Right-half Plane Zeros Research Articles

A novel modulation for four‐switch Buck‐boost converter to eliminate the right half plane zero point

AbstractThe four‐switch Buck‐Boost (FSBB) converter are widely used in combination with other isolated converter to extend the voltage range capability of the overall structure. When the converter operates in buck‐boost mode and boost mode, it exhibits a right half plane zero (RHPZ) in the control to output transfer function. This characteristic would cause negative impact to stability of the converter. In order to eliminate the RHPZ, a novel modulation method is proposed in this paper. The buck mode is introduced to the modulation to adjust the voltage gain, and the corresponding average state space modeling for the FSBB with the proposed modulation is established. The simulation of the converter with the proposed modulation method and traditional modulation are presented. Finally, experiment results by hardware in the loop (HIL) platform is employed to verity the correctness of theoretical analysis results.

High voltage gain minimum‐phase isolated DC‐DC converter with improved transformer utilization

AbstractThe standard structure of an isolated SEPIC (iSEPIC) does not have a minimum‐phase nature, which signifies no additional support for the output capacitor during ON‐time conditions. Consequently, it has high voltage stress, right half plane (RHP) zeros presence, DC component in the transformer core, and less transformer utilization. This paper presents a modification in a iSEPIC converter having higher voltage gain over a conventional iSEPIC converter. This work analyzes a modified iSEPIC structure by providing additional support to the output capacitor during ON‐time conditions. As a result, the nonminimum‐phase nature will be transformed into the minimum‐phase nature. Consequently, all the mentioned demerits of the standard iSEPIC structure are eliminated The derived discrete‐time modeling analyzes the RHP zeros dependence on the load variation. This modification also leads to improvement in dynamic performance to accommodate the load variation. Finally, a 60 W modified iSEPIC prototype is developed to validate the proposed analysis.

Analysis and circuit design of isolated forward SEPIC converter with minimum-phase stability

PurposeConventional isolated dc–dc converters offer an efficient solution for performing voltage conversion with a large improved voltage gain. However, the small-signal analysis of these converters shows that a right-half-plane (RHP) zero appears in their control-to-output transfer function, exhibiting a nonminimum-phase stability. This RHP zero can limit the frequency response and dynamic specifications of the converters; therefore, the output voltage response is sluggish. To overcome these problems, the purpose of this study is to analyze, model and design a new isolated forward single-ended primary-inductor converter (IFSEPIC) through RHP zero alleviation.Design/methodology/approachAt first, the normal operation of the suggested IFSEPIC is studied. Then, its average model and control-to-output transfer function are derived. Based on the obtained model and Routh–Hurwitz criterion, the components are suitably designed for the proposed IFSEPIC, such that the derived dynamic model can eliminate the RHP zero.FindingsThe advantages of the proposed IFSEPIC can be summarized as: This converter can provide conditions to achieve fast dynamic behavior and minimum-phase stability, owing to the RHP zero cancellation; with respect to conventional isolated converters, a larger gain can be realized using the proposed topology; thus, it is possible to attain a smaller operating duty cycle; for conventional isolated converters, transformer core saturation is a major concern, owing to a large magnetizing current. However, the average value of the magnetizing current becomes zero for the proposed IFSEPIC, thereby avoiding core saturation, particularly at high frequencies; and the input current of the proposed converter is continuous, reducing input current ripple.Originality/valueThe key benefits of the proposed IFSEPIC are shown via comparisons. To validate the design method and theoretical findings, a practical implementation is presented.

Analysis and implementation of feedback linearisation controller for fuel cell-fed boost converter

ABSTRACT Fuel cell needs to be integrated with dc-dc boost converters to supply load at elevated voltages. Due to the presence of right half plane zero (RHPZ) in the output voltage to duty cycle transfer function of the boost converter and the nonlinear V-I characteristics of the fuel cell, it necessitates the usage of nonlinear controllers. This paper proposes an effective stabilising feedback linearisation (FDBKLN) controller for fuel cell-fed boost converter to provide improved dynamic performance and tight voltage regulation for wide load variation. Performance of the controller has been tested in simulation using the developed tunable minimal order fuel cell model and validated through experiments for fuel cell-fed 600W boost converter. Stability of the proposed controller is also verified using Lyapunov theorem.

