186 results about "Z-source inverter" patented technology

The invention discloses a stored energy type standard-Z source photovoltaic power generation control system and method. The control system comprises a controller and a stored energy type standard-Z source inverter, wherein the controller comprises a capacitor voltage outer ring and a stored energy battery current inner ring and is used for regulating the direct-connection duty ratio of the inverter, thus the voltage of a DC (direct-current) bus can be constant, although the photovoltaic cell voltage is changed in a wide range; and the output power of the inverter is controlled by a power ring, and the output power of photovoltaic cells and the inverter is controlled so as to carry out charge-discharge management on stored energy batteries, thus realizing maximum power tracking. According to the invention, single-stage power transform is used to complete boosting, reduction voltage, inversion and energy storage, so that a simpler structure is used to realize minimum inverter capacity, thus ensuring the voltage of the DC bus to be constant and a power grid to obtain stable power, thereby maximally collecting solar energy and improving generating efficiency.

The invention provides a high-gain Z-source inverter, comprising a three-phase inverter, which is composed of a direct-current voltage source and a three-phase inversion bridge. The high-gain Z-source inverter further comprises a Z-source network, which is composed of a power diode, a switch inductor and a capacitor. The high-gain Z-source inverter is characterized in that a single inductor is replaced by a branch circuit of the switch inductor; the head end of the Z-source network is connected with the positive electrode of a power supply; the tail end of the Z-source network is connected to the positive end of the three-phase inversion bridge; and the inversion bridge and the power supply are grounded commonly. Compared with the traditional Z-source inverter, the Z-source inverter disclosed by the invention is capable of improving the boost capacity of the inverter, realizing a high modulation factor and improving the output quality of the whole inverter; and simultaneously, the voltage stress of the Z-network capacitor can be effectively reduced so as to reduce the volume and the weight of the inverter.

A medium voltage adjustable frequency drive includes an input isolation transformer having a three-phase input and a three-phase output, a converter having a three-phase input electrically connected to the three-phase output of the input isolation transformer and an output providing a direct current bus, an inverter having an input electrically connected to the output of the converter and a three-phase output, and a pre-charge circuit. The pre-charge circuit includes a ferro-resonant transformer circuit having a primary winding structured to input a low voltage and a secondary winding structured to output a medium voltage and provide a constant current source. The pre-charge circuit also includes a medium voltage diode bridge having an input receiving the medium voltage from the secondary winding of the ferro-resonant transformer circuit and an output structured to provide the constant current source to the direct current bus.

The present invention provides a z-source inverter and its soft starting method, belonging to power electronic converter. The inverter main circuit is composed of a DC voltage source, a three-phase inverter bridge, a z-source network, a power diode, characterized in that the positive end of the three-phase inverter bridge is connected to the cathode of the DC voltage source, the negative end of the three-phase inverter bridge is connected to the Z source network. Compared with the voltage source type and the current source type inverter, the Z source inverter realizes pressure raising change function, and the upper and the lower switch tubes of the same bridge arm are directly passing, so the dead zone does not need, the circuit structure is simple, having high credibility. Compared with the traditional Z source inverter, the capacitor voltage of the Z source network in the Z source inverter has small stress, and realizing the soft start of the transformer, avoiding the problems of large voltage and current when the traditional Z source inverter starts, the work of the transformer is safe and credible, and having light volume and weight.

The invention relates to an SVPWM (Space Vector Pulse Width Modulation) control method for a Z-source inverter, belongs to the technical field of inverter control and solves the problem of generation of a larger inductive current ripple caused by the existing SVPWM control method for the Z-source inverter. The states of three switching tubes of an upper bridge arm are represented by eight vectors, and the eight vectors divide a control interval into six sectors. For taking the third (III) sector as an example, the vectors taking actions in Ts in each SVPWM period are allocated sequentially from left to right as 111, 110, 100, 000, 000, 100, 110 and 111, wherein the total acting time of a traditional zero vector is set as T0; the total acting time of a direct-through zero vector is set as t0 which is greater than 0 and less than or equal to T0; and the total acting time t0 of the direct-through zero vector is divided into four sections inserted between the acting times of the traditional zero vector and an adjacent effective vector, thereby realizing SVPWM control of the Z-source inverter. The SVPWM control method is suitable for the SVPWM control of the Z-source inverter.

A method and an apparatus for setting up synchronization, with a power grid, of an inverter having a photovoltaic generator as a primary energy source is disclosed. The inverter is supplied with the energy from an additional energy source connected in parallel with input terminals of the inverter, wherein the additional energy source is a DC energy source operated independent from the primary energy source. The frequency, phase relationship and output voltage of the inverter supplied from the additional DC energy source are matched to the frequency, phase relationship and output voltage of the power grid, whereafter the primary energy source is connected to the inverter. With this method, an inverter dimensioned for a permissible open-circuit voltage can also be used under operating conditions, without requiring modifications of the circuitry of the primary energy source.

