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A modular multilevel converter (MMC) with traditional cascaded PI control structure suffers from poor steady state and dynamic performance. This is due to the limited harmonic rejection capability of PI controller thus failing to alleviate even order harmonics in circulating current and due to the slower outer average voltage control loop resulting in significant deviation in submodule capacitor voltages...
This paper presents a steady-state analysis of the modular multilevel converter (MMC) for the second order voltage and current ripple prediction under unbalanced conditions, taking the impact of negative sequence current control into account. Using the circular relationship among current and voltage quantities, the magnitudes and initial phase angles of different circulating current components can...
In this paper, a simple single-phase grid-connected photovoltaic (PV) inverter topology consisting of a three-level inverter, an LCL filter, and a new current feedback method for active damping is considered. A dynamically rapid method is used for tracking the maximum power point (MPP) of photovoltaic arrays, known as ripple correlation control. The algorithm uses the current and voltage low-frequency...
This paper analyzes the active power in modular multilevel converters (MMCs), and presents a novel comprehensive control scheme of low frequency operation for the arm capacitor voltages and high frequency circulating current. The inner loop of this scheme employs the arm current direct control which can control the ac side currents, dc-link current and circulating currents simultaneously; an improved...
In a modular multilevel converter (MMC), the circulating current control is usually adopted. It can minimize the circulating current in order to reduce the converter power loss, and also provide an active damping which is beneficial for the converter control stability. The circulating current control is normally implemented by adding a compensating component into the modulation signal. Consequently,...
Input -series connected DC/DC converters based on one transformer is proposed for high voltage input and high power applications. Phase-shifted full-bridge (PS-FB) control strategy with common duty cycle control is adopted for each converter. Operation principles of the proposed converter are analyzed. Although primary currents vary for magnetic coupling and turns mismatch, combined peak current control...
The grid-connected inverter works as a controlled current source in grid-connected mode, while operates as a controlled voltage source in standalone mode. So in case of utility faults or intentional islanding, the inverter has to change its control strategy from current control to voltage control. This paper first proposed a multi-loop voltage controller with capacitor differential voltage feedback...
This work deals with the design and analysis of a controller for a shunt active power filter. The design is based on combined feedforward and feedback actions, the last using repetitive control, and aims at the obtention of a good closed-loop performance in spite of the possible frequency variations that may occur in the electrical network. As these changes affect the performance of the controller,...
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