[Show abstract][Hide abstract] ABSTRACT: This paper proposes a space-vector modulation (SVM) algorithm for a five-phase open-end winding motor drive system, fed by a dual nonsquare matrix converter (MC). The input to each of the MCs (MC-1 and MC-2) is a three-phase utility grid, and the output is a five-phase with variable voltage, variable frequency capability. The major contribution of this paper is the elimination of the detrimental common-mode voltage (CMV) that appears across the motor winding. In addition, the proposed SVM allows for a unity power factor at the input side, while boosting the output phase voltage by up to 150% of input. This paper presents a comprehensive analysis, to obtain the expression for the SVM modulating signals that are used to generate the switching pulses for the MC. To verify the idea, a modular, reconfigurable 5-kW MC prototype, feeding a five-phase induction motor is built. The control algorithm is implemented on a dSPACE-1006 platform. The test shows that the CMV is successfully eliminated from the motor winding. Other results (i.e., current and voltage waveforms) are also found to be in very close agreement with the theoretical prediction and MATLAB simulation.
[Show abstract][Hide abstract] ABSTRACT: Two four-level five-phase open-end winding drives are analysed in this paper, and their performances compared. The first topology consists of two two-level voltage source inverters (VSI) supplying a five-phase machine with open-end windings (OeW). The second topology comprises one three-level and one two-level VSI to supply the five-phase OeW machine. In both cases, two VSIs are supplied from isolated dc-sources, with voltages in a ratio 21. As a consequence, the output phase-voltage waveforms are equivalent to those produced by a four-level five-phase VSI. The paper shows that the considered topologies exhibit significantly different operating characteristics.
[Show abstract][Hide abstract] ABSTRACT: The quasi-Z-source cascade multilevel inverter (qZS-CMI) presents many advantages over conventional CMI when applied in photovoltaic (PV) power systems. For example, the qZS-CMI provides the balanced dc-link voltage and voltage boost ability, saves one-third modules, etc. However, the qZS-CMI still cannot overcome the intermittent and stochastic fluctuation of solar power injected to the grid. This paper proposes an energy stored qZS-CMI-based PV power generation system. The system combines the qZS-CMI and energy storage by adding an energy stored battery in each module to balance the stochastic fluctuations of PV power. This paper also proposes a control scheme for the energy stored qZS-CMI-based PV system. The proposed system can achieve the distributed maximum power point track for PV panels, balance the power between different modules, and provide the desired power to the grid. A detailed design method of controller parameters is disclosed. Simulation and experimental results verify the proposed system and the control scheme.
[Show abstract][Hide abstract] ABSTRACT: Conventional matrix converters (MCs) have limited voltage gain that is less than 0.866, whether for direct MC (DMC) or indirect MC (IMC). The Z-source matrix converters (ZSMC) overcome the voltage gain limitation of the traditional MC and achieve buck and boost operation with reduced switches count, therefore achieving low cost, high efficiency, and reliability, compared to the back-to-back converter. Furthermore, it will leads to more MC industrial applications. This paper presents an up to date comprehensive overview of the different Z-source matrix converter topologies and their configurations, circuit analysis, modulation schemes, and applications. This study offers a comprehensive and systematic reference for the future development of the Z-source matrix converters.
IEEE Transactions on Power Electronics 08/2015; DOI:10.1109/TPEL.2015.2471799 · 6.01 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The second harmonic $(2omega)$ power ripple of single-phase quasi-Z-source (qZS) photovoltaic (PV) inverter highly affects the whole system's design and performance. The topology's $2omega$ ripple model is very important to analyze qZS PV inverter's $2omega$ voltage and current ripple. The existing models did not consider the PV-panel dynamic and terminal capacitors, which causes the theoretical results apart from the truth. In this paper, a comprehensive modeling for single-phase qZS-PV inverter is proposed, where the $2omega$ ripple model of the qZS-PV inverter system with a real PV source is established and discussed without and with a PV terminal capacitor. The influences from qZS inductance and capacitance, and PV-panel terminal capacitance to the $2omega$ voltage and current ripple are investigated using the built model. The system parameter design method is proposed to mitigate this ripple. Simulation and experimental results validate the proposed $2omega$ ripple model and parameter design method.
