481 results about "Multilevel inverter" patented technology

The invention discloses an energy-saving type cascade multilevel photovoltaic grid-connected generating control system comprising an energy-saving cascade multilevel photovoltaic generating inverter, a controller and a power grid, wherein the multilevel inverter consists of 3n energy-saving type photovoltaic generating modules, wherein n modules are connected in series into one phase of a three-phase inverter; and the single-stage power of each module is converted to realize the buck-boost, the inverting and energy saving and adapt to the wide-range change of the battery voltage with high reliability. 3n photovoltaic cells and energy-saving cells are distributed on 3n modules; the generation of each module is independently controlled, thereby realizing the distributed maximum power track, collecting solar energy to the maximum extent, realizing high efficiency and avoiding the problems of power loss and hot spot caused by the local shade generated when the photovoltaic cells are connected in series; and the invention can flexibly control the stable power of a feeder grid of the multilevel inverter and achieve the functions of reactive power consumption, the power pitch peak control and the like, has the advantage of multilevel inversion and low output harmonic voltage and is suitable for high-voltage, high-power and transformer-free grid connection.

A fault handling system for short circuit recovery in three-phase multiple-level inverter bridges, used to drive inductive loads, which waits for either desaturation of switches or expiration of a delay period based upon an amount of time before saturated switches are damaged before commanding off switches that are saturated, and which artificially creates a dead-short across the three-phase output to force switches conducting a fault current to desaturate. By delaying the switching-off of the inverter bridge during a fault, waiting for desaturation to occur, the statistical likelihood of switch survival is improved.

A power generation system including a photovoltaic (PV) module to generate direct current (DC) power is provided. The system includes a controller to determine a maximum power point for the power generation system and a boost converter for receiving control signals from the controller to boost the power from the PV module to a threshold voltage required to inject sinusoidal currents into the grid. A DC to alternating current (AC) multilevel inverter is provided in the system to supply the power from the PV module to a power grid. The system also includes a bypass circuit to bypass the boost converter when an input voltage of the DC to AC multilevel inverter is higher than or equal to the threshold voltage.

The present invention relates to a battery energy storage topology structure without the transformer based on MMC modularized multi-level inverter: every phase is connected in series with several subunits which are composed of half-bridge power modules and battery energy storage modules, and get access to the electrical network through buffer inductance. The half-bridge power module is formed by the series connection of an even number of n power units, which is divided into two groups, the upper group and the lower group; the number of each group's power units is n/2; the number of output phase voltage level step is n/2 + 1; the number of line voltage level step is n + 1; the output terminal of every phase is the midpoint of two groups of units, and the output terminal is connected with each group of unit by coupling inductance or uncoupling inductance. The power unit is in a half-bridge structure. As the topology is in parallel connection with electrical network, the electric power pollution of electric network can be inhibited; and the topology can make up for the instability of photovoltaic or wind energy generation to provide uninterrupted, clean, stable and high-qualified sine wave voltage of no frequency discontinuity to the load of the electrical network.

The invention discloses a multilevel inverter fault diagnosis strategy based on a principal component analysis and multi-classification related vector machines (PCA-mRVM). The multilevel inverter fault diagnosis strategy includes: subjecting primary samples to dimensionality reduction through principal component analysis, and extracting multiple principal components with fault features so as to form training samples; subjecting the training samples to fault diagnosis through the multi-classification related vector machine, outputting probabilities of fault classifications, and taking the fault classifications with the maximum probabilities as diagnosis results. The multilevel inverter fault diagnosis strategy has the advantages in the fault diagnosis with larger sample space and more classifications, is high in model sparseness, low in computation complexity and the like; most importantly, the probabilities of classification members can be outputted through the mRVM, probability and statistic significance is achieved, and uncertain problems can be conveniently analyzed.

A multilevel inverter is provided. The multilevel inverter includes a plurality of bridges, each bridge configured to receive a respective portion of an input DC power and convert the respective portion to a respective converted AC power. The multilevel inverter also includes at least one bridge controller for operating at least one of the plurality of bridges in a square waveform mode. The multilevel inverter further includes a plurality of transformers, each transformer coupled to a respective bridge and configured to increase a voltage level of the respective portion of converted AC power. The plurality of transformers further includes secondary windings coupled in series with the other secondary windings to combine the respective increased voltage level portions of the converted AC power. The multilevel inverter also includes a grid converter configured to provide output power for a power grid.

