An electronic load device and method for simulating load characteristics

Abstract

The application provides an electronic load device and method for simulating load characteristics, comprising a bridgeless PFC rectification and voltage stabilization circuit, a full-bridge inverter circuit, an AC / DC signal acquisition circuit, a control circuit, an isolation driving circuit and a power conversion circuit; the bridgeless PFC rectification and voltage stabilization circuit is used for realizing the functions of front-stage rectification and voltage stabilization and load characteristic simulation; the full-bridge inverter circuit is used for realizing the function of inverter and current stabilization; the AC / DC signal acquisition circuit is used for acquiring AC / DC signals; the isolation driving circuit is used for realizing electrical isolation; the power conversion circuit is used for providing a suitable working voltage; and the control circuit is used for generating control signals for controlling the bridgeless PFC rectification and voltage stabilization circuit and the full-bridge inverter circuit; so as to realize the function of simulating various load characteristics and improve the safety of load simulation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of load simulation, in particular to an electronic load device and method for simulating load characteristics. BACKGROUND

[0002] Simulation load technology can simulate various load characteristics in power systems through simulation devices to test the performance, stability and robustness of power sources in power systems. Existing simulation load technology includes the following: tungsten filament load: using tungsten filament resistors and other resistive devices, it can simulate various load characteristics such as linearity and nonlinearity. The disadvantages are that it requires a large physical space and cooling equipment, and the energy consumption is large. Electronic load: using electronic devices to simulate load characteristics, it can achieve high precision and high speed simulation. The disadvantages are that the device cost is high, and it may be affected by temperature and voltage. Simulation load capacitor: using variable capacitors to simulate different load characteristics, for example, large capacity capacitors can be used to simulate motor load characteristics. The disadvantages are that the device volume is large, and multiple components may be required to complete a simulation load capacitor. Rotary variable load: by changing the position, speed and direction of the rotary variable, it can simulate varying load characteristics such as sliding friction, inertia and rotor heat transfer. The disadvantages are that it is difficult to implement, and requires complex mechanical equipment.

[0003] In view of the shortcomings of existing simulation load, the present application proposes an electronic load device and method for simulating load characteristics, which automatically controls the no bridge PFC (power factor correction) rectification and stabilization circuit and the full bridge inverter circuit through the control circuit, realizes the function of simulating various load characteristics, and improves the safety of load simulation. SUMMARY

[0004] The purpose of this invention is to provide an electronic load device for simulating load characteristics, comprising a bridgeless PFC rectifier and regulator circuit, a full-bridge inverter circuit, an AC / DC signal acquisition circuit, a control circuit, an isolation drive circuit, and a power conversion circuit. The bridgeless PFC rectifier and regulator circuit is communicatively connected to the full-bridge inverter circuit, the AC / DC signal acquisition circuit, and the isolation drive circuit to achieve pre-stage rectification and voltage regulation and load characteristic simulation functions. The full-bridge inverter circuit is also communicatively connected to the AC / DC signal acquisition circuit and the isolation drive circuit to achieve inverter current stabilization. The AC / DC signal acquisition circuit is also communicatively connected to the control circuit and the power conversion circuit to acquire input signals. The system comprises a bridgeless PFC rectifier and regulator circuit, an input AC / DC signal for the full-bridge inverter circuit, and an output AC / DC signal for the full-bridge inverter circuit. The isolation drive circuit is also communicatively connected to the control circuit for electrical isolation and controls the bridgeless PFC rectifier and regulator circuit and the full-bridge inverter circuit based on the control signal output by the control circuit. The power conversion circuit is also connected to the control circuit to provide suitable operating voltages for the AC / DC signal acquisition circuit, the control circuit, and the isolation drive circuit. The control circuit generates control signals for the bridgeless PFC rectifier and regulator circuit and the full-bridge inverter circuit based on the signals acquired by the AC / DC signal acquisition circuit.

[0005] Furthermore, the bridgeless PFC rectifier and voltage regulator circuit adopts a dual-loop control strategy of the PWM (Pulse Width Modulation) rectifier. The outer loop is the DC-side voltage loop, and the inner loop is the AC current instantaneous value control loop. The output current amplitude parameter of the outer loop is fed to the inner loop, and multiplied by the unit sine to obtain the instantaneous value of the inner loop command. The phase of the unit sine is determined by the set power factor and the output value of the phase-locked loop.

