Active Voltage Regulation Research Articles

Enhanced Active Voltage Regulation Capability for Three-Level NPC Converters with the Space Vector Modulation Method

Enhanced Active Voltage Regulation Capability for Three-Level NPC Converters with the Space Vector Modulation Method

Consensus-Based Model Predictive Control for Active Power and Voltage Regulation in Active Distribution Networks

In this paper, a consensus-based model predictive control (Cb-MPC) scheme is proposed to control the active power and voltage at all nodes in grid-connected active distribution networks (ADNs) with multiple distributed energy resources (DERs). The proposed design methodology is based on a multiple-input multiple-output (MIMO) model of an ADN which accounts for both the internal and external interactions among the control loops of the DERs. To achieve the control objective, each DER unit is equipped with a controller–observer system. In particular, the observer implements the consensus algorithm to estimate the collective system state by exchanging data only with its neighbors. The scope of the controller is to solve the MPC optimal problem based on its collective state estimate, and, due to the presence of an integral term in the control action, it is robust against any unknown scenarios of the ADN, which are represented by uncertainty in the model parameters. The results of numerical simulations validate the effectiveness of the proposed method in the presence of unknown changes in the operating conditions of the ADN and of communication using a sample and hold function.

Achieving grid resilience through energy storage and model reference adaptive control for effective active power voltage regulation

This article presents a comprehensive examination of the utilization of energy storage units for voltage regulation in grids. Specifically, the focus is on the practical implementation of active power control using a Model Adaptive Control (MRAC) algorithm. The article provides a detailed description of the algorithm, considering grid parameters and showcasing the practical application of voltage regulation through energy storage active power control using MRAC. The results of implementing an energy storage unit for global voltage regulation are discussed, highlighting the advantages and superiority of this method.

A combined regulation method of transient power angle stability control and fault current suppression for VSG

When a serious grid fault occurs, a virtual synchronous generator (VSG) tends to lose transient power angle stability (TPAS) and cause the fault current to exceed the limit. Most existing research usually neglects the inherent relationship between transient power angle instability (TPAI) and fault over-current (FOC), which leads to the two problems being solved separately rather than simultaneously. In this paper, the transient power angle and fault current characteristics of VSG are first studied, and the causes and influencing factors of TPAI and FOC are explored. Then, the TPAS analysis is carried out based on the phase portrait theory. A TPAS control method for VSG considering fault current suppression (FCS) is proposed. This method is fulfilled by the combined regulation of active power reference and reactive voltage regulation coefficient, in which the reference and coefficient can be adjusted adaptively according to different fault degrees and application scenarios. In addition, a quasi-static approximate (QSA)virtual inductance is introduced to limit the instantaneous inrush current (IIC). The proposed method achieves both the TPAS and FCS at the same time during the fault. Finally, simulations and experiments verify the correctness of the theoretical analysis and the proposed method.

Maximum Power Tracking of Photovoltaic Modules Based on Fuzzy Logic Employing Four-Phase Intervaled Boost Converter

Currently, there are significant investments in the study of distributed generation, including solar energy by the photovoltaic conversion method. Basically, a cell directly converts solar energy to electricity. For this, static converters are required. However, relevant issues arise in this process: point of maximum efficiency of module generation, strategy of control of the flow of energy to the network. The aim of this work is to monitor the main variables of a photovoltaic system, specifically the voltage and current module and their derivates. The goal is to implement the maximum power tracking technique using Fuzzy logic. In addition, the energy provided by the cell will be employed in an inverter stage that can operate as an active filter, voltage regulator, or generator of reactive and active power. The feasibility of using Fuzzy logic will also be studied. The first stage of this work involves parameterization and simulation of photovoltaic modules. The initial study examines the compatibility of a commercial module and its catalog data with the results of simulation. The simulated I-V characteristics show almost identical results to the catalog data. In sequence, a boost or lift DC-DC converter is employed to emulate variable load for maximum power transfer.

