Research on Control Strategy of Grid-connected Brushless Doubly-fed Wind Power System Based on Virtual Synchronous Generator Control

The brushless doubly-fed wind power system based on conventional power control strategies lacks ‘inertia’ and the ability to support grid,which leads to the decline of grid stability.Therefore,a control strategy of brushless doubly-fed reluctance generator(BDFRG) based on virtual synchronous generator(VSG) control is proposed to solve the problem in this paper.The output characteristics of BDFRG based on VSG are similar to a synchronous generator(SG),which can support the grid frequency and increase the system ‘inertia’.According to the mathematical model of BDFRG,the inner loop voltage source control of BDFRG is derived.In addition,the specific structure and parameter selection principle of outer loop VSG control are expounded.The voltage source control inner loop of BDFRG is combined with the VSG control outer loop to establish the overall architecture of BDFRG-VSG control strategy.Finally,the effectiveness and feasibility of the proposed strategy are verified in the simulation.

Robust Position Observer for Sensorless Direct Voltage Control of Stand-Alone Ship Shaft Brushless Doubly-Fed Induction Generators

The aim of this paper is to investigate an adaptive sensorless direct voltage control(DVC)strategy for the stand-alone ship shaft brushless doubly-fed induction generators(BDFIGs).The proposed new rotor position observer using the space vector flux relations of BDFIG may achieve the desired voltage control of the power winding(PW)in terms of magnitude and frequency,without any speed/position sensors.The proposed algorithm does not require any additional observers for obtaining the generator speed.The proposed technique can directly achieve the desired DVC based on the estimated rotor position,which may reduce the overall system cost.The stability analysis of the proposed observer is investigated and confirmed with the concept of quadratic Lyapunov function and using the multi-model representation.In addition,the sensitivity analysis of the presented method is confirmed under different issues of parameter uncertainties.Comprehensive results from both simulation and experiments are realized with a prototype wound-rotor BDFIG,which demonstrate the capability and efficacy of the proposed sensorless DVC strategy with good transient behavior under different operating conditions.Furthermore,the analysis confirms the robustness of the proposed observer via the machine parameter changes.

Brushless Doubly-Fed Machines:Opportunities and Challenges

The brushless doubly-fed machine(BDFM)is a family of multiport electric machines with two ac electrical ports and a common mechanical port.Different from the conventional singly-fed machines whose synchronous speed is solely determined by a single supply frequency and the actual pole pair number,the BDFM has two supply frequencies and two different pole pair numbers to control the rotor speed.By the two accessible electrical ports,all BDFMs are endowed with more degrees of freedom for speed and power control,inherent fault-tolerant capability and high reliability.The BDFM in its broad sense has been extensively investigated as a promising alternative to the conventional slip-ring doubly-fed induction machine(DFIM)during the past decades,for both limited and wide speed range applications.This paper presents a new theoretical framework of the BDFM within which all topological variants can be closely linked by the similarities in working principle.The individualities of each machine topology are presented first,followed by the commonalities such as the modeling techniques,modes of operation,design considerations and control strategies.The challenges are identified and highlighted based on recent developments and possible opportunities are predicted considering the unique nature of this special AC machine type.

Design and analysis of a dual-stator brushless doubly-fed induction machine with a staggered dual-cage rotor

In this paper,a new dual-stator brushless doubly-fed induction machine with a staggered dual cage rotor is proposed,with emphasis on the general interconnection rule of the conductor bars for the staggered dual cage rotor.Since the squirrel cage rotor offers the merits of robustness,reliable structure,high slot filling factor,and low rotor resistance comparing to the wound rotor,it is introduced to the dual-stator brushless doubly-fed induction machine to solve the problems of high copper loss and unreliable rotor structure for the dual-stator brushless doubly-fed induction machine with a wound rotor.The originality of this article is to investigate the interconnection rule of conductor bars between the inner and outer cages.The constraint condition that is supposed to be satisfied is deduced by using the rotating magneto-motive force theory,based on which diverse slot/pole combinations are investigated.The performance comparison between the existing and proposed machines is conducted.Finally,a prototype is designed and fabricated.The experimental results verify the effectiveness of the proposed topology.

Overview of Research and Development Status of Brushless Doubly-Fed Machine System

The brushless doubly-fed machine(BDFM)has been widely used due to its advantages of robustness,reliable operation,ease of maintenance,adjustable power factor,small converter capacity and low cost.BDFM is attractive for use in many applications such as variable frequency speed regulation systems and variable speed constant frequency generation systems.Hence,there is a rapidly growing interest in design and control of BDFM.In this paper,the origin and development of BDFM are reviewed,the structural characteristics of BDFM are discussed at length,the principles of operation and design are analyzed,and the different control methods used for BDFM are overviewed and compared in detail.Finally,challenges and opportunities of BDFM are concluded.

抑制无刷直流电机转矩脉动的滑模观测器控制

无刷直流电机的转矩脉动影响电机整个系统的性能,制约其在高精度、高稳定性场合的应用。为了抑制无刷直流电机的换相转矩脉动,并且提高其控制的鲁棒性,在H_PWM-L_PWM调制基础上,将换相引起的转矩脉动作为系统干扰,设计了滑模观测控制器。利用滑模观测器的响应快速性,对参数变化和扰动不灵敏性,在系统扰动完全不可测的情况下,来抑制换相转矩波动的影响。仿真结果验证,提出的滑模观测器控制策略鲁棒性好,并且能有效减小换相转矩波动,是一种有效的抑制无刷直流电机换相转矩脉动的方法。

无刷双馈电动机的控制方法研究

相比于传统有刷双馈电机,无刷双馈电机去除了电刷和滑环,从而增强了运行可靠性。本文以无刷双馈电动机的数学模型为基础,通过对其定子功率绕组和控制绕组电流矢量的分析以及转矩表达式的推导,提出了一种新型的控制策略,在保证转速动、静态稳定性的同时,实现了功率因数可调的目的。同时通过仿真和实验验证了该控制策略的有效性。

Fault-tolerant control of an open-winding brushless doublyfed wind power generator system with dual three-level converter

To improve the fault redundancy capability for the high reliability requirement of a brushless doubly-fed generation system applied to large offshore wind farms,the control winding of a brushless doubly-fed reluctance generator is designed as an open-winding structure.Consequently,the two ends of the control winding are connected via dual three-phase converters for the emerging open-winding structure.Therefore,a novel fault-tolerant control strategy based on the direct power control scheme is brought to focus in this paper.Based on the direct power control(DPC)strategy,the post-fault voltage vector selection method is explained in detail according to the fault types of the dual converters.The fault-tolerant control strategy proposed enables the open-winding brushless doubly-fed reluctance generator(BDFRG)system to operate normally in one,two,or three switches fault of the converter,simultaneously achieving power tracking control.The presented results verify the feasibility and validity of the scheme proposed.