Question

In an islanded AC microgrid, there are two parallel inverters (both of them are under droop control).

(a) The input to the inverter 1 is provided from a battery storage system with DC voltage of 350V. The output voltage of this space vector modulated three phase inverter is 560V at rated current of 120A and the load power factor is 0.8. The modulation index of the inverter is 0.85.
(b) The input to the inverter 2 is from an Active Rectifier with input from a 3 phase synchronous generatordriven by a gas turbine. The output voltage of the synchronous generator is 480V, three phase, 60Hz. The output voltage of this sinusoidal pulse width modulated inverter is 780V at rated current of 80A, and the lad power factor is 0.85. The modulation index of the inverter is 0.9.

Their respective droop characteristics of the two inverters are given by:

w1 = 60Hz - 0.2Hz / kW * P1

w2 = 60Hz - 0.1Hz / kW * P2

Draw the block diagram of the total system.

Answer 1

The question pertains to the configuration of an AC microgrid with two paralleled inverters under droop control. Each inverter is supplied by a different power source (battery and gas turbine generator), with unique modulation indexes and droop characteristics that would be represented in the block diagram of the overall system

Step-by-step explanation:

The student is asking about the setup of a paralleled inverter system in an islanded AC microgrid, with each inverter having its own power source and droop control characteristics. In such a system, two inverters work in parallel to supply power to a load. To begin addressing this problem, we'll need to understand the fundamentals of AC power generation and modulation techniques used in power electronics.

Inverter 1 is connected to a battery storage system with a DC voltage of 350V, and it generates 560V AC at a current of 120A and a power factor of 0.8. Its modulation index is 0.85. Meanwhile, Inverter 2 takes input from an Active Rectifier connected to a synchronous generator powered by a gas turbine. It produces 780V AC at a current of 80A with a power factor of 0.85 and has a modulation index of 0.9. The droop characteristics control the frequency output in relation to the power load on each inverter, with Inverter 1's frequency dropping 0.2 Hz per kW, and Inverter 2's dropping 0.1 Hz per kW.

A block diagram of the total system would include the battery and synchronous generator as energy sources, their respective inverters with modulation controls, outputs connected to the common load, and a controller implementing the droop characteristics for both inverters.