UPS Inverters Research Articles

Continuous switching sliding mode controller design for single-phase UPS inverter circuit

Continuous switching sliding mode controller design for single-phase UPS inverter circuit

Prototyping Power Electronics Systems with Zynq-Based Boards Using Matlab/Simulink—A Complete Methodology

Many advanced power electronics control techniques present a steep computational load, demanding advanced controllers, such as FPGAs. However, FPGA development is a daunting and time-consuming task, inaccessible to most users. This paper proposes a complete methodology for prototyping power electronics with Xilinx Zynq-based boards using Matlab/Simulink and HDL Coder. Even though these tools are relatively well documented, and several works in the literature have used them, a methodology for developing power electronics systems with them has never been proposed. This paper aims to address that, by proposing a complete programming and design methodology for Zynq-based power electronics and discussing important drawbacks and hurdles in Simulink/HDL Coder development, as well as their possible solutions. In addition, techniques for the implementation of all required peripherals (ADCs, digital outputs, etc.), system protections, and real-time data acquisition on Zynq boards are presented. This methodology considerably reduces the development time and effort of power electronics solutions using Zynq-based boards. In addition, a demonstration Simulink model is provided with all proposed techniques and protections, for use with a readily available development board (Zedboard) and ADC modules. This should further reduce the learning curve and development effort of this type of solution, contributing to a broader access to high-performance control prototyping using Zynq-based platforms. An application example is presented to demonstrate the potential of the proposed workflow, using a Zedboard to control a multilevel UPS inverter prototype with Model Predictive Control.

Manufacturing of Electrochemical Cell and Enhanced its Efficiency by Adding Additive in Electrolyte

The importance of a lead-acid battery in our daily life needs no explanation. Automotive batteries in their dominant part were made with hard rubber holders and heavy plates and the service life was two years. On the other hand, in stationary batteries, open Planet style cells were still being used and got an additional arrangement of positive plates once the primary set was exhausted. The world has improved significantly from that point forward, both in structure and innovation. Still, the lead-corrosive battery for rechargeable frameworks has not changed, despite there is no indication that it tends to be supplanted close to term by secondary battery framework. So, it is advantageous to take a gander at enhancements in the innovation of battery creation that have occurred essentially in the course of the most recent ten years. Thyristor innovation and micro-processor control take into account strategies that one could dream about in previous times. From a car battery to a UPS inverter, we daily need the services of a lead-acid battery. Considering these aspects, the current research is an effort to provide such solutions so, that the working life of the lead-acid battery increases by not increasing its manufacturing cost. It was found that the two added substances methane sulfonic acid (MSA) and aminomethyl sulfonic acid (AMSA) to lead-acid batteries can enhance the electro-chemical performance and thermal stability of which MSA shows the best impact.

Reinforcement Q-Learning Algorithm for H∞ Tracking Control of Unknown Discrete-Time Linear Systems

This article addresses the online reinforcement $Q$ -learning algorithms to design $H_{\infty }$ tracking controller for unknown discrete-time linear systems. An augmented system composed of the original system and the command generator is constructed, and a discounted performance function is introduced to establish a discounted game algebraic Riccati equation (GARE). The existence conditions of a solution to the GARE are proposed and a lower bound is found for the discount factor to assure the stability of the $H_{\infty }$ tracking control solution. The $Q$ -function Bellman equation is then derived, based on which the reinforcement $Q$ -learning algorithm is developed to learn the solution to $H_{\infty }$ tracking control problem without knowing the system dynamics. Both state-data-driven and output-data-driven reinforcement $Q$ -learning algorithms toward finding the control policies are proposed. Unlike the value function approximation (VFA)-based approach, it is proved that the $Q$ -learning scheme brings out no bias of solution to the $Q$ -function Bellman equation under the probing noise satisfying the persistent excitation (PE) condition, and therefore, converges to the nominal discounted GARE solution. Moreover, the proposed output-data-driven method is more powerful than the state-data-driven method as it may not be available to completely measure the full system states in practical applications. A simulation example with a single-phase voltage-source UPS inverter is used to verify the effectiveness of the proposed $Q$ -learning algorithms.

Proportional Integral Control Realized in Stationary and Synchronous Reference Frames for a Single-Phase UPS Inverter System: A Comparative Study

ABSTRACTVoltage regulation of the single-phase UPS inverter has design challenges in terms of dynamic performances and control complexity. Widely used conventional integral controllers, such as proportional integral and proportional resonant in stationary frame (SF) of reference have limitations of either steady state error or implementation difficulties. Although a mature technique in three-phase applications, the synchronous reference frame (SRF) control scheme has not been exhaustively investigated for single-phase UPS inverters due to complex multiple transformations. This paper suggests a voltage control scheme which can be alternatively used in both stationary and synchronous reference frames. Three integral controllers namely, SF-proportional integral (SF-PI), SF-proportional resonant (SF-PR) and SRF-proportional integral (SRF-PI) are comparatively evaluated for steady state and transient performances. A systematic procedure for the design of control parameters with stability analysis in the frequency domain for the closed loop control system is also presented. Respective controllers are simulated in discrete time frame using MATLAB/Simulink and experimentally implemented using the TMS320F2812 Digital Signal Processor based laboratory prototype.

