Single-phase Power Research Articles

PLC/HMI Based Portable Workbench for PLC and Digital Logic Learning and Application Development

A Programmable logic controller (PLC) uses the digital logic circuits and their operating concepts in its hardware structure and its programming instructions and algorithms. Therefore, the deep understanding of these two items is staple for the development of control applications using the PLC. This target is only possible through the practical sensing of the various components or instructions of these two items and their applications. In this work, a user-friendly and re-configurable ladder, digital logic learning and application development design and testing platform has been designed and implemented using a Programmable Logic Controller (PLC), Human Machine Interface panel (HMI), four magnetic contactors, one Single-phase power line controller and one Variable Frequency Drive (VFD) unit. The PLC role is to implement the ladder and digital logic functions. The HMI role is to establish the virtual circuit wiring and also to drive and monitor the developed application in real time mode of application. The magnetic contactors are to play the role of industrial field actuators or to link the developed application control circuit to another field actuator like three phase induction motor. The Single -phase power line controller is to support an application like that of the soft starter. The VFD is to support induction motor driven applications like that of cut-to-length process in which steel coils are uncoiled and passed through cutting blade to be cut into required lengths. The proposed platform has been tested through the development of 14 application examples. The test results proved the validity of the proposed platform.

State-of-the-Art Power Factor Correction: An Industry Perspective

On 1 January 2001, the IEC 61000-3-2 regulation became effective. Since then, mitigating current harmonics has been essential to ensure that electronic equipment connected to single-phase power distribution lines conforms to electromagnetic compatibility directives. Today, high-quality rectification, commonly known as power factor correction (PFC), is a well-established technique widely adopted by the industry for powering various devices from the ac line. The topic has been studied by academia and industry since the mid-1980s; thus, an enormous amount of research has been published and countless solutions have been proposed since then. However, only a few of those solutions have encountered wide industrial usage. So, it is not the authors’ intention to provide a comprehensive review, but to take stock of the most used PFC techniques from an industry perspective. This paper will review the power factor theory with non-sinusoidal currents, the practical and regulatory aspects of using PFC, and the most common industry solutions for power factor correction in equipment operated from the single-phase, public, low-voltage supply system, with a special focus on boost PFC pre-regulators, their control methods, design procedures, and issues.

Single-phase online interactive uninterruptible power supply design

The single-phase on-line interactive uninterruptible power supply (UPS) designed in this paper consists of three circuits, namely, a single-phase power factor correction circuit, a single-phase inverter circuit, and a bi-directional DC/DC circuit, each of which contains a main circuit as well as a control circuit. The principle, parameter design and control circuit design of each circuit are briefly described. The simulation model of the UPS is constructed, and the simulation results in normal and abnormal utility power are given to verify the correctness of the design.

Double-Loop Controller Design of a Single-Phase 3-Level Power Factor Correction Converter

This paper presents a study on the double-loop controller design technique for a single-phase power factor correction (PFC) three-level (TL) boost converter. Designing a double-loop controller using conventional methods is challenging due to the 120 Hz voltage ripple in the output voltage. This study proposes new double-loop control design methods using a band-stop filter and MATLAB SISOTOOL, detailed in a step-by-step sequence. A band-stop filter with a 120 Hz stop band is applied to the double-loop controller design. Modeling based on the state-space equation, applicable to the full duty range, is constructed to obtain the transfer function. The double-loop controller structure is then designed, and optimal gains that satisfy the design requirements are obtained through automatic tuning using the MATLAB SISOTOOL library. The simulation results demonstrate the performance of the proposed method, which is further verified by experimental results.

Overview of Open-Loop Frequency Estimation Techniques for Grid Synchronization of Single-Phase Power Converters

Open-loop synchronization techniques allow to overcome the stability issues to which closed-loop techniques are subject. Most open-loop techniques differ in their Quadratic Signal Generator and their frequency estimation method. In this paper, an overview of the main frequency estimation methods for single-phase power systems is presented. A description of each technique with their structure for numerical implementation is carried out. A comparative study of those frequency estimation methods is performed according to three test scenarios in order to evaluate the robustness of each method. Recommendations for the selection of the technique is given according to the simulation results.

