Hybrid power plants (HPPs) are an emerging technology generally defined as multiple different generation and/or storage resources behind a single point of interconnection. This blend of technologies possesses several advantages over conventional generation, such as reducing curtailment of renewables sources, peak shaving, among other benefits. However, at present, HPPs are not currently allowed for in some jurisdictions in the world due to their novelty, and there is no unified definition of HPPs across jurisdictions, which makes it difficult for widespread integration.

With many HPPs being inverter-based resources such as battery energy storage systems (BESS) with solar plants, it is important to verify the behaviour of such plants in the electromagnetic transient (EMT) domain. Further, it is important to understand the various services that such plants can provide to the network, and the different factors that may impact the provision of such services. With the increase of inverter-based resources (IBRs) in the network, it is also possible that soon, for few hours of the day, many power systems can be 100% fed from inverter-based generation. In this scenario, the performance of HPPs, and their potential grid forming capability is to be investigated.

This paper aims to address modelling challenges with HPPs in the positive sequence and EMT domains for issues such as stability, controller interaction, circulating AC current and demand response. The impact of HPPs on frequency stability and damping of power system oscillations will be shown. Further, the use of generic models to represent the behaviour of the hybrid plant is discussed.

Keywords – Hybrid power plant, positive sequence, EMT, stability, transmission planning.

Commercial interest in renewable-battery hybrid power plants connected to the bulk power system (“hybrids”) is rapidly growing in the United States and globally. Since hybrid power plants’ operational behavior depends on underlying design choices, understanding what configurations of hybrids are likely to be deployed in the near-future is important for bulk power system planners responsible for ensuring overall system reliability and planning the transmission network. We use historical wholesale market power prices in the seven U.S. organized wholesale power markets from 2012–2019 to calculate hybrid net values, subtracting costs from revenues, across a wide range of wind and solar hybrid configuration choices to evaluate trends in the commercial development of hybrids and identify factors that may alter those trends. Configuration choices considered here include battery duration, battery power capacity, size of the grid interconnection capacity relative to the generator power capacity, the size of PV panels relative to the inverter capacity, and the way that batteries and generators are coupled. We find that the battery duration and battery capacity have the largest impact on the net value of solar and wind hybrids, with the most attractive hybrids having a two-hour battery duration. We find that it is more attractive to set the interconnection capacity to accommodate simultaneous discharge of the generator and the battery, as opposed to limiting the interconnection capacity to the generator power rating, particularly for solar hybrids in the ERCOT and SPP markets. The choice between AC and DC coupling and the sizing of the PV panels relative to the inverter in solar hybrids are secondary to other configuration decisions. Our analytical results align with current commercial trends of online and proposed hybrid projects, thereby suggesting that the net value framework we employ can be used to understand recent commercial hybrid development activity.

Traditionally in the electricity sector, we would forecast demand and dispatch generation to meet it. In the future, as the percentage of variable renewable generation continues to rise, we must forecast generation and schedule demand to match it. This suggests a fundamental new way to operate power systems, hybrid or traditional, small or large scale.

Moreover, the ways in which electricity was generated in large central power plants and delivered to passive customers through a one-way transmission and distribution network is radically changing to one where consumers can generate, store and consume a significant portion of their energy needs. This, however, is only the first step of the transformation of the electric power sector, to be followed by the ability to share or trade with others using the distribution network. More exciting and disruptive opportunities are emerging with the increased digitalization of behind-the-meter assets, which in turn can be aggregated into large portfolios of flexible load and generation and optimized using artificial intelligence and machine learning.

In this context, to keep future systems operational and reliable, we must develop flexible demand, which can follow the variable renewable generation.

This presentation highlights insights from Variable Generation, Flexible Demand, a recent book edited by the author on the role of smart aggregators who can manage large portfolios of flexible demand, which can take advantage of variable renewable generation at all times.

Continuous reduction over the years of incentives/subsidies for the Onshore renewable generation sources require participation of different renewable assets into the ancillary services markets for accessing new revenue workstreams. One of these renewable projects is Haringvliet Hybrid Power Plant (HyPP). It is considered as the first utility scale hybrid plant in Europe [1] and combines wind power, solar power and a battery energy storage under the same point of connection with a capacity of 22 MW, 32 MW and 12 MW, respectively. The battery is used to participate in the ancillary services market called Frequency Containment Reserve (FCR), while the renewable generation sources in the Energy Market mainly.  