A new approach to design an observer for load current of UPS based on Fourier series theory in model predictive control system

In this paper, the model predictive control (MPC) system based on the state space is designed to generate the appropriate switching pulses for UPS inverters. The fast dynamic response and the capability in assessment of various cost functions are some advantages of the predictive control system. The equations concerning the control system show that the load current should be measured. To eliminate the required sensor for load current measurement a new observer is proposed, so the amount of cost can be reduced and the reliability of the system also enhanced. Ordinary observers like Luenberger in terms of stability and design encounter several difficulties. The proposed observer is developed based on Fourier series and instantaneous power theories. This observer is doing well in estimating the load current and renders superior performance regarding the dynamic behavior, stability and convergence. Furthermore, in this observer there is no need for any parameters adjustment and the load current is accurately observed using the measured output voltage and the filter current. To examine the operation of the system the necessary simulations and laboratory experimental results are provided on a 3-phase 220 V UPS. The obtained results are then compared to those obtained by the Luenberger observer.

A digital dual-modulation control for single-phase UPS inverters

ABSTRACTA trip-point modulation strategy is proposed for single-phase uninterruptible power supply inverters with an LC filter, which operates simultaneously with pulse-width modulation, named dual-modulation (DM) control. Current estimation and offset current approximation are used conjointly to facilitate the proposed control law. It is shown analytically that the DM control leads to reduced total harmonic distortion (THD) and gains fast transient-state recovery. The simulation and experimental results demonstrate significant amelioration to THD and dynamic state compared to proportional–integral–derivative control under both linear and non-linear loads.

Hierarchical Fuzzy Control Applied to Parallel Connected UPS Inverters Using Average Current Sharing Scheme

Parallel connection of UPS inverters to enhance power rating is a widely accepted practice. Inter-modular circulating currents appear when multiple inverter modules are connected in parallel to supply variable critical load. Interfacing of modules henceforth requires an intensive design, using proper control strategy. The potentiality of human intuitive Fuzzy Logic (FL) control with imprecise system model is well known and thus can be utilised in parallel-connected UPS systems. Conventional FL controller is computational intensive, especially with higher number of input variables. This paper proposes application of Hierarchical-Fuzzy Logic control for parallel connected Multi-modular inverters system for reduced computational burden on the processor for a given switching frequency. Simulated results in MATLAB environment and experimental verification using Texas TMS320F2812 DSP are included to demonstrate feasibility of the proposed control scheme.

저항성 수하 제어를 적용한 3상 모듈형 UPS 인버터의 비통신선 방식 병렬 운전

저항성 수하 제어를 적용한 3상 모듈형 UPS 인버터의 비통신선 방식 병렬 운전

Study of Electrodeposited Zinc Morphology in Rechargeable Alkaline Batteries

Rechargeable zinc-nickel flow-assisted batteries are attractive in applications like frequency regulations, UPS inverters and hybrid electrical vehicles, etc[1] due to their advantages, such as, being cheap, capable of rapid charging and discharging and high energy density. However, the challenge that rechargeable zinc-anode batteries are facing is short lifespan time due to non-uniform morphology of zinc deposition during charging, hydrogen evolution that compromises energy efficiency and zinc corrosion during battery resting, which leads to further capacity loss[2]. We developed an indicator that monitors the transition of zinc morphology during battery charging[3]. Zincate concentration in the electrolyte, flow velocity and current density were varied over a wide range in the experiments. The results from SEM and 3D X-ray computer tomography (figure 1) show that the ratio between the effective current density and the limiting current density (current density ratio), which is directly related to the zincate concentration at the electrode surface, determines the zinc morphology. Furthermore, we investigated the causes of transition of zinc morphology. Compact zinc deposits are found to have a fine-grained, bright finish and the highest anodic efficiency (figure 2)[4]. Electrochemical impedance spectroscopy (EIS) proves that compact zinc corresponds to the minimum in the half-cell resistance, indicating it is kinetically preferred for compact zinc to form. Preferred crystal orientations of compact zinc depositions make good agreement with the EIS results. Anode substrate is a parameter that also influences the zinc morphology. We studied the effects of various novel metal substrates on zinc morphology over battery cycling. Results from electrochemical techniques, chemical characterization and cell cycling showed that Cu and Bi are promising anode substrates. In order to alleviate the corrosion rate and increase the lifespan of zinc-anode batteries, we investigated the impacts of additives on zinc morphology and cell performance. Lab-scale cells have demonstrated more than 2000 cycles and large-scale cells (113Ah) have demonstrated more than 200 cycles (figure 4 and figure 5). The results indicate that the morphologies of zinc deposition with the presence of additives are finer and the battery performance is improved as well.

