Control and PWM modulation scheme for dead-time compensation of CVCF inverters

The switching dead-time necessary in PWM inverters results in output distortions, and deteriorates the utilization of dc-link voltage. To solve these problems, the authors have developed an accurate dead-time effect mathematical model, and proposed a compensation scheme for grid-connected inverters. In this paper, a new voltage control and PWM modulation scheme is presented for the dead-time compensation of CVCF inverters. It consists of a PID voltage controller and a sliding mode controller (SMC). The PID controller operates in the linear areas; the SMC controller detects the dead-time nonlinear operations and operates for the dead-time compensation . In this control scheme, the PWM modulation gate drive is divided into three operation modes according to the SMC controller output. The unnecessary gate drive signals are removed and the counter side switch can be controlled up to truly 100% PWM duty ratio with a smooth transition between different modulation modes. The influence of switching dead-time can be eliminated almost completely. The proposed control scheme is verified by simulation results. The improvement of harmonic distortion, the minimization of delink voltage and the reduction of inductor ripple current are all confirmed by the simulation results. The comparison results between the conventional and the proposed control scheme are presented in this paper.INTELEC 2009 - 2009 International Telecommunications Energy Conference : Incheon, South Korea, 2009.10.18-2009.10.2

A novel PWM modulation and hybrid control scheme for grid-connected unipolar inverters

The purpose of this paper is to provide low cost, high power quality and high efficiency solutions for grid-connected inverters. Compared with bipolar switched inverters, unipolar switched inverters have the advantages of higher efficiency due to reduced switching frequency and low iron losses of inductor in output filter. However, unipolar inverters produce large harmonic distortion due to the dead-time effects. To address this issue and achieve higher efficiency, a new PWM modulation and a hybrid current control scheme is proposed. Firstly, according to the polarity of current reference, in each leg, the gate drive signal of positive or negative switch is removed, and the dead-time insertion is eliminated. With this modulation method, the inverter circuit operations are divided into six operation modes, and their mathematical models are derived. According to this mathematical model, a hybrid control scheme is proposed that consists of a PI controller and an open-loop controller. The PI controller operates in the linear areas, and the open-loop controller operates in the nonlinear areas. Several control rules are designed to realize smooth transition between different control modes. With this control scheme, firstly, the influence of dead-time can be eliminated, and the harmonic distortion can be greatly reduced. Without the influence of switching dead-time, the dc-link voltage can be minimized that will contribute to reduced switching losses and smaller ripple current. The proposed control scheme is verified with simulation and experimental results. The experimental test is implemented in a 10 kW single-phase grid-connected inverter that uses a DSP controller TMS320F2808. The reductions of conversion losses, low harmonic distortion and low ripple current are all confirmed in the experimental system. The comparisons between the conventional control scheme and the proposed scheme are presented in this paper.2011 IEEE Applied Power Electronics Conference and Exposition - APEC 2011 : Fort Worth, TX, USA, 2011.03.6-2011.03.1

A new approach to improve dynamic characteristics of digitally controlled buck-boost dc-dc converter

This paper presents a new digital control buck-boost dc-dc converter with bias model to improve dynamic characteristics. The buck-boost converter needs to respond appropriately to changing input voltage and load change with wide input voltage. This approach makes adjustment to the bias value by input voltage and output current. As a result, it is revealed that not only the dynamic characteristics but also static characteristics can be improved and it is effective for wide range input voltage.2010 International Symposium on Power Electronics, Electrical Drives, Automation and Motion (SPEEDAM 2010) : Pisa, Italy, 2010.06.14-2010.06.1

Accuracy digital control for boost dc-dc converter

This paper presents the accuracy digital control for the boost type dc-dc converter. The design of the A-D conversion timing and anti-aliasing filter\u27s cut-off frequency is discussed to realize the accurate regulation characteristics and good dynamic characteristics.INTELEC 2009 - 2009 International Telecommunications Energy Conference : Incheon, South Korea, 2009.10.18-2009.10.2

