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Practical subsynchronous instability events have been observed in doubly fed induction generator-based wind farms, which are radially connected to fixed series compensated transmission lines. As a special type of subsynchronous resonance, this phenomenon is described here as subsynchronous control interaction (SSCI). This study proposes a centralis...
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Citations
... However, the cost of FACTS devices could be reduced by designing a special-purpose shunt-VSC to generate a compensated signal at the extracted sub-synchronous frequency instead of the fundamental frequency. The sub-synchronous component is extracted by a notch filter and a bandpass filter [128,129]. The challenge in this technique is the accurate extraction of the sub-synchronous frequency because of varying sub-synchronous and fundamental frequencies with time during SSI events. ...
Emerging sub-synchronous interactions (SSI) in wind-integrated power systems have added intense attention after numerous incidents in the US and China due to the involvement of series compensated transmission lines and power electronics devices. SSI phenomenon occurs when two power system elements exchange energy below the synchronous frequency. SSI phenomenon related to wind power plants is one of the most significant challenges to maintaining stability, while SSI phenomenon in practical wind farms, which has been observed recently, has not yet been described on the source of conventional SSI literature. This paper first explains the traditional development of SSI and its classification as given by the IEEE, and then it proposes a classification of SSI according to the current research status, reviews several mitigation techniques and challenges, and discusses analysis techniques for SSI. The paper also describes the effect of the active damping controllers, control scheme parameters, degree of series compensation, and various techniques used in wind power plants (WPPs). In particular, a supplementary damping controller with converter controllers in Doubly Fed Induction Generator based WPPs is briefly pronounced. This paper provides a realistic viewpoint and a potential outlook for the readers to properly deal with SSI and its mitigation techniques, which can help power engineers for the planning, economical operation, and future expansion of sustainable development.
... Year Type of Generator Method Yunjie Gu et al. [38] 2019 Doubly Fed Induction Generators (DFIG) Motion-induction compensation Chao Gao et al. [39] 2017 DFIG Time-domain analysis Liang Yuan et al. [40] 2020 DFIG Small-signal analysis Fan Yang et al. [41] 2017 DFIG System state matrix and eigenvalue analysis Yanhui Xu et al. [42] 2019 DFIG Active disturbance rejection control Andres E. Leon [50] 2017 DFIG Linear-quadratic regulator Junjie Ma et al. [51] 2019 DFIG Impedance model Wenjuan Du et al. [52] 2017 DFIG -F. Bizzarri et al. [53] 2018 Induction machines Stability analysis Liang Wang et al. [54] 2015 Induction generator Sub-synchronous damper Penghan Li et al. [55] 2021 DFIG Fractional order sliding mode controller Xi Wu et al. [56] 2018 DFIG Sub-synchronous damping controller Liang Wang et al. [57] 2017 DFIG Direct stator-power controller Wenjuan Du et al. [58] 2017 Variable-speed wind generators (VSWGs) Open-loop modal analysis Yanhui Xu et al. [59] 2019 DFIG STATCOM ...
Series compensation is a cost-efficient way to enhance the system reliability and the power transfer capabilities of long transmission lines. As a result of series compensation, the sub-synchronous oscillation (SSO) causes a severe risk of torsional interactions (TI). Therefore, SSO becomes a serious risk factor in grid-integrated renewable energy systems. Numerous researchers have evaluated SSO instances in several types of asynchronous generators in power systems. In this paper, the categorization and the overview of the SSO phenomena have been vital for the different mechanisms, sophisticated systems, analytical techniques, and multiple reviews that have been propagated. This study provides SSO analysis for various types of renewable energy power plants. Finally, while dealing with conventional and new power systems, this study summarizes recent SSO-damping and alleviation techniques for practical perception and future perspectives.
... Using shunt-VSC with well-tuned filters that could extract sub synchronous frequencies has been proposed as an economically feasible alternative [89]. A shunt VSC along with a properly designed controller could dissipate the resonance power resulting from SSCI by absorbing the sub synchronous currents, thus damping out the SSCI [106]. A robust SSR damping control strategy is proposed in [107] where the sub harmonic voltage source converter (SVSC) injects sub synchronous currents to stabilize SSR. ...
With the recent developments in renewable energy generation and addition of power electronic devices, power system dynamics have become extremely complex. One of the challenges faced due to this transition is the sub synchronous oscillations caused by the interaction of renewable energy sources and various components of the power grid. Recently reported incidents due to sub synchronous oscillations highlight the need of monitoring and suppression of these harmful oscillations in real time. This paper gives an overview of the phenomena of sub synchronous oscillations and discusses the existing monitoring and damping techniques along with their limitations. Further, it highlights the research trends along this path.
