31results about How to "Reduce output harmonic content" patented technology

The invention provides an electromagnetic mixed compensation system for quality of electric energy in electrified railways. The electromagnetic mixed compensation system comprises an RPC, two MSVCs and a V / V traction transformer. The V / V traction transformer is in a V / V type formed by connecting two single-phase transformers. The primary side of the V / V traction transformer is connected to a three-phase public power grid, and traction power supply arms serve as two output ends of the secondary side of the V / V traction transformer. Each MSVC comprises a magnetic controlled reactor, a third single harmonic filter branch circuit and a fifth single harmonic filter branch circuit, and the magnetic controlled reactor, the third single harmonic filter branch circuit and the fifth single harmonic filter branch circuit are connected in parallel. The RPC comprises two H-bridge converters with a shared direct-current side. The MSVCs and the RPC are used in cooperation with each other, and therefore the problem of unbalanced harmonic and negative sequences of the electrified railways is solved. Due to the adoption of MSVC and RPC mixed compensation, compensation capacity of the RPC is effectively reduced, and the construction cost of the system is accordingly reduced.

The invention discloses an all-digital naturally sampling SPWM control method and system based on FPGA, the concrete control method comprises the steps as follows: generating the synchronizing signal; accumulating the address for the sine modulation wave to obtain the sine function value of the sine modulation wave of current region; determining the region of the current switch state according to the sine function value of the sine modulation wave and triangular carrier slope state, the sine modulation wave and triangular carrier slope are different in different regions; taking the clock signal of FPGA as the standard, fast sampling sine wave and triangular wave and comparing the value, using the counter for counting the clock signal; stopping comparing while the relationship of the sine modulation wave and triangular wave changes and recording the number of clock signal, determining the start and stop ideal value for the part according to the number of clock signal; adjusting the start and stop ideal value to obtain the actual start and stop time for realizing the symmetry dead zone.

The invention relates to a three-level ANPC convertor neutral-point voltage balance control method. The method comprises the following steps of (1) acting on a three-level ANPC convertor through an SVPWM (space vector pulse width modulation) pulse sequence; (2) detecting the voltage of the direct current side capacitor of the convertor in real time to obtain a neutral-point voltage, and comparing the neutral-point voltage with a reference neutral-point voltage to determine whether the direct current side capacitor requires charging or discharging; (3) in real time detecting the positive and negative direction of the three-phase load current of the convertor; (4) integrating detecting values of the steps (2) and (3), within every switching period, dynamically adjust the duty ratio of the zero state of the switch sequence of a three-phase bridge arm until neutral-point voltage balance, and repeating the step to maintain fluctuation of the neutral-point voltage within a relatively small range. The three-level ANPC convertor neutral-point voltage balance control method can dynamically adjust the charging and discharging time of the capacitor according to the direction of the three-phase load current and the size of the neutral-point voltage to rapidly balance of the neutral-point voltage and to maintain fluctuation of the neutral-point voltage within a relatively small range.

The invention provides a low frequency model predictive control method based on a hybrid modular multilevel converter. A low frequency model predictive control policy based on upper, middle and lowerlayer control is realized. The upper-layer control establishes an index function and selects a bridge arm output level which meets current, circulating current and bridge arm capacitor voltage controlrequirements of the alternating current side. The optimization calculation amount is effectively reduced. The middle-layer control uses an H-bridge module control algorithm to stabilize the H-bridgemodule capacitor voltage. The equivalent output level is calculated. The number of switching of a bridge arm half-bridge sub-module is determined. The lower-layer control determines the switching signal of each sub-module according to the optimization control policy of the sub-module capacitance voltage. Balance control of the sub-module capacitance voltage is realized. The average switch frequency of sub-modules is reduced.

The invention discloses a 9-level inversion topology circuit comprising two T-type 3-level circuits, two switch tubes, and a LC filter circuit; input power supply heteropolar ends of the two T-type 3-level circuits are connected through the two switch tubes; the LC filter circuit is connected on an inversion bridge arm center node of the two T-type 3-level circuits; the input power supply-voltage ratio of the two T-type 3-level circuits is 1. Compared with a conventional multi-level inversion circuit, more levels are formed under unit switch tube of the 9-level inversion topology circuit, i.e., less switch tubes can form more levels, thus easily forming multi-level sine pulse-width modulation waveform simulation AC output, greatly reducing output harmonic wave content, reducing the output filter volume, greatly reducing inverter manufacture cost and material waste, and improving the inverter efficiency.