To operate such complex system, new control philosophy needed to be developed over the past years, referred to here as Hybrid Power Plant Controller (HPPC). Its development progress was covered in [1] [2]. This paper considers the development of new HPPC features to facilitate the compliance with the FCR requirements on a HyPP level rather than the battery solely.  

The Haringvliet HyPP was commissioned in early 2021. At the same time, Vattenfall’s in-house developed HPPC successfully took the role of coordinating and supervising the power production at site. Different functionalities of the HPPC, such as the  active power control (power level adjustment and frequency support) as well as reactive power control (power factor control, voltage control and Q-control) are all tested and operational.  

This paper first presents a selection of field results from the Haringvliet site, where the FCR support is only provided by the battery asset, demonstrating the control performance under various operational modes. Furthermore, the paper provides simulation results demonstrating the newly proposed HyPP frequency controller with different capabilities such as distributed FCR volumes, FCR distribution priorities along internal components and reactive power support that can be added alongside the previous scenarios. These simulations are designed to cover different frequency ranges (under, over and dead band). Eventually, an active power dispatch signal is being sent to every single asset in the HyPP upon the calculation of both normal and FCR dispatches required.  

The simulation results of the new feature show that it can be utilized in future HyPP projects upon further development and prequalification process of the plant’s assets. 

  

[1] Raducu, A. G., Styliaras, N., Funkquist, J., Ionita, C., & Ab, V. (2018). Design and Implementation of a Hybrid Power Plant Controller. In 3rd International Hybrid Power Systems Workshop.  

[2] Pombo, V., Raducu, A. G., Styliaras, N., Sahin, O., Thanopoulos, S., Funkquist, J., Shayesteh, E., V. (2020). The First Utility Scale Hybrid Plant in Europe The Case of Haringvliet. In 5th International Hybrid Power Systems Workshop. 

In recent years, the attention in the academia and industry is being shifted to combine and integrate technologies that minimize the greenhouse gases emissions per delivered energy unit. In this respect  hybrid power plants (HPPs), which co-locate wind power plants (WPPs) and battery energy storage systems (BESSs) behind same grid connection point, are becoming more popular nowadays. 

To maximize profits in electricity markets, HPP operators use forecast of market prices and incorporate it into the energy management of HPPs. Currently, the accuracy of forecasts of market prices is not good enough for energy management of HPPs and this is the case especially for regulation prices, where there are not yet well developed forecasting techniques. Forecasting of regulation prices is especially difficult due to stochastic nature of power generations and loads going out of service due to faults. Therefore, a sound processing of forecast error is highly needed, as large forecast errors may cause aggressive or conservative operation strategies, which reduce the profits for the HPPs. For example, for balancing market, the profits may even be negative, if balancing reserves are expected for up regulation; however, in reality the required balancing is for down regulation and vice versa. In order to counteract such challenges, the development of an HPP energy management system (EMS), which incorporates prices forecast errors in the optimization algorithm, is important. 

This paper focuses on preliminary investigation of Hybrid Power Plants (HPPs) operation in balancing market in 2030. The opportunities of balancing market are firstly analyzed. Then the 2030 market information is simulated by balancing tool chain. Spot market optimization and balancing market optimization are introduced sequentially. For balancing market optimization, a scenario based stochastic optimization is applied to deal with the forecast errors of regulation price. By leveraging multi-price scenarios, the objective function is to maximize expectation of profits. In case study, market scenario of 2020 and 2030 are compared firstly. After that, we define two cases to simulate HPP operation in 2030. The case when HPP only participates in spot market is designed as a benchmark case to evaluate the value of balancing market. The investigation assumes an HPP located in West Denmark (DK1) and therefore applies the market rules for this area. Simulation results demonstrate that HPP can receive 11% increase of revenues in balancing market, but due to the high degradation costs of battery, the profit increase is 5.9%.

This paper discusses the impact of the new electricity matrix on the behavior of the electrical system in the Brazilian Northeastern region, showing the challenges faced by a new configuration in which hydroelectric plants operate proportionally with few machines and there is great penetration of wind and photovoltaic power plants, reducing the mechanical inertia present in the grid in addition to reducing control resources associated with hydroelectric plants. Suggests alternatives to compensate for these losses, which should be stimulated by regulatory agents.

