Electric Vehicle: Vehicle to Grid (V2G) Test challenges and solution

The hybrid-electric and electric vehicle (HEV/EV) market has been growing rapidly in India. Electric Vehicle are viewed not only as transportation with clean energy but also as Mobile Energy storage device. As the number of Electric Vehicle increase on road, it can be utilized to connect with Energy infrastructure to manage the load demand. In this paper we are going to talk about Vehicle-to-Grid which is also called as V2G Technology and Test requirements. 

Currently Power Electronics, Automotive Testing and Grid compliance test are seen in isolation. But as the new Technologies like Vehicle-to-Grid evolves, the entire Energy eco-system are going to converge. The Test solutions also need to converge to meet interoperability between Automotive EV, Grid system and Infrastructure. 

Electric Vehicle role in Energy Eco-system: 

Electrical Vehicle are going to play very important role in Energy Eco-system. The growth of electric vehicles and the smart grid has led to the creation of vehicle-to-grid (V2G) technology. Imagine using your electric vehicle to power your home during power outage or transfer the energy from car to Grid. This enables Electric vehicle as mobile Energy storage devices. This would give huge boost to Energy economy to meet peak load power requirements. 

Vehicle-to-Grid Technology:

Vehicle-to-grid technology involves drawing unused power from the car into the smart grid. V2G, which is also known as vehicle-grid integration (VGI), can help the energy grid supply electricity during peak hours. It can also create an extra power source when weather-dependent renewable energy sources are not available. For example, a home that uses solar power cannot generate electricity at night, but an electric vehicle could provide a secondary source of power if needed. 

Electric Vehicle will be used as mobile energy storage devices to meet peak load power condition. 

Power Electronics Component for EV and Vehicle-to-Grid (V2G): 

Electric Vehicle Power electronics involves On-board charger, Battery, converters, Powertain Inverters and Motor. Ametek Programmable power solution offers Power Test solution for above system for Electric Vehicle. 

V2G introduces new Power Electronics system like Smart Grid and Smart Charing station. 

Although the technology to transfer power between EVs and homes is already in place, transferring power from EVs to the smart grid remains in the experimental stage. 

The most important requirement for V2G is interoperability between Electric Vehicle and Smart Grid.   Standardization of Smart Grid, charging station would be the key to success of Vehicle to Grid Technology and IEEE is already working to standardize the same.

Test Challenges for V2G:

Safety, Reliability and interoperability are the most important requirement for V2G system. Power Testing plays huge role to ensure that system meets all safety and performance criteria. 

1. Safety and Compliance standards for Vehicle-to-Grid: The concepts like V2G are young and the standards for performance testing are still evolving. The Test Instruments need to be flexible and future proof to meet evolving standards requirement.  
2. Interoperability between EV and Grid: As the EV and their charging infrastructure is penetrating and integrating into traditional electrical grid, the question about their compliance to grid code of conduct and regeneration behaviour, is becoming more relevant. While Vehicle to Grid integration throws a challenge for the low voltage electrical distribution system’s old infrastructure, it is also bringing an opportunity to support the grid for peak load shaving. 
3. Bidirectional test: Vehicle to Grid Test brings new concept of Bidirectional flow of Power between Vehicle and Grid. Testing bidirectional power flow demands equipment that can source and sink power to the converter. 
4. Accurate Emulation of Real Scenarios: The number of scenarios for Testing are growing exponentially with Grid and Electric Vehicle integrate. These scenarios need to be emulated accurately in Lab environment to meet safety and performance criteria. Mimicking Grid scenarios accurately to test Electric Vehicle is very important to meet safety requirements.  
5. Hardware in Loop Testing: Automotive and Power test requires Hardware in Loop test to test various scenarios. 
6. Multiple Power System Test: The ecosystem consists of V2G, Renewable Power system, storage devices. All these sub-systems need to be tested separately as well as at complete system level. 

