Harmonic suppression voltage stabilization regulation system and method for variable frequency drive

Abstract

The present application relates to the field of power electronics, and discloses a kind of variable frequency driver harmonic suppression voltage regulation control system and method, comprising: three-phase rectification filter topology unit, DC bus state high-frequency perception unit, bus multi-frequency band harmonic decomposition and disturbance decoupling unit, virtual damping resonance active suppression unit, dynamic modulation timing reconstruction and harmonic hedging unit and three-phase inverter power output unit;System collects DC bus transient signal and decouples, generates virtual damping compensation component, combines transient feedforward coefficient and reverse hedging component to generate combined voltage command, reconstructs space vector action timing and drives inverter power output, the present application is used to suppress the penetration modulation disturbance of bus ripple to inverter phase voltage, remodels impedance characteristic to suppress filter loop parasitic resonance, eliminates vector beat frequency lag and suppresses phase current harmonic distortion.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a harmonic suppression and voltage regulation system and method for frequency converter drivers. Background Technology

[0002] AC / DC power conversion systems typically use a three-phase rectifier circuit to convert AC to DC, and then filter the DC side through a DC filter network composed of smoothing inductors and filter capacitors. The subsequent inverter bridge then converts the DC to AC with controlled frequency and amplitude to drive the load. This topology constitutes the basic circuit for power conversion and frequency conversion drive. When the power grid experiences voltage drops, asymmetrical fluctuations, or harmonic intrusion, the rectifier stage will cause characteristic sub-pulsating voltages on the intermediate DC bus, further affecting the modulation process and output voltage of the inverter bridge. This results in low-frequency distortion and torque pulsation in the output AC current. At the same time, the voltage source inverter bridge will exhibit equivalent negative impedance characteristics under closed-loop control, which is prone to impedance mismatch with the DC filter circuit and causes high-frequency series resonance, resulting in transient overvoltage spikes on the DC bus and exacerbating current oscillations and electrical stress in the power devices.

[0003] To address the aforementioned issues, existing methods can reduce voltage ripple by increasing the bus capacitor capacity, but this increases hardware size and manufacturing cost, and still cannot eliminate resonant instability caused by negative impedance. Adding passive damping resistors to the DC circuit can also reduce active power loss due to continuous heat generation, thus lowering system conversion efficiency. To overcome the hardware bottlenecks of size, cost, and heat loss, existing technologies attempt to construct virtual impedance by reshaping the inverter control algorithm. For example, Chinese invention patent application CN113363959A discloses a method for constructing virtual impedance for three-phase inverters, establishing a small-signal linearization model based on the constant power steady-state operating point. This type of small-signal inversion control introduces an input impedance regulator along a specific axis to improve the system impedance characteristics by inverting the transfer function. However, this type of small-signal inversion control strictly relies on the linearization approximation assumption near the steady-state operating point. Under nonlinear strong disturbance transient conditions such as sudden voltage drops in the grid, large-range speed regulation, or heavy-load start-up, the actual operating point deviates significantly, and the preset small-signal transfer function is easily distorted and fails. At the same time, this scheme does not decouple and link the low-frequency pulsation ripple of the bus and parasitic high-frequency resonance with the inverter modulation timing in the discrete domain. It cannot take into account both active suppression of resonance and dynamic reconstruction of space vector modulation timing under large transient disturbances, and it is difficult to effectively reduce the adverse disturbance of bus transient distortion on the inverter output power quality.

[0004] Therefore, the technical problem to be solved by this invention is how to improve the inverter input admittance characteristics and suppress the parasitic resonance of the filter circuit without increasing the heat loss of the damping resistor, while simultaneously separating and compensating the fluctuations of different frequency bands of the DC bus and the timing of space vector modulation in real time, so as to improve the bus voltage regulation accuracy and output power quality when the grid voltage fluctuates over a wide range and the operating conditions change. Summary of the Invention

[0005] To address the problems in the background art, the present invention provides the following technical solution: a frequency converter driver harmonic suppression and voltage regulation system, comprising:

[0006] The three-phase rectifier and filter topology unit connects to the AC power grid at the AC end and to the DC bus at the DC end for outputting DC power.

[0007] The DC bus status high-frequency sensing unit has its sampling end connected to the DC bus and is used to collect the DC bus transient voltage signal and DC bus transient current signal.

[0008] The bus multi-band harmonic decomposition and disturbance decoupling unit, connected to the DC bus status high-frequency sensing unit, is used to decouple the DC bus transient voltage signal by frequency division and output the DC voltage reference deviation, characteristic secondary pulsation ripple component, and high-frequency resonant disturbance component. The bus multi-band harmonic decomposition and disturbance decoupling unit includes: a DC deviation extraction module, used to calculate the average value of the DC bus transient voltage within the fundamental frequency period based on a moving average filter window, and to subtract the average value of the DC bus transient voltage from the nominal value of the rated DC voltage to output the DC voltage reference deviation; a harmonic quadrature extraction module, used to filter the DC bus transient voltage signal in the discrete time domain based on a parallel second-order generalized integrator, separating the second-order pulsation component and the sixth-order pulsation component, and superimposing them to generate the characteristic secondary pulsation ripple component; and a high-frequency resonant capture module, used to extract the fluctuation signal falling within the inductor-capacitor resonant frequency band of the DC bus transient voltage signal through a digital bandpass filter, and output the high-frequency resonant disturbance component.

[0009] The virtual damped resonance active suppression unit, connected to the bus multi-band harmonic decomposition and disturbance decoupling unit, is used to generate virtual damped voltage compensation components in the stationary coordinate system based on the high-frequency resonance disturbance components.

[0010] The dynamic modulation timing reconstruction and harmonic offset unit is connected to the bus multi-band harmonic decomposition and disturbance decoupling unit and the virtual damping resonance active suppression unit, respectively. It is used to generate transient feedforward compensation coefficient based on the ratio of the rated DC voltage nominal value to the DC bus transient voltage signal, generate reverse offset component based on the characteristic sub-pulse ripple component, add the basic phase voltage control command and the virtual damping voltage compensation component, multiply by the transient feedforward compensation coefficient, and then subtract the reverse offset component to generate the synthesized voltage command. Based on this, the discrete action time of the effective working vector and the zero vector is calculated and the switching drive pulse signal is output.

[0011] The three-phase inverter power output unit connects to the DC bus at the DC end, receives switch drive pulse signals at the control end, and connects to the controlled electric drive load at the AC end.

[0012] Preferably, the three-phase rectifier filter topology unit includes a three-phase uncontrolled rectifier bridge and a smoothing inductor and an electrolytic capacitor bank. The filter network has an inductance of 0.8mH for the smoothing inductor and a total capacitance of 1500μF for the electrolytic capacitor bank. The DC bus status high-frequency sensing unit includes a Hall voltage sensor, a Hall current sensor, and a dual-channel synchronous analog-to-digital converter. The sampling trigger terminal of the dual-channel synchronous analog-to-digital converter is hardware-synchronized and locked with the apex and basal point of the pulse width modulation symmetrical triangular carrier of the three-phase inverter power output unit. The sampling frequency is configured to be 20kHz.

[0013] Preferably, the virtual damped resonance active suppression unit includes: a current resonance extraction module, used to acquire the three-phase inverter output current and convert it to a synchronous rotating coordinate system, and extract the current resonance from it. High-frequency resonant current components of the shaft and Shaft high-frequency resonant current component; damping voltage calculation module, used to calculate... High-frequency resonant current components of the shaft and The high-frequency resonant current component of the shaft is multiplied by a preset virtual damping coefficient to generate a negative feedback damping compensation voltage in a synchronous rotating coordinate system. The coordinate inverse transformation module is used to convert the negative feedback damping compensation voltage into a virtual damping voltage compensation component in a two-phase stationary coordinate system, so that the input admittance of the three-phase inverter power output unit at the system resonant frequency band exhibits positive resistance.

[0014] Preferably, the dynamic modulation timing reconstruction and harmonic offsetting unit calculates the discrete action time of adjacent first effective working vectors, the discrete action time of second effective working vectors, and the total action time of zero vectors within a single switching cycle based on the geometric projection of the synthesized voltage command onto the base vector of the target sector. It then allocates the action time of each vector according to a symmetrical seven-segment timing sequence: one-quarter of the total zero vector action time is allocated in the initial segment of a single switching cycle, half of the discrete action time of the first effective working vector and half of the discrete action time of the second effective working vector are allocated adjacently, half of the total zero vector action time is allocated in the middle segment of the cycle, and half of the discrete action time of the second effective working vector, half of the discrete action time of the first effective working vector, and one-quarter of the total zero vector action time are sequentially mirrored in the symmetrical subsequent segment.