Quantum Mode Series Resonant Converter Utilized as Active Voltage Regulator of a Split DC Bus Capacitor

Quantum Mode Series Resonant Converter Utilized as Active Voltage Regulator of a Split DC Bus Capacitor

Towards Maximizing Hosting Capacity by Optimal Planning of Active and Reactive Power Compensators and Voltage Regulators: Case Study

Improving the performance of distribution systems is one of the main objectives of power system operators. This can be done in several ways, such as network reconfiguration, system reinforcement, and the addition of different types of equipment, such as distributed generation (DG) units, shunt capacitor banks (CBs), and voltage regulators (VRs). In addition, the optimal use of renewable and sustainable energy sources (RSESs) has become crucial for meeting the increase in demand for electricity and reducing greenhouse gas emissions. This requires the development of techno-economic planning models that can measure to what extent modern power systems can host RSESs. This article applies a new optimization technique called RUN to increase hosting capacity (HC) for a rural Egyptian radial feeder system called the Egyptian Talla system (ETS). RUN relies on mathematical concepts and principles of the widely known Runge–Kutta (RK) method to get optimal locations and sizes of DGs, CBs, and VRs. Furthermore, this paper presents a cost-benefit analysis that includes fixed and operating costs of the compensators (DGs, CBs, and VRs), the benefits obtained by reducing the power purchased from the utility, and the active power loss. The current requirements of Egyptian electricity distribution companies are met in the formulated optimization problem to improve the HC of this rural system. Uncertain loading conditions are taken into account in this study. The main load demand clusters are obtained using the soft fuzzy C-means clustering approach according to load consumption patterns in this rural area. The introduced RUN optimization algorithm is used to solve the optimal coordination problem between DGs, CBs, and VRs. Excellent outcomes are obtained with a noteworthy reduction in the distribution network power losses, improvement in the system’s minimum voltage, and improvement of the loading capacity. Several case studies are investigated, and the results prove the efficiency of the introduced RUN-based methodology, in which the probabilistic HC of the system reaches 100% when allowing reverse power flow to the utility. In comparison, this becomes 49% when allowing reverse power to flow back to the utility.

Droop-based active voltage regulation control and robust stability analysis for VSCs in the large-scale RES-integrated power system

New features like high penetration level, low inertia, and weak damping are decreasing voltage support capacity in the power system as it sees large-scale renewable energy source (RES) integration continuously. The reasonable solution to this challenge is developing an additional active voltage regulation function for voltage source converters (VSCs). This study proposes a droop-based active voltage control strategy for VSCs in large-scale RES-integrated power systems to make VSCs continue to operate and regulate the voltage at the point of common coupling (PCC) during a fault without causing overcurrent. In order to meet the requirements of RESs and grid code, all control boundary conditions are designed based on practical engineering data. Meanwhile, plant uncertainty and parameter disturbance are introduced into a robust stability margin analysis model based on the component connection method (CCM) and structured singular value (SSV) to improve the engineering application prospect. The effectiveness and feasibility of this control strategy are proved by logical deduction and practical simulation based on a generalized small-signal model.

Three-phase Active Tracking AC-AC Voltage Regulator based on Buck Converter with an Efficient Hybrid Control Technique

This study proposes a switch-mode three-phase active tracking AC-AC voltage regulator based on the buck converter. The regulator topology incorporates a moderate number of components with less complexity and high efficiency. An efficient hybrid control technique, based on a closed-loop PID controller that is supported with a new designed feedforward controller, is proposed for the regulator control different to the similar studies in the literature. The hybrid control technique augments the response of active tracking of the reference output phase voltages to achieve an improved quality close to sine-wave output phase voltages for either the input AC phase voltages that are ideal pure sine-wave or include various harmonics. The regulator topology has a modular structure for independent control of each output phase. So, the regulator can help to achieve close to sine-wave output phase voltages to supply a balanced/unbalanced wye-connected three-phase load or independent single-phase loads. The presented three-phase regulator and the control technique are tested with simulation and experimental studies. The laboratory set-up of the regulator is designed for 2.2 kW output power, 0-300 Vp input phase voltages (50 Hz), and 0-200 Vp output phase voltages. The results demonstrated that the proposed switch-mode three-phase buck-type active tracking voltage regulator can provide the desired AC phase voltages with less than 5% THD (total harmonic distortion) and low harmonics for different operating conditions.

