Showing papers on "Voltage regulator published in 2018"

A Novel Distributed Secondary Coordination Control Approach for Islanded Microgrids

Abstract: This paper develops a new distributed secondary cooperative control scheme to coordinate distributed generators (DGs) in islanded microgrids (MGs). A finite time frequency regulation strategy containing a consensus-based distributed active power regulator is presented, which can not only guarantee the active power sharing but also enable all DGs’ frequencies to converge to the reference value within a finite time. This enables the frequency and voltage control designs to be separated. Then an observer-based distributed voltage regulator involving certain reactive power sharing constraints is proposed, which allows different set points for different DGs and, thus, accounts for the line impedance effects. The steady-state performance analysis shows that the voltage regulator can accurately address the issue of global voltage regulation and accurate reactive power sharing. Moreover, all the distributed controllers are equipped with bounded control inputs to suppress the transient overshoot, and they are implemented through sparse communication networks. The effectiveness of the control in case of load variation, plug-and-play capability, communication topology change, link failure, time delays, and data drop-out are verified by the simulation of an islanded MG in MATLAB/SimPowerSystems.

Real-Time Coordinated Voltage Control of PV Inverters and Energy Storage for Weak Networks With High PV Penetration

Abstract: There are more large-scale photovoltaic (PV) plants being established in rural areas due to availability of low-priced land. However, distribution grids in such areas traditionally have feeders with low X/R ratios, which makes the independent reactive power compensation method less effective on voltage regulation. Consequently, upstream step voltage regulator (SVR) may suffer from excessive tap operations with PV-induced fast voltage fluctuations. Although a battery energy storage system (BESS) can successfully smooth PV generation, frequent charge/discharge will substantially affect its cost effectiveness. In this paper, a real-time method is designed to coordinate PV inverters and BESS for voltage regulation. To keep up with fast fluctuations of PV power, this method will be executed in each 5 s control cycle. In addition, charging/discharging power of BESS is adaptively retuned by an active adjustment method in order to avoid BESS premature energy exhaustion in a long run. Finally, through a voltage margin control scheme, the upstream SVR and downstream PV inverters and BESS are coordinated for voltage regulation without any communication. This research is validated via a real-time digital simulator MatLab cosimulation platform, and it will provide valuable insights and applicable strategies to both utilities and PV owners for large-scale PV farm integration into rural networks.

A Multi-Functional Fully Distributed Control Framework for AC Microgrids

Abstract: This paper proposes a fully distributed control methodology for secondary control of ac microgrids. The control framework includes three modules: 1) voltage regulator; 2) reactive power regulator; and 3) active power/frequency regulator. The voltage regulator module maintains the average voltage of the microgrid distribution line at the rated value. The reactive power regulator compares the local normalized reactive power of an inverter with its neighbors’ powers on a communication graph and, accordingly, fine-tunes Q-V droop coefficients to mitigate any reactive power mismatch. Collectively, these two modules account for the effect of the distribution line impedance on the reactive power flow. The third module regulates all inverter frequencies at the nominal value while sharing the active power demand among them. Unlike most conventional methods, this controller does not utilize any explicit frequency measurement. The proposed controller is fully distributed; i.e., each controller requires information exchange with only its neighbors linked directly on the communication graph. Steady-state performance analysis assures the global voltage regulation, frequency synchronization, and proportional active/reactive power sharing. An ac microgrid is prototyped to experimentally validate the proposed control methodology against the load change, plug-and-play operation, and communication constraints such as delay, packet loss, and limited bandwidth.

