Output Voltage Control Loop Research Articles

Smart Home Powered by Solar: IoT-based SEPIC Converter Control

Background: In this article, an IOT solution for managing and controlling a PV system with applications for the home is presented. A DC-DC SEPIC converter, a bidirectional converter, a PWM generator, and a single-phase voltage source inverter with active clamping are used for power conditioning. An output voltage control loop is implemented, and real-time online communication with an internet server is accomplished using the PIC microcontroller. Methods: The ESP8266MOD WIFI IOT module works with the Blynk mobile app. Experimental findings showing the proper operation of IOT features demonstrate the effectiveness of voltage regulation. In this article, frequency is taken into consideration as solar power is integrated with the grid. A user may easily control the DC-DC converter, load batteries, and monitor battery voltage through our userfriendly GUI interface. Results: In this paper, an IOT (Internet of Things) application was used to control and track the output of a modest PV power plant. The study shows the efficiency of the digitally controlled system developed to regulate the output voltage of the SEPIC DC-DC converter. Practical Significance: They further argue that the ESP8266 and microcontroller's versatility make them an appropriate instrument for remote and real-time monitoring and control of the proposed model from around the world. The energy that is produced by the sun is added to the grid so that it may be put to effective use and contribute to satisfying the rising demand for energy. Solar energy is the input that SEPIC uses to charge the batteries and for all of its other processes. In the event that solar photovoltaic (PV) panels are not available, the SEPIC DC-DC converter will derive its energy from AC power. Conclusion: In this article, an IOT (Internet of Things) application was used to control and track the output of a modest PV power plant. The research demonstrates the effectiveness of the digitally controlled system created to manage the output voltage of the SEPIC DC-DC converter. They further argue that the ESP8266 and microcontroller's versatility make them an appropriate instrument for allowing remote and real-time monitoring and control of the proposed model from any part of the world. The energy that is produced by the sun is added to the grid so that it may be put to effective use and contribute to satisfying the rising demand for energy. Solar energy is the input that SEPIC uses to charge the batteries and for all of its other processes. In the event that solar photovoltaic (PV) panels are not available, the SEPIC DC-DC converter will derive its energy from AC power.

An Interleaved PFC Boost Converter With Soft Commutations and Voltage Follower Characteristics

This article presents an interleaved boost rectifier for power factor correction (PFC) that operate in the continuous conduction mode and is grounded on the switching cell with switching frequency modulation. The input current naturally follows the shape of the input voltage, which is a resistive input characteristic (voltage follower). In the proposed converter, only one output voltage control loop is required. Moreover, the proposed topology has a wide range of soft commutation and no reverse recovery when the diodes block. This article presents the operating principle, a mathematical analysis of the converter, and four topological variations. In addition, experimental results of a 1-kW rectifier prototype with four different switch technologies [ <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MOSFET</small> , high voltage superjunction <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MOSFET</small> (CoolMOS), silicon carbide (SiC), and insulated gate bipolar transistor (IGBT)], are discussed and their operational characteristics are demonstrated.

Control and monitoring of a Flyback DC-DC converter for photovoltaic applications using embedded IoT system

In this article, the authors present an Internet of Things (IoT) solution for controlling and monitoring a low power photovoltaic system (250 W). Power conditioning is performed by a DC-DC Flyback converter with active clamping. An ESP32 microcontroller is used to implement an output voltage control loop and to communicate, online and in real time, with an internet server. The effectiveness of voltage regulation is proven with experimental results and the authors present evidence that the IoT features work properly.

Flux-Balance Control for LLC Resonant Converters with Center-Tapped Transformers

LLC resonant converters with center-tapped transformers are widely used. However, these converters suffer from a flux walking issue, which causes a larger output ripple and possible transformer saturation. In this paper, a flux-balance control strategy is proposed for resolving the flux walking issue. First, the DC magnetizing current generated due to the mismatched secondary-side leakage inductances, and its effects on the voltage gain are analyzed. From the analysis, the flux-balance control strategy, which is based on the original output-voltage control loop, is proposed. Since the DC magnetizing current is not easily measured, a current sensing strategy with a current estimator is proposed, which only requires one current sensor and is easy to estimate the DC magnetizing current. Finally, a simulation scheme and a hardware prototype with rated output power 200 W, input voltage 380 V, and output voltage 20 V is constructed for verification. The simulation and experimental results show that the proposed control strategy effectively reduces the DC magnetizing current and output voltage ripple at mismatched condition.

