The most important impact of power electronics on our society in the last 50 years has been the elimination of the 60-Hz ac power delivery system for consumer electronic products. Central to this achievement is the use of silicon (Si) power devices and pulsewidth modulation (PWM) techniques in delivering regulated ac and dc powers to low-voltage (LV) loads such as light-emitting diodes and computers. These solid-state power electronic converters have provided our society numerous benefits, including high-quality power and substantial energy savings. They also form the core technology for integrating renewable energies such as wind and solar into our power grid. Figure 1 shows a typical power delivery architecture commonly found in computer supplies and data centers. The incoming universal ac grid power is converted by a power factor correction circuit to 400 V dc before it is stepped down to a lower voltage dc intermediate bus, such as 12 V, and then it powers the digital loads at voltages as low as 1 V by a point-of-load converter. Si power metal-oxide-semiconductor field-effective transistor (MOSFET) transistors from 20 V to 700 V are almost exclusively used in this application with switching frequencies from tens of kilohertz to one megahertz. Emerging devices based on gallium nitride (GaN) heterojunction field effect transistors reduce the switching and conduction losses when compared with Si power MOSFETs and are, therefore, poised to compete in these applications, driven by the need for higher energy efficiency and higher power density.

Medium-Voltage Solid-State Transformer: Technology for a Smarter and Resilient Grid

Due to urbanization and the rapid growth of population, carbon emission is increasing, which leads to climate change and global warming. With an increased level of fossil fuel burning and scarcity of fossil fuel, the power industry is moving to alternative energy resources such as photovoltaic power (PV), wind power (WP), and battery energy-storage systems (BESS), among others. BESS has some advantages over conventional energy sources, which include fast and steady response, adaptability, controllability, environmental friendliness, and geographical independence, and it is considered as a potential solution to the global warming problem. This paper provides a comprehensive review of the battery energy-storage system concerning optimal sizing objectives, the system constraint, various optimization models, and approaches along with their advantages and weakness. Furthermore, for better understanding, the optimization objectives and methods have been classified into different categories. This paper also provides a detailed discussion on the BESS applications and explores the shortages of existing optimal BESS sizing algorithms to identify the gaps for future research. The issues and challenges are also highlighted to provide a clear idea to the researchers in the field of BESS. Overall, this paper conveys some significant recommendations that would be useful to the researchers and policymakers to structure a productive, powerful, efficient, and robust battery energy-storage system toward a future with a sustainable environment.

Battery energy-storage system: A review of technologies, optimization objectives, constraints, approaches, and outstanding issues

A paradigm shift in power generation technologies is happening all over the world. This results in replacement of conventional synchronous machines with inertia less power electronic interfaced renewable energy sources (RES). The replacement by intermittent RES, i.e., solar PV and wind turbines, has two-fold effect on power systems: (i) reduction in inertia and (ii) intermittent generation, lead to the degradation of the frequency stability. In modern power system, the frequency regulation (FR) has become one of the most crucial challenges compared to conventional system because the inertia is reduced and both generation and demand are stochastic. The fast responsive energy storage technologies, i.e., battery energy storage, supercapacitor storage technology, flywheel energy storage, and superconducting magnetic energy storage are recognized as viable sources to provide FR in power system with high penetration of RES. The important aspects that are required to understand the applications of rapid responsive energy storage technologies for FR are modeling, planning (sizing and location of storage), and operation (control of storage). This paper comprehensively reviews these important aspects to understand the applications of fast responsive storage technologies more effectively for FR services. In addition, based on the real world experiences this paper highlights the gaps and limitations in the state-of-the-art practices. Moreover, this study also provides recommendations and future directions for researchers working on the applications of storage technologies providing FR services.

A review on rapid responsive energy storage technologies for frequency regulation in modern power systems

The reduced level of system inertia in low-carbon power grids increases the need for alternative frequency services. However, simultaneously optimizing the provision of these services in the scheduling process, subject to significant uncertainty, is a complex task given the challenge of linking the steady-state optimization with frequency dynamics. This paper proposes a novel frequency-constrained stochastic unit commitment model which, for the first time, co-optimizes energy production along with the provision of synchronized and synthetic inertia, enhanced frequency response, primary frequency response and a dynamically-reduced largest power infeed. The contribution of load damping is modeled through a linear inner approximation. The effectiveness of the proposed model is demonstrated through several case studies for Great Britain's 2030 power system, which highlight the synergies and conflicts among alternative frequency services, as well as the significant economic savings and carbon reduction achieved by simultaneously optimizing all these services.

Simultaneous Scheduling of Multiple Frequency Services in Stochastic Unit Commitment

As one of the featured initiatives in smart grids, demand response is enabling active participation of electricity consumers in the supply/demand balancing process, thereby enhancing the power system's operational flexibility in a cost-effective way. Industrial load plays an important role in demand response because of its intense power consumption, already existing advanced monitoring, and control infrastructure, and its strong economic incentive due to the high energy costs. As typical industrial loads, cement plants are able to quickly adjust their power consumption rate by switching on/off the crushers. However, in the cement plant as well as other industrial loads, switching on/off the loading units only achieves discrete power changes, which restricts the load from offering valuable ancillary services such as regulation and load following, as continuous power changes are required for these services. In this paper, we overcome this restriction of poor granularity by proposing methods that enable these loads to provide regulation or load following with the support of an onsite energy storage system.

