A method for suppressing secondary ripple voltage of a single-phase PWM rectifier control system with parameter adaptation

Abstract

This invention discloses a method for suppressing secondary ripple voltage in a single-phase PWM rectifier control system with parameter adaptation, comprising the following steps: A. After the rectifier enters a steady state, the output DC voltage V of the rectifier is acquired using a voltage sensor. dc Compare this voltage with the DC voltage reference value V. dcref By taking the difference, the DC voltage deviation value V with secondary ripple voltage can be obtained. dce The estimated value of the secondary ripple voltage V of the control system dcs B. The DC voltage deviation value V is calculated in real time by the system. dce A quarter-cycle delay yields the orthogonal DC voltage deviation value V. dceβ Then, the amplitude V of the DC output voltage deviation is calculated. dcep Similarly, the estimated value of the secondary ripple voltage V of the control system is... dcs A quarter-cycle delay yields the orthogonal quadratic ripple voltage estimate V. dcsβ Then, the amplitude V of the estimated secondary pulsating voltage is calculated. dcsp C. Compare V dcep With V dcsp The size of V dcep Greater than V dcsp When V increases, the feedback gain k value is increased; when V increases, the feedback gain k value is increased. dcep Less than V dcsp At this time, the feedback gain k is reduced. The optimal value of k is selected using the perturbation-observation method; considering the volatility of the dynamic system, hysteresis control with a loop width of h can suppress k. o The impact of voltage fluctuations. Based on numerical calculations, this invention introduces the control concept of the disturbance observation method. Through adaptive adjustment of the feedback coefficient k, it achieves real-time compensation for grid-side voltage fluctuations and capacitor parameters, ensuring the suppression effect of secondary pulsating voltage in the control system.

Description

Technical Field

[0001] This invention relates to a method for suppressing secondary ripple voltage in a single-phase PWM rectifier control system with adaptive parameters. Specifically, it relates to a method in a single-phase PWM rectifier control system that estimates the magnitude of the secondary ripple voltage and whose proportional coefficient for estimating the secondary ripple voltage can be dynamically adjusted. Background Technology

[0002] Due to its advantages such as unity power factor on the AC side, stable DC voltage, bidirectional energy flow, and low grid-side current harmonics, PWM rectifiers are widely used in superconducting energy storage, railway locomotive traction, grid-connected solar power generation, and uninterruptible power supplies (UPS). For single-phase PWM rectifiers, the inherent secondary voltage ripple in the system causes even-order voltage ripple on the output side to generate odd-order current ripple on the input side, and vice versa. The most significant issues are the second harmonic voltage on the output side and the third harmonic current on the input side. Excessive AC current distortion can severely impact the power quality of the grid, leading to problems such as harmonic pollution and voltage fluctuations. Therefore, suppressing the secondary ripple of single-phase PWM rectifiers and reducing grid-side current harmonics to minimize their impact on grid power quality has become a research hotspot. Existing improvement methods include hardware and software approaches. Hardware improvements include using LC filters to provide a low-impedance path for secondary ripple, but this increases the weight and size of the rectifier. Active filtering circuits are also used to compensate for secondary voltage pulsations, but this increases control complexity, complicates physical connections, and reduces power density. Software control methods include adding low-pass filters to the voltage loop or notch filters to the voltage sampling side. These methods reduce the bandwidth of the voltage loop, decreasing the fast response performance of the single-phase PWM rectifier. In applications with frequent load power switching, such as microprocessors and communication equipment, this can lead to large fluctuations in DC-side voltage and slow response. Numerical calculation methods are also used, obtaining the magnitude of the secondary voltage ripple from power conservation and subtracting this value at the sampling side. However, this method is challenging because the control system is affected by the capacitance value, requiring accurate capacitance measurement. This invention, based on numerical calculations, introduces the disturbance observation method. Through adaptive adjustment of the feedback coefficient k, it achieves real-time compensation for grid-side voltage fluctuations and capacitance parameters, ensuring the suppression effect of the secondary voltage pulsation in the control system. Summary of the Invention

