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Abstract Regulation of DC‐bus voltages is important for the stable operation of different applications, like microgrids and electric vehicles, and it is usually performed by charging/discharging (C/D) batteries. Such C/D system is formed by a power converter and a control system, and it is aimed at guaranteeing the system stability and extending the battery life. To extend the battery life, it is important to reduce the battery current ripples, which is usually performed with interleaved converters and nonlinear controllers; however, most of those controllers do not provide the design procedure nor guarantee the system stability. This paper proposes a nonlinear control strategy to regulate the voltage in a DC‐bus by C/D a battery through a two‐branch interleaved Boost converter. The proposed control strategy is formed by two sliding mode controllers (SMCs), where the first one regulates the DC‐bus voltage by acting on the first converter branch and the second SMC controls the current in the second branch. The reference of the second SMC is generated from the delayed current of the first branch, in order to coordinate the controllers and to reduce the ripples in the battery current. The paper includes a procedure to design the two SMCs as well as simulation and experimental results to validate the proposed solution and to illustrate its performance. The results prove the system stability and its dynamic performance according to the design.

There exists torque ripple in the commutation process of brushless DC motor (BLDCM), which seriously restricts its application in the high-performance field. This paper proposes an auxiliary step-up circuit to suppress the commutation torque ripple of BLDCM, and the auxiliary step-up circuit consists of a transformer, a capacitor and a switch circuit. For effective suppression of the commutation torque ripple, the capacitor is charged in the non-commutation period. When the commutation occurs, the charged capacitor is added on the power source through a switch circuit to step up the dc-bus voltage in the commutation period, and the three-phase inverter is regulated to make the motor's input voltage is equal to four times the back electromotive force (back EMF) amplitude. The auxiliary step-up circuit only transfers partial power required in the commutation process of the motor, and the capacity of the power components is reduced accordingly. The inductive energy stored in the transformer is returned to the power source in each switching cycle, which improves the energy utilization rate. In addition, this method can also shorten the commutation time. The validity and effectiveness of the proposed method is verified through experimental results.

Summary: This work proposes a 3‐phase 4‐wire unified power quality conditioner (UPQC) structure, which has ability to operate with per‐phase independent grid current control, reduced dc‐bus voltage and inverted/dual compensation strategy. Since the grid currents are controlled by the series converter, two distinct strategies, namely, independent current compensation strategy (ICCS) and load unbalance compensation strategy (LUnCS) can be employed. Using the ICCS, the controls of the grid currents are performed independently per‐phase, such that the UPQC can operate even when grid voltage outage occurs in one or two phases of the power source. Furthermore, to guarantee the proper parallel converter operation, the dc‐bus voltage amplitude must be higher than the grid voltage peak amplitude. Thus, since the parallel converter operation is assured, the functioning of the series converter is also guaranteed because it needs lower dc‐bus amplitude to operate. However, depending on the converter topology adopted in the parallel converter, the series converter could be subjected to operate with dc‐bus voltage higher than necessary. Thus, to minimize this aspect, this paper proposes a UPQC scheme composed of 3‐Leg split‐capacitor (3‐Leg‐SC) and 4‐Leg topologies, operating as series and parallel converters, respectively. Thus, besides the use of the ICCS, lower dc‐bus voltage is allowed when compared to the UPQC composed of two 3‐Leg‐SC converters, as well as reduced power switches number is achieved when the propose scheme is compared to UPQC composed of two 4‐Leg converters. Extended experimental results based on digital signal controller are presented to evaluate the effectiveness and performance of the proposed UPQC. [ABSTRACT FROM AUTHOR]

Regulation of DC‐bus voltages is important for the stable operation of different applications, like microgrids and electric vehicles, and it is usually performed by charging/discharging (C/D) batteries. Such C/D system is formed by a power converter and a control system, and it is aimed at guaranteeing the system stability and extending the battery life. To extend the battery life, it is important to reduce the battery current ripples, which is usually performed with interleaved converters and nonlinear controllers; however, most of those controllers do not provide the design procedure nor guarantee the system stability. This paper proposes a nonlinear control strategy to regulate the voltage in a DC‐bus by C/D a battery through a two‐branch interleaved Boost converter. The proposed control strategy is formed by two sliding mode controllers (SMCs), where the first one regulates the DC‐bus voltage by acting on the first converter branch and the second SMC controls the current in the second branch. The reference of the second SMC is generated from the delayed current of the first branch, in order to coordinate the controllers and to reduce the ripples in the battery current. The paper includes a procedure to design the two SMCs as well as simulation and experimental results to validate the proposed solution and to illustrate its performance. The results prove the system stability and its dynamic performance according to the design. [ABSTRACT FROM AUTHOR]

