UNIDIRECTIONAL BRAKING ENERGY RECOVERY SYSTEM FOR ELEVATORS

The paper discusses design of energy storage based energy recovery system for elevators. The main element of such system is unidirectional DC-DC converter to control energy flow to supercapacitor or li-ion battery based energy storage. The paper gives explanation of selection of the converter topology and some design considerations. The test results of experimental prototype on a developed test bench are presented in the paper

Digital Control of Variable Frequency Interleaved DC-DC Converter

This paper represents a design and implementation of a digital control of variable frequency interleaved DC-DC converter using a digital signal processor (DSP). The digital PWM generation, current and voltage sensing, user interface and the new period and pulse width value calculation with DSP STM32F407VGT6 are considered. Typically, the multiphase interleaved DC - DC converters require a current control loop in each phase to avoid imbalanced current between phases. This increases system costs and control complexity. In this paper the converter which operates in discontinuous conduction mode is designed in order to reduce costs and remove the current control loop in each phase. High current ripples associated with this mode operation are then alleviated by interleaving. Pulse width modulation (PWM) is one of the most conventional modulation techniques for switching DC - DC converters. It compares the error signal with the sawtooth wave to generate the control pulse. This paper shows how six PWM signals phase-shifted by 60 degrees can be generated from calculated values. To ensure that the measured values do not contain disturbances and in order to improve the system stability the digital signal is filtered. The analog to digital converter's (ADC) sampling time must not coincide with the power transistor's switching time, therefore the sampling time must be calculated correctly as well. Digital control of the DC-DC converter makes it easy and quickly to configure. It is possible for this device to communicate with other devices in a simple way, to realize data input by using buttons and keyboard, and to display information on LED, LCD displays, etc

Simulation Based Analysis of Digitally Controlled 4-phase DC-DC Converter with Coupled Inductors

Interleaved converters are used in many different conversion systems involving various topologies and are related to different fields of application due its advantages over single-phase converters. Such advantages include reduced current in switching devices and passive elements, reduced output current ripple, and so on. Reductions in size and costs of magnetic components and inductors current ripple can be achieved by an integration of magnetics. In this paper application of 2-phase coupled inductor designed in convenient way by using commercially manufactured coil formers and ferrite cores is analyzed to developed 4-phase  interleaved DC-DC converter. Different structures of the coupled inductor for 4 phases is studied. The steady state phase and output current ripple in buck mode of the interleaving magnetic integrated bidirectional DC-DC converter is simulated. The necessary count of inductors for selected topology are  manufactured and placed on the PCB board

CAPACITANCE REDUCTION USING RIPPLE SUPPRESSION CONTROL OF SINGLE PHASE ENERGY STORED QUASI-Z-SOURCE INVERTER

The energy stored Quasi-Z-source Inverter (qZSI) allows integrate energy storage in addition to the other energy source mainly for output power smoothening. Single phase inverter suffers from double-frequency power ripple in the input side and also in the energy storage that is transferred there from the ac-side. In qZSI must be used large electrolytic dc capacitors in the impedance network to suppress this 100 Hz ripple. Also to suppress this ripple can be applied two types of power decoupling: passive power decoupling and active power decoupling. In this paper is analyzed passive power decoupling that is realized by means of the modified control strategy that produces the time-varying shoot-though duty cycle to mitigate power ripple without deteriorating of the output power quality. The validity of proposed control strategy was confirmed by simulation results that were obtained in PSIM software

An Accurate Mechanical Overload Detection for Induction Motor via Sensorless Load Torque Estimation

Induction motors are widely used in many industries. In many cases, the load torque value on the motor shaft is variable and the measurement of the torque allows control of the technological process. This paper proposes a torque detection method that can be implemented without expensive sensors and very accurate model of the induction motor. To implement this method only stator current measurement is required. Motor speed is detected and calculated from current spectrum. After that, the torque can be estimated from linearized torque-slip relationship. Proposed method is explained theoretically and followed by experimental implementation results. The test results validate the proposed method and show close agreement between estimated speed and torque values and the real measurements.acceptedVersionPeer reviewe

A new DC-DC converter linking LCC-HVDC transmission networks

Transferring bulk power via high voltage direct current (HVDC) transmission is dominated by line commutated converters (LCC). This is due to the robustness and higher ratings of the thyristors as well as the higher converter efficiency. Nevertheless, most of these transmission networks are point to point. This is due to the challenges of allowing multi-terminal LCC based networks and power reversal. This paper introduces a new dc-dc converter topology that allows connecting two independent LCC networks. The proposed converter is based on insulated gate commutated thyristors (IGCTs). Utilizing IGCTs allow mimicking similar control and performance as in insulated gate bipolar transistor (IGBT) based voltage source dc-dc converters. However, IGCTs have more superior features over IGBTs such as higher efficiency, higher short circuit current and higher power ratings. Detailed analysis and simulations are provided to validate the proposed converter topology, which confirms its potential in connecting HVDC-LCC networks