The invention provides a grid-connected inverter circuit and a control method thereof. The grid-connected inverter circuit comprises an inverter, an (N+1)-port transformer, a 2N-phase rectifier, 2N voltage dividing capacitors and a (2N+1)-end inverter; direct-current voltage is subjected to high-frequency inversion via the inverter to generate high-frequency square wave, the high-frequency square wave passes through the (N+1)-port transformer to boost the voltage into voltage of N voltage levels, the square wave of the N voltage levels is respectively rectified to form voltage of 2N different levels, the voltage of 2N different levels and a zero potential grounding point form (2N+1) level branches, the levels are isolated by the capacitors connected in series longitudinally and charge the capacitors, and the (2N+1) level branches are respectively connected with the (2N+1)-end inverter. The whole circuit adopts multi-level inversion, so that the content of output harmonic is greatly reduced, additional high-capacity filters are not needed, and the structure is simple.

The invention discloses a modular multi-terminal flexible DC micro-grid network, which comprises a DC bus, a controllable module, an uncontrollable module and a large grid of a multi-terminal flexibleDC micro-grid. The controllable module comprises one or more controllable distributed power sources, a battery energy storage system, a DC load and an AC load, wherein each controllable distributed power source is incorporated into the DC bus through a distributed power source grid connection device, the battery energy storage system is connected to the DC bus through a stored energy grid connection device, the DC load is directly connected with the DC bus, and the AC load is connected with the DC bus through an AC load grid connection device. The control objective is simplified as the bus voltage control of the DC micro-grid, and thus, the control mode can be selected easily. The micro-grid is modularized and changed from a previous 'designed micro-grid' into an 'assembled micro-grid', and the DC micro-grid is divided into multiple controllable modules and uncontrollable modules, which can save the construction cost of the micro-grid, reduce the floor area and facilitate the subsequent expansion of the micro-grid.

The invention discloses a high-performance test system for a pump. The system comprises an incoming power supply cabinet, a frequency conversion system, an outgoing power distribution system and a test console. The outgoing line power distribution system is connected with a motor; the motor is connected with a pump; the inlet wire power supply cabinet is connected with the frequency conversion system through a cable. The frequency conversion system is connected with the outgoing line power distribution system through a cable, the incoming line power supply cabinet, the frequency conversion system, the outgoing line power distribution system, the motor and the pump are connected with the test console through cables and communication lines, and the test console is used for detecting signalsof the incoming line power supply cabinet, the frequency conversion system, the outgoing line power distribution system, the motor and the pump and feeding back the signals. The invention provides a high-performance test system for a pump, which not only can complete a conventional function test and a performance test of the pump according to the requirements of a pump test working condition, butalso can meet the test requirements of a pump with a wide capacity range and multiple voltage classes, and is low in cost and small in space occupation ratio.

The invention discloses an orthogonal iron core type controllable electric reactor with a wedge-shaped groove and an equivalent magnetic path length calculating method of the orthogonal iron core type controllable electric reactor with the wedge-shaped groove under direct-current magnetic bias. The controllable electric reactor comprises a working iron core and a control iron core with the wedge-shaped groove. According to the controllable electric reactor and the equivalent magnetic path length calculating method, as the wedge-shaped groove is formed in the control iron core, the harmonic content output by the controllable electric reactor can be effectively reduced, the defect that a traditional electric reactor is high in harmonic content is overcome, and the working performance of the electric reactor is improved. Meanwhile, simulation software ANSOFT special for an electromagnetic field is adopted to calculating the alternating current equivalent magnetic path length, data of the magnetic induction intensity on a specific cross section in the orthogonal iron core type controllable electric reactor are derived and processed according to a studied algorithm, and the equivalent magnetic path length is accordingly calculated. By means of the method, errors, caused by unclear magnetization conditions of the internal iron cores, of calculation of the equivalent magnetic path length in a traditional method are reduced, the alternating current magnetization curve of the electric reactor has the higher scientificity accordingly, and guarantees are provided for studying the iron consumption and other characteristics of the orthogonal iron core type controllable electric reactor.