A new digital control for forward type multiple-output dc-dc converter

The purpose of this paper is to present a new digital control method of the forward type multiple-output dc-dc converter with both the P-I-D control and the static equation model. The dynamic characteristics of digital control dc-dc converter are improved as compared with the conventional one. As a result, it is seen that the forward type multiple-output dc-dc converter with a new digital control has a superior transient response compared with that of the conventional control. The overshoot of reactor current is improved 28%.INTELEC 2009 - 2009 International Telecommunications Energy Conference : Incheon, South Korea, 2009.10.18-2009.10.2

Emergency power supply using flywheel and doubly fed induction generator

An emergency power supply (EPS) using an induction generator with a fly-wheel energy storage is investigated. Two different exciting system for the wounded rotor winding have been investigated. The principles of the operation and experimental results are shown. The results of start-up and steady state condition indicate that the inverter rating of the doubly fed induction generator is reduced fairly.INTELEC 2009 - 2009 International Telecommunications Energy Conference : Incheon, South Korea, 2009.10.18-2009.10.2

A new digital control DC-DC converter with peak current -injected control

This paper presents a new digital control circuit which is able to detect the peak switch current of the high frequency switching dc-dc converter. In this proposed digital control circuit, the peak current-injected control is realized using the combination of the simple dual pulse width modulation analog-to-digital signal converter and the programmed delay circuit. In 100kHz digitally controlled dc-dc converter, it is seen in simulation that the proposed method has no overshoot of the output voltage and the convergence time that the output voltage is settled to steady-state is only 30μs. The difference between the transient time of the proposed circuit and that of the conventional method is an order of magnitude. Furthermore, the ratio of resolution of the DPWM generator against the output voltage is 0.27% and is satisfied to apply the commercial power supply unit.INTELEC 2008 - 2008 IEEE 30th International Telecommunications Energy Conference : San Diego, CA, 2008.09.14-2008.09.1

Developing of higher voltage direct-current power-feeding prototype system

High efficiency power feeding systems are effective solutions for reducing ICT power consumption of ICT equipment, such as routers and servers, or high efficiency cooling systems. We developed a higher voltage direct current (HVDC) power feeding system prototype. This system is composed of a rectifier, power distribution cabinet, batteries, and ICT equipment. The configuration is similar to a -48 V DC power supply system. The output of the rectifier is 100 kW, and the output voltage is 401.4 V. We describe the advantage of an HVDC power feeding system and show that its basic characteristics are stable.INTELEC 2009 - 2009 International Telecommunications Energy Conference : Incheon, South Korea, 2009.10.18-2009.10.2

A novel digital PID controlled dc-dc converter

This paper presents the relationship between the dynamic characteristics and sampling frequency of digitally controlled dc-dc converter with a novel control method. In the proposed method, the calculation process of P and I-D controls is parallel. The sampling interval and points for I-D control are same to the conventional method. However, the sampling point for P control is quickly. The A-D converter can sample the output voltage during the short interval because the calculation process of P control is very simple and to important for transient response. The only sample data near the turn-off timing of PWM pulse is used. The simulation and experiment results of the output voltage against the step change of the load and changing the P control sampling frequency are discussed. As a result, it is revealed experimentally that the good transient response is obtained.2010 International Symposium on Power Electronics, Electrical Drives, Automation and Motion (SPEEDAM 2010) : Pisa, Italy, 2010.06.14-2010.06.1

Dynamic characteristics of DC-DC converter with novel digital peak current-injected control

This paper presents the dynamic characteristics of the proposed digital control current mode de-de converter. In the proposed novel digital control circuit, the peak current-injected control is realized using the combination of the simple dual A-Dsignal converter and the programmed delay circuit. In 100kHz digitally controlled de-de converter, it is seen in simulation that the proposed method has no overshoot of the output voltage and the convergencetime that the output voltage is settled to steady-state is only 151J1S. The difference between the transient time of the proposed circuit and that of the conventionalmethod is an order of magnitude. Furthermore, the ratio of resolution of the DPWM generator against the output voltage is 0.27% and is satisfied to apply the commercial power supply unit.INTELEC 2009 - 2009 International Telecommunications Energy Conference : Incheon, South Korea, 2009.10.18-2009.10.2