Designers of solar energy systems constantly opt for a photovoltaic generator power higher than the inverter power, considering the Sizing Factor Inverter (SFI) inferior to the unit to reduce costs. However, this can decrease inverter lifespan and increase inverter power clipping losses. The main goals of this research are to: determine a range of SFI values for wich higher values of annual average productivity and performance ratio of photovoltaic systems are obtained, in regions of semiarid climate, and analyze the influence of climatic factors - such as wind speed and relative humidity - in the SFI calculation. The methodology proposed for the execution of this research consists of: i) analyzing models for determining the output powers of photovoltaic modules and inverters; ii) study the effects of wind speed and relative humidity in the calculation of the operating temperature of photovoltaic cells; iii) use climate databases to calculate the FDI, to relate this parameter to geographic location; and iv) develop simulation programs and results analysis. The results of this research are the development of a methodology for calculating the SFI that considers the influence of relative humidity and wind speed on the operating temperature of photovoltaic cells; demonstrations that in semiarid climates it is appropriate to use SFI in the range of 0,9 to 1,1 and contributions to the construction of a map that contains intervals of FDI values for which better merit indexes of photovoltaic systems in the brazilian semiarid.

Keywords-photovoltaic systems; semiarid climate; sizing factor inverter; productivity; wind speed.

Variable renewable energy (VRE) participation in ancillary services (AS) markets could provide

new sources of value for resource owners and new options for system operators to manage grid

reliability. From the perspective of VRE resource owners, AS market revenues could help to

offset expected declines in energy and capacity value as VRE penetrations increase. From the

perspective of system operators and the electricity system, VRE participation in AS markets

could provide lower-cost reserve capacity and additional tools for relieving unit commitment and

ramping constraints.

In the United States, however, VRE participation in organized AS markets is currently low or

nonexistent and many questions around the economic value of VRE participation in these

markets remain unanswered. For instance, how would the economic value of AS market

participation to resource owners and to the electricity system as a whole compare between solar

and wind generation, between standalone and hybrid VRE, across the seven organized electricity

markets, and between different AS products? How might the economic value change with higher

VRE and storage penetrations? What changes in market rules would be needed to allow VRE to

participate in AS markets?

This paper examines the economic value of VRE participation in AS markets from resource

owner and electricity system perspectives across the seven U.S. electricity markets. The analysis

uses a price-taker dispatch model with simple, consistent assumptions that facilitate comparisons

across technologies, VRE configurations, and markets over time. It considers two kinds of VRE2

configurations: (1) standalone VRE facilities, with a standalone solar or wind facility; and (2)

hybrid VRE facilities, with a solar or wind facility paired with battery storage.

In a base case, the analysis focuses on VRE participation in regulation markets using historical

market prices, with interconnection capacity limits sized to the VRE facility’s nameplate

capacity. It also examines sensitivities in which VRE participates in spinning reserve markets,

VRE participates in future regulation markets in electricity systems with higher renewable

penetration, and where interconnection capacity limits are sized to the maximum output of the

combined generator and battery capacity (for hybrids).

For standalone VRE owners, the results suggest that the incremental revenues from providing

regulation and spinning reserves would vary significantly across ISO/RTO markets, across years,

and between solar and wind. For some resources in some markets, the average incremental value

may be non-trivial. For instance, average (2015-2019 market prices) incremental revenues for

providing regulation services in CAISO (solar/wind), ERCOT (solar/wind), and SPP (wind) were

$1.4-3/MWhPC (+6-15%). In other markets and for solar in SPP, incremental revenues were

$1.0/MWhPC (+3%) or less. Regulation markets are, however, relatively thin (< 800 MW in each

direction), and even in ISOs/RTOs with higher incremental value expanding market participation

to VRE and energy storage may lead to market saturation and a decline in AS prices.

Participating in spinning reserve markets added little incremental value for standalone VRE

owners, outside of ERCOT and, to a lesser extent, CAISO. This result underscores that, in most

markets, most of the reserve market value for standalone VRE owners would be in providing

regulation reserves, though differences between ERCOT and other markets suggest that this

result is sensitive to differences in market design and AS procurement practices. The high VRE

penetration sensitivity showed significant increases in the incremental value of regulation market

participation for standalone VRE, due to higher regulation prices and a higher frequency of hours

in which regulation prices exceed energy prices.