[0015] Preferably, the digital bandpass filter in the high-frequency resonant capture module is a fourth-order Butterworth digital bandpass filter with a passband frequency range of 800Hz to 3500Hz, a passband attenuation of less than 0.5dB, and a stopband attenuation of greater than 40dB, used to filter out DC steady-state components and pulsating ripples below 800Hz.

[0016] Preferably, the virtual damping coefficient is set in the range of 1.0Ω to 2.0Ω, and the current resonance extraction module includes a lead-lag phase correction stage when extracting the high-frequency resonant current component to compensate for the phase influence of the sampling calculation delay on the positive resistive damping characteristics.

[0017] Preferably, the dynamic modulation timing reconstruction and harmonic offsetting unit further includes a modulation ratio linear boundary clamping module, which scales the discrete action time of each effective working vector by the same proportion and correspondingly amplifies the action time of the zero vector when the synthesized voltage command exceeds the maximum linear modulation boundary determined by the transient voltage signal of the DC bus.

[0018] Preferably, the three-phase inverter power output unit operates in an ambient temperature range of -40℃ to 60℃ and the voltage fluctuation range of the three-phase AC power grid is within the range of -20% to +20% of the rated voltage. When the transient voltage signal of the DC bus suddenly drops, the dynamic modulation timing reconstruction and harmonic offset unit increases the transient feedforward compensation coefficient to compensate for the impact of the DC bus voltage drop on the amplitude of the output fundamental voltage. At the same time, the virtual damping resonance active suppression unit suppresses the high-frequency series resonance overvoltage caused by the smoothing inductor and electrolytic capacitor bank.

[0019] A harmonic suppression and voltage regulation method for a variable frequency drive, used to operate a harmonic suppression and voltage regulation system for a variable frequency drive, includes the following steps:

[0020] Step S1: The AC power is converted into DC power containing DC voltage and ripple components through a three-phase rectifier and filter topology unit, and the transient voltage signal and transient current signal of the DC bus are synchronously acquired through a DC bus status high-frequency sensing unit.

[0021] Step S2 involves using a multi-band harmonic decomposition and disturbance decoupling unit to decouple the DC bus transient voltage signal by frequency division, outputting the DC voltage reference deviation, characteristic secondary ripple component, and high-frequency resonant disturbance component. Specifically, the average DC bus transient voltage within the fundamental frequency cycle is calculated using a moving average filter window, and the difference between the average DC bus transient voltage and the nominal DC voltage value is used to output the DC voltage reference deviation. A parallel second-order generalized integrator filters the DC bus transient voltage signal in the discrete time domain, separating the second-order and sixth-order ripple components, which are then superimposed to generate the characteristic secondary ripple component. A digital bandpass filter extracts the fluctuation signal falling within the inductor-capacitor resonant frequency band of the DC bus transient voltage signal, outputting the high-frequency resonant disturbance component.

[0022] Step S3: The virtual damping voltage compensation component in the two-phase stationary coordinate system is generated by the virtual damping resonance active suppression unit based on the high-frequency resonance disturbance component.

[0023] Step S4: Through the dynamic modulation timing reconstruction and harmonic offset unit, the ratio of the nominal value of the rated DC voltage to the transient voltage signal of the DC bus is calculated to generate the transient feedforward compensation coefficient. The reverse offset component is generated based on the characteristic sub-pulse ripple component. The basic phase voltage control command and the virtual damping voltage compensation component are added together and multiplied by the transient feedforward compensation coefficient. Then, the reverse offset component is subtracted to generate the composite voltage command. The discrete action time of the effective working vector and the zero vector is calculated based on the composite voltage command, and the switch drive pulse signal is output.

[0024] Step S5: The three-phase inverter power output unit receives the switch drive pulse signal, converts the electrical energy of the DC bus into three-phase AC power, and supplies it to the controlled electric drive load.

[0025] The beneficial effects of this invention are:

[0026] 1. In the harmonic suppression and voltage regulation of frequency converter drivers, by separating the steady-state component, second-order pulsation, and sixth-order pulsation in the DC bus voltage, and using the corresponding components to perform feedforward compensation and reverse compensation for the modulation command, the influence of DC bus voltage fluctuations on inverter output can be corrected in a timely manner, reducing the secondary modulation of inverter phase voltage by bus pulsation voltage. When asymmetrical drops or background harmonics occur in the AC input, it is beneficial to maintain the symmetry of the fundamental voltage waveform of the inverter bridge output, reduce the low-frequency distortion of the output current and the torque pulsation of the electrically driven load, and improve the output stability of the frequency converter driver under grid voltage fluctuation conditions.

[0027] 2. By extracting the high-frequency resonant component from the inverter output current and forming a virtual damping voltage compensation, the input admittance characteristics of the inverter bridge in the resonant frequency band of the inductor-capacitor filter circuit can be improved, and the series resonance generated by the filter circuit can be actively suppressed. This method does not require additional passive damping resistors in the DC circuit, which can avoid the active power loss caused by the continuous heating of the damping resistors. At the same time, it reduces the transient overvoltage of the DC bus and the current oscillation of the power devices, reduces the electrical stress on the devices, and improves the operating stability of the frequency converter under load changes.

[0028] 3. By adjusting the duration of the space vector based on the transient voltage of the bus, the characteristic sub-pulse ripple, and the virtual damping voltage compensation component, the duration of the effective working vector and the zero vector can be corrected according to the DC bus state. This reduces the volt-second balance deviation and modulation phase lag caused by bus voltage fluctuations, thereby reducing the total harmonic distortion rate of the inverter output phase current, reducing the electromagnetic torque pulsation and additional losses of the electrically driven load, and enabling the inverter output to maintain good power quality when the bus voltage fluctuates. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0030] Figure 1 This is a flowchart of the bus multi-band decoupling and space vector timing reconstruction control process of the present invention;

[0031] Figure 2 This is a block diagram illustrating the topological interaction principle of active resonance suppression and modulation ratio boundary clamping in this invention. Detailed Implementation

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0033] A frequency converter driver harmonic suppression and voltage regulation system includes:

[0034] The three-phase rectifier and filter topology unit connects to the AC power grid at the AC end and to the DC bus at the DC end for outputting DC power.

[0035] The DC bus status high-frequency sensing unit has its sampling end connected to the DC bus and is used to collect the DC bus transient voltage signal and DC bus transient current signal.

[0036] The bus multi-band harmonic decomposition and disturbance decoupling unit, connected to the DC bus status high-frequency sensing unit, is used to decouple the DC bus transient voltage signal by frequency division and output the DC voltage reference deviation, characteristic secondary pulsation ripple component, and high-frequency resonant disturbance component. The bus multi-band harmonic decomposition and disturbance decoupling unit includes: a DC deviation extraction module, used to calculate the average value of the DC bus transient voltage within the fundamental frequency period based on a moving average filter window, and to subtract the average value of the DC bus transient voltage from the nominal value of the rated DC voltage to output the DC voltage reference deviation; a harmonic quadrature extraction module, used to filter the DC bus transient voltage signal in the discrete time domain based on a parallel second-order generalized integrator, separating the second-order pulsation component and the sixth-order pulsation component, and superimposing them to generate the characteristic secondary pulsation ripple component; and a high-frequency resonant capture module, used to extract the fluctuation signal falling within the inductor-capacitor resonant frequency band of the DC bus transient voltage signal through a digital bandpass filter, and output the high-frequency resonant disturbance component.

[0037] The virtual damped resonance active suppression unit, connected to the bus multi-band harmonic decomposition and disturbance decoupling unit, is used to generate virtual damped voltage compensation components in the stationary coordinate system based on the high-frequency resonance disturbance components.

[0038] The dynamic modulation timing reconstruction and harmonic offset unit is connected to the bus multi-band harmonic decomposition and disturbance decoupling unit and the virtual damping resonance active suppression unit, respectively. It is used to generate transient feedforward compensation coefficient based on the ratio of the rated DC voltage nominal value to the DC bus transient voltage signal, generate reverse offset component based on the characteristic sub-pulse ripple component, add the basic phase voltage control command and the virtual damping voltage compensation component, multiply by the transient feedforward compensation coefficient, and then subtract the reverse offset component to generate the synthesized voltage command. Based on this, the discrete action time of the effective working vector and the zero vector is calculated and the switching drive pulse signal is output.