[Show abstract][Hide abstract] ABSTRACT: This paper investigates the fault tolerant control strategies for a three to five-phase dual matrix converter fed open-end load system. There are two three to five phase matrix converter at both the ends of the load. In healthy condition both the matrix converters are sharing the load according to their modulation index. After the occurrence of an open-circuit fault in one of the matrix converter, it is disconnected and the other remaining converter shares the load according to its capacity (maximum rating is half of the dual converter). In the proposed scheme both the converters are sharing the load equally under normal operating conditions. After the clearance of fault, again both the matrix converters start working normally and sharing the load equally. In this paper it is shown that in a dual matrix converter supply system, they can work in healthy condition, post-fault condition and after clearance of the fault without break in continuity of the supply. Space vector pulse width modulation technique is used for control of the dual matrix converters under normal and post-fault conditions. Here open-end five-phase R-L load is taken for validation of the technique. Simulated results are verified experimentally.
[Show abstract][Hide abstract] ABSTRACT: In this paper a generalized multi-phase space vector theory is considered for developing the space vector modulation of a three-phase to six-phase AC to AC converter. The modulation is based on the control of the voltage vectors in the first d-q plane, while imposing the remaining voltage vectors in the second and the third planes (x-y, 0+-0-), being zero. The duty cycles of the bidirectional switches are obtained using space vector modulation theory. The proposed converter system offers full control of the input power factor, no limitation on the output frequency range and nearly sinusoidal output voltage. The proposed space vector algorithm can be fully implemented on a digital platform. The theoretical analysis is confirmed by digital simulations which is further verified using real time implementation.
[Show abstract][Hide abstract] ABSTRACT: Interleaved boost converters are used in multimegawatt wind energy conversion systems with synchronous generators (SG), after a diode rectifier stage to control the generator and provide voltage elevation for the grid connection at lower speeds. The use of a diode rectifier is possible due to the fact SG do not consume reactive power, making it a cost-effective solution to reduce the size and cost of the full-scale converter needed in SG based turbines. This paper proposes a finite control set model predictive control (FCS-MPC) for the interleaved boost converter capable of effectively distributing the power among the different boost channels. In addition, a new strategy to fix the switching frequency is introduced to the predictive control algorithm. A criterion is presented for the design of the weighting factors. The control method has been tested through simulation on a three-channel interleaved boost converter. The steady-state behavior achieved with the proposed method is similar to the one obtained with classic PI control and PWM. This work enables the use of FCS-MPC for interleaved boost converters, to be further included in existing FCS-MPC algorithms for applications where these converters are used, such as SG based wind energy conversion systems, where this control strategy has already been used for the grid side converter.
[Show abstract][Hide abstract] ABSTRACT: This study discusses the space vector pulse-width modulation (SVPWM) scheme for an eleven-phase two-level voltage source inverter, aimed at producing a sinusoidal output voltage waveform. Generalised space vector theory is used to realise the SVPWM. As per the general inverter switching theory, there are 211 = 2048 switching states that yield 2046 active voltage space vectors and one zero voltage vector, which results with two switching states. Out of the total of 2046 active voltage vectors, the most suitable set comprising 110 active voltage vectors is identified and is utilised in the implementation of the SVPWM. The sinusoidal voltage is obtained by controlling the duty cycles of the applied voltage space vectors in such a way that the non-zero reference voltage in the first (d-q) plane is achieved, while simultaneously zeroing the average voltage in the other four (x-y) planes in accordance with the zero references. The theoretical results are verified by experimentation using a passive resistive-inductive load. Finally, experimentally obtained total harmonic distortion values of the phase voltage and current for the eleven-phase SVPWM are compared with the corresponding values obtained using SVPWM for other odd phase numbers.
