C.-H. Chang

A fuzzy-logic-controlled single-stage converter for PV-powered lighting system applications

This paper presents a fuzzy-logic-controlled single-stage power converter (SSC) for photovoltaic (PV)-powered lighting system applications. The SSC is the integration of a bidirectional buck-boost charger/discharger and a class-D series resonant parallel loaded inverter. The designed fuzzy logic controller (FLC) can control both the charging and discharging current, and can improve its dynamic and steady-state performance. Furthermore, a maximum power point tracker (MPPT) based on a perturb-and-observe method is also realized to effectively draw power from PV arrays. Both the FLC and the MPPT are implemented on a single-chip microprocessor. Simulated and experimental results obtained from the proposed circuit with an FLC have verified the adaptivity, robustness and feasibility.

Single-stage converters for photovoltaic powered lighting systems with MPPT and charging features

This paper proposes single-stage power converters (SSCs) for application in photovoltaic powered lighting systems. The synchronous switch technique is employed to synthesize the SSCs which can fulfill maximum power point tracking, battery charging, discharging and lamp ballasting features. Several typical SSCs are discussed in the paper. One of the proposed SSCs, which is the integration of a buck-boost charger/discharger and a class-D series resonant parallel loaded inverter, is analyzed and designed. Both pulse-width modulation and variable-frequency controls are used to govern the system. The controller is implemented on a single-chip microprocessor. Simulated and experimental results of the proposed system for driving sixteen GE TBX 26 W fluorescent lamps are used to verify the theoretical prediction and feasibility. The proposed system has the merits of lower cost, more compact size and possibly achieving higher reliability over conventional systems.

A fuzzy logic controlled single-stage converter for PV powered lighting system applications

This paper presents a fuzzy logic controlled single-stage power converter (SSC) for photovoltaic powered lighting system (PPLS) applications. The SSC is the integration of a bidirectional buck-boost charger/discharger and a class-D series resonant parallel loaded inverter. The designed fuzzy logic controller (FLC) can control both the charging and discharging current, and improve its dynamic and steady state performance. Furthermore, a maximum power point tracking (MPPT) scheme based on a perturb-and-observe method is also realized to effectively draw power from photovoltaic arrays. Both of the FLC and the MPPT are implemented on a single-chip microprocessor. Simulated and experimental results obtained from the proposed circuit with an FLC have verified the adaptivity, robustness and feasibility.

Single-stage converters for PV lighting systems with MPPT and energy backup

Single-stage converters (SSCs) are proposed for applications of photovoltaic powered lighting system (PPLS). The synchronous switch technique is employed to develop the SSCs which can fulfill maximum power point tracking (MPPT), battery charging, discharging, and lamp ballasting features. Several typical SSCs are discussed. One of the proposed SSCs, which is the integration of a buck-boost charger/discharger and a class-D series resonant parallel loaded inverter, is analyzed and designed into a PPLS. Both pulsewidth modulation (PWM) and variable-frequency controls are used to govern the system operation. The controller is implemented on a single-chip microprocessor. Simulated and experimental results of the proposed system for driving up to sixteen GE TBX 26 W fluorescent lamps are used to verify the theoretical prediction and feasibility. The proposed system has a simple configuration, as well as a zero voltage switching (ZVS) feature, and can achieve the same functions as those in conventional systems when abrupt insolation changes do not occur frequently. These result in the inherent merits of lower cost, more compact size and possibly achieving higher reliability over conventional systems.

A multi-function photovoltaic power supply system with grid-connection and power factor correction features

A conventional photovoltaic (PV) inverter system with grid-connection feature is usually composed of a full-bridge inverter and a microprocessor. The PV system is idle when there is no insolation (at nighttime). To optimize the use of the existing components, this paper proposes a multi-function PV power supply system with grid-connection, power factor correction and lamp-driving features. With the synchronous switch technique, pulse-width modulation, additional relays and components, an ordinary inverter system can function alternately as an electronic ballast with power factor correction at nighttime. Thus, the power switches, driving circuits and the microprocessor in such a multi-function system are optimally used. Computer simulation results and experimental measurements have verified the feasibility of the proposed system.

