The quest for energy conservation is a thought-provoking conundrum to researchers. Time to time they contributed towards this pursuit. In the 19th century, it was a fascinating idea about electric vehicles (EVs). As most of the developing countries depend on conventional energy sources, integration of EVs with renewable energy sources justified the cause. The parking slots became transformed into unlimited sources of clean energy. For the comfort of charging and better energy management, wireless power transfer technology was introduced to the charging station. As a fulfilment of the technology, the vehicle-to-grid (V2G) integration was implemented. It helped the bi-directional power flow between the vehicle and the grid with renewable energy. This study presents an extensive review of the renewable energy powered wireless charging and V2G integration of EVs. Various topologies are discussed with mathematical explanations and block diagrams. Concepts are validated with PSIM simulations.

This study presents a high step-up switched Z-source inverter. Only by using one more inductor and capacitor in comparison with switched boost inverter, the presented inverter reaches various advantages such as including high boost factor, reduced range of duty cycle and continuous input current. These features make it suitable to use in different applications such as photovoltaic system to increase the voltage level. In this study, a comprehensive analysis of the presented inverter in shoot through (ST) and non-ST operation modes are given. This study also elaborates an appropriate switching pattern for the proposed inverter. There is also a comprehensive comparison and cost evaluation of the proposed structure with conventional structures. Cost and power efficiency comparisons are evaluated by the design considerations of ZSIs in the same condition. Finally, in order to reconfirm the analyses, the experimental results of the laboratory prototype are presented.

Here, the authors study open-circuit faults (OCFs) in the power switches of multilevel converters with a model-based perspective. In specific, the authors address single-phase cascaded H-bridge (CHB) converters with n-levels in its output voltage (CHB-n L), which are designed as shunt active power filters. In this task, the OCFs are modelled by fault profiles with an additive structure in each subsystem of the CHB-n L converter. These additive fault profiles have constant and oscillatory components, where the constant term sign indicates the pair of damaged switches in the H-bridge. Hence, a sliding-mode integral observer is proposed to estimate the constant terms of the fault profiles. The complexity of the observer depends on the number of H-bridges in the CHB-n L converter. As a result, the proposed fault detection and isolation (FDI) scheme relies on the estimated constant terms of the additive fault profiles to achieve a robust and fast diagnosis stage. The proposed model-based FDI scheme is validated experimentally under single and multiple fault scenarios, and model uncertainty. During the evaluation, the derived methodology only requires less than one cycle of the fundamental frequency to isolate the faults, and show robustness to load changes and parametric uncertainty.

Fault-tolerant capability greatly promoted the application of multiphase machines on safety-critical occasions, and fault-tolerant control strategies are required to suppress the torque ripples. Based on the generalised symmetrical components (SCs) theory, a general expression of the independent SCs is derived during the fault-tolerant operation of symmetrical multiphase machines in this study, and coefficients of the four basic rotating components in the general expressions are calculated for specific open-circuit conditions. Then the bidirectional rotating proportional–integral controllers are designed to control all the rotating components in each SC. Considering control loops for all the independent SCs, an enhanced rotor field-oriented control fault-tolerant strategy is proposed for symmetrical multiphase induction machines (IMs) with any phase number m. Furthermore, additional rotating current controllers in the first SC control loop are added to reduce the low-order current harmonics during the fault-tolerant operation. Experimental evaluations in terms of the transient, dynamic and harmonic performances on both five-phase and nine-phase IM drive platforms are provided to verify the effectiveness of the proposed fault-tolerant strategy.

Practically, power electronic circuits (PECs) generate electromagnetic interference (EMI) which influence the operation of electronic equipment and may create instabilities. PECs must comply with electromagnetic compatibility standards for stable periodic operation but indeed fail under certain conditions. This study reports the effect of conducted EMI in a current mode controlled higher-order DC–DC converter fed from a pulsating DC voltage instead of a stiff DC voltage. The converter is found to be a source of conducted EMI under light loading conditions adversely affecting the systems’ stability. A non-feedback control technique is implemented to mitigate the instabilities caused by EMI and to make the system electromagneticaly compatible. A mathematical model is developed to describe the dynamics involved. Simulation and experimental results are presented to support the analyses documented.

