Kristaps Vitols

Analysis of electronic differential for electric kart

A simple electronic differential for electric kart with separately driven rear wheels is analysed. A kart model for electronic differential implementation has been developed. The performance of the elaborated differential has been tested using simulation in MatLab Simulink.

Drive selection for electric kart

In this paper the parameters for choosing an electric drive for an electric kart have been analyzed. The advantages and disadvantages of different electric drive configurations have been shown while focusing on development of academic research prototype for future use in student education.

Closed current loop regulator for electric kart DC motor torque stabilization

PID regulator has been adapted to control DC motor current of an electric cart. Both simulation and experiments were carried out to evaluate controller operation during step-change of control signal. The aim is to stabilize motor torque and monitor motor current to protect power converter from dangerous current overshoots.

Low-Cost Voltage Zero-Crossing Detector for AC-Grid Applications

Abstract Renewable energy sources and energy storage devices are becoming more popular. Some of them like small hydropower turbines, wind turbines and diesel generators produce AC voltage with different frequency and voltage than the main grid. For them power electronics converters are necessary. Power electronics converters presented in industry use two or three level energy conversion, although direct AC to AC converters exist, but one of the main problems is the switch commutation when current or voltage is crossing the zero point. Zero crossing sensors are used to solve this problem. They consist of current or voltage measurement unit and zero crossing detector. Different approaches are used for zero crossing: hardware or software. Hardware approach is simple but it has low precision. Software approach has high precision but it is complicated and expensive. In this paper a simple low cost high precision approach is presented. It takes all advantages from both approaches. While tested with two types of microcontrollers the precision of experimental measurement is 25 μs - 40 μs.

Design of an embedded battery management system with passive balancing

This article documents the results of designing an embedded battery pack for an educational electric kart. The work is based on a previous project where an electric kart drive train was designed. The new lithium ion battery pack design is described and the need for a microcontroller controlled battery balancing system is based. A passive cell balancing solution is implemented as a small cell balancer board. A central control board is designed to collect cell status information, analyze the obtained data and provide information to the end user. The collected information is stored in a memory card for further battery pack performance evaluation. The paper shows an example of obtained charge/discharge data.

Efficiency of LiFePO4 battery and charger with passive balancing

This paper is intended as the first part of a two paper series that evaluate the efficiency of a battery pack with charger that has an integrated cell balancing method. For the first paper a simple passive balancing method is used while for the second an active shared transformer balancing method will be used. The paper first discusses the existing works on the subject of cell balancing efficiency. Further the results of experimental testing of cell capacity are provided. A previously designed modular passive balancing system is briefly introduced as it is used for the battery efficiency evaluation. Testing results reveal the battery pack efficiency with balancing as the difference between the energy that is required to charge the pack and the energy that can be obtained when the battery the battery is discharged. While the first efficiency test uses a laboratory power supply to charge the battery pack, the second efficiency test uses a prototype charger circuit. The same charger circuit with different secondary side is to be used for the second article. The prototype charger is required so that the efficiencies of both passive and active balancing methods can be reliably compared.

Redesign of passive balancing battery management system to active balancing with integrated charger converter

The use of high power high efficiency battery systems is increasing as the fields of personal electric vehicles and other fields requiring DC energy storage elements are growing. A typical battery pack consists of series connected cells that need to be monitored and controlled to achieve optimal performance. In this article the author previous work regarding passive balancing circuit is described and the performance of a passive balancing circuit is given and drawbacks are discussed. Another method of active balancing is proposed. The new method combines an active balancing method and a charger topology to develop an integrated charger-balancer solution. The basic calculations of the converter are given. To evaluate the operation of the system a three supercapacitor cell charger circuit was developed and tested with three different capacitor initial voltages. The obtained results and system performance is discussed.

Efficiency of LiFePO4 battery and charger with a mixed two level balancing

This paper is intended as the second part of a two paper series that evaluate the efficiency of a battery pack with charger that has an integrated cell balancing solution. In the first paper a simple passive balancing with a half bridge charger was designed and tested for energy efficiency. This paper continues the work by redesigning the half bridge charger circuit to implement a multi secondary winding transformer balancing circuit. The designed active balancing circuit splits the battery pack in four sections - each section is balanced actively. Each of the sections contains five cells which use the same passive balancing as before. The result is a mixed two level balancing circuit that is integrated in the charger topology. The battery pack with the charger/balancing circuit has been tested to obtain energy efficiency measurements which are compared with the previously obtained passive balancing measurements.

Considerations regarding the concept of cost-effective power-assist wheelchair subsystems

Abstract The present paper deals with the concept of a cost-effective power-assistant wheelchair. An analysis of the market situation and recent technical achievements is done at the beginning. On its basis, a set of solutions suitable for the development of such wheelchairs has been composed. It is shown that the key features of the considered concept are: segmented electrical motor and drive, sectioned battery pack, modular charger and an ANN matrix that provides easy and intuitive interfacing of sensor networks, pseudo-bionic feedbacks and the decision-making unit. Within the scope of the paper, a 3D model has been developed and 3D modelling has been conducted. As a result, certain drawbacks in the design and placement of elements have been found and a modification of the concept has been proposed

Lithium ion battery parameter evaluation for battery management system

Modern lithium ion batteries such as LiFePO4 are an active topic because of their good parameters. Yet as all lithium based batteries they need battery management systems for proper operation. The design and testing of such systems is very time consuming and additionally the cell testing and deep discharge or full charge can become dangerous because of cell operational limits. Typically battery models are used for simulation of such systems, yet the manufacturers do not provide all the necessary information to construct the models. This article is intended to provide some information such as cell capacity dispersion and open circuit voltage necessary for the development of a cell model. The same information can be used to develop state of charge estimator as well.