Symmetrical PLL for SISO Impedance Modeling and Enhanced Stability in Weak Grids

Yang, Dongsheng; Wang, Xiongfei; Liu, Fangcheng; Xin, Kai; Liu, Yunfeng; Blaabjerg, Frede

doi:10.1109/tpel.2019.2917945

Cited by 117 publications

(79 citation statements)

References 28 publications

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“…y m dq = y dd y dq y qd y qq ↔ y +,dq = y dd + y qq 2 + j y qd − y dq 2 (29) y −,dq = y dd − y qq 2 + j y qd + y dq 2 where the superscript m indicates that the parameter is a matrix. Based on (28) and (29), the equation using real space vectors and transfer matrices can be reformulated using complex space vectors and complex transfer functions, shown as follows. (30) where z dq = [z d , z q ] T and z dq = z d + jz q .…”

Section: Appendix a Complex Transfer Functions Representations Of Traunclassified

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Effect of Reactive Power Characteristic of Offshore Wind Power Plant on Low-Frequency Stability

Zhou

Torres-Olguin

et al. 2020

IEEE Trans. Energy Convers.

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Oscillation phenomena of offshore wind power plant (OWPP) in a wide frequency range can be caused due to impedance interactions between grid-connected inverters (GCIs) and transmission cables. In this paper, impedance model of GCI with outer power control loop, inner current control loop and phase-locked loop is first established in dq reference frame. The correctness is validated by frequency scanning method. Then, the effects of active and reactive power/current references on dq impedance characteristics of GCI with/without consideration of power control loop are investigated using complex space vectors and complex transfer functions. Furthermore, RLC circuit model of transmission cable considering frequency-dependent characteristics is also established for dq-domain IBSC. On the basis of them, it's found that low-frequency oscillation phenomena of OWPP under power control mode may occur if active power reference exceeds a certain threshold value, which can be mitigated by injecting a certain amount of negative reactive power. Impacts of PLL parameters, length of transmission cable and number of paralleled GCIs on required negative reactive power for low-frequency stabilization are further investigated. Both Matlab/Simulink-based simulation and OPAL-RT-based real-time verification are implemented in an OWPP with four permanent magnet synchronous generators to validate the correctness of the reactive power characteristic analysis results and the feasibility of mitigating low-frequency oscillation phenomena by negative reactive power injection. Index Terms-Frequency scanning, grid-connected inverter, low-frequency stability, offshore wind power plant, reactive power, transmission cable.

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Section: Appendix a Complex Transfer Functions Representations Of Traunclassified

“…According to (29), the transfer matrices in (2) and (3) can be represented as complex transfer functions, shown as follows.…”

Section: Appendix a Complex Transfer Functions Representations Of Tramentioning

confidence: 99%

Effect of Reactive Power Characteristic of Offshore Wind Power Plant on Low-Frequency Stability

Zhou

Torres-Olguin

et al. 2020

IEEE Trans. Energy Convers.

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“…4, sequence-couplings of the IP-CCI cannot be neglected within 1500Hz, and that of the PLL-CCI cannot be neglected near 50Hz. Take the sequencecouplings into consideration, the SISO stability analysis models are modified by the MIMO admittance-matrix-based analysis model LPN(s) as shown in (25) [16], where Jp(s) and Jn(s) are included, Zgp(s) and Zgn(s) are the positive-and negative-sequence impedances of the grid. By means of the MIMO model, accurate stability judgements can be derived according to the generalized Nyquist criterion, but it fails in getting clear insight of the instability mechanism from LPN(s).…”

Section: A Derivation and Analysis Of Equivalent Sequence-admittancementioning

confidence: 99%

Coupling-Related Instability Mechanism and Mitigation Analysis of the Instantaneous Power Based Current Controlled Inverter

Zheng

et al. 2020

IEEE Access

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Instabilities related to sequence-couplings of current controlled inverters (CCIs) have been recognized recently, but limited to accurate stability analysis of CCIs synchronized to the grid by the phaselocked loop (PLL). As for CCIs, another feasible grid-synchronization method is based on the instantaneous power (IP) theory, while instability recognitions of the IP-based CCI (IP-CCI) are lacking. Therefore, this paper reveals the instability mechanism and mitigation of the IP-CCI by comparison with the PLL-based CCI (PLL-CCI). Specifically, sequence-admittances of the IP-CCI are modeled, and interactions between sequence-couplings and circuit-coupling of the CCI-grid system are analyzed further. Simultaneously, influences of different system parameters on instabilities of the IP-CCI are thoroughly studied. Studies indicate that sequence-admittances of the IP-CCI exhibit closer sequence-couplings in comparison to that of the PLL-CCI, and negative damping of the IP-CCI is resulted from sequence-couplings, which clarifies interactive instabilities of the grid-connected IP-CCI are coupling-related. Therefore, corresponding instability mitigation can be achieved via sequence-decoupling methods, like the studied controller parameters regulation methods and the filter-based methods. Whereas, the stability deterioration level of sequence-couplings is grid-impedance-dependent, which means the weak grid would limit the decoupling performance. Nyquist plots, simulations and experiments are carried out to verify the studied couplingrelated instability of the IP-CCI. INDEX TERMS Current controlled inverter, instantaneous power, sequence-admittance, coupling-related instability.

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“…Recently, [24] conducted a detailed study on the stability of grid connected converter with PLL inclusions. The authors in [25] have proposed the symmetrical PLL for single input single output (SISO) impedance modeling to improve the stability of the grid-connected converter under a weak grid. Reference [26] put forward the two-port network based impedance modeling and stability analysis method for a grid-connected converter.…”

Section: Introductionmentioning

confidence: 99%

“…Reference [26] put forward the two-port network based impedance modeling and stability analysis method for a grid-connected converter. However, the literature [24][25][26] only relies on the grid-connected converter.…”

Section: Introductionmentioning

confidence: 99%

Impact of Phase Locked Loop with Different Types and Control Dynamics on Resonance of DFIG System

et al. 2020

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In recent years, the doubly fed induction generator (DFIG) operates in a weak grid, rather than a strong grid due to the high proportion of wind energy into the power grid. The impedance interaction between the DFIG system and series and parallel compensated weak grid might cause the subsynchronous resonance (SSR) and high frequency resonance (HFR) in the DFIG system, respectively. Phase locked loop (PLL) is a popular grid synchronization technique, and the high bandwidth PLL can cause resonance at middle frequencies in the DFIG system. However, the impact of PLL types and their controller dynamics on the resonance in the DFIG system are not adequately researched. The impact of the PLL controller with different types, such as synchronous reference frame (SRF) and Lead/Lag PLL, is studied in this paper to fill this gap. Additionally, an improved PLL is proposed, which can guarantee the high phase margin and decrease the likelihood of the resonance at middle frequencies in the DFIG system under a weak grid. Moreover, the phase margin of the DFIG system impedance with an improved PLL is less sensitive to its controller parameters. Simulation and experimental results verify the effectiveness of the proposed method.

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Symmetrical PLL for SISO Impedance Modeling and Enhanced Stability in Weak Grids

Cited by 117 publications

References 28 publications

Effect of Reactive Power Characteristic of Offshore Wind Power Plant on Low-Frequency Stability

Effect of Reactive Power Characteristic of Offshore Wind Power Plant on Low-Frequency Stability

Coupling-Related Instability Mechanism and Mitigation Analysis of the Instantaneous Power Based Current Controlled Inverter

Impact of Phase Locked Loop with Different Types and Control Dynamics on Resonance of DFIG System

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