Digital Control Strategy for Single-phase Voltage-Doubler Boost Rectifiers

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.

DC-DC converters are extensively used for switched mode power supplies. Hence, this chapter presents a design, modelling and hardware implementation of a digitally controlled system and its application to DC-DC buck converter being interfaced with Texas Instruments DSP TMS320F2812 controller for voltage control mode. ADC, compensator and digital PWM are the main building blocks that appears in digital controller design. Conventionally, analog controller is popular to get the desired output voltage in DC-DC converters, whereas, digital controllers offer high speed arithmetic and high resolution. Analog PI controller design approach is reviewed and the digital PI controller design is being implemented in this chapter. Digital control has been applied using standard frequency responses with design by emulation approach. Modulation delay in digital control is very critical while designing for fast control loops. Therefore, this chapter also introduces discrete time modelling of synchronous buck converter from practical standpoint considering feedback loop delays. Whereas, this chapter illustrates PI digital controller design methodology, hardware implementation and experimental verification. Experimental results have been taken from a closed loop 18W buck converter. The transient and steady state performance of the converter using PI controller are also presented with appropriate simulation and hardware results.

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.

As digital control may meet the increasingly rigorous requirements for power converters, more and more attention has been paid to the digitalization of traditional analog control uninterruptible power supply (UPS). However, time quantization and numerical quantization of discrete-time system result in a series of problems in digital control UPS, such as sampling delay, computational delay, serious dead time effect, and truncation error etc. In this paper, these issues are researched, and the corresponding techniques for designing a digital single-phase full-bridge on-line UPS are proposed. In digital UPS system, the flux imbalance of output transformer is induced by the accumulation of truncation error, and can be eliminated by modifying digital control algorithm with real time bias correction signals. Under the selection of optimal sampling mode, the sampling delay of control variables may be reduced apparently. The feed-forward compensation scheme is proposed to alleviate the dead time effect. By adjusting the frequency and phase of inverter output voltage alternately, the digital phase-locked loop is implemented in software. Theoretical analysis and experimental results are presented to demonstrate the validity and feasibility of these proposed control schemes.

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.

A novel high-speed flywheel-based DC voltage source (FDCS) has recently been developed as a direct and improved energy storage substitute for chemical batteries in uninterruptible power supply (UPS) applications. Like chemical batteries, the FDCS requires only a DC connection to a UPS with no other interconnections; however, the FDCS offers many advantages over chemical batteries, including reduced life cycle costs due to elimination of the periodic replacement of chemical batteries, increased power density, known state of charge, and the absence of environmentally harmful materials. The FDCS also incorporates a novel soft handover feature which was developed to provide a gradual load transfer from the backup energy source of the UPS to a backup engine-generator set (genset). In the absence of the soft handover feature, the genset fails due to its inability to slew its output power in the time required to continue to supply the critical load. This paper details the performance of the FDCS during operational events and shows the benefits of the soft handover feature for a combined genset-UPS ride-thru application

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>

Proton Motor in German deal for hydrogen fuel cell UPS

With the popularity of micro-processors, digital controllers are widely used in uninterruptible power supply (UPS) inverters. These digital control systems of UPS inverters require a time interval for sampling and computation, which sometimes affects the performance of inverters. In this paper, the problem of time delay in digital control of a UPS inverter is discussed. Then two novel pulsewidth modulation (PWM) methods, the two-polarity PWM method and the asymmetric PWM method, are proposed to handle the time-delay problem. Both of these PWM methods can achieve a wide range of duty ratio between 0.05-0.95, which is independent of inverter model. Furthermore, they are easy to implement using a digital micro-controller. Experimental results are presented in the paper to verify feasibility of the proposed PWM methods.

Uninterruptible Power Supply (UPS) is widely used in industry and electronics field in order to improve power quality. However, the distortion and interruption of output voltage will occur when UPS is applied to instantaneous impulsive load. This paper proposes a novel dynamic control strategy to resist impulsive load. When the impulsive load is imposed on UPS instantaneously, the impulsive current can be quickly sensed by the digital controller and the supplying power for the load is switched from inverter to bypass immediately. Therefore, the output voltage of UPS can be maintained uninterruptible. The proposed control strategy is verified by a 30 KVA UPS prototype.

Part 1 Computers in control systems: historical development digital computer interfacing structure of a digital control loop interface units data representation and aliasing. Part 2 The z-transformation: definition of the z-transform z-transform properties inverse z-transform pulse of z-transfer functions of systems discrete approximations numerical integration pole-zero mapping modified z-transform multi-rate sampling systems analysis of multi-rate systems fast-slow multi-rate systems closed-loop multi-rate systems. Part 3 Analysis of sampled-data control systems z-transformation of systems stability in discrete systems time domain analysis root locus analysis frequency domain analysis. Part 4 Digital compensator design: continuous domain design digital design digital root locas design state feedback design digital PID control disign deadbeat response design optimal control design controller design in the presence of noise. Part 5 Real-time computer control systems: hardware requirements the digital computer and peripheral equipment the real-time clock interface units software aspects controller implementation programming languages system design co-ordination sampling rate selection and quantization errors computer/device communications interrupt handling multi-tasking and background/foreground. Part 6 Advances in computer control: artificial intelligence expert systems examples of expert systems knowledge based systems in control engineering conventional controller design methods manual control methods fuzzy sets and rule-based control basic fuzzy operations fuzzy relations fuzzy control algorithms parallel processing techniques parallel computers algorithms for parallel (MIMD) computers programming parallel computers performance of parallel computers parallel processing in control engineering matrix algebra numerical integration fault tolerance. Appendices: Table of laplace and z-transforms continuous second-order systems response specifications frequency response characteristics the transputer and occam occam overview transputer systems and occam configuration vibration control of a flexible cantilever system simulation modelling and state estimation controller design user interface solutions.

A robust fuzzy digital PID control methodology based on gain and phase margins specifications is proposed. A mathematical formulation based on gain and phase margins specifications, the Takagi-Sugeno fuzzy model of the process to be controlled, the structure of the digital PID controller, and the time delay uncertain system are developed. A multiobjective genetic strategy is defined to tune the fuzzy digital PID controller parameters, so the gain and phase margins specified to the fuzzy control system are found. An analysis of necessary and sufficient conditions for fuzzy digital PID controller design with robust stability, with the proposal of the two theorems, is presented. Experimental results show the efficiency of the proposed methodology in this chapter, applying a platform control in real time of a thermic process through tracking the reference and the gain and phase margins keeping closed the specified ones.

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.

Multiobjective controller design handling human preferences