33results about How to "Realize four-quadrant operation" patented technology

The invention relates to a hybrid multi-level current transformation topology based on an H full-bridge subunit, wherein one end of an H bridge cascading module is connected with a positive direct-current bus, and the other end of a fully-controlled switch tube series connection module is connected with a negative direct-current bus; the fully-controlled switching tube series connection module is of an H bridge circuit structure consisting of four bridge arms with same structure, wherein a connection point between the first bridge arm and the third bridge arm and a connection point between the second bridge arm and the fourth bridge arm are used as output terminals and connected with an LC low-pass filter; and one end of the H bridge cascading module is connected with a connection inductor, and the other end of the connection inductor is connected with one end of the fully-controlled switching tube cascading module. The hybrid multi-level current transformation topology disclosed by the invention can be used as a single phase, can be also used for a three-phase alternating-current circuit sharing a direct-current bus and realizes four-quadrant operation.

The invention belongs to the field of control technology of brushless continuous current dynamo, and discloses a direct torque control method of a brushless continuous current dynamo. The method comprises the following steps: A. a preset torque is obtained according to the actual rotational speed and the command rotational speed of the dynamo; B. an estimating torque is obtained according to the rotor position and the three-phase current value of the input end of the dynamo; C. a first duty ratio is obtained according to the preset torque and the estimating torque, and is added with a second duty ratio related to the speed, and then a final duty ratio is obtained; D. the state of a switch tube is selected according to the final duty ratio, the rotor position and the plus-minus of the preset torque; E. an inverter is controlled to drive the dynamo to rotate according to the state of the switch tube. The invention also discloses a direct torque control device of the brushless continuous current dynamo. According to the invention, a linear counter emf form factor is adopted to calculate the torque, and control period is shortened; PWM (pulse width modulation) technology is combined, and a torque hysteresis regulator is improved, so that torque pulsation inhibition when the inductance of the dynamo is small is realized, and four-quadrant operation of the brushless continuous current dynamo is also realized.

The invention discloses an instantaneous torque control method of a brushless direct-current motor based on direct-current control. The control method comprises the following steps: a two-phase current value of the motor is detected by using a current sensor and a current value of another phase is calculated; a rotor position of the motor is detected by using a position sensor; the instantaneous torque required at present is obtained through calculation and comparison; an optimal reference current is obtained through a torque coefficient reciprocal database in combination with the rotor position; the optimal reference current is compared with a current obtained through the selection so as to obtain a duty ratio D1; the duty ratio D1 is added to a duty ratio D2 corresponding to a counter potential of which the rotate speed is in direct ratio so as to obtain a final duty ratio D; the final duty ratio D, a rotate speed instruction, the negative and positive of the optimal reference current and rotor position information are input into a switch state checking table together; a corresponding switch mode is selected to drive the brushless direct-current motor to operate, thus the four-quadrant operation of the brushless direct-current motor is realized, the control to the rotate speed of the motor and the instantaneous torque is realized, and the purpose of suppressing an electromagnetic torque pulsation of the brushless direct-current motor is achieved.

The invention relates to a novel monopole inverting circuit capable of boosting voltage, and topology is shown in an attached figure. Besides a three-phase switch bridge (B) of the conventional voltage type inverter, the circuit is additionally provided with a tightly coupled inductor consisting of inductors (L1, L2), a capacitor (C), an interdiction diode (D) and a switch tube (T) for an energy feedback passage (can be removed if no energy is needed to feedback). The voltage boosting control mode of the circuit to an inverter direct current bus uses the state of the through zero vector of the upper and lower switch tubes emitted by the three-phase inverter bridge during zero vector to adjust the action time so as to realize the controllable promotion of direct current bus voltage of the input side of the inverter. The inductors (L1 and L2) are tightly coupled, when the inductors are in a state of through zero vector, the inverter is directly communicated, and a DC voltage source (Vs) charges a couple inductor (L1); and when the inductors are in a state of non-through zero vector, the inductors release energy to supply power to the direct current bus of the inverter (B); the voltage of the direct current bus of the inverter is obtained by lapping the voltage of the inductor (L2) and the voltage of the capacitor (C) so as to enable the voltage of the direct current bus of the inverter to be improved, so that the inverter voltage is boosted.

