This paper presents a new direct active and reactive power control (DPC) of grid-connected doubly fed induction generator (DFIG)-based wind turbine systems. The proposed DPC strategy employs nonlinear sliding-mode scheme to directly calculate the required rotor voltage so as eliminate instantaneous errors powers without involving any synchronous coordinate transformations. Thus, no extra current loops are required, thereby simplifying system design enhancing transient performance. Constant...

This paper presents a mathematical model of doubly fed induction generator (DFIG) in the positive synchronous reference frame under distorted grid voltage conditions. The oscillations DFIG's electromagnetic torque and instantaneous stator active reactive powers are fully described when is harmonically distorted. Four alternative control targets proposed to improve system responses during harmonic distortions. A new rotor current scheme implemented developed. consists proportional-integral...

The open-winding configuration with a common dc bus provides zero-sequence current loop which allows the flowing. With application in permanent magnet synchronous generator (PMSG) systems, existing is inevitably caused by mode voltage generated pulsewidth modulation (PWM) techniques and third back EMF inherent flux harmonic component. mathematical modeling analysis, equivalent circuit based on PMSG system proposed. Meanwhile, suppression controller designed. In this paper, zero vector...

This paper presents a direct power control (DPC) strategy for doubly fed induction generator (DFIG)-based wind generation system under distorted grid voltage. By analyzing the six times frequency pulsation produced by fifth and seventh voltage harmonic components, novel DPC with vector proportional integrated (VPI) regulator has been proposed to implement smooth active reactive output of DFIG. The performance analysis strategy, including steady dynamic state performance, closed-loop...

Impedance-based method is an effective to analyze the system stability. Based on impedance stability theory, a doubly fed induction generator (DFIG) based wind power generation can be decoupled into positive- and negative-sequence subsystem. Then, under small-signal operation, each subsystem assumed have linear characteristic in frequency domain. Therefore, single-in-single-out criterion applied for of interconnected consisted DFIG grid. However, when there coupling system, this assumption...

This paper proposes an improved direct power control (DPC) strategy for a doubly fed induction generator (DFIG)-based wind generation system under unbalanced grid voltage dips. The fundamental and double frequency pulsations, which are produced by the transient faults, mathematically analyzed accurately regulated. Five selectable targets, with proper references given, designed different applications during network unbalance. In order to provide enhanced performance, two resonant controllers,...

This paper proposes a coordinated direct power control (DPC) scheme for the rotor-side converter (RSC) and grid-side (GSC) of doubly fed induction generator (DFIG) under unbalanced grid voltage conditions. In order to eliminate coupling interactions between phase-locked loop (PLL) local network, virtual phase angle is used replace actual one acquired by PLL. Thus, PLL removed out RSC GSC in proposed DPC scheme. During network unbalance, controlled reduce torque ripples, while three...

Fault detection and location method are two significant techniques to recognize clear the fault timely. This paper proposes a novel for mesh-type DC microgrid. The key of this is implement similarity analysis on sampled lines current reference by employing an improved Pearson correlation coefficient. Firstly, can be implemented comparing with steady-state in movable time window. And line type recognized based Secondly, obtained calculation results transient current, which corresponds...

The zero-sequence loop inherently exists in the structure of three-phase open-end winding permanent-magnet synchronous machine (OW-PMSM) system with common dc bus, which provides circulating path for current (ZSC) and consequently causes torque ripple extra loss. Besides, common-mode voltage (CMV), can cause many negative effects, such as bearing failure motor bearing, is another concern driving system. However, simultaneous suppression ZSC CMV control devices investigated mainly application...

The phase-locked loop (PLL) will have a negative impact on the stability of doubly fed induction generators (DFIG) system under inductive weak grid. Some PLL-less methods been presented to remove PLL such as switching synchronous reference frame virtual or <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">αβ</i> -frame. Based equivalent single-input single-output impedance model, it is found that DFIG systems implemented in -frame are more...

Torque ripple caused by zero-sequence current (ZSC) and relatively high switching frequency severely worsens the operating performance of an open-winding permanent-magnet synchronous machine (OW-PMSM) system with common dc bus. In this paper, a novel q-axis injection method based on angle-shift-based voltage distribution is proposed for OW-PMSM With method, torque ZSC can be counteracted component generated injected current. Meanwhile, corresponding modulation range analyzed to investigate...

Zero-sequence current (ZSC) is inevitable in the structure of an open-end winding permanent-magnet synchronous machine (OW-PMSM) system with a common dc bus due to simultaneous existence ZSC loop and zero-sequence voltage (ZSV) caused by inverters third electromotive force. To suppress ZSC, novel strategy reduced switching frequency proposed this paper. The main contribution method that suppressed totally frequency. duration time active vectors redistributed generate reference loop, which...

