An Improved Feedforward Control Method Considering PLL Dynamics to Improve Weak Grid Stability of Grid-Connected Inverters

Zhang, Xueguang; Xia, Danni; Fu, Zhichao; Wang, Gaolin; Xu, Dianguo

doi:10.1109/tia.2018.2811718

Cited by 195 publications

(104 citation statements)

References 24 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

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

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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“…As grandezas de regime permanente de (8), (9) e (10) podem ser obtidas solucionando (1)- 7, considerando que as derivadas são nulas. Assim, para linearizar a mudança entre os domínios em torno do ponto de equilíbrio encontrado pode-se substituir (8) nas transformações, ou seja:…”

Section: B Linearizaçãounclassified

“…Utilizou-se o método baseado na impedância para estimar a estabilidade do sistema, e melhorar a robustez do controlador feed-forward. Uma análise semelhante é realizada para um sistema trifásico em [10], [11].…”

Section: Introductionunclassified

Influência do Método de Sincronismo na Estabilidade de Conversores Trifásicos Conectados à Rede

Nicolini¹,

Carnielutti²,

Massing³

et al. 2019

Eletrônica de Potência

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Este artigo realiza a análise da influência do sistema de sincronismo sobre a estabilidade de conversores trifásicos conectados à rede elétrica combinando equações de espaço de estado e funções de transferência matriciais. Fundamentado no método das impedâncias, divide-se o sistema de geração em dois elementos representados por funções de transferência matriciais em eixos síncronos dq. O primeiro representa a admitância equivalente do conversor, que é obtido ao considerá-lo conectado à uma rede ideal. Neste caso, são considerados as dinâmicas do phase-looked loop (PLL) e do controlador de corrente. O segundo representa a impedância equivalente da rede. O modelo não-linear obtido foi, então, linearizado por perturbações de pequenos sinais. A interconexão entre os dois elementos é realizada em matrizes função de transferência e representada na forma de digrama de blocos. A análise da estabilidade do sistema se dá pela utilização do critério generalizado de nyquist (GNC). Além disso, o método dos autovalores é utilizado no sistema completo em espaço de estados para elucidar a escolha dos ganhos do PLL. A fim de verificar a análise teórica, resultados de simulação são apresentados, mostrando uma boa correção com a análise matemática no domínio da frequência.

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“…Reference [17] concluded that the stability of a grid-tied inverter remains unchanged with increasing PLL bandwidth. Finally, in [18][19][20][21] feedforward control methods were proposed to reduce the impact of the PLL bandwidth on the stability of the system. These methods all model the output impedance of the converter in the Laplace domain and analyse its dependence on the PLL parameters.…”

Section: Introductionmentioning

confidence: 99%

Small-Signal Modelling and Stability Assessment of Phase-Locked Loops in Weak Grids

et al. 2019

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This paper proposes a low-complexity small signal model for a 3-leg converter connected to a balanced three-phase, three-wire weak grid and synchronised to this grid using a PLL implemented in a synchronous rotating d-q axis. A thorough analysis of the system stability as a function of the PLL bandwidth and the short circuit ratio (SCR) of the grid is performed based on a linearised model. By using the proposed model, an improved design process is proposed for the commonly used dq-PLL that accounts for the potential stability issues which may occur in weak grids. Using the proposed approach, it is possible to optimise the PLL design to find the fastest PLL that can operate stably considering the SCR of the grid. In addition, the proposed model is very simple, resulting in a straightforward design tool that could also be used for online stability monitoring. The method is validated through simulations and experimental results from a 5kW laboratory system.

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An Improved Feedforward Control Method Considering PLL Dynamics to Improve Weak Grid Stability of Grid-Connected Inverters

Cited by 195 publications

References 24 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

Influência do Método de Sincronismo na Estabilidade de Conversores Trifásicos Conectados à Rede

Small-Signal Modelling and Stability Assessment of Phase-Locked Loops in Weak Grids

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