Architecture design of battery energy storage coordinated control system based on Multi-Agent mechanism

Abstract Energy storage can realize rapid voltage, frequency support and energy adjustment, and is an important guarantee for promoting the efficient consumption of renewable energy and the safe and stable operation of the power system. The flexible adjustment of energy storage is not only affected by its own characteristics, but also closely related to the operation control mode of energy storage. Based on the PQ constant power and virtual synchronization control strategy of the battery energy storage system, this paper constructs the operation architecture of the battery energy storage system based on the Multi-Agent cooperative mechanism, and further gives the energy storage system Multi-Agent cooperative control system’s application scenarios in active frequency modulation and reactive voltage regulation. Research shows that this architecture helps to fully tap the potential of aggregation and regulation of multi-point decentralized energy storage facilities and meet the flexible regulation needs of the power system under the access of high-permeability intermittent renewable energy.

Boost Converter Based 3-phase AC-AC Active Tracking Voltage Regulator Controlled by a Robust Hybrid Control Method

In this study, a switch-mode three-phase active tracking AC-AC voltage regulator based on the boost converter is proposed with a moderate number of active and passive elements used in the topology. A robust hybrid control, where a novel designed feedforward controller supports the closed-loop PID controller, is proposed for the control of the regulator apart from similar studies in the literature. Active tracking response of the reference output phase voltages is augmented by the proposed hybrid control method. Thus nearly close to sine-wave output phase voltages can be obtained, whether the input AC phase voltages are ideal pure sine or not. Also, the modular structure of the regulator topology enables independent control for each output phase. Thus, the supply of balanced/unbalanced wye-connected three-phase loads or independent single-phase loads with nearly close to ideal sine wave voltages can be achieved by the modularity of the regulator. Both experimental and simulation test studies are performed for the proposed regulator system. A laboratory set-up for the regulator is designed for 0-200 Vp input phase voltages (50 Hz), and 0-300 Vp output phase voltages, and 1.8 kW output power. The achieved results for both simulation and experimental tests verify the proposed switch-mode boost-type regulator’s ability to provide output phase voltages nearly close to sine wave with total harmonic distortion (THD) values under 5%.

Design and field implementation of smart grid-integrated control of PV inverters for autonomous voltage regulation and VAR ancillary services

Ancillary services from Photovoltaic (PV) inverters can increase distribution system flexibility and alleviate the voltage regulation challenges associated with high PV penetration levels. However, the required communication infrastructure and smart grid integration challenges limit the broad deployment of PV ancillary services. This paper presents a cost-effective volt/var control (VVC) of multi-string PV inverters for active voltage regulation and reactive power dispatch using the existing smart distribution infrastructure to avoid the upfront costs of providing PV ancillary services. The proposed VVC model is developed in MATLAB/Simulink to adapt PV reactive power compensation according to the X/R characteristics of the distribution feeder. An IEC 61131-3 compliant prototype is designed based on Simulink PLC code and deployed to a commercially available remote terminal unit (RTU) using CODESYS standardization tool to address smart grid integration challenges. The proposed VVC scheme is tested in a real-world grid-connected PV system with multi-string inverters for experimental validation. Quasi-static time-series simulation and experimental results demonstrate the validated effectiveness of the proposed control scheme in controlling fast PV fluctuations, resolving voltage violations, voltage flickers, and enabling higher PV penetration.

Reliability-Enhanced Hybrid Grounding System Based on Active Neutral-Point Voltage Regulator and Low-Resistance

-In urban distribution networks, due to its strong reliability and simple operation, the low-resistance grounding system has gradually replaced the resonance grounding system represented by Petersen coil. However, when a high-resistance ground fault occurs, it is difficult for the low-resistance grounding system to identify the smaller fault characteristics, and the zero-sequence protection device cannot ensure the system reliability. In this letter, a hybrid grounding system (HGS) combining the active neutral-point voltage regulator (NVR) and low-resistance is proposed. By injecting compensation voltage into the neutral point, the fault phase voltage can be reduced below the threshold that can generate a fault arc. Additionally, the proposed coordinated control strategy can effectively switch between the two operation modes (active NVR and low-resistance) according to the actual fault types. Simulation and experimental results verify the rationality and effectiveness of the proposed concept and analysis.