[0003] This invention provides a method for suppressing secondary ripple voltage in a single-phase PWM rectifier control system with adaptive parameters. This invention achieves the effect of automatically adjusting parameters and achieving optimal matching of system parameters without reducing the voltage loop bandwidth, suppressing the impact of secondary ripple voltage on the single-phase PWM rectifier control system, reducing the THD of the input current, and improving power quality. A method for suppressing secondary ripple voltage in a single-phase PWM rectifier control system with parameter adaptation, such as... Figure 3 As shown, V dc The rectifier outputs DC voltage, V dcref V is the DC reference voltage output by the rectifier. dce V represents the DC voltage deviation value. dcs I is the estimated value of the secondary ripple voltage of the control system. ref I is the reference amplitude of the inductor current. L The actual value of the inductor current, phase ωt and 2 L, R, and C are derived from phase-locked loop (PLL) locking, and are respectively the input inductance, inductor equivalent resistance, and supporting capacitance of the single-phase PWM regulator. The feature includes the following steps: A. After the rectifier reaches steady state, the output voltage V of the rectifier is collected using a voltage sensor. dc Compare this voltage with the DC voltage reference value V. dcref By taking the difference, the DC voltage deviation value V with secondary ripple voltage can be obtained. dce The estimated value of the secondary ripple voltage V of the control system dcs Calculated in real time by the system; B. The DC voltage deviation value V dce The orthogonal output voltage deviation value V is obtained by delaying by a quarter cycle. dceβ At this time, the amplitude V of the DC output voltage deviation value dcep The following calculation method can be used to obtain: ; (1) Similarly, the estimated value of the secondary ripple voltage V of the control system dcs A quarter-cycle delay yields the orthogonal quadratic output ripple estimation voltage value V. dcsβ At this time, the amplitude V of the estimated secondary ripple voltage is dcsp The following calculation method can be used to obtain: ; (2) C. Compare V dcep With V dcsp The size of V dcep Greater than V dcsp When V increases, the feedback gain k value is increased; when V increases, the feedback gain k value is increased. dcep Less than V dcsp When the system reaches its optimal value, the feedback gain k is reduced. The optimal value k is selected using the perturbation-observation method. oAt that time, the following conditions are met: V dcep = V dcsp ; (3) Considering the volatility of dynamic systems, rectifiers cannot operate constantly at the static steady point k. o At this point, the optimal value algorithm will lead to k o The constant fluctuation of the value can have an adverse effect on the system. Hysteresis control can suppress k. o The influence of value fluctuations leads to a hysteresis loop width of h, at which point the optimal k is found. o The value should satisfy: (4). In this context, an excessively large hysteresis loop width h will lead to a poorer secondary ripple voltage compensation effect, while an excessively small h will cause the dynamic process k0 value to fluctuate back and forth, affecting the control system. The value of h is determined based on simulation or experimentation. Simulation verification shows that the value of h is taken as the amplitude V of the DC output voltage deviation. dcep Approximately 3%. D. When the operating conditions of the system change, causing the absolute value of the secondary ripple voltage amplitude error to be greater than the set value h, the above steps can be repeated to make the system work in the optimal state again. The beneficial effect of this invention is that it can automatically adjust the secondary pulsation voltage proportional adjustment coefficient, search for the optimal value and complete the setting, so as to achieve the best suppression of the secondary pulsation voltage of the rectifier system under conditions such as input voltage change and capacitor parameter mismatch. Attached Figure Description

[0004] Figure 1 This is the main circuit of a single-phase PWM rectifier. Figure 2 This is a system block diagram for suppressing secondary ripple voltage in a traditional single-phase PWM rectifier control system. The steps of the traditional control method are as follows: The output voltage V... dc Secondary and higher ripples are filtered out by a low-pass filter, and then compared with the voltage reference value V. dcref The voltage error signal is obtained by subtraction, which is then input to the voltage controller to obtain the reference current amplitude. This amplitude is then multiplied by the phase signal obtained from the phase-locked loop to obtain the current reference value I. ref Current reference value I ref Compared with the actual current value I L The current error signal is obtained by subtraction, and the error signal is input to the current controller. Finally, the control signal of the single-phase PWM rectifier is generated by comparing it with the carrier wave. Figure 3 The system block diagram for suppressing secondary ripple voltage in the control system using the proposed single-phase PWM rectifier with adaptive parameters is shown. Figure 4The flowchart shows the calculation process for the feedback gain k value. Detailed Implementation