[0006] Furthermore, the full-bridge inverter circuit adopts SPWM (sinusoidal pulse width modulation) modulation. Based on the error between the actual input current amplitude and the required amplitude, the modulation of the inverter unit reference wave is adjusted so that the actual input current amplitude is equal to the required amplitude.

[0007] Furthermore, generating control signals for the bridgeless PFC rectifier and voltage regulator circuit includes: acquiring the voltage signal E input to the bridgeless PFC rectifier and voltage regulator circuit. ac A phase-locked loop (PLL) is implemented to achieve the phase-locked function; the DC bus voltage U of the bridgeless PFC rectifier and regulator circuit is acquired and output. dc and AC input current I ac A cascaded PI D algorithm is used to stabilize the DC bus voltage.

[0008] Furthermore, generating control signals for the full-bridge inverter circuit includes: acquiring the DC bus voltage U input to the full-bridge inverter circuit.dc Perform cascaded PID algorithm processing; acquire the current I input to the bridgeless PFC rectifier and regulator circuit. ac For current feedforward control, the signal is multiplied by the reference voltage signal output from the phase-locked loop and processed using a regular sampling algorithm to output an SPWM wave, resulting in an inverter voltage e that is in phase, frequency, and amplitude identical to the input voltage. ac .

[0009] Furthermore, the cascaded PI D algorithm processing includes: converting the DC bus voltage U... dc It serves as the voltage outer loop input and is converted into a current reference signal I. dcref The current reference signal I dcref As the input of the inner current loop, the output of the inner current loop is obtained; the output of the inner current loop is multiplied by the reference signal generated by the limiting, normalization and phase-locked loop to obtain the initial control signal; the initial control signal is processed by a regular sampling algorithm to obtain the register value, which is put into the control circuit to control the bridgeless PFC rectifier circuit and the full-bridge inverter circuit.

[0010] The present invention also aims to provide an electronic load method for simulating load characteristics, comprising: determining whether an ADC sampling interrupt is triggered; if so, acquiring current and voltage signals; the current and voltage signals including AC input voltage, AC input current, DC bus voltage, inverter output voltage, and inverter output current; and outputting the grid phase and adjusting the power factor θ using a phase-locked loop. P The PI algorithm is applied to both the inner loop of the rectifier current and the inner loop of the inverter current. The discrete control time of the rectifier PI controller and the discrete control time of the inverter PI controller are determined to be greater than 20 sampling periods. If the discrete control time of the rectifier PI controller is greater than 20 sampling periods, the PI algorithm is applied to the outer loop of the rectifier voltage; otherwise, the original rectifier SPWM is output. If the discrete control time of the inverter PI controller is greater than 20 sampling periods, the outer loop of the inverter voltage is controlled; otherwise, the original inverter SPWM is output. The adjusted rectifier SPWM and the adjusted inverter SPWM are output respectively.

[0011] Furthermore, the phase-locked loop outputs the grid phase and power factor adjustment variables θ. P The circuit includes: a control circuit that obtains the input grid voltage signal through AC / DC sampling; a multiplier phase detector that compares the phase difference between the input grid voltage signal and the feedback signal; an output angular frequency that follows the same instantaneous frequency change pattern through a low-pass filter; a control signal that adjusts the output frequency of the oscillator to synchronize it with the input signal; and a periodic limiting output to obtain the phase of the input voltage.

[0012] Furthermore, the expression for the voltage-controlled characteristic of the oscillator is:

[0013] ω u (t) = ω0 + K0u c (t)

[0014] Wherein, ω u (t) represents the oscillation frequency of the voltage-controlled oscillator;ω0 represents the oscillation angular frequency of the voltage-controlled oscillator when the input control voltage is zero or direct current;K0 represents the control sensitivity;u c (t) represents the input control voltage of the voltage-controlled oscillator.

[0015] Further, the period of the adjusted rectifier SPWM and the adjusted inverter SPWM is:

[0016]

[0017] Wherein, δ represents the period;period represents the maximum period value of the SPWM output in the control circuit;m represents the normalized value of the control algorithm PID output;ω r T D represents the output of the software phase-locked loop;θ P represents the power factor regulation variable.

