DER Integration | SMART GRID 智慧電網

1.Taiwan Electricity Trading Development

Taiwan power company (hereinafter referred to as “TPC”) has made it a priority to enhance the flexibility and resilience of the grid in order to achieve net-zero emissions. Firstly, in 2019, TPC launched Non-Conventional Power Resources Participating Ancillary Services on Electricity (NCPRS), a program for end-user to reduce load or use their own electricity generation equipment. This program successfully attracted more than 84MW of resources to participate, and these resources can be used as a conventional generation unit to provide spinning reserve for the Central Dispatch and Control Center (CDCC). Along with the establishment of the market operator of TPC and with the participation of the international power industry, the average executive rate of ancillary service provided by these resources are over 106%. This result can be seemed as the achievement of the LAAR (Load as a resource) goal.

In addition, TPC has also planned how to use energy storage system (ESS). In collaboration with domestic enterprises and ESS manufacturers, TPC has initiated the "Asia's first" AFC project to procure 15MW ESS resources providing frequency regulation services. These AFC ESS resources can automatically follow the frequency variation and can adjust its output/input within 1 second. The functionality of AFC ESS resources has been proved during the blackout incident happened in 2021, which means that they have the capacity to prevent the power grid contingency.

Based on the success of the AFC project mentioned above, Taiwanese government has drafted a formal regulation concerning the “Energy Trading Platform” which instructed TPC to establish a " Energy Trading Platform "(ETP) in July 2021. Nowadays, along with the participation of the utility generation enterprise, TPC has successfully recruit dozens of enterprises to participate in the ETP. TPC also created the role of QSE which ask participants of ETP to pass the ETP Proficiency test, and there has been more than thousands of people passed this test. The capacity of resources which has registered to ETP has over than 170MW until the end of January 2022.

TPC expects also to create a new trading product in July 2022 for long-term ESS and expects to implement 1,000MW ESS in 2025. It is expected to provide smoothing and load-shifting services to the grid.

Along with the energy transition goal in 2025, it is expected to obtain more than 3,900MW power resources with various types through ETP. TPC also plans to further open the intraday imbalance energy market. With the participation of these dispatchable power resources, Taiwanese power grid can be one of the most sustainable and robust grids in the world, which can also bring greater confidence in the path to achieve net-zero emission goal.(Currently, the types of decentralized power resources acquired include ESSs, electric vehicle charging stations, telecommunication equipment rooms, self-generating equipment, cogeneration, demand response from industrial or domestic users, etc.)

2. Demand response

In order to increase the reliability of power supply and energy efficiency, Taipower has introduced demand response programs since 1979. The following programs have been implemented at present:

Time of Use Rates
Seasonal Rates
Off-Peak preferential Rate for Ice Storage Central Air Conditioning System
Demand Response & Load Management Program
- Scheduled Load Reduction Program
- Emergency Load Reduction Program
- Demand Bidding Program
- Interruptible Air Conditioning Program
- Emergency Demand Response Program

The performance of demand response programs

In order to reduce the demand for power and the growth of peak load, Taipower has implemented demand response program to encourage customers to transfer the period of production process from peak load to off-peak load. In August 2021, which was the month with the most users joining “Demand Response & Load Management Programs (excluding Interruptible Air Conditioning Program)”, 2,151 customers applied and the amount of contracted reduction load was 2,651 MW. During the peak day (Jul 27, 2021), the peak load was clipped by 1,069 MW.

3. Energy storage system

Grid Scale ESS
Moving towards the goal of climate and lower-carbon actions, Taiwan is developing green power actively, along with the installation of energy storage systems (ESS). According to the Forward-Looking Infrastructure Project, the Bureau of Energy, Ministry of Economic Affairs has launched the “Regional ESS Technology Verification Project”. Therefore, Taiwan Power Company (TPC) and Industrial Technology Research Institute (ITRI) have cooperated on developing ESS in Taiwan. ESS can not only smooth green power generation, but also maintain power system frequency stability. In addition to those advantages, it also increases the capacity value of renewable energy and solves the problem of power dispatching.

