Overview of DFIG-Based Wind Power System Resonances Under Weak Networks

Song, Yipeng; Blaabjerg, Frede

doi:10.1109/tpel.2016.2601643

Cited by 128 publications

(71 citation statements)

References 62 publications

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“…The first one corresponds to the transitions among different operation modes which can be seen as a stability caused by changes in the power output from the MG to the grid. The second one is the interaction between the impedance of the weak grid and the output impedance of the MG which may also cause stability problems [26]. From Fig.11 (b), the math model of emulated weak grid shows as equation (17).…”

Section: Stability Analysismentioning

confidence: 99%

Coordinated Primary and Secondary Frequency Support Between Microgrid and Weak Grid

Xiao

Mingke

et al. 2019

IEEE Trans. Sustain. Energy

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Dispersed wind power connected to the weak grid may cause the frequency instability. In this paper, a hierarchical controller applied to a microgrid (MG), including wind turbines (WT) and battery units (BU), is proposed to provide in a coordinated frequency support to a weak grid by adjusting the tieline active power flow according to the frequency-grid requirements. The coordination between MG local and central controllers provides the following features. (i) In case of required grid-frequency, the MG tie-line power flow will be controlled to be constant in each dispatching time interval. (ii) In case of underfrequency, the coordination between WT virtual inertia and BU controllers will be used to participate in primary frequency regulation (PFR). Then, BU supplies power according to the secondary frequency regulation (SFR) commanded by the maingrid dispatch center. (iii) In case of over-frequency, BU absorbs power to reduce the tie-line active power for PFR purposes. After that, the SFR uses pitch control coordinated with the battery charge control. A stability analysis model is established to deal with several transitions among different operation modes and the interaction between the weak grid impedance and the MG output impedance. Simulation results are presented to validate the proposed approach. Index Terms-Wind/battery microgrids, primary frequency regulation (PFR), secondary frequency regulation (SFR), hierarchical control, central controller, local controller NOMENCLATURE Parameter DescriptionWW Generated wind energy [J] T Scheduling period [min] PWf Forecast output power of WT [W] PT Average wind power [W] B * Reference power of the BU inverter [W] PWT Actual WT output power [W] PWT * WT expected output power [W] Pinertia WT virtual power inertia [W] f Difference between the grid frequency and the rated one [Hz] k PFR factor [-] kd Differential coefficient of the frequency deviation [-] PAGC_MG AGC power scheduling of MG [W] PAGC_g AGC power scheduling of grid[W] CMG Frequency-regulation capacity of the MG [W] are with Tianjin Key Laboratory of Advanced Electrical Engineering and Energy Technology, Tianjin Cg Frequency-regulation capacity of the grid [W] fmin Minimum value of the normal frequency [Hz] fmax Maximum value of the normal frequency[Hz]  WT rotor angle speed [rad/s] rated WT rotor rated angle speed [rad/s]  PMSG rotor position angle[] p Pole pairs number of PMSG[-] Psloss PMSG stator losses[W] isabc PMSG stator current[A] Udc Back-to-back converter dc bus voltage[V] Air density [kg/m 3 ] WT radius[m] Wind energy utilization factor [W‧s 3 /kg‧m 2 ] β * Pitch angle reference of the WT [] β Pitch angle of the WT [] λ Tip speed ratio[-] maximum wind energy utilization factor [W‧s 3 /kg‧m 2 ] Popt WT maximum power [W] sd , sq d-q stator inductances [mH] s Stator resistance [Ω] sd , sq d-q stator voltages [V] Synchronous angular velocity[rad/s] φ Permanent magnet flux of the PMSG [Wb] Te Electromagnetic torque of the PMSG [N‧m] E Kinetic energy stored in the WT [J] J Inertia of the WT and i...

