An Active Voltage Stabilizer for a Generic DC Microgrid
01 Sep 2019-
TL;DR: This paper analyzes the low frequency stability chal-lenges that exist in a generic DC microgrid system and proposes a capacitive energy storage system based active voltage stabilizer, that handles the power fluctuations within the system during transient conditions.
Abstract: This paper analyzes the low frequency stability chal-lenges that exist in a generic DC microgrid system. The conditions for system stability are derived from fundamental principles. A capacitive energy storage system based active voltage stabilizer, that handles the power fluctuations within the system during transient conditions, is proposed to stabilize the DC microgrid. The functionality of the active stabilizer, based on a bidirectional DC-DC converter, is elucidated and a suitable control strategy is proposed. The proposed active stabilizer and its associated control system involves only local voltage sensing and does not alter the generic DC microgrid structure. The proposed approach is validated through analytical models and circuit simulations. A dual active bridge (DAB) converter based active stabilizer is implemented and hardware based experimental results from a laboratory test-bench are provided to validate functionality and effectiveness of the proposed approach.
Citations
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TL;DR: In this paper, a hardware-based active voltage stabilizer solution is proposed to stabilize the DC microgrid (MG) system, and the active stabilizer and its associated control configuration involve only local voltage sensing and are nonintrusive.
Abstract: This paper analyzes the low-frequency stability challenges that exist in a complex DC microgrid (MG) system. The converters that belong to a DC MG are categorized into different groups based on their control approach. The small-signal model of the DC MG is presented, and the conditions for system stability are derived. In some DC MG applications, there is the possibility of installing off-the-shelf converters with little flexibility and access for controller auto-tuning. To tackle this, a hardware-based active voltage stabilizer solution is proposed to stabilize the DC MG. The active stabilizer’s functionality, based on an isolated bidirectional DC-DC converter, is elucidated, and a suitable control strategy is proposed. The active stabilizer and its associated control configuration involve only local voltage sensing and are non-intrusive. A dual active bridge (DAB) converter-based active stabilizer is implemented, and hardware-based steady-state and transient experimental results from a DC MG test-bench are provided to validate the functionality and effectiveness of the proposed active stabilizer.
6 citations
18 Nov 2022
TL;DR: In this article , a voltage regulator made of triangles is used to switch the load of an electrical device in 10 ms. This stabilizing device is not very sensitive to changes in voltage supplied through the common line, and voltage smoothing is done if the input voltage is in the range of 130 to 270 volts.
Abstract: Electrical devices react negatively to such variations of the network and quickly fail when they lose their inherent functions. To avoid such effects, people use homemade devices called voltage regulators. A useful stabilizer is a device made of triangles. There are tolerances for voltage change greater than 10 % of the nominal value (220 V). This deviation should be observed both upwards and downwards. But there is no ideal power network, the voltage value in the network changes frequently, thereby worsening the performance of the devices connected to it. This stabilizing device is not very sensitive to changes in voltage supplied through the common line. Voltage smoothing is done if the input voltage is in the range of 130 to 270 volts. Devices connected to the network are powered by a voltage of 205 to 230 volts. From such a device it is possible to operate electrical appliances, the total power of which is up to 6 kW. The stabilizer switches the load of the consumer in 10 ms.
18 Nov 2022
TL;DR: In this article , a voltage regulator made of triangles is used to smooth the voltage in the common line of an electrical device. But there is no ideal power network, the voltage value in the network changes frequently, thereby worsening the performance of the devices connected to it.
Abstract: Electrical devices react negatively to such variations of the network and quickly fail when they lose their inherent functions. To avoid such effects, people use homemade devices called voltage regulators. A useful stabilizer is a device made of triangles. There are tolerances for voltage change greater than 10% of the nominal value (220 V). This deviation should be observed both upwards and downwards. But there is no ideal power network, the voltage value in the network changes frequently, thereby worsening the performance of the devices connected to it. This stabilizing device is not very sensitive to changes in voltage supplied through the common line. Voltage smoothing is done if the input voltage is in the range of 130 to 270 volts. Devices connected to the network are powered by a voltage of 205 to 230 volts. From such a device it is possible to operate electrical appliances, the total power of which is up to 6 kW. The stabilizer switches the load of the consumer in 10 ms.
TL;DR: A novel DC Power System Stabilizer is proposed which is connected to a DC bus as a separate module passivizing the bus impedance at non-passive interaction frequencies to provide an online stability measure in terms of the DC bus impedance characteristics.
Abstract: High penetration of Power Electronic (PE) converters in DC power grids has caused new stability challenges due to dynamic interactions among a network’s subsystems. Dynamic interactions can be avoided by the impedance coordination between the subsystems through the modification of control loops or passive elements inside a grid. Impedance coordination is a very complex and time-consuming task with no adaptations to dynamic changes in a power grid. In this paper, the concepts of dynamic interaction and passivity are explained and combined together to provide an online stability measure in terms of the DC bus impedance characteristics. A novel DC Power System Stabilizer (PSS) is proposed which is connected to a DC bus as a separate module passivizing the bus impedance at non-passive interaction frequencies. The interaction frequencies are detected through a broadband online identification process. The PSS working principle, topology, modeling, and control designs are explained in detail. Finally, the functionality and performance of the proposed stabilizer are validated by simulation results.
Cites background from "An Active Voltage Stabilizer for a ..."
...The idea of centralized stabilizer has been proposed in [26] for the modification of the source-side impedance....
