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This paper proposes an effective control scheme to improve the transient behavior of VSC-based energy storage systems facing energy saturations. This control is aimed to reduce abrupt transients following energy saturations of the storage device. The WSCC 9-bus test system is used for validating and discussing the proposed controller. In particular, the dynamic response of a battery energy storage...
In the near future, transmission grids will include an increasing share of directly connected voltage source converters. These systems should be able to support the utility grid autonomously. The present paper reviews the most popular approaches to address the challenge of proper load sharing amongst multiple parallel inverters applied to the utility grid case. Originally developed for Microgrid or...
In this paper, a communication-assisted protection scheme is proposed for medium voltage dc (MVDC) distribution networks. MVDC grids are applicable for connection between microgrids, upgrading the transmission capacity of ac lines by the conversion to dc, and integration of renewable energy systems to the distribution grids. However, protection issues are one of the main challenges in the development...
Design of voltage source converters (VSC) for high-voltage direct current (HVdc) systems requires extensive simulation tools that are accurate and reliable. Before the installation of VSC-HVdc links, different simulation-based studies need to be performed by different parties and using different electromagnetic transient (EMT) simulation platforms. Previous work shows that even with a pedantic re-implementation...
Protection scheme for AC transmission systems are well understood and matured. On the other hand, DC system is still facing a challenge in developing proper protection scheme because of its natural characteristics. A protection scheme, which utilizes some of the developed techniques for AC system, and modified to suit the DC system characteristics, is proposed in this paper. The scheme is based on...
Direct current transmission based on Voltage Source Converters (VSC-HVDC) has a number of advantages compared with traditional HVDC systems. However, VSC-HVDC systems are subjected to high short circuit currents due to faults in the DC line, which may contribute negatively to the dissemination and advances of this technology. In this context, this paper analyzes the impact of superconducting fault...
This paper studies the methodologies for developing dc fault tolerant and highly efficient VSC converter. Building on a recently proposed LCL-VSC converter, which suffers from low efficiency at partial load, an operating strategy of switchable capacitor banks instead of fixed central capacitor is proposed to improve the efficiency. A theoretical framework is presented to enable LCL-VSC to achieve...
The fast development of wind power technology makes the application of DC transmission network increasingly wide and salient. Accordingly, the fault analysis and fault protection strategy for DC system become very significant. This paper introduces a simple DC system topology structure which is suitable for the power transmission of wind farms, and the fault characteristics of the DC system against...
This paper presents an integrated control and switching scheme for a grid-connected modular multilevel converter (MMC). The control consists of the conventional vector control (outer PQ control, inner line current control) used in two-level voltage source converters (VSCs) and additional circulating current mitigation control. Circulating currents in a modular multilevel converter (MMC) will be eliminated...
The paper investigates the applicability of averaged-value models (AVM) for modular multilevel converters (MMC) operating in a voltage sourced converter based high voltage dc (VSC-HVDC) grid. The AVM models are benchmarked by comparison with a detailed electromagnetic transient (EMT) model of the grid including a full-detail MMC model. Analysis results show that the AVM is only effective as long as...
In a droop-controlled High Voltage Direct Current (HVDC) grid, the line voltage drops throughout the system influence the voltage control. This paper introduces and compares five distinct methods for establishing droop setpoints in order to restore the voltage profile after a contingency and evaluates the ability of these methods to track the setpoints. Furthermore, the influence of the network and...
In this paper, the operation of Voltage Source Converter (VSC) based Multi-Terminal DC (MTDC) transmission system consisting of three different power converter topologies is evaluated. The high frequency isolated modular converter is used as the VSC configuration for two terminals. The Modular Multi-level Converter (MMC) and three-phase AC/DC converters are also used as the VSC configuration for the...
This paper introduces a DC transmission grid with fault tolerant inductor-capacitor-inductor (LCL) voltage source converters (VSCs) and using slow protection system based on mechanical DC circuit breakers (CBs). LCL VSC inherently regulates DC fault current to levels that converter can sustain for prolonged periods which avoids IGBT tripping and brings significant advantage in security and reliability...
If distributed generators are introduced on a large scale to the power system, various impacts on the power system are expected. For example, difference between power supply and power demand is occurred in low-voltage distribution system. Digital Grid can solve these problems by performing a power interchange between the power systems. In this paper, we conducted verification and evaluation for Digital...
Power system operates close to its operational limit to achieve a higher level of utilization of the grid infrastructure. As a result, its transient behavior is of great importance to prevent violation of the operation limits. This paper proposes an internal model control (IMC)-based approach for voltage-sourced converters (VSC) to improve their dynamic behavior. This IMC controller is designed based...
Many European countries have taken steps toward a Supergrid in order to transmit large amount of intermittent and remote renewable energy over long distance to load centers. In the US, as the expected increase in renewable generation and electricity demand, similar problem arises. A potential solution is to upgrade the transmission system at a higher voltage by constructing a new overlay grid. This...
This paper presents the control and integration of a smart energy storage system (SESS) to a permanent magnet synchronous generator (PMSG) wind power plant. For the purpose of long-term energy management the fuel cell/electrolyzer (FC/ELZ) is utilized in the SESS, whereas the ultra-capacitor is dedicated to the SESS in order to compensate for the short-term transient energy fluctuations caused by...
This paper analyzes the response of conventional protection schemes (Line current Differential and Mho Distance elements) and the supervisory elements associated with those protective elements in commercial relays for Type 3 (Doubly Fed Induction Generator based) grid integrated wind farms. The response of line protection elements and their supervisory elements are analyzed using real time by hardware-in-the-loop...
This paper presents a PMU-based state estimation algorithm that considers the presence of voltage source converter-based high voltage direct current (VSC-HVDC) links. The network model of a VSC-HVDC link with its control modes is developed and then combined with an AC model to accomplish a hybrid AC/DC network model. The measurement model in this algorithm considers the properties of PMU measurements,...
This paper presents implementation of a two stage three phase PV-grid interfaced system with a three phase VSC which has been utilized as a multifunctional device. Adaptive noise reduction technique is used to control multifunctional VSC which transfers the active power from PV system to the grid and also works as an active power filter (APF) to improve power quality at AC mains. The control algorithm...
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