... The hybrid compensation, such as the combination of series and shunt voltage compensation, is named UPFC, as illustrated in Figure 12. The shunt and the series branch in the UPFC have different functionality of retaining the terminal FIGURE 13 Special SVC for DFIG system to damp SSR [182] voltage and controlling the power flow, respectively. The underlying objective of the UPFC installed at PCC is to keep the system stable. ...
... To subsynchronous frequency might be extracted using the well-tuned filter. [182] proposed a shunt-SVC, which injects the controllable reactive current at the subsynchronous frequency, depicted in Figure 13. [183] combined band-pass filter and notch filter to extract the subsynchronous signal using line voltage as a feedback signal. ...
In recent years, the wind energy conversion system faces significant challenges for stable and secure operations, especially in the weak grid due to high penetration of wind energy into the grid. Doubly fed induction generator (DFIG) is one of the most popular wind turbine generators due to its cost‐effective variable speed and low‐cost partial size power converter. Impedance interaction between series or parallel compensated weak grid and the DFIG system causes sub‐synchronous resonance (SSR) and high‐frequency resonance (HFR). A comprehensive review of the state‐of‐the‐art SSR and HFR in the DFIG system under a weak grid is presented. First, based on features, such as supplementary hardware, linear and non‐linear control strategies, the resonance damping techniques are classified into different types. Then, the advantages and disadvantages of SSR analysis and damping techniques techniques are put forward. Moreover, the latest development of state‐of‐the‐art SSR and HFR analysis and damping techniques are supplemented. Finally, the contemporary and future trends of the SSR and HFR techniques are discussed.
... The significant disadvantage of adding FACTS devices is the high equipment and maintenance cost. Another type is the configuration of supplementary damping controller (SDC) [5][6], or the optimization of control parameters to increase the system software damping. The SDC methods in the Grid Side Converter (GSC) control of the DFIG are studied [7][8] [9]. ...
... At the same time, it also lacked the stability analysis of system by using this non-linear control. LFO can also be suppressed by injecting the current with the same oscillation frequency and opposite phase into the system or compensating the oscillation reactive power through Active Power Filter (APF), Static Synchronous Compensator (STATCOM) or Static Var Generator (SVG) [25][26][27]. However, there is the need of the equipment installation at the network high-voltage side, which is expensive. ...
Low frequency oscillation (LFO) in the electric multiple units (EMUs)-traction network cascade system (ETNCS) can lead to traction blockade and abnormal operation. Using the Chinese CRH3 EMUs as an example, a new LFO suppressing method by applying the energy storage (ES) device on EMUs is proposed in this paper and the ES is connected to the DC-link on board. The equivalent model of the ETNCS is established at first. The critical condition of LFO in the ETNCS is analyzed via impedance ratio criterion and Bode diagram. Then, the proposed on-board bidirectional DC-DC converter integrated with the ES system is controlled via a virtual DC machine (VDCM) strategy, and the VDCM small signal model derivation and the parameter design are carried out. Using the Bode diagram of the impedance ratio, the system stability with the ES device controlled by the proposed VDCM scheme is analyzed again; simulation results verify the effectiveness of the control algorithm to suppress the LFO adaptively. Compared with the traditional PI controller, the system steady-state and dynamic performance can be improved with the proposed method, including decreased overshoot, fluctuation, response time, and increased gain margin of the DC-link voltage.
... At the same time, the oscillation has no connection with the torsional oscillation of shafting. This kind of SSO phenomenon is called Sub-synchronous Control Interaction (SSCI) [3][4][5]. ...
Since the development of renewable power generation, Sub/Super-Synchronous Control Interaction (SSCI), has attracted wide attention. Sub/super-synchronous oscillation (SSO) belongs to the category of small signal stability, and its characteristics are closely related to the operation mode and controller parameters in power grid. The operation mode of renewable power system changes frequently, a method to construct controller parameter stability region (PSR) is proposed for online assessment of the matching degree of controller parameters in power grid under current operation mode. Based on Gerschgorin disk theorem (GDT), eigenvalue distribution range of the system state matrix is estimated, thus the feasible value set of the controller parameter is deduced through small signal stability criterion. The stability margin evaluation index is proposed for guiding the prevention and control of SSO. Specifically, the preconditions of the application of the GDT on the PSR construction are discussed, and a construction method of transition matrix is proposed for the PSR construction. Furthermore, to reduce the conservativeness of PSR, an extension method for PSR is given. Finally, the validity of the proposed method is verified by a realistic benchmark. The efficiency of the proposed method is highlighted by comparing with the point-wise eigenvalue calculation of the state matrix.
