48results about How to "Solve the pressure equalization problem" patented technology

The invention discloses a photovoltaic grid-connected inverter. The photovoltaic grid-connected inverter comprises a photovoltaic array, a plurality of unit bodies, three unit body series branches, an alternating current reactor, a grid-connected switch, unit body controllers and a master controller, wherein the preceding stage of each unit body is respectively connected with the photovoltaic array; the unit body series branches are connected into a power grid after being connected with the alternating current reactor and the grid-connected switch in series; and each unit body comprises one of the unit body controllers. The invention also discloses a photovoltaic grid-connected inverter control method. In the inverter and the control method disclosed by the invention, the unit bodies are connected in series instead of directly connecting power devices in series, so that the problem of voltage-sharing of devices are solved; the power level is high; the limitation of load capacity of power electronic devices is overcome; a unit phase shift wave overlapping technology is adopted, so that an output harmonic wave is small; because of the action of an energy storage battery, when illumination disappears suddenly, a system cannot be off-grid and standby suddenly; and because of adopting a unit body automatic bypass technology, the security of the system is improved.

The invention discloses a modularized device for conversion between high-voltage direct current and direct current. The modularized device for conversion between the high-voltage direct current and the direct current comprises at least two direct-current-direct-current conversion modules which are the same in structure, wherein the input ends of all the direct-current-direct-current conversion modules are connected in series in sequence in the forward direction and then are arranged between a positive pole and a negative pole of a high-voltage side in a connected mode, and the output ends of all the direct-current-direct-current conversion modules are connected in series or in parallel or in a series-parallel mode according to the voltage class requirement of a low-voltage side, and then are arranged between a positive pole and a negative pole of the low-voltage side in a connected mode. Each direct-current-direct-current conversion module comprises a high-voltage side converter module, a low and medium frequency sine wave transformer and a low-voltage side converter module, wherein the output end of each high-voltage side converter module is connected with an input winding of each low and medium frequency sine wave transformer, and an output winding of each low and medium frequency sine wave transformer is connected with the input end of each low-voltage side converter module. The modularized device for conversion between the high-voltage direct current and the direct current can solve the problems of voltage resistance and voltage sharing of switching devices on the high-voltage side, improve the transmission capacity, and have a certain application prospect in places with high-voltage input high power.

The invention discloses a dual-output single-phase six-switch block modular multilevel converter (MMC) inverter and a control method thereof. The inverter is composed of a direct-current power supply, a first bridge arm, a second bridge arm, a first load and a second load. The first bridge arm and the second bridge arm are formed by series connection of upper switch blocks, intermediate switch blocks, lower switch blocks and coupling inductors; the two ends of the first load are respectively connected to the upper ends of the intermediate switch block of the first bridge arm and the intermediate switch block of the second bridge arm; and the two ends of the second load are respectively connected to the lower ends of the intermediate switch block of the first bridge arm and the intermediate switch block of the second bridge arm. According to the inverter, the carrier phase-lifting PWM control is used; and the inverter has two paths of alternating-current outputs with the 2N+1 levels. The voltage stress carried by each switching tube in a power switch unit is one-Nth of that of the direct-current power supply voltage; and thus the inverter is suitable for high-voltage high-power and dual-load occasions. Besides, both the primary side and the secondary side of the coupling inductor of the first bridge arm and the primary side and the second side of the coupling inductor of the second bridge arm can be replaced by two independent inductors of first inductors and second inductors.

The invention relates to a novel high-capacity multi-level hybrid clamping topology and a topological method. The structure is a three-phase four-bridge arm structure; one bridge arm is added based ona conventional hybrid three-phase structure and is specially used for clamping; further, the structure does not need a voltage balancing circuit and an independent DC voltage source, and can realizemidpoint potential balance under all load characteristics; the conventional clamping device is improved, namely, a diode clamping device with a three-phase four-bridge arm topology is transformed intocapacitor clamping; an active switch transistor is added as a clamping device, so that the topology realizes current bidirectional path, and solves a problem of imbalance capacitance and voltage. Thestanding voltage balance problem in power switch in series operation is solved, further, a better way for realizing high voltage energy control based on low withstand voltage power switch is provided.