Positive and Negative Sequence Control Strategies to Maximize the Voltage Support in Resistive–Inductive Grids During Grid Faults

Abstract: Grid faults are one of the most severe perturbations in power systems. During these extreme disturbances, the reliability of the grid is compromised and the risk of a power outage is increased. To prevent this issue, distributed generation inverters can help the grid by supporting the grid voltages. Voltage support mainly depends on two constraints: the amount of injected current and the grid impedance. This paper proposes a voltage support control scheme that joins these two features. Hence, the control strategy injects the maximum rated current of the inverter. Thus, the inverter takes advantage of the distributed capacities and operates safely during voltage sags. Also, the controller selects the appropriate power references depending on the resistive–inductive grid impedance. Therefore, the grid can be better supported since the voltage at the point of common coupling is improved. Several voltage objectives, which cannot be achieved together, are developed and discussed in detail. These objectives are threefold: to maximize the positive sequence voltage; to minimize the negative sequence voltage; and to maximize the difference between positive and negative sequence voltages. A mathematical optimal solution is obtained for each objective function. This solution is characterized by a safe peak current injection, and by the optimization of the voltage profile in any type of grid connection. Therefore, the proposed control scheme includes advanced features for voltage support during voltage sags, which are applicable to different power facilities in different types of networks. Due to system limitations, a suboptimal solution is also considered, analyzed, and discussed for each of the optimization problems. Experimental results are presented to validate the theoretical solutions.

Reduced DC-Link Voltage Active Power Filter Using Modified PUC5 Converter

Abstract: In this letter, the five-level packed U-cell (PUC5) inverter is reconfigured with two identical dc links operating as an active power filter (APF). Generally, the peak voltage of an APF should be greater than the ac voltage at the point-of-common coupling (PCC) to ensure the boost operation of the converter in order to inject harmonic current into the system effectively; therefore, full compensation can be obtained. The proposed modified PUC5 (MPUC5) converter has two equally regulated separated dc links, which can operate at no load condition useful for APF application. Those divided dc terminals amplitudes are added at the input of the MPUC5 converter to generate a boosted voltage that is higher than the PCC voltage. Consequently, the reduced dc-links voltages are achieved since they do not individually need to be higher than the PCC voltage due to the mentioned fact that their summation has to be higher than PCC voltage. The voltage balancing unit is integrated into the modulation technique to be decoupled from the APF controller. The proposed APF is practically tested to validate its good dynamic performance in harmonic elimination, ac-side power factor correction, reactive power compensation, and power quality improvement.

Distributed Control of Voltage Regulating Devices in the Presence of High PV Penetration to Mitigate Ramp-Rate Issues

Abstract: A distributed voltage control scheme is proposed in an active distribution network in the presence of a large scale photovoltaic (PV) farm/plant to mitigate high ramp-rate issues. Multiple voltage regulating devices, such as on-load tap changers, step voltage regulators (SVRs), and switched capacitors banks are controlled in various ways based on either a centralized or a distributed coordination management scheme. This paper presents the relationship of the active and reactive power outputs of a PV plant in the presence of the conventional voltage regulating devices, and proposes a distributed control strategy to coordinate the SVRs with the PV smart inverter’s capability to improve power quality. The distributed voltage control schemes are tested on an unbalanced medium voltage feeder located in a California utility service territory with the PV integrated at the far end of the feeder.

Improved Design and Control of FBSM MMC With Boosted AC Voltage and Reduced DC Capacitance

Abstract: Reducing the capacitance of submodules (SM) and handling short-circuit faults in HVdc systems are crucial for economical and reliable operation of modular multilevel converters (MMC). This paper proposes an SM capacitance reduction method for full-bridge submodule (FBSM)-MMC, which combines circulating current injection and ac voltage boosting. An optimized circulating current control method considering the limitation of fixed semiconductor current rating is introduced. By adding second-harmonic voltage to the reference arm voltage, the capacitor voltage ripple can be controlled to be a targeted value under all operating conditions. To further decrease the SM capacitor voltage ripples, the negative voltage state of FBSM is fully utilized to boost the ac voltage under fixed dc voltage with the modulation index up to 1.414. Consequently, the capacitance requirement for ac voltage boosting FBSM-MMC can be significantly reduced as compared to the conventional FBSM-MMC. Experimental results confirm the feasibility and validity of the proposed SM capacitance reduction method.