[0018] The technical scheme of the embodiment of the present application has at least the following advantages and beneficial effects:

[0019] The electronic load device for simulating load characteristics provided by the present application can automatically control the no-bridge PFC rectifier voltage stabilizing circuit and the full-bridge inverter circuit through the control circuit, realize the function of simulating various load characteristics, and improve the safety of load simulation. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 An exemplary module diagram of an electronic load device for simulating load characteristics provided by some embodiments of the present application;

[0021] Figure 2 An exemplary circuit diagram of a full-bridge topology provided by some embodiments of the present application;

[0022] Figure 3A An overall circuit diagram of single power supply to double power supply provided by some embodiments of the present application;

[0023] Figure 3B A partial circuit diagram of single power supply to double power supply provided by some embodiments of the present application;

[0024] Figure 3C A partial circuit diagram of single power supply to double power supply provided by some embodiments of the present application;

[0025] Figure 3D A partial circuit diagram of single power supply to double power supply provided by some embodiments of the present application;

[0026] Figure 4A The overall circuit diagram of the optocoupler driving circuit provided for some embodiments of the present application;

[0027] Figure 4B The partial circuit diagram of the optocoupler driving circuit provided for some embodiments of the present application;

[0028] Figure 4C The partial circuit diagram of the optocoupler driving circuit provided for some embodiments of the present application;

[0029] Figure 4D The partial circuit diagram of the optocoupler driving circuit provided for some embodiments of the present application;

[0030] Figure 5A The overall circuit diagram of the differential voltage sampling provided for some embodiments of the present application;

[0031] Figure 5B The partial circuit diagram of the differential voltage sampling provided for some embodiments of the present application;

[0032] Figure 6 The overall circuit diagram of the differential current sampling provided for some embodiments of the present application;

[0033] Figure 7 The exemplary flow chart of the electronic load method for simulating load characteristics provided for some embodiments of the present application;

[0034] Figure 8 The exemplary flow chart of the phase locked loop output grid phase and power factor adjustment variable provided for some embodiments of the present application. DETAILED DESCRIPTION

[0035] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in connection with the drawings of the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0036] Figure 1 The exemplary module diagram of the electronic load device for simulating load characteristics provided for some embodiments of the present application. As shown in Figure 1 The device includes a bridgeless PFC rectification and voltage stabilization circuit, a full-bridge inverter circuit, an AC / DC signal acquisition circuit, a control circuit, an isolation driving circuit and a power conversion circuit.

[0037] The bridgeless PFC rectification and voltage stabilization circuit is in communication connection with the full-bridge inversion circuit, the AC / DC signal acquisition circuit and the isolation driving circuit, accesses 220V AC power, and is used for realizing the front-stage rectification and voltage stabilization and load characteristic simulation functions.

[0038] In some embodiments, the bridgeless PFC rectification and voltage stabilization circuit adopts a double-loop control strategy of a PWM rectifier, an outer loop is a DC side voltage loop, and an inner loop is an AC current instantaneous value control loop; the outer loop outputs a current amplitude parameter to the inner loop, and simultaneously multiplies the unit sine to obtain an inner loop instruction instantaneous value; wherein, a phase of the unit sine is determined by a set power factor and a phase-locked loop output value.

[0039] The full-bridge inversion circuit is also in communication connection with the AC / DC signal acquisition circuit and the isolation driving circuit, accesses the output of the front stage, and is used for realizing the inversion and current stabilization functions.

[0040] In some embodiments, the full-bridge inversion circuit adopts a variable modulation factor SPWM modulation, adjusts the modulation factor of an inversion unit reference wave according to the error between an actual input current amplitude and a required amplitude, and makes the actual input current amplitude equal to the required amplitude.

[0041] The bridgeless PFC rectification and voltage stabilization circuit and the full-bridge inversion circuit constitute a power side-electronic load main circuit.