In this paper, a near-state pulse-width modulation (NSPWM) algorithm is proposed and implemented on dual-two-level voltage-source inverters (D2L-VSIs) in order to reduce the common-mode voltage (CMV), the inverter switching losses, the current total harmonic distortion, and the side effects of bearing currents --compared with space vector modulation (SVM) and PWM7. To gain these goals, two conventional two-level inverters of the D2L-VSI are controlled, separately, with specific switching sequences and an adjusted phase difference between the carriers of two inverters. For evaluating and comparing these PWM techniques mathematically, both CMV root mean square generated and switching losses of the D2L-VSI are formulated as a function of the power factor of the D2L-VSI, which is driven by the methods detailed in this study. Eventually, theories and analysis, as well as simulations and experimental results --which are generated by MATLAB/Simulink environment and a 300 W scaled-down D2LVSI prototype, respectively --authenticate the superiority of the proposed NSPWM over both SVM and PWM7.

This study proposes a sliding mode observer (SMO) based method for sensorless speed control of surface permanent magnet synchronous motor equipped with LC filter. To deal with side effects of pulse width modulation technique, LC filters are equipped between inverters and motors in some industrial applications. Therefore, filter input currents rather than stator currents will be measured by current sensors on the inverter board. Sensorless operation becomes complicated due to the differences between filter input and stator currents. When only inverter-side current sensors are installed, the mathematical model of the LC filter should be considered. Hereby, the proposed SMO takes the LC filter into consideration, so additional measurement of stator currents is not necessary. Back electromotive forces of the PMSM are estimated by the SMO, and the rotor speed and position are calculated by the phase locked loop. The proposed approach features simplicity, and it is suitable for medium- and high-speed ranges. Simulation and experimental results confirm the effectiveness of the proposed method.

Diode and thyristor-based rectifier circuits have been widely used in the industry. Due to non-linear structures of these circuits, they draw non-sinusoidal current from AC network as well as cause a low power factor in the AC side. The DC-link voltage of rectifier is affected by the changes in AC network or by the load variations on the DC side. Pulse-width modulated (PWM) rectifiers can eliminate the mentioned power quality problems if they control properly. This study proposes a controller with an adaptive and robust structure based on proportional + derivative type-2 fuzzy neural network (PD-T2FNN) for DC-link voltage control of PWM rectifier. Dynamic performance of PWM rectifier using the proposed controller is evaluated via dSPACE based experimental setup under different operation conditions: set-point change, step load change in the DC side of the rectifier, set-point change under load and capacitive operation mode. The experimental results are given for traditional PD and proportional + integral and T2FNN controllers to validity performance of the proposed controller. Performances of controllers are evaluated regarding settling time, overshoot, steady-state error and total harmonic distortion. PWM rectifier with PD-T2FNN DC-link voltage controller has superior performance for all operating conditions according to performance criteria when compared with other controllers.

This study aims to provide a comparison between several maximum power point tracking (MPPT) algorithms for PV system under severe weather conditions. Two MPPT hybrid algorithms are proposed, namely (a) hybrid combination of fuzzy logic controller (FLC) and the incremental conductance (IC) and (b) MPPT controller integrates FLC and perturb and observe (P&O) method. The two developed hybrid algorithms combined the strength of both P&O, IC with FLC in single framework. MATLAB/Simulink is used to investigate the response of both algorithms. Several weather conditions are simulated: (i) uniform irradiation, (ii) sudden changing, and (iii) partial shading. Under partial shading on PV panel, multi-peaks appear in power–voltage characteristics of the panel. Simulation results showed that ability of FLC to track MPP degrade significantly when testing at weather conditions far from those used for training. Finally, the proposed hybrid algorithms successfully eliminate the previous limitations associated with FLC, IC, and P&O algorithms individually with efficiency exceeds 97%.

