Fang Lin Luo

Speed nonlinear control of DC motor drive with field weakening

In this paper, we show that it is feasible to apply nonlinear MIMO feedback linearization technique to a separately excited DC motor system that is operated in high-speed field-weakening regime. Load-adaptive and sensorless control techniques to improve dynamic speed performance are proposed and compared. Also, application results are presented to verify theoretical ones.

Advanced PM brushless DC motor control and system for electric vehicles

Electric vehicles may be one of the main future transportation trends from the next decade due to their low-pollution and high efficiency. Reviewing the papers in the literature we can see that the best motive equipment is permanent magnet brushless DC (PM BLDC) motor. Many papers discuss the power supply for PM BLDC motors. This paper introduces a novel digital signal processor (DSP) controlled pulse width modulated (PWM) chopper to drive a PM BLDC motor. The main power supply unit is a chopper consisting of three power switches, which has a simple circuit and low-cost topology with less power losses. A comprehensive analysis on the principle of operation, design considerations and control algorithms implemented are described in this paper. The analysis also includes simulation and experimental results based on the prototype developed. The main objective is to achieve cost minimization and a simple structure drive system that is suitable for electric vehicle applications.

Analysis of a cascade double /spl Gamma/-CL current source resonant inverter

The current source resonant inverter (CSRI) is the heart of many systems and equipment, e.g. uninterruptible power supplies (UPS) and high-frequency annealing (HFA) equipment. Many topologies shown in open literature are the series resonant converters (SRC) and parallel resonant converters (PRC) that consist of two or three energy storage elements. However, they have a number of limitations. These limitations of two- or/and three-element resonant topologies can be overcome by adding a fourth energy storage element. This paper introduces a cascade double /spl Gamma/-CL CSRI, which has very smooth waveforms of output voltage and current, and very low total harmonic distortion (THD) value. It effectively reduces the power losses and largely increases the power transfer efficiency. Simulation and testing results verified the design and analysis.

Closed-Loop Control for Digital Power Electronics

This chapter discusses closed-loop control. All existing converters applied in industrial applications are stable, and they have been working in variable state—stable but shifted—because of the interferences. Closed-loop control is necessary to keep converters working in steady state to satisfy the industrial requirements. Closed-loop control is applied in most industrial applications to keep converters working in steady state to satisfy the industrial requirements. Traditionally, the proportional-plus-integral (PI) control and proportional-plus-integral-plus-differential (PID) control are very popular in closed-loop control systems. PI and PID controllers can be constructed by analog form using operational amplifier (OA). The chapters talks about PI control for AC/DC rectifiers, PI control for DC/AC inverters and AC/AC—AC/DC/AC—converters, and PID control for DC/DC converters.

Applications in Other Branches of Power Electronics

The digital-control theory is applied in other branches of power electronics, such as, power factor correction (PFC), static compensation (STATCOM), flexible AC transmission system (FACTS), reactive power (VAr) compensation, and power quality control (PQC). This chapter describes digital-control theory that is being applied in some branches of power electronics. Reactive power has no real physical meaning, but is recognized as an essential factor in the design and good operation of power systems. VAr compensation or control is an essential part in a power system to minimize power transmission losses, to maximize power transmission capability, and to maintain the supply voltage. The chapter talks about power-systems analysis, power-factor correction, and static compensation (STATCOM). The staircase PWM is widely used in STATCOM because GTOs with lower-switching frequency are employed as switches in such applications of high power and high voltage. The vector control based on synchronous frame transform has been used successfully in STATCOM to regulate reactive power and reduce negative-sequence component of the bus voltage. This chapter deals with how the vector control and staircase modulation are combined to reach the control aims.

Energy Factor ( EF ) and Sub-sequential Parameters

Switching power circuits, such as power DC/DC converters, power PWM DC/AC inverters, soft-switching converters, resonant rectifiers and soft-switching AC/AC matrix converters, have pumping-filtering process, resonant process, and/or voltage-lift operation. These circuits consist of several energy-storage elements. They are likely an energy container to store certain energy during performance. The stored energy will vary if the working condition changes. EF is a new concept in power electronics and conversion technology, which thoroughly differs from the traditional concepts, such as power factor (PF), power transfer efficiency (^), total harmonic distortion (THD) and ripple factor (RF). EF and the other sub-sequential parameters can illustrate the system stability, reference response, and interference recovery. This investigation is very helpful for system design and DC/DC converters characteristics foreseeing.

Basic Mathematics of Digital Control Systems

Publisher Summary Digital control systems are described by digital control theory. Some necessary fundamental knowledge on digital control theory is introduced in this chapter as mathematical tools. As computers operate on digital signals, the need for handling digital signals increased proportionally. High-speed processing capabilities of modern computers attracted applications that make use of digital signals, which further accelerate the development of the use of digital signals. Therefore, digital control systems have gradually become more prominent in todays industries. Digital control systems have many advantages over analog control systems. Digital control systems are smaller in size and consume less power than their analog control counterparts. Digital control systems are also highly reproducible and have virtually unlimited programmability. The greatest advantage of digital technology is the flexibility that allows modification to be done. Digital computers are used for simulation and computation of control systems dynamics for analysis and design of complex control-systems. It eased the hassle of laboratory work that is tedious and expensive. Computer simulations also allow the designers to check or present the results obtained by analytical means. In addition, digital computers can also be used as controllers or processors.

Chapter 7 – Digitally Controlled DC/DC Converters

Publisher Summary All power DC/DC converters are treated as a second-order-hold (SOH) element in digital control systems. Power DC/DC converters have plenty of topologies, and the corresponding conversion technique is a big research topic. There are different types of converters, and this chapter focuses on the function of different types of converters. The chapter deals with mathematical modeling for power DC/DC converters. Most power DC/DC converters consist of multiple—more than two—passive energy-stored components, and in traditional method, they have higher-order transfer function. The chapter also talks about multi-element resonant power converters (RPC). The sixth-generation converters work in the resonant state to reduce the power losses. The technique was created in the 1980s and was popular in the 1990s. Depending upon the number of the passive components, the few categories of converters are two-element RPC, three-element RPC, four-element—2L-2C—RPC. All RPCs work in a forced resonant state.

Mathematical Modeling of Digital Power Electronics

All switching circuits work in the discrete-time state; therefore, they have to be described by digital control theory rather than analog control. This chapter mainly describes the mathematical modeling for different types of converters in digital control. The chapter differentiates between analog and digital control systems. The chapter discusses zero-order hold (ZOH) for AC/DC controlled rectifiers, traditional modeling for AC/DC controlled rectifiers, and ZOH for AC/DC controlled rectifiers in digital control. It focuses on first-order transfer function for DC/AC PWM inverters and second-order transfer function for DC/DC converters. The chapter also deals with first-order transfer function for AC/AC—AC/DC/AC—converters.

Digitally Controlled DC/DC Converters

All power DC/DC converters are treated as a second-order-hold (SOH) element in digital control systems. Power DC/DC converters have plenty of topologies, and the corresponding conversion technique is a big research topic. There are different types of converters, and this chapter focuses on the function of different types of converters. The chapter deals with mathematical modeling for power DC/DC converters. Most power DC/DC converters consist of multiple—more than two—passive energy-stored components, and in traditional method, they have higher-order transfer function. The chapter also talks about multi-element resonant power converters (RPC). The sixth-generation converters work in the resonant state to reduce the power losses. The technique was created in the 1980s and was popular in the 1990s. Depending upon the number of the passive components, the few categories of converters are two-element RPC, three-element RPC, four-element—2L-2C—RPC. All RPCs work in a forced resonant state.