At current market prices, revenues from regulation and spinning reserve markets are not large

enough to meaningfully offset declines in solar and wind resources’ energy and capacity value as

their penetrations increase. At higher VRE penetrations, regulation and spinning reserve market

revenues may more meaningfully reduce value declines in some markets.

For hybrid VRE owners, incremental revenues were, as expected, several-fold higher than for

standalone owners, though variation across markets highlights differences in storage value due to

different market designs and resource mixes. In the near term, the results suggest that AS

revenues could be a significant part of hybrid VRE business models, with the POI sensitivity

showing that most of the regulation value of hybrids could be captured with POI capacity limited

to the VRE facility’s nameplate capacity when storage is sized to 50% of VRE capacity.

However, hybrid VRE faces the same uncertainty around AS market prices that standalone VRE

does.

In most ISOs/RTOs, standalone and hybrid VRE participation in regulation markets could

provide significant value to the electricity system as a whole, as measured by the difference

between VRE resources’ average regulation value and average regulation market prices. In other

words, VRE could provide regulation during periods with high market prices, which would put

downward pressure on average market prices and provide ISOs/RTOs with a larger toolset to

resolve emerging, higher-cost system constraints. The results show that, in general, VRE

provision of regulation services in ISOs/RTOs with separate upward and downward regulation

products was higher than in ISOs/RTOs with bidirectional products. Hybrid VRE provided more

regulation service and often, but not always, had higher regulation value than standalone VRE.

The results provide insights on two priority areas for considering VRE participation in ISO/RTO

reserve markets. First, developing separate upward and downward regulation products, for

ISOs/RTOs that do not have them, will enable more efficient use of VRE and storage resources

in regulation markets by taking advantage of the fact that these resources have very different

opportunity costs for upward and downward reserves and that prices for upward and downward

regulation tend to be poorly correlated. Second, and similar to the CAISO’s strategy (CAISO,

2020b), focusing initially on VRE hybrid participation in AS markets may be a more efficient

first step toward expanding market participation, given that hybrids will provide more reserves

than standalone VRE and will generally have higher AS value. That being said, ultimately it may

be beneficial to enable both kinds of resources to participate in AS markets.

Grid-connected Energy Storage Systems (ESS) are vital for transforming the current energy sector. Lithium-Ion Battery (LIB) technology is presently the most popular form of ESS, especially because of its fast response capability, efficiency, and reducing market prices, but is not always preferred for long-term storage, due to its relatively shorter lifetime. A Redox Flow Battery (RFB) on the other hand has a higher lifetime and better long-term storage capability, but has a higher upfront cost and reduced round trip efficiency. A Hybrid ESS (HESS) consisting of LIB and RFB offers the advantages of both technologies, thus making the ESS more economical and flexible to use while also improving the cycle lifetime of individual ESS. Such a grid-connected HESS is planned and installed for a student residence at Bruchsal having 126 apartments for 150 students and equipped with 220 kWp photovoltaics and 10.5 kWp wind-power. Real-time high-resolution data of the residence’s electrical load and energy generation are collected and used to optimally control the HESS. Additionally, the RFB is also used as heat storage, which supports partial heating requirements of the residence.

In the present work, an Energy Management System (EMS) is deployed which not only controls this conglomerate but also optimizes its operations in real-time. Additionally, an in-housebuilt independent controller for the power-to-heat operation is installed, which works together with EMS to store and extract heat from the RFB. The EMS aims at running the whole system at the lowest operational cost, while also reducing the aging process of the HESS. The EMS is also backed up with energy generation and consumption forecasting algorithms, which enable it to intelligently predefine not only the energy flow, but also the ratio of the energy form, i.e. electrical and thermal.

1. INTRODUCTION 

This study aims to integrate the Floating Solar Power Plants in the reservoirs of Hydroelectric Power Plants. In March 2016, Brazil has pioneered the launch of this type of energy by creating solar power plants on floats at  Hydroelectric Power Plant. The objective was to integrate the solar plant with the operation of hydroelectric power plants and evaluate the influence of this integration on the ecosystem of the reservoirs.

2. WHAT ARE RENEWABLE PLANTS IN RESERVOIRS?

For Solar Floating, the plates are installed on types of buoys that float in large lakes, normally the same ones used by hydroelectric plants, as in the case of dams.