[0042] The AC / DC signal acquisition circuit is also in communication connection with the control circuit and the power conversion circuit, is used for acquiring AC / DC signals input into the bridgeless PFC rectification and voltage stabilization circuit, input into the full-bridge inversion circuit and output from the full-bridge inversion circuit. In some embodiments, the AC / DC signal acquisition circuit includes a voltage divider, a voltage stabilizer, a feedback component and an LM358 gain circuit and other elements, can convert a differential current input signal in any certain range into a DC voltage signal, then accesses the voltage stabilizer, makes the input signal be accurately acquired, and serves as a reference voltage input into the feedback component, realizes gain adjustment and signal adjustment. An RC low-pass passive filter circuit is added, filters out interference, this differential current sampling solves circuit construction, output sensitivity and voltage supply capacity, ensures that the system has reliable performance, high precision and reliable operability, and improves the quality of the phase-locked loop. The acquisition of voltage and current signals all uses an ADC module built in a single-chip microcomputer, greatly saves resources and simplifies circuit design.

[0043] The isolation drive circuit is also connected with the control circuit, for realizing electrical isolation, and controlling the bridgeless PFC rectification and stabilization circuit and the full-bridge inversion circuit based on the control signal output by the control circuit. For example, the isolation drive circuit amplifies the SPWM drive signal to drive the MOSFET. In some embodiments, the isolation drive circuit includes a transformer isolation power supply of an optical coupler TLP352 and a PWM controller UC3845B, and the isolation circuit prevents interference, current backflow, and the like caused by direct connection, especially between the low-voltage control circuit and the external high-voltage circuit.

[0044] The power conversion circuit is also connected with the control circuit, for providing appropriate working voltages for the AC / DC signal acquisition circuit, the control circuit and the isolation drive circuit. In some embodiments, the power conversion circuit can be realized by a power conversion board, which converts a 24V power supply into ±12V, 5V, the 5V is connected with a TMS320F28335 single-chip microcomputer, for providing appropriate working voltages for the TMS320F28335 single-chip microcomputer, the ±12V is connected with the AC / DC signal sampling circuit, for providing appropriate bipolar power supply for the AC / DC signal sampling circuit, the 24V is connected with the isolation drive circuit, for providing appropriate working voltages for the isolation drive circuit, to ensure that the control signal can completely drive the MOSFET through the drive circuit. Among them, the bipolar power supply is a TPS5430 single-to-dual power supply, which has a wide input voltage range, can output 1.22V, has strong load capacity, can output a current of up to 3A (peak value up to 5A), has a maximum efficiency of 95%, and can provide stable power supply for the sampling circuit. For more information about the single-to-dual power supply, see Figures 3A-3D and the related description.

[0045] The control circuit is used to generate control signals for controlling the bridgeless PFC rectification and stabilization circuit and the full-bridge inversion circuit based on the signals collected by the AC / DC signal acquisition circuit. In some embodiments, the control circuit can select a single-chip microcomputer circuit, and the single-chip microcomputer selects a TMS320F28335 single-chip microcomputer, which realizes monitoring of power side data through the AC / DC sampling circuit, realizes data processing, makes a control strategy to adjust SPWM data, and outputs SPWM waves to the control isolation drive circuit using an internal EPWM module to realize electrical isolation and real-time control of dynamic characteristics of the electronic load. The power module provides stable power supply for the drive circuit, the TMS320F28335 single-chip microcomputer and the AC / DC sampling circuit to ensure stable operation of the low-voltage side.

[0046] In some embodiments, generating the control signal for controlling the bridgeless PFC rectification and stabilization circuit includes: collecting a voltage signal E ac, and the phase-locked loop processing is performed to realize the phase-locked function; the direct-current bus voltage U dc and the input alternating-current measurement current I ac are collected, and the cascade PID algorithm processing is performed to realize the direct-current bus voltage stability. The stable inverter input direct-current voltage is provided for the inverter circuit in the rear stage, and the normal operation of the circuit in the rear stage is ensured.

[0047] In some embodiments, the control signal for controlling the full-bridge inverter circuit is generated, including: collecting the direct-current bus voltage U dc , performing the cascade PID algorithm processing; collecting the current I ac , performing the current feedforward control, multiplying the reference voltage signal output by the phase-locked loop to perform the regular sampling algorithm processing, and outputting the SPWM wave to obtain the inverter voltage e ac .