The provided current source inverter includes a buck converter having an input capacitor and an output inductor, receiving a DC input voltage, and generating an output inductor current, a DC/AC converter having an output capacitor, receiving the output inductor current and generating an AC output voltage, a load coupled to the DC/AC converter, and an energy clamp circuit coupled to the buck and the DC/AC converters. The energy clamp circuit includes a first diode and a second diode, provides a discharging route while the load is disconnected with the output capacitor such that the electrical power stored at the output inductor could be discharged to the output capacitor and the input capacitor and avoids an inrush current.

The invention discloses a uniform prediction control method for quasi-Z source inverter-permanent magnet synchronous motor systems. According to the method, stator current d and q axis components areobtained through coordinate transformation, each control variable is obtained through a delay compensation link, a torque given value is obtained through a rotation speed closed loop, and d and q axiscurrent given values are obtained to calculate a stator flux linkage given value; an inductive current given value is calculated through a power compensation manner so as to obtain an inductive current critical value; and an optimum vector is judged according to a relationship between inductive current and the inductive current given value so as to obtain each control variable at the next moment,the control variables at the next moment are substituted in an evaluation function to obtain an optimum vector, and a switch state corresponding to the optimum vector is output to an inverter. The uniform prediction control method is capable of decreasing the operand of controllers, avoiding the influences, on prediction control of quasi-Z source inverter-permanent magnet synchronous motor systems, of quasi-Z source inverter negative modulation, realizing the uniform prediction control of quasi-Z source inverter-permanent magnet synchronous motor systems, and solving the control conflict problems in two-stage control.

The invention discloses a quasi Z source inverter which comprises a direct-current power source, an inverter, a switch inductance set and an auxiliary circuit in mutual connection. The quasi Z source inverter can realize boost-buck of any proportion of voltage on a direct-current side without a DC-DC (direct current) booster circuit before inversion, has good effects in terms of reliability and efficiency, has higher boost-buck times than common impedance network type inverters, is free of impact to an electrolytic capacitor when a system is started, can realize soft start characteristics and has the advantages of high step-up, stability, small size, high efficiency and the like.

The invention relates to a quasi Z-source inverter with high boost gain. The quasi Z-source inverter comprises a DC power supply Vin, a quasi Z-source boost network, and a three-phase inverter. The quasi Z-source boost network comprises a tap inductor, a first diode D1, a first capacitor C1, a second capacitor C2, and a switched inductor group. When the three-phase inverter is in a non shoot-through state, the tap inductor charges the first capacitor C1 and the switched inductor group charges the second capacitor C2 in order to improve the boost capability of the Z-source inverter and reduce the voltage stress of the first capacitor C1, the second capacitor C2, and the switched inductor group. Compared with a product in the prior art, the quasi Z-source inverter uses single-stage structure and reduces circuit size and cost. A shoot-through zero vector enables the top bridge arm and the bottom bridge arm of an inverter bridge to be simultaneously switched on, thereby improving circuit security. The quasi Z-source inverter reduces voltage stress of devices while achieving high boost gain.

The present invention discloses a series quasi Z source inverter based grid-tied PV control method. A PV battery inverter system is seen as a virtual synchronous generator, and an integral of an output voltage of a series quasi Z source inverter is taken as a virtual motor magnetic chain. An outer ring is controlled by using a power ring, so that active power transmission and reactive power compensation are realized. An inner ring is a current ring, so that current rapid tracking is realized. PI modulation is performed on the current inner ring, so as to generate a modulated wave signal. Three times of harmonic wave modulation is performed on a modulated signal obtained at a PV side and the modulated wave signal. On and off of an inverter bridge are controlled, so as to realize power adjustment of the grid-tied PV system. According to the method, a virtual synchronous generator quasi direct power control policy is adopted for controlling the system, the virtual magnetic chain directly orients, an alternating current voltage sensor is omitted, system reliability is improved, device cost is saved, quasi direct power control can directly control active power and reactive power of the grid-tied inverter, and the system has the advantages of simple structure and good dynamic response performance.

The invention relates to a model predictive control method for reducing the switching frequency of a quasi-Z source inverter, which comprises the steps of establishing system models of the quasi-Z source inverter, including the establishment of system models in a non-through state and a through state; determining and selecting a voltage vector criterion, including a transitional zero vector, six traditional effective vectors and a through vector; designing a cost function; and introducing a switching frequency-related weight item into the cost function in order to reduce the switching frequency of the quasi-Z source inverter, wherein the switching frequency of the system can be reduced through adjusting a weighting factor of the switching frequency weight item. The reduction of the switching frequency of the system will bring the following two advantages: first, the loss of the system at the on-off switching time is reduced by reducing the switching frequency of the system so as to improve the working efficiency of the whole system; and second, the reduction of the switching frequency of the system also means that the service life of an IGBT is longer.