In many papers I have seen boost converter has been used but it steps up the voltage.In many places buck converter is also used. My question is how exactly the tracking occurs . I have studied P & O As well as incremental conductance. Using boost how does input voltage gets affected.
Hello Dabamoy!!!
The following lecture series will surely help you in understanding Solar PV and MPPT.
https://nptel.ac.in/courses/117108141/55
Regards
Utkarsh
In certain cases, Boost converter is used for e.g. say 200V to 600V DC and then power the inverter for 400V motor. The MPPT algorithm is inbuilt in the boost converter and inverter module used for frequency control.
So the boost converter will match the impedance of PV array and the load of the boost converter and as you mention there are various MPPT technique used for this.
A legacy boost converter has high efficiency across a wide power range. That is why it is commonly used as input voltage boosting stage in PV systems. However it depends on a specific PV system requirements whether or not the voltage from PV generator should or shouldn't be boosted. You may have a look on different boosting topologies in a PV power system:
Article Step-up DC/DC converters for photovoltaic applications - the...
To efficiently track the MPP (Maximum *POWER* Point) across different wheather conditions the power generated by PV array should be measured, that is why a voltage and a current are sensed at the input of a boost converter (i.e. output of a PV array) and their multiplied values (i.e. instantenuous PV array power) are processed by a MPPT algorithm which further drives a boost converter to track MPP. An example of such system is presented here:
Article Low voltage photovoltaic system with P-V curve evaluation MP...
I hope it helps. Cheers.
The boost converter is used to step up the input voltage to obtain a desired output voltage. The circuit operation is divided into two modes. In mode 1, when the switch is in on condition the input current supplies energy to the inductor for a period time (T) ON. Similarly in mode 2, when the switch is off, the inductor voltage adds to the source voltage and current is forced to flow through diode and the load for a period T OFF. The MPPT is achieved by interposing a boost converter between the PV module and the load, thus, from the voltage and current measurements, the MPPT algorithm calculates the optimal duty cycle D (0≤D≤1) in order to maximize the power flow.
According to the other part of your enquiry, suppose we have a constant load at the output of a boost converter. Duty cycle (D) variations which are the result of a MPPT algorithm, cause average value of the input current decrease / increase which causes the changes of the operating point of a PV array (see PV array P-V and I-V curves). Thus a MPPT algorithm adjusts the average value of PV array output current to track instantenous maximum power point (MPP) which changes with the wheather conditions.
Best of luck.
The DC-DC converter is used for matching the load with the characteristics of the PV panels due to its sensitivity to changes the duty cycle D with the voltage.
Due to the low output voltage of the PV cells and high current, to match the demand from the load, the boost converter is used- it helps to match the voltage level, however it also reduces the current level (2x voltage mean that you are getting 0.5x current), which is a proper operating conditions for most electrical loads. In some cases, buck-boost converter might be used, but it is less common practice.
MPPT using buck converter:
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The first point that we have to consider is that there are sources like the AC grid in case of AC or the battery in case of DC. These are known as voltage sources. These voltage sources are considered to remain practically in the same voltage whether AC derived from a solar PV source followed by a chain of converters is Integrated to the AC grid or a DC source derived from a solar PV is integrated to a battery.
For example consider a 12vbattery of rating 100AH. Consider a 24 v battery of capacity 1 AH. Parallel them. What will happen now?. What happens is that the terminal voltage of the 24v battery also becomes 12 v. A current flows from the 24v 1Ah battery to the 12 v 100 Ah battery while the terminal voltage of the small, 1Ah, battery is also brought down to nearly 12V. Now consider a boost converter. Assume that a boost converter is fed with 12 v and applied with 0.5 duty cycle. The output voltage is expected to become 24 v only if the load is neither a current source nor a voltage source. If the load itself is avoltage source of 12v , like a battery, even if the source voltage of the boost converter is 12v and duty cycle d being 0.5 the output side voltage of the boost converter does not become 24 v but what prevails is the terminal voltage of the load side voltage source, say battery. Now the boost converter drives a current against the voltage source thus delivering power to the voltage source , which is battery and it gets charged. Variations in solar insolation will be exhibited as variations in power delivered, manifested as variations in the output current of the boost converter flowing against a fairly constant voltage. The important point is that there are boost converters in DC, and there are boost inverters in AC , like the Zsource inverters, but when these are respectively connected across DC or AC voltage sources the converter drives a variable current output for variable power delivery while the voltage across the integrating bus bar is maintained practically at a constant voltage by some other mechanism not known to the boost converter or anything else by which renewable energy is being integrated.
At first, as we want to extract the maximum power from the PV panel, and for this reason, we need to ensure the maximum power point to extract the maximum power under certain conditions. And then if you take look over the working principle of the boost converter it is a converted where the PV input voltage is lower than the battery voltage of the system, so usually to control the PV power output or controlling the charge of storage you need to use this boost converter used for MPPT Tacking.
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