[0039] The three-phase inverter power output unit connects to the DC bus at the DC end, receives switch drive pulse signals at the control end, and connects to the controlled electric drive load at the AC end.

[0040] Preferably, the three-phase rectifier filter topology unit includes a three-phase uncontrolled rectifier bridge and a smoothing inductor and an electrolytic capacitor bank. The filter network has an inductance of 0.8mH for the smoothing inductor and a total capacitance of 1500μF for the electrolytic capacitor bank. The DC bus status high-frequency sensing unit includes a Hall voltage sensor, a Hall current sensor, and a dual-channel synchronous analog-to-digital converter. The sampling trigger terminal of the dual-channel synchronous analog-to-digital converter is hardware-synchronized and locked with the apex and basal point of the pulse width modulation symmetrical triangular carrier of the three-phase inverter power output unit. The sampling frequency is configured to be 20kHz.

[0041] Preferably, the virtual damped resonance active suppression unit includes: a current resonance extraction module, used to acquire the three-phase inverter output current and convert it to a synchronous rotating coordinate system, and extract the current resonance from it. High-frequency resonant current components of the shaft and Shaft high-frequency resonant current component; damping voltage calculation module, used to calculate... High-frequency resonant current components of the shaft and The high-frequency resonant current component of the shaft is multiplied by a preset virtual damping coefficient to generate a negative feedback damping compensation voltage in a synchronous rotating coordinate system. The coordinate inverse transformation module is used to convert the negative feedback damping compensation voltage into a virtual damping voltage compensation component in a two-phase stationary coordinate system, so that the input admittance of the three-phase inverter power output unit at the system resonant frequency band exhibits positive resistance.

[0042] Preferably, the dynamic modulation timing reconstruction and harmonic offsetting unit calculates the discrete action time of adjacent first effective working vectors, the discrete action time of second effective working vectors, and the total action time of zero vectors within a single switching cycle based on the geometric projection of the synthesized voltage command onto the base vector of the target sector. It then allocates the action time of each vector according to a symmetrical seven-segment timing sequence: one-quarter of the total zero vector action time is allocated in the initial segment of a single switching cycle, half of the discrete action time of the first effective working vector and half of the discrete action time of the second effective working vector are allocated adjacently, half of the total zero vector action time is allocated in the middle segment of the cycle, and half of the discrete action time of the second effective working vector, half of the discrete action time of the first effective working vector, and one-quarter of the total zero vector action time are sequentially mirrored in the symmetrical subsequent segment.

[0043] Preferably, the digital bandpass filter in the high-frequency resonant capture module is a fourth-order Butterworth digital bandpass filter with a passband frequency range of 800Hz to 3500Hz, a passband attenuation of less than 0.5dB, and a stopband attenuation of greater than 40dB, used to filter out DC steady-state components and pulsating ripples below 800Hz.

[0044] Preferably, the virtual damping coefficient is set in the range of 1.0Ω to 2.0Ω, and the current resonance extraction module includes a lead-lag phase correction stage when extracting the high-frequency resonant current component to compensate for the phase influence of the sampling calculation delay on the positive resistive damping characteristics.

[0045] Preferably, the dynamic modulation timing reconstruction and harmonic offsetting unit further includes a modulation ratio linear boundary clamping module, which scales the discrete action time of each effective working vector by the same proportion and correspondingly amplifies the action time of the zero vector when the synthesized voltage command exceeds the maximum linear modulation boundary determined by the transient voltage signal of the DC bus.

[0046] Preferably, the three-phase inverter power output unit operates in an ambient temperature range of -40℃ to 60℃ and the voltage fluctuation range of the three-phase AC power grid is within the range of -20% to +20% of the rated voltage. When the transient voltage signal of the DC bus suddenly drops, the dynamic modulation timing reconstruction and harmonic offset unit increases the transient feedforward compensation coefficient to compensate for the impact of the DC bus voltage drop on the amplitude of the output fundamental voltage. At the same time, the virtual damping resonance active suppression unit suppresses the high-frequency series resonance overvoltage caused by the smoothing inductor and electrolytic capacitor bank.

[0047] A harmonic suppression and voltage regulation method for a variable frequency drive, used to operate a harmonic suppression and voltage regulation system for a variable frequency drive, includes the following steps:

[0048] Step S1: The AC power is converted into DC power containing DC voltage and ripple components through a three-phase rectifier and filter topology unit, and the transient voltage signal and transient current signal of the DC bus are synchronously acquired through a DC bus status high-frequency sensing unit.

[0049] Step S2 involves using a multi-band harmonic decomposition and disturbance decoupling unit to decouple the DC bus transient voltage signal by frequency division, outputting the DC voltage reference deviation, characteristic secondary ripple component, and high-frequency resonant disturbance component. Specifically, the average DC bus transient voltage within the fundamental frequency cycle is calculated using a moving average filter window, and the difference between the average DC bus transient voltage and the nominal DC voltage value is used to output the DC voltage reference deviation. A parallel second-order generalized integrator filters the DC bus transient voltage signal in the discrete time domain, separating the second-order and sixth-order ripple components, which are then superimposed to generate the characteristic secondary ripple component. A digital bandpass filter extracts the fluctuation signal falling within the inductor-capacitor resonant frequency band of the DC bus transient voltage signal, outputting the high-frequency resonant disturbance component.

[0050] Step S3: The virtual damping voltage compensation component in the two-phase stationary coordinate system is generated by the virtual damping resonance active suppression unit based on the high-frequency resonance disturbance component.

[0051] Step S4: Through the dynamic modulation timing reconstruction and harmonic offset unit, the ratio of the nominal value of the rated DC voltage to the transient voltage signal of the DC bus is calculated to generate the transient feedforward compensation coefficient. The reverse offset component is generated based on the characteristic sub-pulse ripple component. The basic phase voltage control command and the virtual damping voltage compensation component are added together and multiplied by the transient feedforward compensation coefficient. Then, the reverse offset component is subtracted to generate the composite voltage command. The discrete action time of the effective working vector and the zero vector is calculated based on the composite voltage command, and the switch drive pulse signal is output.

[0052] Step S5: The three-phase inverter power output unit receives the switch drive pulse signal, converts the electrical energy of the DC bus into three-phase AC power, and supplies it to the controlled electric drive load.

[0053] Example 1: Current industrial-grade precision temperature control equipment uses a three-phase AC power grid to power the frequency converter driver. The effective value of the rated input line voltage is 380V, and the power frequency is 50Hz. The three-phase rectifier filter topology unit consists of a three-phase uncontrolled rectifier bridge, a smoothing inductor, and an electrolytic capacitor bank, forming an LC-type filter network. The nominal inductance of the smoothing inductor is 0.8mH, and the total capacitance of the electrolytic capacitor bank is 1500μF. The nominal value of the rated DC voltage under rated symmetrical input conditions is set to 540V. When an asymmetrical voltage drop occurs in the grid-side power supply, or when the driven compressor inductive load is in a variable speed transition process, the DC bus simultaneously experiences transient voltage drop, low-frequency ripple penetration modulation, and series coupling caused by the negative impedance characteristics of the rectifier filter circuit and the inverter closed loop. The resonant DC bus status high-frequency sensing unit uses Hall voltage and Hall current sensors to acquire signals. The sampling trigger terminal of the dual-channel synchronous analog-to-digital converter is hardware-synchronized and locked with the apex and basal point of the symmetrical triangular carrier modulated by the inverter switch. The sampling frequency is 20kHz, corresponding to a single discrete switch period of 50μs. This allows for the synchronous acquisition of DC bus transient voltage and DC bus transient current signals. The acquired DC bus transient current signal is multiplied by the DC bus transient voltage signal to obtain the instantaneous input power of the DC bus, which is used to monitor the system energy flow and perform protection blocking during overcurrent. This current signal also serves as a reference quantity for the impedance characteristics of the bus filter circuit, used to assist in judging the change of inverter input admittance during dynamic processes.