[0048] In some embodiments, the cascade PID algorithm processing includes: taking the direct-current bus voltage U dc as the voltage outer loop input and converting it into the current reference signal I dcref ; taking the current reference signal I dcref as the current inner loop input to obtain the current inner loop output; multiplying the current inner loop output with the reference signal generated through the amplitude limiting, normalization processing and phase-locked loop to obtain the initial control signal; performing the regular sampling algorithm processing on the initial control signal to obtain the register value, and putting the register value into the control circuit to control the no-bridge PFC rectifier circuit and the full-bridge inverter circuit.

[0049] In some embodiments, the phase-locked loop processing includes: obtaining the input power grid voltage signal through the AC / DC sampling by the single-chip microcomputer, comparing the phase difference between the input power grid voltage signal and the feedback signal by using the multiplication phase detector; obtaining the output angular frequency which is the same as the instantaneous frequency variation law through the low-pass filter; generating the control signal to adjust the output frequency of the oscillator to make it synchronized with the input signal; performing the period amplitude limiting processing to obtain the phase of the input voltage.

[0050] In some embodiments, the no-bridge PFC rectifier circuit adopts the double-loop control strategy of the PWM rectifier, the outer loop is the direct-current side voltage loop, and the inner loop is the AC current instantaneous value control loop. The current amplitude parameter output by the outer loop is multiplied by the unit sine to obtain the inner loop instruction instantaneous value, and the phase of the unit sine is determined by the set power factor (load characteristic). Finally, the load characteristic simulation (power factor adjustment) is realized, the direct-current side output is stabilized, and the stable operation of the inverter link in the rear stage is ensured. For example, the control circuit controls the no-bridge PFC rectifier circuit to realize the rectification and voltage stabilization, including: obtaining the input voltage E acand the DC side output voltage U dc ; voltage outer loop PI controller; obtain input current I ac ; current inner loop PI controller; current inner loop output * PLL output.

[0051] In some embodiments, the full-bridge inverter device, using variable modulation SPWM modulation, according to the error between the actual input current amplitude and the required amplitude, adjusts the modulation m of the inverter unit, so that the actual input current amplitude is equal to the set amplitude. Finally realize the DC-AC function, provide stable working voltage for our ordinary household appliances, or other AC power equipment, and adjust the current of the load. For example, the control signal controls the full-bridge inverter circuit to realize inverter current stabilization, including: obtaining input voltage U dc ; voltage outer loop PI controller; obtain input current I ac ; current inner loop PI controller output; current inner loop output * PLL output.

[0052] Figure 2 The exemplary circuit diagram of the full-bridge topology provided for some embodiments of the present application.

[0053] As Figure 2 shown, the full-bridge topology includes four MOS transistors S1, S2, S3 and S4. To realize the function of electronic load, the device has two main topologies, and the control signals of the two main topologies are generated by the single-chip microcomputer. By controlling the conduction states of the eight silicon carbide MOS transistors, and there is no simultaneous conduction state of the same side transistors, the function of electronic load is realized. In some embodiments, the drive waveforms of the controlled MOSFET and the adjacent two transistors are complementary with a dead zone of 50us, and the single-chip microcomputer needs to output eight such complementary SPWM waves to control the two main topologies.

[0054] In some embodiments, regular sampling method can be used to adjust the period of output PWM in real time, so as to output SPWM wave to realize control of the main topology. Period Wherein period is the maximum period value of the SPWM output in the single-chip microcomputer, and in this system, period = 3600, that is, the carrier frequency is 20Khz, and m is the normalized value of the PID output of the control algorithm, which plays a role in controlling the voltage and current. ω r T D is the output of the software phase-locked loop, which is the real-time phase of the power grid, θ P is a power factor regulation variable, which is used to realize the load characteristic simulation function, and the program flow of the controller input amplitude parameter, I ac feedforward and E acThe feedforward obtains a current feedforward result and a voltage feedforward result; the current feedforward result and the voltage feedforward result are subjected to amplitude limiting processing and data normalization processing respectively to obtain a current normalized result and a voltage normalized result; the current normalized result and the voltage normalized result are subjected to regular sampling respectively to output SPWM for controlling the full-bridge inverter circuit and the bridgeless PFC rectification and voltage stabilization circuit respectively. The SPWM wave output through regular sampling controls the silicon carbide MOSFET in real time.