The invention discloses a common direct-current bus bidirectional converter and a control method thereof. The bidirectional converter mainly comprises an active and reactive controller, a CPS-SPWM controller and a plurality of converter modules. The control method mainly comprises the following steps: judging whether a load is accessed to a direct-current bus or not; if yes, detecting the number of converter modules connected to the system; judging whether an alternating-current power grid needs active feedback or not; if the alternating-current power grid does not need active feedback, controlling all the modules connected to the system in a voltage and current double-closed-loop mode, controlling all the modules through the same reference voltage, or else, averagely distributing active power needing to be fed back to all the working converter modules, changing the feedback current direction of the working converter modules, and then adopting power outer-loop current and inner-loop double-closed-loop control; when no load exists, judging whether the alternating-current power grid needs electric energy quality management or not, and if yes, adopting a voltage and current double-closed-loop control method under a d-q coordinate system, and adding reactive power and harmonic waves needing to be output into current loop control; and if not, only keeping the direct-current voltage.

The invention discloses a combined type inverter. The combined type inverter comprises input voltage, and a capacitor C1 connected between positive and negative electrodes of the input voltage in parallel, the positive electrode of the input voltage is connected with drain electrodes of an MOS tube Q1, an MOS tube Q3 and an MOS tube Q5 in parallel, a source electrode of the MOS tube Q1 is connected with a drain electrode of an MOS tube Q2, a source electrode of the MOS tube Q3 is connected with a drain electrode of an MOS tube Q4, a source electrode of the MOS tube Q5 is connected with a drain electrode of an MOS tube Q6, source electrodes of the MOS tube Q2, the MOS tube Q4 and the MOS tube Q6 are connected with the negative electrode of the input voltage; and a position between a source electrode of the MOS tube Q1 and the drain electrode of the MOS tube Q2 is connected between the source electrode of the MOS tube Q5 and the drain electrode of the MOS tube Q6 through an inductor L2, a capacitor C2 and an inductor L3 in sequence, a position between the source electrode of the MOS tube Q3 and the drain electrode of the MOS tube Q4 is connected between the source electrode of the MOS tube Q5 and the drain electrode of the MOS tube Q6 through an inductor L1, the capacitor C2 and the inductor L3 in sequence, and the capacitor C2 is connected with a load R1 in parallel.

The invention discloses an output harmonic suppression method for an H-bridge cascaded static synchronous compensator, and the method sequentially comprises the following steps: adding a voltage feedforward control link on the basis of CPS-SPWM modulation; dividing the average voltage control of each section of direct-current capacitor into average control and balance control; optimizing the modulation performance of the output harmonic suppression of the H-bridge cascaded STATCOM; adding a current decoupling control link; taking a dq-axis component output by the low-pass filter as a referenceinstruction current for PI feedforward decoupling control; controlling the compensation signals to achieve current static-error-free tracking and harmonic treatment. Independent control and trackingof parameters are achieved, the quality of voltage and current output by the compensator is improved, then the output harmonic content of the static synchronous compensator is reduced, and the controlperformance of the static synchronous compensator is optimized.

The present invention provides a method and device for predicting and compensating DC bus ripple voltage of an AC motor driver, using the predicted value of DC bus voltage, performing voltage compensation calculation through a ripple voltage compensation algorithm, and obtaining Ualpha* and Ualpha* required by the SVPWM space vector modulation algorithm Ubeta*, then execute the SVPWM space vector modulation algorithm, set the PWM buffer register, update the flag, and the CPU will automatically load the new value and output the PWM waveform in the next reload cycle. The present invention solves the problem of time delay in the implementation of the DC bus voltage sampling and compensation method in the prior art, performs precise compensation control on the DC bus ripple voltage, and avoids the distortion of the pulse width modulation output of the driver as much as possible, and the distortion of the output voltage and current waveform , reduce the output harmonic content and improve the driving performance of the driver.

