Search

The performance of the power converter bus bar is not only determined by its normal operational design, but also related to its fault ride-through ability consideration. Conventional busbar design only takes the normal operational performance into account. This article proposes an optimal busbar design method for the modular multilevel converter (MMC) submodule, which takes both the normal and fault ride-through performance into account. The normal operational design is to realize low stray inductance and balanced inductance distribution between parallel capacitor branches. The basic structural design guideline for the MMC submodule is presented. Taking both the stray inductance and manufacturing cost into account, the optimal layout of the busbar is proposed. To balance the capacitor branch currents, the mathematical model of the busbar stray inductance is built. The influence of different busbar structures on the stray inductance is analyzed. The analysis is verified by simulation results. To improve the fault ride-through capability, special consideration is taken into account to reduce the thermal and mechanical stress at the weakest point. Simulation and experimental results verify the efficacy of the proposed approaches. [ABSTRACT FROM AUTHOR]

Power conditioning system (PCS) is the crucial component of superconducting magnetic storage system (SMES), which determines its power control performance and ability. This paper investigates the feasibility of applying Z source converter (ZSC) as the PCS for SMES. A ZSC-based PCS (ZSC-PCS) for SMES is presented, parameter design methods are analyzed, and a novel minimum power losses control scheme is proposed. By dynamically regulating open zero vector duty ratio to its minimum required level, the ZSC-PCS can enlarge both active and reactive power capability of SMES with lowest power losses. The feasibility of the proposed approach is verified by the experimental results on a kVA scale prototype. [ABSTRACT FROM AUTHOR]

A low-voltage ride-through (LVRT) strategy for a doubly fed induction generator (DFIG) with a switch-type fault current limiter (STFCL) is presented in this paper. The STFCL is composed of fault-current-limiting inductors, isolation transformers, a diode bridge, a semiconductor switch, a snubber capacitor, and a fault energy absorption bypass. The presented STFCL can insert fault-current-limiting inductors in series with the stator branches on occurrence of a grid fault, which can limit the rotor overcurrent and weaken the rotor back electromagnetic force voltage simultaneously. The safety and controllability of the rotor side converter can thus be guaranteed. The STFCL can also absorb the excessive energy stored in the stator during LVRT with the fault energy absorption bypass so as to prevent the semiconductor devices from overvoltage. The feasibility of the proposed approach is validated by simulation studies on a typical 1.5-MW wind-turbine-driven DFIG system. The validity of the proposed approach is further verified by the experimental results on a 2-kW DFIG prototype. [ABSTRACT FROM PUBLISHER]

A multicell fault current limiter (MCFCL) is proposed in this paper. The MCFCL is composed of multiple fault current limiting cells. Each fault current limiting cell consists of a fault current limiting inductor and a power electronic module. The proposed MCFCL has the flexibility in expanding the operation voltage by increasing the number of fault current limiting cells. The MCFCL has excellent static and dynamic voltage equalizing capability between different cells, which makes it highly reliable. The MCFCL utilizes the fault energy absorption bypasses instead of varistors to prevent overvoltages across the semiconductor devices, which makes it able to repeat fault current limitation multiple times in a short time interval. Moreover, the MCFCL has rather high efficiency, which is expected to be no less than 99.9% with appropriate semiconductor devices. The operational principles and parameter design methods of the MCFCL are presented. A medium-voltage prototype is developed and tested. The simulation and experimental results are presented to clarify the theory and feasibility of the proposed approaches. [ABSTRACT FROM PUBLISHER]

Two major problems that are faced by doubly fed induction generators are: weak low-voltage ride-through capability and fluctuating output power. To solve these problems, a superconducting fault-current limiter-magnetic energy storage system is presented. The superconducting coil (SC) is utilized as the energy storage device for output power smoothing control during normal operation and as a fault-current limiting inductor to limit the surge current in the stator or rotor during the grid fault. The SC can also weaken the rotor back electromotive force voltage, and thus enhance the controllability of the rotor-side converter (RSC), which helps to protect both the RSC and the gearbox. Simulation results verify the efficacy of the proposed approaches. [ABSTRACT FROM PUBLISHER]

A 0.5 MVA/1 MJ superconducting magnetic energy storage system (SMES) has been installed in a superconducting power substation. The SMES is designed to compensate active power fluctuations, current harmonics and reactive power of the downstream load. The system configurations and control strategies are described. Experimental and field test results show that the proposed SMES can effectively improve the power quality of the power system. [ABSTRACT FROM PUBLISHER]

A superconducting magnetic energy storage system (SMES), with stored energy of 1 MJ and compensation power of 0.5 MVA, has been developed successfully, and now is operating at the world's first superconducting power substation at Baiyin National High-Tech Industrial Development Zone, Gansu Province, China. The SMES employs a high Tc superconducting magnet, which consists of 44 pancakes, operates at 4.2 K in liquid helium, and is cooled down by 4 G-M cryo-coolers. The SMES connects to a 10.5 kV power grid by the use of a power conversion system. Since 16 February, 2011, the SMES has been operating reliably, and providing good-quality power for three companies. [ABSTRACT FROM PUBLISHER]

With the increasing depletion of fossil fuels and growing environmental pressure, the mankind has got known the need to vigorously develop the renewable energy and the energy-saving technology. The high Tc superconducting (HTS) power technology will be very helpful to enhance the stability, reliability, and efficiency and transmission capacity of the power grid which would be dominated by the renewable energy. In this paper, we will report the installation and operation of a 10 kV HTS power substation which includes a 75 m/1.5 kA HTS power cable, a 10 kV/1.5 kA HTS fault current limiter, a 1 MJ/0.5 MVA high Tc SMES and a 630 kVA/10 kV/0.4 kV HTS power transformer. [ABSTRACT FROM PUBLISHER]

It is expected that superconducting technologies will play an important role in the future smart grid, because the application of superconductor technologies in the power grid can decrease power losses, relieve overload, avoid higher levels of transmission voltage, increase power transmission capacity, and improve power quality and grid stability. In recent years, high temperature (high-Tc) superconducting power technologies have achieved remarkable progress. High temperature superconducting (HTS) power equipment, such as HTS power cables, HTS transformers, high-Tc superconducting fault current limiters (SFCL), and high-Tc superconducting magnetic energy storage devices (SMES) have been demonstrated in the power grids of many countries. With the development of HTS power equipment, the construction of a HTS power substation is ready. In China, a 10.5 kV HTS power substation is under construction in Baiyin city, Gansu province. The substation integrates a HTS power cable, a HTS transformer, a HTS fault current limiter, and a high-Tc SMES. All these HTS power devices, which were previously developed by the Institute of Electrical Engineering (IEE), Chinese Academy of Sciences (CAS), have been demonstrated to operate for a long time in the commercial power grid. In this paper, the design and constructing progress of the HTS substation are introduced in detail. [ABSTRACT FROM AUTHOR]