This paper proposes a flexible grid connection technique of voltage-source inverter (VSI) based on direct power control strategy under unbalanced conditions. Based the mathematical model in αβ stationary reference frame VSI, generalized compensation expressions for adjustable current unbalance and fluctuations are deduced. By analyzing active reactive expressions, three different algorithms parameters designed to make compromise among negative sequence, ripples, ripples. To satisfy code,...

This paper proposes an improved direct power control (DPC) strategy for the rotor-side converter (RSC) and grid-side (GSC) of doubly fed induction generator under unbalanced distorted voltage conditions. The proposed scheme is implemented in a synchronous reference frame with fixed angular speed, so that phase-locked loop can be removed relevant potential instability issues avoided. Besides, sequential separations complex calculations compensating items eliminated direct-resonant method...

This article presents an improved virtual synchronous generator (VSG) control strategy of doubly-fed induction (DFIG) during symmetrical voltage fault. Based on VSG control, DFIG can behave like a conventional (SG), which support frequency and in grid-connected mode. Moreover, when microgrid disconnects from grid, provide power for local loads. However, fault, the transient components cannot be controlled properly by VSG. To solve this problem, air-gap flux feedback is designed to accelerate...

This letter proposes a simplified modulation strategy for the open-end winding permanent-magnet synchronous motor (OW-PMSM) system with common dc bus under open-phase fault condition, suppression of circulating current. Based on analysis voltage distribution OW-PMSM fault, phase-shifted stationary coordinate is proposed and applied to synthesize reference voltage. In process, duration time two selected orthogonal vectors directly obtained both sector identification calculation trigonometric...

The sequence-domain impedance using harmonic linearization technique can well describe the behavior of interconnected system consisting grid and converter. However, fast phase-locked loop (PLL) design, unbalanced current controller structure will cause unneglectable off-diagonal components in matrix Due to frequency coupling sequence effect domain, traditional single input output transfer function lacks capability accurately express this shift relationship. Therefore, paper, (HTM) is used...

A simplified model predictive control (S-MPC) for open-winding permanent magnet synchronous motor system fed by two isolated power sources is proposed in order to remove the complex tuning work of weighting factors and reduce calculation burden conventional MPC. Control constraints torque flux MPC are converted into an equivalent vector purpose eliminating factor cost function. Moreover, a novel prediction strategy fast voltage selection scheme presented burden. As result, optimal selected...

With the increasing penetration of renewable energy, wind turbines based on doubly fed induction generators (DFIG) are becoming more and important in power system. The impedance reshaping control strategy virtual method can be utilized to solve stability problem DFIG-grid interconnected system under weak grid. However, issues caused by phase-locked loop (PLL) is complicated due frequency coupling characteristic. This article presents an improved DFIG a symmetrical PLL, which characteristic...

In order to realize the grid-friendly wind turbine system (WTS), applying of virtual synchronous generator (VSG) control strategy WTS has become a trend research, and it is also required analyze grid-connected operation characteristics VSG controlled WTS. this paper, impedance modeling impedance-based stability analysis type-IV are carried out. Different from existing method that modeled by high dimensional model with complex expressions, describe shaping effects dc-link dynamics proposed,...

In this article, we analyze the negative impact of phase-locked loop (PLL) on stability doubly fed induction generators system. The small-signal disturbance PLL mainly affects coordinate transformation rotor current and introduces a resistance within bandwidth. Two impedance reshaping methods are carried out to weaken resistance. A virtual in conventional control is added first method. second method completely removes by switching target from power. difference between these two analyzed...

With the increase of wind power installation capacity, line commutated converter (LCC)-based high-voltage direct current (HVdc) transmission system is an effective scheme for long distance power. Commutation failure a common fault LCC-HVdc system. During commutation failure, voltage sending ac grid presents "first decreased then increased" characteristic. In order to avoid overvoltage under causing generation (WPGS) separate from grid, it necessary suppress failure. This article...

The paper presents a modularized control strategy of doubly fed induction generator (DFIG) system, including the grid-side converter (GSC) and rotor-side (RSC), under unbalanced harmonic grid voltage. sequence decomposition process complicated reference calculation can be avoided in proposed strategy. From perspective power friendly operation, targets DFIG system this are chosen as: 1) smooth active reactive injected into grid; 2) balanced sinusoidal current grid. RSC GSC work as two...

The paper presents a collaborate control for the rotor-side converter (RSC) and grid-side (GSC) of doubly fed induction generator (DFIG) generation system during network unbalance. In this study, RSC is controlled to reduce torque ripples, three selectable targets GSC, i.e., balanced total currents, constant active or reactive power into grid from overall are identified impacts negative-sequence voltage on DFIG performance. A reduced-order generalized integrator employed, which implemented...

This paper presents a flexible compensation strategy for voltage source converter (VSC) connected to an unbalanced and harmonic distorted grid, which can achieve tradeoff between the two common control targets, i.e., compensating at point of coupling (PCC), output current VSC. To target, hybrid virtual impedance method is proposed, uses both feedforward PCC feedback develop (including negative sequence) references. Compared with conventional methods using only or feedback, proposed VSC in...