A bridge circuit with series-connected switches and associated control method. The bridge circuit has a first bridge arm and a second bridge arm coupled to a common node, the first bridge arm has a plurality of series-connected first main switches, each first main switch is coupled in parallel with an auxiliary module, each first auxiliary module has a clamping capacitor and an auxiliary switch, the first bridge arm receives a first main switch signal to control the plurality of series-connected first main switches, the second bridge arm receives a second main switch signal, the control method is sensing voltages of the clamping capacitors in the first bridge arm, correspondingly generating voltage sensing signals, and turning on at least one auxiliary switch for a predetermined time during a dead time according to a sorting result of the voltage sensing signals.

A method of balancing voltage distribution over a plurality of switches connected in series with each other in a high voltage (HV) switch is provided. A snubber arrangement is associated with each switch of the plurality of switches. The method includes, for a first snubber arrangement associated with a first switch of the plurality of switches, determining a first voltage across a first snubber energy storage component of the first snubber arrangement associated with the first switch. The method further includes, for a second snubber arrangement associated with a second switch of the plurality of switches, determining a second voltage across a second snubber energy storage component of the second snubber arrangement associated with the second switch. The method further includes comparing the first voltage and the second voltage and, based on the comparison, adjusting a first drive signal of at least the first switch based on the first voltage.

A power conversion device includes a power converter including a plurality of arms each having a plurality of converter cells connected to each other in cascade. Each converter cell includes a capacitor electrically connected to input/output terminals through a plurality of switching elements. A control device performs AC current control in accordance with a deviation between a detected AC current and an AC current command value and individual voltage control in accordance with a deviation between a voltage of each individual capacitor and an individual voltage command value. The control device calculates an evaluation value indicating the degree of variations in voltage of the individual capacitors. When the evaluation value is greater than a threshold value, the control device changes control of the power converter such that arm current flowing through each of the arms increases while the AC current control and the individual voltage control are being performed.

The present application provides a conversion system and a control method, including N power converters and N controllers, where each power converter includes a first side and a second side, the first sides of the N power converters are electrically coupled in series, and currents flowing through the first sides of the N power converters are the same, the N controllers correspond to the N power converters one to one. Each controller contains a common-mode voltage loop and a current loop. The common-mode voltage loop is configured to receive a voltage reference signal and a voltage feedback signal, and output a given signal. The current loop is configured to receive the given signal, a current reference signal, and a first side current of a corresponding power converter, and output a common-mode control signal to modulate a first side voltage of the corresponding power converter.

A submodule distributed control method, device and system are provided. Submodules of each bridge arm are grouped. Each group corresponds to one valve based controller. An upper-level control device calculates a weight of each group according to a bridge arm current, an average voltage of normal submodules in each group, and the number of the normal submodules in each group; calculates, according to the number of submodules to be input in a corresponding bridge arm, the number of submodules being input in each group and delivers the number to the valve based controller. The valve based controller operates according to a voltage balancing policy and a gating method that are provided in the prior art.

A converter comprises a first switch, a second switch, a first blocking device and a second blocking device connected in series between two terminals of an output capacitor, an inductor coupled between a dc input source and a common node of the second switch and the first blocking device and a capacitor coupled between a common node of the first switch and the second switch, and a common node of the first blocking device and the second blocking device, wherein a voltage across the capacitor is configured to be adjustable through adjusting duty cycles of the first switch and the second switch.

A controller switches between modes each having a different connection state of a DC power supply and the capacitor with respect to first and second output points by controlling switches. A generation unit generates a reference wave including at least one carrier wave. The modes are classified into a sustaining mode in which no current is caused to flow to the capacitor, a charging mode in which a current is caused to flow to the capacitor, and a discharging mode in which a current in a direction opposite to that in the charging mode is caused to flow to the capacitor. The controller switches between the sustaining mode and a charging or discharging mode according to the comparison result between a signal wave and the reference wave.

A circuit includes first and second transistors, a capacitor, and a controller. The controller is coupled to the control inputs of the first and second transistors. The controller configured to, during a first mode and in accordance with a first time-varying duty cycle, turn on and off the first transistor while turning on the second transistor when the first transistor is off. The controller is also configured to, during a second mode following the first mode, and in accordance with a second time-varying duty cycle, turn on and off the first transistor while turning on the second transistor when the first transistor is off.

Current control section 2 performs PI control based on deviation between d-axis command current Id_cmd and d-axis detected current Id_det and deviation between q-axis command current Iq_cmd and q-axis detected current Iq_det. Neutral point potential control section 4 calculates corrected command voltage V_cmd′ by addition of neutral point control compensation quantity V_cmp to three-phase command voltage V_cmd. Limiter LMT3 outputs limiter processed command voltage V_cmd″ by liming the output of corrected command voltage V_cmd′. Three-phase to two-phase converter 5 outputs feedback quantities Vd_back, Vq_back by three-phase to two-phase conversion of the limiter processed command voltage V_cmd″. Current control section 2 performs integral control in accordance with quantities resulting from addition of the feedback quantities Vd_back, Vq_back to the deviations. Accordingly, the three-phase neutral point clamed power conversion apparatus performing the PWM control suppresses interference between the current control and the neutral point potential control.

A method for controlling a three-level back-to-back voltage source power conversion assembly includes receiving an indication of a DC or AC unbalance occurring in voltage of a DC link. The power conversion assembly has a first power converter coupled to a second power converter via the DC link. In response to receiving the indication, the method includes activating a balancing algorithm that includes determining a deviation of a midpoint voltage of the DC link as a function of a total voltage of the DC link, calculating a voltage compensation needed for pulse-width modulation signals of the power conversion assembly based on the deviation, and coordinating common mode voltage injection from each of the power converters independently at a neutral point of the power conversion assembly based on the voltage compensation, thereby minimizing the at least one of the DC unbalance or the AC unbalance at any given operating condition.