[0054] The bus multi-band harmonic decomposition and disturbance decoupling unit receives the DC bus transient voltage signal in the discrete time domain. Using one fundamental frequency cycle as a moving average filter window, with a 20kHz sampling frequency corresponding to a 50Hz power frequency, each filter window contains 400 sampling points. Based on this, the average DC bus transient voltage within the current power frequency cycle is calculated. When the measured DC bus transient voltage drops by 10% to 486V, the difference between this average value and the nominal 540V rated DC voltage is obtained to determine the DC voltage reference deviation. For the 100Hz second-order pulsation component and the 300Hz sixth-order pulsation component formed on the DC side due to grid imbalance and rectifier commutation, the harmonic quadrature extraction module uses two harmonics corresponding to 100Hz and 300Hz respectively. The process involves parallel processing of independent second-order generalized integrator structures. Each integrator structure is discretized by bilinear transformation. Within each switching cycle, the process iterates based on the current input DC voltage error signal and the state variables of the previous cycle to obtain filter components in phase with the target pulsation frequencies of 100Hz and 300Hz, respectively. The two components are then algebraically superimposed to form a characteristic sub-pulsation ripple component with an instantaneous amplitude of 15V. The high-frequency resonant capture module uses a fourth-order Butterworth digital bandpass filter with a passband frequency of 800Hz to 3500Hz, a passband attenuation of less than 0.5dB, and a stopband attenuation of greater than 40dB to directly extract the fluctuation signal in the transient DC bus voltage signal that falls within the inductor-capacitor resonant frequency band and outputs the high-frequency resonant disturbance component.

[0055] The virtual damped resonant active suppression unit receives the high-frequency resonant disturbance component and processes the three-phase inverter output current according to the resonant frequency band corresponding to this component. The current resonance extraction module converts the three-phase inverter output current to a synchronously rotating dq coordinate system, and obtains the d-axis high-frequency resonant current component and the q-axis high-frequency resonant current component after bandpass filtering and lead / lag phase correction within the corresponding resonant frequency band. The damping voltage calculation module multiplies the two high-frequency resonant current components by the virtual damping coefficient. In this embodiment The voltage is calibrated to 1.5Ω, forming a negative feedback damping compensation voltage in a synchronous rotating coordinate system. Subsequently, through inverse Park transformation, the negative feedback damping compensation voltage is converted into a virtual damping voltage compensation component in a two-phase stationary coordinate system. This negative feedback relationship causes the virtual damping voltage compensation component to reverse the high-frequency resonant current in the target resonant frequency band and is superimposed on the base phase voltage control command. This causes the input admittance of the three-phase inverter power output unit to exhibit positive resistance at the system resonant frequency band. During the closed-loop control of the inverter bridge, the original equivalent negative impedance will cause a slight increase in the DC bus voltage disturbance accompanied by a reverse decrease in the DC input current. After adding the above negative feedback damping compensation, the amplification of the resonant current is suppressed, and the DC input port forms a positive resistive real admittance in this frequency band, thereby weakening the resonant amplification formed by the coupling of the negative impedance and the filter circuit.

[0056] The dynamic modulation timing reconstruction and harmonic offset unit calculates the transient feedforward compensation coefficient based on the ratio of the nominal 540V rated DC voltage to the transient voltage signal of the 486V DC bus in the current sampling period. This coefficient is used to compensate for the impact of the overall DC bus voltage drop on the amplitude of the inverter bridge output fundamental voltage. Simultaneously, it uses the characteristic secondary ripple component, the current fundamental voltage rotation angle, and a preset harmonic offset gain coefficient of 0.08. The reverse offset component in the two-phase stationary coordinate system is generated. For the basic phase voltage control command in the two-phase stationary coordinate system, it is first added to the virtual damped voltage compensation component, then multiplied by the transient feedforward compensation coefficient, and then the reverse offset component is subtracted to obtain the composite voltage command in the two-phase stationary coordinate system. The processing relationship remains as follows: ,in, and These represent the base phase voltage control commands in the two-phase stationary coordinate system. and These represent the virtual damping voltage compensation components in the two-phase stationary coordinate system, respectively. This represents the transient feedforward compensation coefficient. This represents the harmonic offset gain coefficient. This represents the characteristic sub-pulsation ripple component. Indicates the current fundamental frequency rotation electrical angle. and To synthesize the voltage command, the characteristic sub-pulsation ripple component is multiplied by the cosine and sine components of the current fundamental voltage rotation angle to form a reverse offset component, which keeps the output fundamental voltage fluctuation caused by the bus voltage fluctuation in the modulation wave generation stage in the opposite direction to the compensation direction.

[0057] Based on the geometric projection of the synthesized voltage command onto the target sector's base vector, the dynamic modulation timing reconstruction and harmonic offsetting unit calculates the discrete action time of adjacent first effective working vectors, the discrete action time of the second effective working vector, and the total action time of the zero vector within a single switching cycle. When the target synthesized vector is located in the first sector, one-quarter of the total action time of the zero vector is allocated in the initial segment of a single 50μs switching cycle, followed by half of the discrete action time of the first and second effective working vectors; half of the total action time of the zero vector is allocated in the middle segment of the cycle, and then half of the discrete action time of the second and first effective working vectors is sequentially mirrored in the latter half of the cycle. Half the time and a quarter of the total action time of the zero vector make the sum of the discrete action times of each vector equal to a single switching cycle. Thus, the transient voltage signal of the DC bus, the characteristic secondary ripple component, and the virtual damped voltage compensation component are jointly included in the calculation process of the synthesized voltage command and the action time of the space vector. When the DC bus voltage drops and is accompanied by harmonic disturbances, the three-phase inverter power output unit maintains positive resistive damping characteristics in the system resonant frequency band. At the same time, it reduces the modulation effect of DC bus ripple on the fundamental phase voltage of the inverter output and the overvoltage caused by series resonance, so that the fundamental waveform of the output three-phase AC power remains symmetrical, the total harmonic distortion rate of the phase current is kept within the controlled range, and the electromagnetic torque ripple of the compressor inductive load is reduced accordingly.

[0058] Example 2: This example examines the impact of various control components on DC bus ripple, high-frequency resonance, and inverter output current during AC-DC-AC power conversion. A power electronics test platform was constructed, consisting of a three-phase programmable AC power supply, a three-phase uncontrolled rectifier bridge, an LC-type filter network composed of a smoothing inductor and electrolytic capacitor bank, a three-phase insulated-gate bipolar transistor inverter bridge, and an inductive motor load. The rated line voltage of the three-phase programmable AC power supply is 380V, and the fundamental frequency is 50Hz. During testing, fifth and seventh background harmonics and broadband electromagnetic interference noise with a signal-to-noise ratio of 20dB are superimposed. The nominal inductance of the smoothing inductor is 0.8mH, the total capacitance of the electrolytic capacitor bank is 1500μF, and the nominal rated DC voltage at rated symmetrical input is 540V. The DC bus status high-frequency sensing unit uses Hall effect sensors... Voltage and Hall current sensors acquire transient DC bus voltage and current signals at a hardware synchronous sampling frequency of 20kHz. The inverter switch carrier period is 50μs. A digital signal processor performs multi-band processing on the transient DC bus voltage signal. A power frequency moving average filter window is used to obtain the DC voltage reference deviation. A parallel second-order generalized integrator is used to obtain the characteristic sub-pulse ripple component. A fourth-order Butterworth digital bandpass filter with a passband of 800Hz to 3500Hz directly extracts the fluctuation signal within the inductor-capacitor resonant frequency band of the transient DC bus voltage signal, forming a high-frequency resonant disturbance component. A virtual damping resonant active suppression unit extracts the high-frequency resonant current component from the three-phase inverter output current based on the resonant frequency band corresponding to the high-frequency resonant disturbance component, and combines it with the virtual damping coefficient. The virtual damped voltage compensation component is formed, and the dynamic modulation timing reconstruction and harmonic offset unit are combined with the transient feedforward compensation coefficient and the harmonic offset gain coefficient. The reverse offset component is generated and the spatial vector discrete action time is reconstructed. During the test, the peak-to-peak value of the DC bus ripple, the peak voltage of the high-frequency resonance, and the total harmonic distortion rate of the phase current are recorded. And conversion efficiency.

