4848 results about "Dc voltage" patented technology

The invention discloses a DC voltage divider parameter anomaly detection method based on harmonic characteristics, and the method comprises the steps: deploying an isolation type voltage sensor at a bus of a DC power transmission system, carrying out the voltage sampling through combining with an ADC, carrying out the data buffering and preprocessing, extracting a fundamental wave component and a target harmonic component through the fast Fourier transform, and calculating the harmonic distortion rate. And constructing a low-voltage arm capacitance and harmonic distortion rate model based on a voltage divider secondary circuit equivalent circuit and an energy distribution principle, and calibrating the low-voltage arm capacitance and harmonic distortion rate model. And designing a multi-objective optimization scheduling algorithm based on energy storage capacity and capacitance characteristics, and realizing dynamic power distribution and harmonic suppression of the system. And after abnormal triggering, the system automatically loads a capacitance compensation coefficient, adaptively adjusts algorithm parameters in combination with a measurement loop PI control link, reduces a harmonic amplification effect, and ensures that a measurement error is within an acceptable range. Harmonic monitoring precision and capacitance compensation optimization capability of the direct-current power transmission system are effectively improved, and stable operation of the system is guaranteed.

The invention relates to a dual three-phase permanent magnet synchronous generator rectification system and a direct current voltage stabilization control method thereof. Comprising a dual three-phase permanent magnet synchronous generator, a VSD decoupling converter, a load current observer, a dynamic load feed-forward compensator, a voltage closed-loop controller, a dead-beat predictive current controller, a maximum four-vector SVPWM modulation module and a six-phase rectifier. The double-three-phase topological structure adopted by the invention has the advantages of multiple control degrees of freedom, high reliability and the like. A dynamic load feed-forward compensator is constructed to perform dynamic feed-forward compensation on quadrature-axis current of the motor, so that the recovery time of bus voltage is shortened, and the voltage fluctuation amplitude is reduced; the designed dead-beat predictive current controller optimizes the dynamic characteristics of a current loop, improves the torque tracking performance of the motor, and further improves the voltage stabilization regulation capability of the system. The designed load current observer realizes the analysis redundancy of current detection and improves the reliability of the system.

The invention discloses a fault ride-through test method for an offshore wind power flexible direct output system, and the method comprises the steps: building a fault equivalent circuit of the offshore wind power flexible direct output system, analyzing the operation characteristics of an AC power grid side under a low-voltage fault, and determining the incidence relation between the DC side excess energy and the power grid voltage drop; establishing a model representing each component in the fault equivalent circuit, wherein the components at least comprise a machine-side converter, a grid-side converter, a direct-current capacitor and an unloading resistor; when a low-voltage fault of an alternating-current power grid side is detected, executing the following cooperative control based on the model: synchronously starting unloading resistance control and reactive power support control, wherein an unloading resistor dissipates excess energy of a direct-current side through a direct-current chopper; the grid-side converter injects a capacitive reactive current which is deeply matched with the voltage drop of the power grid so as to improve the voltage of a grid-connected point; and if the direct-current voltage continuously exceeds the preset threshold value, starting power prompt drop control, and reducing the output power of the unit according to a gradient until the system recovers to be stable.

A control system for an AC-DC converter includes a mixed-signal power controller and first and second gate drivers. The controller has a digital module and an analog module. The analog module has a current sensor generating a current sense voltage based on a sensed switch current. The digital module has a DC voltage sensor generating a DC sense voltage based on a DC bus voltage, and an AC voltage sensor generating an AC sense voltage and a binary polarity signal based on the AC voltage. The digital module induces the first gate driver to output first and second control signals for controlling a high-side switch and a low-side switch of a current shaping half-bridge based on first and second clock signals and the comparator voltage, such that an inductor current flowing through an inductor is proportional to a current command value.

The invention discloses a control method and system for improving SVG (Static Var Generator) disturbance signal generation precision, relates to the technical field of SVG disturbance signal generation, and solves the technical problem that a current disturbance signal generated by an SVG is difficult to meet the dynamic precision requirement required by multi-frequency impedance measurement. According to the technical scheme, disturbance signal attenuation caused by SVG direct-current voltage control is calculated through an observer, after phase compensation, the disturbance signal attenuation and a direct-current voltage given value are superposed to serve as outer loop input of a voltage controller, and the outer loop input is subtracted from direct-current voltage feedback; an outer ring output is obtained through a voltage controller of an outer ring and superposed with an instruction current disturbance signal to serve as an inner ring input of a current controller, and SVG operation is controlled through a current inner ring controller and a PWM modulation instruction. The influence of a direct-current voltage outer loop on actual current disturbance signals is remarkably reduced, and the SVG can still output accurate actual current disturbance signals when instruction current disturbance signals of all frequencies are injected into the SVG.

