A novel high-speed flywheel based DC voltage source with soft handover capability

In the past large Uninterruptible Power Supply (UPS) applications requiring parallel operation of Pulse Width Modulated (PWM) inverters was not practical. New developments in PWM logic design have made load sharing of PWM inverters very precise. This paper addresses the critical factors of the inverter and system design which permit parallel operation and enhancement of system reliability. Taking full advantage of the PWM technique in control of an inverter is discussed. New methods of accomplishing parallel operation are discussed. Particular emphasis is given to improving the "fault tolerance" capabilities of a UPS system. The paper discusses in detail the design of a parallel-redundant UPS system which eliminates some of the "single point failure modes" present in most UPS system configurations. The logic design which permits precision sharing of load currents between parallel inverter; and, the methods of removing faulted inverters from the common bus are presented. Actual operating sequences are used to demonstrate the effectiveness of the system design and the improved fault tolerance characteristics.

This paper reviews the use of large DC aluminum electrolytic and AC polymeric film capacitors within Uninterruptible Power Supply (UPS) applications, focusing on aspects such as field aging, failure mechanisms, anticipated service life, and preventative maintenance of capacitors. UPS systems are equipped with substantial capacitor banks comprising both DC electrolytic and AC polymeric film capacitors. Both types of capacitors undergo degradation under real-world operating conditions, with field aging being a gradual process that can span several years. The review highlights that implementing a proactive replacement plan for AC polymeric film and DC aluminum electrolytic capacitors can significantly improve the reliability and performance of UPS systems and extend their service life. This approach successfully helps organizations prevent downtime and enhance power supply stability, leading to greater operational efficiency.

A current sharing method considering battery state of charge(SOC) for multi-module uninterruptable power supply(UPS) system is proposed. Modularized UPS system consists of a single master module and multi slave modules. A master module performs output voltage control and distributes current commands to slave modules. The current commands are generated by using the proposed current sharing algorithm to balance the SOC of each UPS module. Moreover, the UPS mode transfer time can be significantly reduced by using the predictive current control. The predictive current control method is mathematically verified by analyzing the UPS system. The validity of proposed balancing method and predictive control is verified by simulation results.

In this paper a Low frequency inverter, its operation and testing's are discussed. The low frequency inverter is designed for Uninterrupted Power Supply (UPS) application. This inverter is tested for improving the reliability to be well used in UPS application. The types of testing's and two case studies on improving the stability and reliability are discussed. Also the various protections included in UPS application for an inverter are discussed.

Objetive: Display console is the software and hardware platform of warship and submarine control system. It's very important to strengthen the performance and improve the life of the Uninterruptible power supply (UPS) in display console . The residual capacity of UPS is a nonlinear function of voltage, discharge current, temperature and other variables. At present, there are some problems such as large measurement error and poor state prediction, what influence the battery power management system's management effectiveness. Therefore, this paper studies the estimation method of battery residual capacity based on BP Algorithm according to the principle of neural network, so as to improve the estimation accuracy of UPS residual capacity. Method: Firstly, we establish the BP neural network model consists of three layers, secondly gather UPS experimental data set, then build, train and test BP network model with LM algorithm by Matlab program language, finally gather the state of charge(SOC) training results. Result: Experimental results indicate that the method in this paper can estimate UPS SOC accurately and efficiently. Conclusion: It can satisfy the system requirements of uninterruptible power supply SOC estimation.

The performance characteristics of the rectangular wave delta modulation (RWDM) scheme for uninterruptible power supply (UPS) applications is investigated. Normalized characteristic curves that show the effect of various modulator parameters on the frequency spectrum of the inverter output voltage are obtained using discrete Fourier transform (DFT) and harmonic analysis techniques. The performance of a single-phase half-bridge inverter with an LC filter is discussed, and experimental results are provided to validate the predicted and simulated results. It is shown that the harmonic content of the inverter output waveform can be controlled through the control of the modulator parameters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A division-summation (D-Σ) digital control can track sinusoidal reference current in four operation modes: grid-connection, rectification, PF leading and PF lagging mode. It can overcome the limitation of abc to α-β-γ frame transformation and cover wide filter inductance variation. However, the switching sequences for the four modes are different from each other, increasing complexity of firmware programming. In this paper, improvement of control-law derivation for D-Σ digital controlled three-phase four-wire inverter is presented. By selecting the zero crossing points of phase voltages as region transitions, the control laws and the related parameter tables for the four modes can be unified to a general form. The three-phase four-wire inverter topology can be also adopted as an uninterruptible power supply (UPS) application and it can supply unbalanced, linear and rectified loads. With the proposed load impendence estimation, the D-Σ digital control laws can be applied for voltage tracking. The switching sequences of the four modes and UPS mode are all unified to the switching pattern of the grid-connection mode. Additionally, a D-Σ transformation matrix is identified to simplify the derivation procedure of the division (D) and summation (Σ), which can obtain the control law directly. Experimental results measured from a 10 kVA inverter have verified the analysis and discussion.