The invention discloses an SVPWM strategy based on the power supply topology of double three-level inverters. According to the strategy, a gating signal of each switch device is obtained fast according to three-phase referential voltage signals, two inverters work alternately in each fundamental wave period, the average zero sequence voltage generated by the two inverters is zero in each switch period, and the midpoint electric potential is balanced based on the voltage signals of two direct-current-side capacitors. The SVPWM strategy based on the power supply topology of the double three-level inverters has the advantages that the modulation strategy is simple and fast, and coordinate change and complicated sector judgment and table look-up are not needed; the two inverters work alternately, the switching frequency of the switch devices is reduced by half, and the loss of the switch devices is reduced; after the average zero sequence voltage is eliminated, power supply of the two inverters can be achieved by only one direct current power source, the topology structure can be effectively simplified, cost can be reduced, and four-quadrant operation of a motor is facilitated.

The invention discloses a flywheel motor adopting a no-cross one-range winding, relating to the technical field of the motor and solving the problems that the existing flywheel motor has complex structure, large power consumption and poor moment stability. A rotor in the invention is a wheel body of a flywheel; an outer rotor iron core and an inner rotor iron core of the rotor are fixedly connected on a torque output shaft; a no-iron core frame type stator is fixed between the inner rotor iron core and the outer rotor iron core; permanent magnets are fixed on the inner rotor iron core or the outer rotor iron core and the side wall corresponding to the no-iron core frame type stator; a winding of the no-iron core frame type stator consists of a plurality of groups of planar coils which areevenly distributed and fixed on the side wall of the frame; two adjacent groups of planar coils have an electric angle of 240 degrees, and have no cross; three position sensors are respectively fixedon the frames at the central positions of three adjacent groups of planar coils; and the ratio of the number Z of the planar coils and the number 2p of poles of the permanent magnets is 3 / 4. The flywheel motor is applicable to the technical fields of posture control of the satellites and control moment gyros and the like.

The invention provides an alternating-current excitation synchronous machine control device and method, and belongs to the field of electromechanical control engineering. According to the method, alternating-current excitation is conducted on a wound-type motor rotor winding through a variable-frequency controller, excitation efficiency is improved by controlling the excitation current of the motor through a rotor, the capacity of the system is decreased to be twenty percent or lower that of the motor, the capacity of the variable-frequency controller is greatly decreased, and device cost is greatly reduced. Active power of the motor running is provided by a stator winding through a power grid, the power factor on the stator side can be controlled to be 1, the speed regulation system is made more reasonable and more efficient through excitation control, and four-quadrant operation is achieved.

The invention discloses a high-power brushless double-fed motor three-level bidirectional frequency conversion speed regulation system, which is characterized in that the system is composed of a brushless double-fed motor and a three-level dual PWM AC speed regulation system. The dual-PWM AC speed regulation system includes a brushless doubly-fed motor three-level PWM rectifier unit and a brushless doubly-fed motor three-level inverter unit. In the main circuit structure of the three-level dual-PWM AC speed regulation system of the present invention, four power devices are connected in series for each phase bridge arm. The three-level PWM rectifier can realize two-way flow of energy, improve energy recovery rate, and reduce energy loss of motor AC speed control system. It is suitable for high-voltage and high-power motor drive occasions.