[0059] Different control loops were removed or weakened to observe the corresponding output changes. Control group one used traditional proportional-integral control, operating at 380V rated voltage. Set to 0. Set to 0, the peak-to-peak DC bus ripple voltage is 24.6V, the high-frequency resonant peak voltage is 592V, and the total harmonic distortion of the phase current is... The conversion efficiency is 96.12%, with a rate of 6.84%. Under this configuration, the bus pulsation caused by grid-side voltage disturbances and rectifier commutation is not compensated for by feedforward and reverse offset. The DC bus voltage fluctuation directly enters the inverter modulation process. Control group II retains harmonic offsetting but cancels virtual damping control. When the input is 380V and 5% harmonics are superimposed, 0, The value was 0.08, the measured peak-to-peak value of the DC bus ripple was 8.2V, the high-frequency resonant peak voltage rose to 688V, and the total harmonic distortion of the phase current was [missing value]. The conversion efficiency was 96.45%, with a conversion rate of 4.95%. In this group, the reverse offset component still corrected the low-frequency ripple, but without the virtual damping voltage compensation component, the damping of the inverter in the resonant frequency band weakened, and the high-frequency resonant peak value increased accordingly. The control group retained virtual damping control but canceled feedforward and harmonic offset. When the input line voltage dropped by 20% to 304V, 1.5 The DC bus ripple peak-to-peak value is 0, the high-frequency resonant peak voltage is 498V, and the total harmonic distortion rate of the phase current is 0. The conversion efficiency is 95.80% and the conversion rate is 8.12%. Without transient feedforward compensation and reverse offset components participating in the synthesis voltage command correction, the low-frequency pulsation of the DC bus continues to act on the inverter modulation process, and the phase current distortion worsens with voltage drop.

[0060] Maintaining harmonic offset gain coefficient The value is 0.08, achieved by changing the virtual damping coefficient. Observe the change between resonance suppression and output current. Control group four will be subjected to a sudden heavy load of 380V. With a value set to 0.5, the measured peak-to-peak DC bus ripple voltage was 6.5V, the high-frequency resonant peak voltage was 634V, and the total harmonic distortion of the phase current was... The conversion efficiency is 96.88% at 3.42%. When the virtual damping coefficient is small, the virtual damping voltage compensation component corresponding to the high-frequency resonant current is small, and the resonant peak value remains at a high level. Under the same 380V sudden heavy load condition, control group five will... Increased to 2.8, The value remains at 0.08, the peak-to-peak value of the DC bus ripple is 6.1V, and the high-frequency resonant peak voltage drops to 546V, but the total harmonic distortion rate of the phase current increases. The conversion efficiency rose to 4.18%, with a conversion efficiency of 96.31%. The high-frequency resonant peak value of this group further decreased, while the larger virtual damping voltage compensation component made the synthesized voltage command closer to the modulation boundary, and the output current distortion increased accordingly.

[0061] Within the set range of virtual damping coefficient 1.0 to 2.0, maintain Boundary and nominal parameter tests were performed to achieve a damping of 0.08. For sample group one of this invention, the lower limit of damping was taken, and the damping was tested under a rated operating condition of 380V. With a voltage set to 1.0, the measured peak-to-peak DC bus ripple voltage was 5.8V, the high-frequency resonant peak voltage was 552V, and the total harmonic distortion of the phase current was [value missing]. The conversion efficiency is 97.21% and the nominal parameters are used in sample group two of this invention under rated operating conditions of 380V. Set it to 1.5. Maintaining a value of 0.08, the peak-to-peak DC bus ripple is 4.2V, the high-frequency resonant peak voltage is 544V, and the total harmonic distortion of the phase current is... The conversion efficiency is 97.35%, with a damping limit of 1.82%. The sample of this invention uses the upper limit of the three damping parameters, and under a rated operating condition of 380V, it will... Set to 2.0 With a value set to 0.08, the measured peak-to-peak DC bus ripple voltage was 4.6V, the high-frequency resonant peak voltage was 542V, and the total harmonic distortion of the phase current was... The conversion efficiency is 97.18%, with a conversion rate of 2.15%. In the three sample groups, after the high-frequency resonant disturbance component determines the target resonant frequency band, the virtual damping resonant active suppression unit forms a negative feedback virtual damping voltage compensation component in this frequency band. At the same time, the transient feedforward compensation coefficient and the reverse offset component enter the synthetic voltage command, so that the low-frequency bus ripple and the high-frequency resonance are processed by the corresponding control links respectively.

[0062] To further modify the grid-side input conditions, sample group four of this invention uses a 304V input, i.e., a voltage drop of 20% with added harmonics. 1.5 The value is 0.08. After the transient voltage drop of the DC bus, the transient feedforward compensation coefficient changes with the ratio of the nominal value of the rated DC voltage to the transient voltage signal of the DC bus. The reverse offset component continues to participate in the synthesis voltage command correction according to the characteristic sub-pulsation ripple component. The measured peak-to-peak value of the DC bus ripple is 7.4V, the high-frequency resonant peak voltage is 442V, and the total harmonic distortion rate of the phase current is... The conversion efficiency is 96.92%, with a conversion rate of 2.68%. Sample group five of this invention uses a 456V input, i.e., a light load condition with a 20% spurt. 1.5 The measured peak-to-peak value of the DC bus ripple was 5.1V, the peak voltage of the high-frequency resonant voltage was 654V, and the total harmonic distortion rate of the phase current was 0.08. The conversion efficiency is 97.05%, which is 2.26%. When the bus voltage increases, the dynamic modulation timing reconstruction and harmonic offset unit still calculates the discrete action time of the effective working vector and the zero vector according to the synthesized voltage command, so that the output modulation is adjusted according to the current DC bus state.

[0063] The above tests varied the virtual damping control, transient feedforward compensation, reverse offset component, virtual damping coefficient, and grid-side input conditions, while the other test links maintained their corresponding configurations. The changes between the control groups showed that canceling the virtual damping control mainly affected the high-frequency resonant peak voltage, while canceling the feedforward and harmonic offset resulted in significant DC bus ripple and phase current distortion. Within the set virtual damping coefficient range, the virtual damping voltage compensation component and dynamic modulation timing reconstruction worked together on the inverter modulation process, generating corresponding DC bus ripple, high-frequency resonant peak voltage, total harmonic distortion rate of phase current, and conversion efficiency test results under rated input, voltage drop, harmonic superposition, heavy load surge, and overvoltage light load conditions.

[0064] Example 3: Current industrial-grade precision temperature control equipment uses a three-phase AC power grid to power the frequency converter driver. The rated effective value of the input line voltage is 380V, and the power frequency is 50Hz. The three-phase rectifier filter topology unit consists of a three-phase uncontrolled rectifier bridge, a smoothing inductor, and an electrolytic capacitor bank, forming an LC-type filter network. The nominal inductance of the smoothing inductor is 0.8mH, and the total capacitance of the electrolytic capacitor bank is 1500μF. The nominal rated DC voltage under rated symmetrical input conditions is 540V. The operating temperature is -40℃, and a 20% symmetrical voltage drop occurs on the grid side. At that time, the transient voltage of the DC bus drops to 432V, and the compressor load is simultaneously in the high-pressure differential heavy-load start-up acceleration stage. The modulation depth of the fundamental phase voltage of the inverter bridge output increases accordingly. The high-frequency sensing unit of the DC bus status collects the transient voltage signal and transient current signal of the DC bus at a hardware synchronous sampling frequency of 20kHz through Hall voltage sensor and Hall current sensor. The corresponding single switching cycle is 50μs, which provides synchronous sampling data for subsequent bus multi-band harmonic decomposition and disturbance decoupling, virtual damping compensation and modulation ratio linear boundary clamping.

[0065] The bus multi-band harmonic decomposition and disturbance decoupling unit receives the transient voltage signal of the DC bus. Based on a sampling frequency of 20kHz and a power frequency of 50Hz, a power frequency moving average filter window corresponds to 400 sampling points. This filter window is used to obtain the average transient voltage of the DC bus within the current power frequency cycle, and a DC voltage reference deviation is formed accordingly. For the 100Hz second-order pulsation component and the 300Hz sixth-order pulsation component generated on the DC side by grid-side sag and rectifier commutation, a second-order generalized integrator is connected in parallel for discrete filtering. The two target pulsation components are superimposed to obtain a characteristic sub-pulsation ripple component with an instantaneous amplitude of 22V. The high-frequency resonant capture module uses a passband frequency of 800Hz to 3500Hz. A fourth-order Butterworth digital bandpass filter with a passband attenuation of less than 0.5dB and a stopband attenuation of greater than 40dB directly intercepts the fluctuation signal in the transient voltage signal of the DC bus that falls within the resonant frequency band of the inductor and capacitor, and outputs the high-frequency resonant disturbance component. In the DC bus circuit of this embodiment, the inherent resonant frequency of the fundamental filter network composed of the smoothing inductor and the filter capacitor is in a lower frequency band. The high-frequency resonance in the range of 800Hz to 3500Hz is formed by the combined action of the equivalent series inductance of the electrolytic capacitor, the stray inductance of the busbar, and the parasitic inductance and capacitance of the power circuit lead. Therefore, the passband of the digital bandpass filter avoids the power frequency and low-frequency rectification pulsation, and only retains the DC bus voltage fluctuation in this high-frequency resonant frequency band.