[0055] In some embodiments, the state equation for realizing the electronic load function by the bridgeless PFC rectification and voltage stabilization circuit and the full-bridge inverter circuit is as follows:

[0056]

[0057]

[0058] Wherein, u s represents an AC source voltage value; R represents a load resistance value; i s represents an AC source current value; L represents an input inductance value; S A represents a left half-bridge working state; S B represents a right half-bridge working state; u dc represents a DC side voltage value; i R represents a load current value; C represents a filter capacitance value; i dc represents a DC side output current value. For the above state equation, after Laplace transformation, the P I controller is introduced to control the current of the system, so as to achieve closed-loop control of the output voltage of the bridgeless PFC rectification device. The same full-bridge topology is used for inverter and rectification.

[0059] Figure 3A The overall circuit diagram of single power supply to double power supply provided by some embodiments of the present application. Figure 3B The partial circuit diagram of single power supply to double power supply provided by some embodiments of the present application. Figure 3C The partial circuit diagram of single power supply to double power supply provided by some embodiments of the present application. Figure 3D The partial circuit diagram of single power supply to double power supply provided by some embodiments of the present application. As Figures 3A-3D shown, the single power supply to double power supply is realized by two TPS5430 chips and their peripheral circuits.

[0060] Figure 4A The overall circuit diagram of the optocoupler driving circuit provided by some embodiments of the present application. Figure 4B The partial circuit diagram of the optocoupler driving circuit provided by some embodiments of the present application. Figure 4C The partial circuit diagram of the optocoupler driving circuit provided by some embodiments of the present application. Figure 4DPartial circuit diagram of the optical coupling driving circuit provided for some embodiments of the present application. As shown in Figures 4A-4D , the optical coupling driving circuit is realized by UC3845BD1G chip and two pieces of TLP352 chip and their peripheral circuits.

[0061] Figure 5A Overall circuit diagram of the differential voltage sampling provided for some embodiments of the present application. Figure 5B Partial circuit diagram of the differential voltage sampling provided for some embodiments of the present application. As shown in Figure 5A and 5B , the differential voltage sampling is realized by voltage sampling circuit and voltage signal amplification circuit.

[0062] Figure 6 Overall circuit diagram of the differential current sampling provided for some embodiments of the present application. As shown in Figure 6 , the differential current sampling is realized by current sampling circuit and current signal amplification circuit.

[0063] Figure 7 Exemplary flow chart of the electronic load method for simulating load characteristics provided for some embodiments of the present application. As shown in Figure 7 , the electronic load method for simulating load characteristics comprises the following contents:

[0064] Judging whether to trigger ADC sampling interruption.

[0065] If yes, collecting current voltage signal; the current voltage signal comprises AC input voltage, AC input current, DC bus voltage, inverter output voltage and inverter output current.

[0066] Phase locked loop outputs power grid phase and adjusts power factor variable θ P .

[0067] Respectively performing PI algorithm processing on rectifier current inner loop and inverter current inner loop.

[0068] Respectively judging whether the control time of rectifier current inner loop (i.e., rectifier controller discrete control time) and inverter current inner loop (i.e., PI controller discrete control time) is greater than 20 sampling periods.

[0069] If the inner loop control is greater than 20 sampling periods, performing PI algorithm processing on rectifier voltage outer loop; otherwise, outputting original rectifier SPWM; if the inner loop control is greater than 20 sampling periods, performing inverter voltage outer loop PI control; otherwise, outputting original inverter SPWM.

[0070] Respectively outputting adjusted rectifier SPWM and adjusted inverter SPWM.

[0071] In some embodiments, the period of the adjusted rectifier SPWM and the adjusted inverter SPWM is:

[0072]

[0073] wherein δ represents the period; period represents the maximum period value of the SPWM output in the control circuit; m represents the normalized value of the control algorithm PID output; ω r T D represents the output of the software phase-locked loop; θ P represents the power factor adjustment variable. For more information about the electronic load method for simulating load characteristics, see Figure 1 and the related description.