Switching Table-based Direct Power Control (ST-DPC) is one of the most widely used techniques in Active Front-End (AFE) rectifiers. Proper control of switching states of the power converter is essential to obtain better power quality performance and quicker response to the load demand. In the classical ST-DPC techniques such as Virtual Flux with Noguchi's Table-based DPC (VF-NT-DPC) and Virtual Flux with Improved Table-based DPC (VF-IT-DPC) etc., these switching states are decided based on a predefined static switching table. Hence, they have poor power quality and dynamic performance with load variations. In this research work, in-depth mathematical analysis is carried out based on the quantised values of ‘the rate of change of active and reactive powers’ and an algorithm is introduced for AFEs. Since, the proposed algorithm is considering the quantised values of ‘the rate of change of active and reactive powers’, which is dynamic in nature; therefore, it has reduced THD, lesser power ripple, and quicker response than classical ST-DPC techniques. To show the superiority of the Algorithm based DPC (A-DPC) technique experimental work is carried out and the power quality performance of the proposed A-DPC is compared with conventional ST-DPC techniques VF-NT-DPC and VF-IT-DPC.

The Y-source inverter uses different turns ratios of a coupled inductor and a controllable duty ratio to vary its gain. However, its input current is discontinuous, and any leakage inductances of its coupled inductor will lead to unintentional dc-link voltage spikes and gain reduction. To solve these problems, an extended quasi-Y-source inverter has been proposed in this study, which compared with the Y-source inverter, uses an extra inductor and an extra capacitor. Although the extras may not appear attractive, they have successfully helped with the suppression of leakage effects, which decrease the voltage spikes, and hence permit the main magnetic core size to be much smaller. Concurrently, the continuous input current can be also achieved. Besides, inrush current at startup has been reduced to a more acceptable value, which together with other features of the proposed inverter, have been proven through experiments.

This study proposes a step-wise design procedure for development of a single-phase multilevel inverter topology. It is started with a module consisting of a single switch and single source. The number of switches and sources is gradually added in the module to increase the number of levels and quality of the output voltage. Each step is theoretically analysed and experimentally verified. These developed modules are used as a part of the inverter to get the bipolar load voltage with or without H-bridge. Each developed inverter topology differs from each other depending on the number of switches, sources and configuration of sources involved in the structure. The use of inverters, with cascaded modules, can be extended for medium-to-high-power applications. The theoretical analysis of one of the developed topology is explained and simulated in MATLAB/Simulink environment. Its performance is compared with some of the existing topologies to show the difference. The hardware setup is built in the laboratory for practical validation of the proposed topology. The nearest level control modulation scheme is used in both simulation and experimentation.

This study proposes a modified double-switch flyback-forward (DSFF) converter for low-power applications with a reduced number of windings in its transformer. This circuit has resulted from the combination of the two-switch flyback and two-switch forward converters. It includes a simple transformer with one set of secondary side windings, and it is not necessary to design two separate sets of windings for the desired output voltage which is the main problem of other flyback-forward converters. An auxiliary winding has been designed for self-biasing, and consequently, it improves the overall efficiency in the no-load condition. Due to the modifications on the previously presented two-switch flyback-forward converter, the circuit model has changed. This study, first, analyses the operation of the proposed converter in detail, then it explains a method to design this converter in continuous inductor current mode. Also, a start-up voltage regulator circuit and a modified bootstrap gate driver will be investigated, and the DC and AC model of the converter will be presented. Experimental results validate the proposed DSFF converter. The tested circuit includes a DSFF converter, a pulse generator circuit, a start-up voltage regulator, and a modified bootstrap gate driver.