Power loss analysis of grid connection photovoltaic systems

This paper presents power loss analysis of grid-connection PV systems, based on the loss factors of double line-frequency voltage ripple, fast irradiance variation, fast dc load variation, non-uniform solar cell characteristic, and limited operating voltage range. These loss factors will result in power deviation from the maximum power points (MPP). In the power loss analysis, both single-stage and two-stage grid connection PV systems are considered. The effects of these loss factors on two-stage grid-connection PV systems are insignificant due to an additional maximum power point tracker (MPPT), but it will reduce the system efficiency typically about 3 %. The power loss caused by these loss factors in single-stage grid-connection PV systems is also around 3 %; that is, a single-stage grid-connection PV system has the merits of saving components and reducing cost, while does not scarify overall system efficiency. Simulation results with a MATLAB software package are presented to confirm the analysis.

Power loss analysis of photovoltaic dc distributed generation systems with grid-connection

This paper presents power loss analysis for PV dc-distributed systems based on the loss factors of double line-frequency voltage ripple (DLFVR), fast irradiance variation + DLFVR, fast dc load variation + DLFVR, limited operating voltage range + DLFVR, and overall loss factor combination. These loss factors will result in power deviation from the maximum power points. In the paper, both single-stage and two-stage grid-connected PV systems are considered. All of the effects on a two-stage system are insignificant due to an additional maximum power point tracker, but the tracker will reduce the system efficiency typically about 2.5 %. The power loss caused by these loss factors in a single-stage grid-connected PV system is also around 2.5 %; that is, a single-stage system has the merits of saving components and reducing cost, while does not penalize overall system efficiency in dc-distribution applications. Simulation results with the MATLAB software package and experimental results have confirmed the analysis.

A 1/spl phi/3W grid-connection PV power inverter with partial active power filter

This paper presents a single-phase three-wire (1/spl phi/3W) grid-connection photovoltaic (PV) power inverter with a feature of a partial active power filter (PAPF), which can not only deal with PV power but can filter current harmonics and improve power factor. Once the processed power exceeds the switch ratings, the inverter can reduce its output reactive power and harmonic power, while still can supply the maximum real power generated by the PV arrays. In derivation of control laws, a limit circle is defined to confine the output power of the inverter. To determine the power that the inverter can process, a criterion is proposed to find reactive power, which can avoid complex detections of phase angle and magnitude of the fundamental component of a nonlinear load current. Simulation results and experimental measurements have verified the proposed algorithm and the feasibility of the inverter.

Current improvement for a 3 ⊘ bi-directional inverter with wide inductance variation

This paper presents current improvement for a 3⊘ bi-directional inverter with wide inductance variation. A bi-directional inverter fulfilling grid connection and rectification with power factor correction has been designed and implemented in the laboratory. With a digital predictive current control, the inverter can accommodate wide inductance variation, improving current distortion in high power applications significantly. However, under low current levels, inductor currents have serious distortion. To improve current distortion, this paper presents four attempts, including mid-point current sampling, smooth region transition, current interleaving, and duty splitting. Theoretical analysis and experimental results are presented to verify the discussion.

SVPWM-based D-Σ digital control for 3ϕ grid-connected inverter with wide inductance variation

This paper presents an SVPWM-based division-summation (D-E) digital control for a three-phase grid-connected inverter with wide inductance variation. The proposed D-E approach summarizes all of the individual inductor-current variations over one switching cycle to derive control laws directly, which can overcome the limitation of d-q transformation. The inverter with this control can achieve the functions of grid connection, rectification with power factor collection, and STATCOM by taking into account wide filter-inductance variation and grid-voltage distortion, reducing core size significantly. The control laws for achieving the desired functions are derived in detail and they are expressed in general forms for readily software programming. In the design and implementation, the inductances corresponding to various inductor currents were measured at the start-up and stored in the microcontroller for scheduling loop gain cycle by cycle. Experimental results from an 8 kVA 3φ inverter have confirmed the analysis and discussion of the proposed control approach.