15 kV Silicon Carbide (SiC) ETO devices are used. Since one single such device can meet the voltage withstand requirement, the operation losses as well as dimensions are significantly reduced. Future improvements in the Gen-III FID include the use of hybrid schemes and the development of symmetrical blocking high voltage SiC devices to further minimize the operation losses.

The use of real time digital simulation of large power systems is widely spreading due to its high precision result and increasing computing capability. However, in many cases, especially when large power system networks are to be modeled, the interconnection data and parameter data are available in flies which are used as input to simulation programs. Most transmission utilities use dynamic studies using PSS®E, PSLF or similar type of tools. Since most of the system data are available in PSS®E data format, it will be easier to develop an electromagnetic transient model if those data files can be used without putting much effort. Considering the benefit in huge savings in time, RTDS®Technologies Inc. has developed a conversion routine to generate transient model of power system network using the data files available in PSS®E. This paper discusses the conversion process and uses two test cases to verify the accuracy of the conversion tool. IEEE 39 bus test system and a notional 311 bus system were used for this purpose. Both steady state and transient test results of PSS®E and RSCAD model are then compared with each other. This paper also discusses the limitations and challenges of the conversion process, as well as potential solutions. In essence, this study evaluates the accuracy of model conversion from PSS®E to RSCAD for large power systems and highlights the lessons learned from the whole exercise.

Existing approaches to predicting tie strength between users involve either online social networks or location-based social networks. To date, few studies combined these networks to investigate the intensity of social relations between users. In this paper we analyzed tie strength defined as partners and acquaintances in two domains: a location-based social network and an online social network (Second Life). We compared user pairs in terms of their partnership and found significant differences between partners and acquaintances. Following these observations, we evaluated the social proximity of users via supervised and unsupervised learning algorithms and established that homophilic features were most valuable for the prediction of partnership.

This paper discusses the potential role Power Hardware-in-the-Loop (PHIL) testing can play in both actual testing and derisking laboratory experiments, and shows results obtained while preparing for MW-scale testing of new AC-DC converter technology. The step-by-step approach taken by moving through phases of modeling and simulation to PHIL experiments is described, and the real time simulation for the PHIL testing including Rest-of-System and setup of experiments is addressed. An AC/DC rectifier was successfully operated in PHIL up to several hundred kilowatt to derisk planned experiments for upcoming performance testing of AC/DC converters. The PHIL experiments used in this way are a crucial part in the commissioning process and allow confidence to be gained in proper setups before the actual converter becomes available for testing.

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.

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.

A reliable and secure communication network plays a significant role in Smart grid systems, which aims at coordinating generation, transmission, distribution, and consumption parts in power system. The scope of our work ranges from utility level to end consumption level. The major difficulties in this work can be summarized as follows: 1) Performance requirements from the viewpoint of network have not been clearly defined; 2) Model mapping from power system to communication networks is not straightforward. 3) Network performance has not been well-investigated. This paper proposes a communication network model for a typical program of smart gird. Moreover, application requirements, link capacity and traffic settings have been investigated. Simulation results validate the feasibility of this model and provide useful network performances which can satisfy both the non-real-time and real-time application requirements.

With hundreds of millions of users already today,virtual worlds will become an important factor in tomorrow's media landscape. In a virtual world, users are represented by so-called avatars. These avatars move around the virtual world, communicate with each other,and interact with the virtual world. The movements of these avatars can be tracked precisely, and useful information can be inferred from analyzing these movements. In this paper, we analyze a large data set (>200 million records) of position data describing the movements of avatars in the virtual world Second Life.The dataset was derived from in-world sensors that had been deployed beforehand, but also so-called bots can be used to gather such information. From this data, we can track usage patterns of avatars (and therefore users) overtime. We can also identify regions of high interest where a large number of users gather frequently (which would be important for planning advertising in the virtual world), and visualize this statistical analysis using heat maps. By combining the position data with information about the language spoken by the avatars, we can label these regions according to the language predominantly spoken there. Analyzing incidents of co-location of avatars over a period of time, we can automatically infer friends, and eventually social networks. Using additional metadata such as language we can label clusters in this automatically generated social network.

The economies of virtual worlds are driven by the exchange of virtual good and services. These goods are available in the form of image textures, 3D objects, and scripts. The theft or unauthorized use of these goods was and still is a serious problem for virtual world users and content providers. In our work we try to point out various aspects of IPR violations in virtual worlds and suggest a platform for detection inspired by plagiarism detection services in real world.