A Single-Stage Integrated Boost-LLC AC–DC Converter With Quasi-Constant Bus Voltage for Multichannel LED Street-Lighting Applications

Single-stage boost-LLC ac–dc converters are popularly utilized as the front-end stage of multichannel LED street-lighting drivers. Pulse frequency modulation (PFM) strategy with a duty cycle of 0.5 is commonly utilized in these ac–dc converters. However, PFM has the following drawbacks: 1) high bus voltage limits the ac input voltage range, which makes it only suitable for the input voltage range of 85~135 V and 2) the maximum bus voltage can reach up to three times of the minimum bus voltage, which increases the difficulty of the LLC design. This paper proposed a hybrid modulation strategy, which consists of a bus voltage control loop using asymmetric pulsewidth modulation and an output voltage control loop using PFM. The stable output voltage and the quasi-constant bus voltage can be simultaneously achieved. Furthermore, by increasing bus voltage ripple and employing the twin-bus configuration, the short-lifetime electrolytic capacitors are eliminated, and the efficiency of the total LED driver can be greatly improved. Therefore, universal-input operation, high efficiency, low cost, and long lifetime are the key innovations of the proposed solution. A universal-input 100-W prototype is built to demonstrate the feature of the proposed solution. The experimental results show that the converter achieves a peak efficiency of 92.5% at the input voltage of 130 V and a high power factor value of above 0.95 over the whole input voltage range. With the proposed modulation strategy, the maximum bus voltage is just 500 V under universal input voltage condition, which is greatly lower than that of the traditional PFM controlled boost-LLC converters.

Voltage Balance Control Based on Dual Active Bridge DC/DC Converters in a Power Electronic Traction Transformer

In this paper, a voltage balance control strategy based on dual active bridge (DAB) dc/dc converters in a power electronic traction transformer (PETT) is proposed. Based on this strategy, the output-parallel DAB converters can be equivalent to an input-series-output-parallel system. Furthermore, a PETT starting control method is put forward, which can effectively avoid risks of overcurrent and overvoltage in the PETT starting process. In order to carry out the controller design and system stability analysis, three different kinds of mathematical models of DAB converters are set up. The first model is related to a single DAB converter, the second model reflects the equivalent relation between an output-parallel DAB system and a single DAB converter in terms of the output-voltage control loop, and the third model indicates that the voltage balance control system based on DAB converters is a multiinput-multioutput system. Due to the nonzero off-diagonal elements of the controlled plant, there is a mutual effect between different control loops, which is defined as “interaction” in the multivariable feedback control theory. The stability of the voltage balance control system is made up of two parts, including the stability of each single-input-single-output (SISO) control loop and the influence of the interaction on the system stability. The research is carried out to measure the intensity of the interaction in this paper, and a criterion directly based on the controlled plant is proposed to predict the influence of the interaction, which can obviously simplify the system stability analysis. Considering the particular traction onboard application, a new control structure toward the voltage balance controller is introduced. Based on the new structure, the controller is designed and the stability of the SISO system is analyzed. Finally, a five-cell PETT prototype with rated power of 30 kW is taken to carry out further research, and the experiment results verify the effectiveness and correctness of the proposed algorithms.

Synthesis of the output voltage control loop of a nonlinear Solid State Transformer

The object of the study is an autonomous source of sinusoidal voltage, which consists of a bridge frequency converter with PWM, equipped with an output LC filter and a single-phase nonlinear output transformer with an additional filter capacitor, which is connected to the output of the secondary winding. The factors hindering the technical implementation of the control of this object are analyzed. The nonlinearity of the transformer's magnetic system is approximated by a power series along with odd exponents. The substitution of variables made possible to develop a mathematical description of the circuit in the form of a nonlinear singularly perturbed system of differential equations. It is assumed that there is an attractive invariant surface, which makes it possible to reduce the order of the original system of equations. An analytical form of the equations of this surface in the form of a series in powers of a small parameter is obtained. A local region of state space is defined in which a nonlinearity can be transformed to a form that allows the fulfillment of the conditions of the Poincaré-Lyapunov theorem for a nonlinear system of differential equations. A system of lower-order differential equations is obtained that is equivalent in some region to the original nonlinear singularly perturbed system. The possibility of replacing a nonlinear system of a reduced order by its first approximation for the construction of a control law is substantiated. The control law is synthesized using the Lyapunov function method for the first-approximation system of equations. The control law is a linear combination of the variables of the reduced system of equations. The choice of the Lyapunov function in the form allowing to establish an unambiguous relationship between the coefficients of this function and the scale coefficients of the control law equation is proposed. Analytical expressions for calculating these scale factors are obtained. The results of digital simulation are presented. The simulation was performed taking into account the limitations inherent in the real object of power electronics and affecting the possibility of technical implementation of the obtained control law.Bibl.10, Fig.2

