State-space Averaging Research Articles

Small-Signal Analysis and Control of Soft-Switching Naturally Clamped Snubberless Current-Fed Half-Bridge DC/DC Converter

This paper presents small-signal analysis of a soft-switching naturally clamped snubberless isolated current-fed half-bridge (CFHB) DC-DC converter using state-space averaging. A two-loop average current controller was designed and implemented on a digital signal processor. The complete design procedure is presented here. Simulation results using software PSIM 11.1 are shown to validate the stability of the control system and the controller design. Experimental results for the step changes in load current vividly demonstrated satisfactory transient performance of the converter and validated the developed small-signal model and the control design.

Analysis of an efficient interleaved ultra‐large gain DC–DC converter for DC microgrid applications

This study deals with steady-state analysis and control of a step-up interleaved winding cross-coupled inductor DC–DC converter with high voltage gain and reduced voltage stress across semiconductors using voltage multiplier cells (VMCs). Because of the interleaved scheme, the thermal stress is reduced and the input current ripple is minimised. The leakage energy is recycled by passive lossless clamp circuit to the output. Meanwhile, the voltage stress across the semiconductors is substantially low. Hence, MOSFETs with less ON-state resistances and diodes with a less forward voltage drop can be utilised that improves the circuit performance. The operation principle and the steady state are discussed. Small-signal modelling of the proposed converter is derived via state-space averaging technique and a dual loop controller for output voltage regulation is designed. The adopted strategy utilises a fast dynamical inner loop to control the input current and an outer loop for the output voltage regulation. Finally, a 1 kW prototype with 60 V–1 kV voltage conversion is fabricated and tested to probe the carried analysis.

A comparison of harmonic modeling methods with application to the interconnection and the control of switched systems

Many harmonic modeling approaches have been introduced in the literature, such as generalized state-space averaging, dynamic phasors, extended harmonic domain, and harmonic state-space. They are capable of capturing both the transient evolution and the steady-state of harmonics. They model the frequency coupling nature of a system and can highlight the frequency couplings within interconnected components. By these modeling techniques, a linear time-periodic model can be converted into a linear time-invariant model, which allows the use of traditional analysis and control methods. This paper presents a state of the art of harmonic modeling approaches. Its contribution is to clearly establish strong links between the different literature approaches and to develop a general harmonic methodology that unifies them. A rigorous theoretical framework for the modeling, analysis and control of linear time-varying systems with an arbitrary number of harmonics is developed. In particular, a harmonic model is proposed from which all the literature models can be easily derived. This paper also deals with the harmonic modeling of switched affine systems. It shows the advantages of harmonic modeling to analyze the frequency couplings within associated switched systems and to the control with active filtering.

A Novel Transformerless Single-Stage Grid-Connected Solar Inverter

A novel tranformerless single-stage grid-connected solar inverter with a combination of a bidirectional dc/dc boost converter followed by a flyback inductor inverter is proposed. The inverter shares a common ground with the photovoltaic (PV) panel and the grid, which realizes a zero leakage current and it is the most desired feature in transformerless inverters. Further, the proposed inverter provides the boost voltage operation, hence it does not require a second stage which decreases the system cost and increases the system reliability. The other advantage of the proposed inverter is that it provides both the symmetrical positive voltage gain and negative voltage gain, which allows to use simple sinusoidal pulsewidth modulation technique for realizing the ac sinusoidal output voltage. The proposed inverter steady-state operation and the design equations are presented in detail. The converter dynamic model is developed using state-space averaging approach, and a proportional resonant current controller is designed for inverter closed-loop operation with the grid. The presented analysis and the design are verified with both the simulation and experimental results.