Optimal Planning of a Distribution Network in Egypt

Distribution networks planning is a very complex task as it involves the consideration of various important issues. A model for optimal planning of a distribution network is presented in detail, using Distributed Generation (DG). This paper presented a detailed analysis of the West Delta Network (WDN) as a part of the Egyptian distribution network with a 30% increase in system loading. An Oscillatory Particle Swarm Optimization (OPSO) technique was used to find the optimal locations and sizes of one DG or multiple DGs for achieving the objectives of minimizing total active power losses and system voltage regulation as a single-and-multi-objective optimization problem in a distribution network. Several penetration scenarios have done to evaluate concentrated (at one location) and distributed DGs (at different locations). The results are presented in a comparative form and thoroughly discussed. The obtained results will help in system operation with DG integration and identifying the critical penetration levels for the studied system.

Buck-type Single-phase AC-AC Active Tracking Voltage Regulator Controlled by an Enhanced Hybrid Control Method

In this paper, a single-phase switch-mode buck-type AC-AC voltage regulator is presented with reduced numbers of elements which are used in the topology. Apart from similar studies in the literature, a new hybrid control method which is structured by the closed-loop PID controller and a new enhanced feedforward controller is used for the control of the regulator. The hybrid controller improves the active tracking capability of the reference to achieve an output voltage as close to the sine-wave with high quality. The input AC voltage may be an ideal sine wave or it may include harmonics. Both simulation and experimental tests are applied for the proposed regulator controlled by this control method. The experimental set-up for the regulator is designed for 0-200 Vp input voltage (50 Hz), 0-100 Vp output voltage, and 0.6 kW output power. The results proved the capability of the proposed buck-type switch-mode regulator to achieve the requested output voltage as near as possible to sine wave. The obtained output voltages for different load conditions and input-output parameters have less than 5% THD (total harmonic distortion) and high quality.

A New Current Source Converter Using AC-Type Flying-Capacitor Technique

Entering the new millennium, current source converters (CSCs) have drawn increasing attention not only for high-power but also some emerging low-power applications which prefer the inherent voltage boosting nature and low dv/dt on ac-side. However, the dc-link quality of CSC has not been well improved and is rarely discussed in literature. To fill this gap, a new type of CSC topology is proposed in this article through the isomorphic theory. It utilizes the ac-type flying capacitors in each phase leg and provides alternative commutation loops, which can reduce the dc-side dv/dt and improve the common-mode voltage simultaneously. Besides, this technique can increase the withstand voltage of the converter without series connections of switching devices. Different from the voltage-source converter type, the flying capacitor voltage in CSC should be maintained as ac voltage, thus, active voltage regulation is necessary. To deal with such a challenge, carrier-based pulsewidth modulation with flying capacitor voltage regulation is also developed in this work. Compared with the traditional device-series-connected CSC topologies, the numbers of active switches and the device blocking voltage can remain the same, while the ac-type flying capacitors are added in the proposed topology to gain all the above merits. Simulation and experiment results are obtained to verify the advantages of this new type of CSC topology.

Multiterminal HVDC System with Power Quality Enhancement

High-Voltage Direct Current (HVDC) systems are a feasible solution that allows the transmission of energy between several power networks. As a consequence of the use of HVDC systems, renewable energy sources can be integrated more easily into distribution grids and smart grids. Furthermore, HVDC systems can contribute to improving the power quality (PQ) of the grids to which they are connected. This paper presents a multiterminal HVDC system that not only controls the flows of active power between four different networks, but also compensates imbalances and harmonics in the grid currents to maintain balanced and sinusoidal voltages at the point of common coupling of the various grids. The compensation is carried out by the voltage-source converters (VSCs) connected to their respective AC grids. A control scheme based on the use of resonant regulators and proportional–integral (PI) controllers is responsible for of achieving the necessary power flow control with the amelioration of the PQ. A case study of a multiterminal HVDC system that comprises four terminals sharing a DC bus of 80 kV is simulated by means of PSCADTM/EMTDCTM (Power System Computer-Aided Design; Electromagnetic Transients including Direct Current), where the AC grids associated with the terminals suffer from voltage imbalances and voltage harmonics owing to the connection of unbalanced loads and nonlinear loads. The obtained simulation results show the performance of the complete system in terms of active power flow, voltage regulation, and harmonic distortions of the grid current and the grid voltage.