The invention discloses a direct-current voltage self-balancing method in the high-low voltage ride-through process of a high-voltage frequency converter, and the method comprises the steps: obtaining an electric signal of the high-voltage frequency converter, calculating the Lyapunov index of a system in real time based on the electric signal, so as to quantify the chaotic state of the system, and generating a real-time Lyapunov index sequence; according to the real-time Lyapunov index sequence, the gradient of the real-time Lyapunov index sequence relative to a preset system state variable is determined, and a Lyapunov gradient field is constructed; using the Lyapunov gradient field to generate a basic control quantity through nonlinear mapping; and converting the basic control quantity into a pulse width modulation parameter to form a PWM control signal set to be applied to the high-voltage frequency converter. According to the method, the Lyapunov gradient field is constructed to provide prospective direction guidance for control, so that the chaotic oscillation is quickly suppressed, and the dynamic stability of the system under power grid disturbance is remarkably improved.

The invention discloses a cooperative ride-through control method for a new energy flexible direct current transmission system under a receiving end fault, and relates to the technical field of flexible direct current transmission, and the method comprises the steps: periodically collecting the grid-connected point voltage of a receiving end converter station, an output active current reference value, and the real-time data of the online impedance estimation of a converter station side; calculating the minimum possible true values of the converter station side equivalent reactance and the short circuit point voltage; calculating a reactive current reference value and an active current reference value of the flexible DC receiving end converter station after the fault occurs; calculating the input time of the energy consumption resistor; the reactive current reference value, the active current reference value and the energy consumption resistor input moment are sent to a receiving end converter station; and when the receiving-end converter station detects that the voltage drop of the grid-connected point meets the low-voltage crossing starting condition, the receiving-end converter station enters a low-voltage crossing control mode and starts control, and the receiving-end converter station performs corresponding adjustment. By the adoption of the method, the rising speed of the direct-current voltage is reduced fundamentally, the input time or the input frequency of an energy consumption device is reduced, and the economical efficiency of fault ride-through is improved.

The invention provides an array substrate and a display device, and the array substrate comprises a substrate; the gate insulating layer is arranged on the substrate; the data line is arranged on the gate insulating layer; the first passivation layer is arranged on the gate insulation layer and covers the data line; the first shielding electrode is arranged on the first passivation layer, and the first shielding electrode is connected with the direct-current voltage signal output end; the second passivation layer is arranged on the first passivation layer and covers the first shielding electrode; the common electrode is arranged on the second passivation layer, and a part of the common electrode is overlapped with the data line and the first shielding electrode; the pixel electrode and the common electrode are arranged on the same layer or stacked, and the pixel electrode is insulated from the common electrode. The first shielding electrode is connected to the direct-current voltage signal, so that the data voltage signal on the data line does not affect the signal on the common electrode, coupling capacitance between the common electrode and the data line is avoided, and poor display of picture flicker is avoided.

A converter system, e.g., for vehicle-to-vehicle charging, includes galvanically-isolated modular first and second converters having the same maximum voltage rating, a direct current (DC) voltage bus interconnecting the converters, and an electronic controller. An input voltage to the DC bus is converted into an output voltage via switching control signals to the modular converters. The system's voltage rating may equal the maximum of the input and / or output voltage, or it may equal the maximum input voltage and be about 50-percent of the maximum output voltage. The maximum input and output voltages may be equal. When the voltage rating is about 50-percent of the maximum input voltage, capacitors may be connected in parallel with the modular converters on an input side thereof. Switching circuits may be connected to the bus to control the conversion of the input voltage via switching control signals.

Sensing circuitry for an implantable stimulator device is disclosed. The sensing circuitry includes a downselector with switching networks used to couple selected electrode nodes and / or DC voltages to one or more sense amps. The switching networks comprise high-voltage devices that are controlled in accordance with a high-voltage power supply voltage VH. VH may be generated by a boost circuit, and may be set to the higher of a boosted voltage and a compliance voltage that powers the stimulation circuitry. The switching networks include three switches, some of which may comprise transfer gates. The downselector can be controlled to couple one or more electrodes nodes to a particular sense amp during sensing durations. The downselector can also be controlled during stimulation durations to couple one or more electrodes nodes together, thus supplementing operation of the stimulation circuitry.

