Half Plane Zeros Research Articles

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.

Various MPPT Modes and Dynamic Performance of Coupled Inductor Bipolar Multi-Output Converter With no Right Half Plane Zero

Various MPPT Modes and Dynamic Performance of Coupled Inductor Bipolar Multi-Output Converter With no Right Half Plane Zero

Reducing the Input Capacitance to Minimize the Right-Half-Plane Zero Effect for Buck Converters in Wireless Power Receiver Systems

Reducing the Input Capacitance to Minimize the Right-Half-Plane Zero Effect for Buck Converters in Wireless Power Receiver Systems

Research on High-Performance Multiphase DC–DC Converter Applied to Distributed Electric Propulsion Aircraft

The performance of power converter of electric propulsion aircraft (EPA), which should have high efficiency, high power density and high reliability, affects the volume, weight and efficiency of the whole electric aircraft (EA). This paper proposes a novel DC-DC converter with gallium nitride (GaN) transistors. Firstly, the working modes and main operation waveforms of the converter are analyzed. The new converter can achieve ZVS and ZCS through auxiliary soft switch branches. Compared with the traditional Buck-Boost converter, the soft switching capability of the proposed converter allows operation at very high frequency and has a higher efficiency. The multiphase interleaving magnetic integration technology is adopted to realize the modular design, which not only meets the requirements of high power and low ripple, but also eliminates right half-plane zero in boost mode, achieves high dynamic response and improves the power density. A novel parallel multiphase inverse coupled inductor (ICI) and a symmetrical array ICI are proposed, to allow a high-density and high-efficiency bidirectional DC-DC converter design for hybrid energy storage system of EPA. Finally, the proposed ICI prototype was compared with the state-of-the-art commercial ICI product, and the comprehensive performance of the converter was verified through steady-state, transient, efficiency and thermal experiments.

High Step-Up Gain Converter Based on Two-Phase Interleaved Coupled Inductor Without Right-Hand Plane Zero

This paper proposed a novel two-phase interleaved Coupled Inductor (CI) based high step-up gain converter without Right Half Plane (RHP) zeros for a wide operating range of duty cycle. A coupled inductor between input and output is used in the proposed converter to eliminate RHP zero. The energy of CI is transferred to output capacitor when switch is ON to eliminate RHP zero. Furthermore, the converter has a wide operating range to eliminate RHP zero with a coefficient coupling of CI near one. Thus, the converter achieves higher bandwidth and a wide range of control over output voltage. The small-signal model of proposed converter is derived to verify the proposed claim. The single loop voltage control is sufficient to regulate output voltage of the converter with a good stability margin and faster dynamic response for a wide range of load changes. In addition, proposed converter has a high voltage step-up gain and low voltage stress on switching devices compared to the boost converter. Moreover, interleaved operation at input side reduces ripple and increases power density. All theoretical findings are verified by simulation and 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.

Multi-Objective Optimisation-based Robust H∞ Controller Design Approach for a Multi-Level DC-DC Voltage Regulator

In case an analytical approach to the selection of any weighting function is not possible, the selection process is usually a random and time-consuming process. In robust H∞ control theory, the selection of scalar, time, or frequency-dependent weighting functions is the main issue to shape the amplitude-frequency characteristic curve of the feedback controller. Therefore, we propose a robust H∞ control approach which utilises the multi-objective grey wolf optimisation algorithm (MOGWO) to obtain the optimal performance weighting functions in the presence of right half-plane zeros and limited bandwidth constraints. A trade-off design flowchart is proposed, providing Pareto optimal solutions to choose the optimal configuration of the robust feedback controller. The control method is structured by combining the robust H∞ optimal technique and the multi-objective algorithm. The effectiveness of the approach is compared with the non-convex single-objective heuristic solutions like the multi-verse optimisation algorithm (MVO), whale optimisation algorithm (WOA), and grey wolf optimisation algorithm (GWO). The focus of this design is to track and stabilise the output voltage of the DC-DC converter in the presence of external disturbances and parameter uncertainties. The optimised controllers are implemented using a digital signal processor (DSP) on a 200 W interleaved boost converter. The simulation results and experimental findings show that the proposed control method provides supreme disturbance rejection along with maintaining the stability of the system.

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.

Fractional‐order filter‐based enhanced full state feedback control design with multi‐objective formulation using grey wolf optimization algorithm

AbstractA perturbed fractional‐order filter (FOF)‐based LQR control design with multiple performance indices is proposed in this paper. Three variants of the FOF‐based linear quadratic regulator (LQR) system have been proposed along with choices on the commensurate order of state feedback law. The multi‐objective problem formulation has been done with three performance objectives to address the different issues of design. The first performance index constitutes a weighted sum of ITAE (Integral Time of Absolute Error) and the difference between the eigenvalues of the plant and the LQR controlled plant, chosen to minimize the large oscillations as well as relative stability with respect to eigenvalues. A new lower bound of the singular values have been addressed to ensure the robust stability of the system through the formulation of a second performance objective. It is the minimization of singular values of the return ratio matrix at the plant's input. The third and the last performance index aims minimization of maximum singular values of the perturbation transfer function at the plant's output, so as to guarantee no closed‐loop right half plane zeros. The multi‐objective optimization problem is solved and the optimal solutions are obtained via Grey Wolf Optimization Algorithm. The simulation results validate the performance and effectiveness of the proposed control design.