The invention discloses a high-voltage and large-power wind power generation system and a control method thereof. The high-voltage and large-power wind power generation system comprises a multi-phase permanent-magnet direct-drive wind power generator, 3n three-phase full-control rectification bridges and an H-bridge cascaded multilevel inverter, wherein the multi-phase and large-power permanent-magnet direct-drive wind power generator is provided with 9n phase outputs, n is a positive integer, each three phases form a winding, the 9n phase outputs jointly form 3n windings, each winding is connected with a DC side of each sub-module of the H-bridge cascaded multilevel inverter after being converted by one of the three-phase full-control rectification bridges, and an AC output end of the H-bridge cascade multilevel inverter is connected with a three-phase power grid. The three-phase full-control rectification bridges employ maximum power tracking control to achieve the output of a unit power factor of the wind power generator; and the H-bridge cascaded multilevel inverter is used for achieving high-voltage access, and an AC side is directly connected with a 35kV alternating current. By the high-voltage and large-power wind power generation system, the low-voltage and large-power permanent-magnet direct-drive wind power generation system can be directly connected with a high-voltage power transmission system by a converter, a boost transformer is omitted, and the cost is reduced.

The invention provides a four-quadrant control device and a four-quadrant control method for an electric steering engine. A signal conditioning circuit is used for performing voltage transformation, filtering, clipping processing on a given signal of the deflection angle of a control plane and then sending the given signal into a controller DSP (Digital Signal Processor) through AD (Analog-Digital) conversion; the DSP is used for outputting a digital control signal; after digital isolation, the digital control signal is sent to a driving circuit and converted into a success rate control signal; and a main power circuit is controlled so as to control a brushless direct-current motor to work; the brushless direct-current motor drives the control plane to derivate so as to follow the given signal of the deflection angle of the control plane through a transmission gear set; the bus bar current of the brushless direct-current motor is sampled through a current sensor and then fed back to the DSP, and an angle sensor connected with the transmission gear set feeds back the current deflection angle of the control plane in real time which is sent to the DSP. According to the four-quadrant control device and the four-quadrant control method for the electric steering engine, the frequency response of a brushless direct-current electric steering engine is effectively quickened, and the antijamming capacity of the system is improved.

The invention relates to alternating-current to direct-current conversion of electric energy, discloses a four-quadrant multilevel current-source converter with a main circuit based on a thyristor and belongs to improvement to the fact that reactive power compensation is needed to be performed additionally caused by the fact that phase current is restricted and phase voltage is delayed due to a phase shift range of a trigger angle ranging from 0 to 180 when two groups of three-phase bridge-paralleled twelve-pulse thyristor circuits are utilized in high-power places. The converter is characterized in that a paralleling reactor in the topology is replaced by a multilevel injection circuit to enable each group of the three-phase bridges to output stepped multilevel pulse direct current and provide zero-current phase-commutation conditions for the thyristor. The multilevel injection circuit consists of multiple units with the same structure, each unit consists of two components with inverse resistant characteristics and a reactor, and cathodes or anodes of the components are connected with a terminal of the reactor to enable each group to structurally be a three-port unit. Consequently, the multilevel injection circuit and the main circuit are coordinated for controlling to provide the zero-current phase-commutation conditions for a main bridge thyristor, so that controlled turn-off of the thyristor is realized, and the whole circuit can possess four-quadrant operating capability.

The invention discloses a method and a system for controlling a network-side converter. A power grid voltage is taken as a differential of a virtual flux linkage by using a virtual power grid flux linkage angle observer; a virtual power grid flux linkage is observed by an observing method similar to that of the flux linkage of an alternating current motor for replacing the power grid voltage to serve as an oriented vector; and a power grid orientation angle is obtained by using the virtual power grid flux linkage angle observer. By the method and the system, partial parameters are calculated by software by using the virtual power grid flux linkage angle observer, a control strategy is decoupled by using a vector oriented by a d axis virtual power grid flux linkage, and four quadrant operation is realized; and related electricity parameters are acquired by the virtual power grid flux linkage angle observer, and a virtual power grid flux linkage angle is observed by a software algorithm. The observation accuracy of a virtual power grid flux linkage observer can be improved by adding initial flux linkage estimation, and the impact of a starting current can be effectively restrained, so that the conventional method for using a hardware voltage sensor is replaced. By the method and the system, the reliability and anti-interference performance of the network-side converter are improved, and hardware cost is lowered.

