Читать книгу Power Electronics-Enabled Autonomous Power Systems - Qing-Chang Zhong - Страница 16

Electrification is the greatest engineering achievement of the 20th century (NAE 2000) and the power system is regarded as the largest and most complex machine engineered by humankind (Kundur 1994). Power systems are arguably the most important infrastructure that underpins social life and economic growth because “energy regimes shape the nature of civilizations –how they are organized, how the fruits of commerce and trade are distributed, how political power is exercised, and how social relations are conducted” (Rifkin 2011).

The generation of electricity has been dominated by large centralized facilities that burn fossil fuels, such as coal, oil, and gas. While fossil fuels have greatly contributed to the world's civilization, two challenging consequences are emerging: one is that fossil fuels are not sustainable and the other is that the combustion of fossil fuels emits greenhouse gases, which is a major cause for climate change – one of today's most pressing global challenges (Hutt 2016). The large‐scale adoption of renewable distributed energy resources (DERs) has been widely accepted as a promising means to tackle these two challenges. The United Nations have put the Paris Agreement into force to reduce greenhouse gas emissions (UN 2018) and many countries have set strategic plans to utilize renewable energy and make a transition to a low‐carbon economy. For example, France and the UK plan to close all coal plants by 2023 (England 2016) and 2025 (Vaughan 2018), respectively. Many states in the US, including Hawaii, California, and New York, have decided to generate 100% carbon‐free electricity by around 2050. As a result, the number of DER units is rapidly growing and could easily reach millions, even hundreds of millions, in a power system. This is often referred to as the democratization of power systems (Farrell 2011). Integrating a small number of DERs into the grid is not a problem, but integrating millions of DERs into the grid brings unprecedented challenges to grid stability, reliability, security, and resiliency (Zhong and Hornik 2013). For example, it has been reported that Hawaii's solar push strains the grid (Fairley 2015) and renewable energy could leave you mired in blackouts (Brewer 2014). Fundamentally speaking, this is less of a power problem but more of a systems problem.

Adding an ICT system into the power system, hence the birth of the smart grid, has emerged as a potential solution to make power systems more efficient, more resilient to threats, and friendlier to the environment (Amin 2008; Amin and Wollenberg 2005). However, this could also lead to serious reliability concerns (Eder‐Neuhauser et al. 2016; Overman et al. 2011). If the ICT system breaks down then the whole power system could crash. On 1 April 2019, a computer outage of Aerodata caused 3000+ flight cancellations or delays, affecting all major US airlines including Southwest, American, Delta, United, Alaska, and JetBlue (Gatlan 2019). This sends a clear warning signal to the power industry: ICT systems may become a single point of failure for power systems and similar system‐wide outages could happen to power systems if their operation relies on ICT infrastructure. Moreover, when the number of players reaches a certain level, how to manage the ICT system is itself a challenge. What is even worse is that adding ICT systems to power systems opens the door for cyber‐attacks by anybody, at any time, from anywhere. On 23 December 2015, hackers compromised the ICT systems of three energy distribution companies in Ukraine and temporarily disrupted the electricity supply to approximately 225,000 customers (Lee et al. 2016). There are numerous reports about cyber‐attacks to power systems (Carroll 2019) and, on 15 June 2019, The New York Times reported that US Escalates Online Attacks on Russia's Power Grid (Sanger and Perlroth 2019). There are certainly issues beyond engineering and technologies but the reliance of power system operation on ICT systems has become a fundamental systemic flaw. It is the responsibility of engineers to correct this systemic flaw and make power systems secure and reliable. Actually, there is no other choice left. On 27 June 2019, the US Senate passed a bipartisan bill, the Securing Energy Infrastructure Act, with the aim of removing vulnerabilities that could allow hackers to access the energy grid. There is a pressing demand to correct this systemic flaw and avoid potential cyber‐attacks.

Another fundamental systemic flaw of current power systems is that a local fault can lead to cascading failures (Schäfer et al. 2018; Yang et al. 2017). On 28 September 2016, tornadoes with high‐speed winds damaged and tripped two 275 kV transmission lines in South Australia (SA), causing six voltage dips in 2 min. Eight wind farms exceeded the preset number of voltage dips and tripped, losing 456 MW wind generation in 7 s. The imported power through the Victoria–SA Heywood Interconnector (510 MW) significantly increased and forced it to trip within 0.7 s, islanding SA from the National Electricity Market and leaving an imbalance of 1 GW. Subsequently, all gas generators tripped and all supply to SA was lost, leading to a state‐wide blackout. About 850,000 customers lost electricity (AEMO 2017). On 16 June 2019, all of Argentina and Uruguay, and parts of Brazil, Chile, and Paraguay in South America were hit by a massive blackout, affecting approximately 48 million people (Regan and McLaughlin 2019). The blackout originated at an electricity transmission point between the power stations at Argentina's Yacyreta Dam and Salto Grande in the country's northeast. On 9 August 2019, a major blackout struck England and Wales, affecting almost a million homes and forcing trains to a standstill around the UK (Ambrose 2019). Again, it was caused by something not uncommon, the loss of a gas‐fired power plant and an offshore wind farm. There is a pressing demand to correct this systemic flaw and prevent local faults from cascading into wide‐area blackouts.

The purpose of this book is to summarize the author's profound thinking over the last 18 years on these problems, which he anticipated in 2001, and present a theoretical framework, together with its underpinning technologies and case studies, for future power systems with up to 100% penetration of distributed energy resources to achieve harmonious interaction, to prevent local faults from cascading into wide‐area blackouts, and to operate autonomously without relying on ICT systems and completely avoid cyber‐attacks.

It is purely a coincidence that The New York Times report on cyber‐attacks on Russia's power grid, the South America blackout, the US legislation on preventing cyber‐attacks to the grid, and the UK blackout all happened within the last two months when this book was being finalized, signaling the right time to complete this book.