Problems and Prospects of Battery Dealers

The industrial batteries consumption is going up every year with the economy booming. This in turn will create more opportunities and demand for the batteries in the sectors such as telecom towers, railway usage, automobiles, power sector and household for UPS inverters. With the country short of power in several pockets, usage of inverters too, has gone up significantly, and this is not going to come down in the near future. Hence, studying about the battery dealers' opinion on problems and prospects of battery business in the study area is quite significant as it will expose the difficulties confronted by them and scope for the prospects of their business. For the purpose of the study both primary and secondary data were employed. Convenience sampling method was adopted to collect the primary data from 200 battery dealers of various brands from the three districts namely Coimbatore, Erode and Tirupur. Field survey method was employed to collect first hand information through a well-structured questionnaire. Secondary data was also collected for the study from books, journals and news papers. It is clear from the study that the present battery dealership business performance is good. However, companies have to create certain policies which reduce the stringent formalities in the business to encourage the dealers and promote the business.

Particle swarm optimization tuned fuzzy terminal sliding mode control for UPS inverters

This paper proposes a particle swarm optimization algorithm tuned fuzzy terminal sliding mode control for the appli- cation of UPS inverters. Though classic sliding mode control (SMC) is insensitive to system uncertainties, it possesses an infinite system-state convergence time. For high-accuracy tracking control, a terminal sliding mode control (TSMC) is developed to provide a finite system-state convergence time. However, difficult estimation occurs in TSMC, and incurs high UPS inverter voltage harmonics and slow dynamic response. To obtain high-quality UPS inverter output voltage, a fuzzy logic (FL) with a computationally simple and practically easy estimator is integrated into TSMC to resolve system uncertainties. Simultaneously, the particle swarm optimization (PSO) algorithm is applied to optimally tune the control gains of the TSMC with a fuzzy estimator. Results indicate that the presented combination of PSO, FL and TSMC yields a closed-loop UPS inverter with good performance under various loading conditions. Simulation and experimental results indicate that the proposed control can achieve low total harmonic distortion (THD) under nonlinear loading conditions and fast dynamic response under transient loading conditions.

An Extended Lyapunov-Function-Based Control Strategy for Single-Phase UPS Inverters

In this study, an extended Lyapunov-function-based control strategy that assures global asymptotic stability is proposed for single-phase UPS inverters. The Lyapunov function is formed from the energy stored in the inductor and capacitor due to the fact that the system states converge to the equilibrium point if the total energy is continuously dissipated. It is shown analytically that the classical Lyapunov-function-based control leads to a globally asymptotically stable system at the expense of steady-state errors in the output voltage, which exist due to the lack of outer voltage loop in the control input. Therefore, an extended Lyapunov-function-based control strategy is proposed, which eliminates the steady-state error without destroying the global stability of the closed-loop system. The steady state and dynamic performance of the proposed control strategy has been tested by simulations and experiments under resistive and diode bridge rectifier loads. The results obtained from a 1-kW inverter demonstrate that the developed control strategy not only offers global stability, but also leads to good quality sinusoidal voltage with a reasonably low THD, almost zero steady-state error in the output voltage, and fast dynamic response under linear and nonlinear loads.

An adaptive sliding-mode control technique for three-phase UPS system with auto-tuning of switching gain

This paper presents an adaptive sliding-mode control (ASMC) technique for a three-phase UPS system with an auto-tuning mechanism of the switching gain. First, a sliding-mode control (SMC) scheme for the three-phase UPS inverter is designed to guarantee the robustness against the system uncertainties and external disturbances. Then, through addition of an adaptive control term, the ASMC algorithm is developed to optimize the switching gain without the prior information of the unknown and bounded uncertainties. It is shown that the upper bounds of the uncertainties are not required to be known in the SMC design. Also, the chattering problem in the reaching mode is considerably alleviated and the excessive use of electric power can be reduced by avoiding overestimation of the switching gain. Both the stability and robustness of the proposed ASMC method are proven by using the Lyapunov theory. In addition, a simple sliding-mode observer is used to estimate the load current without any additional current sensors. Therefore, the proposed ASMC system can accomplish the superior control performance (such as faster voltage recovery under a sudden load change, smaller steady-state error under parameter deviations, and lower THD under nonlinear load) compared to the conventional SMC scheme. Finally, the performance verifications of the proposed algorithm are carried out through the comparative simulation and experimental results on a prototype 1-kVA three-phase UPS inverter using TMS320F28335 DSP.