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.

Ultra-High Step-Up Gain Interleaved Coupled Inductor DC–DC Converter with Reduced Voltage Stress and Eliminated Right Half Plane Zero

Ultra-High Step-Up Gain Interleaved Coupled Inductor DC–DC Converter with Reduced Voltage Stress and Eliminated Right Half Plane Zero

Indirect closed loop control of quasi-Z-source inverter for standalone solar PV-based energy conversion system

Nowadays impedance source inverter (ZSI) offers an attractive solution to renewable energy sources with low output, can buck/boost the output voltage by utilising shoot-through pulses. The presence of right half plane zero in control transfer function makes the closed loop control complex, an undershoot is visible in the capacitor voltage. This paper presents an indirect control method of peak dc link voltage for a quasi-Z-source (qZS) inverter connected system. Small signal model for dc and ac sides are elaborated, optimum parameters for impedance network and controller are designed by analysing various frequency and time responses. The control methodology uses a single loop PI controller at dc side, decoupled feed forward control at ac side and parasitic resistances are considered for dynamic analysis. Results depicts a fast reference tracking, without compromising stability, harmonic attenuation, and transient response. A stable controller response validates the presented design and control methodology.

Indirect closed loop control of quasi-Z-source inverter for standalone solar PV-based energy conversion system

Nowadays impedance source inverter (ZSI) offers an attractive solution to renewable energy sources with low output, can buck/boost the output voltage by utilising shoot-through pulses. The presence of right half plane zero in control transfer function makes the closed loop control complex, an undershoot is visible in the capacitor voltage. This paper presents an indirect control method of peak dc link voltage for a quasi-Z-source (qZS) inverter connected system. Small signal model for dc and ac sides are elaborated, optimum parameters for impedance network and controller are designed by analysing various frequency and time responses. The control methodology uses a single loop PI controller at dc side, decoupled feed forward control at ac side and parasitic resistances are considered for dynamic analysis. Results depicts a fast reference tracking, without compromising stability, harmonic attenuation, and transient response. A stable controller response validates the presented design and control methodology.

Improved Controller and Design Method for Grid-Connected Three-Phase Differential SEPIC Inverter

Single-ended primary-inductor converter (SEPIC) based differential inverters (SEPIC-BDI) have received wide concerns in renewable energy applications due to their modularity, galvanic isolation, decreased power stages, continuous input current, and step up/down capability. However, its design still has several challenges related to component design, the existence of complex right half plane (RHP) zeros, and increased sensitivity to component mismatches. In this context, this paper presents an improved control and enhanced design method for the three-phase SEPIC-BDI for grid-tied applications. A generalized static linearization approach (SLA) is proposed to mitigate the low-order harmonics. It practically simplifies the control complexity and decreases the required control loops and sensor circuits. The mismatch between the SEPIC converters in each phase is highly mitigated due to the independent operation of the SLA in each phase and the output dc offset currents are reduced. The proposed enhanced design methodology modifies the SEPIC open-loop transfer function by moving the complex RHP zeros to the left half-plane (LHP). Therefore, a simple proportional-integral (PI) controller effectively maintains converter stability without adding higher-order compensators in the literature. Moreover, a straightforward integrator in the control loop eliminates the negative sequence harmonic component (NSHC) and provides a low computational burden. Simulations and experimental results based on 200V, 1.6 kW, 50 kHz prototype with silicon carbide (SiC) devices are provided to validate the effectiveness of the proposed work. The results show that the proposed controller and design method achieve pure output current waveforms at various operating points of the inverter and dc voltage variations.

Wide Operating Range Minimum Phase Interleaved Hybrid Converter With Reduced Leakage Current

In order to minimize the common mode leakage current and capability to supply both dc and ac outputs simultaneously, a transformerless wide operating range minimum phase interleaved hybrid converter for photovoltaic applications is presented in this article. The proposed hybrid converter has wide operating ranges of duty ratio (D) and modulation index (M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> ), and can be operated at both the conditions, D + M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> ≥ 1 and D + M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> ≤ 1, which increases the dc gain and improves the ac output quality. Moreover, the proposed hybrid converter exhibits minimum phase behavior as the right half plane zero is eliminated, which enables simpler controller design and facilitates improved bandwidth with higher load current. A hybrid pulsewidth modulation technique is developed for the proposed hybrid converter to minimize the high-frequency common mode voltage terms of the parasitic capacitor and to regulate both the dc and ac outputs simultaneously. The performance of the proposed hybrid converter is compared with other similar topologies to bring out its advantages. Detailed mathematical modeling of the proposed hybrid converter is carried out and a 930-W laboratory prototype is developed to verify its performance.

