Implementing Smart Grid Technologies in China: Experiences and Future Approach

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1 1 Implementing Smart Grid Technologies in China: Experiences and Future Approach Presented by Jin Zhong and Qinwei Duan The University of Hong Kong Hong Kong SAR

2 2 Smart Grid in China Renewable energy integration Reaching the goal of 10GW wind installed capacity and 20GW solar installed capacity in 2020 Urbanization of the population Population growth in urban areas Energy efficiency & emission reduction Smart meters and home-area networks implementation

3 3 Guangdong Power Grid (GPG) Metrics Currently the largest provincial power grid in China Solely-owned by China Southern Power Grid (CSG) Managing the power grid of 21 cities in Guangdong Province. The service area covers 177,900 km 2, with power supply to population of million.

4 4 Smart Grid Demonstration Projects in GPG Foshan City: Self Healing Distribution System Nan ao Island: Multiterminal HVDC System

5 5 Self-healing Distribution System Definition: The Self Healing Grid is a system comprised of sensors, automated controls, and advanced software that utilizes real-time distribution data to detect and isolate faults and to reconfigure the distribution network to minimize the customers impacted. Main goal: Reduce outages and improve system reliability Methods: Reconfiguring the switches and reclosers installed on the distribution feeder to quickly isolate the faulted section of the feeder and re-establish service to as many customers as possible from alternate sources/feeders.

6 6 Operating Strategy Self-healing Self-sensing: Real-time monitoring of the distribution feeders using smart sensors. Data will be provided to enable the applications. Self-diagnosing: Automatically detecting the fault on the distribution feeder based on gathered data Self-decision-making: Optimally decide comprehensive control strategies in response to the faults Self-recovery: Automatically implementing the control strategies to recover the distribution system and pick up the loads

7 7 System States Security Preventive Control Optimization Control Optimized Alert Recovery Control Recovery Grid-tied Control Emergency Control Emergency Control Islanded Emergency Normal state: contingency prevention; operating state optimization Contingency state: fast fault-locating, isolating and shifting load to nearby feeder; securing critical loads Control strategies: that transform the system from emergency and alert state to normal state

8 8 Hardware Platform Separating Intranet from Public Network. Utilizing the currently deployed automatic control and dispatch system in distribution network. State estimation model incorporating various distributed renewable energy source. Setting the technical standards for Self-healing Control Station and Intelligent Terminal Device.

9 9 System Testing The project is initially tested in Guangdong Finance & Technology Development Region for 1 year in Area of km², 306 MV loads and LV loads, 297.5MVA distribution transformer capacity. Self-healing Control success rate: % 12 preventive self-healing control actions, 100% success rate 560 contingency self-healing control actions, % success rate

10 10 System Implementation Implemented in Electric Power Dispatching Center of Foshan City, Guangdong Province, since January, 2014 China s largest Self-healing Distribution System Project 89 distribution substations Incorporation of distributed generation: Integrated Solar PV- Energy Storage Foshan City distribution network reliability since implemented: %

11 11 Experiences Gained Communication to devices is key to any system Establishing the communication links between devices and control center Relays need to provide correct information for software to work properly Feeder capacity is very important. Excess capacity is necessary for feeders that supply the automation zone.

12 Multi-terminal Flexible HVDC 12

13 13 Advantages Over Two-terminal HVDC Line losses are lower because there is no reactive power flow, Power flow is much more controllable, Stability of connected ac systems is increased, Smaller conductors and transmission corridors are required, Short-circuit currents are limited, Terminal construction can be staged to coincide with load growth, No additional capacity is required for voltage support or stability, Connection is asynchronous, so ac systems of different frequencies or systems with stability problems can be connected, There are no circulating power problems, HVDC systems can continue operation with one line out of service.

14 14 Aim of the Project Integration of large-scale wind farm using conventional HVDC Integrating large-scale wind farm using MT-HVDC Intermittency and variability of wind generation leads to frequent and high fluctuation in power flow in main grid AC connection leads to voltage fluctuation in main grid Difficulty in integrating offshore wind generation over 50km distance Networking of Multi-terminal Flexible HVDC Control strategy in Multi-terminal HVDC Wind farm operation characteristics and control strategies Converter topologies

15 15 Project Network Topology The topology utilized parallel connected voltage source converters(vsc). Flexible power flow distribution; Highly expandable, high reliability; Suitable for distributed integration; Suitable to be built in multi stages.

16 16 Project Implementation Undersea Cable Converter Station ±160kV Wind farm Converter Station ±160kV Overhead Lines Converter Station ±160kV Wind farm The project is implemented in Nan ao Island, Guangdong in December,2013; Operating HVDC link with 3 terminals (3 converter stations), connecting 2 large wind farms; The world s first Multi-terminal Flexible HVDC in operation.

17 17 Operation Results AC, DC parallel connected to DC only DC only to AC, DC parallel connected AC Voltage AC Current DC Current DC Voltage Switching Signal AC Voltage AC Current DC Current DC Voltage Operation mode switch between AC-DC parallel connected and DC; Fast switching control mode without creating pulsation; Re-synchronization control in wind farm side converter; The approach can be utilized in islanded mode control in main grid or micro-grid

18 18 Project Outcomes Large scale wind farm integration through Multi-terminal Flexible HVDC: Networking approach; Mathematical model, assessment and evaluation methods; Key Equipment: Developed China s first hundred kv level Flexible HVDC converter, HVDC cable and multi-terminal protection system; Standardization: High-voltage, large-volume Flexible HVDC Transmission Technology System.

19 19 Conclusion 1. China s smart grid scenario is still focusing on technologically upgrading transmission and distribution systems 2. Research on the true needs of China in the smart grid framework based on the country s geographic and economic situation is highly necessary 3. Renewable energies, distributed generations, microgrids, demand response, smart meter, smart appliances, EVs can all be implemented technologically, but a smart grid framework and plan should address what we need, why we need them and how are they incorporated into the framework