Design and Stability Analysis of a Fuzzy Adaptive SMC System for Three-Phase UPS Inverter

This paper proposes a combined fuzzy adaptive sliding-mode voltage controller (FASVC) for a three-phase UPS inverter. The proposed FASVC encapsulates two control terms: a fuzzy adaptive compensation control term, which solves the problem of parameter uncertainties, and a sliding-mode feedback control term, which stabilizes the error dynamics of the system. To extract precise load current information, the proposed method uses a conventional load current observer instead of current sensors. In addition, the stability of the proposed control scheme is fully guaranteed by using the Lyapunov stability theory. It is shown that the proposed FASVC can attain excellent voltage regulation features such as a fast dynamic response, low total harmonic distortion (THD), and a small steady-state error under sudden load disturbances, nonlinear loads, and unbalanced loads in the existence of the parameter uncertainties. Finally, experimental results are obtained from a prototype 1 kVA three-phase UPS inverter system via a TMS320F28335 DSP. A comparison of these results with those obtained from a conventional sliding-mode controller (SMC) confirms the superior transient and steady-state performances of the proposed control technique.

Research of UPS Inverter Based on Repetitive Control and Deadbeat Control

A composite control strategy is proposed based on the repetitive control and deadbeat control in the ups inverter control system, according to the features of the non-static error track of repetitive control and the deadbeat control’s fast response and high precision control. Repetitive control can be very good to eliminate periodic disturbance, and deadbeat control to reduce the overshoot and oscillation, when the system is subject to greater disturbance, that can improve the dynamic performance of the system. Simulation results show that it has a fast transient response, high accuracy, THD and other small features.

Low-THD, Fast-Transient, and Cost-Effective Synchronous-Frame Repetitive Controller for Three-Phase UPS Inverters

This paper presents a novel synchronous-frame repetitive controller for three-phase UPS inverters. Distinguished from conventional repetitive control techniques, the proposed synchronous-frame approach minimizes the repetitive control time delay to one-sixth of the fundamental period such that the dynamic response is significantly improved. In order to overcome the harmonic distortions under severe load conditions (e.g., unbalanced and nonlinear), in this paper, three synchronous rotating frames are deliberately selected, in each of which the repetitive controller is incorporated. Resultantly, the (6n ±1)th harmonics as well as the triplen harmonics are compensated. Moreover, a high-performance fourth-order linear phase infinite-impulse-response filter is applied to further enhance the accuracy of steady-state tracking. The proposed controller is programmed on the 16-bit fixed-point digital signal processor (TI TMS320LF2407) and eliminates high-resolution current sensors for cost effectiveness. Simulations and experimental tests have been carried out based on an 18-kW three-phase UPS system. Low total harmonic distortion (<;0025;) has been achieved under heavily distorted nonlinear load and unbalanced load. Fast dynamic response has been demonstrated during step load transients.

A Bidirectional UPS Inverter Utilising High Frequency Center–Tapped Transformer

A new variation of transformer-isolated inverter for UPS application is proposed. It is basically similar to the circuit proposed by Kourtroulis with the following modifications: 1) a modified modulation technique for the HF PWM interver stage and 2) replacing the full bridge active rectifier witha center-tapped active rectifier. With these modifications, the switches count is reduced, and expectedly, the efficiency is increased. Futhermore, the modified PWM technique will ensure that the transformer can be utilised near to its full potential. This is due to be absence of the low frequency component that can result in transformer saturation. The paper will detail the design considerations for the proposed topology. It will primarily focus on the power circuit, modulation method, and the high frequency transformer design. To prove the concept, a 1–kW prototype inverter was built and tested. Keywords: Inverter, bidirectional, high frequency transformer, pulse width modulation

Comparative Study of Different Switching Surfaces for Sliding Mode Control of a 40 kVA Single-phase UPS Inverter

In this paper, the effect of switching surface on sliding mode control of a single phase inverter is studied. Capabilities of three switching surfaces in chattering elimination, THD reduction and steady state error improvement are compared. The performance of these switching surfaces has been investigated through simulation. Simulation results show that after chattering improvement by adding first integral term, adding second integral term is not advisable.

One-Cycle Controlled Single Phase UPS Inverter

Abstract A one-cycle controlled single-phase full-bridge DC-AC inverter is proposed. One-cycle control is a nonlinear control method which has fast transient response and good tracking performance. The one-cycle control immunizes the inverter against the perturbation of input dc bus and provides well system dynamic regulation with hybrid sinusoidal PWM control. The basic operational theory and control method are discussed in this paper. Finally, simulation waveforms and experimental results are given. The simulation and experimental results demonstrate the effectiveness of this control technique for inverters in UPS applications, especially when nonlinear loads must to be supplied and line has large undesirable harmonic components.