CHARGE AHEAD: DESIGNING V2G SYSTEMS TO TRANSFORM EVS INTO GRID-ENHANCING POWERHOUSES
Developing Bidirectional Power Converters
Using an EV battery as a storage unit requires a bidirectional power converter that permits electricity flow and a digital control system that manages device switching to regulate voltage and current. These components enable the converter to achieve the required power flow between the battery and the power system.
EV sales and renewable energy production are on the rise globally. The US alone added 5.8 million light-duty electric vehicles( EVs) to its roads as of 2023, which has led the US Department of Energy to predict that electricity demand for EV charging could increase overall US electricity consumption by 20-50 % by 2050. If the current worldwide trend continues, engineers’ primary challenge will be managing the complex energy flow caused by supply and demand variability and grid overloading due to EVs connecting to the grid at variable intervals. One solution is to use EV batteries as energy storage assets to improve grid response, referred to as vehicle-to-grid( V2G). V2G supports the secure operation of distributed energy resources and helps manage complex energy flow, improve efficiency, and minimize energy loss.
Managing these dynamic power systems is a complex endeavor and requires two key capabilities: 1) enable two-way power flow between EVs and the grid and 2) predict the overall electrical load and the time ranges when EVs are expected to connect to the grid. To do that, engineers must rely on bidirectional power converters and simulation-based technology development.
In bidirectional power converter development, design engineers use behavioral models on a desktop computer to simulate the battery, power converter and its control algorithms, and grid connection. The value of simulation models lies in their ability to accurately represent the technology’ s behavior in development and address engineering challenges at each stage of the development process. For example, converter average value models can be implemented in feedback control design. These models accurately capture the voltage and current response within the control system’ s bandwidth while omitting the effect of power electronic switching. This simplifies the model because it does not need to simulate over higher frequencies, allowing engineers to perform control design iterations rapidly. Desktop simulation can also be used to evaluate the response of grid-connected charging stations, evaluate compliance against grid codes, and develop predictive maintenance algorithms that improve system up-time.
Control design for bidirectional power converters includes tuning control parameters for achieving stable and rapid response and providing support for 4-quadrant control, enabling the system to control both the direction of current flow and the voltage polarity. Once the feedback control is designed, engineers can evaluate it on a more detailed model that includes power electronic switching. As part of the feedback control system verification, this evaluation assesses the impact of high-frequency harmonics.
Desktop simulation can also be used to evaluate system response under conditions that are difficult or dangerous to test on physical hardware. For example, fault simulations allow engineers to develop
16 AUTOMATION, CONTROL & ENGINEERING