Tri-State Coupled Inductor Based High Step-Up Gain Converter Without Right Hand Plane Zero

This brief proposes a novel tri-state Coupled Inductor (CI) based high step-up gain converter without Right Half Plane (RHP) zero. The basic Coupled Inductor based Boost Converter (CIBC) can achieve high step-up gain by changing the turn ratio of CI and duty cycle. However, the control to output voltage transfer function of basic CIBC converter in CCM has RHP zero hence non-minimum phase behavior with limited bandwidth and unstable operation of the converter when step changes in duty cycle. RHP zero can be eliminated from the basic CIBC by providing freewheeling period in converter operation hence additional degree of freedom to control energy transfer to output capacitor. Thus, the converter achieves stable operation and improves the bandwidth. The small-signal model of the proposed converter is derived to verify the claim. All theoretical findings are verified by experimental results. Experimental results are provided from implemented laboratory prototype of input voltage of 24 V to output voltage of 100 V and 200 W power.

Performance Improvement by Sampling Position Approach in Dual Loop Digital ACM Controlled DC-DC Boost Converter

In DC-DC boost converter mostly discontinuous voltage ripple is associated with Equivalent Series Resistance (ESR) of the output side capacitor. This voltage ripple makes the design of digital controllers challenging in deciding the appropriate sampling position in one switching period. The necessity of Right Half Plane Zero (RHPZ) elimination, which impacts the stability is managed by shifting the sampling position to OFF-time duration. This is mostly analyzed in the frequency domain. The proposed work provides the time-domain analysis in consideration of ESR impacting the RHPZ. A dual loop Digital Average Current Mode (DACM) controller which has two sampling position freedom is considered in this brief. The ESR value of the output capacitor for extracting the benefits of RHPZ elimination is proposed with help of the discrete-time modeling technique. An analytical discussion about the influence of RHPZ elimination with time-domain characteristics such as, voltage deviation, peak-to-peak inductor current oscillations, and efficiency is presented. Finally, two 60W boost converters prototype with different output capacitor (C) and its ESR <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(r_{C})$ </tex-math></inline-formula> values are developed to validate the proposed analysis.

Design of a novel robust adaptive cascade controller for DC‐DC buck‐boost converter optimized with neural network and fractional‐order PID strategies

AbstractA cascade technique with two control loops is designed for a DC\DC Buck‐Boost converter that is a right half‐plane zero (RHPZ) structure called a non‐minimum phase system. This concept presents several challenging constraints for designing well‐behaved control techniques. Cascade controllers can provide various benefits compared with single loop controllers such as higher safety, higher robustness, and higher stability. This strategy assumes the system as a black‐box structure without the need for a mathematical model of the system. This benefit can decrease the computational burden and provides faster dynamics along with ease of implementation. This technique consisted of an outer Fractional‐order PID voltage controller tuned with the Antlion Optimizer (ALO) algorithm, which provides a reference current for the inner control loop of the Neural Network‐based LQR (NN‐LQR) controller. The basic principle in cascade controllers is a more rapid performance of the inner loop that has been satisfied with the NN‐LQR strategy, which optimizes and tunes the gains of the LQR controller and shows faster dynamics and higher robustness. It should be mentioned that the number of neurons is limited to 2 and 4 in each layer to decrease the computational burden with lower complexity. Also, the ALO algorithm is a modern nature‐inspired algorithm used to tune the PID gains with better results under‐constrained problems with diverse search spaces. Considering the negative impacts of various disturbances on a power converter, a Fractional‐order‐based PID (FO‐PID) control technique is a proper alternative since it shows higher robustness in load uncertainties along with better dynamical responses based on its extra degree of freedom. Moreover, to evaluate the superiority of this controller, two other controllers are designed using the PSO algorithm for PID and FO‐PID controllers. Finally, the presented cascade controller has been tested in various working conditions through simulation and experiment results.