Voltage command values are set according to voltage fluctuations of a plurality of power supply sources, and one of outputs from a plurality of power supply circuits which output DC voltages obtained by performing conversion according to the voltage command values is supplied to a power conversion circuit as control power so that the system can be continuously operated even at the time of an abnormality due to a device failure and a power outage, and control power consumption can be suppressed in the case of voltage fluctuations of the power supply sources.

The present invention provides a topology, method and system for bi-directional power conversion of excitation power supply for power battery testing, wherein the topology comprises a three-phase PWM (pulse width modulation) converter, a high-frequency isolation three-level LLC (logical link control) resonant converter and a DC-DC (direct current) converter forming a topology structure for a three-stage power conversion; an input end of the three-phase PWM converter is connected to a power grid side; the high-frequency isolation three-level LLC resonant converter is connected between the three-phase PWM converter and the DC-DC converter in series and is configured for realizing bi-directional DC voltage conversion and isolation, and to raise a busbar voltage between the high-frequency isolation three-level LLC resonant converter and the DC-DC converter; and, the DC-DC converter is configured to generate charging and discharging excitation currents for a power battery testing.

The invention discloses a fault processing method for an offshore wind power direct current parallel sending-out system through a DRU-MMC. The fault processing method comprises the steps that direct current energy consumption devices are arranged at direct current outlets of respective land MMC converter stations of a DRU-HVDC system and an MMC-HVDC system; when the alternating current power grid at the receiving end has an alternating current fault, the direct current energy consumption device is controlled to adopt a direct current voltage suppression strategy; when the DRU-HVDC system and the MMC-HVDC system respectively have direct current faults, different locking and circuit breaker disconnection time sequence control strategies are adopted, and in the direct current fault ride-through period, a direct current suppression strategy and a direct current voltage suppression strategy are controlled to be adopted by a direct current energy consumption device of the DRU-HVDC system. Therefore, the fault ride-through capability of the DRU-MMC direct current parallel sending-out system of the offshore wind power can be effectively improved, and stable operation of the system is ensured.

The invention discloses a control device and a control method of a radio frequency power supply and the radio frequency power supply. The control device comprises an adjusting module, a control module and a sampling module. The adjusting module is used for outputting a driving signal to a radio frequency input end of the power amplification module according to a reference radio frequency signal output by the signal generation module and a second bias voltage value output by the control module; the sampling module is used for collecting actual forward power output to the load by the power amplification module and actual reverse power reflected by the load; the control module is used for applying a direct-current voltage value smaller than the maximum input voltage value to the power supply end of the power amplification module according to the actual reverse power and the reverse power threshold value when the actual reverse power is larger than the reverse power threshold value, and adjusting a second bias voltage value according to the actual forward power and the forward power threshold value. When the load impedance changes, the radio frequency power supply can be effectively protected from being damaged by overlarge reverse power, continuous output of forward power can be maintained, and process interruption is avoided.

A direct-current conversion circuit, which is used for providing direct-current conversion between a first direct-current voltage and a second direct-current voltage is described. The direct-current conversion circuit comprises: a transformer, which comprises a primary-side winding and a secondary-side winding, wherein the primary-side winding comprises a center tap, and a first primary-side winding and a second primary-side winding, which are respectively connected to the center tap; a primary-side circuit, wherein a first side of the primary-side circuit is connected to the primary-side winding, a second side of the primary-side circuit comprises a first end, a second end, and a third end, and a first direct-current voltage is provided between the first end and the second end of the primary-side circuit; and a secondary-side circuit, wherein a first side of the secondary-side circuit is connected to the secondary side winding.