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Section: Stability Analysismentioning

confidence: 99%

Coordinated Primary and Secondary Frequency Support Between Microgrid and Weak Grid

Xiao

Mingke

et al. 2019

IEEE Trans. Sustain. Energy

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“…The DFIG impedance modeling is investigated as follows. There are mainly two types of filters used by DFIG grid side converter (GSC), which are the L filter and LCL filter, respectively [11]. The DFIG containing a commonly used L filter is applied in this paper.…”

Section: Equivalent Circuit Of the Systemmentioning

confidence: 99%

“…The GSC is modeled as a voltage source V GSC = i * L f G c G d connecting an impedance Z GSC = G c G d in series, where G c is the PI controller with proportional gain K pgsc and integral part K igsc /s. Gd is used to describe digital control delay [11]. Thus the equivalent impedance of the GSC and L filter can then be given as Z GL = Z Lf + Z GSC .…”

Section: Equivalent Circuit Of the Systemmentioning

confidence: 99%

“…The nth voltage harmonic can be derived through the inverse transformation of Equation (10), as given in Equation (11).…”

Section: Random Integer Harmonic Detectionmentioning

confidence: 99%

“…The compensation voltage in the time domain can be obtained by substituting µ * αn , µ * βn for µ n α , µ n β in Equation (11). Once the reference compensation harmonic voltage is obtained, it is input to a voltage controller to generate control signals.…”

Section: Random Integer Harmonic Detectionmentioning

confidence: 99%

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Harmonic Adaptability Remote Testing Method for Offshore Wind Turbines

Jiang

Liu

et al. 2017

Energies

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Harmonic adaptability (HA) capability is required for large-scale onshore and offshore wind turbines (WTs) connected to the grid. To ensure that the distortion of the harmonic voltage at the grid access point generated by grid simulator is in accordance with the required value, this paper proposes an on-site HA remote testing method for offshore WTs to eliminate submarine cable effects. The deviation compensation method detects the integer harmonic voltage distortion based on instantaneous reactive power theory, and the deviation from the required value is compensated by series active power filter. In order to further reduce the capacity of the designed device, integer harmonics close to the resonant frequency are suppressed by the selective harmonic damping (SHD) method initially. Owing to the attenuation of extreme amplification, the deviation determining the equipment capacity is decreased correspondingly. As a small synthesized impedance working for the selected frequency can suppress the amplification significantly, a low power ratings design for the SHD method can be achieved, and undesired resonance can be avoided. Simulation results indicate that the proposed method can make the harmonic distortion within the error tolerance.

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Active damping of resonances in DFIG system with cascade converter under weak grid

Din

Zhang

et al. 2019

Int Trans Electr Energ Syst

Self Cite

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Summary The interaction of impedance between the doubly fed induction generator (DFIG) system and series‐compensated weak grid gives rise to an issue of subsynchronous resonance (SSR). Likewise, the high‐frequency resonance (HFR) occurs when a DFIG system is connected to parallel‐compensated weak grid. This paper proposes an improved method to mitigate the caused resonance. The improved method, based on impedance modeling, utilizes an additional cascaded converter (CC) at Y‐point of DFIG stator winding with virtual impedance implemented at the CC control unit, which reshapes the DFIG impedance for effective mitigation of both SSR and HFR. The virtual impedance is disabled when DFIG operated in series‐compensated weak grid, while enabled when working in parallel‐compensated weak grid, which effectively damps the HFR. A detailed theoretical explanation and impedance modeling of the CC has been given. The effectiveness of the proposed method has been validated through MATLAB simulations based on a 2‐MW DFIG system.

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Overview of DFIG-Based Wind Power System Resonances Under Weak Networks

Cited by 128 publications

References 62 publications

Coordinated Primary and Secondary Frequency Support Between Microgrid and Weak Grid

Coordinated Primary and Secondary Frequency Support Between Microgrid and Weak Grid

Harmonic Adaptability Remote Testing Method for Offshore Wind Turbines

Active damping of resonances in DFIG system with cascade converter under weak grid

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