The invention discloses a dynamic voltage-sharing control method for a power module of a chained multi-level converter. The voltage-sharing method is performed by a single-phase software phase-locked loop, a sign function and a proportional controller connected in series, and comprises the steps that: the software phase-locked loop detects the phase of a power frequency component in the output current of the chained multi-level converter and inputs the phase information into the sign function to obtain the regulating direction of the voltage-sharing control, then the regulating variable of the voltage-sharing control is obtained by the proportional controller according to the direct voltage deviation of a single power module, at last the voltage-sharing component in the output voltage of the power module is obtained through multiplying the regulating direction with the regulating variable, and thus the output voltage of the module is obtained by summing the voltage-sharing component with the momentary value of the output voltage of the phase. The dynamic voltage-sharing control method overcomes harmonic current under the working condition of small current and influence of dynamic load which changes rapidly on the voltage sharing of the power module, and effectively solves the voltage-sharing problem of the chained multi-level converter under the working conditions of light load and dynamic load.

The invention provides a method for controlling voltage of direct current capacitors in a double-output and three-switch-set MMC inverter. The method comprises the step of controlling the voltage of the direct current capacitors of power switch units of the upper switch set, the middle switch set and the lower switch set, and the step of sampling the voltage of the direct current capacitors of the power switch units of the upper switch set, the middle switch set and the lower switch set and stabilizing the voltage of the direct current capacitors of the power switch units through voltage feedback and PI adjustment. According to the method, the voltage of the direct current capacitors in the double-output, one-phase and three-switch-set MMC inverter is balanced and stabilized, the double-output, one-phase and three-switch-set MMC inverter can have two paths of N+1 electrical level alternating current output, the quality of the output current waveform is very high, the voltage stress borne by each switch tube in the power switch units is only 1/N of the direct current bus voltage, the voltages borne by all the switch tubes are equal in the working process of a converter, and the voltage-sharing problem of the switch tubes is solved very well.

The invention provides a 3N+3 switch set MMC AC-AC converter and a control method thereof. The 3N+3 switch set MMC AC-AC converter is composed of N three-phase alternating-current input/outputs, a first bridge arm, a second bridge arm, a third bridge arm and a first capacitor, each of the first bridge arm, the second bridge arm and the third bridge arm is formed by serially connecting N+1 switch sets and two inductors, each switch set is formed by serially connecting n power switch units, and three ends of each three-phase inductive load serve as a three-phase alternating-current output, wherein N and n are positive integers. Carrier phase-shifting PWM (pulse-width modulation) control is adopted, and each three-phase alternating-current output is converted into an alternating-current input with line voltage to be 2n+1 levels and converted into an alternating-current output with line voltage to be 2n+1 levels through AC-AC conversion to power a load; voltage stress borne by each switch tube in an MMC power switch unit is 1/n of voltage of a direct-current power source, so that the problem of voltage sharing of the switch tubes is solved, and the 3N+3 switch set MMC AC-AC converter is suitable for being used in places with high voltage and high power.

The invention provides a single-phase six-switching-group MMC AC-AC converter and a control method of the single-phase six-switching-group MMC AC-AC converter. The converter comprises an alternating current input power supply, an input inductor, a first bridge arm, a second bridge arm, a first capacitor and a load. The first bridge arm and the second bridge arm are respectively formed by connecting an upper switching group, a middle switching group, a lower switching group, a first inductor and a second inductor in series. Each switching group is formed by connecting N power switching units in series. The two ends of the load serve as output. N is a positive integer. The converter is controlled by a carrier phase-shifting PWM, the alternating current input power supply is converted into alternating current input at the 2N+1 level and supplies power to the load after being converted into alternating current output at the 2N+1 level through AC-AC conversion, stress of voltage borne by each switching pipe in each MMC power switch unit is only one Nth that of the voltage of a direct current power supply, the problem of voltage equalizing of the switching pipes is well solved, and the single-phase six-switching-group MMC AC-AC converter is suitable for places with high voltages and high power.