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This paper presents a new dual loop control using novel vector product phase locked loop (VP-PLL) for a high power static var compensator (SVC) with three-level GTO voltage source inverter (VSI). From a simple dq-axis equivalent circuit obtained by circuit DQ-transformation method, steady-state analysis is achieved for maximum controllable phase angle αmax per unit current between AC source and switching function of inverter. In addition, the system parameters L and C are designed and thus transient analysis is made for open-loop transfer function. This paper proposes software VP-PLL for more accurate α control than conventional hardware PLL because αmax becomes very small in high power SVC. Therefore, the overall controller has dual loop structure of inner VP-PLL for synchronizing the phase angle with AC source and outer Q-loop for compensating reactive power of load. Finally, the usability of the proposed control method is verified through the experiment of 100kvar power capacity with both stand alone a...

A soft switching quasi-parallel resonant DC-link (QPRDCL) inverter with improved PWM capability has been recently presented. The circuit has the minimum voltage stress of the devices and provides the flexibility of selecting the on/off instants of the resonant link, resulting in improved PWM capability. In this paper, the operational principles and the detailed analysis of the QPRDCL inverter are presented for the resonant components design and the inverter control. An SVPWM with optimal vector sequence suitable for the QPRDCL inverter is also presented through the comparisons among five different modified space vector PWM (SVPWM) techniques classified by the voltage vector sequences. The performance of the selected optimal SVPWM is verified by the experimental results.

This paper proposes a new control method of a static var compensator (SVC) with a three-level inverter, to control reactive power with fast dynamics while maintaining the DC side capacitor voltage constant. First, using the circuit DQ-tranformation, a general and simple model of SVC with a three-level inverter is obtained, and DC and AC analyses are carried out to characterize the open-loop system. Based on the transfer function matrix of the system, modulation index control for reactive power compensation and phase angle control for DC side voltage regulation are designed. By inserting a feedforward path to the voltage regulation loop the modulation index is successfully decoupled from the capacitor voltage, whereby fast dynamics are achieved. The experimental results confirm the theoretical analyses and control method.

Comparative studies between harmonic elimination and optimal PWM strategies are given for high power three-level inverter feeding an induction motor. An effective PWM map construction method based on the valid region on the frequency modulation index plane is suggested. Thereby, an optimal map including asynchronous space vector PWM, harmonic elimination and optimal PWM method is generated covering all of the low, middle and high modulation index regions. The PWM map was designed for 1 MVA rated general purpose GTO inverter and implemented with a digital signal processor. Experimental results are presented for 10 kVA prototype. >

A recently proposed circuit P-Q transformation is used to analyze a three-phase controlled-current PWM rectifier. The DC operating point and AC transfer functions are completely determined. Most features of the power converter are clearly interpreted. They are: (1) the output voltage can be controlled from zero to maximum; (2) the system is equivalently an ideal current source in the steady state; (3) the system can be described as linear circuits; and (4) the input power factor can be arbitrarily controlled within a certain control range. >

A new control scheme named optimum quantum sequence control (OQSC) which always minimizes the output voltage ripple of the quantum series resonant converter (QSRC) for all possible sequences is proposed. This control scheme is so general that it is irrelevant to all circuit conditions such as magnitudes of circuit elements as well as input/output voltage so far as it is operating in the continuous conduction mode (CCM). Furthermore, the dynamic range of QSRC is much extended by the OQSC. This feature is verified by simulations and experiments with good agreements. >

A multilevel PWM voltage source inverter, especially a five-level one, is introduced to obtain a static var compensator (SVC) as a large scale power source. The multilevel inverter has many advantages, such as better utilization of the switching devices, lower switching frequency at each semiconductor switch and reduced harmonics. In this paper, the SVC with five-level inverter is modelled using circuit DQ transformation and completely analysed including DC and AC characteristics. It is also pointed out that the modulation indexes depend on the values of the DC side capacitors to meet the DC side voltage balancing, Finally, through the experimental results from a 5kVA SVC, the validity of the analyses and the feasibility of the var compensation system are shown for high power applications.

A soft switched space vector PWM inverter is developed using new parallel resonant DC-link (PRDCL). This PRDCL can operate on variable DC-link pulse position and width resulting in enhanced PWM capability, which is superior to other resonant DC-links. A new space vector algorithm is presented suitable for this PRDCL inverter. The suggested algorithm is able to eliminate narrow PWM pulses that impede DC-link operation. This PWM control, however, requires complex and precise timing sequences in relation to PRDCL operation, which is nicely solved by adopting a new programmed controller with a buffer and a programmable timer.

A model based on practical switches with finite turn-on, turn-off, delay, storage, and reverse recovery times is proposed. The effects of switching on the state equation, system stability, DC gain and efficiency are shown for the boost, buck, and buck-boost converters. The effect of current-based switching-time variation on system stability effect, and the effect of average duty cycle variation on system stability is considered. DC gains of the boost and buck-boost converters are shown to be greatly degraded by switching loss. It is also shown that no additional resistance is generated by switching, in contradiction to previous work. It is found that the buck converter is superior to the others from the viewpoints of systems stability and DC gain, and the efficiencies of all the converters are maximized when the DC gain is close the unity. Previous results are improved and unified using state-space modeling. Analysis results are very simple in spite of the complex switching waveforms. This modeling approach is believed to be very useful for the high-frequency or high-power applications where switching effects become dominant. >

A high-performance induction motor (IM) drive which is different from field-oriented control (FOC) is presented. In this drive, the rotor flux and the stator current are simultaneously controlled. The drive has the characteristics of good dynamics and fast transient response. Implementation of this drive is very simple compared with the FOC. Although the drive is robust against the rotor resistance variation, a rotor resistance compensation method for controlling the output torque accurately is presented. Simulation results show that the drive scheme can be used for applications requiring good dynamic performance. >