A boost inverter includes a first capacitor for connection in parallel with a dc supply voltage; a second capacitor connected in series with the first capacitor; an energy transfer path including a transfer capacitor and switches connected to the transfer capacitor for cyclically transferring energy from the first capacitor to the transfer capacitor and then from the transfer capacitor to the second capacitor; a multilevel inverter circuit connected in parallel with the series combination of the first and second capacitors, the inverter having at least one phase output for connection to an electric motor; and a PWM controller that activates the energy transfer path when a desired peak-to-peak output voltage exceeds the dc supply voltage and deactivates the energy transfer means when the desired peak-to-peak output voltage is less than the dc supply voltage.

The invention provides a multi-level inverter and a power supply system, and relates to the electronic field. The multi-level inverter and the power supply system can simplify circuit structures. The multi-level inverter comprises two N-level inversion units, a direct-current power source module, a transformer and a filter. Pulse width modulation waves of the two N-level inversion units are staggered by 180-degree phase positions, and the N is an integer larger than or equal to three. The output end of the direct-current power source module is respectively connected with the input ends of the two N-level inversion units, the transformer comprises an original edge and an auxiliary edge, an inductor of the original edge and an inductor of the auxiliary edge are mutually coupled, one end of the inductor of the original edge and one end of the inductor of the auxiliary edge are connected with the output ends of the two N-level inversion units respectively, and therefore the two N-level inversion units are coupled in a phase reversal mode. The other end of the inductor of the original edge and the other end of the inductor of the auxiliary edge are mutually connected, W levels are output at the connecting positions of the inductors, and the W is equal to 2N-1. One end of the filter is connected with the connecting positions of the two coupled inductors, and the other end of the filter is connected with the ground. The multi-level inverter and the power supply system are used for converting the direct current into the alternating current.

Systems and methods for supplying power at a medium voltage from an uninterruptible power supply (UPS) to a load without using a transformer are disclosed. The UPS includes an energy storage device, a single stage DC-DC converter or a two-stage DC-DC converter, and a multi-level inverter, each of which are electrically coupled to a common negative bus. The DC-DC converter may include two stages in a unidirectional or bidirectional configuration. One stage of the DC-DC converter uses a flying capacitor topology. The voltages across the capacitors of the flying capacitor topology are balanced and switching losses are minimized by fixed duty cycle operation. The DC-DC converter generates a high DC voltage from a low or high voltage energy storage device such as batteries and/or ultra-capacitors. The multi-level, neutral point, diode-clamped inverter converts the high DC voltage into a medium AC voltage using a space vector pulse width modulation (SVPWM) technique. The UPS may also include a small filter to remove harmonics in the AC voltage output from the multi-level inverter.

The photovoltaic and wind-power uniform interconnected equipment with reactive compensation and harmonic wave processing comprises: at least a clean energy power, at least one power modualtor, a dc busbar loop, a three- or four-phase multilevel inverter, one three- or four-phase interconnected reactor, a three- of four-phase breaker, and a data collection and logic controller. This invention can interconnect both the photovoltaic power and wind-power source, and every power can realize the maximal power point track. This invention can compensate the harmaci wave in 0-30 times.

The invention discloses a system and a method for controlling neutral point voltage balance with a low frequency oscillation suppression function. The system comprises a multi-level inverter and a digital processing control module, wherein the digital processing control module comprises a sampling unit, a closed-loop control unit and a digital pulse width modulation (DPWM) unit; the output end of the DPWM unit is connected to each switching tube of the bridge arm of each phase of the multi-level inverter. The method comprises the following steps: in each switching period, the sampling unit acquires a direct-current bus voltage signal of the multi-level inverter, and a three-phase voltage signal and a three-phase current signal both output by the multi-level inverter, respectively; the acquired signals are processed by the closed-loop control unit to obtain three-phase modulating waves; the three-phase modulating waves are processed by the DPWM unit to obtain a pulse width modulation control signal which is used for controlling the working state of the switching tube of each phase of the multi-level inverter by virtue of a drive circuit. The system and the method are capable of suppressing the low frequency oscillation of the neutral point voltage of the direct-current bus of the multi-level inverter and realizing the neutral point voltage balance.

The invention discloses a method for controlling the power balance of the DC side of a cascaded multilevel inverter. The power control of the cascaded multilevel inverter is divided into two layers, an upper layer control and a lower layer control,wherein, the upper layer control realizes the total power control, and the lower layer control carries out the operation of active power redistribution on each full-bridge conversion unit by overlapping a pure active power vector which is parallel to the current direction on the basis of the upper layer control, thereby enabling the input power on the DC side of each full-bridge conversion unit of the cascaded multilevel inverter to tend to be balanced. The invention does not need to be provided with an extra power circuit, and can effectively realize the power balance of the DC side of the inverter, thereby reducing the cost fo the system and improving the reliability of the system.