3. HOW THE INITIATIVE HAS BEEN DONE IN BRAZIL?

The project started in March 2016 at hydroelectric power plants, which is located in the state of Amazonas and in the Brazilian Northeast respectively, as a way of taking advantage of the large space provided by the lake's water mirror, such as the substations and transmission lines that were underused in the regions.

In this study, the feasibility of integrating the renewable source of hydroelectricity with solar sources is being verified, these sources are to be used in large proportions, in Brazil, there is still a reduction in the costs of energy produced by solar plants.

At the same time, this initiative has been seen as an excellent alternative to assist in the production of electricity from other sources and, consequently, the use of production capacity is already being expanded to the Northeast dam, which is located in the São Francisco River.

4. WHAT IS THE CAPACITY OF EACH SOURCE?

The initial implementation of the pilot plants in the reservoir was started with a generation of 1 MWp. As the EletroCenter has a capacity of 5MW, the study allows for a glimpse of other connected sources such as Offshore Wind and Battery, with a capacity of up to 5MWp.

5. WHAT ARE THE ADVANTAGES OF RENEWABLE SOURCES?

The plates require an initial investment, but the savings generated by not paying the electricity utilities to compensate for the amount paid initially. Best of all is that, even in places where there is not so much sun or wind, this type of energy can be stored in batteries.

6. AUXILIARY SERVICES PROTECTION STUDY FOR CONNECT 

This study aimed to calculate the short circuit currents and the appropriate adjustments for the protection relays of the Auxiliary Services system to be implemented in the Initial Stage 2Mwp and Final Stage 5 MWp of the Hybridization project with the Photovoltaic Source (PV).

We emphasize that some of the adjustments for the relays in the feeders/pathways of the motors to be indicated in this study were reassessed, depending on the current loads and field measurements, during the implementation process.

This study included the adjustments and coordination of the protection relays of the following Switchboards and Load Centers, related to the supply of energy to the auxiliary equipment of the generating units numbers 1, 3, and 5, and to the general auxiliary services 13.8/0 .38 associated KV.

From the database collected in the field related to equipment, devices, and interconnection cables, the study will establish the maximum and minimum values ​​of short-circuit in the collective bars of these panels, thus defining the ranges to adjust the respective protection relays. In addition to the parameterization of the relays, actuation curves were presented to demonstrate the selectivity between the protections in cascade.

7. CONPROVE PS SIMUL SOFTWARE APPLICATION FOR FAT AND SAT

A protection planning application for modeling and simulating energy systems and for analysis and protection for short circuit studies, stability analyses, integration studies of renewable sources in the grid; for the analysis of power generation from hydro and solar renewables, including inverter-interfaced generation. Software similar to PSSE, PSCAD / EMTDC, DigSilent Power Factory but national and that was tested by the University of Protection Laboratory with renewable model sources.

Renewable energy is intermittent by nature, so they are often backed up by fossil power (in many cases fuel oil with a high carbon footprint). Hybridizing such power systems by integrating biofuels- and hydrogen-capable power generation, energy storage, flywheels, and synchronous condensers for grid balancing paves the way to a more decarbonized, sustainable, and even less costly energy system. Remote, off-grid areas have a growing need for sustainable energy that is reliable and affordable. Hybrid systems are being developed with the goal of reducing – or even preventing – carbon emissions via increasing the share of renewable energy. Smartly coordinated microgrids, hybrid power plants and energy parks can make a tremendous contribution to decarbonization. Storage systems enable higher utilization of renewable energy (less curtailment) and reduce the need for additional backup power. This also leads to reduced fuel consumption and dependency on fuel imports. Equipped with autonomously operating control systems utilizing real-time algorithms and weather forecast, hybrid systems can produce first-class results in an economical and environmentally optimized manner.

Siemens Energy offers several pathways for transforming remote energy generation from fossil to less carbon-intensive and renewables-dominated power generation systems. The decarbonization depths depends on the specific customer goals, geographic renewables potential and availability of financing. Starting with measures to increase efficiency of existing technology, over “fuel shift and hybridization” up to “deep decarbonization” technologies, SE has proven to be a reliable, efficient, and innovative partner and one of the very few OEMs with most of the green solution technologies in-house.

On the example of a real-world application, it shall be shown how Siemens Energy supports the energy transition of customers towards a cleaner and more sustainable energy future. Special focus is put on the impact of different levels of decarbonization and the respective effects on CO2 reduction and economics.