The invention provides a low-frequency model predictive control method based on a hybrid modular multilevel converter, which realizes a low-frequency model predictive control strategy based on upper, middle and lower layers of control: The current, circulating current and bridge arm capacitor voltage control the required bridge arm output level, and effectively reduce the amount of optimization calculation; the middle layer control uses the H bridge module control algorithm to stabilize the H bridge module capacitor voltage and calculate its equivalent output level. And determine the switching number of the half-bridge sub-module of the bridge arm; the lower layer control determines the switching signal of each sub-module according to the optimal control strategy of the sub-module capacitor voltage, realizes the balanced control of the sub-module capacitor voltage, and reduces the average switching of the sub-module frequency.

The invention discloses a T-shaped multi-level inversion circuit, and the circuit comprises two T-shaped three-level circuits, two switching tubes, two pairs of reverse parallel switching tubes, and an LC filter circuit. The input power heteropolarity ends of the two T-shaped three-level circuits are connected through the two switching tubes, and the two pairs of reverse parallel switching tubes enables the homopolarity input power ends of the two T-shaped three-level circuits to be connected. The LC filter circuit is connected to central nodes of inversion bridge arms of the two T-shaped three-level circuits, and the ratio of the input power voltages of the two T-shaped three-level circuits is 5. The circuit generates more levels through fewer switching tubes, greatly reduces the number of power switching tubes, further reduces the cost of a multi-level inverter, improves the efficiency of the inverter, and reduces the switching frequency.

The invention provides a single-input switched capacitor multi-level inverter and its modulation method. The switching device controls the working state of the capacitor to realize the conversion and transmission of electric energy, and has the advantages of small size, high efficiency, and high power density; The inverter is based on the series-parallel conversion of the switched capacitor structure, which can generate more output levels with fewer power devices, simplifies the topology structure, and reduces the output harmonic content. It has the advantages of small number of devices, simple control, single power input, Capacitive self-balancing and independent application to inductive loads and other advantages.

The present invention aims to propose a dead zone compensation method for frequency converters, which includes the following steps: the switch switching time setting step is set in one sampling period according to the on or off state of the switch tube in the three-phase inverter circuit Several switch switching times, the several switch switching times are combined with the switching delay and the dead zone delay of the switching tube. The step of obtaining the voltage map is to obtain the voltage map according to the switching time of the switch, the voltage of the DC bus, and the voltage drop of the switch tube and the diode in the three-phase inverter circuit. In the voltage map, the voltage is a constant value at each switching time of the switch. In the voltage calculation step, the maximum value, the middle value and the minimum value of the voltage are calculated according to the switching time of the switch and the fixed value of the voltage during the switching time of the switch. In the switch switching time calculation step, the actual time of each switch switching time is determined in the actual sampling period according to the voltage map, the maximum value, the middle value and the minimum value. The invention can make the compensation more timely and accurate.

The invention discloses a method for series triple-phase hopping AC-AC frequency conversion. A main frequency conversion circuit is formed on the basis of the same circuit as the traditional series triple thyristor AC-AC frequency conversion method, the frequency conversion control is carried out by an innovative method called phase hopping frequency conversion, the idea of frequency conversion control is to control each circuit separately, a pair of thyristors in a positive group and a negative group are simultaneously triggered for each repetition, communicating an output of the heavy circuit with a phase input of the heavy circuit, and the second trigger is carried out after a time interval related to the desired output frequency, so that the re-output terminal is connected with the next phase input, and the phase of the output voltage is continuously hopped by constantly switching the connection relationship, thereby obtaining the effect of changing the output frequency as a whole.At the same time, the phase of the output voltage of each multiple circuit is arranged according to the requirement, and the magnitude of the total output voltage is regulated by the vector superposition of the output voltages of each multiple circuit. The method has the advantages of low cost and high reliability.

