# A Comprehensive Review of Developments in Electric Vehicles Fast Charging Technology
## 6 Control Strategies for EV Systems  
This section focuses on the control technology employed in DC-DC converters for EV fast charging. It covers control objectives, methods, and challenges associated with different converters. Various control techniques such as voltage mode, current mode, peak current, and average current control are examined, applicable to isolated and non-isolated converter systems. Table 6 offers a comparison of control strategies for these converter types. Control objectives in DC-DC converter control technology refer to the desired performance criteria that need to be achieved. These objectives typically include regulating the output voltage or current, achieving a fast response to load changes, maintaining stability, minimising ripple and noise, and maximising efficiency. Ongoing research and development efforts continue to refine these control technologies and explore new approaches to optimize charging performance, integrate them with smart grids, and enhance user experience. As the EV market expands, advancements in control technologies will play a vital role in shaping the future of fast and reliable charging infrastructure. Control methods in DC-DC converter control technology encompass the techniques and algorithms to achieve the desired control objectives. Some commonly employed methods include voltage mode control, current mode control, peak current control, and average current control. Each method has advantages and trade-offs regarding response speed, stability, and complexity. However, despite the availability of various control methods, DC-DC converters can encounter common problems that need to be addressed. These issues include  
Figure 7: Block diagram of DC Fast Charging Power Conversion Stage with: (a) LFTS Configuration. (b) SST-Based HFT Configuration. output voltage or current overshoot or undershoot, instability leading to oscillations or ringing, poor transient response, excessive ripple or noise, and cross-regulation problems in multiple-output converters. Effective control strategies should consider these challenges and aim to mitigate them. In voltage mode control for non-isolated and isolated DC/DC converters, charging techniques include pulse width modulation, peak and average current mode control, feedforward control, proportional-integral-derivative control, and predictive control. Techniques for non-isolated DC/DC converters under current mode control involve current sensing, cycle-by-cycle current limiting, and slope compensation. The peak current control technique in non-isolated converters employs peak current sensing and limiting, while average current control utilizes the average current sensing and limiting control techniques. Isolated DC/DC converters under voltage mode control use the same methods as non-isolated converters. In contrast, the current mode control technique utilizes current sensing, cycle-by-cycle current limiting, and slope compensation. Peak current control in isolated converters employs peak current sensing and limiting, while average current control uses average current sensing and limiting. These strategies and techniques are tailored to ensure effective voltage and current regulation in various DC/DC converter configurations. When choosing a control method, considering the impact of charging methods on battery durability, it is crucial to prioritize factors like battery health, longevity, and service life. To achieve this, it is necessary to assess how each method affects battery degradation and lifespan [156]. This evaluation should consider aspects such as charging rate (high currents degrade batteries faster), temperature management (cooler temperatures promote battery health), and general stress on the battery cells during charging [157]. Prioritizing these factors in the charging process can extend the lifespan of electric vehicle batteries and maximize their long-term performance. For optimal charging profiles, always consult the battery manufacturer's specifications.