Proton Motor in German deal for hydrogen fuel cell UPS

Three-phase Uninterrupted Power Supply (UPS) is widely used in industrial field. The output voltage quality of three-phase UPS mainly depends on its control strategy. However, the internal uncertainty and external disturbance of three-phase UPS always affect the output of UPS. Aiming at describing the source of internal uncertainty, the influence of external disturbance and system coupling of three-phase UPS, the detailed mathematical model is firstly established. Secondly, according to the mathematical model, the designing method for three-phase UPS controller based on active-disturbance rejection controller (ADRC) method is proposed. Finally, the corresponding simulation model is constructed in Matlab/Simulink. The simulation results prove that the proposed strategy can effectively improve the output power quality of three-phase UPS.

A multi-objective control scheme of a voltage source converter with battery–supercapacitor energy storage system used for power quality improvement

Uninterruptible power supply (UPS) monitoring system using message queuing telemetry transport (MQTT) protocol is a solution to solve UPS monitoring issues in a large infrastructure. This paper discusses the proof of the small size of message data by using the MQTT protocol on IoT-based communications. Based on IoT concept, the system described in this paper used Arduino microcontroller connected to the Internet via an Ethernet shield. The system used MQTT as a communication protocol that was designed for a lightweight communication. This system was intended to display UPS monitoring data in real-time on a web page stored on raspberry pi which roles as a web server, MQTT broker, MQTT subscriber and database. UPS parameter could be monitored using a web-based application. There were some differences in data obtained from sensor with the measurement results of measuring instruments specified for each parameter: the difference of input voltage was equal to 0.20%, while differences of output voltage, output power and output current reached 1.34%, 0.17% and 20%, respectively.

Problem: The current study was motivated by the need to identify and explore the mechanisms leading to performance degradation and the ultimate failure of a newly designed battery to be used as a backup source for uninterruptible power supplies (UPS) applications. It was also desired to estimate how long (in terms of number of discharge cycles) the battery could serve its intended function before failing to sustain a discharge cycle for the required duration during a power outage.Approach: An accelerated test (AT) was undertaken to investigate battery performance and degradation under elevated power, temperature, and cycling rate. The AT resulted in both lifetime and degradation data on test batteries. Standard maximum likelihood methods for censored data were used for lifetime analysis and modeling. In addition, a nonlinear mixed-effects model was developed to study the effects of acceleration variables on degradation.Results: The lifetime-data analysis of the data from the AT provided good life estimates because the resulting data involved little censoring. Nevertheless, the further careful study of the degradation data provided valuable added knowledge by suggesting some underlying physical mechanisms and yielding insights that helped product-reliability improvement. It is generally recognized that degradation measurements provide more information than lifetime data. This holds particularly when there are only a few observed failures and the data are heavily censored. This case study illustrates another important benefit of degradation data even when lifetime data are nearly complete. Such data allow modeling of physical failure mechanisms more directly than lifetime data and, therefore, yields insights not possible through traditional lifetime analysis.

In this paper, a digital controller design procedure is presented for single-phase voltage-doubler boost rectifiers (VDBR). The model derivation of the single-phase VDBR is performed in the s-domain. After that the simplified equivalent z-domain models are derived. These z-domain models are utilized to design the input current and the output dc-link voltage controllers. For the controller design in the z-domain, the traditional K-factor method is modified by considering the nature of the digital controller. The frequency pre-warping and anti-windup techniques are adapted for the controller design. By using the proposed method, the phase margin and the control bandwidth are accurately achieved as required by controller designers in a practical frequency range. The proposed method is applied to a 2.5 kVA single-phase VDBR for Uninterruptible Power Supply (UPS) applications. From the simulation and the experimental results, the effectiveness of the proposed design method has been verified.

This paper focuses on the development and experimental validation of a single-phase modular multilevel converter (MMC) based on a battery energy storage system (BESS) for residential uninterruptible power supply (UPS) with two-level active SoC balancing control. The configuration and mathematical modeling of the single-phase MMC-BESS are first presented, followed by the details of the control strategies, including dual-loop output voltage and current control in islanded mode, grid-connected control, circulating current control, and two-level active state-of-charge (SoC) balancing control. The design and optimization of the quasi-proportional-resonant (QPR) controllers were investigated by using particle swarm optimization (PSO). Simulation models were built to explore the operating characteristics of the UPS under islanded mode with an RL load and grid-connected mode and assess the control performance. A 500 W experimental prototype was developed and is herein presented, including results under different operating conditions of the MMC-BESS. The experimental results show that for both RL load and grid-connected tests, balancing was achieved. The response time to track the reference value was two grid periods (0.04 s). In the islanded mode test, the THD was 1.37% and 4.59% for the voltage and current, respectively, while in the grid-connected mode test, these values were 1.72% and 4.24% for voltage and current, respectively.

In this paper, we analyze lifetime maximization problem of lead-acid batteries commonly used in small scale Uninterrupted Power Supply (UPS) and distributed renewable energy systems. The aging process of batteries in these systems is a complex phenomenon and depends upon many factors. We consider the most comprehensive lead-acid battery model that is commonly known as the weighted Ah-throughput (Schiffer) model and identify three key factors affecting the lifetime of these batteries: 1) bad recharge, 2) time since last full recharge and 3) the lowest state of charge since last full recharge. Each factor depends on battery state of charge (SoC). An appropriate weighted sum of these three factors dictating the battery life is considered as optimization objective. The appropriate constrained optimization problems for the two common scenarios are solved and SoC-based charge/discharge algorithms are formulated. Simulation results show significant improvement in the lifetime of lead-acid battery (more than 85% in some cases) as compared to the traditional terminal voltage based charge control algorithms.