[0066] The virtual damped resonance active suppression unit determines the resonant frequency band to be suppressed based on the high-frequency resonant disturbance component, and processes the three-phase inverter output current within this frequency band. The current resonance extraction module converts the three-phase inverter output current to a synchronous rotating coordinate system, and obtains the d-axis and q-axis high-frequency resonant current components after bandpass filtering and lead / lag phase correction. The damping voltage calculation module multiplies the two high-frequency resonant current components by a virtual damping coefficient of 1.5Ω. The negative feedback damping compensation voltage is formed in the synchronous rotating coordinate system, and then the virtual damping voltage compensation component in the two-phase stationary coordinate system is obtained through coordinate inverse transformation. The lead-lag phase correction stage adopts a first-order digital differential structure, which calculates the current resonance signal of the current sampling period, the historical input signal of the previous sampling period, and the historical output signal of the previous sampling period according to predetermined coefficients. This is used to compensate for the calculation and pulse width modulation update delay of about 1.5 switching cycles at the 20kHz sampling frequency. The correction stage provides a 25° to 35° lead phase in the target resonance frequency band, so that the negative feedback damping compensation voltage maintains a reverse correction relationship with the high-frequency resonance current in the control superposition direction. As a result, the input admittance of the three-phase inverter power output unit at the system resonance frequency band exhibits positive resistance.

[0067] The dynamic modulation timing reconstruction and harmonic offset unit obtains the transient feedforward compensation coefficient based on the ratio of the nominal value of the 540V rated DC voltage to the current transient voltage signal of the 432V DC bus. Under this operating condition, the ratio is 1.25. Simultaneously, it combines the characteristic sub-pulsation ripple component, the current fundamental frequency rotation electrical angle, and a harmonic offset gain coefficient of 0.08. The reverse offset component is generated. The base phase voltage control command is first added to the virtual damped voltage compensation component, then multiplied by the transient feedforward compensation coefficient, and the reverse offset component is subtracted to obtain the synthesized voltage command. When the current DC bus transient voltage is 432V, the synthesized voltage command has entered outside the maximum linear modulation boundary. The modulation ratio linear boundary clamping module performs clamping accordingly. The dynamic modulation timing reconstruction and harmonic offsetting unit calculates the first effective working vector discrete action time, the second effective working vector discrete action time, and the zero vector total action time based on the geometric projection of the clamped synthesized voltage command in the direction of the adjacent base vector in the first sector. The calculation is performed within the linear range. When modulating the boundary, the discrete action time of each effective working vector is scaled by the same proportion, and the released time is included in the total action time of the zero vector. Each vector is then allocated according to a symmetrical seven-segment timing sequence. One-quarter of the total action time of the zero vector is allocated in the initial segment of the switching cycle, half of the discrete action time of the first effective working vector and half of the discrete action time of the second effective working vector are allocated in turn, half of the total action time of the zero vector is allocated in the middle segment of the cycle, and the second effective working vector, the first effective working vector and the tail zero vector are allocated in the second half of the cycle in a mirror manner, so that the sum of all discrete action times is consistent with the 50μs switching cycle.

[0068] When -40℃, a 20% drop in grid-side voltage, and heavy-load compressor start-up occur simultaneously, the DC voltage reference deviation, characteristic secondary ripple component, and high-frequency resonant disturbance component enter their respective control loops. The transient feedforward compensation coefficient and reverse offset component correct the modulation effect of DC bus voltage drop and low-frequency ripple on inverter phase voltage. The virtual damping voltage compensation component forms negative feedback for the high-frequency resonant current in the system resonant frequency band. The modulation ratio linear boundary clamping module adjusts the discrete action time of the effective working vector and the zero vector when the synthesized voltage command exceeds the linear modulation boundary. Accordingly, the three-phase inverter power output unit maintains continuous switching drive timing under conditions of deep DC bus voltage drop and high modulation depth, the output phase voltage remains symmetrical, the total harmonic distortion rate of the phase current is within the controlled range, and the electromagnetic torque pulsation of the compressor load is suppressed.

[0069] Example 4: This example combines Figures 1 to 2 This paper describes the harmonic suppression and voltage regulation system and method for variable frequency drives, such as... Figure 1As shown, step S1 converts AC power into DC power containing DC voltage and ripple components through a three-phase rectifier and filter topology unit, and synchronously acquires DC bus transient voltage and current signals through a DC bus state high-frequency sensing unit. Step S2 decouples the DC bus transient voltage signal through a bus multi-band harmonic decomposition and disturbance decoupling unit, outputting DC voltage reference deviation, characteristic sub-pulsation ripple components, and high-frequency resonant disturbance components. Step S3 generates virtual damped voltage compensation components in a two-phase stationary coordinate system based on the high-frequency resonant disturbance components through a virtual damped resonance active suppression unit. Step S4 uses dynamic modulation... The timing reconstruction and harmonic offset unit calculates the ratio of the nominal value of the rated DC voltage to the transient voltage signal of the DC bus to generate the transient feedforward compensation coefficient. It generates the reverse offset component based on the characteristic sub-pulse ripple component. It adds the basic phase voltage control command and the virtual damping voltage compensation component, multiplies it by the transient feedforward compensation coefficient, and then subtracts the reverse offset component to generate the composite voltage command. It calculates the discrete action time of the effective working vector and the zero vector based on the composite voltage command and outputs the switch drive pulse signal. In step S5, the three-phase inverter power output unit receives the switch drive pulse signal, converts the electrical energy of the DC bus into three-phase AC power, and supplies it to the controlled electric drive load.

[0070] like Figure 2 As shown, the three-phase rectifier-filter topology unit converts the DC current into a DC current containing DC voltage and ripple components and outputs it to the DC bus status high-frequency sensing unit. The DC bus status high-frequency sensing unit synchronously acquires the DC bus transient voltage and transient current signals and inputs them to the bus multi-band harmonic decomposition and disturbance decoupling unit. The bus multi-band harmonic decomposition and disturbance decoupling unit extracts the fluctuation signal and outputs the high-frequency resonant disturbance component to the virtual damped resonant active suppression unit. The virtual damped resonant active suppression unit generates a virtual damped voltage compensation component based on the high-frequency resonant disturbance component and inputs it to the dynamic modulation timing reconstruction unit. Along with the harmonic offset unit, the bus multi-band harmonic decomposition and disturbance decoupling unit simultaneously outputs the DC voltage reference deviation and characteristic sub-pulse ripple component to the dynamic modulation timing reconstruction and harmonic offset unit. The dynamic modulation timing reconstruction and harmonic offset unit calculates the discrete action time and outputs the switch drive pulse signal to the three-phase inverter power output unit. When the synthesized voltage command exceeds the maximum linear modulation boundary, it is input to the modulation ratio linear boundary clamping module. The modulation ratio linear boundary clamping module scales the discrete action time of each effective working vector by the same ratio and amplifies the zero vector before inputting it to the three-phase inverter power output unit.