The invention discloses a balance ship. The balance ship comprises a cabin and a ship body, and further comprises a flywheel energy storage system arranged in the cabin, and a gyroscope; the flywheel energy storage system comprises a power transmission device, an electric power conversion device and an accumulator; the gyroscope is connected with the power transmission device; and the power transmission device is connected with the accumulator through the electric power conversion device. In the navigation process, as the flywheel energy storage system drives the gyroscope to rotate to achieve self-balance function, the autonomous balance of the ship can be guaranteed, the life and property safety of people is guaranteed, even if the ship generates navigation accidents or meets with the bad weather, the self-balance of the ship can be guaranteed, and the ship is not dumped; and in daily navigation process, the flywheel energy storage system provides energy to the accumulator to guarantee daily power supply of the ship.

The invention relates to a dynamic voltage adjusting device and method based on a modular multi-level inverter, and the device comprises a main circuit and a DSP control circuit. The main circuit comprises an energy storage unit, an MMC inversion unit, and a capacitor coupling unit. The energy storage unit provides energy for a compensator, and the MMC inversion unit is provided with a modular multi-level structure. A single-phase topological structure comprises an upper bridge arm and a lower bridge arm. Each bridge arm comprises a plurality of submodules which are in series connection and have the same structure, and one bridge arm reactor. The voltage waveform which meets the requirements is outputted through controlling the on / off of a switching device in each submodule, and the capacitor coupling unit is used for inhibiting the impact on a load from the voltage fluctuation of a system. Compared with the prior art, the device is low in switching frequency, is low in switching loss, is small in output harmonic, and is good in application prospect.

The invention discloses a mine main ventilation fan high-voltage inverter device with energy feedback. The mine main ventilation fan high-voltage inverter device comprises a pulse-width modulation (PWM) rectifier, a current source type high-voltage inverter and a PWM inverter, the input end and the output end of the current source type high-voltage inverter are respectively connected with the PWM rectifier and the PWM inverter, the output end of the PWM inverter is connected with a main ventilation fan, and simultaneously alternating current power output by the PWM inverter is fed back to a power grid to achieve feedback of electric energy. Electric energy output by the power grid is converted by a special power supply to supply power for the PWM rectifier and the main ventilation fan M. The mine main ventilation fan high-voltage inverter device adjust the voltage of the PWM rectifier and the PWM inverter through PWM technology, accordingly removes an input transformator and an output transformator and achieves purposes of simplifying system structures and improving system operation efficiency and reliability.

The present invention discloses a single-stage non-isolated double-Cuk type inverter without an electrolytic capacitor. An anode of an input power supply is connected to one end of an input inductor, a cathode of the input power supply is connected to a collector of a fifth power switch tube and a collector of a sixth power switch tube of a second Cuk circuit, and the other end of the input inductor is connected to a collector of a first power switch tube, and a collector of a second power switch tube and one end of an input capacitor; the other end of the input capacitor is connected to an emitter of a fourth power switch tube and an emitter of a third power switch tube; and an emitter of the fifth power switch tube is connected to an emitter of the first power switch tube, a collector of the third power switch tube and one end of a filter inductor, the other end of the filter inductor is connected to one end of the filter capacitor and one end of a load, the other ends of the filter capacitor and the load are connected to an emitter of the sixth power switch tube, an emitter of the second power switch tube and a collector of the fourth power switch tube. The single-stage non-isolated double-Cuk type inverter disclosed by the present invention is simple in structure, quick in dynamic response and good in tracking performance, and has relatively strong inhibiting capacity for fluctuations of the power supply and the load.

