Medium voltage three-level converters for the grid connection of a multi-MW wind turbine (original) (raw)
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Medium Voltage Multilevel Converters for a Multi-MW Wind Turbine Grid Connection
Recent advances in the wind power technology have increased wind turbine power ratings to multi-MWs. This increase and recently introduced strict grid codes are spurring the utilization of full-scale medium voltage (MV) grid-side power electronics converters in wind turbines. In this study, for the grid connection of a hypothetical 6MW-3kV wind turbine, three-level (3L) configurations of NPC, FC, and HB VSCs are simulated for PF=0.9-1 and f c =650-1050Hz. The simulation results show their performance with respect to total harmonic distortion of current, switch utilization, switch losses, and loss distribution. Finally, these VSCs are compared with respect to the two most important criteria (power density and reliability) for the 6 MW wind turbine connected to a MV (>3kV) grid via a transformer.
Integration of wind energy sources into the distribution grid affects the voltage profile that could be stabilized through the grid reinforcement or limiting the active power injection. This paper presents a control strategy to regulate the voltage at point of common coupling (PCC) through reactive power exchange to the grid. The reactive power capability of the grid-connected hybrid multilevel converter is based on the voltage sensitivity of the distribution grid at PCC. A hybrid five-level multilevel converter referred as flying capacitor (FC) based active-neutral-point-clamped (ANPC) converter is considered. It is an arrangement of a three-level ANPC converter and a two-level cell. Also, a control strategy is proposed to regulate the FCs voltages of the gridconnected hybrid multilevel converter at their required values. The proposed FC control strategy provides extra freedom to regulate the dc-link capacitor voltages with dc-offset injection technique. Simulation studies demonstrate the performance of the proposed control strategies for the system considered.
IEEE Transactions on Industry Applications, 2014
In order to fulfill the growing demands from the grid side, the full-scale power converters are becoming popular in the wind turbine system. The Low Voltage Ride Through (LVRT) requirements may not only cause the control problems but also result in overstressed components for the power converter. However the thermal loading of the wind power converter under various grid faults is still not yet clarified especially at MW power level. In this paper, the impacts by three types of grid faults to a three-level Neutral-Point-Clamped (3L-NPC) wind power converter in terms of operating and loading conditions are analytically solved and simulated. It has been found that the operating and loading of converter under LVRT strongly depend on the types/severities of grid voltage dips and also the chosen control algorithms. The thermal distribution among the three-phases of converter may be quite uneven and some devices are much more stressed than the normal operating condition.
2012 IEEE Energy Conversion Congress and Exposition (ECCE), 2012
In order to fulfill the growing demands from the grid side, the full-scale power converters are becoming popular in the wind turbine system. The Low Voltage Ride Through (LVRT) requirements may not only cause the control problems but also result in overstressed components for the power converter. However the thermal loading of the wind power converter under various grid faults is still not yet clarified especially at MW power level. In this paper, the impacts by three types of grid faults to a three-level Neutral-Point-Clamped (3L-NPC) wind power converter in terms of operating and loading conditions are analytically solved and simulated. It has been found that the operating and loading of converter under LVRT strongly depend on the types/severities of grid voltage dips and also the chosen control algorithms. The thermal distribution among the three-phases of converter may be quite uneven and some devices are much more stressed than the normal operating condition.
Journal of Energy in Southern Africa, 2019
Developers and operators are interested in improving the reliability and reducing the associated costs of wind power plants (WPPs) because of the continuous increase in the power capacity of wind energy conversion systems (WECSs) and the increasing development of WPPs. The electrical subsystem of the WPP experiences the highest failure rate and constitutes a significant proportion of its total cost. Reliability of the WECS can be increased and its cost reduced by eliminating the wind turbine transformer from the electrical subsystem. This study gives a techno-economic evaluation of a five-level nested neutral point clamped (NNPC) converter topology for transformer-less connection of high- power WECSs. The approach entailed the calculation of reliability of five-level NNPC converter topology deployed in the grid-side of a WECSs. This method presents a mathematical formula for deriving the reliability of a five-level NNPC converter topology by using the reliability block diagram and r...
A four‐leg three‐level neutral‐point‐clamped inverter
A kind of multiconverter wind power conversion system with HVDC transmission based on VSCs is discussed for 10 MW offshore wind turbine. HVDC transmission is implemented by multiple modular VSCs that are serially connected by means of multiphase PMSG in the nacelle of wind turbine and multiwinding transformer in onshore power substation. As basic building blocks, power loss properties of different VSC topologies are compared. Then, a traditional three-level neutral-point-clamped voltage source inverter (3L-NPC VSI) mixed with an added FC leg is proposed for HVDC transmission. The added FC leg is used to deal with the intrinsic neutral-point imbalance issue of 3L-NPC VSI, including voltage fluctuation and DC drift. Four kinds of different balance control strategies are presented, and their performances are compared. Simulation and experiment results verify the effectiveness of the control strategies. Finally, it is proved that the power loss property of four-leg 3L-NPC VSI is better than the traditional 2L VSI regardless of additional power loss offered by the added FC leg
Grid-Connection Control and Simulation of PMSG Wind Power System Based on Three-Level NPC Converter
The technology of the high-voltage and high-power three-level converters are applied to the system of direct-drive wind power, and the converter structure is the dual three-level with back-to-back structure. The generation-side converter guarantees the point tracking of the maximum power and the smooth operating of the generator through the double-loop control scheme of the maximum ratio of torque to current. The grid-side converter adopts the vector control of grid voltage orientation, realizing the decoupling control of the active and reactive power. Meanwhile, the constant DC power can be ensured and the working state of the converter can be maintained in a unity power factor state. The simulation results show that the use of the dual three-level converter not only realizes the dynamic control of the system but also ensures the high quality of the electricity delivered to the grid.