The invention relates to an active power quality adjuster, consisting of a fundamental wave compensation part and a harmonic wave compensation part, and the two parts compensate fundamental current and harmonic current respectively. An H-bridge cascade multilevel inverter and a fundamental wave connection inductance are connected in series at the fundamental wave compensation part, so that reactive compensation and unbalanced load compensation can be dynamically carried out; the H-bridge cascade multilevel inverter and a unituning passive filter are connected in series to form the harmonic wave compensation part which is connected across the two ends of the fundamental wave connection inductance. Therefore, the power quality adjuster can lower switching frequency and loss of the H-bridge cascade multilevel inverter at the fundamental wave compensation part greatly on one hand, and only a fraction of fundamental current passes the harmonic wave compensation part and the whole part only undertakes fundamental voltage of the fundamental wave connection inductance without undertaking fundamental voltage on the other hand, thereby effectively reducing the capacity of the H-bridge inverter and the withstand voltage at the harmonic wave compensation part.

The invention discloses a pre-charging system and method for a modular multilevel inverter, the common DC bus of the modular multilevel inverter is connected with every phase bridge arm of the modular multilevel converter through a current-limiting resistance R1 and a pre-charging initial contactor KM2 in sequence, a pre-charging finishing contactor KM1 is connected with a current-limiting resistance R1 in parallel, and the purpose of pre-charging is achieved by controlling the switch tube of the contactor and the modular neutron multilevel inverter module; according to the method provided by the invention, during the process of pre-charging, the current direction and the sub-module capacitance voltage value of the bridge arm are beyond testing, the workload of the controller is decreased; as the sub-module capacitance voltage value can achieve the rated value in normal operation after pre-charging, the decreasing of the wave form in the initial time when the system operates normally is avoided; and full-automatic pre-charging can be realized by switching on and off the circuit by the contactor, and the safety factor of the system is improved.

The invention discloses a three-phase hybrid multilevel inverter circuit, which is formed by cascading a level circuit module and a bridge circuit module. The bridge circuit module is a three-phase bridge circuit module which consists of a direct current supply, a clamp diode and a capacitor; the level circuit module is an asymmetric four-level circuit module which consists of a direct current supply, a clamp diode and an asymmetric four-level converter; and the output of the three-phase hybrid multilevel inverter circuit equals to the superposition sum of the outputs of each cascaded unit. By adopting different modulation methods, a multi-level output can be realized and the number of the output levels can be changed by changing the voltage ratio of the input current. The input direct current supply can be acquired by the solar energy, wind energy, fuel cells, storage batteries or isolated transformer rectifier units. Forming a hybrid cascaded multilevel converter by cascading the symmetric multilevel converter and the three-phase bridge circuit, the three-phase hybrid multilevel inverter circuit has the advantages of improving the output power quality, reducing the output harmonic waves and enhancing the reliability of the system due to the ability for outputting a plurality of levels.

A multilevel inverter using a cascade configuration with a device for equally controlling a power factor for each unit cell includes: a master controller, a plurality of power cells connected in series for each of three AC (Alternating Current) phases, a phase shift transformer for supplying a power cell input voltage, a CAN (Controller Area Network) communication network to provide a communication path between the master controller and each power cell, and cell controllers to control output voltages and output frequencies of the respective power cells according to a voltage command and a frequency command from the master controller, each cell controller having a pulse width modulator to generate a pulse width modulation control signal of a variable voltage and a variable frequency to the connected corresponding power cell, wherein each cell controller is configured to calculate a phase difference value of the corresponding power cell according to a preset total number of connected power cells and the floor number (i.e., the serial connection sequence) of the corresponding power cell to thereafter phase-shift a chopping wave by the calculated phase difference value, thereby compensating for the phase differences between each power cell.

A two-level or multi-level inverter are supplied with a positive auxiliary voltage (Ug+) and a negative auxiliary voltage (Ug−). A bootstrap technique provides a first positive auxiliary voltage and a first negative auxiliary voltage from the supplied potentials. The bootstrap technique provides at least one additional negative auxiliary voltage to a switch driver of at least one semiconductor switch from the first negative auxiliary voltage. At the start up of an inverter, the inverter can perform a startup sequence to provide auxiliary voltages to the respective auxiliary voltage inputs of the switch drivers by turning the power semiconductors sequentially on and off.

A multilevel inverter control system having logic configured to substantially minimize and area between a target waveform and a step signal of a multilevel inverter.