An electronic system includes a plurality of switching elements (T) and a plurality of energy storage elements (L; C). The energy storage elements (L; C) are connected to one another by the switching elements (T). The energy storage elements (L; C) can be selectively switched to a first, a second or a third state by switching the switching elements (T). In the first state, the energy storage elements (L; C) are connected in series with one another. In the second state, the energy storage elements (L; C) are connected in parallel with one another. In the third state, the energy storage elements (L; C) are bypassed, wherein two of the energy storage elements (L; C) are each connected by no more than three of the switching elements (T).

A loss optimization control method for modular multilevel converters (MMCs) under fault-tolerant control is disclosed. The method includes the following steps: when a fault of a SM in a MMC occurs, bypassing the faulty SM to achieve fault-tolerant control; suppressing the fundamental circulating current using a fundamental circulating current controller; respectively calculating the loss of each SM in faulty arms and healthy arms by using loss expressions of different switching tubes in SMs of the MMC; aiming at the loss imbalance between the arms of the MMC, taking the loss of a healthy SM as the reference, adjusting the period of capacitor voltage sorting control in the faulty SMs, achieving the loss control over the working SMs in the faulty SMs, and finally achieving the loss balance of each SM in the faulty arms and the healthy arms. Compared with the conventional methods, the proposed method is easier to implement and does not increase the construction cost of MMCs.

A cascaded multilevel converter is disclosed. The converter comprises a plurality of modules coupled to form a branch, each of the modules comprising a switching circuit and a DC link for supplying DC voltage to the switching circuit. The converter further comprises a controller for controlling the switching circuit of each module to generate an AC voltage in the branch, wherein the controller is configured to: determine for each module a voltage across a capacitor of the DC link of the module, determine for each module a reference power value for charging the capacitor of the DC link of the module to a reference voltage value for the module, determine, from the reference power values of the modules, a common reference AC current value for AC current in the branch, determine, from the common reference AC current value, a common reference AC voltage value for AC voltage in the branch.

A current path to a gate is cut off by a normally-off first switch element until start-up of a gate drive voltage generator is sensed. Furthermore, a semiconductor switching element is maintained in an off state as a normally-on second switch element short-circuits the gate to a source. As start-up of the gate drive voltage generator is sensed, the second switch element is turned off and the first switch element is turned on. As the gate is thus driven by an output from a signal amplifier in accordance with a control signal, the semiconductor switching element is turned on and off in accordance with the control signal.

A system may be provided that may include a first battery, and an inverter coupled to the battery. The system may also include a first active filter including a first switch element, second switch element, third switch element, and fourth switch element. Each switch element may be coupled to the first battery or the inverter. The first, second, third, and fourth switch elements may be configured to increase or decrease an applied voltage or current of the first battery.

An MMC-type power conversion device includes a failure detection unit that detects presence or absence of failure of each of n upper arm current detectors and n lower arm current detectors. The failure detection unit makes a first determination based on comparison between a sum of detection values of n upper arm current detectors and the sum of detection values of n lower arm current detectors, a second determination based on comparison between a current command value and the sum of detection values of n upper arm current detectors, a third determination based on comparison between a current command value and the sum of detection values of n lower arm current detectors, and a fourth determination of comparing, for each phase, the sum of detection values of the current detectors of an upper arm and a lower arm of the same phase.

A power converter for transforming electrical power between direct current power and alternating current power is provided, as well as related methods and systems. The power converter comprises: a half-bridge inverter, a switching cell, and a connection branch connecting the half-bridge inverter to the switching cell. The half-bridge inverter comprises: first and second switches connected in parallel, and a first capacitor connected between the first and second switches. The switching cell comprises: a first pair of switches forming a first branch, a second pair of switches and a second capacitor forming a second branch; and a third capacitor connected between the first and second branches. The connection branch is coupled to the half-bridge inverter at a first point intermediate the first capacitor and the second switch, and coupled to the switching cell at a second point intermediate the first branch and the second capacitor.

A dual multi-level inverter topology with reduced switch count and small DC-link capacitor is provided. The inverter topology provides multi-level inverter operation without requiring a neutral point connection that is commonly present in a stacked capacitor topology (for example, a topology including two capacitors).

Aspects are described for hybrid modular multilevel converters that include half-bridge submodules. In some embodiments, a hybrid modular multilevel converter can include a direct current (DC) bus and an alternating current (AC) node. A first arm of the hybrid modular multilevel converter includes a first submodule chain link and a first arm inductor and a second arm includes a second submodule chain link and a second arm inductor. A capacitor connects between a first side of the first arm and a first side of the second arm.

A grid-forming wind turbine control method for a diode rectifier unit-based offshore wind power transmission system. A control system for controlling a grid-side converter has a three-layered structure, where a first layer is a combination of an active power controller and a reactive power controller; a second layer is a voltage controller; and a third layer is a current controller. The actual reactive power is represented by a per-unit value of a capacity of a corresponding wind turbine unit. The wind turbine units have the same reactive-power reference value, which is constant and does not change with time. The reactive power controllers of all wind turbine units have the same structure and parameters.