Guanghai Gong

Comparative evaluation of three-phase high-power-factor AC-DC converter concepts for application in future More Electric Aircraft

A passive 12-pulse rectifier system, a two-level, and a three-level active three-phase pulsewidth-modulation (PWM) rectifier system are analyzed for supplying the dc-voltage link of a 5-kW variable-speed hydraulic pump drive of an electro-hydrostatic actuator to be employed in future More Electric Aircraft. Weight, volume, and efficiency of the concepts are compared for an input phase voltage range of 98-132 V and an input frequency range of 400-800 Hz. The 12-pulse system shows advantages concerning volume, efficiency, and complexity but is characterized by a high system weight. Accordingly, the three-level PWM rectifier is identified as the most advantageous solution. Finally, a novel extension of the 12-pulse rectifier system by turn-off power semiconductors is proposed which allows a control of the output voltage and, therefore, eliminates the dependency on the mains and load condition which constitutes a main drawback of the passive concept.

Comparison of Prediction Techniques to Compensate Time Delays Caused by Digital Control of a Three-Phase Buck-Type PWM Rectifier System

The digital control of a three-phase three-switch buck-type rectifier system is analyzed in this paper. Three main sources of time delays in the control loop can be identified for the implementation on a digital signal processor (DSP): 1) the delay time due to the sampling of the control quantities; 2) the one due to the calculation time of the DSP; and 3) the one due to the sample-and-hold function of the pulsewidth modulator. Using the buck-type system as an example, the influence of the time delay on the stability of the inner current control loop is discussed, and two prediction methods for time-delay compensation, i.e., a linear prediction and the Smith prediction, are comparatively evaluated. The control performance and the effect of the delay times and the prediction methods are shown by simulation results and through measurements on a 5-kW prototype.

Comparative evaluation of three-phase high power factor AC-DC converter concepts for application in future more electric aircrafts

A passive 12-pulse rectifier system, a two-level, and a three-level active three-phase PWM rectifier system are analyzed for supplying the DC voltage link of a 5 kW variable speed hydraulic pump drive of an electro-hydrostatic actuator to be employed in future more electric aircrafts. Weight, volume and efficiency of the concepts are compared for an input phase voltage range of 98 V to 132 V and an input frequency range of 400 Hz to 800 Hz. The 12-pulse system shows advantages concerning volume, efficiency and complexity but is characterized by a high system weight. Accordingly, the three-level PWM rectifier is identified as most advantageous solution. Finally, a novel extension of the 12-pulse rectifier system by turn-off power semiconductors is proposed which allows a control of the output voltage and therefore eliminates the dependency on the mains and load condition which constitutes a main drawback of the passive concept.

12-pulse rectifier for more electric aircraft applications

A high power density 10 kW three-phase 12-pulse rectifier is analyzed for applications in future more electric aircrafts. The experimental results, which are in good accordance with the theory, show high efficiency and low input current harmonics for a wide operating range. Furthermore, two novel rectifier topologies, which are formed by combining the passive 12-pulse rectifier with a boost stage on the DC side are proposed. This allows to guarantee a constant output voltage and/or to overcome the problem of the dependency of output voltage on the mains voltage amplitude and output power level.

A Comparative Study of Multicell Amplifiers for AC-Power-Source Applications

AC test power sources are essential for testing electric equipment that is ac-mains connected. Typically, linear power amplifiers (LPAs) are mainly employed as ac test sources because of their high fidelity and excellent dynamic behavior. However, these LPAs have very high losses in their output stages, which make the systems bulky and expensive due to the large heatsinks that are required. In recent years, two approaches have attracted popular interest to improve the efficiency of ac power sources. These are hybrid operation, i.e., combination of linear and switch mode, and multilevel switch-mode inverters. In this paper, three types of multilevel power amplifiers, based on hybrid or switching technology, are presented, namely: hybrid multicell amplifier (H-MCA), amplitude-modulated (AM) + pulsewidth-modulated (PWM) MCA (AP-MCA), and PWM MCA (P-MCA). For each of these topologies, the operating principle and control scheme are introduced. Finally, a 1-kVA laboratory prototype, which can realize all the three topologies, is built, and the measured performance based on this universal prototype are compared.

