Simon Round

A fully digital hysteresis current controller for an active power filter

An active power filter is used to eliminate current harmonics produced by nonlinear loads. This paper discusses a fully digital method of controlling a power inverter used to inject the active filter compensating currents into the power system. A digital signal processor performs the harmonic isolation and generates a digital reference current. A hysteresis current controller has been implemented in a field programmable gate array that generates the inverter switching signals using this reference. This reduces the analogue circuitry and enhances the systems immunity to electromagnetic interference. The performance of a small-scale inverter under completely digital control is presented and discussed.

Real-time optimization of an active filter's performance

Recent advances in power electronics have meant that many loads now draw a distorted current from the power supply. For the same real power consumed, the apparent power for the distorted load is greater than the equivalent sinusoidal load. A real-time active filter optimization algorithm has been implemented in a TMS320C30 DSP, with the aim of maximizing the monetary saving from active filtering by reducing the apparent power consumed at the point of supply. As the basis for this optimization a savings function which takes into account active filter efficiency, the cost of energy, and the supply and load current distortion before and after filtering, has been derived. A simplex optimization technique, which is able to find the optimum operating point even under varying load conditions, is used to maximize these energy savings. >

An adaptive battery monitoring system for an electric vehicle

In electric vehicles it is important to know the state of charge of the batteries in order to prevent vehicle strandings and to ensure that the full range of the vehicle is exploited. It is also useful to know state of health information about the batteries to predict when the batteries need replacing. This paper describes a battery monitoring system that is able to calculate the state of charge and state of health of multiple batteries in a battery bank. It has been designed specifically to monitor lead-acid batteries in an electric car environment using noninvasive measurement techniques. The monitor incorporates an adaptive monitoring method, which is based on coulometric measurements when the batteries are under load and predicted open circuit voltage measurements under noload conditions.

The transient and steady state performance of a shunt active filter using measured site data

This paper presents the analysis of real power system events recorded at a light industrial site to determine the effect of a shunt active filter on power quality. The shunt active filter is shown to improve power quality by lowering the distortion of the supply voltage in both the transient and steady state. The shunt active filter power rating and other design information are also determined. The performance degradation of the shunt active filter when it has a limited rating is then demonstrated. In one case the voltage distortion is made worse by the active filter. The requirements that various transient events, including capacitor switching and induction motor starts, place on the shunt active filter design are outlined. These requirements are such that the required switching frequencies exceed those attainable with IGBTs and transient ratings dominate the active filter design constraints.

Design of an auxiliary power distribution network for an electric vehicle

This paper presents the design of an auxiliary power distribution network for an electric vehicle. Efficiency is a key element in the design for any electric vehicle and a 48 Vdc distribution network will be used throughout the vehicle. The high efficiency Cuk converter has been selected as the most appropriate topology to supply the various distributed loads. To achieve the best compromise between efficiency and component sizes, a switching frequency of 100 kHz is used. The results from simulations and experimental measurements are discussed and a range of proposals is also made to modify some of the existing loads to further improve efficiency.

An improved three-level shunt active filter

A shunt active filter is capable of removing harmonic currents from the supply of commercial and industrial sites. This paper presents a novel method for generating the compensating current signal for an active filter that uses a three-level inverter to provide a fast transient response. It is shown that the active filter must be positioned downstream of the power factor correction capacitors for stable operation. A new compensating current technique, based on sinusoidal subtraction, together with the faster response of the three-level inverter produces a shunt active filter system that has superior performance compared to traditional two level systems.

Achieving sinusoidal rectifier input currents while minimising the kVA rating of controllable switches

A three-phase diode bridge rectifier is commonly used in many power electronic systems to convert the utility voltages into a DC voltage. Nonsinusoidal supply currents drawn by such systems are of concern to electricity supply authorities. With the objective of obtaining sinusoidal current, this paper compares three techniques in terms of total kVA rating of the controlled switches: (1) an active filter added between the supply and rectifier; (2) an active filter with a boost converter controlling the DC current of the diode rectifier; (3) a six switch, PWM power converter. Computer and experimental results of the active filter in combination with the boost power converter are presented which show the system to be an economical solution in terms of the total kVA rating of controllable switches.<<ETX>>

Design Of An Intelligent Controller For An Active Filter

Absfmdr A technique of achieving both active current distortion compensation and power factor correction zk bnem described The active filter hm been evaluated using a single phase prototype circuit thatprovides up to 2 kVA of distortion compensation. There is an optimum operating range for the active filter which k determined by the choice of average switching frequency and invener DC bus voltage. Experimental results, illurtrahg the filters abilig to reduce the current harmonic distortion components, are presented On the bask of these experimental results, the design of an intelligent controller, using a Texas Instruments TMS32OC30 Digitul Signal Processor (DSP), for the active filter is

Decentralised source scheduling in a model nanogrid using DC bus signalling

Abstract Ananogrid is a small DC power system that uses distributed energy sources to power local loads. DC bus signalling, a novel control strategy that schedules sources in a decentralised fashion, brings the non-renewable sources in a nanogrid online when the renewable sources have been exhausted. This paper presents a prototype model nanogrid that uses power electronic converters to interface the sources and loads to the nanogrid. The design of the system is discussed and experimental results are presented. The results show that DC bus signalling allows the sources to be consumed in a prioritised fashion.

Real time optimisation of active filter energy savings

Due to advances in power electronics, many loads now draw a nonsinusoidal or distorted current from the supply. For the same real power, the kVA level for the harmonic load is greater than the equivalent sinusoidal load. Therefore the industrial user of harmonic loads has a greater energy cost. To reduce the distortion drawn from the power system, a shunt active filtering system has been developed. A relationship for determining the savings made from active filtering is derived and this savings function has been implemented in an intelligent controller using a TMS320C30 Digital Signal Processor. The simplex method is used to determine the optimum operating point, taking into account supply current distortion and the cost of energy. The active filter is thus able to determine its own operating point (DC bus voltage and average switching frequency) which maximises savings within a given set of constraints.<<ETX>>