André Veltman

Advanced Electrical Drives

Electrical drives convert in a controlled manner, electrical energy into mechanical energy. Electrical drives comprise an electrical machine, i.e. an electro-mechanical energy converter, a power electronic converter, i.e. an electrical-to-electrical converter, and a controller/communication unit. Today, electrical drives are used as propulsion systems in high-speed trains, elevators, escalators, electric ships, electric forklift trucks and electric vehicles. Advanced control algorithms (mostly digitally implemented) allow torque control over a high-bandwidth. Hence, precise motion control can be achieved. Examples are drives in robots, pick-andplace machines, factory automation hardware, etc. Most drives can operate in motoring and generating mode. Wind turbines use electrical drives to convert wind energy into electrical energy. More and more, variable speed drives are used to save energy for example, in air-conditioning units, compressors, blowers, pumps and home appliances. Key to ensure stable operation of a drive in the aforementioned applications are torque control algorithms. In Advanced Electrical Drives, a unique approach is followed to derive model based torque controllers for all types of Lorentz force machines, i.e. DC, synchronous and induction machines. The rotating transformer model forms the basis for this generalized modeling approach that ultimately leads to the development of universal field-oriented control algorithms.

Prediction of Battery Behavior Subject to High-Rate Partial State of Charge

An online optimization procedure provides the parameters of a nonlinear battery model by taking into account a few minutes of measured current-voltage data. Within a defined range in terms of charge current, state of charge (SOC), and duration of charge and discharge events, the model is able to capture the relevant battery dynamics and predict the behavior for the next few minutes. From the battery behavior during specific events, the state of the battery can be revealed, which is defined as the state of function. Validation, which is carried out on measured current-voltage profiles, shows the accuracy of prediction during the high-rate partial SOC operation. Even with the data measured during a city drive within a microhybrid electrical vehicle, the method is able to predict the voltage level during high-rate discharge pulses (cranking).cranking

Control of Synchronous Machine Drives

This chapter deals with field-oriented control of synchronous machines. Field-oriented control has become common choice for many servo-drive applications due to the availability of affordable digital signal processors (DSPs). Controls are derived for both non-salient and salient synchronous machines. The operation in field weakening with constant stator flux linkage and with unity power factor is analyzed.

Control of Induction Machine Drives

In this chapter, attention is given to the control concepts that can be used to achieve independent torque and flux linkage control of induction machines over a wide speed range. First, classical V/f control concepts with very limited dynamic performance capabilities will be discussed. Next, field-oriented control techniques will be discussed. A key role is assigned to the presentation of a universal field-oriented (UFO) model which is used in conjunction with a current source induction machine model. At a later stage, this model is replaced with a voltage source induction model which is connected to a synchronous current-controlled converter. Finally, attention is given to the operational aspects of the drive which takes into account the maximum supply voltage and current constraints. In this context field weakening techniques are also discussed.

Modulation for Power Electronic Converters

At present, voltage source converters are mostly used in electrical drives. These converters utilize capacitors in the DC-link to store temporarily electrical energy. Switching the power electronic devices allows the DC voltage to be modulated which can result in a variable voltage and frequency waveform. The purpose of the modulator is to generate the required switching signals for these switching devices on the basis of user defined inputs. Modulation techniques for power electronic converters are discussed in this chapter.

Space Vector Based Transformer Models

This chapter considers an extension of the (single phase) ideal transformer (ITF) model to a two-phase space vector based version. The introduction of a two- phase (ITF) model is instructive as a tool for moving towards the so-called ideal rotating transformer “IRTF” concept, which forms the basis of machine models for this book. The reader is reminded of the fact that a two-phase model is a convenient method of representing three-phase systems as discussed in Sect. 4.6 The development from ITF to a generalized two-inductance model, as discussed for the single phase model (see Chap. 3), is almost identical for the two-phase model. Consequently, it is not instructive to repeat this process here. Instead, emphasis is placed in this chapter on the development of a two-phase space vector based ITF symbolic and generic model.

Voltage Source Connected Synchronous Machines

The synchronous machine has traditionally been used for power generation purposes. For motor applications (when connected to the power grid), a synchronous machine is ideal when the operating speed must remain constant, i.e., independent of load changes. Starting up, however, needs special measures.

VOLTAGE SOURCE CONNECTED ASYNCHRONOUS (INDUCTION) MACHINES

The induction machine is by far the most commonly used machine around the globe. Induction machines consume approximately one-third of the energy used in industrialized countries. Consequently this type of machine has received considerable attention in terms of its design and application.

DIRECT CURRENT MACHINES

The genesis of the ideas required to build an electrical machine can be traced back to the discovery of electromagnetism by the Danish scientist Oersted in 1819–1820. Oersted discovered that a current in a wire could deflect a compass needle. Thus the connection between a current carrying conductor, a magnetic field, and a mechanical movement was established. A German chemist named Schweigger, who studied Oersted’s experiment, found that if the wire carrying the current was wound into a coil then the deflection of the magnet was greatly increased. The Professor of Chemistry at Cambridge, Cumming, coined the term “Galvanometer” for this configuration and used it as a current detector. At around the same time Ampere developed a theory to support the observations made about current carrying coils in wire. In 1825 Sturgeon found that putting an iron core in the coil increased the magnetic field strength considerably for the same current.

Pulse Width Modulation and Current Control for DC Drives

In this chapter we will look at some basic drive implementations with a DC machine as discussed in Sect. 10.4 Our aim is to arrive at generic models of all major drive components (excluding the DC machine which has already been discussed) which we can then transpose to a PLECS type environment in the tutorials at the end of this chapter. A central topic of this chapter is the so-called pulse width modulation (PWM) which is used to realize uni-polar and bipolar voltage control of converters.