33results about How to "Capacitor voltage equalization" patented technology

The invention discloses an optimal pressure equalizing control method of a modular multilevel converter type direct current transmission system. By setting an upper limit and a lower limit on voltage, the pressure equalizing control is mainly carried out on submodules with out-of-limit capacitor voltage, and capacitor voltage sequencing for submodules with no out-of-limit capacitor voltage is processed by combing the charging / discharging conditions of bridge arm current so as to increase the probability of maintaining an original switching state for the submodules with no out-of-limit capacitor voltage when the next action is in triggering control and lower the switching frequency of devices. The introduction of the pressure equalizing control can not lower the working frequency of triggering control and the tracking speed of a converter by using submodule capacitor voltage sequencing and triggering control to work at different frequencies. The optimal pressure equalizing control method of the invention can greatly lower the switching frequency of the devices on the premise of having no obvious increment on submodule capacitor voltage fluctuation.

The invention provides a capacitor voltage balance control method of a cascade reactive power compensation device, belonging to the technical field of reactive power compensation control, and aiming at solving the problem that the existing method for balancing the capacitor voltage of a power unit is complex in process and unstable in control status. The method comprises the following steps of: firstly, acquiring the alternating current-side voltage u and the alternating current-side voltage i of each power unit in the cascade reactive power compensation device to obtain the instantaneous power polarity of each power unit; sampling the instantaneous capacitor voltage of a power unit by the frequency which is same as that of the carrier of the reactive power compensation device to obtain a voltage adjusting value of the power unit to be taken as a modification value of the carrier; confirming the modification value of the carrier and the overlapping mode of the carrier, and obtaining the adjusted carrier; and comparing the adjusted carrier with the sinusoidal modulation wave to obtain a modulating signal of the power unit, and controlling the power unit of the reactive power compensation device by the modulating signal to realize the capacitor voltage balance control of the compensation device. The capacitor voltage balance control method is used for balancing the capacitor voltage of the reactive compensation device.

The invention discloses a multi-mode smooth control method and system for a cascaded three-level BUCK-BOOST converter, which is applied to a cascaded three-level BUCK-BOOST converter. For the inherent dead zone, capacitor voltage imbalance and mode oscillation problems of the cascaded three-level BUCK-BOOST converter, using the multi-mode smooth control method proposed by the present invention to control the converter can solve the above problems, A smooth transition between boost and buck is achieved.

The invention relates to a capacitor self-equalizing three-phase multi-level converter circuit with a DC bus, which belongs to the technical field of electric power equipment. The multilevel converter circuit is composed of a three-phase valve body with a common DC bus. Each phase valve body is divided into two parts, left and right, and each part contains N (N is an even number greater than zero) half-bridge power units connected in series. Each half-bridge power unit is composed of a diode, a capacitor and two power switches in series; the left and right sides of each phase valve body are connected in a quasi-symmetrical form, using the diode of the power unit, six connecting inductors and a middle diode A valve body topology with capacitive self-balancing function is formed, and the three-phase valve body is connected in parallel to the DC bus, so that the circuit can also realize functions such as negative sequence component processing and four-quadrant operation on the basis of capacitive self-balancing function. The invention has simple circuit topology and simple control, and can be widely used in medium and high-voltage large-capacity AC / DC conversion occasions.

The invention discloses a parallel active filter based on a modularization multi-level converter and a control method of the parallel active filter and belongs to the technical field of power harmonic suppression in a medium-high voltage high-power occasion. The problem that an existing parallel active filter cannot carry out harmonic combination compensation effectively, so that power distribution network electric energy quality is poor is solved. The filter comprises the modularization multi-level converter, a current transformation unit, a harmonic current detecting unit, a current controller, a capacitor C and a power grid electric reactor LS. The modularization multi-level converter is of a half-bridge-type topological structure, and an upper bridge arm and a lower bridge arm of the modularization multi-level converter respectively comprise n submodules SMn. According to the control method, a carrier phase-shifting modulation method is used, so that under the same switch frequency, equivalent switch frequency is high, switching loss is reduced, meanwhile, a capacitive coupling voltage sharing and ring current suppression strategy is used, and capacitor voltages and direct current bus voltages of the submodules are kept stable. The parallel active filter is used for harmonic suppression of a power grid.

