Control of a single-switch two-input buck converter for MPPT of two PV strings

© 2014 ACPE. In this paper, the configuration composed by a Two-Input Buck (TIBuck) converter and a boost inverter is proposed for low-voltage grid-connected PV systems. This configuration is attractive for this application because it has high efficiency and can achieve dual maximum power point tracking (MPPT) with only one active switch. However, in this system, the nonlinear characteristics of the converter and the two PV arrays complicate the control. By means of a small-signal modeling, the control theme of the two PV voltages is formulated and the effect of the nonlinearities is presented. Simulation results are reported to validate the theoretical analysis, showing the dual MPPT capability

Advanced multi-functional model predictive control for three-phase AC/DC converters

© 2016 The Institute of Electrical Engineers of Japan. With the conventional model predictive control (MPC) based direct power control of three-phase AC/DC converters, the active and reactive powers can be simultaneously controlled by a single cost function. A change in parameters of either the active or reactive power within the cost function will affect the other, leading to poor dynamic performance of transient response. Besides, the steady state performance of the conventional MPC is affected by one-step-delay of digital implementation. This paper proposes an advanced multi-functional MPC of three-phase full-bridge AC/DC converter for high power applications. It has multiple functions such as one-step-delay compensation, power ripple reduction, switching frequency reduction, and dynamic mutual influence elimination. Using the proposed modified cost function, both the steady state and dynamic performances of the converter can be improved. Finally, the simulation results are reported to validate the advancement of the proposed control strategy in comparison with other control methods

Low-complexity dual-vector-based predictive control of three-phase PWM rectifiers without duty-cycle optimization

© 2013 IEEE. The conventional model-predictive-based direct power control (MPDPC) of the three-phase full-bridge AC/DC converters chooses the best single voltage vector for the following control period, which results in variable switching frequency and power distortion, and thus a relatively higher sampling frequency is needed to achieve acceptable results. This paper proposes a simplified dual-vector-based predictive direct duty-cycle-control (SPDDC) with an additional zero vector implemented in contrast to the MPDPC. With the same best vector selection method, the proposed strategy has retained the control simplicity with just one more step added and much better control performance as well as a fixed switching frequency in comparison to the MPDPC. On the other hand, the duty-cycle optimization procedure is eliminated while the negative duration issue is essentially resolved compared with the conventional dual-vector-based model predictive duty-cycle-control (MPDCC). Comprehensive comparisons of various control methods by numerical simulation and experimental testing show that the SPDDC can achieve better steady state and dynamic performance than the MPDPC and simpler algorithms than the MPDCC

Analysis of a shunt maximum power point tracker for PV-battery system

© 2015 IEEE. This paper first presents a maximum power point efficiency analysis of the conventional direct connection of PV panels to a battery. Next, an improved shunt maximum power point tracking (MPPT) which integrated a half-bridge converter with a full-bridge load is proposed. The configuration is designed such that the PV panel voltage equals the sum of capacitor voltage and battery. This capacitor voltage is controlled to achieve the MPPT of the PV panels. Some experimental results are reported to verify the proposed concept and analysis

Feasibility study on using pipe type cables and CoAxial cables for HFAC power distribution in data centre applications

© 2017 IEEE. This paper investigates into the power cable used in HFAC Power Distribution Systems (PDSs) and recommends new cable types that could be used to improve the performance. While using the same materials and trying not to increase the weight per unit length, the cross section of the cable has been modified to minimize the losses observed in HFAC applications. With higher operating frequencies, the skin effect of conductors dominate and the cable impedance increase exponentially, overcasting the benefits of using HFAC. Upto now, cables manufactured with DC ratings have been used in AC applications with various de-rating factors to account for the additional impedance. Although this approach has worked well with 50/60Hz applications, when extended to HFAC the PDSs become bulky and heavy, thus not effective and even question the benefits of using HFAC in PDSs. Therefore, a new approach of using different cross sections of cables for HFAC applications is proposed. Optimal sizes could be selected in accordance with manufacturing limitations leaving the fine adjustments to be made with the HFAC grid parameters for extracting the maximum benefits out of HFAC PDSs

