A method controls switching states of a multi-level converter with multiple modules. Each module has: terminals on a first and second side; controllable switches; and an energy store in series with a first switch in a first connection between the terminals. A second switch is arranged in a connection between the terminals. The control of the switching states is divided into a real-time and offline part. In the real-time part, for each time step: a voltage level is allocated to a voltage requirement; a total switching state is determined in a first switching table for the voltage level; and the total switching state is passed on as a control signal to the switches. In the offline part: a second switching table is calculated, resulting in accordance with a minimization of a cost function.

A higher-level control unit 5 generates a level command L* on the basis of a command value cmd. A switching load distribution control unit 6 stores the output period information of each cell and designates a gate signal so that: in case of a pattern by which a cell is changed from ±1 level to 0 level, the cell having the longest ±1 level period information is set to 0 level; and in case of a pattern by which a cell is changed from 0 level to ±1 level, the cell having the longest 0 level output period is set to ±1 level. This distributes the switching load of each cell in the serial multiplex inverter control device.

Systems and methods for power conversion are described. For example, a system may include a transformer including a plurality of secondary windings; a first set of switches connecting respective taps of the plurality of secondary windings to a first terminal; a second set of switches connecting the respective taps of the plurality of secondary windings to a second terminal; and an electrical load connected between the first terminal and the second terminal.

A compensator circuit for a PWM active rectifier includes a look up table containing compensating voltage values for given values of input phase current and input voltage frequency, and a low pass filter arranged to filter the input phase current to the rectifier based on a filter bandwidth determined according to the input voltage frequency. The compensator circuit arranged to receive measured input current and voltage frequency values and to output corresponding compensation voltage values from the look up table, the compensation voltages to be provided, in use, to the rectifier to adjust the switching pattern of the rectifier.

A multilevel self-balance control circuit can include: a voltage divider unit configured to receive and divide an input voltage; a voltage-controlled charge source load coupled to an output terminal of the voltage divider unit, and being configured to adaptively adjust charge amount input to the voltage-controlled charge source load based on an output voltage of the voltage divider unit, such that a total amount of charges flowing through the voltage-controlled charge source load during a period of each working state of the voltage divider unit is positively correlated with the output voltage of the voltage divider unit, thereby forming a negative feedback loop to achieve voltage balancing of the voltage divider unit; and a control unit configured to generate control signals for the voltage divider unit and the voltage-controlled charge source load, thereby coordinately controlling the voltage divider unit and the voltage-controlled charge source load.

A DC/DC power converter comprises three or more capacitors connected in series between an output terminal and a ground terminal, the three or more capacitors being connected in series by means of two or more capacitor connection points, and an input voltage switching unit configured to connect an input terminal to one of a group of switching connection points, the group of switching connection points comprising the two or more capacitor connection points and the output terminal. With such a DC/DC power converter it is possible, for example, to convert a variable DC voltage at the input into a variable DC voltage at the output, wherein the voltage range of the output voltage is smaller than the voltage range of the input voltage.

An auxiliary power circuit of a conversion module is used to supply power to a control unit, and an input end of the conversion module includes an even number of energy storage units coupled in series. The auxiliary power circuit includes an even number of primary-side circuits and a secondary-side circuit. Each primary-side circuit includes a first switch unit, a second switch unit, and a resonance tank. The first switch unit is connected to the second switch unit in series, and is correspondingly connected to one of the energy storage units in parallel. The resonance tank is connected to the second switch unit in parallel. The secondary-side circuit is coupled to the resonance tanks of two of the primary-side circuits to acquire power and supply power to the control unit.

Circuits and methods that more effectively and efficiently solving the charge-balance problem for multi-level converter circuits by establishing a control method that selects an essentially optimal pattern or set of switch states that moves the fly capacitors towards a charge-balance state or maintains the current charge state every time a voltage level at an output node is selected regardless of what switch state or states were used in the past. Accordingly, multi-level converter circuit embodiments of the invention are free to select a different switch state or output voltage level every switching cycle without needing to keep track of any prior switch state or sequence of switch states. Additional benefits include improved transient performance made possible by the novel charge-balance method.

Circuits and methods that solve the light-load problem of a multi-level converter by generating a ripple signal in the control loop of the multi-level converter that causes a large output current ripple during light load conditions. This added current ripple does not change the average output current but does create a temporary positive and negative current that can be used to balance and charge/discharge the fly capacitors of the multi-level converter. An alternative approach is to add extra switching cycles for the fly capacitors when the output ripple current crosses zero.

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.