Hybrid-Bridge-Based DAB Converter With Voltage Match Control for Wide Voltage Conversion Gain Application

Abstract: This paper proposes a voltage match (VM) control for hybrid-bridge-based dual active bridge (DAB) converter in wide voltage conversion gain applications. With the addition of an auxiliary half-bridge circuit, the topology becomes an integration of a half-bridge and a full-bridge DAB converter. Unlike other pulse width modulation generation method for DAB converters, this converter utilizes four-level voltage at one port of the transformer to obtain matched voltage waveforms within the range of twice the minimum conversion gain. Wide conversion gain, decoupling of the two power control variables and wide zero-voltage switching (ZVS) ranges can be achieved with the proposed VM control. Full load ranges of ZVS for the six main power switches can be achieved and the two auxiliary switches can also operate in a wide ZVS range. In addition, the power control is done only using two control variables and its implementation is very simple, only needing a divider and a conventional voltage regulator. These characteristics and benefits of the proposed control are verified by experimental results from a 1-kw converter prototype.

Three-Level Quasi-Switched Boost T-Type Inverter: Analysis, PWM Control, and Verification

Abstract: In this paper, a three-level quasi-switched boost T-type inverter (3L qSBT2I) is proposed. A new pulse-width modulated (PWM) control method is presented to reduce the inductor current ripple of the qSBT2 I. In the introduced PWM technique, the shoot-through duty cycle is maintained constant to keep the modulation index as high as possible. Then, the only control parameters of the qSBT2I are the duty cycles of the two additional switches. By controlling the duty cycles of the two additional switches, the voltage gain of the proposed qSBT2 I can be improved to a value larger than that of the conventional 3L impedance source inverters. The steady-state analysis, operating principles, and comparisons with the impedance source-based 3L inverters are presented. A 1-kW prototype is constructed to verify the operating principle of the 3L qSBT2I. An indirect dc-link voltage regulator and a capacitor voltage-balance controller are applied to the proposed qSBT2I. Simulation and experimental results are presented.

A Digitally Controlled Fully Integrated Voltage Regulator With On-Die Solenoid Inductor With Planar Magnetic Core in 14-nm Tri-Gate CMOS

Abstract: A fully integrated digitally controlled two-phase buck voltage regulator (VR) with on-die solenoid inductors with a planar magnetic core is demonstrated in 14-nm tri-gate CMOS for fine-grained power delivery/management domains of high power density in system-on-chips while enabling ultra-thin (z-height) packages. The VR achieves 1-A/mm2 power density for 400-mA load current with a measured peak efficiency of 84% at 100-MHz switching frequency including a digital PWM with >9 bits (8 ps) of resolution.

Imbalance Mechanism and Balanced Control of Capacitor Voltage for a Hybrid Modular Multilevel Converter

Abstract: Due to different charging and discharging characteristics of full-bridge submodules and half-bridge submodules in hybrid modular multilevel converters (MMC), capacitor voltage imbalance will occur under boosted ac voltage or reduced dc voltage conditions. To address this issue, the mechanism of capacitor voltage imbalance is carefully studied, with three main factors—modulation index, power angle, and hybridization ratio—summarized and their effect on capacitor voltage imbalance analyzed. Further, a control strategy based on fundamental frequency reactive circulating current injection is proposed to keep the capacitor voltage balanced in the hybrid MMC. The amplitude and phase angle of the injected circulating current are calculated and their influence on the energy fluctuation in the submodules’ capacitors and the semiconductors’ current stress is explored. Experimental results under boosted ac voltage and reduced dc voltage conditions demonstrate the feasibility and validity of the proposed scheme.

An Enhanced State Observer for DC-Link Voltage Control of Three-Phase AC/DC Converters

Abstract: To regulate the dc-link voltage of three-phase ac/dc converters, an enhanced state observer-based controller is presented in this letter. The proposed controller, contrary to the traditional ones, does not require the dc-link current measurement and offers a “plug and play” capability, a rather high disturbance rejection ability and robustness against the dc-link capacitance parameter variation. The design procedure of the suggested controller is discussed, and its effectiveness is verified using experimental results.

