A new three-phase 5-level current-source inverter

The new three-phase 5-level current-source inverter (CSI) proposed in this paper was developed by connecting three separate single-phase 5-level CSIs in series, and its operational principle was analyzed. There are two major problems existing in current-source multilevel inverters, one is the complex PWM control method (2-logic to 3-logic conversion), and the other is the problem of current-unbalance between different levels. A simple current-balance control method via DC current feedback is applied in each single-phase 5-level CSI cell to implement the current-balance control between different levels. And to reduce the output current harmonics, POD PWM control technique was used. Simulation and experimental results showed that this new three-phase 5-level CSI topology operates correctly.

A 6-switch single-phase 5-level current-source inverter

The new 6-switch single-phase 5-level current-source inverter proposed in this paper was developed by properly simplifying the traditional 8-switch single-phase 5-level current-source inverter, and its operational principle was analyzed. Just like the problem of voltage-unbalance between different levels existing in voltage-source multilevel inverters, a similar problem of current-unbalance between different levels whether for the 8-switch single-phase 5-level current-source inverter, or for the new 6-switch 5-level current-source inverter also exists. A simple current-balance control method via DC current feedback is presented here to implement the current-balance control between different levels. And to reduce the output current harmonics, PWM control technique was used. Simulation and experimental results showed that this new 6-switch topology operates correctly and that the balance-inductor can almost equally distribute the total DC current.

Novel control scheme for 3-phase PWM current-source converters under unbalanced source voltage conditions

Under unbalanced source voltage supply, considerable output second harmonics and input low-order harmonics in 3-phase PWM current-source converters (PWM-CSC) are generated. This paper proposes a new deadbeat controller based on compensation for unbalanced source voltage and current. With the proposed scheme, the second harmonics of the output current are eliminated and low-order harmonics of the source current are reduced effectively. Simulation and experimental results con- firmed the feasibility of the proposed method.

Topology for current-source grid-connected inverter with improved effciency and pulse width modulation control strategy

A novel topology of the current-source grid-connected inverter is proposed based on the immittance converter theory. A control strategy of sine-sine pulse width modulation （PWM） is studied. Compared with the traditional current-source inverter, the power frequency inductors and power frequency transformer are replaced with high frequency inductors and a high frequency transformer. Thus, the proposed inverter has advantages of small volume, low cost, low total harmonic distortion （THD）, low power losses, high power factor （PF） and simple control. Furthermore, grid voltage cannot influence output current of the grid-connected inverter and the current-source inverter with a high PF that approaches one has been realized. Finally, validity of the theory analysis and feasibility of the control scheme are shown by simulation and experimental results.

Superconducting Magnetic Energy Storage Integrated Current-source DC/DC Converter for Voltage Stabilization and Power Regulation in DFIG-based DC Power Systems

Unpredictable power fluctuation and fault ridethrough capability attract increased attention as two uncertain major factors in doubly-fed induction generators(DFIGs)integrated DC power system.Present solutions usually require complicated cooperation comprising multiple modules of energy storage,current control,and voltage stabilizer.To overcome the drawbacks of existing solutions,this paper proposes a superconducting magnetic energy storage(SMES)integrated currentsource DC/DC converter(CSDC).It is mainly composed of a current-source back-to-back converter,and the SMES is tactfully embedded in series with the intermediate DC link.The proposed SMES-CSDC is installed in front of the DC-DFIG to carry out its dual abilities of load voltage stabilization under multifarious transient disturbances and power regulation under wind speed variations.Compared with the existing DC protection devices,the SMES-CSDC is designed on the basis of unique current-type energy storage.It has the advantages of fast response,extensive compensation range,concise hardware structure,and straightforward control strategy.The feasibility of the SMESCSDC is implemented via a scaled-down experiment,and its effectiveness for DC-DFIG protection is verified by a large-scale DC power system simulation.

A power conversion system for PMSG-based WECS operating with fully-controlled current-source converters

We propose a new power conversion system for a permanent magnet synchronous generator(PMSG) based grid-connected wind energy conversion system(WECS) operating with fully-controlled back-to-back current-source converters. On the generator side, two independent current-source rectifiers(CSRs) with space-vector pulse width modulation(SVPWM) are employed to regulate and stabilize DC-link currents. Between DC-link and the electrical grid, a direct-type three-phase five-level current-source inverter(CSI) is inserted as a buffer to regulate real and reactive power fed to the grid and thus adjusts the grid side power-factor. We also present a current-based maximum power point tracking(MPPT) scheme, which helps the generator extract the maximum power through closed-loop regulation of the generator speed. By applying the multilevel modulation and control strategies to the grid-side five-level CSI, a multilevel output current waveform with less distortion is produced, and the bulk requirement of the output capacitor filter to eliminate the harmonic current is reduced. All the proposed concepts are verified by simulation models built in a PSIM environment.

Analysis on Application of a Current-source Based DFIG Wind Generator Model

Models for simulation are vital for the authenticity of the simulation.Modeling doubly fed induction generation(DFIG)for power system stability analysis has attracted a great deal of research interests in the past few years due to the wide applications of DFIG in wind power generation.The models developed by the wind generator manufacturers are not only complicated,but also proprietary and very specific to their own products.Many simplified generic models have been proposed.Among them,the current-source based model is most widely used for power system stability analysis.The validation work on this model so far has been based on the selected simulation scenarios or limited real measurements.However,there has been no systematic and theoretic analysis on the validity of the current-source based model,which may cause inappropriate applications of this type of model in real engineering practices.This paper presents the conditions for using the current-source based model for power system stability analysis;then examines the model’s validity under symmetrical and asymmetrical fault conditions.Our practices for modeling and validating a real wind farm in North China confirm the validity analysis of this work on the current-source based DFIG model.

Simulation for accelerator dynamic power supply based on current-source PWMrectifier

Purpose The booster power supply of high-energy photon source is dynamic power supply,and the output is 2-Hz bias sine wave.Current-source rectifier(CSR)topology can achieve the 2-Hz current directly.Methods In order to get the output current and good power factor of the power grid,the algorithm of“indirect current control”is applied.This method needs to measure the voltage of three phases and calculates several certain parameters of the circuit.The control strategy based on the“indirect current control”of the CSR is built in the Simulink simulation environment.Parameters and algorithms are described in detail,and the control block diagram and simulation model are given.Results The control strategy can output the right current and make a good power factor in the side of grid.Conclusions The CSR topology,as a good choice of power supply of accelerator,has a well-researched prospect.

低压差线性稳压器的使用技巧

低压差线性稳压器(LDO)有许多使用技巧。详细介绍了提高LDO输入电压的方法,多片LDO的并联使用方法;并深入阐述能从(?)V起调的LDO以及用LDO构成恒流源的电路设计。