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This paper deals with the interruption scheme designed using Vacuum Circuit Breaker (VCB) based on zero crossing characteristics, implemented electromechanically for High Voltage Direct Current (HVDC) system. The operation is carried out using Mechanical scheme as it has minimum energy loss in comparison to Solid-State and Hybrid schemes. The Mechanical scheme consists of series connection of multiple...
This paper proposes a new high-voltage Pulse Generator (PG), fed from low voltage dc supply Vs. This input supply voltage is utilized to charge two arms of N series-connected modular multilevel converter sub-module capacitors sequentially through a resistive-inductive branch, such that each arm is charged to NVS. With a step-up nano-crystalline transformer of n turns ratio, the proposed PG is able...
To improve the reliability of modular multilevel converter (MMC), the fault submodules must be isolated rapidly. In this paper, a new fast fault diagnosis method is proposed containing two steps: fault detecting and fault locating. Fault detection step finds failures by improved predictive model which detects the fault by comparing the difference between the predictive value and the measured one of...
In this paper, an asymmetric mixed MMC topology of multilevel converter for bipolar HVDC transmission systems is introduced. Among the existing MMC topologies for the bipolar HVDC systems, the asymmetric mixed MMC topology provides the benefits of: a lower number of submodule cells, fewer switching devices and lower conduction losses. Furthermore, the HVDC based on asymmetric mixed MMC can be flexibly...
Modular multilevel converter (MMC) has been proved a prospective topology in high voltage and high power occasions. Hybrid MMC mixed with half-bridge (HB) and full-bridge submodules (FBSMs), which achieves a good tradeoff between power devices quantity and dc short circuit fault handling capability, attracts extensive attention. In this paper, the characteristics of SM capacitor voltage ripples are...
Nowadays, research on the reliability improvement of T-type three-level inverters is studied as an important issue. In this paper, a novel fault tolerant control strategy based on model predictive control (MPC) is proposed for open-circuit faults in switch devices. When an open-circuit fault occurs to neutral-point switches, the impossible switching states of zero- and small-voltage vectors should...
A short-circuit fault protection strategy based on the direction of bus-side capacitor discharge current for a high-surety power supply, known as Super Uninterruptable Power Supply (Super UPS), is studied in this paper. It consists of multiple energy sources and storage components. All energy sources and storage components are connected to a common DC bus through converters in the system. If a short-circuit...
This paper proposes a transformer based self-starting boost converter for thermoelectric energy harvesting, which operates even when polarity inversion of thermoelectric generator (TEG) occurs. TEG is used to convert thermal energy into electrical energy. Due to the Seebeck effect, an open circuit voltage of the TEG is proportional to the number of thermocouples in series and to the temperature difference...
This paper proposes an adaptive DC-bus stabilizer for single-phase grid-connected voltage source converter (VSC) with small-scale renewable energy integration. To enhance converter's power density, the conventional active power decoupling (APD) techniques were adopted to reduce the DC capacitance by compensating the inherent second-order harmonic power ripples in the single-phase VSC. However, it...
A low voltage ride-through solution for an indirect three-level matrix converter based open-end winding drive is demonstrated. The proposed method uses the input filter capacitors to exchange the inertial energy from the motor and thereby maintain the flux in the motor during grid fault conditions. The input filter capacitors act as the voltage source for inverters during the fault. Ride-through is...
Half-bridge (HB) modular multi-level converter (MMC) based bipolar HVDC transmission systems can be employed to transfer bulk power over long distances with high reliability and flexibility. However, this configuration exhibits special fault behaviors that should be taken into account during its design stage. For instance, a single-phase-to-ground fault at the valve-side of the HB-MMCs will lead to...
This paper proposes an enhanced modular multilevel converter based battery energy storage system (EMMC-BESS) for interfacing low voltage batteries to the medium or high voltage grids. Besides the distributed battery integration functionalities and the inherited advantages of traditional MMCs, EMMC-BESS also provides the DC fault handling capability. Based on analysis of operation principles, the control...
This paper proposes a new modular multilevel converter with symmetric bidirectional DC fault blocking capability for high voltage direct current transmission systems. The new modular multilevel converter is composed of novel submodules, which is developed from a three-level T-type converter combined with some clamp circuits. The proposed novel submodule can output three voltage levels with six IGBTs,...
This paper presents theoretical and experimental discussions on low-voltage-ride-through (LVRT) operation of a modular multilevel single-delta bridge-cell (SDBC) inverter intended for utility-scale photovoltaic (PV) systems. As the penetration of distributed generation from renewable energy sources connected to medium- and high-voltage grids increases, grid-tied inverters progressively need to abide...
This paper proposes a novel input-series output-parallel (ISOP) current-fed modular dual-active-bridge (CF-MDAB) dc-dc converter for medium-voltage dc (MVDC) system application. The proposed converter exhibits favorite features of DAB converter such as galvanic isolation, soft-switching condition and small passive components. Compared to ISOP DAB converter, the proposed topology has direct dc current...
Fault tolerant operation can significantly improve the reliability of a Modular Multilevel Converter (MMC), but the precondition is that a fast and accurate fault detection and localization method has been embedded into the MMC control system. This paper proposes a fault diagnosis method used in a distributed control architecture, which makes the local controllers capable of identifying the switching...
In this paper, a method to diagnose and identify the open-circuit faults of IGBT for a six-level hybrid inverter (6L-HI) is proposed, which is based on the signals of the inner device voltages, the flying capacitor voltages and the phase currents of the inverter. Since the flying capacitor voltage sensors and the output current sensors are already employed for the inverter operation, only one additional...
Hybrid modular multi-level converter (Hybrid MMC) topology, consisting of both half-bridge (HB) and full-bridge (FB) submodules, is suitable for HVDC application as it combines the advantages of both HB-MMC and FB-MMC. This paper focuses on the control aspects of hybrid MMC with the objective of limiting DC fault current. It is also controlled to exchange reactive power with the AC grid during DC...
A novel Medium Voltage Direct Current (MVDC) circuit breaker consisting of a High-Speed Switch(HSS) and a bridge-type commutation branch, which is based on current injection, is proposed and analyzed in this paper. The commutation branch of this design adopts bridge type, which can break bidirectional fault current rapidly by controlling thyristors. Meanwhile, after fault current is commutated to...
Research on direct current (dc) interruption has grown in recent years, driven by increased interest in using high voltage direct current (HVDC) for large power transmission and future grids. In fact, dc interruption poses particular challenges to protection devices and circuit breakers and new technologies are needed to meet the requirements of future HVDC grids. In this paper we review some of the...
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