On Determining of LTI Systems Having Nondecreasing Step Response

This brief mainly focuses on discussing computational method of determining whether step responses are nondecreasing for linear time invariant (LTI) systems, including negative real pole systems and complex pole systems. A modified theorem of Jayasuriya and Dharne and a useful fact are offered to deal with negative real pole systems which may have right half plane (RHP) zeros. A necessary condition is presented for complex pole systems to have non-decreasing step responses. Besides, an approximated method is further given as an improvement for determining step responses of complex pole systems.

A Minimum-Phase Dual Output Hybrid Converter for Standalone Hybrid AC/DC Supply Systems

A minimum-phase dual output hybrid converter for standalone hybrid ac/dc supply systems is proposed in this article. Due to its circuit arrangement, the converter eliminates the right half-plane zero from the control-to-dc output voltage transfer function (i.e., making the system minimum-phase) and gives simultaneous ac and dc outputs using single-stage power conversion. Due to the minimum-phase behavior, the converter is capable of operating at a high load current while maintaining closed-loop stability. Further, it enables simpler controller design and faster dynamic response. As it has two inductors, one at the main input voltage terminals and another at the output dc voltage terminals, it gives continuous input/output currents. Also, it gives step-down/step-up dc output voltages along with the step-down ac output voltage based on the duty ratio. It also has inherent shoot-through protection capability, which results in reliable power conversion on the occurrence of misgating of the switches caused by electromagnetic interference. A hybrid pulsewidth modulation scheme is developed to achieve simultaneous ac and dc outputs. Detailed mathematical modeling is carried out to demonstrate the properties of the converter, and its experimental validation is done through a laboratory prototype. Moreover, at different loading conditions, efficiencies of the converter are measured for varying dc load (having constant ac load) and varying ac load (having constant dc load), to show its effectiveness.

Model Predictive Control of Autonomous Delivery Robot with Non-minimum Phase Characteristic

This paper introduces the concept of motion planning of delivery robot in an autonomous driving mode using an inverted pendulum model that can effectively control disturbance. The inverted pendulum model exhibits the non-minimum phase characteristic caused by the right half-plane zero. An effective method of reducing this characteristic is examined. A motion platform with 3-degree-of-freedom motion and a touch sensor are installed on a wheeled omnidirectional mobile platform. A steel ball is placed on the touch sensor and controlled to be located at the center. As the autonomous delivery robot moves, the steel ball is subjected to various disturbances and goes off the center. The influence of disturbance can be predicted by measuring the distance the steel ball moves away from the center. In this paper, linear quadratic regulator, preview control, and model predictive control are applied to the inverted pendulum model for motion planning, and thus the reduction of the non-minimum phase characteristic can be comparatively analyzed via simulation. The decrease in the disturbance is experimentally compared according to motion planning. Consequently, this paper proposes an effective motion planning method for an autonomous delivery robot with non-minimum phase characteristic.

Minimum phase bipolar converter for DC microgrid applications

This study proposes a minimum phase bipolar converter for dc microgrid applications, which is derived from the combination of C'uk and Sepic converters with some modifications in both of them in order to get a minimum phase system. In the proposed bipolar converter (PBC), the equivalent series resistance of transfer capacitors of both C'uk and Sepic converters is increased by adding resistances and introducing magnetic coupling between the filter inductors of the Sepic converter with a series RC network. These circuit modifications eliminate right half plane zero from the PBC and thereby make it a minimum phase, unlike the conventional C'uk-Sepic bipolar converter. Due to the minimum phase behaviour, the proposed converter can deliver high load current, achieves high bandwidth and facilitates simpler controller design in contrast to the conventional C'uk-Sepic bipolar converter. Detailed steady state and dynamic modelling of the PBC has been carried out in order to show its advantages. A 500 W laboratory prototype has been developed and implemented using field programmable gate array-based system to verify the operation of the proposed converter.

Internal Model Control Design Based on Equal Order Fractional Butterworth Filter for Multivariable Systems

An internal model control with inverted decoupling (ID-IMC) controller design method based on equal fractional Butterworth (EFBW) filter is proposed for Multiple Input-Multiple Output (MIMO) systems with multiple time delays and Right Half Plane (RHP) zeros. There has been finite memory and limited flexibility for multivariable processes developed using a direct ID-IMC method. This paper presents a novel procedure to approximate Butterworth (BW) filters using fractional-order (FO) theories, so that the degree-of-freedom for tunable parameters is increased. The proposed ID-IMC controller cascaded with EFBW filter combines the computational simplicity of the ID-IMC structure with the greater flexibility of the EFBW filter, in conjunction with a better set-point tracking and disturbance rejection performance. Further, the stability analysis of the designed controller is given to ensure the stability of the closed-loop system. Dynamic performance indicators and sensitivity functions are carried out for the time domain and robustness analysis. Two illustrative examples are presented to show the merits of the proposed method.