International Journal of Circuit Theory and Applications, 2019
In this study, a comprehensive control scheme for cascaded H-bridge multilevel inverter (CHBMLI)-based grid integrated bulk wind energy conversion system (WECS) addressing the problem of deviation of wind speeds among windmills like a partial shading condition of PV system is presented. The proposed control scheme uses independent dc links with reduced voltages that makes such a topology an ideal candidate for high and medium power WECS with improved reliability. Inconsistency of wind speeds at each turbine causes distinct voltage conditions among the isolated dc links of the CHBMLI H-bridge cells (HBC) leading to unstable power generation. The projected scheme along with maximum and efficient energy conversion has the ability of dc link capacitor voltage balancing in each HBC of CHBMLI during the above said power generation mismatch conditions and also maintains power quality in the grid side voltage and injected currents as per standards. Moreover, the modelling analysis of the adopted CHBMLI for the grid integrated WECS application has also been derived. The system performance under inconsistent wind speed environment has been tested and analysed by using MATLAB simulation and validated by using FPGA-based real-time simulator (Opal-RT-OP5700). KEYWORDS dc-link capacitors balancing, grid-connected cascaded H-bridge multilevel inverter, mathematical modelling, power quality, wind energy conversion system
International Journal of Engineering Research and Technology (IJERT), 2014
https://www.ijert.org/an-advanced-full-bridge-three-level-dc-dc-converter-with-voltage-balancing-control-technique-for-wind-power-systems https://www.ijert.org/research/an-advanced-full-bridge-three-level-dc-dc-converter-with-voltage-balancing-control-technique-for-wind-power-systems-IJERTV3IS080933.pdf This paper presents an advanced full-bridge three level DC-DC converter and its control for wind power systems. A passive filter is used to improve the performance of the proposed converter. The presence of passive filter reduces the voltage stress of the medium frequency transformer in the AFBTL DC-DC converter. A modulation strategy is proposed for the AFBTC DC-DC converter, which provides two operating modes. Furthermore, a voltage balancing control of the wind turbine based on the AFBTL DC-DC converter in a DC-grid system is presented. Finally, the simulation results for the proposed AFBTL DC-DC converter with 1KW output power range is presented and obtained merely to the theoretical values. Keywords-Full bridge three level (FBTL) converter, half bridge three level (HBTL) converter, permanent magnet synchronous generator (PMSG), DC-DC converter, wind turbine, voltage balancing control, pulse width modulation (PWM). I INTRODUCTION In general, the DC grid provides advantageous things such as absence of reactive power, harmonics and power factor, which gives an effective solution for the power collection system for the growing power demand in the present days. The offshore wind turbines are mostly connected to a DC grid to deliver DC power to a medium or high DC voltage networks. To minimize power delivery and the DC connection, a high efficient DC-DC converter is required. Generally, the voltage level of the DC network is much higher than the input voltage level of the DC-DC converter. For this reason, a medium frequency transformer (MFT) with a range of hundreds of hertz to several kilohertz operating frequency is used for the DC-DC converter. In addition to providing the boosted output voltage, it provides the galvanic isolation between source and grid. (1a) (1b) Girija, P.
This paper thinks about the modeling switching strategy and control conspire for impartial point clamped converter sustained into matrix. Design and Analysis of PWM 3– level inverter for power quality mix of wind power in to network to interface with the medium voltage framework. Inverters are arranged into single level inverter and multi-level converter. Multi-level converter has a ton of favorable position to single level inverters have least harmonic twisting, lessened EMI/RFI creation and keep running on very surprising voltage levels. Multi-level inverter is utilized for a few mechanical applications, for example, power filters, static var compensators and drives applications. The disadvantages are the disconnected power supplies required for every last one of the phases of the multi-level converter and costlier, extreme to oversee in programming. This venture goes for the reproduction investigation of 3-ɸ single level and multi-level convertor. The part of convertor in dynamic power channel for harmonic elimination is considered and reproduced in MATLAB/SIMULINK. Right off the bat, the 3-ɸ framework with non-straight loads is demonstrated and their trademark is resolved. Also, the dynamic power filters are making with the convertor and fitting switch regulation technique (PWM technique) to hold out harmonic elimination.