[0074] Figure 8 An exemplary flow chart of the phase-locked loop output grid phase and power factor adjustment variable provided for some embodiments of the present application. In the present application, the grid phase locking is achieved using the principle of a multiplication phase detector, and a safety limiting process is performed. The single-chip microcomputer obtains the input grid voltage signal through AC / DC sampling, compares the phase difference between the input grid voltage signal and the feedback signal using a multiplication phase detector, and then obtains the same output angular frequency as the instantaneous frequency variation law through a low-pass filter. A control signal is generated to adjust the output frequency of the oscillator so that it is synchronized with the input signal. Finally, a cycle limiting process is performed on the output to obtain the phase of the input voltage.

[0075] For example, the phase-locked loop output grid phase and power factor adjustment variable θ P may include:

[0076] The control circuit obtains the input grid voltage signal through AC / DC sampling, compares the phase difference between the input grid voltage signal and the feedback signal using a multiplication phase detector;

[0077] obtains the same output angular frequency as the instantaneous frequency variation law through a low-pass filter;

[0078] generates a control signal to adjust the output frequency of the oscillator so that it is synchronized with the input signal;

[0079] performs a cycle limiting process on the output to obtain the phase of the input voltage.

[0080] In some embodiments, the expression of the voltage-controlled characteristic of the oscillator is:

[0081] ω u (t) = ω0+ K0u c (t)

[0082] wherein ω u(t) represents the oscillation frequency of the voltage-controlled oscillator; ω0represents the oscillation angular frequency of the voltage-controlled oscillator when the input control voltage is zero or a direct current; K0represents the control sensitivity; u c (t) represents the input control voltage of the voltage-controlled oscillator. The above expression shows that when u C (t) varies with time, the oscillation frequency ω u (t) also varies with time, the phase-locked loop enters "frequency pulling", automatically tracking the frequency of the input signal, so that the phase-locked loop enters the locked state, and keeps ω0=ω i unchanged, at this time ω0is the output of the phase-locked loop in the system program. For more information about the output grid phase and power factor regulation variables, see Figure 1 and its related description.

[0083] The above only describes the preferred embodiments of the present application and is not used to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An electronic load device for simulating load characteristics, characterized by, The application relates to a power supply test system, which comprises a bridgeless PFC rectification and voltage stabilization circuit, a full-bridge inverter circuit, an AC / DC signal acquisition circuit, a control circuit, an isolation driving circuit and a power conversion circuit. The bridgeless PFC rectification and voltage stabilization circuit is in communication connection with the full-bridge inverter circuit, the AC / DC signal acquisition circuit and the isolation driving circuit, and is used for realizing front-stage rectification and voltage stabilization and load characteristic simulation functions; the bridgeless PFC rectification and voltage stabilization circuit adopts a double-loop control strategy of a PWM rectifier, an outer loop is a DC side voltage loop, and an inner loop is an AC current instantaneous value control loop; an outer loop output current amplitude parameter is given to the inner loop, and meanwhile, the outer loop output current amplitude parameter is multiplied by a unit sine to obtain an inner loop instruction instantaneous value; the phase of the unit sine is determined by a set power factor and a phase-locked loop output value; the full-bridge inverter circuit is also in communication connection with the AC / DC signal acquisition circuit and the isolation driving circuit, and is used for realizing inverter current stabilization functions; the full-bridge inverter circuit adopts variable modulation SPWM modulation; according to the error between an actual input current amplitude and a required amplitude, the modulation of a reference wave of an inverter unit is adjusted, so that the actual input current amplitude is equal to the required amplitude; the AC / DC signal acquisition circuit is also in communication connection with the control circuit and the power conversion circuit, and is used for acquiring AC / DC signals of input of the bridgeless PFC rectification and voltage stabilization circuit, input of the full-bridge inverter circuit and output of the full-bridge inverter circuit; the AC / DC signals include AC input voltage, AC input current, DC bus voltage, inverter output voltage and inverter output current; the isolation driving circuit is also in communication connection with the control circuit, and is used for realizing electrical isolation and controlling the bridgeless PFC rectification and voltage stabilization circuit and the full-bridge inverter circuit based on a control signal output by the control circuit; the power conversion circuit is also connected with the control circuit, and is used for providing working voltages for the AC / DC signal acquisition circuit, the control circuit and the isolation driving circuit; the control circuit is used for generating control signals of the bridgeless PFC rectification and voltage stabilization circuit and the full-bridge inverter circuit based on signals acquired by the AC / DC signal acquisition circuit; the process of generating the control signals comprises the following steps: adopting a cascade PID algorithm to process the DC bus voltage as voltage outer loop input and convert the DC bus voltage into a current reference signal; the current reference signal is input into a current inner loop to obtain a current inner loop output; the current inner loop output is multiplied by a reference signal generated through amplitude limiting, normalization processing and a phase-locked loop to obtain an initial control signal; the initial control signal is processed through a regular sampling algorithm to obtain a register value; and when generating the control signals, the control circuit judges whether the discrete control time of a rectification PI controller and the discrete control time of an inverter PI controller are greater than 20 sampling periods; if yes, the rectification voltage outer loop and the inverter voltage outer loop are processed through PI algorithm respectively; otherwise, original SPWM output is adopted. The process of generating the control signals of the bridgeless PFC rectification and voltage stabilization circuit comprises the following steps: The process of generating the control signals of the full-bridge inverter circuit comprises the following steps: The process of generating the control signals of the bridgeless PFC rectification and voltage stabilization circuit comprises the following steps: Judging whether an ADC sampling interruption is triggered or not; ​ ​ 2. The electronic load device simulating load characteristics according to claim 1, characterized in that, ​ Collecting a voltage signal input to the bridgeless PFC rectification and voltage stabilization circuit Doing phase-locked loop processing to realize phase-locked loop function Collecting output the DC bus voltage of the bridgeless PFC rectification voltage stabilizing circuit and AC input current , do cascade PID algorithm processing, realize the voltage stability of DC bus side.