Vehicle-to-Grid Testing: 

To support Vehicle-to-Grid integration, EV and EV chargers (also called as Power conversion equipment) need to be smart and manage the charging & discharging in various grid scenarios. The performance testing requires a real bidirectional Power source which can source & sink power in both directions, and simulate various grid conditions. International standards are imposing strict and complicated test procedures which requires a flexible tool to generate all kinds of grid scenarios. Being a grid interactive load/source, these are required to be tested according to various standards such as IEEE 1547 / UL 1741 / UL 458 / IEC 61000-3-15 / IEC 62116 etc., 

Ametek MX/RS series Regenerative 3-Phase Grid Simulator

AMETEK California Instrument’s programmable regenerative grid simulators (MX & RS series) are ideally suited for testing Vehicle-to-Grid requirements. 

Compliance Test: 

• MX/RS can be programmed to emulate most types of grid power anomalies, including voltage dips, sags, swells, harmonics (even, odd, inter), interruptions, waveform phase shifts, waveform distortions, etc. 
• It can support standard Grid test for standards IEC61000-4-11, and IEC61000-4-13. 

Emulate Grid condition and Test Scenarios: 

• The support for arbitrary waveform, makes it flexible for emulating various raw grid power waveforms, which are far from ideal sine wave. 
• MX/RS can support generating & measuring voltage and current harmonics up to 50^th order, which supports most stringent test requirements. 

• MX/RS series offers Regenerative mode (bidirectional Power mode) which automatic crossover between Source and Sink power in AC mode. It can Regenerate up to 100% of the rated output power back to the utility grid during sink mode operation with conversion efficiency of >85%. 

Safety first: Anti-Islanding Test

• “Anti-islanding” is the ability of a generator to avoid supplying power to the grid if a circuit is opened. It is a necessary feature of distributed generation capacity for two reasons. Without it, excessive current could be drawn from the device, potentially damaging power electronics. More importantly, line workers may assume that circuits on the load side of an open line or open switch will not be energized – if there is an active “island” of energized lines, this poses a hazard to line workers. Also if the grid reconnects with inverter out of synchronization, again there is a chance for damage to customer/utility equipment. As per standard IS 16169/IEC 62116, Power conversion equipment (PCE) shall cease the energy output within 2 seconds after grid disconnection (grid shutdown/ offline). This function has to be equipped with grid tied Vehicle. Ametek MX/RS series Grid simulator offers Test procedure to test Anti-Islanding condition. 

Hardware In Loop Test: 

• With its capability to directly work with DC voltage control inputs, the grid simulators can be used as Class-A amplifiers in HIL (Hardware-In-Loop) applications. 

One stop solution for Power testing:

• AMETEK Programmable Power boasts one of the industries’ broadest portfolios of programmable power products under the well-known and respected Sorensen, Elgar, and California Instruments brands. AMETEK Programmable Power’s products serve a wide range of stimulus for Renewable Energy, Electric Vehicle, Grid and Battery testing. Ametek Solar Simulator, Grid Simulator (MX/RS), Wide range of Programmable AC and DC sources offers most comprehensive solution for EV and V2G Testing. 

Summary: 

As Electric Vehicle are on the rise, it requires infrastructure enhancement to meet growing demand. Electric vehicles are capable of providing ancillary services and storage of Energy to meet peak load power requirements. Additionally, V2G can provide distribution system support when there is a concentration of parked V2G cars, along overload elements in the distribution system. As the power electronics is growing with EV and V2G, the test requirements are also growing exponentially. Ametek offers broad range of Programmable Power source as well as custom solutions. AMETEK Programmable Power Solutions are especially skilled at providing application specific solutions like Solar Array Simulation, PV emulation for inverter verification, Battery string simulator, Power compliance test. 

Authors:

Bachelor Degree in Electronics Engineering with 20+ years of experience in Test and Measurement, Specialization in Automotive validation for High Speed Network standards and power design.

Bachelor Degree in Electrical Engineering with 18+ years of experience in Application consultants for Automotive Power, Solar, Power Design and Testing, Business development for VTI Data Acquisition system and system software.

Published in Telematics Wire