System Integration of Grid-Connected Photovoltaic Converters

• Unreliable grid experiences sag, swell, frequency deviation, harmonic distortion => Unreliable Performance of sensitive loads

• Reactive loads require power factor correction circuits => Additional Cost

• Harmonic-inducing loads contaminate grid current => Inefficiency

S

MainDSP

DSP

CommunicationNetwork

Sensor Network

Boost converter

Boost converter

DC/AC InverterSeries

DC/AC Inverter Parallel

Boost converter

Boost converter

DC/AC InverterSeries

PV

PV

Grid

DC/AC Inverter Parallel

Load

DSP

DSP DSP

• Phase locked loop will be embedded in the series invertor• Synchronize input grid signal with generated signal• Compensating voltage changes by tracking the grid voltage in

relation to the signal of the grid

• Measure and provide real time power measurements to the DSPs

• Use LEM Voltage Transducer to step down the voltage to +/- 1.5V

• External +/- 15V DC source to shift up the voltage to 0V ~3V.

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3

2 • Transmit different current and voltage values from different boards to main controller

• Explore more effective communication protocol to use for the project.

Compensates for grid voltage disturbances

Series invertor

Parallel invertor

Compensates for load

harmonic and reactive currents

Current Problem

Proposed Solution

FYP Group:EEE-14A100 Students: Luo Jin Wei, Wivaldy Lee Wen Yi, Stephanie Kek Sok HuiDiploma in Clean Energy Engineering (DCEG) Supervisor: Dr Chia Chew Lin Co-supervisor: Arun Nagendra, Naga Brahmendra

*PLL is implemented inside the series inverter

Our Objectives• To design and build the sensing network will provide the accurate, precise real

time power measurement

• To build and develop a communication system which will transmit real time power measurements between multiple DSPs for Inverter control coordination

• To develop control algorithm that will compensate any grid voltage fluctuations via tracking of grid and inverters' voltage and phase.

S

S

S S S S S

*S => Sensor

1

2

3

Methodology

Reference: “Single-Phase Inverter-Control Techniques for Interfacing Renewable Energy Sources With Microgrid-Part II: Series-connected Inverter Topology to Mitigate Voltage-Related Problems Along With Active Power Flow Control,” IEEE Trans. Power Electron., Vol. 26, No. 3 , MARCH 2011