Stable operating area of photovoltaic cells feeding DC–DC converter in output voltage regulation mode

From the perspective of output voltage control stability, this study investigates the stable operating area of photovoltaic (PV) cells feeding the DC–DC converter in output voltage regulation (OVR) mode. In this study, the boost interface converter is taken as an example, and its control system arrangements, small-signal model including the dynamic equivalent circuit of PV cells and the closed-loop transfer functions with different control loop formation are deduced at first. After that, according to the Hurwitz criterion, the essential condition for output voltage control stability is analysed and the relations between control loop formation of the interface converter in OVR mode and the stable operating area are obtained. The validity of the theoretical analysis has been verified by the experiment and simulation results of a 150 W prototype. The investigation shows that: (i) no matter what kind of control loop formation is adopted, the PV cells cannot output the maximum power when the PV interface converter operates in OVR mode; (ii) when the interface converter operates in OVR mode, PV cells can only operate stably in voltage area or current area. Moreover, the type of operating area entirely depends on the converter's output voltage control loop formation.

Single Stage Single Switch Power Supply (S4PS)Design for Low Power HB-LED Lighting

Abstract This paper presents an improved power quality converter (IPQC)-based power supply design for high brightness light emitting diode (HB-LED) low power lighting. The IPQC circuit uses a Cuk buck-boost converter to operate it in a discontinuous conduction mode (DCM) using the voltage follower technique for the mitigation of harmonic contents present in the AC mains current. Subsequently, reduction in harmonic contents results in improving the power quality indices at the AC mains. Single-stage single switch converter topology is used, which has less component count, size and cost as compared to the two-stage converter topology. DCM operation has an advantage that only output voltage control loop is required as compared to three control loops required in the continuous conduction mode operation. An 18-W LED driver is designed, modeled and simulated using MATLAB/Simulink software for 220 V, 50 Hz AC mains. The performance of the proposed LED driver is observed in terms of total harmonic distortion of the input current (THDi), input power factor (PF) and crest factor (CF) taking into account the strict international standard of IEC 61000-3-2 for class C equipments.

Two-Loop Digital Sliding Mode Control of DC–DC Power Converters Based on Predictive Interpolation

Digital implementation of sliding-mode current control applied to dc–dc switching converters is analyzed and developed in this paper. It is based on an interpolation predictive strategy that avoids problems associated to continuous sampling process of the controlled variable and minimizes quasi-sliding effects. In addition to inherent advantages of digital implementation, as programmability, flexibility, complex calculation capability and noise immunity, the proposed strategy maintains robustness and has similar behavior than analog sliding-mode current control implementations. In order to obtain output voltage regulation, an outer proportional-integral digital output voltage control loop is added. Simulated and experimental results in a boost converter are in good agreement with the theoretical predictions.

Three-Dimensional Flux Vector Modulation of Four-Leg Sine-Wave Output Inverters

The time integral of the output voltage vector of a three-phase inverter is often termed the inverter flux vector. This paper addresses the control of a three-phase four-leg sine-wave output inverter having an LC filter at its output, by controlling the flux vector in three dimensions. Flux vector control has the property that an output filter resonance is actively damped by an output voltage control loop alone. Furthermore, an inverter switching action inherently regulates the output voltage rapidly against dc-bus voltage variations. The flux vector control of sine-wave output inverters finds several applications in three-phase four-wire systems. This paper presents a flux modulation method for three-phase four-leg inverters feeding unbalanced and nonlinear loads. All the necessary steps for the digital implementation of the flux modulator are presented. The switching behavior of the modulator has been evaluated, which is useful for the variable fundamental frequency applications of the inverters. To provide experimental validation, the modulator is implemented as a part of the control system for a stand-alone three-phase four-leg inverter with an LC filter at its output. Control system details are also provided. Experimental results indicate the effectiveness of the modulator and control system in providing balanced voltages at the output of the LC filter even under highly unbalanced conditions with nonlinear loads. The resonance damping and voltage regulation properties of the modulator are also apparent from the experimental results.

