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Traditional dimming methods require excessive amount of external components and connection pins of ICs; therefore limit the possibility of making compact dimming fluorescent ballasts. By going over these conventional methods and introducing a new dimming method, this paper provides a solution for making highly integrated dimmable fluorescent ballasts, minimizing usage of external components and connector...
This paper presents an improved controller for parallel connected single-phase UPS inverters in distributed generation application areas. The proposed control strategy needs only locally measurable feedback signals with communicationless between each inverter. It also shows how the improved adaptive droop method can be easily adapted to account for the operation of parallel inverters, providing good...
In this paper, a small signal model of hysteretic current mode control with variable frequency and fixed hysteretic band is presented, based on three terminal averaged switch cell of buck converter in continuous current mode. This model reveals that the averaged current is the control target of hysteretic control. And phase lag of current loop with high switching frequency is quite small that makes...
A crucial component of a grid-connected converter system is the phase-locked loop (PLL) that synchronizes the control to the grid voltage. Accurate, fast responding PLLs are required to provide phase angle and frequency measurements of the grid voltage for control and protection purposes. This paper proposes novel feedback mechanisms using the estimated frequency and phase in single-phase PLLs (in...
This paper proposes a set of sequence-decoupled resonant controllers constructed with an easy-to-implement structure. It shows that either positive-sequence or negative-sequence components of three-phase unbalanced AC signals can be regulated individually in the stationary frame, while conventional and widely used resonant controllers cannot separately cope with these two sequences. Consequently,...
Constant frequency inverters, such as the 60 Hz 120 V UPS or the 208 V 3-phase power system may be paralleled with the utility for backup power or paralleled with similar supplies to increase output capabilities. Previous research has addressed paralleling 3-phase 4-wire inverters. This paper will examine the parallel operation of 2 similar 3-phase 4-wire inverters using repetitive control. Repetitive...
In this paper, a new method to mitigate the common-mode (CM) voltage in neutral point clamped (NPC), three-level converters is proposed by analyzing the voltage vectors and related CM voltages. Currently, only 19 of 27 available voltage vectors are used in order to reduce the amplitude of CM voltage to be one sixth of the dc-link voltage. This is achieved by adding a constraint to the universal, multilevel...
The conditions for limit cycle oscillations in digitally controlled resonant converters were explored theoretically and tested by simulations and experiments. The analytical analysis reveals that, similar to the case of digital PWM control, limit cycles of such systems will occur when the LSB of the control is changing the output by a value that is larger than the resolution of the ADC. However, unlike...
Current regulation plays a key role in modern power electronic AC conversion systems. The most obvious strategy is to use a simple closed loop PI regulator. However it is well known that this approach cannot achieve zero steady state error because of the instability that inevitably occurs as the PI gains are increased to reduce this error. Linear analysis identifies that an AC load controlled by a...
The combination of non-linear control and linear control proposed provides very fast transient response (voltage step from 1 V to 1.5 V in 2 mus). This non-linear control is based on hysteretic control of the Cout current. This system is very sensitive to effects like aging, temperature, input and output voltage variation, etc., that modify the switching frequency. This paper proposes a frequency...
This paper proposes a novel fixed-frequency sliding mode (SM) controller of buck converters in CCM (continuous conduction mode), which almost holds the advantage of robustness and fastness of SM control. The design method of a new SM controller for buck converter is given. Simulation and experimental results verify the validity and feasibility of the fixed-frequency modulation method in Buck converter...
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