Novel Tracking Power Supply for Linear Power Amplifiers

Conventional linear power amplifiers (LPAs) show a high output voltage quality but are characterized by high power losses and/or low power density. Therefore, there is a growing interest in increasing the efficiency of LPAs, e.g., for the realization of high power testing voltage sources. In this paper, a high-frequency isolated boost-type tracking power supply (TPS) system is proposed for the conditioning of the input voltage of an LPA. The output voltage of the TPS is varied according to the voltage to be formed by the LPA so that the voltage drop across the power amplifier output transistors is reduced to low values. This results in a significant increase of the total system efficiency. The operating principle of the proposed system is described. A design method for the output filter using the power supply rejection ratio of the LPA is proposed. This method ensures that the amplifier output voltage has minimal switching frequency components. Furthermore, a control system design method is presented that ensures good performance in the control of the constant inductor current of the switch-mode tracking stage. Finally, the theoretical considerations are verified by measurements on a 1-kW laboratory prototype.

Novel hybrid 12-pulse boost-type rectifier with controlled output voltage

Novel hybrid 12-pulse line interphase transformer (LIT) rectifier systems with integrated single-switch or two-switch boost-type output stage that ensure a constant output voltage independent of mains and load conditions are proposed for supplying actuators of future more electric aircraft. The principle of operation, the dimensioning, and the system control are discussed. The theoretical considerations are experimentally confirmed for a 10 kW laboratory prototype. Finally, the single-and the two-switch system are comparatively evaluated concerning the level of input current ripple, power factor, and overall efficiency.

A multi-cell cascaded power amplifier

A multi-cell cascaded power amplifier with a high output voltage capability, wide load range and high bandwidth is presented in this paper. The cascaded power amplifier is formed by combining a low-voltage linear power amplifier in series with multiple inverter cells. Therefore the cascaded power amplifier combines the advantages of a linear power amplifier with the advantages of a switched mode power amplifier. A high output voltage and bandwidth of 20kHz is achievable using very simple modulation and feedback control design. The dc voltages for the inverter cells and linear power amplifier are provided by an isolated, bidirectional dc-dc resonant converter. The dimensioning and physical structure of a 1.2kW, plusmn400V cascaded amplifier is given, and shows that a compact, flat system design is possible. Finally, digital simulation results verify the theoretical analysis of the amplifier

Design, Control and Performance of Tracking Power Supply for a Linear Power Amplifier

Power amplifiers are widely used in consumer and industrial applications and are based on either a linear power amplifier or switch-mode power amplifier design. By combining the linear power amplifier with a switch-mode tracking power supply, a hybrid power amplifier is formed that maintains a high quality output while having a high efficiency. This paper presents a hybrid amplifier that is constructed with a novel boost-type tracking power supply and provides an excellent performance. A design method for the output filter using the power supply ratio rejection (PSRR) of the linear power amplifier is proposed. This method ensures that the amplifier output voltage has minimal switching frequency components as well as being able to quickly track changes in the output voltage. A control system design method is presented that ensures good performance in the control of the constant inductor current of the switch-mode tracking stage and a high rejection of output voltage disturbances. A laboratory prototype experimentally verifies the theoretical analysis

Control-oriented modeling and robust control of a three-phase buck+boost PWM rectifier (VRX-4)

The modeling and control of a three-phase, three-switch buck-type rectifier system with integrated boost output stage (VRX-4) is analyzed in this paper. A cascaded multi-loop control structure is presented that has the following features: constant output voltage for a wide input voltage range and step-wise changes of load; sinusoidal input currents in phase with the mains voltages that also remain sinusoidal in case of asymmetric mains conditions; and active damping of the input filter resonance. For the control design an equivalent DC-DC small-signal model of the converter is derived and verified by simulations and measurements. Based on this and the identification of the critical operating point the controllers for the inner DC current and outer voltage control loops are selected The stability of the closed loop system is discussed and the robust operation of the system is verified by measurements on a 5 kW prototype.