The invention discloses a hybrid ride-through method for DC short-circuit faults in an MMC-MTDC system, and relates to the technical field of power supply systems, including proposing a non-blocking fault ride-through strategy based on negative DC voltage control. On this basis, a hybrid crossing method is proposed, which does not block the converter station when no overcurrent occurs, actively blocks the converter station when the bridge arm overcurrent occurs, and removes the blocked converter station. , so that the unblocked converter station can continue to operate, realize the DC fault ride-through more safely and quickly, minimize the impact of the DC fault disturbance on the system, and help improve the anti-DC fault disturbance capability of the multi-terminal DC power grid.

The invention discloses a layered control method for a cascaded rectifier, which comprises the following steps: generating an initial parameter group for starting the cascaded rectifier system in an upper controller; The parameter set is transmitted to each bottom controller for controlling each sub-module in the cascaded rectifier system via a communication link; in each bottom controller: a PWM initial modulation signal is generated based on the received initial parameter set and used as Control instructions are sent to each sub-module in real time to start the cascaded rectifier system to work, and at the same time collect the voltage and current of the front-end input and rear-end output of each sub-module after being started; The calculation is controlled to obtain a PWM real-time modulation signal, and the PWM real-time modulation signal is used to control the voltage input of the correspondingly connected sub-module.

The present invention proposes a hybrid dual sub-module MMC voltage equalization control method and device. For any bridge arm, according to the current direction of the bridge arm, the positive or negative of the sum of the voltage differences in the modules of the entire bridge arm and the positive or negative of the number of input sub-modules , sorting the comprehensive voltage index of each sub-module, and determining the corresponding output state of each sub-module; the comprehensive voltage index is related to the capacitor voltage in the module and the capacitor voltage difference in the module. The present invention is based on the comprehensive voltage index-based sorting voltage equalization control between modules, which realizes the effect of capacitor voltage balance inside the module and capacitor voltage balance between modules, and can be used in various working conditions such as start-up, normal operation, and fault ride-through of the mixed twin-module MMC system Both can achieve a good pressure equalization effect.

The invention relates to the field of DC transformers, in particular to a modular high-voltage transmission ratio DC transformer topology structure and a control method. The topology structure consists of a high-voltage filter capacitor C HV , high voltage filter inductor L HV , high-voltage side thyristor, N power module groups, low-voltage filter inductor L LV with low voltage filter capacitor C LV composition. Each power module group includes an input port and an output port. After the input of N power module groups is connected in series, the high-voltage side thyristor, high-voltage filter inductor, high-voltage filter capacitor and low-voltage filter capacitor are connected to form a high-voltage DC port; N power module groups output After parallel connection, connect the low-voltage filter inductor and the low-voltage filter capacitor to form a low-voltage DC port. Compared with the traditional DC transformer, the present invention has the advantages of fewer modules, low cost and small volume. The DC transformer topology in the present invention only uses a small number of half bridges, which can realize DC voltage conversion with high transmission ratio, thereby reducing DC voltage. Transformer cost, improve power density.

The invention relates to a valve level control method for a flexible DC power transmission system and belongs to the technical field of power electronics and custom power. The method comprises the steps that correlation operation is performed on a three-phase modulation signal received by valve level equipment to obtain the number of sub-modules which should be input by upper and lower bridge arms; afterwards, capacitor voltage values of the collected sub-modules are sequenced from small to large; finally, the direction of bridge arm current is judged, the sub-modules with lower capacitor voltages are input if the direction of the bridge arm current is the same as that of charging current, and the sub-modules with higher capacitor voltages are input if the direction of the bridge arm current is the same as that of discharging current. According to the valve level control method, the balance of the capacitor voltages can be maintained while the time consumed by a sorting algorithm is shortened remarkably, and the capacitor voltages of all the bridge arm sub-modules can be effectively maintained to be on the same level on the basis of guaranteeing that the valve level control cycle reaches the microsecond level below; in addition, the harmonic content of AC output voltage is low, reduction of system loss is facilitated, and the construction cost is also lowered.

The invention discloses a multi-power-supply gridconnected system control method based on a modularized multilevel convertor. The multi-power-supply gridconnected system control method comprises the following steps: the power control part of the modularized multilevel convertor generates a sinusoidal modulation wave; the sinusoidal modulated wave is sequentially subject to direct current supply control, an interphase circumfluence control and a gridconnected current direct current component inhibit control to superpose corresponding regulation value, and is finally subject to carrier wave dephasing SPWM modulation to generate a switch driving signal. The multi-power-supply gridconnected system control method can flexibly control the interphase circumfluence according to the operation state of the multi-power-supply gridconnected system.