Control Strategy for Distribution Generation Inverters to Maximize the Voltage Support in the Lowest Phase During Voltage Sags

Abstract: Voltage sags are considered one of the worst perturbations in power systems. Distributed generation power facilities are allowed to disconnect from the grid during grid faults whenever the voltage is below a certain threshold. During these severe contingencies, a cascade disconnection could start, yielding to a blackout. To minimize the risk of a power outage, inverter-based distributed-generation systems can help to support the grid by appropriately selecting the control objective. Which control strategy performs better when supporting the grid voltage is a complex decision that depends on many variables. This paper presents a control scheme that implements a smart and simple strategy to support the fault: the maximum voltage support for the lowest phase voltage. Therefore, the faulted phase that is more affected by the sag can be better supported since this phase voltage increases as much as possible, reducing the risk of undervoltage disconnection. The proposed controller has the following features: 1) maximizes the voltage in the lowest phase, 2) injects the maximum rated current of the inverter, and 3) balances the active and reactive power references to deal with resistive and inductive grids. The control proposal is validated by means of experimental results in a laboratory prototype.

Grasshopper optimization algorithm for automatic voltage regulator system

Abstract: A novel design method is presented to determine optimum proportional-integral-derivative (PID) controller parameters of an automatic voltage regulator (AVR) system utilizing the grasshopper optimization algorithm (GOA). The proposed approach is a simple and effective algorithm that is able to solve many optimization problems even those with unknown search spaces effectively. The simplicity of algorithm provides high quality tuning of optimal PID controller parameters. The integral of time weighted squared error (ITSE) is used as the performance index to confirm the performance of the proposed GOA-PID controller. When compared to the other PID controllers based on Ziegler- Nichols (ZN), differential evolution (DE), and artificial bee colony (ABC) tuning methods, the proposed method is found highly effective and robust to improve AVR system's transient response.

Voltage Management for Large Scale PV Integration into Weak Distribution Systems

Abstract: In long distribution feeders, step voltage regulators (SVRs) with the line drop compensation have been widely implemented to control voltage profiles. After integration of photovoltaic (PV) systems, reactive power support from PV inverters can also be utilized in voltage regulation. Although both SVR and reactive power support can be effective to manage system voltage without coordination, problems such as large voltage variations and excessive SVR tap operations still exist in some strong PV power fluctuating days. In order to solve these issues, SVR and reactive power support should be assigned to different voltage regulation tasks according to their voltage regulation characteristics. Specifically, in a distribution system, an SVR should mainly deal with slowly changing quantities ( e.g. , load, upstream voltage), while the limited reactive power support should be used to counter fast fluctuating PV power. In this paper, the power factor droop parameters applied on PV inverters are optimally selected to achieve such coordination, so that voltage problems and excessive SVR tap operations can be successfully mitigated. The effectiveness of the proposed method is demonstrated via case studies. Future PV integration project in weak distribution systems can benefit from the innovative and practical methodology proposed in this paper.

Active Power Quality Improvement Strategy for Grid-Connected Microgrid Based on Hierarchical Control

Abstract: When connected to a distorted grid utility, droop-controlled grid-connected microgrids (DCGC-MGs) exhibit low equivalent impedance. The harmonic and unbalanced voltage at the point of common coupling (PCC) deteriorates the power quality of the grid-connected current (GCC) of DCGC-MG. This paper proposes an active, unbalanced, and harmonic GCC suppression strategy based on hierarchical theory. The voltage error between the bus of the DCGC-MG and the grid’s PCC was transformed to the dq frame. On the basis of the grid, an additional compensator, which consists of multiple resonant voltage regulators, was then added to the original secondary control to generate the negative fundamental and unbalanced harmonic voltage reference. Proportional integral and multiple resonant controllers were adopted as voltage controller at the original primary level to improve the voltage tracking performance of the inverter. Consequently, the voltage difference between the PCC and the system bus decreased. In addition, we established a system model for parameter margin and stability analyses. Finally, the simulation and experiment results from a scaled-down laboratory prototype were presented to verify the validity of the proposed control strategy.

