Modeling and control of a cascaded multilevel converter‐based electronic power transformer

Abstract

Control strategy of a cascaded multilevel converter based electrical power transformer (EPT) in a distribution system with capabilities of low voltage ride-through and unbalanced load current management is investigated in this study. The mathematical model and decoupled control schemes of the system, including a high-voltage side control scheme, an isolation-stage control scheme, and a low-voltage side control scheme, are presented in detail. A dual current control scheme is introduced to control both positive and negative sequence currents for enhancing the low voltage ride-through capability of the high-voltage side cascaded H-bridge converter. Positive, negative, and zero-sequence voltages are controlled for the low voltage side three-phase four-wire converter in the decoupled control scheme, respectively, for unbalanced load current management. A proportional resonant controller (PRC) is utilized to control the zero-sequence voltage, while the root locus method is applied in the PRC design. Three-dimensional space vector pulse width modulation (PWM) switching strategy is then used for the low voltage side converter. Simulation studies were conducted with MATLAB/Simulink to validate the coordinated control strategy.

Power Electronic Transformer Device Model Based on DSP Protection

“…In the case of failure, the failure indicator of the cabinet door will always be on, and the display screen of the monitoring and protection cabinet and the upper computer will show that the system is in a failure state. When the reset button on the cabinet door is pressed after troubleshooting, the system will clear the registers such as the current fault marker, soft start marker, soft start delay counter, button marker and various fault counters and enter the standby state, waiting for the soft start command or parameter modification command [12].…”

Multi‐function combined operation and control strategy of electronic power transformer for power quality improvement

“…Therefore, the current state feedback decoupling and the input voltage feed forward are applied. Then (4) can be simplified as (9):…”

“…2 . The isolation stage : As previously described (Section 2.2) dual‐active bridge (DAB) is chosen for the isolation stage of the EPT shown in Fig. .…”

“…As a new type of flexible alternating current transmission system (FACTS) device, the electronic power transformer (EPT) , also called the solid‐state transformer (SST) , has more advantages compared to the traditional line‐frequency power transformer. Reference presented a next‐generation power distribution system architecture, called the FREEDM system, in which the SST acts as the key converter and interfaced to distributed renewable energy and distributed energy storage devices.…”

“…As a new type of flexible alternating current transmission system (FACTS) device, the electronic power transformer (EPT) [6][7][8][9], also called the solid-state transformer (SST) [10,11], has more advantages compared to the traditional line-frequency power transformer. Reference [12] presented a next-generation power a Correspondence to: Dan Wang.…”