The circuit D-Q transformation is used to analyze a three-phase, current-source, pulse-width modulated (PWM) rectifier. The DC operating point and AC transfer functions are completely determined. Most features of the converter are clearly interpreted. The output voltage can be controlled from zero to maximum. The system is equivalently an ideal current source in the steady state and can be described in terms of linear circuits. The input power factor can be arbitrarily controlled with a certain control range. >

A soft-switched space vector pulse-width-modulated (PWM) inverter is developed using a novel parallel resonant DC link (PRDCL). This PRDCL can operate on variable DC link pulse position and width, resulting in enhanced PWM capability, which is superior to that of other resonant DC links. A space vector algorithm suitable for this PRDCL inverter is presented. The algorithm eliminates narrow PWM pulses which impede DC link operation. This PWM control, however, requires complex and precise timing sequences in relation to PRDCL operation, which is accomplished by adopting a new programmed controller with a buffer and a programmable timer. >

A new type of dual output zero voltage switched (ZVS) DC/DC power converter is proposed. One output is dependent on the effective duty ratio and the other is largely dependent on the switching frequency. Two completely regulated outputs are obtained with only one bridge circuit by combining the different configurations of secondary output. Using ZVS technique, switching loss can be reduced to quite low at several hundred kHz. >

This paper presents a new dual loop control using novel vector product phase locked loop (VP-PLL) for a high power static VAr compensator (SVC) with three-level GTO voltage source inverter (VSl). Through circuit DQ-transformation method, a simple DQ-axis equivalent circuit is obtained. From this, DC analysis is carried out to obtain maximum controllable phase angle /spl alpha//sub max/ per unit current between the three phase source and the switching function of the inverter, and AC open-loop transfer function is given. Because /spl alpha//sub max/ becomes small in high power SVC, this paper proposes VP-PLL for more accurate a control. As a result, the overall control loop has dual loop structure, which consists of inner VP-PLL for synchronizing the phase angle with source and outer Q-loop for compensating reactive power of load. Finally, the validity of the proposed control method is verified through the experimental results.

Rotor time constant is essential for high performance motor control in the induction motor. A simple and exact measurement method of rotor resistance and rotor time constant of induction motor is proposed. A DC current is injected to the magnetizing inductance, and then the magnetizing current is discharged to the rotor, so that the voltage is taken at the stator. Then the measured stator voltage has information of rotor time constant as a function of magnetizing current. In this paper, rotor time constant obtained from conventional method and the proposed method are compared. The accuracy of the measurement is tested with a vector controller by a linear relation between the input torque command and output torque at steady state. >

In this paper, a new type of PWM series resonant converter is proposed. One pole of the proposed converter is switching at zero-current and the other is switching at zero-voltage. By introducing an auxiliary inductor, zero-voltage switching is possible even at no load. The proposed converter is suitable for a high-voltage DC/DC converter because the voltage stresses of switching devices are minimized. >

A modified output control scheme for the series resonant converter (SRC) is proposed. In this scheme, quantized output voltage is obtained by quantum duty control and one last unit voltage is continuously adjusted by phase angle control during a half resonant cycle period. The proposed control method suggests a way to eliminate the stepped discontinuity problem in the output voltage of quantum control without degrading the performance. Based on the steady-state analysis, an optimum quantum sequence with greatly reduced output voltage ripple is given. >

This paper presents a new active power filter connected in series with a bank of capacitors having no tuned filters and no resonance problem related with harmonic loads. A capacitor of appropriate small size is determined considering much small power capacity of the converter compared with load power. Through frequency analysis of the system, a dual loop controller is designed for eliminating harmonics of load current and reducing the fundamental voltage component of the converter. Finally, the performance of the presented scheme is confirmed using simulation with 10 kVA 6-pulse load and experimental results with 1 kVA 6-pulse load.

This paper proposes a new control method of static VAr compensator (SVC) with a three-level inverter to control reactive power with fast dynamics while maintaining DC side capacitor voltage constant. Firstly, using the circuit DQ-transformation, a general and simple model of SVC with a three-level inverter is obtained, and DC and AC analyses are carried out to characterize the open-loop system. Based on the transfer function matrix of the system, modulation index control for reactive power compensation and phase angle control for DC side voltage regulation are designed. By inserting feedforward path to the voltage regulation loop the modulation index is successfully decoupled from the capacitor voltage whereby fast dynamics are achieved. The experimental results confirm the theoretical analyses and control method. >

The static and dynamic characteristics of a practicable step-up nine-switch matrix convertor under the control strategy proposed by Venturini are analysed fully by the recently presented circuit DQ transformation technique and signal flow graphs. The step-up nine-switch matrix convertor consists of nonideal voltage and current sources, such as occur in practical inductance and capacitance filters. Several static and dynamic features of the convertor, such as steady-state input/output voltage gain, input power factor and transient response, are predicted analytically and verified by computer simulations. The signal flow graph is adopted to solve the complex fourth-order equivalent convertor and thus the nine-switch matrix convertor is analysed fully in explicit form.

Detailed analysis and optimum design of the commutating circuit of the recently proposed DC-side commutated current-source inverter are given. Analysis was performed for each topology mode during a step transition interval under certain assumptions and using various normalised quantities. Using the analysis results, optimum design of the commutating circuit was studied with an aim to maximising the turn-off time with a minimum commutating energy. Experimental results showed reasonably good agreement with the theoretical results.