A novel control architecture for floating wind turbines

The control of Floating Wind Turbines (FWTs) is challenging, as they possess much lower natural frequencies related to the structure's rigid body motion, which creates an undesirable coupling between tower motion and the blade pitch control. As a result, the tower motion is negatively damped triggering instability. This is because of the presence of Right Half Plane Zeros (RHPZs) imposing fundamental limitation on the control bandwidth. To address this problem, different solutions were proposed with varying control structures ranging from Single-Input, Single-Output (SISO) controllers to Multiple-input, Multiple-output (MIMO) ones. In this paper, a new control structure, of Single-Input, Multiple-Output (SIMO) is proposed that is able to lift the bandwidth limitation, while using simple elements that match the industry demands.

Sensor/actuator colocation feasibility for distributed damping control using active power modulation

Multi-use distributed active power modulation devices, including energy storage, have the potential to transform the dynamic performance and resilience of modern power systems. Rapid response characteristics relative to traditional power delivery equipment paired with traditional uses (arbitrage, reserve, etc.) make storage an obvious choice for multi-use operation, adding value for asset owners while augmenting stability for reliable operation. Limitations to distributed power control are investigated to provide guidance for those interested in separated sensors and actuators. Substantive distance between the sensor/actuator pair results in non-minimum phase (NMP) which complicates the control design, reducing feedback system effectiveness. It is shown that wide-area control (WAC) is limited by the presence of NMP induced by closed right-half plane (CRHP) zeros - a consequence of sensors placed at locations separated from modulation bus(es). Such geographic separation may be driven by economics, asset owner jurisdiction, technology and/or policy, and is therefore unavoidable. This work suggests that system designers must perform a collocation study before control design and testing. A well-known WAC architecture using synchrophasors as sensors and energy storage devices for active power injection is presented as a detailed case study. • Collocated sensor–actuators pose difficulties which may force modest separation. • Closed right-half plane (CRHP) zeros may result due to such separation. • Noncollocated sensor–actuator pairs may reduce performance and threaten stability. • Bandwidth and performance limitations regarding collocation are determined.

Optimized Model Based Controller with Model Plant Mismatch for NMP Mitigation in Boost Converter

In this paper, an optimized Genetic Algorithm (GA) based internal model controller-proportional integral derivative (IMC-PID) controller has been designed for the control variable to output variable transfer function of dc-dc boost converter to mitigate the effect of non-minimum phase (NMP) behavior due to the presence of a right-half plane zero (RHPZ). This RHPZ limits the dynamic performance of the converter and leads to internal instability. The IMC PID is a streamlined counterpart of the standard feedback controller and easily achieves optimal set point and load change performance with a single filter tuning parameter λ. Also, this paper addresses the influences of the model-based controller with model plant mismatch on the closed-loop control. The conventional IMC PID design is realized as an optimization problem with a resilient controller being determined through a genetic algorithm. Computed results suggested that GA–IMC PID coheres to the optimum designs with a fast convergence rate and outperforms conventional IMC PID controllers.

A Spectrum-based Filter Design for Periodic Output Regulation of Systems with Dead-Time

This paper presents a filter structure that allows the user to place desired poles and the necessary zeros to achieve periodic regulation to the closed-loop sensitivity through Internal Model Control framework. The periodic regulation is aimed at stable SISO linear systems suffering from input dead-time and having no closed right-half plane zeros. The negative Effects of the dead time on tracking/rejection are compensated by introducing another delay which is tuned independently from the filter thanks to its structure. The main focus is given to constructing the filter with polynomials. However, it can be readily extended to quasi-polynomials. The findings are verified with a computer simulation of a vibration control task.