[0071] Example 5: Current industrial-grade precision temperature control equipment uses a three-phase AC power grid to power the frequency converter driver. The rated effective value of the input line voltage is 380V, and the power frequency is 50Hz. The three-phase rectifier filter topology unit consists of a three-phase uncontrolled rectifier bridge, a smoothing inductor, and an electrolytic capacitor bank, forming an LC-type filter network. The nominal inductance of the smoothing inductor is 0.8mH, and the total capacitance of the electrolytic capacitor bank is 1500μF. The nominal rated DC voltage under rated symmetrical input conditions is 540V. When the ambient temperature is -40℃ and a 20% symmetrical voltage drop occurs on the grid side, the rectified output voltage decreases, and the transient voltage of the DC bus drops to... 432V; At this time, the compressor load is in the heavy-load start-up acceleration stage with large differential pressure. The back EMF and torque response of the stator winding cause the inverter bridge to output a fundamental phase voltage with a large amplitude. The fundamental phase voltage control command then approaches the space vector linear modulation boundary. The DC bus status high-frequency sensing unit collects the DC bus transient voltage signal and DC bus transient current signal at a hardware synchronous sampling frequency of 20kHz through Hall voltage sensor and Hall current sensor. The corresponding single switching cycle is 50μs, which provides synchronous sampling data for bus multi-band harmonic decomposition and disturbance decoupling, virtual damping compensation and modulation ratio linear boundary clamping.

[0072] The dynamic modulation timing reconstruction and harmonic offset unit obtains the transient feedforward compensation coefficient based on the ratio of the nominal value of the 540V rated DC voltage to the current transient voltage signal of the 432V DC bus, and combines it with the current fundamental frequency rotation electrical angle and a harmonic offset gain coefficient of 0.08. A reverse offset component in a two-phase stationary coordinate system is generated. The base phase voltage control command and the virtual damped voltage compensation component are added together, multiplied by the transient feedforward compensation coefficient, and then the reverse offset component is subtracted to obtain the synthesized voltage command. When the current DC bus transient voltage is 432V, the synthesized voltage command exceeds the maximum linear modulation boundary determined by the bus voltage. The modulation ratio linear boundary clamping module starts clamping calculation accordingly and proportionally shrinks the synthesized voltage command according to the clamping modulation ratio coefficient with reserved safety adjustment margin to form the synthesized voltage command after boundary clamping. When the target synthesized vector is located in the first sector, it is based on its position in the directions of the two adjacent base working vectors. Geometric projection is used to calculate the discrete action time of the first effective working vector, the discrete action time of the second effective working vector, and the total action time of the zero vector. The discrete action times of the two effective working vectors are scaled by the same ratio, and the action time released after scaling is included in the total action time of the zero vector. Then, according to the symmetrical seven-segment timing sequence, the zero vector is allocated in the initial segment of the switching cycle, and the first and second effective working vectors are allocated in sequence. The complementary zero vector is allocated in the middle segment of the cycle, and the second effective working vector, the first effective working vector, and the tail zero vector are allocated in the reverse order in the second half of the cycle, so that all discrete action times are closed within the 50μs switching cycle.

[0073] When the grid-side voltage drop and inverter modulation approaching the saturation boundary occur simultaneously, the bus multi-band harmonic decomposition and disturbance decoupling unit obtains the DC voltage reference deviation, characteristic sub-pulsation ripple component, and high-frequency resonance disturbance component, respectively. The transient feedforward compensation coefficient and reverse offset component are used to correct the modulation effect of DC bus voltage drop and low-frequency ripple on inverter phase voltage. The virtual damping voltage compensation component is used to suppress high-frequency resonance overvoltage in the inductor-capacitor resonance band. When the synthesized voltage command exceeds the linear modulation boundary, the modulation ratio linear boundary clamping module maintains the vector action time closed within the switching cycle by proportionally scaling the effective working vector discrete action time and correspondingly extending the zero vector total action time. The three-phase inverter power output unit maintains continuous switching drive timing accordingly, the output phase voltage remains symmetrical, the total harmonic distortion rate of the phase current is within the controlled range, and the electromagnetic torque pulsation of the compressor load is suppressed.

[0074] Example 6: Current industrial-grade precision temperature control equipment uses a three-phase AC power grid to power the frequency converter driver. The effective value of the rated input line voltage is 380V, and the power frequency is 50Hz. The three-phase rectifier filter topology unit consists of a three-phase uncontrolled rectifier bridge, a smoothing inductor, and an electrolytic capacitor bank, forming an LC-type filter network. The nominal inductance of the smoothing inductor is 0.8mH, and the total capacitance of the electrolytic capacitor bank is 1500μF. The nominal rated DC voltage under rated symmetrical input conditions is 540V. When a +10% overvoltage transient occurs on the grid side, the transient voltage of the DC bus rises to 594V. At this time, the compressor motor is in continuous operation. During the steady-state operation phase, the DC bus voltage is superimposed with characteristic sub-pulsation ripples formed by rectifier commutation, and is affected by switching actions and system parasitic parameters, resulting in high-frequency resonance disturbances. The DC bus status high-frequency sensing unit samples the DC bus voltage and current through Hall voltage and Hall current sensors. The sampling triggering time of the dual-channel synchronous analog-to-digital converter is hardware synchronized with the apex and basal point of the inverter switch modulating the symmetrical triangular carrier wave. The transient voltage and current signals of the DC bus are obtained at a sampling frequency of 20kHz, corresponding to a single switching cycle of 50μs. The synchronous sampling results are then sent to the subsequent control loop.

[0075] The bus multi-band harmonic decomposition and disturbance decoupling unit obtains the DC voltage reference deviation, characteristic secondary pulsation ripple component, and high-frequency resonance disturbance component based on the DC bus transient voltage signal. The virtual damped resonance active suppression unit processes the three-phase inverter output current according to the resonance frequency band corresponding to the high-frequency resonance disturbance component, forming a virtual damped voltage compensation component in a two-phase stationary coordinate system. As a result, the DC bus reference change, low-frequency pulsation, and high-frequency resonance under the grid-side overvoltage spurt condition are respectively entered into the corresponding control channels, and the processing flow of each control channel is consistent with the aforementioned embodiment.

[0076] The dynamic modulation timing reconstruction and harmonic offset unit obtains the transient feedforward compensation coefficient based on the ratio of the nominal value of the 540V rated DC voltage to the transient voltage signal of the 594V DC bus in the current sampling period, and combines it with the current fundamental frequency rotation electrical angle and a harmonic offset gain coefficient of 0.08. A reverse offset component is generated in a two-phase stationary coordinate system. After the basic phase voltage control command in the two-phase stationary coordinate system is determined, the basic phase voltage control command is added to the virtual damped voltage compensation component, multiplied by the transient feedforward compensation coefficient, and the reverse offset component is subtracted to obtain the corrected synthetic voltage command and the corresponding synthetic vector amplitude. The synthetic vector amplitude is within the maximum linear modulation region corresponding to the transient voltage of the 594V DC bus. Therefore, the modulation ratio linear boundary clamping module does not perform super-boundary scaling. The dynamic modulation timing reconstruction and harmonic offset unit directly calculates the first effective working vector discrete action time, the second effective working vector discrete action time, and the zero vector total action time based on the geometric projection of the synthetic voltage command in the directions of the two adjacent basic working vectors in the first sector.