3. Electronic load device for simulating load characteristics according to claim 2, characterized in that ​ Collecting a dc bus voltage input to the full-bridge inverter circuit , and performing a cascade PID algorithm processing Collecting input current of the bridgeless PFC rectification and voltage stabilization circuit The current feedforward control is multiplied by the reference voltage signal output by the phase-locked loop to perform a regular sampling algorithm, and an inverter voltage with the same frequency, phase and amplitude as the input voltage is output by the SPWM wave .

4. An electronic load method for simulating load characteristics of an electronic load device according to any one of claims 1-3, characterized in that, ​ ​ If yes, collect current voltage signals; the current voltage signals include AC input voltage, AC input current, DC bus voltage, inverter output voltage and inverter output current; Phase-locked loop output grid phase and regulated power factor variable ; Respectively, PI algorithm processing is performed on the rectifier current inner ring and the inverter current inner ring; Respectively, whether the rectifier PI controller discrete control time and the inverter PI controller discrete control time are greater than 20 sampling periods is judged; If the rectifier PI controller discrete control time is greater than 20 sampling periods, PI algorithm processing is performed on the rectifier voltage outer ring; otherwise, the original rectifier SPWM output is taken; If the inverter PI controller discrete control time is greater than 20 sampling periods, inverter voltage outer ring control is performed; otherwise, the original inverter SPWM output is taken; Respectively, the adjusted rectifier SPWM and the adjusted inverter SPWM are output.

5. The electronic load method of simulating load characteristics according to claim 4, wherein, Phase-locked loop output grid phase and power factor regulation variable comprising: The control circuit obtains input grid voltage signals through AC / DC sampling, and uses a multiplication phase detector to compare the phase difference between the input grid voltage signals and feedback signals; An output angular frequency same as the instantaneous frequency change law is obtained through a low-pass filter; A control signal is generated to adjust the output frequency of the oscillator, so that it is synchronized with the input signal; Periodic amplitude limiting processing is performed on the output to obtain the phase of the input voltage.

6. The electronic load method of simulating load characteristics according to claim 5, wherein, The expression of the voltage control characteristic of the oscillator is: wherein, represents an oscillation frequency of the voltage-controlled oscillator; represents an oscillation angular frequency of the voltage-controlled oscillator when the input control voltage is zero or a direct current voltage; represents a control sensitivity; represents an input control voltage of the voltage-controlled oscillator.

7. The electronic load method of simulating load characteristics according to claim 4, wherein, The period of the adjusted rectifier SPWM and the adjusted inverter SPWM is: wherein, denotes a period; denotes a maximum period value of the SPWM output in the control circuit; denotes a normalized value of the control algorithm PID output; denotes an output of the software phase-locked loop; denotes a power factor regulation variable.

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