LC Impedance Source Bi-Directional Converter with Reduced Capacitor Voltages

This paper proposes an LC (Inductor and Capacitor) impedance source bi-directional DC–DC converter by redesigning after rearranging the reduced number of components of a switched boost bi-directional DC–DC converter. This new converter with a conventional modulation scheme offers several unique features, such as a) a lower number of components and b) reduced voltage stress on the capacitor compared to existing topologies. The reduction of capacitor voltage stress has the potential of improving the reliability and enhancing converter lifespan. An analysis of the proposed converter was completed with the help of a mathematical model and state-space averaging models. The converter performance under different test conditions is compared with the conventional bi-directional DC–DC converter, Z-source converter, discontinuous current quasi Z-source converter, continuous current quasi Z-source converter, improved Z-source converter, switched boost converter, current-fed switched boost converter, and quasi switched boost converter in the Matlab Simulink environment. MATLAB/Simulink results demonstrate that the proposed converter has lesser components count and reduced capacitors’ voltage stresses when compared to the topologies mentioned above. A 24 V to 18 V LC-impedance source bi-directional converter and a conventional bidirectional converter are built to investigate the feasibility and benefits of the proposed topology. Experimental results reveal that capacitor voltage stresses, in the case of proposed topology are reduced by 75.00% and 35.80% in both boost and buck modes, respectively, compared to the conventional converter circuit.

A Photovoltaic-Based DC Microgrid System: Analysis, Design and Experimental Results

Due to the exhaustion of fossil energy, the utilization of renewable energy resources is developing quickly. Due to the intermittent nature of the renewable energy resources, the energy storage devices are usually adopted in renewable power generation system to enhance the system reliability. In this paper, the photovoltaic-based DC microgrid (PVDCM) system is designed, which is composed of a solar power system and a battery connected to the common bus via a boost converter and a bidirectional buck/boost converter, respectively. As the photovoltaic (PV) panels might operate in a maximum power point tracking (MPPT) mode or constant voltage mode, meanwhile, the power can flow between the battery and the load bidirectionally. Therefore, for the sake of optimizing power utilization in the PVDCM system, a control strategy making the system able to switch from one operating mode to another smoothly and automatically is proposed in this paper. Moreover, the small-signal modeling method based on averaged state-space is no more applicable in this study, thus the nonlinear analysis method with discrete-time mapping model is adopted for stability analysis. Based on the stability analysis, the closed-loop parameters are designed to make sure the whole system can operate properly in all operating modes. The control strategy and stability analysis based on the nonlinear analysis method in the closed-loop design are verified by experiment results.

A new effective robust nonlinear controller based on PSO for interleaved DC–DC boost converters for fuel cell voltage regulation

Output voltage regulation of DC–DC converters has recently gained an increasing attention to face the many system nonidealities. The fast switching behavior is nonlinear time varying, the presence of model and measurement uncertainties, and large variations, are all inherited challenges. The aim of the present work is to design a robust nonlinear controller that ensures satisfactory and robust output voltage regulation for a proton-exchange membrane fuel cell (PEMFC) based on a DC–DC Interleaved Boost Converter (IBC). A state-space model of the DC–DC IBC is first derived using the state-space averaging technique, and a mathematical model is constructed for the PEFMC. In this regard, a robust nonlinear controller and a proportional integral controller are proposed. The controllers are tuned though particle swarm optimization algorithm to estimate their good parameters assuring the desired performance is met. The integral of absolute error criterion is used to improve the dynamic performance of the overall controlled system. Furthermore, the closed-loop stability is analyzed using the Lyapunov stability theorem, and the effectiveness of the closed-loop system is validated under various operating conditions of the PEMFC and load perturbations. Compared to other methods, the obtained results demonstrate a superior performance of the proposed control strategy in terms of its robustness to variations and uncertainties, smooth tracking of a varying set-point and faster transients.