The target for Battery Energy Storage System (BESS) in 2025 is 1,000MW. TPC will build 160MW of equipment in own site and purchase 840MW through ancillary services. BESS can help smooth the intermittency of variable renewable energy. After a power system accident, it can help withstand the trip of one largest unit without touching the low-frequency relay action to trip the user load. The 840MW energy storage ancillary services include 500MW with energy transfer function, which can help relieve the pressure of night peak load.

TPC has completed energy storage battery systems at two sites, including Kinmen with a total of 3.8MW (11.8MWh) and the Sulin branch of Taiwan Power Research Institute with a total of about 1.25MW (1.9MWh). At the same time, ITRI has also completed energy storage battery systems at TPC's Solar PV sites in Yong-An Kaohsiung, Long-Jing Taichung and Zhangbin Changhua, with a total of about 6.5MW (6.4MWh). At present, there are 40MW BESS on construction. In addition, TPC expects to purchase 131MW of battery energy storage equipment in 2022.

In 2020, TPC also purchased 15MW automatic frequency control (AFC) ancillary service from five private companies. These energy storage battery systems have started operation in 2021.

In 2021, the power trading platform has been established. and the frequency regulation ancillary services of energy storage will be obtained from the Day-Ahead ancillary services market. At present, February 2022, the qualified trading capacity is 19.1MW.

Unit：MW

Kinmen Energy Storage System

Kinmen is an islanding power system. As renewable energy penetration increases, a possible way to make the power system more reliable is to install energy storage system (ESS). TPRI has already installed two sets of ESS in Xia-xing Power Plant, which not only assist power system operation but also enhance the knowledge and dispatch experience of ESS.

The power type of ESS uses Li battery(2MW/1MWh), which has already been constructed in December 2009. This system provides power system ancillary services and spinning reserve, carries out functions like renewable energy smoothing, frequency-watt control, voltage-var control and frequency deviation-P control. The energy type of ESS uses NaS battery(1.8MW/10.8MWh), which has already been constructed in December 2020. The main purposes are to execute load transformation, adjusting renewable energy generation period, and increasing diesel engine’s dispatch flexibility.

Green Energy Smart Management System of TPRI Sulin branch
The green energy smart management system installed in the Sulin branch of Taiwan Power Research Institute(tpri-EMS) was designed base on micro-grid concept. The tpri-EMS is consists of 9 energy management subsystems, including the photovoltaic storage test site. By 2021, the performance test and verification of all-vanadium redox flow batteries and lithium-ion battery energy storage systems have been completed. In the future, the focus will be on the development of application functions of energy storage systems in microgrids, such as peak shaving, load tracking, automatic demand response, reduction of contract capacity as well as photovoltaic smoothing.

tpri-EMS (left：homepage, left：peak shaving demonstration screen)

Evaluation of all-vanadium flow battery in renewable energy storage
With an aim to increase the ratio of renewable energy to the total power generation to 20% in 2025, Taiwan Power Company has actively been promoting solar power generation and wind power generation. Taiwan Power Research Institute (TPRI) has conducted energy storage demonstration experiments for smoothing renewable energy generation and controlling peak power demand. To successfully achieve these goals, TPRI has introduced an all vanadium redox flow battery’s energy storage system from Sumitomo Electric Industries Ltd. in May 2016. This 125kW/750kWh system was installed at Shulin branch of TPRI in February 2017. Battery performance test, demand response, renewable energy smoothing, island mode operation, and cost minimization are tested in this system. In addition, a 250kW/400kWh and a 1.MW/1.5MWh container type lithium-ion battery energy storage system from local company has been constructed in this area in 2019.

Demonstration and experimental study of a flywheel energy storage system for long duration applications
Flywheel Energy Storage System (FESS) stores energy by converting the electricity and the spinning kinetic energy with a bidirectional power conversion device. FESS is suitable for use cases that require hundreds of thousands cycles of charge & discharge. The power output ranges from kW to MW within a short period of 1 second.

FESS is one of the oldest energy storage mediums. The performance in terms of energy storage density, energy efficiency, power, and response time of the FESS is outstanding. Using mechanical energy for energy storage has advantages of long cycle life, reliable operation and zero impact to the environment. The energy efficiency of the FESS depends on manufacturing materials, electrical machines, types of bearing, and the vacuum chamber housing the rotor. The State of Charge (SOC) of the FESS can be directly calculated by monitoring the rotational speed of the flywheel which effectively improves the reliability of the power management system.