The invention discloses a transformer-free three-phase DC-AC convertor for a direct-current micro grid. The transformer-free three-phase DC-AC convertor for the direct-current micro grid comprises at least two DC-AC conversion units which are connected in parallel in a fault-phase mode. In addition, the DC-AC convertor can be automatically controlled by adopting a CPU through a PWM control technology. According to the transformer-free three-phase DC-AC convertor for the direct-current micro grid, a transformer does not need to be inserted between a direct-current bus and a low-voltage grid, the DC-AC convertor can work within the best modulation rate range, the convertor efficiency is improved, and harmonic wave output is reduced.

The invention discloses a T-type multi-level inverter circuit, which comprises two T-type three-level circuits, two switch tubes, two pairs of anti-series switch tubes and an LC filter circuit; two T-type three-level circuit input The opposite polarity ends of the power supply are connected through two switch tubes, and two pairs of anti-series switch tubes connect the input power of the T-type three-level circuit to the same polarity end, and the LC filter circuit is connected to the inverter bridge arms of the two T-type three-level circuits On the central node, the ratio of the input power supply voltages of the two T-shaped three-level circuits is 5. The invention uses fewer switching tubes to generate more levels, greatly reduces the number of power switching tubes, further reduces the cost of the multi-level inverter, improves the efficiency of the inverter, and reduces the switching frequency at the same time.

The invention discloses a nine-level inverter topology circuit, which includes two T-type three-level circuits, two switch tubes, and an LC filter circuit; the input power terminals of the two T-type three-level circuits pass through two The two switch tubes are connected, and the LC filter circuit is connected to the center node of the inverter bridge arm of the two T-shaped three-level circuits. The ratio of the input power supply voltages of the two T-shaped three-level circuits is 1. Compared with the traditional multi-level inverter circuit, the nine-level inverter topology circuit of the present invention generates more levels per unit of switch tubes, that is, more levels are generated with fewer switch tubes, and it is convenient to generate multiple levels. The level sinusoidal pulse width modulation waveform simulates the AC output, the output harmonic content is greatly reduced, the volume of the output filter is reduced, the manufacturing cost and material waste of the inverter are greatly reduced, and the efficiency of the inverter is improved.

The invention discloses a cascade six-fold phase-hopping AC-AC frequency conversion method, A main frequency conversion circuit is for on that basis of the same circuit as the traditional serie triplethyristor cycloconverter method, the frequency conversion control is carried out by an innovative method called phase hopping frequency conversion, the idea of frequency conversion control is to control each circuit separately, A pair of thyristors in a positive group and a negative group are simultaneously triggered for each repetition, communicating an output of the heavy circuit with a phase input of the heavy circuit, and the second trigger is carried out after a time interval related to the desired output frequency, so that the re-output terminal is connected with the next phase input, and the phase of the output voltage is continuously jumped by constantly switching the connection relationship, thereby obtaining the effect of changing the output frequency as a whole. At that same time, the phase of the output voltage of each multiple circuit is arrange according to the requirement, and the magnitude of the total output voltage is regulated by the vector superposition of the output voltages of each multiple circuit. The cascade six-fold phase-hopping AC-AC frequency conversion method has the advantages of low cost and high reliability.

The invention relates to a low frequency model prediction control method based on a hybrid modular multi-level current converter. Each bridge arm is equipped with N sub modules, namely, semi-bridge modules, and one full bridge module. The capacitor voltage of the full bridge module is assigned as a half of each sub module. The low frequency model prediction control method concretely includes taking upper and lower bridge arm module input number as a control variable, performing layering control on AC current, loop current and capacitor voltage of the sub modules and selecting the optimal switch state combination by utilizing an AC current index function; adjusting the sub module input number of the upper bridge and the lower bridge arms by adopting a loop current index function; determining the final sub module input number through combination with the working state of the full bridge module; and finally calculating the sub module input number difference of neighboring time points, adopting an optimization voltage-sharing strategy for realizing balance control of the capacitor voltage of the sub modules, so that the system switching frequency is reduced. The method is clear in physical model and does not need to consider complex parameter setting and weight index design. Digital control is easy to realize and optimizing computation workload is reduced.