In the context of future permanent magnet synchronous machines (PMSMs) with a high number of phases (>7) in integrated drives, this study proposes several control strategies when multiphase PMSMs with non‐sinusoidal back electromotive forces (back‐EMFs) operate in healthy and open‐circuit faults. In all operation modes, the considered constraint on current is related to the maximum root mean square current allowable in one phase of the machine. The constraint on voltage limits the maximum peak value of the phase voltage determined by the DC‐bus voltage of the converter. When one or two phases are open‐circuited, to maximise torque and respect the constraints, new current references obtained by several proposed methods in rotating and natural frames are imposed to the machine. Owing to the non‐sinusoidal waveform of back‐EMFs and the considered constraints, numerical computations based on analytical formulations are required to obtain maximal torque‐speed characteristics, including the flux‐weakening operation. The usefulness of the proposed strategies is verified by numerical and experimental results. [ABSTRACT FROM AUTHOR]

Due to their nonlinearity, hybrid renewable power systems (HRPSs) are more complex in terms of their modeling, power management and control. In this context, this paper focuses on optimizing the functionality of a stand-alone HRPS through the optimization of the input/output scaling gains of the fuzzy sliding-mode controllers. This optimization is based on a new evolutionary optimization algorithm called water cycle algorithm (WCA). In fact, in this work the introduction of WCA in renewable energy optimization systems is proposed for the first time. Furthermore, depending on the HRPS operating modes, two fitness functions are proposed: the photovoltaic-generated energy, which must be maximized, and the error between the measured DC-bus voltage and its reference, which should be minimized. The stand-alone HRPS is composed of a photovoltaic generator as a main source, a fuel cell and batteries as auxiliary sources. For the verification process, simulations have been conducted under MATLAB/Simulink/SimPower Environment. The obtained results reflect the effectiveness of our proposed technique. [ABSTRACT FROM AUTHOR]

The aim of present study is to develop a 'Luo' converter‐based low‐cost solar powered water pumping scheme utilising a switched reluctance motor (SRM). The speed of SRM drive is controlled by adjusting the DC‐bus voltage of split‐capacitor converter. The converter is electronically commutated at fundamental frequency for low switching losses. A 'Luo' DC–DC converter working in continuous inductor current and capacitor voltage modes (continuous inductor current mode and continuous capacitor voltage mode) is utilised to feed power to SRM drive through a split‐capacitor converter. It also provides the limitless sector of maximum power point tracking (MPPT). The elimination of current and voltage sensors on the motor side owing to variable speed operation of the motor drive makes the system cost‐effective and reliable. The soft‐starting of SRM drive is also achieved through the proper step size and initial duty cycle selection through MPPT algorithm. The performance of SRM system is validated by both Simulink/MATLAB platform‐based model and responses of developed prototype. [ABSTRACT FROM AUTHOR]

This paper presents implementation of distribution static compensator (DSTATCOM) using kernel incremental metalearning algorithm (KIMEL) control algorithm. It demonstrates the functions of DSTATCOM such as reactive power compensation, harmonics elimination, and load balancing under linear and nonlinear loads with its self-supporting dc-bus voltage. The proposed control algorithm based on KIMEL is applied for extraction of fundamental active and reactive power components of load currents that are required for estimation of reference supply currents. These reference supply currents are used for gating pulses generation using indirect current control principle. A DSTATCOM with features of self-supporting dc bus (capacitor) is developed using DSP (dSPACE-1104), and the response of proposed control algorithm is studied under various operating conditions and found satisfactory. [ABSTRACT FROM AUTHOR]

This paper deals with a power factor correction (PFC)-based Cuk converter-fed brushless dc motor (BLDC) drive as a cost-effective solution for low-power applications. The speed of the BLDC motor is controlled by varying the dc-bus voltage of a voltage source inverter (VSI) which uses a low frequency switching of VSI (electronic commutation of the BLDC motor) for low switching losses. A diode bridge rectifier followed by a Cuk converter working in a discontinuous conduction mode (DCM) is used for control of dc-link voltage with unity power factor at ac mains. Performance of the PFC Cuk converter is evaluated under four different operating conditions of discontinuous and continuous conduction modes (CCM) and a comparison is made to select a best suited mode of operation. The performance of the proposed system is simulated in a MATLAB/Simulink environment and a hardware prototype of the proposed drive is developed to validate its performance over a wide range of speed with unity power factor at ac mains. [ABSTRACT FROM AUTHOR]

In this paper, a new integrated three-level ac-dc converter is presented. The proposed converter integrates the operation of the boost power factor correction and the three-level dc-dc converter. The converter is made to operate with two independent controllers-an input controller that performs power factor correction and regulates the dc bus and an output controller that regulates the output voltage. The input controller prevents the dc-bus voltage from becoming excessive while still allowing a single-stage converter topology to be used. The paper explains the operation of the new converter in detail and discusses its features and a procedure for its proper design. Experimental results obtained from a prototype are presented to confirm the feasibility of the new converter. [ABSTRACT FROM AUTHOR]