Ambient Signals based Load Modeling with Two Three-phase Induction Motors

Abstract The traditional electric power system simulation and calculation are based on the simple load model including one motor and one static load. On the one hand, the power system load is getting more and more complex. On the other hand, it’s proved that two kinds of three-phase induction motors will show a little difference. As a result, in this paper, a new model load with two three-phase induction motors is proposed. Besides, the dynamic of the power system load is taken into account. The torque of those two three-phase motors will show different characteristics, that one is constant and the other is variable. Formerly, the dynamic of the load is regarded as the result of an induction motor. However, the single-phase motor and electronic load both lead to the complexity of the load. To get a more accurate calculation, we need a more proper load model. One of the ways to improve the load model is to pay more attention to the ingredients ignored. The single-phase motor and power electronic load make a great difference. Besides, it’s proved that the composited load model with two three-phase motors will be better in the calculation.

Development of an Automatic Phase Selector for Nigerian Power Utility Customers

Power utility customers in a developing country like Nigeria have constituted a habit of changing the electricity supply line from an unavailable or unstable phase to the most available or stable phase. The category of customers involved in this character are those on single phase power supply. However, this act is being carried out manually at the meter point using the cut-out fuses. This attitude results in phase unbalances, overheating electrical equipment including feeder pillars, transformer coils, network faults, and overall system instability. Thus, this paper presents the development of an Automatic Phase Selector for Nigerian Power Utility Customers. The device automatically selects an available phase from the three-phase power supply lines. The research comprises designing an automatic phase selector circuit, simulation of the designed circuit, programming code development in C- Language for the microcontroller, construction of the designed circuit, and carrying out tests on completed work done to ascertain the effectiveness of the developed system. The system operation involved a three-phase supply from the closest distribution network of the power utility company which is connected to a three-in-one gang switch while the switching ON and OFF of their static switches represent phase-off in an ideal situation. The operational results of this system are presented in the form of the truth table which indicates that the affected customer would not have a power supply only when the 3-phases are under voltage or overvoltage or unavailable. This implies that one of the three phases that meet the three criteria would be switched ON. A pure sine wave was used as input into the Optocoupler and the output waveform of the rectified pulsating signal is separately displayed. This output waveform is very clean and noiseless. Finally, the system when practically tested with an unbalanced three-phase supply, worked perfectly enhancing the flexibility of operating an Automatic Phase selector and hence avoiding manual switching of the phase selector which has been attributed to changing of cut-out fuses and associated stress as well as having a user-friendly phase selector.

Robust Voltage Control of a Single-Phase UPS Inverter Utilizing LMI-Based Optimization with All-Pass Filter Under System Uncertainty

This paper proposes a systematic control design for a single-phase LC-filtered inverter considering uncertain system parameters. One major difficulty in controlling single-phase power converters is the lack of a direct conversion method for transforming single-phase signals into dq-frame signals. By employing an all-pass filter in this proposed approach, it is possible to control the output voltage in terms of DC quantity or the dq-rotating frame. Furthermore, voltage stability and harmonic distortion (THD) minimization of the uninterruptible power supply (UPS) are major concerns in inverter design. Therefore, this controller uses integral action to get rid of steady-state errors and stabilize the closed-loop system by the state feedback control. In order to enlarge and guarantee the stability range in the presence of potential parameter fluctuations, an uncertainty model is being considered. In this context, the uncertainty models refer to the potential model with variations in the filter's inductance and capacitance caused by operating temperature, aging, and various external factors. The efficacy of the control approach is assessed through simulations and experiments, with the objective of comparing its results with those of the PI control using a control board featuring a TMS320F28335 digital signal processor. Consequently, the proposed approach offers lower THD at every load step with lesser afford in performance tuning in comparison to the PI method.

Fast bus voltage detection method for single-phase power converters with split capacitors based on reduced-order generalized integrals

Fast bus voltage detection method for single-phase power converters with split capacitors based on reduced-order generalized integrals

Cooling power analysis of a small scale 4 K pulse tube cryocooler driven by an oil-free low input power Helium compressor

Here we report the performance of a small scale 4 K pulse tube cryocooler operating with a low input power reaching a minimum temperature of 2.2 K, as well as a cooling capacity of over 240 mW at 4.2 K. The compressor is air cooled and can be supplied by single phase power sockets. With an input power of about 1.3 kW the coefficient of performance reaches values of up to 185 mW/kW, which is among the highest currently reported values for small to medium power pulse tubes. The combination of an oil-free Helium compressor and low maintenance pulse tube cryocooler provides a unique miniaturized, energy efficient and mobile cooling tool for applications at 4 K and below.