Voltage and Reactive Power Control to Maximize the Energy Savings in Power Distribution System With Wind Energy

Abstract: Commonly, voltage regulators and capacitor banks are used as control devices for voltage and reactive power (volt/VAr) control in distribution system. A specific mechanism can be developed using volt/VAr control for energy savings known as conservation voltage reduction (CVR). Active distribution system with high penetration of distribution generations (DG's) offers additional mechanism for volt/VAr control. The unique contribution of this paper is development of a computational algorithm for intelligent volt/VAr optimization and control of complex distribution networks with active participation from DG's to maximize overall network energy savings through CVR. Proposed volt/VAr optimization problem is solved to find the optimal voltage regulator settings, switched capacitor states, and voltage magnitude of DG controlled bus. This work presents a unique coordinated volt/VAr architecture that can find application in distribution management systems. Particle swarm optimization has been used given compatibility with combinatorial variables, robustness in solving nonlinear optimization problems, and ease of implementation. The results have been validated against an exhaustive search strategy for the IEEE 13 bus and IEEE 37 bus distribution system, and also using commercial distribution software SynerGEE. Results are also presented for a utility feeder with detailed analysis.

Incorporation of stochastic fractal search algorithm into efficient design of PID controller for an automatic voltage regulator system

Abstract: Although most accepted control algorithm is of proportional + integral + derivative (PID) structure in automatic voltage regulator (AVR) systems due to its effectiveness and simplicity, it is still a challenging task for researchers to tune its parameters efficiently. It is therefore of great interest, and constructs the motivation of this paper to undertake this task by incorporating the recently introduced, powerful optimization technique named as stochastic fractal search (SFS), for the first time in literature, which has the feature of increased accuracy and reduced convergence time. After optimizing the controller gains of Kp, Ki, and Kd, their performance is checked by using transient response analysis and then compared with those offered by recently published studies that use six competitive algorithms for achieving an efficient AVR system. To appraise the stability of the concerned power system tuned by SFS algorithm, root locus analysis and bode analysis are conducted along with the robustness analysis, which examines the system response to variations in the system parameters. Obtained comparative results affirm the excellence of SFS algorithm in achieving better PID parameters, and accordingly this yields an improved voltage response and minimized integral of time squared error in the output voltage profile.

Optimal Voltage Regulation of Distribution Networks With Cascaded Voltage Regulators in the Presence of High PV Penetration

Abstract: This work proposes a novel zone-based multistage “time-graded” operation of cascaded on-load tap changing transformers, capacitor banks, and step voltage regulators in the presence of large-scale photovoltaic (PV) sources. A multistage Volt-VAr optimization (VVO) algorithm is proposed to regulate the voltage in a medium voltage unbalanced distribution system while trying to relax the tap/switch operations of regulators that are cascaded in series, and minimize the curtailment of PV inverter output. A linearized power system model is formulated and a mixed-integer quadratic programming solver is utilized to solve the subobjective optimization at each stage in near to real time. The multistage coordinated operations are performed successively based on the regulator zones starting from the zone nearest to the substation, to achieve the overall voltage regulation of the system. Simulation studies were performed for various scenarios of PV and load profile variations. A comparison study between the novel multistage VVO and a multiobjective VVO was done to observe the convergence performance. Results show the efficient usage of the conventional voltage regulating devices along with minimal power curtailment from PVs when required.

