代做EEEE4121 Distributed Generation and Alternative Energy代做留学生SQL语言程序

Department of Electrical and Electronic Engineering

EEEE4121 Distributed Generation and Alternative Energy

Description of Coursework #1 (2025)

Design and evaluation by simulation of a standalone PV system with battery storage with increased security of electricity supply

This project aims at designing a PV system able to provide the full daily electrical energy demand of a critical single-phase AC consumer (240Vrms/50Hz) via a single-phase H-bridge inverter and be able to work in a standalone mode in the case of a prolonged loss of public electricity network, with the help of battery stack. The connection of the PV string to the DC link of the H-bridge inverter should follow the suggestion in Fig 1, whilst the connection of the battery stack to the AC load is not imposed in any way. It could be that the battery connects to the DC link of the H-bridge inverter via a separate DC/DC converter or independently to the AC via its own DC/AC bidirectional inverter, but the aspects related to the converter topology choice of the battery converter needs to discussed in report.

Fig. 1. Single Stage Power Electronic Interface to connect a PV panel string to the AC power grid. The project will consist of the following parts:

Part 1. You will be given a load power profile and the orientation and inclination of a rooftop of the building on which the PV panels will have to be installed. You will be given a specific month of the year for which the energy captured during a sunny day (https://re.jrc.ec.europa.eu/pvg_tools/en/) should cover the energy consumed as resulting from the load power profile given.

A sample of the PV panel datasheet used in the 500W PV inverter design exercise is provided in moodleas a model but for full marks you need to identify a suitable solar panel that should be used to implement the PV string that would give you sufficient string voltage to allow the direct connection of the PV string to the DC link of the H-bridge inverter whilst avoiding overmodulation (fulfil minimum voltage condition).

You may assume the PV power available at a given moment in time [i] is proportional with the  time dependent irradiance data (input from CSV file) relative to the nominal irradiance stated in the datasheet (typically 1000W/m2 for  standard operating condition) and multiplied by the PV panel power rating as follows:

Ppv [i] = Rated_MPP@1kW/m2 * IrradianceCSV_file  [i] / Datasheet_nominal_irradiance                (1)

You need to insert the relevant graphs from PV panel datasheet in the report (state also the web link also to the datasheet in reference!!).

For validation of the PV string configuration, you should use the PLECS model provided and customised with your individual calculated data as resulted from the individual set of parameters received by each student.

Full marks will be awarded to the designs where the selection of PV panel resulted in a reasonable fit which means that the PV energy collected is only slightly larger (by not more than 20%) than the energy consumed by load and the open circuit voltage of the PV string is not larger than 600V. Also, changes in PV characteristics affecting operation (open circuit voltage, MPP voltage and power) due to temperature should be discussed including potential situations where performance or safe operation may be compromised.

Part 2. In order to provide the standalone operation capability needed to increase the energy security of the critical load, a battery stack is to be sized to compensate for the instantaneous power mismatches between the PV generation side and the consumer as defined by the load power profile both in terms of available energy but also maximum power stresses (you need to check both maximums during charging and discharging!). Students are expected to select a suitable battery cell or module of a Lithium-ion chemistry that may suit the specifics of charge discharge cycle and calculate the number of modules or cells needed to achieve the energy requirement. The connection of the battery stack to the inverter is not imposed by a specific power converter topology but the configuration of series sells¶llel strings needs to  aim at reducing cost and complexity of battery converter. For full marks you are also expected to consider aspects related to lifetime, cost and of how to connect the battery to the power system by considering voltage limits emerging from the operation of the power converter that you can choose from the following alternatives:

(i)           interface the battery via its own DC/AC inverter directly to the AC grid, in which case the minimum voltage restriction to avoid inverter overmodulation applies also to the battery string selection (no of series connected cells or modules)

(ii)          connection of the battery to the DC link of the PV inverter via a:

a.      bidirectional voltage step-up (boost) DC/DC converter or

b.       bidirectional voltage step down (buck) DC/DC converter.

This selection needs to be justified and the V/I ratings of switches used in the battery converter and should be derived according to worst case conditions. You need to show an electric circuit diagram (not  block diagram!) as detailed as possible (it doesn’t need to include controller details) of the full system and explain how would work.

Part 3. Based on the design of the PV string in Part 1, which determined the maximum PV string power and the string voltage (at MPP), a design study will be carried out to calculate the size of key passive components (the AC side inductance and the DC-link capacitors) needed for the single phase H-bridge inverter to connect your PV string designed in Part 1 to the 240Vrms/50Hz single phase grid. This calculation step is then followed by a validation by a PLECS simulation study to confirm that the relevant design specs are below the limits.

Each student will receive an individual value for the switching frequency, maximum current ripple in the AC inductor and maximum DC link voltage ripple across the DC link capacitors but it is expected that the target DC-link voltage used in  the H-bridge calculations to be the optimum MPP voltage of the PV string as determined in Part 1 (and not the minimum limit to avoid overmodulation or max voltage!!).

The maximum peak to peak switching current ripple in the AC side inductor is a given percentage (individual value received by email) of the peak of the required fundamental AC side current component which should match the maximum point power of your PV string.

The maximum peak to peak DC-link voltage ripple is a given percentage (individual value received by email) of your PV string voltage when operating at MPP.