Browse Prior Art Database

CONTROL SYSTEM FOR SOLAR FARMS ALLOWING BLACK START

IP.com Disclosure Number: IPCOM000244490D
Publication Date: 2015-Dec-16
Document File: 5 page(s) / 156K

Publishing Venue

The IP.com Prior Art Database

Abstract

An efficient control system and method for allowing a solar farm to operate in a black start mode is disclosed. A system implementing the disclosed method is provided with a number of individual panel units 1, 2, 3, …n. The system consists of two sections: a DC-DC boost converter and a DC-AC inverter, with a common DC link between the two sections via the control system. The control system implements a dynamic droop curve for regulating output voltage and frequency, resulting in a constant volt per hertz ratio curve. The dynamic droop curves allow solar inverters to have some amount of output impedance for sharing the load as the load current increases. The curves generated by the control system are configured to maintain the output voltage and frequency very close to the nominal values for load currents below the total capability of the solar farm.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 44% of the total text.

Page 01 of 5

283270 

CONTROL SYSTEM FOR SOLAR FARMS ALLOWING BLACK START

BACKGROUND

This invention relates generally to control system for solar farms and in particular to a system allowing a solar farm to operate in black start mode. The solar farm is effectively operated in black start mode where the farm powers a load independent of the grid. In this circumstance, the solar inverter is not equipped with grid to track the voltage and it may create its own reference for voltage and current. Existing control systems are not configured for this kind of operation and this may result in islanding of a single inverter. Further, currently available control systems are also unstable when used with multiple parallel solar inverters.

The control system of the DC-DC boost converter ordinarily operates to control the power output of each inverter, with typical voltage-current curves as shown in FIG. 1. The parallel inverters in a solar farm operate in separate photovoltaic (PV) arrays. In such instance, one of the PV array provide more or less available power than others based on the condition of the PV array and partial shading from clouds. Considering the different PV curves of each array and the MPPT (Maximum Power Point Tracking) for each solar inverter being independent, it is necessary to design a new control scheme for the DC-DC boost converter to properly regulate the power. Thus, there is a need for a novel control system which could allow a solar farm to operate in black start mode.

FIG. 1: Dynamic droop curve for output voltage against output current

BRIEF DESCRIPTION OF DRAWINGS

The invention discloses a control system that allows a solar farm to operate in black start mode by the implementation of dynamic droop curves, wherein:

FIG.1 illustrates a dynamic droop curve for output voltage against output current in solar farm control system.

FIG.2 illustrates a control system configured to generate a dynamic droop curves for a solar farm operating in black start mode.

Output Voltage vs Output Current


1.2

1


0.8


0.6


0.4


0.2

0

(PU)

 

 

Voltage

Output

0 2


0.5


1.5

1

Output Current (PU)


Page 02 of 5

283270 

FIG.3 illustrates a method for allowing a solar farm to operate in black start mode.

FIG.4 illustrates a dynamic droop curve for output frequency against output current in the control system.

FIG.5 illustrates a dynamic droop curve for output volt per hertz against reactive output current in the control system.

DETAILED DESCRIPTION

The invention proposes an efficient control system and method for allowing a solar farm to operate in black start mode. The control system implements a dynamic droop curve for regulating output voltage and frequency, resulting in a constant volt per hertz ratio curve as shown in FIG. 1. The dynamic droop curves allow solar inverters to have some amount of output impedance, causing them naturally to share the load as the load current increases. The curves are generated by the control system to maintain the out...