IET Power Electronics 06/2015; 8(6). DOI:10.1049/iet-pel.2014.0327 · 1.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper presents the performance assessment of three active Islanding Detection Methods (IDMs) for a quasi-Z-Source (qZS) based Power Conditioning System (PCS). The proposed PCS consists of a three-cell Cascaded H-Bridge (CHB) inverter where each module is fed by a qZS network. The proposed combined controller achieves grid-tie current injection, DC-link voltage balance for all qZS-CHB inverter modules, and anti-islanding protection. The anti-islanding protection performance is evaluated for three phase-shift based active Islanding Detection Methods (IDMs), namely Active Frequency Drift (AFD), Slide-Mode Frequency Shift (SMS), and Sandia Frequency Shift (SFS). Simulation results and real-time implementation using dS1103 board are carried out to validate the proposed design.
[Show abstract][Hide abstract] ABSTRACT: The single-phase quasi-Z source inverter topology (qZSI) is attracting attentions for the single-phase grid-tie photovoltaic applications. However, due to the inherent second harmonic power flow in a single phase system, a large qZS network is required to reduce the second harmonic components of current and voltage at the dc port. Minimization of this qZS network remains an open research topic. This paper proposes a design method for the single-phase qZSI topology to minimize the qZS capacitance and inductance. A second harmonic power flow model for the single-phase qZSI is derived and ripple power is analyzed for the minimization solution of the qZS network. A current ripple damping control is proposed to ensure suppression of the second harmonic power flow in the inductor. The proposed design and conventional design methods are compared through design examples, simulation comparison, and experimental verification. These results verify the proposed minimization design method.
[Show abstract][Hide abstract] ABSTRACT: Second harmonic pulsating power flows through the dc side of the single-phase quasi-Z-source inverter (qZSI). This requires bulky capacitor banks and inductors to suppress the second harmonic ripple of dc-link voltage and inductor currents. However, the resultant qZS network seriously deteriorates the system reliability, efficiency, volume, weight, and cost. This paper proposes an active filter integrated single-phase qZSI topology to transfer the low-frequency (second harmonic) power ripple directly from the ac load to the active filter ac capacitor. Thus low-frequency power ripple will not be present at the dc side, and constant inductor current and constant capacitor voltage are ensured. The qZS impedance is small because only high frequency switching ripple is present and the active filter supports ac voltage (large ripple) enabling small values of capacitance - both of these characteristics result in low size and low weight. This paper investigates the analysis, modeling, parameter design method of qZS network and active filter, as well as control strategy of the proposed topology. Comparative evaluation and experimental results verify the proposed new topology system.
[Show abstract][Hide abstract] ABSTRACT: A hybrid pulsewidth modulated single-phase quasi-Z-source inverter (qZSI) based grid-tie Photovoltaic (PV) power system is proposed. The hybrid pulsewidth modulation (HPWM) conducts PWM when the required ac output voltage is lower than the dc source voltage, otherwise it performs pulse-amplitude modulation (PAM) for the single-phase qZSI. The low-frequency ripple voltage of dc link is utilized, resulting in reductions of quasi-Z-source inductance and capacitance, as well as power devices' switching actions. Control strategy of the proposed system is further presented to track the maximum power points of the PV panel and to inject the extracted PV power into grid. A grid-tie current controller, combining with the plug-in repetitive control and proportional-resonant regulator, is employed to achieve strong harmonic suppression, fast convergence, and zero tacking error. The system dynamic model is disclosed to design controllers. Simulation and experimental results demonstrate validity of the proposed system.
[Show abstract][Hide abstract] ABSTRACT: Due to variability of solar energy resources, maximum power point tracking (MPPT) of photovoltaic (PV) is required to ensure continuous operation at the maximum power point (MPP) and maximize the energy harvest. This paper presents a digital model predictive control technique to employ the MPPT for flyback converter for photovoltaic applications. The MPP operating point is determined by using perturb and observe (P&O) technique. The proposed two-steps predictive model based MPPT presents significant advantages in dynamic response and power ripple at steady state. A characteristic of MPC is the use of system models for selecting optimal actuations, thus evaluating the effect of model parameter mismatch on control effectiveness is of interest. In this paper the load model is eliminated from the proposed MPC formulation by using an observer based technique. The sensitivity analysis results indicate a more robust controller to uncertainty and disturbances in the resistive load.