A control scheme combining state-of-charge balancing and voltage/current regulation for a distributed battery system based on fly-back converter

© 2016 IEEE. This paper presents a control scheme combining SoC balancing and voltage/current regulation for a distributed battery system based on fly-back converters. In discharging operation, the proposed control scheme consists of two control loops. The first control loop is designed to regulate all battery terminal voltages to be identical, thus SoC imbalance issue is solved from the root. The other control loop is designed to regulate the output voltage. These two control objectives are combined into one system. In charging operation, the flyback converters are operated in discontinuous conduction mode (DCM). As a result, the charging power of each battery is identical. Therefore, SoC imbalance issue is avoided. The analysis of the control scheme and prototype validation based on flyback converters are provided to illustrate and demonstrate the proposed control scheme

A flyback converter based partial power processing structure for BESS with voltage/current regulation and battery balancing functionalities

© 2017 IEEE. This paper presents a flyback converter based partial power processing structure for battery energy storage system (BESS). It combines both of the battery balancing functionality and power stage regulation functionality into one system. The proposed BESS only have one control variable which is the common duty cycle for all the flyback converters. It is used for the voltage or current regulation. There is no active control for the battery balancing because the current sharing of individual battery is directly proportional to the battery terminal voltage in discharging mode and inversely proportional in charging mode. The unbalanced battery terminal voltages will gradually converge while system running. Beyond these, only a small portion of the total discharging/charging power is processed by the converters. The overall system efficiency can be significantly improved compared to traditional BESSs. Experimental results of a prototype with two batteries verified that the proposed BESS provides satisfied performance

Review of battery cell balancing techniques

© 2014 ACPE. A highly reliable and efficient battery management system (BMS) is crucial for applications that are powered by electrochemical power. Cell balancing is one of the most important features of a BMS. Cell balancing techniques help to distribute energy evenly among battery cells. Without cell balancing, a portion of the capacity or energy in the battery bank will be wasted, especially for long battery string which operates in frequent recycling condition. In this paper, some popular cell balancing techniques are described and categorized according to the way of processing redundant energy in battery cells

Single-phase single-stage ZCS boost PFC rectifier with reduced switch count

© 2014 ACPE. In this paper, a new single-phase single-stage ZCS PFC boost rectifier with reduced switch count is introduced. The efficiency of the proposed converter is improved by eliminating input stage diode-bridge. Moreover, only two active switches are used to permit bi-directional current flow from high-voltage-rail to low-voltage-rail and vice versa. Hence, no auxiliary switch is needed. A resonant inductor and a capacitor are used to make both switches operate at ZCS turn-off and soft turn-on. The proposed converter is developed by using totem-pole bridgeless boost (TPBLB) converter. Standard components are used to prove that the proposed converter is working with acceptable performance compared to other bridgeless boost converters with soft-switching. In addition, a PWM controller is proposed, which combines a conventional average-current-mode power factor correction (PFC) controller, several logic-gates and a phase detector. A detailed analysis of the converter operation and control is supported by simulation results. Finally, a 400 W, 50 kHz experimental prototype is built to verify the theoretical analysis and performance of the proposed converter

Encoderless FS-PTC for induction motor with extended Kalman filter

© 2014 ACPE. This paper proposes an encoderless finite state predictive torque control (FS-PTC). In FS-PTC, stator flux and torque are predicted using a finite number of inverter switching states to select an optimal voltage vector to be applied to the motor by actuating a predefined cost function. Up to now, extended Kalman filter (EKF), a promising state observer for encoderless control system, has not been used with FS-PTC to estimate motor speed and flux, since it needs more calculation time. However, it can be implemented by sacrificing a small amount of torque and flux ripples. Hence, in this paper, EKF is used to estimate rotor speed and flux. Then, the stator flux is estimated from the estimated rotor flux. Measurement noises in the currents are also filtered out through EKF. Simulation results show that the proposed estimator can estimate the speed accurately, at both speed reversal and load change conditions. The sensitivity of the control scheme is also investigated for the deviations of stator and rotor resistances