Multioutput Hybrid Solar Inverter With No Right Half-Plane Zero and Reduced Common-Mode Leakage Current

In this article, a multioutput-based transformerless hybrid solar inverter (TLHSI) with no right half-plane zero (RHPZ) and reduced common-mode leakage/ground current is presented for photovoltaic (PV) based microgrid applications. In the proposed multioutput TLHSI, two magnetically coupled inductor coils are placed between the input and dc output sides along with a dc-link capacitor to continuously provide the stored energy to the dc load so that the RHPZ is eliminated and, thus, makes it a minimum phase system. Furthermore, a hybrid unipolar sinusoidal pulsewidth modulation technique is established to nullify the high-frequency components of common-mode voltage across the PV to ground stray capacitor. Also, it normalizes both dc and ac loads at the same instant from a single dc input during each operating state of the proposed TLHSI. The shoot-through issue is resolved in the proposed TLHSI, which increases the system reliability. Furthermore, as the deadtime is not required in between the switching pulses, the quality of the inverter output voltage improves. The performance analysis of the proposed TLHSI is compared with the existing topologies. To validate the performance of TLHSI, a scaled down 340 W laboratory prototype is developed.

A new Buck-Boost converter with capability of eliminating right-half-plane zeros

ABSTRACT In this paper, a new Buck-Boost converter with coupled inductor that can eliminate right-half-plane (RHP) zeros is proposed. The steady-state model and small-signal model of the proposed Buck-Boost converter in continuous conduction mode (CCM) are established and analysed, and its control-to-output voltage transfer function is obtained. The condition for this proposed converter to eliminate RHP zeros is derived based on the Mason formula. The comparisons among the other extant four Buck-Boost converters and the proposed Buck-Boost converter are carried out, and it shows that the proposed Buck-Boost converter has the advantage of eliminating RHP zeros. Finally, some simulations and circuit experiments are presented for confirmation.

A Magnetically Coupled-Inductor Boost Converter with High Bandwidth and Fast Dynamic Response

Transient modeling analysis of the traditional DC/DC converters shows their worse effect of nonminimum-phase characteristics due to right-half-plane (RHP) zero existence in their plant transfer function. This RHP zero restricts the bandwidth of the switching converters and, that is the main reason for slower response. The motivation of this paper is to present a new technique for eliminating the RHP zero from the dynamics of a conventional boost converter that can solve the problems associated with the nonminimum phase converters and, to focus on its analysis, design and modeling to achieve a high voltage gain as well as the RHP zero cancellation. The proposed technique uses a transformer combined with switching capacitor cells. The striking feature of the suggested topology is its minimum-phase structure, further enhancement of the voltage gain, switching stress reduction, achievement of an improved frequency response and easiness for the design of a closed-loop control scheme to perform the voltage trajectory tracking task. First, the operation of the proposed converter is identified and then, the corresponding circuit performance is evaluated. By using a suitable design, the control-to-output-voltage transfer function is completely free from the RHP zero. The significant advantages of the proposed converter are established via comparisons. To confirm the design approach and theoretical findings, the simulations are introduced and, numerical experimental results such as Bode diagrams are presented.

Down-Sampled Repetitive Controller for Grid-Connected Ćuk CCM Inverter

The Ćuk inverter operating in the continuous conduction mode (CCM) is susceptible to grid disturbances, and its transfer function has two right-half-plane zeros (RHPZs), which causes a large phase lag. To improve the output-tracking precision in the grid-connected environment, a repetitive controller (RC) with linear phase-lead compensation has been developed for the Ćuk inverter. However, this controller requires a heavy computational burden and memory space; these problems become more severe as the converter operates at a higher switching frequency. This article proposes to use a down-sampled repetitive controller (DRC) for the Ćuk CCM inverter to alleviate these problems. The down-sampling technique itself can significantly reduce the computational burden and memory space of RC. On the contrary, its control accuracy becomes very low, particularly for the Ćuk CCM inverter. Unlike conventional module integrated inverters (MIIs), the Ćuk CCM inverter must adopt a fractional-order phase-lead compensation algorithm to compensate for the effect of the large phase lag in the down-sampled environment. To clarify the inevitable usage of DRC with a fractional-order phase-lead compensation for Ćuk CCM inverter, the DRC is classified into four types; this article provides its detailed design guideline based on stability analysis of the overall control system and also presents design examples for representative MIIs. Experiments using a 300-W prototype Ćuk inverter validate that the proposed control approach achieves acceptable output-tracking accuracy. The total computation time and memory space with the DRC decrease by 76.0% and 80.0% compared to those with the conventional RC, while the output-tracking accuracy with the DRC decreases by 0.42%.