IEEE First Workshop on Smart Grid & Renewable Energy (SGRE), Qatar; 03/2015
[Show abstract][Hide abstract] ABSTRACT: This paper presents maximum power point tracking (MPPT) and decoupled power control for single phase grid-tied photovoltaic (PV) systems. Model predictive control (MPC) technique is used to extract the maximum power from the PV array and feed it to grid. The stochastic behavior of solar energy necessitates MPPT of PV system to operate at maximum power point and make the system economical. Power control of grid-tied inverters are commonly based on synchronous reference frame transformation, this methodology requires the phase angle information by phase-looked loop (PLL). In this paper MPC technique is used for decoupled active and reactive power control of the single phase grid-tied inverter. The proposed technique does not need PLL, modulation module and synchronization transform, which makes the control algorithm simple for digital implementation. Comparing the developed technique to the conventional perturb & observe (P&O) method indicates significant improvement in PV system performance. The simulation result is validated by implementing the control algorithm experimentally using dSPACE 1007.
IEEE First Workshop on Smart Grid & Renewable Energy (SGRE), Qatar; 03/2015
[Show abstract][Hide abstract] ABSTRACT: This paper presents a model predictive control technique for standalone doubly fed induction generators (DFIGs) without using position sensor. The technique uses a discrete-time model of the system to predict the future value of the rotor current for all possible voltage vectors generated by the rotor side converter (RSC). In this study, due to computational simplicity, the absolute error is selected as a quality function. Also, rotor position phase locked loop (RP-PLL) algorithm is used to achieve sensorless operation. The proposed MPC with RP-PLL sensorless algorithm is designed and simulated in Matlab &Simulink. Simulation results, including constant speed and load changes, and also variable rotor speed and constant load, are presented. The simulation results have proven excellent performance of the proposed MPC with RP-PLL sensorless algorithm, both of load and speed changes conditions.
[Show abstract][Hide abstract] ABSTRACT: This work proposes a new control scheme for electrical drives system, named cascaded predictive speed control (PSC). The strategy seeks to maintain the simplicity of the classic predictive control while excluding linear or other controllers. The control strategy has a cascade architecture, similar to the techniques of classical control (FOC or DTC). The outer loop controls the speed of the machine, determining a reference torque through a mechanical dynamic model, which allows tracking the speed reference. The inner loop controls the stator current with a cost function that selects the state of the converter which generates the best tracking references for the stator current synchronous components. Preliminary simulation results confirm the effectiveness of this approach, which produces produces a high quality drive control.
[Show abstract][Hide abstract] ABSTRACT: This paper presents a novel seven-phase open-end winding drive system supplied by the dual non-square matrix converter. The input to each of the matrix converter is three phase utility grid system and the output is seven phase voltages with variable voltage and frequency. The two matrix converters feeding a seven-phase load are supplied from a common single three-phase utility source of 50 Hz. Space vector based PWM algorithm is developed to control the dual three to seven-phase matrix converter. The proposed control technique eliminates the common-mode voltage across the machine winding and hence no zero sequence currents will be produced and therefore no isolated supply is required for the dual three-to-seven phase matrix converter system. Further the proposed technique will enhance the seven phase machine phase voltage to 1.95 times the voltage produced by a single three to seven phase matrix converter system in the linear modulation range. The paper presents the analytical approach to obtain the expression of modulating signals that are used to generate the switching pulses for the matrix converter. Simulation results are presented to support the idea of the proposed modulation scheme.
[Show abstract][Hide abstract] ABSTRACT: This paper presents a single-phase zero-voltage switching (ZVS) AC-link inverter for PV-grid connection at maximum power operation. The PV modules charge an AC-link until it reaches a certain reference current waveform; while, in the same time, the PV modules is connected to the grid inverter via a series inductor. Then the PV modules are disconnected and the charged AC-link discharges into the grid. The proposed controller employs a conventional MPPT to maximize the PV output power. Then the controller generates the link's reference current to fulfill both of MPPT and the desired active/reactive power needs to be injected into the grid. The proposed topology along with the proposed controlling strategy achieves a flexible and continuous power flow features. A detailed descriptive figure of the inverter's operating modes and their switching strategy is presented in this manuscript. Furthermore, a simulation model is developed in MATLAB/Simulink environment for the overall system and the results are addressed. Results show that the proposed AC-link inverter successfully achieves PV-grid integration at good dynamic and steady-state performances.