Static Synchronous Compensator (STATCOM) regulates the voltage and corrects the power factor at the point of common coupling (PCC) by injecting reactive power. Also, this device plays a vital role as a stability aid for small and large transient disturbances in an interconnected power system. This work deals only with power-factor correction which means STATCOM in Var compensation mode. PI controller is very common in the control of various systems including STATCOM. However, one disadvantage of this conventional controller is its inability to still working well under a wider range of operating conditions. So, as a solution fuzzy controller is proposed in literature. But, the main problem with the conventional fuzzy controllers is that the parameters associated with the membership functions and the rules depend broadly on the intuition of the experts. To overcome this problem, this paper investigates the application of Adaptive Neuro-Fuzzy Inference System (ANFIS) approach to design a fuzzy controller for controlling the DC capacitor voltage under steady and transient condition. The simulation results using MATLAB/SIMULINK have proved that the proposed design method gives reliable powerful fuzzy controller with a minimum number of membership functions and has very good characteristics such as: fast dynamic response, high accuracy of tracking the DC-voltage reference, and strong robustness to load parameters variation. [ABSTRACT FROM AUTHOR]

The modularized subunit of an electronic power transformer (EPT) is a series connection of two H-bridge voltage-source converters and a DC-DC converter with a high-frequency isolation transformer (HFIT). On the basis of cascading and paralleling the modularized subunits, EPT can be used in high-voltage and large-current applications in the power system. This paper discusses the steady state analysis of the modularized subunit of EPT. Theoretical analysis considers the influences of the two H-bridge voltage-source converters on the two sides of the DC-DC converter. We deduce the formulas of the theoretical calculation on the internal electrical characteristics of EPT (e.g., the voltages of the DC-bus capacitor and the primary side peak current of the HFIT). This paper provides guidance on the design and selection of EPT key elements (e.g., the DC-bus capacitors and HFIT). Experimental results are obtained from a single subunit of a laboratory model rated at 962 V, 15 kVA. All calculations, simulations, and experiments confirm the theoretical analysis of the subunit of EPT. [ABSTRACT FROM AUTHOR]

Installation of many distributed generations (DGs) could be detrimental to the power quality of utility grids. Microgrids facilitate effortless installation of DGs in conventional power systems. In recent years, dc microgrids have gained popularity because dc output sources such as photovoltaic systems, fuel cells, and batteries can be interconnected without ac/dc conversion, which contributes to total system efficiency. Moreover, high-quality power can be supplied continuously when voltage sags or blackouts occur in utility grids. We had already proposed a “low-voltage bipolar-type dc microgrid” and described its configuration, operation, and control scheme, through experiments. In the experiments, we used one energy storage unit with a dc/dc converter to maintain the dc-bus voltage under intentional islanding operation. However, dc microgrids should have two or more energy storage units for system redundancy. Therefore, we modified the system by adding another energy storage unit to our experimental system. Several kinds of droop controls have been proposed for parallel operations, some of which were applied for ac or dc microgrids. If a gain-scheduling control scheme is adopted to share the storage unit outputs, the storage energy would become unbalanced. This paper therefore presents a new voltage control that combines fuzzy control with gain-scheduling techniques to accomplish both power sharing and energy management. The experimental results show that the dc distribution voltages were within 340 V ± 5%, and the ratios of the stored energy were approximately equal, which implies that dc voltage regulation and stored energy balancing control can be realized simultaneously. [ABSTRACT FROM AUTHOR]

This paper presents an embedded energy share method between the high energy storage system (battery) and the auxiliary energy storage system such as supercapacitors (SC). Using the SC and battery with a good strategy for energy management improves the performance of hybrid electric vehicles (HEVs). The SC modules are dimensioned for peak power requirement, and the battery's module ensures the average power of HEVs. The battery module is connected to dc-bus through a dc/dc converter for the first topology and without a converter for the second configuration. Buck-boost converters are used between the SC and the dc-bus to manage the available energy for all topologies. The originality of this paper stems from its focus on the control methods of the dc-bus voltage and currents, which use adjustable polynomial controllers (correctors based on polynomial approach). These methods are implemented in the PIC18F4431 microcontroller which ensures analog to digital conversion, and the pulsewidth modulation signals generation for dc/dc converters. Due to cost and available components, such as the power semiconductors (IGBT) and the battery, the experimental tests benches are carried out in reduced scale. Through some simulations and experimental results, the performance of the proposed control is shown and analyzed. [ABSTRACT FROM AUTHOR]