In general, most FESSs can provide high power instantaneously with short duration. However, the FESSs providing the long charge and discharge duration for peak shaving and energy shifting is rare. Therefore, a FESS with rated power of 8kW, discharge duration of 4 hours, and 32 kWh energy has been installed by TPRI in TPC in February 2019. The FESS is tested for various technical characteristics, and the reliability and corresponding performance of the specification have been demonstrated for the reference of application in the future.

After several earthquakes with magnitude 4 and magnitude 6 on the Richter scale, the flywheel system still works continuously. It also can be operated stably in summer without the use of air conditioning. The manpower and material costs required for operation and maintenance are extremely low, and only the vacuum pump needs to be maintained annually. The flywheel is expected to be worn out after long-term operation, and it only needs to replace the bearing for continuous running. It has great advantages in enduring application and provides reliable and stable backup power.

Related Regulations
To respond to domestic renewable energy development and energy management demand, energy storage equipment, installed by consumers, is a great tool which can be used with demand management and participate in ancillary service, is beneficial to improving power system stability.

To meet the demand of domestic energy storage equipment installation, TPC announced guidelines for grid connection of energy storage system on March 6, 2020.

4. GEMS & DREAMS

DREAMS with Smart Inverter
In response to the policy of energy transition in our country, a huge amount of renewable energy will be incorporated to the power distribution system in the future. In order to solve the problem of the power distribution system limited by grid installation strength and intermittent power generation characteristic of renewable energy system due to maximum grid hosting capability, the “Distribution Renewable Energy Advanced Management System (DREAMS,shown in Figure)” can be used in coordination with smart converted to reduce the power factor of renewable energy system to absorb the virtual work in order to maintain the voltage quality. In addition to the effective management of the impact of renewable energy on the power distribution system, the simulation analysis of power distribution feeder can verify that, under the same voltage variation constraint, the incorporation of “Distribution Renewable Energy Advanced Management System (DREAMS)” in conjunction with the self-adjustment function of smart inverter can enhance the permissible hosting capacity of renewable energy system of the feeder by more than 20%.

Figure . Distribution Renewable Energy Advanced Management System (DREAMS)

DREAMS Planning and Construction Schedule

The power generation information of the sites with renewable energy system installation of more than 500kW will be collected according to TPC DNP3.0 communication protocol. The information shall include power generation volume of actual and virtual works, power factory, voltage at duty point, and relevant set values. The aforementioned information should be sent back to the “Distribution Renewable Energy Advanced Management System (DREAMS)” via 4G communication system.
In mid-to-long-term the “Distribution Renewable Energy Advanced Management System (DREAMS)” is expected to be interfaced with “Advanced Distribution Management System (ADMS)” to execute remote monitoring of renewable energy site via transmission of control command to the smart inverter of renewable energy in order to enhance the grid resilience and to maintain good power supply quality based on maximization of renewable energy.

DERMS Planning in Future
The future plan is to adopt “Distribution Renewable Energy Advanced Management System (DREAMS)” in coordination with “Advanced Distribution Management System (ADMS)”, so the network topology architecture can be updated in real time according to the switching operation decision of dispatch of power distribution system. And the system impact analysis can be conducted based on the power generation information of renewable energy collected by the renewable energy management system in order to derive the control decision of renewable energy smart inverter. In the end the control station and download the aforementioned control decision to the smart inverter via 4G communication system to achieve the modulation of renewable energy system power output in order to provide the auxiliary service function required by maintaining the safe operation of power grid.

Green Energy Estimate and Monitor System (GEMS)
The statute stipulates that renewable energy sold greater or equal to 500kW must return power generation information to the Taipower dispatching control center. Most solar photovoltaic power generation information is not returned to the dispatching center. As the end of December 2021, the total system installation solar photovoltaic capacity was about 7.7GW. In order to accurately grasp the instantaneous power generation of private solar photovoltaic power plants, Taipower sets up a Green Energy Estimate Monitor System (GEMS). The GEMS’s model uses the monitored power plant as the basis to estimate the power generation of neighboring unmonitored power plants. The GEMS will count the entire solar photovoltaic power generation in Taiwan.