... Decrease results in more stability [40] As the DC bus decouples the MSC and the GSC, the MSC has very low participation in the adverse interactions with the grid [7,24] Kp,Q In weak grid conditions, a decrease in gain results in more stability [24] Ki,Q In weak grid conditions, increase in gain (i.e., making the AC voltage control slower) results in more stability [24] In general, the controller tuning is the preferred solution to mitigate SSO, as it does not require using additional hardware devices or software update. Yet, this is not always practical. ...
The replacement of conventional generation by power electronics-based generation changes the dynamic characteristics of the power system. This results in, among other things, the increased susceptibility to subsynchronous oscillations (SSO). First, this paper discusses three recently emerging SSO phenomena, which arise due to the interactions between (1) a doubly-fed induction generator and a series compensated transmission system; (2) a voltage source converter (VSC) and a weak grid; and (3) nearby VSCs. A fundamental review of these phenomena resulted in the requirement for a reclassification of the existing SSO phenomena. This reclassification is proposed in this work and is based on interacting components identified using participation factor analysis for the distinct phenomena. Second, a critical review of the existing mitigation measures is performed for these phenomena, highlighting the advantages and disadvantages of the solutions. The influence of the wind speed, grid strength, number of wind turbines, and several converter controller parameters are also discussed. To assist equipment manufacturers, control design engineers, and system operators in selecting and designing effective mitigation measures, the existing solutions are categorized in control solutions, hardware solutions, and solutions based on system level coordination. Finally, perspectives on open issues conclude this paper.
... In fact, the electromagnetic oscillation is one of the typical problems in power electronized power systems [1,2]. In the point view of oscillation frequency, the oscillation phenomenon in CTAIP is similar to the oscillation caused by subsynchronous control interaction (SSCI) [3,4]. There has been a large number of studies focused on SSCI. ...
The central Tibet AC interconnection project (CTAIP), which connects the Tibet power grid and the Sichuan power grid through a long distance transmission line of more than 1400 km, has a significant problem of voltage regulation. In order to improve the voltage regulation performance, six sets of ±60 Mvar static VAR compensators (SVC) were installed in the CTAIP. However, the SVCs may lead to electromagnetic oscillation below 50 Hz while improving voltage regulation capability. In this paper, the electromagnetic oscillation modes and the sensitivity of control parameters of SVC are analyzed. Then, the characteristics and influencing factors of the oscillation are discussed. It was found that there is an inherent electromagnetic oscillation mode below 50 Hz in the ultra-long distance transmission system. The employ of SVCs weaken the damping of this mode. Large proportional gain and integral gain (PI) parameters of SVCs can improve the voltage regulation performance, but weaken the electromagnetic oscillation mode damping. Therefore, a suppression method based on SVC PI parameters optimization is proposed to damp the oscillation. The essential of this method is to use the rising time of voltage response and setting time of SVCs as performance indicators of voltage regulation, and take the damping level of the electromagnetic oscillation mode as the performance index of SVC electromagnetic oscillation suppression ability. Combining the two indicators to form a comprehensive optimization index function, an intelligent optimization algorithm is applied. The process of SVC parameter optimization and the steps of multi-SVC parameter optimization in large power grids is proposed. Finally, PSCAD and real-time digital simulation (RTDS) simulation results verified the correctness of the proposed method. The optimization strategy was applied to CTAIP. The artificial grounding short circuit experimental results proved the effectiveness of the proposed strategy.
... The total number of WTGs in a WF are mentioned in brackets, as shown in Fig. 5. The parameters of these WTGs can be found in [30] and are not repeated here. The total number of nodes of the simulation model are 24, considering all WTGs of a wind farm are connected to one common node on the high-voltage side. ...
It has become a great challenge to mitigate the unstable subsynchronous control interaction (SSCI) in practical series compensated wind power systems, mainly because of the system-wide influential factors, such as the constantly changing wind speed, number of in-service wind turbines, and operating conditions. In an effort to address the challenge, this work proposes a simple yet practical grid-side subsynchronous damping controller (GSDC), which consists of a subsynchronous damping controller (SDC) supplemented to a subsynchronous current generator (SCG). The GSDC utilizes bus voltages and line currents as feedback signals and injects currents at the subsynchronous frequency into the system to provide active damping. The parameters of the SDC and SCG can be optimized for any system facing SSCI issues. In this study, a GSDC is developed and optimized over an EMT model of a realistic system. The proposed scheme has demonstrated its effectiveness and robustness through controller-hardware-in-the-loop (CHIL) tests for mitigating SSCI over a wide range of operating conditions. This work has paved the way for the commissioning of a practical GSDC in a real-world system that has experienced unstable SSCI incidents.