Demand Response of Ancillary Service From Industrial Loads Coordinated With Energy Storage

With the increased environmental concern, the photovoltaic (PV) generation capacity is growing in today’s power systems. As the PV penetration rate increases, the intermittency and uncertainty of PV systems will cause frequency regulation issues. When rapid fluctuations take place, the system requires fast responding regulation to recover the frequency within a short period of time. Traditional power plants with slow dynamics are less capable of tracking the fast-changing regulation signal. In this context, a battery energy storage system (BESS) is considered as an effective regulation source to respond immediately to frequency deviations. This paper addresses the sizing issue of an aggregated BESS by a series of system level performance tests with different BESS penetration rates. The evaluation criteria are the control performance standards 1 and 2. Response effectiveness of the BESS with different levels of disturbances is also analyzed, with comparison to that of the traditional power plants. The proposed BESS aggregation controller is also validated using software simulations and a hardware testbed.

Penetration Rate and Effectiveness Studies of Aggregated BESS for Frequency Regulation

The battery energy storage systems (BESSs) have been increasingly installed in the power system, especially with the growing penetration rate of the renewable energy sources. However, it is difficult for BESSs to be profitable due to high capital costs. In order to boost the economic value of BESSs, this paper proposes a hierarchical energy management system (HiEMS) to aggregate multiple BESSs, and to achieve multimarket business operations. The proposed HiEMS optimizes the multimarket bids considering a realistic BESS performance model, and coordinates the BESSs and manages their state of charge values, according to their price penalties based on dynamically generated annualized cost. By taking part in the energy market and regulation market at the same time, the cost-performance index (CPI) of the BESS aggregation is greatly improved. The impact of photovoltaic generation on system performance and CPI is also studied.

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A Hierarchical EMS for Aggregated BESSs in Energy and Performance-Based Regulation Markets

The battery energy storage systems (BESSs) have been increasingly installed in the power system, especially with the growing penetration rate of the renewable energy sources However, it is difficult for BESSs to be profitable due to high capital costs In order to boost the economic value of BESSs, this paper proposes a hierarchical energy management system (HiEMS) to aggregate multiple BESSs, and to achieve multi-market business operations The proposed HiEMS optimizes the multi-market bids considering a realistic BESS performance model, and coordinates the BESSs and manages their state of charge (SOC) values, according to their price penalties based on dynamically generated annualized cost By taking part in the energy market and regulation market at the same time, the cost-performance index (CPI) of the BESS aggregation is greatly improved The impact of photovoltaic generation (PV) on system performance and CPI is also studied

/pdf/hierarchical-ems-for-aggregated-besss-in-energy-and-35mpm3rl9t.pdf

Hierarchical EMS for aggregated BESSs in energy and performance-based regulation markets

With the more advanced technology and decreased cost of batteries, it is less costly to form large-scale battery energy storage systems (BESSs) to take part in grid applications. BESSs are increasingly considered as participants for grid regulation services because of their fast responding ability. This paper reviews various control schemes of the BESSs in the literature. Sizing studies are conducted based on the current regulation performance scoring system and the respective criteria, using historical regulation data. The cost and lifetime of three mainstream batteries (Lead-acid, Lithium-ion, and Vanadium) are estimated. Cost-performance indexes are calculated based on simulation results.

Cost-effectiveness studies of the BESSs participating in frequency regulation

With the increased environmental concern, the photovoltaic (PV) generation capacity is growing in today's power systems. As the PV penetration rate increases, the intermittency and uncertainty of PV systems will cause frequency regulation issues. When rapid fluctuations take place, the system requires fast responding regulation to recover the frequency within a short period of time. Traditional power plants with slow dynamics are less capable of tracking the fast-changing regulation signal. In this context, a battery energy storage system (BESS) is considered as an effective regulation source to respond immediately to frequency deviations. This paper addresses the sizing issue of an aggregated BESS by a series of system level performance tests with different BESS penetration rates. The evaluation criteria are the control performance standards 1 and 2. Response effectiveness of the BESS with different levels of disturbances is also analyzed, with comparison to that of the traditional power plants. The proposed BESS aggregation controller is also validated using software simulations and a hardware testbed.

Tian Zhang

Papers

Penetration Rate and Effectiveness Studies of Aggregated BESS for Frequency Regulation

A Hierarchical EMS for Aggregated BESSs in Energy and Performance-Based Regulation Markets

Hierarchical EMS for aggregated BESSs in energy and performance-based regulation markets

Cost-effectiveness studies of the BESSs participating in frequency regulation

Penetration rate and effectiveness studies of aggregated BESS for frequency regulation