The invention discloses a virtual synchronous generator control method and system of a matrix converter, and particularly belongs to the field of matrix converter control. The system comprises an alternating current source type power supply, an input filter, a matrix converter, an output filter, an alternating current bus, a virtual synchronous generator controller, an expected output current generator and a matrix converter controller. The control method is suitable for an alternating current source type micro-source and an energy storage system which adopt a matrix converter for grid connection, the matrix converter is used for connecting an alternating current source type power supply and a power grid, and energy provided by the alternating current source type power supply is used for implementing a virtual synchronous generator control strategy of the matrix converter. According to the method, a virtual synchronous generator control strategy is established by using a synchronous generator model; and the hysteresis controller is used for controlling the matrix converter, so that the grid-connected matrix converter can simulate droop characteristics of active power-frequency andreactive power-voltage of the synchronous generator, the grid-connected matrix converter has certain inertia and damping, and the stability of the system can be improved.

The present invention discloses a single-stage non-isolated double-Cuk type inverter without an electrolytic capacitor. An anode of an input power supply is connected to one end of an input inductor, a cathode of the input power supply is connected to a collector of a fifth power switch tube and a collector of a sixth power switch tube of a second Cuk circuit, and the other end of the input inductor is connected to a collector of a first power switch tube, and a collector of a second power switch tube and one end of an input capacitor; the other end of the input capacitor is connected to an emitter of a fourth power switch tube and an emitter of a third power switch tube; and an emitter of the fifth power switch tube is connected to an emitter of the first power switch tube, a collector of the third power switch tube and one end of a filter inductor, the other end of the filter inductor is connected to one end of the filter capacitor and one end of a load, the other ends of the filter capacitor and the load are connected to an emitter of the sixth power switch tube, an emitter of the second power switch tube and a collector of the fourth power switch tube. The single-stage non-isolated double-Cuk type inverter disclosed by the present invention is simple in structure, quick in dynamic response and good in tracking performance, and has relatively strong inhibiting capacity for fluctuations of the power supply and the load.

The invention provides a four-quadrant control device and a four-quadrant control method for an electric steering engine. A signal conditioning circuit is used for performing voltage transformation, filtering, clipping processing on a given signal of the deflection angle of a control plane and then sending the given signal into a controller DSP (Digital Signal Processor) through AD (Analog-Digital) conversion; the DSP is used for outputting a digital control signal; after digital isolation, the digital control signal is sent to a driving circuit and converted into a success rate control signal; and a main power circuit is controlled so as to control a brushless direct-current motor to work; the brushless direct-current motor drives the control plane to derivate so as to follow the given signal of the deflection angle of the control plane through a transmission gear set; the bus bar current of the brushless direct-current motor is sampled through a current sensor and then fed back to the DSP, and an angle sensor connected with the transmission gear set feeds back the current deflection angle of the control plane in real time which is sent to the DSP. According to the four-quadrant control device and the four-quadrant control method for the electric steering engine, the frequency response of a brushless direct-current electric steering engine is effectively quickened, and the antijamming capacity of the system is improved.

The invention relates to a novel monopole inverting circuit capable of boosting voltage, and topology is shown in an attached figure. Besides a three-phase switch bridge (B) of the conventional voltage type inverter, the circuit is additionally provided with a tightly coupled inductor consisting of inductors (L1, L2), a capacitor (C), an interdiction diode (D) and a switch tube (T) for an energy feedback passage (can be removed if no energy is needed to feedback). The voltage boosting control mode of the circuit to an inverter direct current bus uses the state of the through zero vector of the upper and lower switch tubes emitted by the three-phase inverter bridge during zero vector to adjust the action time so as to realize the controllable promotion of direct current bus voltage of the input side of the inverter. The inductors (L1 and L2) are tightly coupled, when the inductors are in a state of through zero vector, the inverter is directly communicated, and a DC voltage source (Vs)charges a couple inductor (L1); and when the inductors are in a state of non-through zero vector, the inductors release energy to supply power to the direct current bus of the inverter (B); the voltage of the direct current bus of the inverter is obtained by lapping the voltage of the inductor (L2) and the voltage of the capacitor (C) so as to enable the voltage of the direct current bus of the inverter to be improved, so that the inverter voltage is boosted. The novel monopole inverting circuit capable of boosting voltage only uses a first stage transform circuit, smartly applies through zero vector which is not allowed by the traditional inverter so as to improve the DC busbar voltage of the inverter, realizes the adjustment to the busbar voltage, suits to the variational occasions which need to boost and invert or larger input voltage, and overcomes the shortage of the traditional voltage type inverter, cares nothing for the through caused by the electromagnetic interference and does not need to be inserted into a dead zone.