The invention discloses a weight coefficient-free model prediction control system and method for a permanent magnet synchronous motor, and particularly belongs to the field of permanent magnet synchronous motor control. The control system comprises a direct current voltage source, a three-phase converter, a permanent magnet synchronous motor, a rotating speed outer ring PI control module, an MTPA flux linkage calculation module and a model prediction control module. The control method comprises the following implementation steps: firstly, establishing a torque and flux linkage prediction model of the permanent magnet synchronous motor; then, a reference torque amplitude value and a reference flux linkage amplitude value are obtained through a rotating speed outer ring PI controller and a maximum torque per ampere (MTPA) calculation module respectively; secondly, constructing an independent torque cost function and a flux linkage cost function according to the torque error and the flux linkage error, and forming a cascade form; evaluating the switching states by using a cost function, selecting two vectors from the eight switching states of the converter by using the independent cost function of the torque (or flux linkage), and selecting an optimal vector from the two vectors by using the independent cost function of the flux linkage (or torque); and finally, the execution sequence of the torque and flux linkage cost function is alternated in each subsequent period. Compared with the prior art, the method avoids complex weight coefficient design through a cost function cascading mode, alternates the execution sequence of the cost functions in each period, dynamically balances the weights of the two control targets, and reduces the number of calculation times.

The invention relates to the technical field of power system control, in particular to a direct-current capacitor self-synchronizing grid-connected control strategy method, system, equipment and medium, a direct-current capacitor energy dynamic model is established based on an actual energy balance relation, a direct-current voltage signal is acquired in real time, and a synchronous compensation signal is calculated based on the acquired direct-current voltage signal; performing phase compensation and gain adjustment on the synchronous compensation signal through a correction link based on the calculated synchronous compensation signal, adjusting the internal frequency of the inverter based on the synchronous compensation signal after phase compensation and gain adjustment, controlling the DC voltage through the internal frequency of the inverter, and establishing a self-synchronization control model; and based on the self-synchronization control model, establishing an adaptive control algorithm, generating a damping coefficient and a virtual inertia coefficient through the adaptive control algorithm, and dynamically adjusting control parameters according to the damping coefficient and the virtual inertia coefficient.

The invention discloses a method and a device for tracing a commutation failure fault of a high-voltage direct-current power transmission system, and the method comprises the steps: taking three electrical quantity signals, namely an alternating-current voltage, a direct-current current and a direct-current voltage, of an inversion side of the high-voltage direct-current power transmission system as source data when the commutation failure occurs; extracting an optimal fault feature of the source data by adopting a fault feature extraction model and a feature screening algorithm based on feature density; and finally, in combination with a commutation fault detection model and the optimal fault characteristics, obtaining a fault type causing commutation failure of the high-voltage direct-current power transmission system. Through the above design, fault tracing of the commutation failure can be realized, and in the tracing process, the optimal fault features are extracted by using the machine learning model and the feature screening algorithm based on the feature density, so that interference of human subjective experience on feature extraction can be reduced, and the effectiveness of fault tracing is improved; therefore, the method is very suitable for large-scale application and popularization.

The invention relates to the technical field of battery modeling and photovoltaic energy storage systems, and discloses a self-adaptive battery modeling method for direct current bus voltage support of an optical storage system. The method comprises the following steps: establishing a basic model comprising a direct-current voltage source, an ohmic internal resistor and an RC polarization network; the voltage drop depth is obtained by monitoring the voltage of the direct-current bus in real time and used for correcting the polarization resistance; and performing differential operation on the voltage to obtain a change rate so as to adjust the polarization capacitance. And dynamically optimizing the battery model by combining correction results of the two, and realizing adaptive updating of model parameters. And applying the optimization model to the optical storage integrated grid-connected system. The adaptability of the battery model to the dynamic working condition is improved.

A control device includes a modulation rate calculator configured to calculate a modulation rate based on a DC voltage on a DC side an, a limiter configured to update a DC voltage command lower bound limiter based on the lower bound limiter operation value; a maximum power point tracking controller configured to calculate a first DC voltage command value and determine a second DC voltage command value based on the calculated first DC voltage command value and the DC voltage command lower bound limiter set to the limiter, and an inverter controller configured to control an inverter of the power conversion system based on the second DC voltage command value.

The invention belongs to the field of new energy, and particularly discloses a direct-current bus voltage control method and system of a flywheel energy storage system. Comprising the following steps: if DC bus voltage is in a normal range, DC voltage forms a q-axis current reference signal after being adjusted by a PI controller, the q-axis current reference signal generates a q-axis voltage instruction signal after being adjusted by a current control loop PI, and a dq-axis voltage instruction value is generated through decoupling; if the current control loop slightly deviates from the normal range, parameters of a PI controller are adjusted, so that an integration link plays a leading role in control output, a virtual impedance link connected to the current control loop in parallel is adjusted, and a dq-axis voltage instruction value is generated; and if the voltage is seriously deviated from the normal range, a grid-side power signal is fed forward to a machine-side direct-current voltage control loop, virtual resistance in a virtual impedance link is adjusted, and a dq-axis voltage instruction value is generated. According to the invention, the control mode is automatically switched according to different conditions of the DC bus voltage by adopting a threshold-grading regulation and control strategy, and the adaptability to large disturbance is improved while the steady-state precision of the system is maintained.