Fractional analog scheme for efficient stabilization of a synchronous buck converter

Abstract This paper presents the design and control of power electronic synchronous buck converter. Even though a synchronous buck converter is more popular and more widely available, it is not always efficient as nonsynchronous. Firstly, the inputoutput linearization from the state space averaging of the converter is studied, after which a small AC signal analysis is introduced to obtain the dynamic transfer function. All the parameters of the converter are calculated based on the output voltage, current ripples as well as the input voltage. For robustness, the controller is implemented by comparing the response of integer order with non-integer (fractional) order controller, simply known as fractional order controller (FOC). The fractional order derivative is implemented from the Oustaloup approximation and the controller parameters are being tuned using Nelder Mead approximation bases on a system model. It is shown that the FOC performance is comparatively better in presence of the load disturbances and parameter variations. The experimental study with the real-time fractional PI is possible to make for a stand-alone embedded application using FPAA. The proposed technique does not require any digitization of the signal, so it can be easy to implement with improved performance. The effectiveness of the analog controller is discussed, giving some future directions to adopt the new fractional controller.

Design of Capacitive Wireless Power Transmission System in Seawater

As an emerging power supply method, wireless power transmission has attracted extensive attention from researchers at home and abroad. Since there is no direct contact of the wires, it is expected to solve the problem of power supply life of the underwater robot. First of all, this paper combines the working principle of capacitive wireless power transmission, analyzes the working state of the circuit by using the generalized state space average, and obtains the working frequency of realizing the soft switching state. Secondly, two different coupling mechanisms are designed and Maxwell finite element simulation is carried out to calculate the capacitance value and field strength distribution. Finally, the underwater wireless power transmission system is built. The influence of transmission distance d and different coupling mechanisms on output power is discussed. The following conclusions are obtained: (1) As the transmission distance d increases, the output power decreases and the electromagnetic interference increases. (2) Cylindrical capacitors have higher power density and smaller electromagnetic interference than parallel plate capacitors. The research results provide an important reference for future underwater wireless power transmission systems.

Mathematical Modeling of Current Source Matrix Converter with Venturini and SVM

The study of Current Source Matrix Converter (CSMC) static properties using the averaged state-space method for two modulation strategies Venturini and Space Vector Modulation (SVM) is the subject of this article. The converter properties for both modulation strategies have been examined and compared. The modeling approach based on the averaged state space method presented in this paper is relatively simple and requires only a small number of mathematical transformations. The averaged set equation is obtained directly from the three-phase schematic circuit, taking into account the sequences of switching patterns and modulation strategies. All the obtained results have confirmed that CSMC has some interesting properties, such as buck–boost output voltage regulation unlike the classic Matrix Converter (MC), in which the maximum voltage gain is 0.866.

A General Frequency-Domain Model of Trailing-Edge and Leading-Edge Carrier PWM dc–dc Converter Based on Hybrid Continuous and Discrete-Time Descriptions

This article proposes a general frequency-domain model to reflect the effect of trailing-edge and leading-edge carrier on the stability of the pulsewidth modulation (PWM) dc-dc converter. The state vector in the general state-space averaging (SSA) model is considered as the sampled value of the actual state vector rather than the average value. In this way, the continuous and discrete-time descriptions can be used together to maintain a balance between accuracy and simplicity. In the proposed model, the main circuit and controller are described by a continuous model with the same equations as the existing SSA model. Therefore, the simple structure of the continuous model is inherited. The PWM carrier comparison component is described by a discrete-time model (DTM), which can accurately reflect the effects of PWM carrier and state vector ripple. Thus, the high accuracy of DTM is maintained as well. In order to show the advantages of the proposed model, the comparison between the proposed model and other existing models is made. Compared with the SSA model and the discrete average model, the proposed hybrid model is more accurate. Compared to the DTM, the proposed hybrid model is more convenient to use. Simulation and experiment results verify the above analyses and advantages.

A Bidirectional Wireless Power Transfer System Control Strategy Independent of Real-Time Wireless Communication

For the bidirectional wireless power transfer (BWPT) technology, the phase synchronization between the transmitting and receiving converters is very essential and difficult to achieve by wireless communication between two sides because the delay and data transfer interval of wireless communication severely influence the control performance. This article proposes a novel control strategy for BWPT, which can achieve the phase synchronization and maximum efficiency point tracking independent of the real-time wireless communication. To solve the overshoot and oscillation problem incurred by the proposed control strategy and the nature of the system itself, the dynamics of a series-series compensated BWPT system is then analyzed and a small-signal model of this system is derived based on the generalized state space averaging and extended describing function methods. Using the small-signal model, a BWPT control system based on the proposed control strategy is designed and optimized. The validity of the proposed strategy and the performance of the control system are verified experimentally using a 3.3-kW prototype system.