Pulse forming networks and Marx generators are the classical rectangular waveform pulse generators (PGs). They are inflexible and their capacitors must be fully charged to the required voltage from 0 V before delivering each high-voltage (HV) pulse. They are only able to generate unipolar pulses; if bipolar pulses are sought another generator fed from a negative supply voltage is added. Recently, several power electronics based PGs have been proposed. This study presents an HV power electronics based PG, which is based on half-bridge modular multilevel converter (MMC) sub-modules (SMs) charged sequentially in a voltage-boost mode. Each SM capacitor and main switch form a boost converter with the charging input supply and inductor. As a result, all SM capacitors are charged to a voltage greater than the input. During the discharging process, the SM capacitors are connected in series, producing a rectangular HV pulse across the load. The proposed charging method allows a reduction in the converter footprint in comparison with recently proposed MMC sequentially charged PG topologies. Although only rectangular pulse waveforms are sought in this study, an SM-capacitor voltage balance method allows multilevel pulse generation. The viability of the proposed converter is confirmed by MATLAB/Simulink simulation and scaled-down experimentation.

Photovoltaic (PV) systems, especially which are installed in the remote areas, stand in need for a highly reliable system. A high failure rate of the semiconductor switches and capacitors yields a very low reliability of the inverters used in the PV system. Conventional two-level inverters are replaced by multilevel inverters (MLIs) to effectively improve the output quality waveform. However, MLIs incorporate a high device count in their architecture which further impairs the reliability of the PV system. Recent research has focused on developing fault-tolerant MLI topologies with reduced device count. However, the number of active devices and power losses, factors which are many of the times overlooked, are key in determining the reliability of the inverter. Here, the reliability of a novel fault-tolerant MLI topology is evaluated bearing in mind the effect of power losses on the junction temperature. Equal (or best) voltage source utilisation characteristics help in maintaining the uniform charge of the batteries. The concept of reliability is evaluated mathematically. The fault tolerance and even source utilisation of the proposed topology is verified through the obtained experimental results.

Single-switch multi-output light emitting diode (LED) drivers derived from Cuk, Sepic and Zeta converter are proposed and analysed. The proposed multi-output LED drivers can achieve balanced output current of each LED string by charge balance of storage capacitor without auxiliary current balancing circuit. Therefore, if only the output current of one LED string is controlled to the required level, the output currents of other LED strings will be regulated to the same level naturally, which will greatly simplify the control loop, especially when the number of LED string is numerous. The proposed LED drivers use only one active switch, which decreases the volume of circuit and simplifies the control loop. Finally, a 76 W prototype is built to verify the studied results.

This paper presents a battery-integrated multi-input step-up DC–DC converter (BI-MISUC) as a unified interface for multiple energy sources in the frame of a sustainable hybrid energy supply. The proposed converter comprises one bidirectional port for a battery and several unidirectional input power ports. Battery can be charged by input sources, discharged into load or bypassed while charging/discharging durations are independent of switching duty ratios for input sources. In the presented BI-MISUC, higher voltage gains with lower duty ratios are achieved not only by increasing the number of inputs but also using the switched inductor (SI) modules. It therefore enables BI-MISUC to be used for a wide range of applications from low to high voltage/power. Furthermore, input sources can be operated individually or simultaneously to supply load energy at the desired output voltage. The converter operation is described for three scenarios (i.e. no battery, battery charging and discharging). A linear quadratic regulator (LQR) control is also used to regulate the output voltage and output power of input sources at the desired references for different scenarios. Finally, the performance of the BI-MISUC is validated by simulations and experimental results.

In this study, two high voltage gain active Z-source dc/dc converters are proposed, which are suitable for renewable energy applications. The complete analyses of the proposed structures are presented and the suitable control method is proposed. The voltage and current stresses of all elements are calculated. Moreover, in order to recognise the advantages and disadvantages of the proposed converters, a comprehensive comparison between the proposed dc/dc Z-source converters with conventional converters are made. The efficiency of both proposed converters and the conventional ones are also compared. In addition, the application of the proposed topologies in fuel cell vehicle is proposed. Finally, in order to verify the theoretical analyses, simulation results in PSCAD/EMTDS software and experimental results of the prototype are presented.