[0077] Within a single 50μs switching cycle, the action time of each vector is allocated according to a symmetrical seven-segment timing sequence: the initial segment allocates the basic zero vector, followed by the first and second effective working vectors in sequence, the complementary zero vector is allocated in the middle segment of the cycle, and then the second, first, and tail zero vectors are allocated in the second half of the cycle in a mirror sequence, so that all discrete action times remain closed with the switching cycle. When the grid-side voltage rises and the load is stable, the DC voltage reference deviation and characteristic secondary ripple components are fed into the synthesized voltage command through the transient feedforward compensation coefficient and the reverse offset component. The virtual damped voltage compensation component corresponding to the high-frequency resonance disturbance also participates in the modulation. The symmetrical seven-segment vector action time allocation maintains the volt-second balance and phase relationship of the output voltage vector, the phase current waveform of the three-phase inverter power output unit remains symmetrical, the total harmonic distortion rate of the phase current is within the controlled range, and the electromagnetic torque ripple is suppressed.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. A harmonic suppression and voltage regulation system for a variable frequency drive, characterized in that, include: The three-phase rectifier and filter topology unit connects to the AC power grid at the AC end and to the DC bus at the DC end for outputting DC power. The DC bus status high-frequency sensing unit has its sampling end connected to the DC bus and is used to collect the DC bus transient voltage signal and DC bus transient current signal. The bus multi-band harmonic decomposition and disturbance decoupling unit, connected to the DC bus status high-frequency sensing unit, is used to decouple the DC bus transient voltage signal by frequency division and output the DC voltage reference deviation, characteristic secondary pulsation ripple component, and high-frequency resonant disturbance component. The bus multi-band harmonic decomposition and disturbance decoupling unit includes: a DC deviation extraction module, used to calculate the average value of the DC bus transient voltage within the fundamental frequency period based on a moving average filter window, and to subtract the average value of the DC bus transient voltage from the nominal value of the rated DC voltage to output the DC voltage reference deviation; a harmonic quadrature extraction module, used to filter the DC bus transient voltage signal in the discrete time domain based on a parallel second-order generalized integrator, separating the second-order pulsation component and the sixth-order pulsation component, and superimposing them to generate the characteristic secondary pulsation ripple component; and a high-frequency resonant capture module, used to extract the fluctuation signal falling within the inductor-capacitor resonant frequency band of the DC bus transient voltage signal through a digital bandpass filter, and output the high-frequency resonant disturbance component. The virtual damped resonance active suppression unit, connected to the bus multi-band harmonic decomposition and disturbance decoupling unit, is used to generate virtual damped voltage compensation components in the stationary coordinate system based on the high-frequency resonance disturbance components. The dynamic modulation timing reconstruction and harmonic offset unit is connected to the bus multi-band harmonic decomposition and disturbance decoupling unit and the virtual damping resonance active suppression unit, respectively. It is used to generate transient feedforward compensation coefficient based on the ratio of the rated DC voltage nominal value to the DC bus transient voltage signal, generate reverse offset component based on the characteristic sub-pulse ripple component, add the basic phase voltage control command and the virtual damping voltage compensation component, multiply by the transient feedforward compensation coefficient, and then subtract the reverse offset component to generate the synthesized voltage command. Based on this, the discrete action time of the effective working vector and the zero vector is calculated and the switching drive pulse signal is output. The three-phase inverter power output unit connects to the DC bus at the DC end, receives switch drive pulse signals at the control end, and connects to the controlled electric drive load at the AC end.

2. The frequency converter driver harmonic suppression and voltage regulation system according to claim 1, characterized in that, The three-phase rectifier filter topology unit includes a three-phase uncontrolled rectifier bridge and a group of smoothing inductors and electrolytic capacitors. The filter network has an inductance of 0.8mH for the smoothing inductor and a total capacitance of 1500μF for the electrolytic capacitor bank. The DC bus status high-frequency sensing unit includes a Hall voltage sensor, a Hall current sensor, and a dual-channel synchronous analog-to-digital converter. The sampling trigger terminal of the dual-channel synchronous analog-to-digital converter is hardware-synchronized and locked with the apex and basal point of the pulse width modulation symmetrical triangular carrier of the three-phase inverter power output unit. The sampling frequency is configured to be 20kHz.

3. The frequency converter driver harmonic suppression and voltage regulation system according to claim 1, characterized in that, The virtual damped resonance active suppression unit includes: a current resonance extraction module, used to acquire the three-phase inverter output current and convert it to a synchronous rotating coordinate system, extracting the current resonance within it. High-frequency resonant current components of the shaft and Shaft high-frequency resonant current component; damping voltage calculation module, used to calculate... High-frequency resonant current components of the shaft and The high-frequency resonant current component of the shaft is multiplied by a preset virtual damping coefficient to generate a negative feedback damping compensation voltage in a synchronous rotating coordinate system. The coordinate inverse transformation module is used to convert the negative feedback damping compensation voltage into a virtual damping voltage compensation component in a two-phase stationary coordinate system, so that the input admittance of the three-phase inverter power output unit at the system resonant frequency band exhibits positive resistance.

4. The frequency converter driver harmonic suppression and voltage regulation system according to claim 1, characterized in that, The dynamic modulation timing reconstruction and harmonic offsetting unit calculates the discrete action time of adjacent first effective working vectors, the discrete action time of second effective working vectors, and the total action time of zero vectors within a single switching cycle based on the geometric projection of the synthesized voltage command onto the base vector of the target sector. It then allocates the action time of each vector according to a symmetrical seven-segment timing sequence: one-quarter of the total zero vector action time is allocated in the initial segment of a single switching cycle; half of the discrete action time of the first effective working vector and half of the discrete action time of the second effective working vector are allocated immediately adjacent to it; half of the total zero vector action time is allocated in the middle segment of the cycle; and half of the discrete action time of the second effective working vector, half of the discrete action time of the first effective working vector, and one-quarter of the total zero vector action time are sequentially mirrored in the symmetrical subsequent segment.

5. The frequency converter driver harmonic suppression and voltage regulation system according to claim 1, characterized in that, The digital bandpass filter in the high-frequency resonant capture module is a fourth-order Butterworth digital bandpass filter with a passband frequency range of 800Hz to 3500Hz, a passband attenuation of less than 0.5dB, and a stopband attenuation of greater than 40dB. It is used to filter out DC steady-state components and pulsating ripples below 800Hz.

6. The frequency converter driver harmonic suppression and voltage regulation system according to claim 3, characterized in that, The virtual damping coefficient is set in the range of 1.0Ω to 2.0Ω, and the current resonance extraction module includes a lead-lag phase correction stage when extracting the high-frequency resonant current component to compensate for the phase influence of the sampling calculation delay on the positive resistive damping characteristics.

7. The frequency converter driver harmonic suppression and voltage regulation system according to claim 1, characterized in that, The dynamic modulation timing reconstruction and harmonic offset unit also includes a modulation ratio linear boundary clamping module. When the synthesized voltage command exceeds the maximum linear modulation boundary determined by the transient voltage signal of the DC bus, the discrete action time of each effective working vector is scaled up by the same proportion, and the action time of the zero vector is amplified accordingly.

8. The frequency converter driver harmonic suppression and voltage regulation system according to claim 1, characterized in that, The three-phase inverter power output unit operates in an ambient temperature range of -40℃ to 60℃ and the voltage fluctuation range of the three-phase AC grid is within the range of -20% to +20% of the rated voltage. When the transient voltage signal of the DC bus suddenly drops, the dynamic modulation timing reconstruction and harmonic offset unit increases the transient feedforward compensation coefficient to compensate for the impact of the DC bus voltage drop on the amplitude of the output fundamental voltage. At the same time, the virtual damping resonance active suppression unit suppresses the high-frequency series resonance overvoltage caused by the smoothing inductor and electrolytic capacitor bank.

9. A method for harmonic suppression and voltage regulation of a variable frequency drive, used to operate the harmonic suppression and voltage regulation system of a variable frequency drive as described in claim 1, characterized in that, Includes the following steps: Step S1: The AC power is converted into DC power containing DC voltage and ripple components through a three-phase rectifier and filter topology unit, and the transient voltage signal and transient current signal of the DC bus are synchronously acquired through a DC bus status high-frequency sensing unit. Step S2 involves using a multi-band harmonic decomposition and disturbance decoupling unit to decouple the DC bus transient voltage signal by frequency division, outputting the DC voltage reference deviation, characteristic secondary ripple component, and high-frequency resonant disturbance component. Specifically, the average DC bus transient voltage within the fundamental frequency cycle is calculated using a moving average filter window, and the difference between the average DC bus transient voltage and the nominal DC voltage value is used to output the DC voltage reference deviation. A parallel second-order generalized integrator filters the DC bus transient voltage signal in the discrete time domain, separating the second-order and sixth-order ripple components, which are then superimposed to generate the characteristic secondary ripple component. A digital bandpass filter extracts the fluctuation signal falling within the inductor-capacitor resonant frequency band of the DC bus transient voltage signal, outputting the high-frequency resonant disturbance component. Step S3: The virtual damping voltage compensation component in the two-phase stationary coordinate system is generated by the virtual damping resonance active suppression unit based on the high-frequency resonance disturbance component. Step S4: Through the dynamic modulation timing reconstruction and harmonic offset unit, the ratio of the nominal value of the rated DC voltage to the transient voltage signal of the DC bus is calculated to generate the transient feedforward compensation coefficient. The reverse offset component is generated based on the characteristic sub-pulse ripple component. The basic phase voltage control command and the virtual damping voltage compensation component are added together and multiplied by the transient feedforward compensation coefficient. Then, the reverse offset component is subtracted to generate the composite voltage command. The discrete action time of the effective working vector and the zero vector is calculated based on the composite voltage command, and the switch drive pulse signal is output. Step S5: The three-phase inverter power output unit receives the switch drive pulse signal, converts the electrical energy of the DC bus into three-phase AC power, and supplies it to the controlled electric drive load.

Images