Open Information Online Hosting Capacity Map

Background information
In recent years, with the government expanding its efforts to promote the green energy development policy, related renewable energies such as photovoltaics, wind power, hydroelectricity and geothermal power, all of which are Distributed Energy Resources (DER), will be massively grid-connected to the distribution system, and it will significantly change the entire distribution network structure. The electric power will no longer be generated by the generator units in large power plants, but rather be generated by small and decentralized devices. In order to fully understand the grid-connection status of the renewable energies, Taipower began to develop the Distribution Planning Information System (DPIS) since years ago, attempting to regulate the possible impact to the system when those energies are grid-connected by adopting the application review mechanism for Distributed Energy Resources.

According to records, there are nearly 10,000 feeders in the power distribution lines in Taiwan. The amount of data is huge and its number in the hosting capacity sections is as high as 3.26 million. When presented on a traditional web-based graphics platform, it would consume a considerable amount of software and hardware resources and may result in performance problems caused by a large amount of map data loading. Therefore, the Map Tile display technology will be used to generate the map tile files after the incorporation of timed calculations of each hosting capacity section, and then combined with the TGOS Address Geocoding Service and the generic version of the electronic maps to construct the visualized distribution feeder hosting capacity system. The system provides the public or the industry to conduct a location query by means of an address to achieve the purpose of visualizing the distribution feeder hosting capacity

System architecture description
The system is divided into two parts: the internal system and the external system. The architecture picture are shown in Fig1.

In order to allow external users to have a more intuitive understanding on the possible hosting capacity of feeder line, this project will regularly extract the topology information of existing distribution equipment from each business branch of Taipower by using the Extract-Transform-Load (ETL) technology. This project then simplifies it to become the information structure required to calculate the possible hosting capacity and subsequently summarize and send it to the information center as the basic information for computation.

We tested several computing cores and compared their benefits. Analyze its accuracy and calculation speed, and choose the best one.
Calculation results will integrate to the Geographic Information System (GIS) technology and displaying the possible hosting capacity of each feed line section on the map with colors.

Furthermore, to solve the performance issue that may be caused by external users downloading a large number of map data, this project constructs a feeder hosting capacity visualization system by using Map Tile display technology. It was thereby achieving the establishing hosting capacity visualization of the feeder.

Fig 1. The architecture of Feeder Hosting capacity visualization system

Power system impact analysis

This system integrates data from several systems automatically, such as Distribution Mapping Management System, Renewable Energy Management Systems, Distribution Planning Information Systems, etc. Input data mainly include wire parameters, transformer parameters, electrical connectivity, power distribution equipment data, transformer data, load data, renewable energy data, user data, coordinate points, etc. Comprehensively organize all the materials and build a complete feeder input file. The schematic diagram of power system impact analysis is shown in Fig.2.

Taipower has about 10,000 total feeders, and the number of calculations for each joint is very large. Considering the overall load of the mainframe and the accuracy of the data, the core of the most cost-saving calculation is adopted. Each joint will be inversely calculated one by one, and get the maximum hosting capacity finally. It will be the basis of updating the externally displayable hosting capacity.

Fig 2. Schematic diagram of power system impact analysis

System introduction
In order to allow the user to clearly view the hosting capacity of each section of feeder, we indicate the hosting capacity of each section by means of color display. This referred to the webpages which are built by the foreign electricity utility.

The hosting capacity is divided into six levels and six colors from small to large, and display on the geographic map.

Feeder hosting capacity visualization system for power distribution system：http://hcweb.taipower.com.tw/
Line hosting capacity visualization system for Transmission power supply system(Due to national security issues, only opened for internal use)：http://pvgis.taipower.com.tw/ltfl/

Fig.3 to Fig.8 below show the actual screenshot and function name.

