16.12.2015

Dc dc converter for photovoltaic applications

The components of a renewable solar energy system are actually relatively simple and easy to understand, even without a prior knowledge of electrical systems. Photovoltaic (PV) installations tied to the grid are usually built with arrays of modules connected in series to string inverters. With the rapid worldwide market growth in solar energy, innovation continues to drive inverter design. Protections: overload, short circuit, reverse polarity and under and input surge, temperature.
As we all know, the photovoltaic power station is located at remote areas, which makes it difficult to supply power for the control systems.
In traditional photovoltaic monitoring system, generally we need an additional power supply like battery or the mains supply to power the system. You must have JavaScript enabled in your browser to utilize the functionality of this website.
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In this study, a bidirectional power converter for a stand-alone photovoltaic power generation system when a lithium-ion battery is used to regulate the power supply.
Multilevel topologies have several advantages to offer over two-level topologies in high voltage applications.
Modular converters based on isolated dc–dc topologies are proposed in and further investigated and modified.
These topologies enable static voltage sharing among identical modules which may be connected in series. The proposed TMMC topology is configured as a general n-level structure as shown in Figure. The single-column structure of the TMMC is similar to the battery charge equalizer circuit first proposed and later applied to PV applications for equalizing series-stacked PV panel voltages. An n-level TMMC may also be operated at other non-integer conversion ratios and still maintain equal module power sharing.
In this paper, a bidirectional modular multilevel dc–dc converter topology and its corresponding control algorithm is proposed.
A rapidly growing architecture, the micro-inverter, converts power from one PV module to the AC grid and is usually designed for a max output power in the range of 180-300W. Modern inverters need to have proven reliability across various grid types, while increasing conversion efficiency and integrating new safety and control features.
The modules feature an isolation voltage of 4000VAC, output over-voltage protection, short circuit protection and input against reverse protection which ensure the stability of the circuit. At the meantime, the multiple protections ensure the reliable operation of power supply and load. Our new developments help thousands of engineering students and research scholars to complete their projects in a simple and easy way. Also, a small-scale air-conditioner was provided as the load for the bidirectional power converter developed to examine the efficiency of the converter. Several effective modular multilevel dc–dc converters have been proposed in the literature. In medium voltage applications, it has been difficult until very recently to find suitable devices to build converters with Elementary concept of a multilevel converter to achieve higher power rating entails using a series of power semiconductor devices with several lower DC sources to perform the power conversion by synthesizing a staircase voltage waveform.
In applications where isolation is not a requirement, the weight, parasitic, losses, and cost associated with transformers add to the system complexity and limit the expandability and operating power of such topologies.


TMMC’s modules are constructed from buck-boost converters as shown on the top right corner of Figure.
This structure has also been recently employed for differential power processing of digital systems. For step-up only operation, switch Sa would be of active type and switch Sb could be a diode. An exception in this case would be the first row modules which would carry a current different than other row modules. As specified, the output voltage is simply equal to the summation of the input voltage with the first and second row capacitor voltages.
In this state, the modules’ inductors are energized, with the first row modules’ inductors energized from the input voltage source and the second row module’s inductor energized through the first row modules’ capacitors. In this state, each module’s inductor is transferring energy to the corresponding module’s capacitor. The proposed TMMC converter is capable of equal power sharing among its modules over a broad range of conversion ratios. Through interleaved operation, the output voltage and input current ripples of the TMMC are shown to achieve a reduction of 38%and 49%, respectively.
Micro-invertera€™s have advantages in terms of ease of installation, localized maximum power point tracking (MPPT) and redundancy that provides robustness to failure. TI reference designs enable designers to evaluate every part of the inverter system to ensure they are choosing the optimal technologies to meet their customer demands. The overall framework of the proposed system comprised a maximum power point tracking controller, bidirectional buck–boost soft switching converter, lithium-ion battery and small-scale air-conditioner. This has allowed power electronic power processing to be extended to higher voltages and power operations. In addition, the expandability of these converters is limited due to transformer isolation rating requirements. The TMMC is bidirectional such that the high-side voltage (VHV) and low-side voltage (VLV) may readily be used as either input or output.
As noted from the TMMC’s structure in Figure, there are n modules in parallel on the first row to process the high current on the low-voltage side, and at higher rows where a higher net voltage is realized, fewer modules are connected in parallel. Conversely, for step-down only operation, switch Sa could be a diode and switch Sb would be of active type. Nevertheless, this may easily be compensated through addition or subtraction of modules in the first row. The proposed control algorithm provides localized control of the modules which enhances the dynamic performance and design flexibility of the converter.
Since each row of the TMMC provides a potential input or output node at a controllable voltage level, multiple-input multiple-output power transfer is readily achievable.
From the gate driver to push higher voltage MOSFETs and IGBTs as efficiently as possible, to the digital power control loops for more robust AC generation, down to the analog signal chain for accurate sensing, our inverter reference designs provide the components required to evaluate the full system. The magnetic less structure of this topology makes it well suited for automotive applications. A modular multilevel dc–dc converter is proposed for interfacing super capacitors to a dc bus in regenerative braking applications.
Disadvantages with these topologies are the large size of the passive components, the high peak currents, and the challenges associated with dynamic voltage sharing during switch transitions. It is noted that the proposed topology’s structure resembles that of the power sharing diagram of Figure.


The low-voltage side’s parallel capacitor are required simply for filtering reasons and are not inherent to the proposed topology’s structure.
Assuming integer-only conversion ratios, the number of required rows and switches for a given conversion ratio are shown in Table I. Figure shows the switching states and corresponding current flow directions of the two-level step-up TMMC under non-inter leaved operation. The steady-state equations provided in Section V may be utilized for component selection Figure. TI also provides designs and software for more emerging features before they are common place in the market, like integrated DC arc fault detection and advanced grid communication connectivity.
The topology is constructed from a series connection of half-bridge converters with an output inductor. The proposed topology, named the triangular modular multilevel dc–dc converter (TMMC) has a transformer less structure and does not suffer from high peak currents.
While the power sharing capability of the TMMC is not identical to that of Figure, it has a significantly reduced silicon area requirement as compared to the topology of (lower than 50% for conversion ratios lower than five).
Semiconductor switches such as MOSFETs or IGBTs may readily be utilized as the active switches.
In general, the TMMC modules are not restricted to the arrangement shown in Figure, and alternative configurations exist.
Three-level step-up TMMC demonstrating input voltage modularity through connection of the input source above the first row. However, due to the switched-capacitor nature of this topology, a deliberate startup procedure is required to avoid current spikes.
In family of non isolated modular resonant dc–dc converter topologies are proposed for high-power applications. Furthermore, additional or fewer modules may be connected in parallel at any row, however, this paper will focus on this right triangular structure which optimally utilizes the power sharing capacity of each module for single-input single-output applications.
The remainder of this paper is focused toward discussing the steady-state and dynamic behavior of the TMMC.
The capacitor-clamped topology is further investigated and modified for soft-switching and optimal design. Moreover, the topology provides multiple fixed voltage nodes which may be utilized as either inputs or outputs.
To aid with visualization and understanding, the two-level structure is selected as the topology under analysis. A few disadvantages associated with the topology of are: 1) it is restricted to integer-only conversion ratios and 2) its modules’ capacitors are exposed to different steady-state voltage stresses, making the topology non-modular from a manufacturing and design perspective.
This qualifies the topology as a multiple-input multiple-output converter and makes it suitable as a scalable unified solution for a variety of power system architectures.
The optimal conversion ratio to operate an n-level TMMC is n + 1 as the converter may easily achieve equal voltage and current sharing among its modules under such configuration.



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