Analysis and Modeling of a New Coupled-Inductor Buck–Boost DC–DC Converter for Renewable Energy Applications

A new coupled-inductor buck–boost converter (CIBuBoC) is proposed in this article. In the proposed CIBuBoC, an ultra-high step-up/step-down voltage conversion ratio and step-up/step-down boundary adjustment are achieved compared to the other related buck–boost converters using two power switches with simultaneous operation along with a coupled inductor. This circuit has a simple structure with two cascade semistage and some features including ultra-extended output voltage, continuous input current with low ripple, positive polarity of the output voltage, and common ground. These features make the CIBuBoC more suitable for many applications such as photovoltaic systems. Moreover, the voltage stress across each power switch is much lower than the other buck–boost converters, which led to power mosfet s selection with lower drain-source on -resistance ( R ds). Therefore, the proposed converter has also enough high efficiency. All steady-state and stress analysis, and also, comparisons with other related converters in continuous conduction mode are provided in detail. Also, using the state-space averaging technique, the low-frequency behavior of the proposed CIBuBoC is studied completely. Experimental results of a 100-W step-up 30–200 V and a 35-W step-down 30–22 V confirm the theoretical advantages of the proposed circuit.

Small Signal Analysis and Control of Snubberless Naturally-Clamped Soft-Switching Current-Fed Push-Pull DC/DC Converter

This article presents detailed small-signal modeling and closed-loop control design for transient performance evaluation of a high-frequency snubberless isolated current-fed push-pull dc-dc converter. The topology attains the natural commutation of semiconductor devices through zero current switching. The state-space averaging technique is employed to derive the transfer functions. A two-loop average current controller is designed and implemented on a digital signal processor to evaluate and demonstrate the transient performance of the converters. A complete procedure for a closed-loop control design is illustrated. Simulation results using PSIM 11.1.64 with the designed controller are shown to validate the stability of the system. Experimental results demonstrated satisfactory transient performance at various load conditions of the converter and validated the derived model and the control design.

A New Multilevel Inverter Topology With Reduced Power Components for Domestic Solar PV Applications

Power electronic converters are used to nullify the input fluctuations from a solar photovoltaic unit because of intermittent solar irradiance and to make the terminal voltage grid compatible with the desired frequency. The conventional two-level converters suffer from low power quality and high voltage stress. In this article, a new multilevel inverter topology called Dual Source Multilevel Inverter (DS-MLI) with fewer power switches is proposed for solar PV power conversion systems. It can operate in symmetric and asymmetric operating modes with no cascading. This reduces the switching components required to produce several levels in the staircase voltage waveform. A closed-loop control algorithm is designed using the state-space averaging technique, and we assess the dynamic behaviour of the system under step change. We carry the simulation out in MATLAB environment. The experimental prototype of DS-MLI rated 1 kW is fabricated using FGA25N120-ANTD IGBTs, and an eco-sense made solar PV emulator is used for analysing the performance of DS-MLI while interfacing with solar PV unit. We compare the suggested scheme with its conventional counterpart in the aspects of components required, cost and efficiency, and the results are presented.

Modelling, design and implementation of quadratic buck converter for low power applications

This paper discusses the modelling, design and implementation of quadratic buck converter (QBC) for low voltage CPU voltage regulator applications. The small-signal modelling of QBC is characterised by state-space averaging technique. The QBC has been applied with average current-mode (ACM) control strategy in order to evaluate steady sate as well as dynamic performance. The hardware development of QBC is exploited using FPGA controller. The PSIM simulation results are validated with the experimental results in terms of line and load regulations. It can be verified from results that the system stability is guaranteed for a wide range of operating conditions.

