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This paper is introducing a new method of operation for a series resonant converter, with intended application in megawatt high voltage DC wind turbines. Compared to a frequency-controlled series resonant converter operated in sub-resonant mode, the new method (entitled pulse removal technique) allows the transformer design to be determined by peak load and maximum switching frequency, while still...
This paper is devoted to load-carrying capacity of an induction machine under voltage containing subharmonic injection. The permissible machine load is investigated for various frequencies of voltage subharmonics. The results of calculations are presented for a totally-enclosed induction cage machine of rated power 5.5 kW.
Four DC/DC converters are analyzed and compared with respects to availability, efficiency, ratings, repair costs and power density. Intended application is offshore wind farms with MVDC power collection. The selected topology is a new series resonant converter, which offers 99% efficiency across the entire operational range, but needs components designed for high voltage stress.
Contactless power transfer (CPT) is an emerging topic which relies in high frequency resonant inverters to transfer power from a transmitter to a physically separated receiver inductively. Capacitive compensations on both the primary and secondary sides of a loosely coupled transformer are usually employed in recent researches in order to enhance the power transfer capability and the system efficiency...
Microinverters connect a single photovoltaic (PV) module to the grid, and therefore require a high voltage step-up conversion ratio. This is usually achieved in a two-stage approach with a step-up dc-dc converter followed by a step-down inverter. More recently single-stage step-up inverters have been proposed under the assumption that less stages improves efficiency. This paper compares these two...
In the paper the design of an IPMSG for small wind turbines is presented. Based on classical construction of induction motor (IM), the internal permanent magnet generator (IPMG) was projected. Parameterization and sweep analysis of the rotor geometry was done in the finite element analysis (FEA) software, to obtain the maximum back electromotive force (BEMF). Based on this analysis, one case was chosen...
The control of multiterminal HVDC systems based on local variables has shown a better performance, in terms of dynamical response and implementation simplicity, than constant DC voltage and droop control. However, power oscillations can be produced due to the interaction among different HVDC stations. In this paper, a modified control logic for this type of control is proposed in order to reduce the...
This paper presents a broad bandwidth (DC to ∼50MHz) current sensor. It is inserted in the current conducting path and it has a low insertion inductance of about 1 nH due to a coaxial housing. The measurement procedure is based on HOKA principle using TMR sensors for the low frequency capture and a Rogowski coil for the high frequency capture. The HOKA principle combines both by analog signal processing.
A 240 kVA, 10 kHz medium-frequency transformer (MFT) to be used in MV DC/DC conversion was developed. The transformer has separately dry-cast windings and was designed for DC system voltages up to 50 kV. For dimensioning and optimization, a MATLAB-based tool was used, containing fast models for electromagnetic, insulation, and thermal design, as well as losses in windings and core. Starting from a...
With commercial operation of the first Chinese Maglev line, lifetime prediction of power devices in Maglev choppers becomes a crucial topic. This paper adopts a mission profile of one typical Maglev chopper for lifetime prediction. A test rig is built for the IGBT/Diode case temperature measurement. Using look-up tables of IGBT/Diode losses, an accurate electro-thermal model can be established. The...
Almost all power electronic converters require magnetic devices and some properties of the converters can be controlled with magnetics. New magnetic materials enable implementation of magnetic control of converters also in high switching frequency applications. The presented paper gives an overview about controllability of magnetic devices in theory and practice, simulation approaches and examples...
This paper presents a new and low-cost thermal interface assembly between a printed circuit board and a heat-sink that provides electric isolation on the whole surface, and thermal conduction where needed. The assembly relies on the association of an isolation and a spacer layer and a thermo-conductive gel. The bill of material is 8 times lower than a best in class thermal pad, and equivalent thermal...
Power system restoration takes place where power systems experience a blackout and might be splitted into several islands with limited number of black start units. The main challenge of the restoration process is to keep both frequency and voltage within allowable limits while restoring the network through energizing lines and transformers as well as load pickup. The load pickup scheme is determined...
Hybrid Microgrids are currently of great interest and are considered the distribution and transmission systems of the future, because they enable the coexistence of the AC microgrids and DC microgrids. This paper deals with the implementation of a new power management algorithm of the power converters that form part of the hybrid microgrid of Distributed Generation. The hybrid microgrid consists of...
This paper presents a sensorless starting procedure for a soft starter driven IE4 direct on line permanent magnet synchronous motor (PMSM). First, the initial position of the rotor is determined using a pulsating current space vector. Subsequently, the motor is started from standstill by the soft starter from a known position. The following firing sequences are calculated on the basis of the flux...
The press-pack IGBT (PPI) modules are characterized by design of double-sided cooling, solderless joint and wire-bondless contact. These features allows them to be utilized in the field where power density and reliability are demanding, especially in multi-MW wind turbine applications. However, owing to the press-pack structure, there is parasitic inductance which can't be neglected in the mechanical...
Microgrid systems provide benefits to strong, weak and remote power grids. Using multiple sources with differing characteristics and native constraints makes it a challenge to control the microgrid. Compared to the traditional central controller approach, a decentralized microgrid controller architecture has benefits including resiliency to asset and communication failures, which are experimentally...
This paper describes a transformerless STATCOM (Static synchronous compensator) based on the MMCC-SDBC (modular multilevel cascade converter — single-delta bridge-cells) for independent control of positive- and negative-sequence reactive powers. A three-phase 200-V 6-kVA experimental system is designed, constructed and tested to verify the effectiveness of the topology and the control method including...
The traditional particle swarm optimization (PSO) algorithm has been used to optimize inverter controller parameters. However, there are some disadvantages when the quantity and optimization interval of inverter controller parameters increase, such as easily falling into local optimum, and optimization convergence problems. An improved PSO algorithm with multi-swarm and multi-velocity (MMPSO) is proposed...
This paper investigates the fundamental characteristics of contactless power transfer in seawater. The influence of seawater on contactless power transfer via magnetic resonant coupling method is experimentally examined. The experimental results show that the transmission efficiency decreases about 5% in seawater compared to that of in air.
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