In order to reduce the switching losses and improve the converter efficiency, the switching frequency of the semiconductor devices is usually kept low. However, the low switching frequency operation could lead to a severe harmonic distortion in the stator current and an undesirable modulation delay, which also affect the current control performance. Here, a stator current harmonic elimination control scheme has been studied for the electrically excited synchronous motor (EESM). First, extracting the stator current amplitudes of the fundamental and harmonic components by the sliding discrete Fourier transform (SDFT) algorithm. Then, these obtained current amplitudes will be taken as a part of the cost function for the current model predictive control strategy along with the switching losses and neutral point potential issues. For the further algorithm simplification and performance improvement, a reduced-order processing has been also introduced to realise a simple digital implementation. Finally, simulation and experiments demonstrate that this kind of stator current control could realise a similar characteristic with the selective harmonic elimination along with an online implementation and nice dynamic performance.

This study presents an open-circuit fault diagnosis method for a fault-tolerant three-level neutral-point-clamped static synchronous compensator (STATCOM). Since STATCOM only outputs reactive current, misdiagnosis may occur by utilising conventional methods. The proposed method relies on the measurement of three-phase currents and is able to identify the faulty switch within 10 ms. The diagnosis method uses the residuals of three-phase currents to detect the faults and locate the faulty switch pair. In addition, the root-mean-square value of the faulty phase current for a quarter of the current period is used to identify the faulty switch. Only the sensors that already exist in the system are required for the diagnosis method, which avoids the use of additional hardware circuits. Experimental results demonstrate the effectiveness and robustness of the proposed fault diagnosis strategy.

In this study, a new control method dedicated to modular multilevel converters (MMCs) is proposed. The approach is based on local communication between the individual controls of each submodule (SM). The local values of the capacitor voltages and the carrier-phase angles are shared between immediate neighbours achieving balancing of their capacitor voltages, and an automatic interleaving of the pulse-width modulation (PWM) signals. Using an inter-cell communication strategy, the number of required data exchanges with a centralised controller is greatly reduced. This method works for any number of SMs present in the converter and provides an integrated dynamic reconfiguration capability to enable or disable SMs during operation, without any additional consideration for the control-algorithm's implementation. Such a capability is not offered by classical MMC control methods using either PWM or nearest-level control strategies. Higher stability, robustness and larger bandwidth of the proposed method are first demonstrated through real-time simulation. The auto-interleaving of the PWM carriers and the capacitor-voltage balancing, provide fast responses and adequate accuracy. Experimental results are provided using a 600 V/3 kW/18 cells single-phase MMC demonstrator confirming the simulation results, and the advantages of this SM control strategy.

Self-excited induction generator (SEIG)-based wind energy conversion systems (WECS) are very popular for supplying stand-alone loads at remote sites. The SEIG needs adjustable VAR to regulate its terminal voltage and frequency. Usually, a combination of a static compensator (STATCOM) and a fixed capacitor bank is used to meet this VAR demand. Here, a state feedback-based control scheme is proposed to achieve independent control of the STATCOM DC-link voltage and the SEIG terminal voltage. Further, to ensure harmonic-free voltage at the SEIG terminal while supplying non-linear three-phase or single-phase loads, a harmonic compensation technique is also developed. The wind turbine pitch angle control is utilised to regulate the frequency of the SEIG terminal voltage. The combined action of the proposed voltage control and pitch control strategies ensures that the load voltage and frequency are maintained at their respective rated values with very low harmonic distortion irrespective of variation in the wind speed and load demand. The performance of the proposed controllers (in terms of transient load voltage and frequency deviations and load voltage total harmonic distortion), as verified on a laboratory prototype, are found to be superior to that of similar controllers proposed in the literature.