The Frequency- and the Time-Domain Design of a Dual Active Bridge Converter Output Voltage Regulator Based on the D-Decomposition Technique

Commonly used variants of the proportional-integral, PI, and the integral-proportional, IP, compensator gains selections, merged with the $\mathfrak {D}$ -decomposition technique are presented in this paper. The motivation to this work is the willingness to check whether such a combination can lead to unified and perhaps simplified approach in this matter. Therefore, the $\mathfrak {D}$ -decomposition technique has been effectively combined with the frequency- and the time-domain driven requirements regarding the control dynamics. Criteria such as the gain- and phase-margins, $(GM, PM)$ , the sensitivity, $M_{\text {S}}$ , the pole placements by means of the $(\sigma, \omega _{\text {d}})$ and the $(\xi, \omega _{\text {n}})$ , and the overshoot with the rise time $(\delta, t_{\text {r}})$ are considered. It has been shown that the control design effort can be reduced by the means of the $\mathfrak {D}$ -decomposition to intuitive judgments in the proportional and integral gains coordinates $(K_{\text {P}}, K_{\text {I}})$ with parametric curves. As such it can be thought of as a promising scenario in a case considered. The analyses are presented and discussed in details. They are conducted basing on example of output voltage closed loop control of the Dual Active Bridge, DAB, converter. The circuit operates under the phase shift control scheme. The control-to-output transfer function identification and the control circuit delays are included in the analyses. The case analysis have shown that the time domain requirements are less effectively met with the PI regulator when compared to its IP configuration. This is due to the commonly used simplifications during conversion between the $(\xi, \omega _{\text {n}})$ and the $(\delta, t_{\text {r}})$ in presence of uncompensated zero of the closed loop transfer function. The paper contains complete and intelligible approach to dedicated mathematical investigations verified experimentally.

A Power-Decoupled Current-Source Inverter for PV Energy Harvest and Grid Voltage Regulation

The single-phase microinverter (SMI) is becoming one of the most cost-efficient interfaces for bridging photovoltaics (PV) and power systems. However, in the maximum power point tracking operation, the SMI injects an intermittent active power to the grid, which leads to voltage variations at the point of common coupling (PCC). This certainly dampens the power quality of grids. Besides, the power mismatch between the dc and ac terminals of SMIs will render a double-line-frequency pulsating power at the dc terminal, which inevitably increases the power ratings of the circuit components of the SMIs. To address these issues simultaneously, a power-decoupled current-source inverter (PD-CSI) is proposed in this article. The PD-CSI can provide the required reactive power compensation for regulating the PCC voltage. Meanwhile, it is imbedded with an active power decoupling circuit, which can actively store the double-line-frequency pulsating power in a film capacitor so that the PV can be operated at a constant dc current. The state-space model and steady-state operation of the PD-CSI are elaborated. The controllers are designed for achieving the active power decoupling operation and the PCC voltage stabilization. Experimental and simulation results in an 110-V ac microgrid have been provided to validate the simultaneous functionalities of the active power decoupling and grid voltage regulation for the proposed PD-CSI.

Distribution feeder costs as a function of the penetration of distributed generation – key drivers and trends

Distributed generation (DG) has experienced extraordinary growth in installed capacity in many countries. DG can have a significant impact on both the investment and operational costs of distribution feeders. However, in many contexts, such impact is still not clear. Moreover, the impact of DG could be positive or negative and could be different for different levels of DG penetration. This paper proposes a high-level approach to estimate the cost of distribution feeders as a function of the DG penetration scenario, for different types of medium voltage grids. Grid scenarios include urban and rural feeders, intermittent and conventional DG technologies, different distributions of loads and DG along the feeder, and passive and active voltage regulation. For each grid scenario, we build the curve of total feeder cost as a function of the penetration of DG. We identify the levels of the penetration that create savings and the levels that drive additional costs. We find that, for all the explored medium voltage grids, DG creates savings for low penetration scenarios, but increases the total feeder cost for higher penetrations, which is largely driven by the increase in power losses. We finally discuss the possible policy implications of the resulting cost curves.