The invention discloses a high-power brushless doubly-fed machine three-level bidirectional variable-frequency speed regulation system. The system is characterized in that the system consists of a brushless doubly-fed motor and a three-level dual-PWM alternating-current speed regulation system; and the three-level dual-PWM alternating current speed regulation system includes a brushless doubly-fed motor three-level PWM rectification unit and a brushless doubly-fed motor three-level inverter unit. According to the high-power brushless doubly-fed machine three-level bidirectional variable-frequency speed control system of the invention, in the main circuit structure of the three-level dual-PWM alternating current speed regulation system, as for each phase of bridge arm, four power devices are connected in series, and therefore, each power device bears lower voltage compared with a two-level main circuit structure; an rectification end adopts a three-level PWM rectifier, so that directional energy flow can be realized, and the recovery rate of energy can be improved, and the energy loss of the motor alternating-current speed regulation system can be decreased. The high-power brushless doubly-fed machine three-level bidirectional variable-frequency speed regulation system is suitable for high-voltage high-power motor driving application.

The invention discloses an instantaneous torque control method of a brushless direct-current motor based on direct-current control. The control method comprises the following steps: a two-phase current value of the motor is detected by using a current sensor and a current value of another phase is calculated; a rotor position of the motor is detected by using a position sensor; the instantaneous torque required at present is obtained through calculation and comparison; an optimal reference current is obtained through a torque coefficient reciprocal database in combination with the rotor position; the optimal reference current is compared with a current obtained through the selection so as to obtain a duty ratio D1; the duty ratio D1 is added to a duty ratio D2 corresponding to a counter potential of which the rotate speed is in direct ratio so as to obtain a final duty ratio D; the final duty ratio D, a rotate speed instruction, the negative and positive of the optimal reference current and rotor position information are input into a switch state checking table together; a corresponding switch mode is selected to drive the brushless direct-current motor to operate, thus the four-quadrant operation of the brushless direct-current motor is realized, the control to the rotate speed of the motor and the instantaneous torque is realized, and the purpose of suppressing an electromagnetic torque pulsation of the brushless direct-current motor is achieved.

The invention relates to multi-stage inverter equipment for grid-connected compensation of a power distribution network, which comprises a plurality of inverters which are cascaded in sequence and a plurality of switching devices which are respectively used for controlling the input and output of each inverter, wherein the number of the switching devices is consistent with that of the inverters, and each switching device is respectively connected with the corresponding inverter. Compared with the prior art, multiple groups of inverter packets can be combined into a cascaded inverter mode by using the multi-path switcher, and the cascaded inverter mode has the function of giving appropriate compensation capability when a power distribution network needs higher peak compensation, and can beused for a compensation field with a severe harmonic loop.

The invention relates to a control system and control method of an indirect space vector matrix converter based on a 60-degree coordinate system. The control system includes a bilateral switch matrix circuit which consists of power devices having a bidirectional blocking capability and an automatic turning-off capability, a 3*3 switch array is formed, each output phase is connected with a three-phase input end through a bilateral switch, and a three-phase alternating current power supply is connected with the bilateral switch matrix circuit through an input filter with damping resistance. The control method includes the steps of: 1. calculating virtual direct current side voltage and virtual direct current side current in a virtual alternating current-direct current-alternating current structure; 2. determining an output voltage duty ratio and an output current duty ratio; 3. determining vector action time and a vector distribution condition; and 4. determining switching-on and switching-off of switching tubes. The control system of the indirect space vector matrix converter based on the 60-degree coordinate system is a stable, efficient and reliable electric power conversion device, and has the advantages of wide output frequency modulation and amplitude modulation, sinusoidal input and output waveforms, large degree of freedom of control, bidirectional flow of energy, fast dynamic response and the like.