커플드 인덕터기반의 계통 연계형 Ćuk CCM 인버터의 동적 모델링과 제어기 설계

This paper presents a dynamic modeling and controller design for a grid-connected Ćuk continuous conduction mode (CCM) inverter with a coupled inductor. The primary- and secondary-side inductors of the conventional Ćuk converter are integrated into one coupled inductor in the presented Ćuk CCM inverter, and it reduces the number of passive components. To make the Ćuk CCM inverter with a coupled inductor connected with the grid utility, an output current controller should be designed appropriately. However, the output current control of the presented Ćuk inverter is difficult due to the existence of the right-half plane (RHP) zeros in its transfer function. To solve the problem, a dynamic model of the Ćuk CCM inverter with a coupled inductor is developed and a repetitive controller (RC) coupled with feedback and feedforward controllers is applied to this inverter. A practical design guideline is also presented to select control parameters. Experimental results using a 200-W prototype demonstrate the acceptable performance of the proposed controller.

Design of linear and nonlinear controller for DC-DC boost converter with right-half plane zero

Design of linear and nonlinear controller for DC-DC boost converter with right-half plane zero

Design of linear and nonlinear controller for DC-DC boost converter with right-half plane zero

Design of linear and nonlinear controller for DC-DC boost converter with right-half plane zero

Impedance-Based Stability Evaluation for Multibus DC Microgrid Without Constraints on Subsystems

Multibus dc microgrids, which combine renewable energy sources, energy storage systems, and loads, have voltage stability requirement, which solicits increasing research attention in practice. Potentially complex architectures of the multibus dc microgrids make it difficult to evaluate the stability using the conventional stability criteria. In this article, some constraints related to the conventional stability criteria, such as right-half-plane (RHP) poles or zeros in the subsystems are discussed. Further, an impedance-based stability criterion is proposed in the light of generalized bode plots for multibus dc microgrids. The configuration of the multibus dc microgrid is simplified by adopting generalized voltage source, generalized current source, and two-port model. Then, impedances or admittances for each bus port can be derived, which are helpful for assessing the stability of the system. Using the proposed stability criterion, the stability of each bus port in the multibus dc microgrid can be evaluated separately. The proposed stability method considers the number of RHP pole of the open-loop transfer function for the system so the stability of the system consists of subsystems with RHP pole and zero can be analyzed correctly. Moreover, the intermittent bus converter connected with neighboring dc microgrid can be regarded as an extension unit. Then, the proposed method can be easily extended and is acting as a generalized approach for different configurations, i.e., single-bus dc mirogrid or a cluster of dc microgrids. Experiments are done to validate the effectiveness of the proposed criterion.

A novel control strategy for effects of Right-Half Plane Zero in three-phase voltage source rectifier

The linear model of the three-phase voltage source rectifier (VSR) proposed before could not provide an accurate description for the stability and dynamics performance when the output power is high, the inductances are large or the boost ratio is high. Hence, an item of Right-Half Plane Zero (RHPZ), which contains the output power, the inductances and the boost ratio, is introduced into the linear model in this paper, where its derivation and physical interpretation are also provided. After the introduction, the quantitative analysis for the RHPZ effects, including the decrease of the stability, the deterioration of the dynamic performance and the overshoot of the DC-link voltage, are provided in this paper. According to the analysis, a novel control strategy is proposed to enhance the stability to improve the dynamic performance and to restrain the voltage overshoot. Finally, simulation and experimental results verify that this control strategy has a great validity to reduce the RHPZ effects.