Modified Perturb and Observe-based MPPT control of MHPCS for single-phase power distribution positioned in remote locations

Modified Perturb and Observe-based MPPT control of MHPCS for single-phase power distribution positioned in remote locations

TS fuzzy control of PV assisted single phase three phase induction motor drive for rural pumping applications

The motor drives for aqua farms and large-scale irrigation system needs a reliable electric drive, which requires the continuous power supply and efficient control. However, the rural single phase power supply is frequently interrupted. Renewable assistance would improve the availability of supply and heuristic control approach improves robustness in control. This paper presents a three phase induction motor drive fed from single phase electric grid with assistance from PV and battery energy storage. TS- fuzzy based direct torque control is employed for robust control during load changes, and the topology, component modelling, front-end converter control, PV interface DC–DC converter control, and inverter control are presented. MATLAB/Simulink is used to simulate the proposed drive system. The performance of the proposed system is validated using simulation data for both steady-state and transient states.

Experimental analysis of a modified scheme for supplying single-phase remote loads from micro-hydro based three-phase self-excited induction generator

Induction machine (IM) plays significant role in rural electrification, acting as a generator for small kilowatt to large megawatt applications. These IMs are therefore used for power generation, gaining a huge acceptance within the researchers because of its brushless system, robust design and cheap market rate. In off-grid operation, the induction generator (IG) also known as self-excited IG (SEIG), requires supply of external reactive power (RP) for building up its terminal voltage and satisfying the electrical load demand. A small kilowatt level renewable-driven three-phase SEIG is generally deployed for generating single-phase power in off-grid mode for remote areas. Generation of single-phase power and supplying the load from a three-phase SEIG in off-grid operation, results in the imbalance of the SEIG's stator current and phase voltage. In this regard, various capacitor-based excitation (CBE) schemes have been reported for supplying the required RP to the three-phase SEIG and generating single-phase power, while reducing the mentioned difficulties. The current paper emphasizes on the steady-state mathematical formulation of a proposed modified CBE scheme for generating single-phase power and supplying remote hilly load from a hydro-driven three-phase SEIG under the fixed speed of the generator. Further, a state-of-the-art experimental test-bench of the proposed scheme, where a hydro-driven three-phase SEIG supplying single-phase resistive-inductive (RL) load has been showcased with the same being simulated in the MATLAB environment. The result indicates that the proposed CBE scheme can effectively supply single-phase RL load of different power factors (p.f.), having promising voltage regulation with balanced SEIG operation.

Feasibility Study of Three-Phase Modular Converter for Dual-Purpose Application in DC and AC Microgrids

The modern concept of a universal converter is intended as a power converter suitable for application in both dc or ac grids using the same external connectors. This novel family was recently proposed to allow an easier integration of renewable energy sources and energy storage systems, interfacing with dc/ac grids and/or loads with a minimum redundancy of power switches and passive elements. This kind of solution and applications are expected to be a reality in the nearest decade, as ac and dc low voltage distribution networks will coexist. Nevertheless, the initial solutions proposed as universal converter were focused on ac single-phase power conversion systems. In this sense, this article proposes and describes a new member of the universal converter family suitable for dc to dc and dc to ac power conversion (both in three-phase three-wire and in three-phase four-wire). The proposed power topology is derived as a modular extension from the single buck-boost bidirectional cell. Its main operation modes (buck and boost) are discussed, and a pulse-width-modulation technique is developed to generate the corresponding switching patterns. The proposed solution is successfully validated in open-loop mode both in simulation and experimentally with a laboratory prototype. The measured efficiency of the power converter was above 97% in the dc to ac mode and around 99% in the dc to dc mode.

Study of Problem and Effect Mitigation Technique of Unbalance Capacitance in 500 kV Single Phase Transformers

This article presents the study of the effect of unbalanced stray capacitance in single-phase 500 kV power transformers and establishes the mitigation technique. The power transformers were operated in Wang Noi Substation for transmitting the electrical power. There are 3 units of single-phase power transformer. Previously, a transformer of phase B failed after being serviced for several years. Thus, the new power transformer was ordered instead of the failed one. However, once the new system had been operated, the hotspots at the surge arrester of tertiary winding (22 kV) were found and the unbalance of phase voltages was observed, resulting in overvoltage as a root cause of the problem. Once a thorough investigation was done, it was found that there was an effect of unbalanced stray capacitance between tertiary winding and ground core since the new power transformer has some different designs compared with the remaining. Hence, the mitigation technique was performed by adding the capacitor parallel to the tertiary winding until the voltage balance was achieved. Simulation with the PSCAD program was performed to determine the optimum value for additional capacitors, i.e., voltage balance, using an iterative method. In this article, the capacitors used for additional were capacitor voltage transformers, which have been installed. As a result of the troubleshooting, the voltage at the 22 kV bus was more balanced as well as not causing overvoltage, and the hotspots at the surge arrester of tertiary winding were not detected resulting in gaining the stability and reliability of using these transformers.

