A dynamic process for reaching the maximum power point of a variable power source such as a solar cell is introduced. The process tracks maximum power nearly cycle-by-cycle during transients. Information from the natural switching ripple instead of external perturbation is used to support the maximizing process. The method is globally stable for DC-DC power converters, provided that a switching action is present. A prototype boost power converter that uses this method for control can follow power transients on time scales of a few milliseconds. This performance can be achieved with a simple analog control structure, which supports power processing with minimum loss.

Dynamic maximum power point tracker for photovoltaic applications

A maximum power point tracker for photovoltaic arrays is presented. Components are optimized for weight/power-loss tradeoff in a solar-powered vehicle, resulting in over 97% efficiency. The control circuit uses a robust auto-oscillation method. Measurement and multiplication of array voltage and current is shown to be unnecessary, and the control is based only on output current measurement. Multiple local maxima arising from partial shading of the solar array are discussed. >

A high-efficiency maximum power point tracker for photovoltaic arrays in a solar-powered race vehicle

A multilevel pulse-width modulated (PWM) single phase voltage-source inverter topology for photovoltaic applications is discussed in this paper. The use of the phase opposition (PO) carrier disposition multicarrier PWM switching technique for this topology is presented. Inverter switch control signals are derived. A 5-level and a 3-level PWM voltage waveform across the load is generated, for high and low modulation indexes respectively. Performance characteristics including total harmonic distortion for a range of operating conditions of the inverter are provided. Theoretical considerations discussed in this paper are supported with simulation and experimental results taken from a low power laboratory prototype.

A multilevel PWM inverter topology for photovoltaic applications

In this paper, the authors proposed a novel maximum power point controller, which not only can track the maximum power of an array quickly without perturbation and observation process but also can be implemented easily. The main idea is based on the graphical interpretation of the maximum power point as the intersecting point of two curves on the phase plane corresponding to the solution of two algebraic equations. In other words, the operating point is the intersecting point of the PV-array characteristic curve and the maximum power line. A circuit is constructed based on a boost circuit and a three phase full bridge inverter.

A fast maximum power point tracker for photovoltaic power systems

A novel type of solid-state ballast, which operates in the megahertz-range frequency, is presented in this paper. A circuit composed of a voltage-fed half-bridge inverter, a distributed constant line, and a parallel LC resonant circuit has been developed for this purpose. The high-intensity discharge (HID) lamp is connected to the output terminal of the inverter through the distributed constant line. Here, since the length of the line is adjusted to 1/4 of the propagation wavelength /spl lambda/, the output voltage of the voltage-fed inverter can be converted to a current source on the load side. Based on the experiment results, the ballast appears to be able to supply not only high voltage, but also constant current for ignition of the HID lamp. The experimental results from a prototype system are used to verify the theoretical procedure.

Megahertz operation of voltage-fed inverter for HID lamps using distributed constant line

The authors describe a control method for a resonant DC-DC converter in a small-scale photovoltaic system linked up with storage batteries. The converter is suitable for tracking control of storage battery charging. The control method and experimental results are presented. Optimum operation was achieved by the application of the improved control circuit presented. With this circuit, it is possible to implement tracking control for various intensities of solar radiation. >

New control method of resonant DC-DC converter in small scaled photovoltaic system

A new type of solid state ballast, which can provide the high-frequency power to high intensity discharge (HID) lamps without an acoustic resonance, is presented. A ballast is needed to lighten the HID images, and is expected to be small and stably operating. The ballast equipment is composed of an inverter circuit, having variable switching frequency, a series resonant circuit, and a starting capacitor of the HID lamps. The operating characteristics of the ballast circuit are presented. The proposed circuit is useful for the HID lamps due to the small size and the low switching losses. >

New type of ballast for HID lamps using series resonant circuit

A novel type of solid state ballast, which operates in the MHz-range frequency, is presented in this paper. A circuit composed of a voltage-fed half-bridge inverter, a distributed constant line, and a parallel LC resonant circuit has been developed for this purpose. The HID (high intensity discharge) lamp is connected to the output terminal of the inverter through the distributed constant line. Here, since the length of the line is adjusted to 1/4 of the propagation wavelength /spl lambda/, the output voltage of the voltage-fed inverter can be converted to a current source on the load side. Therefore, the ballast can supply not only high voltage to the HID lamp for initiating discharge but also constant current to it during discharge condition. The experimental results from a prototype system verify the theoretical procedure.

Novel scheme of ballast for HID lamps using distributed constant line

The authors present a type of PWM (pulse-width-modulated) inverter for a small-scale photovoltaic power system. It has five voltage levels, including the earth level, which is composed of charging two storage battery units in series or parallel combination. The waveform of the output voltage is more sinusoidal than that of the conventional PWM inverter. In the case of an inductive load, however, the waveform shows some deteriorations. The operation of this PWM inverter with an inductive load is analyzed. An advanced circuit is devised to eliminate these deteriorations. It is verified that the experimental results agree well with the theoretical results obtained using FFT (fast Fourier transform) analysis. A resonant-type five-level PWM inverter is also presented. >

Advanced circuit of five-level PWM inverter with an inductive load

A resonant-type five-level pulse-width-modulated (PWM) inverter for small-scale photovoltaic systems is presented. The output waveform of this inverter has multiple levels of voltage, achieved by connecting two units of power source in series or parallel. The operation of and experimental results for this inverter are presented. An efficient circuit which uses two inductors with coupling is proposed to attain high efficiency with this inverter. The inverter also exhibits reduced low-order harmonics. >

M.H. Ohsato

Papers

New control method of resonant DC-DC converter in small scaled photovoltaic system

New type of ballast for HID lamps using series resonant circuit

Novel scheme of ballast for HID lamps using distributed constant line

Advanced circuit of five-level PWM inverter with an inductive load

Characteristics of resonant type five-level PWM inverter used in small-scaled photovoltaic systems