Distributed Generator Inverters as STATCOMs for Grid Voltage Control
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Solution Overview
Problem
The integration of distributed renewable energy sources, such as wind farms, into power grids poses challenges like voltage regulation and stability due to reverse power flow, which can exceed acceptable voltage limits, necessitating expensive voltage regulation devices.
Innovation Solution
Utilizing solar farm inverters as static synchronous compensators (STATCOMs) to provide dynamically controllable reactive power, especially at night when solar farms are idle, to regulate voltages and improve power system stability, and during the day to support real power generation while performing additional control functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wind farms are integrated into the power grid, then renewable energy generation increases, but voltage regulation becomes difficult due to reverse power flow
Solution Approach 1:
The solar farm inverter is designed to perform multiple functions: during the day it generates real power from solar energy, and at night it operates as a STATCOM to provide reactive power compensation and voltage regulation. This multi-functionality allows a single device to address both renewable energy generation and voltage stability issues without requiring separate dedicated equipment for each function.
Solution Approach 2:
The solar farm inverter serves the power grid's voltage regulation needs during nighttime when it is not generating real power. By utilizing its idle capacity to provide reactive power support, the system essentially serves itself - the same infrastructure that generates clean energy during the day also provides grid stabilization services at night, eliminating the need for separate voltage regulation equipment.
2Reliability
If expensive voltage regulation devices are installed to control reverse power flow, then voltage stability improves, but system cost increases
Solution Approach 1:
Instead of installing dedicated expensive voltage regulation devices, the patent utilizes the existing solar farm inverter to perform voltage regulation functions. The inverter's ability to operate as a STATCOM during nighttime provides the same voltage stability benefits as dedicated devices would, but without the additional capital expenditure for separate equipment.
Solution Approach 2:
The solar farm inverter provides voltage regulation services to the grid during nighttime using its own idle capacity. This self-service approach means the system that benefits from renewable energy integration during the day also provides the stabilization services at night, eliminating the need for separate paid installations of voltage regulation equipment.
3Reliability
If solar farm inverters are used as STATCOM, then voltage control capability improves, but inverter utilization complexity increases
Solution Approach 1:
The inverter operates in different modes depending on the time of day and grid conditions. During the day, it functions as a real power generator; at night, it switches to STATCOM mode for reactive power compensation. This dynamic operation allows the same hardware to adapt to different operational requirements without needing separate dedicated devices for each function.
Solution Approach 2:
The inverter provides useful action continuously throughout the day and night - generating real power during daytime and providing reactive power support during nighttime. This continuous useful action maximizes the utilization of the inverter's capacity and ensures the grid benefits from the infrastructure at all times, rather than having idle equipment or requiring separate devices for different time periods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for effective voltage control, increased power transmission capacity, and improved stability without the need for expensive voltage regulation devices, enabling the integration of more renewable energy sources into the grid.
Implementation Method 1
The DC voltage is provided by an energy storage capacitor. It is also known in the prior art that a STATCOM provides desired reactive power generation, as well as power absorption, by means of electronic processing of voltage and current waveforms in a voltage source converter (VSC).
Data Source
AI summary
The invention provides a method and system for operating an inverter based distributed power generation source with energy storage system, as a Flexible AC Transmission System (FACTS) device—a STATCOM. The inverter based distributed power generation source can provide reactive power compensation, voltage regulation, damping enhancement, stability improvement and other benefits provided by FACTS devices. These STATCOM functions are provided when the said energy storage based distributed power generation source is doing at least one of: i) not exchanging active power with said power grid system, or ii) exchanging active power less than a maximum inverter capacity with said power grid system. The present invention thus provides a technological improvement that opens up a new set of applications and potential revenue earning opportunities for energy storage based distributed power generation sources other than simply from exchanging (injecting or absorbing) active power.