This study presents a single-stage grid-tied three-level neutral point clamped photovoltaic inverter with a centralised model-predictive decoupled active–reactive power control. The proposed centralised model predictive control (CMPC) incorporates the constraints of maximum power extraction, dc-link capacitor voltage balancing and active–reactive power tracking in a single objective function. The dc-link voltage of the inverter is regulated to its reference for extracting the maximum power. In order to eliminate the impact of reactive power exchange on floating dc-link voltage regulation, a decoupled active–reactive power control is used in the CMPC. Furthermore, a preference selective index-based dynamic weighting factor selection approach is introduced to maintain the relative importance between the power tracking and dc-link capacitor voltage balancing. The proposed control approach eliminates the outer dc-link voltage control loop and also, the empirical approach required for the selection of weighting factors. As a result, it ensures an optimal control action in each sampling period to improve the steady-state and dynamic tracking performance of the control objectives. The proposed control approach is experimentally verified by using a 1.2 kW laboratory-scale prototype and the results are presented to demonstrate its effectiveness compared to the classical proportional–integral-based model predictive control.

This work focuses on the accurate identification of lithium-ion battery's non-linear parameters by using an iterative learning method. First, the second-order resistance-capacitance model and its regression form of the battery are introduced. Then, when the battery repeatedly implements a discharge trial from the state of charge (SOC) 100 to 0%, an iterative learning based recursive least square (IL-RLS) algorithm is presented to accurately identify the non-linear parameters of the regression model. The essential idea of the IL-RLS algorithm is to improve the current parameter estimates by learning the predictive errors of the previous trials. After that, the parameters are identified as the functions of SOC by using the IL-RLS, which are verified by comparing with the results of the classic identification method for current pulses. As a result, an application-oriented SOC estimation scheme is proposed, where the IL-RLS calibrates the battery parameters offline and the classic extended Kalman filter (EKF) estimates the SOC in real-time. Finally, based on the EKF as well as the parameters identified by the IL-RLS, one static and three dynamic operating conditions are given to show the efficiency of the IL-RLS, where all the SOC estimation errors are <2%.

A non-isolated high-voltage gain dual-input DC/DC converter with a zero voltage turn-off (ZVT) auxiliary circuit has been presented. Two photovoltaic (PV) modules can be connected to the proposed converter with separate maximum power point tracking (MPPT). The cost of whole PV power generation system can be decreased significantly as a single converter is employed instead of two converters. All switches can achieve ZVT by an auxiliary circuit, and turn-off switching losses can be decreased and the efficiency of the converter can be improved. Working principle and performance characteristics of the proposed converter are analysed in detail, a dual-input maximum power point tracking control algorithm has been designed for the proposed converter. An 800 W experimental prototype has been built to verify the theoretical analysis.

Conventional battery/super-capacitor (SC) cell voltage equalisers require numerous switches and/or a multi-winding transformer, which are not desired in terms of circuit complexity and extendibility. In this study, a modularised non-isolated two-switch cell voltage equaliser for series-connected lithium-ion battery/SC is proposed. The proposed equaliser consists of a non-isolated front-end dc–dc converter and a full-wave voltage multiplier circuit. Without coupled-inductor, multi-winding transformer and multiple active switches, the proposed equaliser uses only two active switches and two magnetic components, thus it benefits from reduced complexity and circuit volume. Meanwhile, the modularised full-wave voltage multiplier circuit makes it flexible to extend to more battery/SC cells. Furthermore, it can work under open-loop without cell monitoring circuit, which makes its control simple. The equalisation current of the proposed equaliser can be limited automatically. Compared with conventional non-isolated equalisers using half-wave voltage multiplier, it benefits from faster equalisation speed and lower equalisation loss. High efficiency is achieved by zero voltage switching of all switches. Experimental results are provided to verify analysis results of the proposed equaliser.

Both the spectral analysis and the closed-form root-mean-square (RMS) equations are widely used to determine the three-phase inverter dc-link current for capacitor rating proposed. However, the analytical models of the dc-link currents have rarely been reported for applications like the active power filter, where ac currents are mostly low-order harmonics (LOHs). This paper first derived expressions for each dc-link LOH current, in order to compute the capacitor losses for each LOH frequencies. Then, it is shown that the derivation of the dc-link switching harmonic current (SHC) RMS equation is very much complicated when LOHs are present in the ac currents. Hence, new set of generalised RMS equations were successfully derived and simplified into one equation to facilitate the worst case design. The design case of the dc-link current is demonstrated with the proposed equations. A flexible grid-tied inverter lab prototype is developed to inject arbitrary combinations of LOH currents of different orders, sequences, amplitudes and angles into the grid. Good match between the computational and experimental results validates the proposed methods.