The present invention is an AC excitation synchronous motor control device and method, which belongs to the field of electromechanical control engineering. The present invention uses a variable frequency controller to perform AC excitation on the rotor winding of a wound motor, and controls the excitation current of the motor through the rotor to improve the excitation efficiency. The capacity of the system is reduced to less than 20% of the motor capacity, which greatly reduces the capacity of the frequency conversion controller and greatly reduces the equipment cost. The active power of the motor operation is provided by the stator winding through the power grid, and can be controlled to the stator side power factor of 1. Excitation control makes the speed control system more reasonable and efficient, enabling four-quadrant operation.

The invention discloses an SVPWM strategy based on the power supply topology of double three-level inverters. According to the strategy, a gating signal of each switch device is obtained fast according to three-phase referential voltage signals, two inverters work alternately in each fundamental wave period, the average zero sequence voltage generated by the two inverters is zero in each switch period, and the midpoint electric potential is balanced based on the voltage signals of two direct-current-side capacitors. The SVPWM strategy based on the power supply topology of the double three-level inverters has the advantages that the modulation strategy is simple and fast, and coordinate change and complicated sector judgment and table look-up are not needed; the two inverters work alternately, the switching frequency of the switch devices is reduced by half, and the loss of the switch devices is reduced; after the average zero sequence voltage is eliminated, power supply of the two inverters can be achieved by only one direct current power source, the topology structure can be effectively simplified, cost can be reduced, and four-quadrant operation of a motor is facilitated.

The invention discloses a dynamic braking control system of a direct current motor, which comprises direct current motor, a direct current constant voltage source, a torque and rotating speed sensor, a PLC (programmable logic controller) processor, a chopper control board, an IGBT (insulated gate bipolar transistor) power component and a braking control resistance module, wherein a voltage output of the direct current constant voltage source is connected with a voltage input of the direct current motor via the braking control resistance module; the direct current motor is connected with the torque and rotating speed sensor; an output of the torque and rotating speed sensor is connected with an input of the PLC processor; an output of the PLC processor is connected with an input of the chopper control board; an output of the chopper control board is connected with an input of the IGBT power component; and the IGBT power component is in parallel connection with the braking control resistance module. According to the system, the braking control resistance module is cut off by the PLC processor under different conditions, so that rotating speed and torque outputs of the direct current motor change to achieve dynamic braking.

The invention relates to the technical field of power electronics, and particularly relates to a cascaded 24-pulse-wave converter topology. The cascaded 24-pulse-wave converter topology comprises a double-Y pulse generator, a phase-shifting transformer set, a four-quadrant 24-pulse-wave converter set and a resistance-inductance load, wherein the double-Y pulse generator is connected to one end ofthe phase-shifting transformer set, the other end of the phase-shifting transformer set is connected with one end of the four-quadrant 24-pulse-wave converter set, and the other end of the four-quadrant 24-pulse-wave converter set is connected with the resistance-inductance load. The device can effectively suppress circulating current, omit an additional circulating current reactor, save the costand reduce the size. In addition, once converter fault circulating current is out of control, only the converter connected with the fault converter in parallel is influenced, and other converters arenot influenced, so that other converters are protected to the maximum extent; four-quadrant operation can be realized; the connection mode of the transformer and the converters enables the network side and the transformer to be balanced in load, the transformer is small in load, and circulating current cannot flow through two secondary sides of the same transformer simultaneously.