Power transformer fault diagnosis using dynamic multiscale graph modeling and M2SGCN network based on statistical fusion

Power equipment fault diagnostics hold significant importance for the stability of power grid systems. In pursuit of this objective, this paper proposes a fault diagnosis method that utilizes dynamic multiscale graph (DMG) modeling and the multiscale multi-stream GCN(M2SGCN) network, incorporating statistical fusion. Specifically, a novel DMG modeling method is proposed to derive visibility graph data and horizontal visibility graph data from vibration signals across multiple scales. Next, a comprehensive neural network architecture named M2SGCN is established to learn global and local features simultaneously, providing a more precise representation. Subsequently, a Dempster Shafer evidence theory statistical fusion technique combined with an adaptive threshold model (DSTFusion) is utilized to integrate primary decision results for enhanced fault diagnosis accuracy. In addition, two datasets obtained from single-phase and three-phase power transformers are analyzed to demonstrate the evolution process. When compared to state-of-the-art indicators such as accuracy, precision, recall, and F1 scores, the method proposed excels in multiple aspects, successfully detecting fault states before their occurrence and achieving outstanding performance.

Unit vector template controlled grid integrated and solar fed BLDC drive-based water pumping system

With increased population and energy demand, the need to utilize renewable energy becomes so vital. The need to manage food demand globally also emphasizes the support to agriculture. This article proposes a unit vector template-controlled grid-integrated solar Photovoltaic (PV) powered three-phase Brushless Direct Current (BLDC) drive-based water pumping system. The proposed system includes solar photovoltaic, boost converter, voltage source inverter, single phase grid supply, single phase bidirectional voltage source converter, and BLDC-driven water pump. The solar PV is connected to the dc grid through the boost converter. An incremental conductance algorithm performs the Maximum Power Point Tracking (MPPT) of a Photovoltaic array. The power exchange between the dc-bus and the utility grid has been achieved through a unit vector template algorithm-controlled bidirectional voltage source converter. It allows a consumer to operate a water pump at maximum capacity for the whole day regardless of the weather and to supply a single-phase power grid when water pumping is unnecessary. A 3-phase BLDC motor-based water pump is driven by a 3-phase voltage source inverter, which is used for electronic commutation and to regulate the motor speed. The performance of the proposed system has been evaluated for different modes of peak, rms voltage and motor speed has been maintained around 255 V and 180 V and 2500 rpm respectively in all the modes of operation. Its practicality and trustworthiness are shown by different simulation results using MATLAB/Simulink version 2022bsoftware.

D-estimation method for grid synchronization of single-phase power converters: analysis, linear modeling, tuning, and comparison with SOGI-PLL

D-estimation method for grid synchronization of single-phase power converters: analysis, linear modeling, tuning, and comparison with SOGI-PLL

A control method for the single-phase three-leg unified power quality conditioner without a phase-locked loop

The single-phase three-leg unified power quality conditioner (UPQC) can achieve the functions of voltage compensation, reactive power compensation, and harmonic compensation. However, traditional control algorithms require a phase-locked loop to obtain the real-time phase angle of the grid voltage, which undoubtedly increases algorithm complexity. To simplify the phase-locked calculation, this paper proposes a control method without the phase-locked loop for the single-phase three-leg UPQC. In the proposed scheme, the instantaneous value of the grid voltage is employed to realize the grid integration control. Then, the load voltage reference is calculated in real time using a second-order generalized integrator. Moreover, a simple algorithm for reactive power and harmonic compensation is discussed, further simplifying the control algorithm. Finally, a small-scale experimental platform is built, and the effectiveness of the proposed method is verified by the experimental results.

Proposal of Novel Single-Phase Power Quality Indicators considering subsynchronous frequency perturbations in Voltage and Current under non-sinusoidal conditions.

This work pretends to reconsider power quality (PQ), in AC single-phase low voltage systems, considering perturbation sources with frequency components below the fundamental frequency in voltage and current signals. These perturbations induced by sources like Geomagnetic Induced Currents (GMC), Arc Furnaces, switching VSC, etc. [1]-[2],[30]-[32], can occur in a frequency range comprised between DC and the fundamental frequency of the system. Standard PQ indexes do not characterize properly these subsynchronous frequency perturbations (SFFP), [2]-[3] and this work pretends to analyze the spectra from 0 to 50Hz for voltage and current, proposing new formulation for some PQ as a function of SSFP, with the intention of explaining the observed degradation of the power quality in single-phase low voltage electric systems.