The invention discloses a hybrid direct current transmission power coordination control device and a control method and equipment thereof, and relates to the technical field of offshore power generation, and the hybrid direct current transmission power coordination control device comprises a diode rectifier unit and a first modular multilevel converter which are connected with an offshore wind plant, the sending-end converter station is used for converting alternating current generated by an offshore wind plant into direct current and outputting the direct current; the second modularized multi-level current converter is connected with the diode rectifier unit and the land power grid and is used for restoring the direct current into the alternating current and transmitting the alternating current to the land power grid; and the control module is connected with the first modular multilevel converter and is used for controlling the DC voltage of the first modular multilevel converter based on the fluctuation power according to the transfer relation between the active power and the DC voltage of the sending end converter station, so that the higher requirement of the rated capacity of the MMC in the related technology is met, and the reliability of the MMC is improved. And the engineering construction cost is increased.

The invention provides a wide-voltage intelligent control large-current contactor. Comprising a wide voltage control module which is composed of a rectifier bridge, a voltage acquisition module, a single-chip microcomputer control system and a DCDC conversion module and is used for converting input AC / DC voltage into stable 24VDC output; the wide-current control module is used for controlling the coil to start, the contactor can be in a working state even if power failure occurs, the stability of a power grid is ensured, and the device can be applied to the fields of uninterruptible power supply control cabinets, photovoltaic energy storage, power grid distribution and the like.

Disclosed in the present invention are a control method and system capable of providing frequency support for a flexible interconnected power distribution network. The method comprises: using a permanent-magnet direct-drive wind turbine connected to a flexible interconnected power distribution network to provide frequency support, measuring a direct-current voltage of a grid-side converter of the wind turbine, calculating a per-unit value and the phase of the direct-current voltage, and calculating the amplitude of a modulation voltage; generating a trigger pulse signal; monitoring the rotation speed of a wind turbine rotor and the rotor position angle of a synchronous generator, and acquiring a per-unit value of optimal power; calculating an active power reference value; on the basis of active power control and current control, outputting a d-axis component and a q-axis component of a modulation voltage of a generator-side converter, and by means of rotating coordinate transformation, generating a three-phase modulation voltage in a stationary coordinate system; and generating a trigger pulse signal by means of a pulse width modulation stage. The present invention enables wind turbines to provide quick response for power distribution networks in a frequency support stage, and prevent rotation speed stalling and suppress secondary frequency drop in a rotation speed recovery stage, thereby improving the support capability of the wind turbines for power grids.

The invention relates to the technical field of automatic welding, and discloses a micro welding seam tracking method and system based on electromagnetic induction. According to the method, a high-frequency alternating magnetic field is applied to a welding seam area through an exciting coil in the micro electromagnetic sensing core; an induction coil in the electromagnetic sensing core is used for detecting magnetic field disturbance caused by geometric shape changes of the weld groove, and induction signals are obtained; processing the induction signal through a signal processing circuit integrated in the probe, namely converting the impedance change of the coil into a voltage signal, demodulating and filtering the voltage signal, and extracting a direct-current voltage signal corresponding to the deviation of the probe relative to the central position of the welding seam; the direct-current voltage signals serve as position feedback information to be output to a welding robot control system; and the movement track of the welding robot is adjusted in real time according to the position feedback information, and welding seam tracking and path deviation correction are achieved.

The invention discloses a global cooperative control method and system for unbalanced fault ride-through of a multi-terminal DC power grid, and the method comprises the steps: constructing a fault detection model based on the positive sequence voltage drop depth and the negative sequence voltage size of the AC side of each converter station, automatically judging an unbalanced fault, and carrying out the fault detection when the fault is detected. Calculating the maximum allowable active current based on a fault station unbalanced current control model to carry out current limiting control on the converter station; and carrying out output power adjustment on the DC voltage deviation of the non-fault station based on the non-fault station power cooperation model. Asymmetric fault ride-through is carried out by using a constrained and optimized current instruction generation algorithm, and the capacity of a converter is dynamically and accurately distributed and utilized in a limited manner, so that the voltage support capability of a fault alternating-current power grid is maximized, and globally optimized adaptive power distribution is realized; the power of the non-fault station is calculated and distributed in a centralized manner and is dynamically adjusted according to the real-time available capacity, so that the self-adaption and global optimization of the running state change of the power grid are realized, and the fault handling toughness and reliability of the power grid are improved.