A digital hybrid current mode (HCM) control technique which combines peak current and average current mode (ACM) control methods is studied. The proposed controller consists of three control loops, an analogue fast current loop, a digital slow current loop and an outer voltage loop. For the control method, both continuous and discrete-time models are built. Similarly, a continuous-time model for ACM control is provided for comparison. For both control techniques, a compensator design method is proposed. The control methods are implemented on a 6 W synchronous buck converter with a mixed-signal ARM-based microcontroller. Controller models are verified with the frequency response measurements of the inner and outer loops. In digital HCM control, higher DC gain and phase margin is achieved with the same gain margin compared to digital ACM control. Furthermore, the transient responses of the systems are analysed. When the outer voltage loop is open, 30% faster dynamic response is measured by the digital HCM method. With voltage compensation, comparable dynamic response on the output voltage is achieved without inductor current overshooting by the digital HCM control.

Model-predictive direct-power control (MPDPC) has attracted increasing attention from scholars because of its outstanding dynamic response and high-power factor. However, its major shortcoming is the high-computational cost, which limits its application in three-level (3L) converters. By dividing the conventional MPDPC into two steps, a double-step MPDPC (DMPDPC) algorithm is presented to address this problem. The first step of this algorithm is dedicated to searching a sector including an optimal switching state (OSS). In the second step, the OSS in a chosen sector is gained. Furthermore, its driver signals are changed as soon as the OSS is gained and their delay time is detected. Then, the corresponding delay compensation is also proposed to improve the steady-state performance of the 3L-converter. The validity of the proposed approach is demonstrated by the experimental platform with 4 kVA rated power. The experimental results show that the computing time in DMPDPC is 50.82% of that in conventional MPDPC. In addition, the proposed DMPDPC decreases the 3L converter's active and reactive powers ripples, reduces its current harmonic and strengthens its robustness against parameter variation.

Impedance-based frequency-domain method is an effective tool for the stability assessment of a doubly fed induction generator (DFIG) system. Several impedance models have been proposed recently; however, these models are usually associated with model reductions since the complexity in achieving a detailed DFIG model. This may lead to unreliable stability results under certain conditions, and a clarification of this modelling effect is lacking in the literature. Therefore, this study aims to address this issue by developing a detailed DFIG impedance model. To achieve this target, a modular modelling technique is proposed instead of the conventional linearisation by parts, for which the components of a DFIG system are modelled as multi-port modules. Through this method, the detailed DFIG model together with four types of reduced-order models can be derived efficiently. The detailed DFIG model is verified by the measured frequency responses in PSCAD™/EMTDC™, along with its correctness in Nyquist-based stability analysis. Subsequently, four types of the reduced-order models are compared with the detailed one in terms of Nyquist plots, so that their performance and effectiveness for stability analysis are clarified. Besides, conclusions regarding the reduced-order models are also verified by time-domain simulations.

The high-efficiency inverter in a wide input voltage range is expected to be a solution for the distributed generation system. This study gives a high-efficiency two-stage topology and proposes a finite-control-set model predictive control (FCS-MPC) strategy. The main objectives of the proposed model predictive controller are: (i) simultaneously controlling multi-variables in the complex buck-boost current controller, (ii) optimal design calculation for predictive current and voltage, (iii) normalisation of the state variables for cost function formulation, and (iv) low correlation between the dc-link capacitor and control algorithm. A more reasonable operation mode of high-frequency switches is provided for the two-stage topology improving system performance. In order to optimise the total harmonic distortion of the output current and the error of the dc-link voltage, a suitable weighting factor could be designed in the proposed FCS-MPC method. The steady-state characteristics of the proposed controller are simulated based on MATLAB/Simulink. Experimental results demonstrate the validity and practicability of the proposed control strategy.