The invention discloses a transformerless three-phase DC-AC converter for a DC microgrid, which comprises: at least two DC-AC conversion units, at least two DC-AC conversion units connected in parallel; wherein: two DC ‑AC conversion units are wrongly connected in parallel. In addition, the CPU can also be used to automatically control the DC-AC converter through PWM control technology. The transformerless three-phase DC-AC converter for the DC micro-grid of the present invention does not need to insert a transformer between the DC bus and the low-voltage power grid, and can allow the DC-AC converter to work in the best modulation rate range, improving the efficiency of the DC-AC converter. converter efficiency and reduced harmonic output.

The invention discloses a combined type inverter. The combined type inverter comprises input voltage, and a capacitor C1 connected between positive and negative electrodes of the input voltage in parallel, the positive electrode of the input voltage is connected with drain electrodes of an MOS tube Q1, an MOS tube Q3 and an MOS tube Q5 in parallel, a source electrode of the MOS tube Q1 is connected with a drain electrode of an MOS tube Q2, a source electrode of the MOS tube Q3 is connected with a drain electrode of an MOS tube Q4, a source electrode of the MOS tube Q5 is connected with a drain electrode of an MOS tube Q6, source electrodes of the MOS tube Q2, the MOS tube Q4 and the MOS tube Q6 are connected with the negative electrode of the input voltage; and a position between a source electrode of the MOS tube Q1 and the drain electrode of the MOS tube Q2 is connected between the source electrode of the MOS tube Q5 and the drain electrode of the MOS tube Q6 through an inductor L2, a capacitor C2 and an inductor L3 in sequence, a position between the source electrode of the MOS tube Q3 and the drain electrode of the MOS tube Q4 is connected between the source electrode of the MOS tube Q5 and the drain electrode of the MOS tube Q6 through an inductor L1, the capacitor C2 and the inductor L3 in sequence, and the capacitor C2 is connected with a load R1 in parallel.

The invention discloses a three-PWL double-current hysteresis power amplifier which comprises an error comparing module, a PI current controller module, a double-current hysteresis comparing module, an optical coupler isolation driving module, a power changing module and a current feedback current. The traditional current hysteresis control and the three-PWL modulation are combined, thus, the advantages of simple structure, good current tracking performance and low cost of the hysteresis control circuit and the advantages of small current ripples, high control accuracy and low output harmonicwave content are obtained. The power amplifier can be used for all occasions with the requirements of controlling the output current, i.e. the power amplifying part of an active electromagnetic bearing or a vibration generator, and the like.

The invention discloses a three-phase three-phase series-connected three-phase stepping alternating-current frequency conversion method. The main frequency conversion circuit is formed on the basis of the same circuit as the traditional three-phase three-phase three-phase series series thyristor alternating-current conversion method. Separate control, triggering a pair of thyristors in the positive group and the negative group simultaneously for each heavy circuit, so that the output terminal of the heavy circuit is connected with the input of one phase of the heavy circuit, and after a time interval related to the expected output frequency. The next time it is triggered, the heavy output terminal is connected to the input of the next phase. By continuously switching this connection relationship, the phase of the output voltage is continuously changed, thereby obtaining the effect of changing the overall output frequency. At the same time, by arranging the phase of the output voltage of each heavy circuit according to the needs, and adjusting the triggering time of each heavy thyristor, it can realize the output of AC power with a three-phase phase difference of 120° for use by three-phase motor loads. It has the advantages of low cost and high reliability.

The invention discloses a compound control based hybrid cascading seven-level active filter. The compound control based hybrid cascading seven-level active filter comprises an H-bridge hybrid cascading main circuit (3), a sampling circuit (4), a control circuit (5), and a pulse width modulation (PWM) and isolation drive circuit (6), wherein the ratio of the DC side voltages of two H-bridge units in the H-bridge hybrid cascading main circuit (3) is 1: 2, the control circuit (5) comprises a main power signal generation module (7), a power compensation signal generation module (8), and a compound control module (9), the main power signal generation module (7) generates a main control signal, the power compensation signal generation module (8) generates a power compensation signal, the compound control module (9) is used for generating a first control signal and a second control signal, and the PWM and isolation drive circuit (6) is used for generating a final switch tube drive signal. Compared with traditional isobaric cascading active filters, the compound control based hybrid cascading seven-level active filter can output more levels under the same number of units, so that effects of harmonic compensation are improved.