Modelling and control of dual input boost converter with voltage multiplier cell

A dual input DC-DC converter with dual boost and integrated voltage multiplier cell operating at duty cycles larger than 0.5 is a necessity to achieve a high voltage gain for energy systems possessing two independent renewable energy resources. Output voltage regulation during load changes and input disturbances is the requisite of an energy system, which is achieved by the implementation of a suitable control action, which further requires the dynamic model of the converter. The modelling of this higher order converter with overlapping switching signals is complicated. The small-signal transfer function model based on state-space averaging followed by small-signal linearisation is verified using MATLAB and powersim (PSIM). The output voltage to duty cycle transfer functions significantly contributes to representing the converter dynamics from which its right-half s -plane zero is analysed. Since it is a non-minimum phase system, a dual loop control strategy is adopted. Voltage regulation and active current sharing are ensured from the simulation and experimental responses of the uncompensated and compensated systems. Further, from the derived integer-order converter model a fractional controller is designed and its dynamic response is compared with the traditional controller. A 200 W prototype of the converter is developed, and the control is implemented using field-programmable gate array.

Research on Linear Active Disturbance Rejection Control in DC/DC Boost Converter

This paper proposes a cascade control strategy based on linear active disturbance rejection control (LADRC) for a boost DC/DC converter. It solves the problem that the output voltage of boost converter is unstable due to non-minimum phase characteristics, input voltage and load variation. Firstly, the average state space model of boost converter is established. Secondly, a new output variable is selected, and a cascade control is adopted to solve the problems of narrow bandwidth and poor dynamic performance caused by non-minimum phase. LADRC is used to estimate and compensate the fluctuations of input voltage and loads in time. Linear state error feedback (LSEF) is used to achieve smaller errors than traditional control method, which ensures the stability and robustness of the system under internal uncertainty and external disturbance. Subsequently, the stability of the system is determined by frequency domain analysis. Finally, the feasibility and superiority of the proposed strategy is verified by simulation and hardware experiment.

Research on modelling and simulation of converters for electromagnetic transient simulation in photovoltaic power generation system

Large-scale photovoltaic (PV) power plants connected to the grid leads to the complex calculations in the modelling and simulation of the power system, especially in the electromagnetic transient progress. Common averaging methods are studied for modelling a grid-connected converter to simplify the calculation and balance accuracy and efficiency in simulation. The piecewise technique, which combines the time segment with similar operating characteristic, is applied to different averaging models of converters. The advantages and disadvantages of different piecewise averaging models are compared. In addition, a new piecewise generalised state-space averaging (P-GSSA) model is derived and a multiple time scale modelling is achieved for the grid-connected converters in PV systems. The model error and accuracy of the P-GSSA model are analysed, the physical significance and the influence factors in the model error of P-GSSA model are discussed. The research shows that P-GSSA model is flexible to be used in a PVs system simulation, and it can accurately reflect the steady state and transient characteristics of a converter. The analysis of the P-GSSA model is verified by simulating a DC/AC converter and a PV system.

A hybrid control strategy for Z-source inverter DG systems

A hybrid control system for Z-source inverter (ZSI) with LC filter which is used in distributed generation (DG) systems is presented in this study. The proposed system has two different controllers, dc-side and ac-side. While designing the ac-side controller, a proportional-resonant (PR) controller was used. Besides, to be able to adjust the voltage of the Z-source capacitor according to the reference value of it, a proportional–integral (PI) controller was employed on the dc-side of the ZSI. In the end, a dynamic ZSI model was obtained by the help of small signal analysis and state space averaging. After the mathematical model of the ZSI was derived, the dc-side and ac-side controllers were designed. Using both controllers, inverter reference tracking performance was enhanced. The proposed controller offers superior output voltage regulation regardless of the linear and nonlinear loads. Taking into account the abrupt variations in both the dc source and linear/nonlinear load level, the effectiveness of the proposed control system was tested and supported by Matlab®/Simulink simulations.