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The Ultracapacitor-Based Controlled Electric Drives With Braking and Ride-Through Capability: Overview and Analysis

Two issues are still a great challenge in design and application of advanced controlled electric drives: 1) recovery of the braking energy and 2) ride-through capability of the drive system. Apart from ordinary solutions, such as back-to-back and matrix converters, the ordinary drive converter equipped with an energy storage element is used in specific applications such as traction and lift drives. This approach came into focus recently with rapid development of electrochemical double-layer capacitors, so-called ultracapacitors. The ultracapacitor is an electrochemical capacitor having energy density much greater than that of standard electrolytic capacitors. Additionally, the ultracapacitor power density is much higher than that of the existing electrochemical batteries. In this paper, a regenerative controlled electric drive having extended ride-through capability is discussed. The basic principle has been extensively analyzed, including a detailed analysis of all operational modes. A bidirectional three-level dc-dc converter has been considered as the interface power converter. The ultracapacitor design guideline is given. A control algorithm that allows control of the dc bus voltage and the ultracapacitor voltage and current has been presented and briefly analyzed. The regenerative controlled drive system has been tested, and the results are presented and discussed.