Fig3. System introduction page

Fig4. Side information bar

Fig5. System description and notices

Fig6. System description and notices

Fig7.Legend and layer switch

Fig8. Feeder information

6. Design of Platform and System for Power Wheeling and Direct Supply in Taiwan

Background
In Taiwan, the Electricity Act is passed in January 2017. This act has activated the reform of electricity liberalization. To alleviate the impact of the reform on the current system, the first stage will be the so-called “renewable energy first,” which means that free trading of green energy is permitted and consumers are allowed to choose their power suppliers. Trying to learn from other countries’ experiences and see if they can fit well with our industrial structure, TPC is now working on the formulation of regulations for power wheeling and grid-connection type direct supply, and also establishing the “power wheeling & direct supply platform” on which relevant works can be done.

Project contents
The structure of power wheeling and grid connection type direct supply is shown in figure 1. Power wheeling means that power source can transmit power to customers through grid company; grid connection type direct supply means that customers are connected to power sources through private lines. Renewable energy, Due to their intermittent property, are still considered as unstable power source. Therefore, when there is surplus or lack of power, TPC, as an electricity retailing utility enterprise, is responsible of maintaining stable power supply.

Figure 1 Illustration of power wheeling and grid connection type direct supply

The purpose of “power wheeling & direct supply platform” is to promote the service of power wheeling and direct supply. Figure 2 shows the structure of the platform. With the help of AMI, which precisely records power generation and consumption every 15 minutes, the amount of power, either delivered through power wheeling or direct supply, can be analyzed and used as the basis of reviewing of “bundled renewable energy certificate.”

1. Providing compound ways of selling power
In the past, power generated by renewable-energy-based electricity generating enterprise are sold to TPC at price of the feed-in tariff announced by the government. Now, the power wheeling & direct supply system can provide renewable energy developers with compound choices of how they are going to sell their power, as shown in figure 3.

Figure 3 Electricity market in Taiwan

2. Satisfying needs of industries
Many corporations had already announced that they will use green energy as their power source. Also, the government also legislate that the percentage of green energy usage should reach specific degrees. The power wheeling & direct supply system can help corporations not only satisfy the regulations set by the government but also acquire the bundled renewable energy certificate.

3. Set the foundation for overall electricity liberalization
Electricity liberalization is a global trend of electricity development. Through completion of relevant regulations and operating scheme, step by step, during the process of promoting electricity liberalization, this project set a foundation for overall electricity liberalization.

4. Advantages of the platform
The “power wheeling & direct supply platform” possesses several intact functions such as wheeling contract management, power consumption computing, post-billing , etc. Also, the platform is able to integrate with power acquisition mechanism and public electricity retailing mechanism. In the future, in face of overall electricity liberalization, this platform can be expanded as a mid- and long-term electricity transaction management platform.

Benefits of the project
1. Benefits for TPC
It is believed that the promotion of power wheeling & direct supply system can help TPC adjust its organization and nurture relevant employees to make sure that overall electricity liberalization is successful in the future.

2. Benefits for customers
The power wheeling & direct supply system can offer customers compound ways of purchasing electricity. Through marketing mechanism, customers are free to choose their own power supplier to satisfy their needs of green energy purchases. Also, combination of different retailing schemes can help corporations reduce their cost on power consumption.

3. Benefits for industries
Through marketing mechanism, corporations can be more competitive and efficient in their performances. In addition, more corporations can be attracted to invest in the development of renewable energy technologies.

4. Promoting construction of smart grid
Customers who participate in the platform of power wheeling and direct supply are required to install AMI smart meters. It is helpful for increasing the penetration of AMI and speeding up construction of smart grid.

5. Speeding up renewable energy development to meet the government goal
By 2025, it is planned that the percentage of renewable energy generation shall reach the government goal of 20%. Through promotion of mechanism of power wheeling & direct supply to establish a market that is equitable and sound, more corporations can be encouraged to participate in the green energy industry. Thus, the goal of energy transition can be achieved.

Conclusion
Electricity liberalization has become a global trend. In Taiwan, regulations, techniques, industrial environment, and social consensus are all mature and ready for electricity liberalization. The mechanism of power wheeling and direct supply will kick-start the electricity liberalization in Taiwan. Also, the power wheeling & direct supply platform is beneficial for execution of power wheeling and direct supply contract. It is expected that through sound planning we will be able to reach the goal of electricity liberalization.