Paolo Tenti

General-purpose fuzzy controller for DC-DC converters

In this paper, a general-purpose fuzzy controller for DC-DC converters is investigated. Based on a qualitative description of the system to be controlled, fuzzy controllers are capable of good performances, even for those systems where linear control techniques fail, e.g., when a mathematical description is not available or is in the presence of wide parameter variations. The presented approach is general and can be applied to any DC-DC converter topologies. Controller implementation is relatively simple and can guarantee a small-signal response as fast and stable as other standard regulators and an improved large-signal response. Simulation results of buck-boost and Sepic converters show control potentialities.

AC/DC/AC PWM converter with reduced energy storage in the DC link

The paper introduces the family of quasi-direct converters, i.e., forced-commutated AC/DC/AC power converters including small energy storage devices in the DC link. In particular, the case of the three-phase to three-phase quasi-direct power converter is considered. Since energy storage minimization calls for instantaneous input/output power balance, a proper control strategy is needed. The paper describes a simple and effective control technique which also provides high-power factor and small distortion of the supply currents. After a discussion of the general properties of quasi-direct power converters, design criteria of both power and control sections are given, and experimental results of a 2-kVA prototype are reported. >

General-purpose sliding-mode controller for DC/DC converter applications

A general-purpose sliding-mode controller is described, which can be applied to most DC-DC power converter topologies. It has the same circuit complexity as standard current-mode controllers, but provides extreme robustness and speed of response against supply, load, and parameter variations. Moreover, contrary to other sliding-mode techniques, the proposed solution features constant switching frequency in the steady state, synchronization to external triggers, and absence of steady-state errors in the output voltage.<<ETX>>

Three-Phase AC/DC PWM Converter with Sinusoidal AC Currents and Minimum Filter Requirements

A pulsewidth modulation (PWM) control technique suitable for fully controlled three-phase ac/dc converters is analyzed, which gives sinusoidal input currents and ideally smoothed dc voltage. The technique allows four-quadrant operation and full-range control of the input power factor. An extension to a simplified converter scheme, capable of one-quadrant operation, is also considered. Operation of the converter is analyzed under both ideal and actual conditions. Control implementation and design criteria are discussed and experimental results are reported.

Predictive digital control of power factor preregulators with input voltage estimation using disturbance observers

The paper presents a fully digital control of single-phase boost power factor preregulators (PFPs) based on inductor (or switch) current and output voltage measurements. Input voltage sensing is avoided using a disturbance observer, which provides a waveform proportional to the rectified input voltage. The proposed solution is based on a multiloop structure for PFPs with an internal deadbeat current control and a conventional outer voltage control, possibly with fast dynamic response. The resulting control algorithm is simple, accurate, and robust with respect to parameter mismatch. The digital control has been implemented both in a field programmable gate array and in a digital signal processor (TMS320F2812), to test the proposed algorithm with different control delays. Experimental results on a single-phase boost PFPs show the effectiveness of the proposed solution.

High Efficiency Quasi-Resonant DC Link Three-phase Power Inverter for Full-Range PWM

A quasi-resonant dc link soft switching inverter is presented, capable of PWM operation. It requires only two additional switches, and allows loss limitation in the resonant circuit. The modulation method adopted is able to perform true PWM operation at any modulation index. Simulated and experimental results are reported, confirming the effectiveness of the proposed solution.

Conservative Power Theory, a Framework to Approach Control and Accountability Issues in Smart Microgrids

Smart microgrids offer a new challenging domain for power theories and compensation techniques, because they include a variety of intermittent power sources, which can have dynamic impact on power flow, voltage regulation, and distribution losses. When operating in the islanded mode, low-voltage smart microgrids can also exhibit considerable variation of amplitude and frequency of the voltage supplied to the loads, thus affecting power quality and network stability. Due to limited power capability in smart microgrids, the voltage distortion can also get worse, affecting measurement accuracy, and possibly causing tripping of protections. In such context, a reconsideration of power theories is required, since they form the basis for supply and load characterization, and accountability. A revision of control techniques for harmonic and reactive compensators is also required, because they operate in a strongly interconnected environment and must perform cooperatively to face system dynamics, ensure power quality, and limit distribution losses. This paper shows that the conservative power theory provides a suitable background to cope with smart microgrids characterization needs, and a platform for the development of cooperative control techniques for distributed switching power processors and static reactive compensators.

Digital Control of Single-Inductor Multiple-Output Step-Down DC–DC Converters in CCM

This paper investigates the application of digital control for non-isolated single-inductor multiple-output step-down dc-dc converters operating in continuous-conduction mode. The accurate and independent control of each output requires a sophisticated digital control architecture so as to minimize the cross-regulation problem. The adopted control includes a separate regulation for common-mode and differential-mode output voltages. Due to the differential-mode control loop dependence on the load current, a variable-gain functional block has been investigated; this provision keeps the differential-mode loop gain constant under different load conditions. Moreover, a nonlinear evaluation of the common-mode voltage has been investigated in order to improve the system dynamic response to asymmetrical load changes. Even if aimed at an integrated solution, experimental verifications have been performed using discrete components, implementing the digital control in a field-programmable gate array. Simulation results on a three-output converter and experimental results on dual-output converter (Vin = 2.5 4divide5 V, Vo1 = Vo2 = 0.9divide1.5 V, and Ioperp = Io2 = 0 4divide0.6 A) confirm the proposed analysis.

A synchronized resonant DC link converter for soft-switched PWM

A resonant DC link scheme for soft-switched inverters is proposed, where the link oscillation can be synchronized with inverter modulation. The scheme is able to operate with reduced commutation losses at a high switching frequency. Synchronization compatibility allows the development of suitable modulation techniques, which ensure improved waveform accuracy. The system performance and control strategies are verified both by simulation and by experimental tests, confirming the effectiveness of the proposed scheme.<<ETX>>

General-purpose fuzzy controller for DC/DC converters

In this paper, a general-purpose fuzzy controller for DC-DC converters is investigated. Based on a qualitative description of the system to be controlled, fuzzy controllers are capable of good performances even for those systems where linear control techniques fail, e.g. when a mathematical description is not available or in the presence of wide parameter variations. The presented approach is general and can be applied to any DC-DC converter topologies. Controller implementation is relatively simple and can guarantee a small-signal response as fast and stable as for other standard regulators and an improved large-signal response. Simulation results of buck-boost and Sepic converters show control potentialities.<<ETX>>