The invention relates to an electric vehicle wireless charging system LPV-Hammerstein model identification method based on an alternating least square iteration strategy, and belongs to the technical field of power electronic system modeling and parameter identification. The method comprises the following steps: firstly, constructing an LPV-Hammerstein model structure based on a WPT system circuit topology and a working mechanism, and then collecting discrete data of a system input control signal U, an output DC voltage Vo and a scheduling variable Req; then, alternately fixing other parameters by adopting an alternate least square iterative algorithm, and converting a to-be-estimated parameter problem into a linear least square sub-problem to be solved; and when a convergence condition is satisfied, a final LPV-Hammerstein model parameter estimation result is obtained. According to the method, the common nonlinear and parameter change coupling characteristics in the wireless charging system of the electric vehicle can be effectively processed, a systematized and efficient way is provided for obtaining a high-precision system dynamic model, and the limitation that the system cannot be accurately described by a traditional linear model or a simple nonlinear model is overcome.

An inertia cooperative control method of an integrated optical storage alternating current and direct current hybrid micro-grid comprises the steps that firstly, according to static and dynamic power capacities of energy storage units in direct current sub-grids and allowed direct current voltage deviation, sub-grid equivalent virtual resistance and virtual capacitance are calculated; secondly, RC + R type parallel virtual impedance parameters are distributed according to the power proportion of each energy storage unit, and multi-energy-storage cooperative response power disturbance according to the capacity is achieved; then, a phase angle is generated based on the mapping relation between direct-current side voltage and frequency, an alternating-current voltage amplitude instruction is determined in combination with reactive power droop control and feeder impedance voltage drop compensation, and a dq-axis voltage instruction is generated through virtual impedance compensation; normalized three-phase modulation waves are obtained through voltage-current double closed-loop control and dq / abc coordinate transformation, and six paths of PWM signals are generated to drive an interconnection converter after the normalized three-phase modulation waves are compared with triangular carrier waves. The method does not need to depend on external communication, has the capabilities of autonomous inertia support, voltage and frequency coordinated regulation and reasonable multi-source power distribution, and improves the stability and dynamic response performance of the system under island operation.

A power conditioning subsystem (PCS) includes an inverter circuit configured to mutually covert direct current (DC) power of a storage battery and alternating current (AC) power, a command value acquiring portion configured to acquire a command value from a higher-level apparatus to charge or discharge the storage battery, a DC voltage acquiring portion configured to acquire a DC voltage on the storage battery side, and a limiter processing portion configured to perform a process of setting to limit each of an upper limit and a lower limit of the command value acquired by the command value acquiring portion on the basis of the DC voltage acquired by the DC voltage acquiring portion.

The utility model relates to a rear-phase-cut single-live-wire type wall light modulator, which comprises an MOS (Metal Oxide Semiconductor) tube switch loop unit, a singlechip control unit and a direct-current power supply unit, the MOS tube switch loop unit comprises a wiring terminal J2 connected with an MOS tube Q1, a grid electrode of the MOS tube Q1 is connected with four resistors in series in sequence and then is connected with an MOS tube Q2, a drain electrode of the MOS tube Q2 is connected with a diode D2, the diode D2 is connected with a diode D1, a fixed end contact of a single-pole double-throw switch is connected with the MOS tube Q2, and two movable end contacts of the single-pole double-throw switch are connected with the wiring terminal J1 and the wiring terminal J3 respectively; the direct-current power supply unit comprises an alternating-current voltage waveform acquisition circuit, a direct-current voltage drop circuit, an overcurrent protection circuit and a filtering voltage stabilizing circuit; according to the single-chip microcomputer control unit, a linear sliding potentiometer is connected with the PC2 end of a single-chip microcomputer after being connected with a resistor in series, the linear sliding potentiometer and a rotary potentiometer are sequentially connected between the output end of the direct-current power supply unit and the ground in series, a triode Q6 is connected with a triode Q5 and then connected with the collector electrode of a triode Q7, and the base electrode of the triode Q7 is connected with the PA6 end of the single-chip microcomputer after being connected with a resistor in series.