WEEK 1
For this week, I decided to design a transformer-less Online UPS system, which by using the conventional Boost PFC circuit and Bidirectional DC-DC converter for charging and discharging process for the battery. The boost circuit will act as a power factor correction. Meanwhile, the bidirectional DC-DC converter, this converter operates in a buck manner while charging and in boost manner while discharging. Then, I will be doing the literature study on both components for the simulation in Matlab Simulink and the mathematical calculation for each parameter involved in this design. which the objective for this project is :
- To create a transformer-less Online UPS system which as we already know that the transformer can make the circuit bulky and transformer is very expensive
- To maintain input voltage and input current in phase with one another.
WEEK 4
For current week 4, I will design the bidirectional dc-dc converter for charging and discharging the battery. This converter operates in a buck manner while charging and in boost manner while discharging. The voltage from the DC bus needs to be stepped down during charging and boosted during discharge. From the literature study that been done, The Bidirectional DC-DC Converter block represents a converter that steps up or steps down DC voltage from either side of the converter to the other as driven by an attached controller and gate-signal generator. Bidirectional DC-DC converters are useful for switching between energy storage and use, for example, in electric vehicles. There are 2 types for the bidirectional DC-DC converter which is an isolated converter and non-isolated converter. For my design, I will use the non-isolated converter, bidirectional DC-DC converter without an electrical barrier. This model variant contains an inductor, two capacitors, and two switches that are of the same device type.
WEEK 2
For current week 2, I am designing the conventional boost PFC circuit. I doing the research on the internet for the simulation of the design and the calculation for all the parameters involved. The circuit used here is a conventional boost PFC circuit. This helps to maintain input voltage and input current in phase with one another.
In order to run the simulation, we need to calculate the parameter for the duty cycle, D, input current, di, inductor, L, and capacitor, C. The value for the input is from the related to the output voltage of bridge rectifier is given as
The peak power for the circuit is 5KVA and switching frequency is 20kHz. Then, we can calculate the duty cycle,
Then we need to calculate the input current,di, and ripple current can be determined by using estimation for 20% to 40% of the output current,
Then we can calculate the inductor and capacitor,
WEEK 3
For week 3, I started to design the simulation for the conventional boost PFC circuit. By using the parameter that we calculated before, we can get the 400V DC that needs to be fed to the bidirectional DC-DC converter. From the simulation, the output we get is 398.9V which is near 400V. the figure below is my boost design that has been combined with the rectifier,
The results for the output are shown below,
This is the result of the output waveform for the output voltage.
This is the result of the input waveform of the input current.
WEEK 5
For week 5, I start to design the simulation for the non-isolated bidirectional dc-dc converter. The voltage from the DC bus needs to be stepped down during charging and boosted during discharge on the battery.
In buck mode, the 400V dc is stepped down to 120V dc to charge the battery. The design equation as follows,
In boost mode, the battery voltage of 120V is increased to 400V DC and powers inverter during the absence of grid supply. The design equations are as follows