Parallel Operation of Transformers With on Load Tap Changer and Photovoltaic Systems With Reactive Power Control

Abstract: In recent years, the number of active grid components for voltage regulation in distribution grids has increased significantly. Besides voltage regulators, such as transformers with on load tap changers (OLTCs), distributed generators can provide a certain voltage support by means of reactive power control (RPC). The different control entities, OLTC, and RPC by photovoltaic (PV) systems, usually operate based on local measurements and control characteristics. Hence, unintended interactions between the control entities cannot be excluded in general. This paper analyzes the parallel operation of OLTC transformers with a voltage-based control and PV systems with different RPC strategies (e.g., Watt/power factor control PF(P), volt/var control (Q(V)) in a distribution system environment. The focus is on unintended interactions, such as an increase of OLTC switching operations by PV RPC. The contribution and novelty of this paper is to raise awareness for the likelihood of these unintended interactions and to provide a first methodology to assess the parallel operation of OLTC control and PV RPC in detail. The results show that the impact of PV RPC on the number of OLTC switching operations and the effectiveness in parallel operation can differ considerably between the applied PV RPC strategies.

Static Voltage Security Region-Based Coordinated Voltage Control in Smart Distribution Grids

Abstract: The high penetration levels of distributed generators (DGs), on the one hand, make the operational state of distribution grids increasingly complex; on the other hand, they enrich voltage regulation measures. Consequently, a voltage control strategy of the distribution grid for coordinating DGs and other voltage regulation devices is needed. This paper applies the security region methodology to coordinated voltage control. To meet the demand of online voltage security assessment and control in the distribution grids, a hyperplane expression for the boundary of the static voltage security region (SVSR) in complex power injection spaces is derived, and a corresponding fast generation method is proposed. Additionally, based on SVSR, a two-stage voltage control strategy is proposed. In the first stage, the regulation devices are automatically selected according to the coefficients in the hyperplane expressions, and the regulation effect can be estimated by SVSR. In the second stage, the outputs of the devices are determined by utilizing an optimization technique. The proposed voltage control strategy is tested by using a modified PG&E69-bus distribution grid, and the results verify the effectiveness.

Combined voltage and frequency control of a multi-area multisource system incorporating dish-Stirling solar thermal and HVDC link

Abstract: This study highlights the significance of dish-Stirling solar thermal system (DSTS) and high voltage direct current (HVDC) link in the combined automatic load frequency control (ALFC) and automatic voltage regulator (AVR) model of the multi-area thermal-diesel plant. Appropriate generation rate constraints and governor dead band for the thermal plant are considered. A maiden attempt has been made to apply fractional order integral double derivative controller with derivative filter (FOIDDF) as a secondary controller for both ALFC and AVR loops. The performance of the FOIDDF controller is compared with some commonly used classical controllers. The lightning search algorithm is implemented for simultaneous optimisation of the controller parameters. The comparison shows the better performance of FOIDDF than others. The effect of the AVR loop on the ALFC loop is also analysed for the first time in the combined model. The investigation of the effect of DSTS and HVDC links reveals that their inclusion improves the system dynamics. The superiority of the proposed controller has been established for variable insolation of the DSTS. The rigorous sensitivity analysis of the different position and magnitude of disturbance, change in tie-line synchronising coefficient and different condition of the DSTS reflects the robustness of the proposed controller parameters obtained at the nominal condition.

Exploiting Voltage Regulators to Enhance Various Power Attack Countermeasures

Abstract: The security implications of on-chip voltage regulation on the effectiveness of various voltage/frequency scaling-based countermeasures such as random dynamic voltage and frequency scaling (RDVFS), random dynamic voltage scaling (RDVS), and aggressive voltage and frequency scaling (AVFS) are investigated. The side-channel leakage mechanisms of different on-chip voltage regulator topologies are mathematically analyzed and verified with circuit level simulations. Correlation coefficient between the input data and monitored power consumption of a cryptographic circuit is used as the security metric to compare the impact of different on-chip voltage regulators when implemented with the aforementioned countermeasures. As compared to a cryptographic circuit without countermeasure, the RDVFS technique implemented with an on-chip switched-capacitor voltage converter reduces the correlation coefficient over 80 percent and over 92 percent against differential and leakage power analysis attacks, respectively, through masking the leakage of the clock frequency and supply voltage information in the monitored power profile.