DC/DC Conversion Systems Consisting of Multiple Converter Modules: Stability, Control, and Experimental Verifications

This paper investigates DC/DC conversion systems constructed from connecting multiple converter modules in series and/or parallel at both the input and output sides. Control strategies aiming at achieving proper sharing of the voltage and/or current at the input or output sides are studied in detail. The relationship between sharing of input voltages/currents and that of output voltages/currents is studied. In particular, the inherent stability of control operations applied at the input side and the output side is analyzed. Based on the analysis, a general control strategy for series-parallel systems, which decouples the output voltage control loop and the sharing control loop, is proposed. Furthermore, three modularization architectures are proposed for input-series-output-parallel (ISOP), input-parallel-output-series (IPOS), and input-series-output-series (ISOS) connected systems. These architectures enjoy full advantages of modularization and no external controller is needed to coordinate the sharing control for the individual modules. Experimental prototypes are built and tested to validate the general control strategy and the proposed modularization architectures.

Constant-frequency sliding-mode and PI linear controllers for power rectifiers: a comparison

Constant-frequency sliding-mode and linear proportional integral (PI) cascaded controllers (internal current loop and external output voltage control loop) for 12-pulse thyristor rectifiers are designed, using new models and convenient assumptions, and their performances compared. The use of sliding-mode control on line-commutated power converters implies the use of fixed-frequency sliding-mode design, originating steady-state errors. These are eliminated using a higher order switching function, with fourth-order Bessel polynomial coefficients, to minimize the response time and to eliminate the overshoot in the reaching mode. Comparisons are made using simulations (MATLAB/SIMULINK blocks) and experimental results. The sliding-mode controllers, as well as the PI controllers, need almost the same hardware and present no steady-state errors and no output voltage overshoots. Besides allowing a faster dynamics than the PI controllers, the proposed sliding-mode approach provides a new, nonlinear theoretical frame for solving the control problem of power rectifiers with output filters.

Power factor preregulators with improved dynamic response

An improved control strategy of standard power factor preregulators (PFPs) is proposed which allows fast output voltage response while maintaining a high power factor. This is obtained by compensating for the intrinsic low-frequency output voltage ripple, thus allowing a higher bandwidth of the output voltage control loop. This method does not require additional sensing, but only a multiplier and simple analog circuitry, and works well with a universal input voltage range. Experimental tests on a boost power converter with average current control confirm the validity of the approach.

High performance control of the series–parallel resonant converter

The authors describe the operation, characteristics and design of a two-loop control technique for a MHz-switching series–parallel resonant converter. A resonant current feedback loop is used to determine the transistor switching instants resulting in the fourth-order converter characteristics becoming third order and, furthermore, being insensitive to operating conditions. The technique exploits the inherent delays in MHz-switching converter systems to provide well-damped dynamics. An output voltage control loop bandwidth of 100 kHz is achieved.

Microprocessor based robust digital control for UPS with three-phase PWM inverter

This paper describes a novel method of robust (insensitive to system parameter variations and load current changes) and fast digital control for an uninterruptible power supply (UPS) with a three-phase PWM inverter. The purpose of this paper is to propose a method by which characteristics better than those by conventional methods are obtained using an algorithm simpler than that of conventional methods. The experiments show that the purpose is achieved and the proposed method offers a total harmonic distortion of 0.6% of the output voltage waveform at a full nonlinear load. The analysis shows that the stability of the method is sufficient. Three features of the method are: (a) a capacitor current observer for stabilization and a disturbance observer for robustness are used to compensate the time lag by the computation and the disturbances, in a minor loop of the capacitor current through an inductor-capacitor filter of the inverter; (b) new models of the inverter and the disturbances are established to simplify these observers; and (c) the output voltage control loop can be designed easily and exactly because the minor loop realizes a rapid and robust control of the current.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>