Stability Analysis and Damping Enhancement Based on Frequency-Dependent Virtual Impedance for DC Microgrids

Guo, Li; Zhang, Shaohui; Li, Xialin; Li, Yunwei; Wang, Chengshan; Feng, Ying

doi:10.1109/jestpe.2016.2598821

Cited by 147 publications

(81 citation statements)

References 44 publications

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“…To evaluate the proposed EMS, constant power load (CPL) [50] models were selected due to their widely use in DC MGs analyses [51][52][53][54][55]. That representation has the main characteristic of changing both the load current and voltage to keep the load consumption constant; therefore, when the bus voltage exhibited perturbations, the load current changed accordingly.…”

Section: Devices and Control Strategiesmentioning

confidence: 99%

“…This is different from the constant impedance load (CIL) representation, in which perturbations in the bus voltage causes a different load power consumption. In practical applications of DC Microgrids CPL is an accurate representation of the loads due to the presence of DC/DC converters interfacing the loads with the DC bus: the load current changes according to the perturbations in the bus voltage (load voltage) to consume the power requested by the load [51][52][53]. Therefore, CIL is not an accurate representation of the loads in DC Microgrids with commercial loads.…”

Section: Devices and Control Strategiesmentioning

confidence: 99%

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Energy Management in PV Based Microgrids Designed for the Universidad Nacional de Colombia

et al. 2020

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Stand-alone Electrical microgrids (MGs) require power management strategies to extend the life-time of their devices and to guarantee the global power balance of non-critical loads such as lighting of small sections of an university campus or individual air conditioning systems. This paper proposes an energy management strategy (EMS) for an isolated DC microgrid formed by a photovoltaic system (PVS), an energy storage system (battery), and a noncritical load. This configuration enables the photovoltaic system to control the power generation and ensures that the storage element does not exceed the safe limits of the state of charge. To control the generation of the photovoltaic system, two operating modes based on the perturb and observe (P&O) algorithm are implemented. The first one performs a maximum power point tracking (MPPT) action, while the second one regulates the power generated by the PVS to match the load requirement (power demand tracking, PDT). The management strategy also considers different operating states for ensuring the battery safety: normal operation, overcharge (at the maximum state of charge), and bulk charge (at the minimum state of charge); in those states the disconnection/connection of both the battery and the load is also considered. The main contribution of this work is to design and test a control strategy for an EMS aimed at regulating a standalone microgrid based on a PV system and an energy storage device. This solution is validated using detailed MG circuital simulations, which includes the PV source model (single-diode model), lithium-ion battery model, constant power load model and the DC/DC converters equations; moreover, realistic power generation and demand from Universidad Nacional de Colombia, located at Medellín-Colombia, are considered. The results obtained demonstrate the effectiveness of the energy management strategy, and in this way, enable to extend the battery lifetime and reduce the costs associated to the maintenance and disconnection of the microgrid in educational buildings or other applications focused on this type of DC microgrid.

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Section: Devices and Control Strategiesmentioning

confidence: 99%

Section: Devices and Control Strategiesmentioning

confidence: 99%

Energy Management in PV Based Microgrids Designed for the Universidad Nacional de Colombia

et al. 2020

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“…In this paper, only the operation mode in which multiple converters are connected in parallel to maintain the bus voltage is considered. The PV source would be integrated into the bus by maximum power point tracking control, and it can be considered as a special constant power load whose output power is negative and stochastic because of its similar external characteristics with constant power load [31]. In traditional ac microgrids, power converter-based units are coordinated together with a frequency-droop controller as well [2,4,5].…”

Section: Overall Descriptionmentioning

confidence: 99%

A Novel Autonomous Current-Sharing Control Strategy for Multiple Paralleled DC–DC Converters in Islanded DC Microgrid

et al. 2019

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Due to the existence of line impedances and low-bandwidth communication, the traditional peer-to-peer control method based on droop control has difficult meeting the requirements of current sharing and voltage stability in islanded DC microgrids at the same time. In this paper, a novel current-sharing control strategy based on injected small ac voltage with low frequency and low amplitude is proposed for multiple paralleled DC-DC converters. The small ac voltage is superimposed onto the output voltage of each converter. Then, the reactive circulating power is generated and used to regulate the output DC voltage of each converter. Under the droop characteristic between the injected frequency and output DC current, a feedback mechanism is generated to realize the accurate current sharing. On this basis, a reactive power-voltage limiter link and virtual negative impedance are added. Under the interaction of the two links, the bus voltage drop caused by line impedances can be almost completely eliminated. This method does not need any communication or to change the hardware structure. The controller design process is presented in detail along with a system stability analysis. Finally, the feasibility and effectiveness of the proposed control strategy are validated by the results obtained from simulations and experiments.

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“…In [18]- [21], the concept of virtual impedance/admittance shaping is introduced as an intuitive way to mitigate the effect of negative impedance loads. Other contributions with similar aims, such as [22]- [24], induce a stabilizing damping component using feedback controllers.…”

Section: Introductionmentioning

confidence: 99%

Data-Driven Control of LVDC Network Converters: Active Load Stabilization

Ruiz-Martinez

Mayo-Maldonado

Escobar

et al. 2020

IEEE Trans. Smart Grid

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This paper addresses the (model-free) data-driven control of power converters, acting as distributed generators, in low voltage direct current (LVDC) networks (e.g. DC microgrids, DC distributed power systems, DC buses wit multiple sources and loads, etc.). Since traditional stand-alone control design, cannot guarantee stability when converters are connected to a network, it is proposed a deterministic solution that does not require the network model-an approach purely based on measurement data. This is a suitable way to overcome common issues when using a model-based approach, e.g. the use of an excessive number of variables and equations, the presence of un-modeled dynamics, unknown parameters and/or the lack of first principle model equations. To corroborate the advantages of the proposed approach, the present work addresses an extreme but also realistic scenario: weak networks with active loads, such as constant power loads (CPLs). It is also shown that the proposed scheme guarantees stability in a rigorous deterministic way-using a Lyapunov approach based on coefficient matrices directly constructed from data. Simulation results using a multibus LVDC distribution network, based on PSCAD/EMTDC, are provided as proof of concept. Index Terms-Data-driven control, distributed generators, LVDC networks, DC microgrids, DC buses, oscillations, stability, constant power loads. Recent contributions of model-based approaches include: [11]-[13], where feedback control techniques are proposed to stabilize power converters in the presence of CPLs. In [2],

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Stability Analysis and Damping Enhancement Based on Frequency-Dependent Virtual Impedance for DC Microgrids

Cited by 147 publications

References 44 publications

Energy Management in PV Based Microgrids Designed for the Universidad Nacional de Colombia

Energy Management in PV Based Microgrids Designed for the Universidad Nacional de Colombia

A Novel Autonomous Current-Sharing Control Strategy for Multiple Paralleled DC–DC Converters in Islanded DC Microgrid

Data-Driven Control of LVDC Network Converters: Active Load Stabilization

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