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References
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01 Jan 1976
1,224 citations
"An Active Voltage Stabilizer for a ..." refers background in this paper
...One of the popular ways to understand these interations is to analyze the smallsignal power electronic converter impedances [1]....
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TL;DR: In this article, stability issues in dc microgrids with instantaneous constant-power loads (CPLs) are explored and mitigation strategies such as load shedding, adding resistive loads, filters, or energy storage directly connected to the main bus, and control methods are investigated.
Abstract: This paper explores stability issues in dc microgrids with instantaneous constant-power loads (CPLs). DC microgrids typically have distributed power architectures in which point-of-load converters behave as instantaneous CPLs to line regulating converters located upstream. Constant-power loads introduce a destabilizing effect in dc microgrids that may cause their main bus voltages to show significant oscillations or to collapse. This paper also discusses stabilization strategies to prevent these undesired behaviors from occurring. Mitigating strategies such as load shedding, addition of resistive loads, filters, or energy storage directly connected to the main bus, and control methods are investigated. Advantages and disadvantages of these methods are discussed and recommendations are made. The analysis is verified with simulations and hardware-based experiments.
538 citations
"An Active Voltage Stabilizer for a ..." refers background in this paper
...Tightly regulated point of load (POL) converters (DC/DC or DC/AC types) in a DC microgrid act as constant power loads (CPL) with a negative incremental resistance [3], [4]....
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TL;DR: The implementation of novel active-damping techniques on dc/dc converters has been shown and the proposed active- damping method is used to overcome the negative impedance instability problem caused by the CPLs.
Abstract: Multi-converter power electronic systems exist in land, sea, air, and space vehicles. In these systems, load converters exhibit constant power load (CPL) behavior for the feeder converters and tend to destabilize the system. In this paper, the implementation of novel active-damping techniques on dc/dc converters has been shown. Moreover, the proposed active-damping method is used to overcome the negative impedance instability problem caused by the CPLs. The effectiveness of the new proposed approach has been verified by PSpice simulations and experimental results.
422 citations
"An Active Voltage Stabilizer for a ..." refers background in this paper
...microgrid to prevent any undesirable impedance interactions that can destabilize the system [3], [7]....
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...Tightly regulated point of load (POL) converters (DC/DC or DC/AC types) in a DC microgrid act as constant power loads (CPL) with a negative incremental resistance [3], [4]....
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TL;DR: In this paper, the authors reviewed all the major stability criteria for dc distribution systems that have been developed so far: the Middlebrook Criterion, the Gain Margin and Phase Margin (GMP), the Opposing Argument Criterion (OAC), the Energy Source Analysis Consortium (ESAC), and the Three-Step Impedance Criterion.
Abstract: Power-electronics-based dc power distribution systems, consisting of several interconnected feedback-controlled switching converters, suffer from potential degradation of stability and dynamic performance caused by negative incremental impedances due to the presence of constant power loads. For this reason, the stability analysis of these systems is a significant design consideration. This paper reviews all the major stability criteria for dc distribution systems that have been developed so far: the Middlebrook Criterion, the Gain Margin and Phase Margin Criterion, the Opposing Argument Criterion, the Energy Source Analysis Consortium (ESAC) Criterion, and the Three-Step Impedance Criterion. In particular, the paper discusses, for each criterion, the artificial conservativeness characteristics in the design of dc distribution systems, and the formulation of design specifications that ensure system stability. Moreover, the Passivity-Based Stability Criterion is discussed, which has been recently proposed as an alternative stability criterion. While all prior stability criteria are based on forbidden regions for the polar plot of the so-called minor loop gain, which is an impedance ratio, the proposed criterion is based on imposing passivity of the overall bus impedance. A meaningful simulation example is presented to illustrate the main characteristics of the reviewed stability criteria.
347 citations
"An Active Voltage Stabilizer for a ..." refers background or methods in this paper
...Conditions 3 and 4 are referred to as minor loop gain criterion and passivity criterion respectively in popular literature [2]....
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...Different methods have been proposed in literature to assess the stability of multi-converter systems based on these small-signal impedances [2]....
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TL;DR: Three simple and computationally efficient active damping solutions that can be implemented to stabilize a controlled voltage-source converter (VSC) interfacing a dc- microgrid to an ac system are proposed.
Abstract: DC microgrids are gaining high momentum under the smart grid environment. DC microgrid stability can be an issue under high penetration of tightly regulated power converters used to interface distributed resources and loads. This paper addresses dc microgrid stability under high penetration of tightly regulated power electronic converters; and proposes three simple and computationally efficient active damping solutions that can be implemented to stabilize a controlled voltage-source converter (VSC) interfacing a dc- microgrid to an ac system. The proposed active damping methods depend on reshaping the VSC impedance by injecting internal-model-based active damping signal at the outer, intermediate and inner control loops of the voltage-oriented VSC interface. Small signal analysis is conducted to assess the system stability under different compensation schemes. Moreover, the reshaped source impedance of the VSC interface and the modified voltage-tracking dynamics are derived under different compensation schemes. Sensitivity and robustness analyses are provided to assess the dynamic coupling among active damping and voltage tracking controllers. Evaluation results, based on a detailed model of a dc microgrid with multiple tightly regulated converter-interfaced loads, are provided to validate the developed models and demonstrate the effectiveness and robustness of proposed techniques.
210 citations
"An Active Voltage Stabilizer for a ..." refers background in this paper
...microgrid to prevent any undesirable impedance interactions that can destabilize the system [3], [7]....
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