This study proposes a new scheme for online detection and identification of single and multiple insulated-gate bipolar transistor (IGBT) open-circuit faults in three-phase pulse-width modulation (PWM) inverters of AC machine drives, which is based on Park's vector of machine phase currents. First, the switch open-circuit faults are detected by monitoring dwell times of the vector of the actual phase currents expressed in the stationary reference frame in each sector, where the normalisation of the current to its reference value is utilised, by which the immunity to the false alarms in transient conditions is improved significantly. Then, the IGBT open-circuit faults are identified, where leg open-circuit conditions are in the first place determined based on the average values of the normalised line-to-line currents. Next, the single open-circuit IGBT is located from the polarity of the corresponding phase current. By the proposed diagnosis method, the fault detection time is at the longest about 52.3 and 54% of a fundamental period in the simulation and experimental tests, respectively, and the 27 possible cases of IGBT open-circuit faults combined for all IGBTs in the inverter can be identified. In addition, this algorithm can be implemented without any additional hardware and computational burden.

This study presents two methods of controlling neutral-point voltage oscillation in a hybrid VIENNA rectifier, which is composed of the parallel association of a three-phase single-switch Boost rectifier with a VIENNA-type rectifier. The neutral-point oscillation reason has been analysed with a mathematical model. Meanwhile, the two neutral-point control methods of a simplified method based on a zero-sequence component injection and a dual-carrier pulse-width modulation (PWM) method are proposed to control the voltage deviation of the split DC-link and three-time fundamental frequency neutral-point voltage fluctuation with a decrease from ±1.6 to ±1 V, respectively. Moreover, the significant oscillation in the neutral-point voltage caused by unbalanced loads or asymmetric capacitor parameters can also be effectively suppressed by using the dual-carrier PWM method. Furthermore, the performance comparison between these two methods is provided. The experimental results show that the system after being introduced the proposed two methods still exhibits a low-order input current harmonic such as second, third, and fourth harmonics as well as the input current total harmonic distortion is lower than the standard 5%.

The DC/DC converter needs the inductor to get the desirable increased voltage, which means it is impossible to avoid the power loss. Thus, minimising the inductor current may be a way to suppress the loss. In this study, to achieve higher efficiency of DC/DC converters, the control method to minimise peak current in boundary conduction mode (BCM) of the DC/DC converter is proposed when implementing soft switching of the converter switches. The comprehensive principle to minimise peak current in BCM is studied and the precise conduction time and conduction sequence of four switches of the buck–boost circuit are deduced. On comparing with the bipolar BCM and unipolar BCM, the proposed BCM could effectively reduce the inductor current in the DC/DC converter. Furthermore, low-voltage and high-voltage DC experiments were independently designed to verify the proposed control. The experimental results from a prototype of 1 kW DC/DC converter proved that this novel control method could realise the soft switching with the minimising peak current of the buck–boost converter switches and reduce the loss of the whole DC/DC converter.

Space-vector pulse width modulation (SVPWM) provides several degrees of freedom, which can be optimised to improve the harmonic performance of the three-phase inverter. Genetic algorithm (GA) and immune algorithm (IA) are the two classical probabilistic optimisation algorithms, which are simple in structure and do not need an accurate mathematical model. However, the optimisation accuracy and reliability are low when they optimise the high-dimensional non-linear problem, such as SVPWM control sequence of the three-phase inverter. To cope with these problems, a genetic algorithm–particle swarm optimisation (GA–PSO) is proposed here, which introduces the mutation of GA into discrete PSO. The global and local optimisation ability of the algorithm is greatly improved by the introduction of mutation operation. The results of MATLAB/SIMULINK simulation show that the weighted total harmonic distortion (WTHD) by the optimal SVPWM control sequence based on GA–PSO is 0.199%, which is much better than that of the PSO, IA, and GA. The average generation number of GA–PSO is only 1/500 of IAs. Further experimental data verify that the WTHD by the optimal SVPWM control sequence based on GA–PSO is lower than that of conventional SVPWM and IA.