A Low-Cost Voltage Equalizer Based on Wireless Power Transfer and a Voltage Multiplier

Abstract: This paper develops a novel voltage equalizer by combining wireless power transfer (WPT) and a voltage multiplier (VM) for series-connected energy storage cells. The physical isolation achieved by WPT can offer several unique benefits that traditional equalizers can hardly provide. In this paper, the characteristics of a multiple-output VM are analytically discussed and used to develop an equivalent one-output VM model. Based on this model, parameters of the WPT system are properly designed. The proposed design methodology can achieve a single-switch voltage equalizer without feedback control, which dramatically decreases the circuit complexity and cost. Moreover, this methodology can naturally ensure a robust system under small coil misalignment. In the experiment, the proposed system is built to balance four series-connected ultracapacitor modules. The system efficiency is 72.8% at a load power level of 10 W.

A Transformer-Less Unified Power Quality Conditioner with Fast Dynamic Control

Abstract: A single-phase transformer-less unified power quality conditioner (TL-UPQC) is presented. Apart from having no isolation transformer, the proposed structure utilizes four switching devices only, forming two half-bridge voltage-source inverters—one connected in parallel with the load and another one connected in series with the ac mains. The two inverters share the same dc link. The parallel inverter, which is controlled by a hysteresis current controller, is used to shape the current drawn from the ac mains and regulate the dc-link voltage. The series inverter, which is controlled by a boundary controller with second-order switching surface, is used to regulate the steady-state load voltage and provide voltage sag/swell ride-through. A dc-link capacitor voltage balancing control that coordinates the operations of the hysteresis and boundary controllers is designed. Modeling, design, and analysis of the whole system will be given. A 1 kVA, 110 V, 60 Hz prototype has been built and evaluated on a setup with a nonlinear load. The steady-state and transient responses under a voltage sag will be given. Experimental results are favorably compared with the theoretical predictions and the performance of other UPQCs.

Reducing Power Side-Channel Information Leakage of AES Engines Using Fully Integrated Inductive Voltage Regulator

Abstract: This paper demonstrates an integrated inductive voltage regulator (IVR) for improving power side-channel-attack (PSCA) resistance of 128-bit Advanced Encryption Standard (AES-128) engines. An inductive IVR is shown to transform the current signatures generated by an encryption engine. Furthermore, an all-digital circuit block, referred to as the loop-randomizer, is introduced to randomize the IVR transformations. A 130-nm test-chip with an inductive IVR with 11.6-nH inductance, 3.2-nF capacitance, and 125-MHz switching frequency is used to drive two different architectures of AES-128 engine: high performance and low power. The measurements demonstrate that the IVR with loop randomizer eliminates information leakage while incurring only 3% overhead in performance and 5% overhead in power over a baseline IVR-AES system. Moreover, while a key-byte can be extracted for the standalone high-performance and low-power AES (LP-AES) with only 5000 and 1000 measurements, respectively, the proposed IVR inhibits key extraction even with 500 000 measurements.

Voltage Regulation Method for Voltage Drop Compensation and Unbalance Reduction in Bipolar Low-Voltage DC Distribution System

Abstract: Owing to the development of highly efficient electric power converters, the number of studies on the construction of low-voltage dc (LVDC) systems is gradually increasing. To use LVDC distribution systems, voltage regulation methods to compensate for the voltage drop and to limit the voltage unbalance are essential. In a bipolar LVDC distribution system, a voltage drop and voltage unbalance could occur because of the load current and the variation in the amount of power supplied to the poles. However, not enough research has been conducted on voltage regulation methods for LVDC distribution systems. To reduce the voltage drop and the voltage unbalance, this paper proposes a voltage regulation method based on the neutral to line drop compensation (NLDC) method, which employs a modified LDC to calculate the sending-end reference voltage. In the NLDC method, the neutral current and neutral line impedance are taken into consideration to compensate for the neutral line potential fluctuation and voltage drop on the pole. The next sending-end voltage is determined by checking the voltage unbalance factor, and it is adjusted to maintain it within the allowable voltage unbalance factor. A voltage regulation algorithm and a bipolar LVDC system model are implemented using the Electromagnetic Transients Program.