[0005] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. like Figure 3 As shown, V dc The rectifier outputs DC voltage, V dcref V is the DC reference voltage output by the rectifier. dce V represents the DC voltage deviation value. dcs I is the estimated value of the secondary ripple voltage of the control system. ref I is the reference amplitude of the inductor current. L The actual value of the inductor current, ωt and L, R, and C are derived from phase-locked loop (PLL) locking, representing the input inductance, inductor equivalent resistance, and supporting capacitance of a single-phase PWM rectifier, respectively. The feature includes the following steps: A. After the rectifier reaches steady state, the output voltage V of the rectifier is collected using a voltage sensor. dc Subtract the voltage reference value V from the voltage. dcref The DC voltage deviation value V with secondary ripple voltage can be obtained. dce The estimated value of the secondary ripple voltage V of the control system dcs The system calculates it; B. The power supply phase ωt is obtained by phase-locked loop and the phase 2ωt of the secondary ripple voltage compensation is calculated. The specific derivation process is as follows: Let the instantaneous values ​​of the power supply voltage and current be u, respectively. s i s Then we have: ; (1) ; (2) In the formula, U s I is the effective value of the power supply voltage. s The current is the effective value of the power supply current, and σ is the angle between the grid-side voltage and current. When operating in rectifier mode, σ is 0. The instantaneous power on the AC side of a single-phase PWM rectifier. It can be represented as: ; (3) Output voltage Decomposed into DC component and second harmonic AC component The instantaneous output power of the DC side of the single-phase PWM rectifier is... It can be represented as: ; (4) From the law of conservation of power, we can obtain: ; (5) For second harmonic power: ; (6) When operating in rectifier mode, the angle σ between the grid-side voltage and current is 0. Simplifying this formula yields the secondary ripple voltage that should be compensated. : ; (7) in This represents the load current value. DC voltage deviation value V dce ( The orthogonal DC voltage deviation value V is obtained by delaying it by a quarter cycle. dceβ At this time, the amplitude V of the DC voltage deviation value dcep The following calculation method can be used to obtain: ; (8) Similarly, the estimated value of the secondary ripple voltage V of the control system dcs ( The orthogonal quadratic ripple voltage estimate V is obtained by delaying the voltage by a quarter period. dcsβ At this time, the amplitude V of the estimated secondary ripple voltage is dcsp The following calculation method can be used to obtain: (9). C. Compare V dcep With V dcsp The size of V dcep Greater than V dcsp When V increases, the feedback gain k value is increased; when V increases, the feedback gain k value is increased. dcep Less than V dcsp When V decreases, the feedback gain k value is reduced. dcep equals V dcsp At that time, achieve the optimal k o The selection of values ​​for k. At this point... o The value theory derivation is as follows: When the converter operates in a stable rectification state, ignoring the intermediate losses and secondary voltage ripple, power conservation yields: ; (10) Simplifying the above equation, we get: ; (11) The above formula Substitute into the secondary ripple voltage type middle: ;(12) We can obtain: ; (13) ;(14) Where k o The optimal feedback coefficient is achieved when the system is in a steady state. It can be replaced with At this point, the expression becomes: ; (15) Considering the volatility of dynamic systems, rectifiers cannot operate constantly at the static steady point k. o The value, at which point the optimal value algorithm will lead to k o The constant fluctuation of the value can have an adverse effect on the system. Hysteresis control can suppress k. o The influence of value fluctuations leads to a hysteresis loop width of h, at which point the optimal k is found. o The value should satisfy: ; (16) In this context, an excessively large hysteresis loop width h will lead to a poorer secondary ripple voltage compensation effect, while an excessively small h will cause the dynamic process k0 value to fluctuate back and forth, affecting the control system. The value of h is determined based on simulation or experimentation. Simulation verification shows that the value of h is taken as the amplitude V of the DC output voltage deviation. dcep Approximately 3%, and the increment of the feedback gain k It should satisfy the following expression: (17). Where T s This refers to the unit of time for the system program to run in steps. This invention achieves optimal suppression of secondary ripple voltage in the rectifier system under conditions such as input voltage variation and capacitor parameter mismatch without reducing the voltage loop bandwidth. It searches for the optimal value and completes the setting by automatically adjusting the secondary ripple voltage proportional adjustment coefficient.

Claims

1. A method for suppressing secondary ripple voltage in a single-phase PWM rectifier control system with parameter adaptation, characterized in that, The proportional coefficient of the secondary pulsating voltage used for control system estimation has a parameter self-adaptation function and can automatically adjust to achieve optimal compensation. The implementation steps are as follows: A. After the rectifier reaches steady state, the output DC voltage V of the rectifier is collected using a voltage sensor. dc Compare this voltage with the DC voltage reference value V. dcref By taking the difference, the DC voltage deviation value V with secondary ripple voltage can be obtained. dce The estimated value of the secondary ripple voltage V of the control system dcs Calculated in real time by the system; B. The DC voltage deviation value V dce A quarter-cycle delay yields the orthogonal DC voltage deviation value V. dceβ At this time, the amplitude V of the DC output voltage deviation value dcep The following calculation method can be used to obtain: ； （1） Similarly, the estimated value of the secondary ripple voltage V of the control system dcs A quarter-cycle delay yields the orthogonal quadratic ripple voltage estimate V. dcsβ At this time, the amplitude V of the estimated secondary pulsating voltage is dcsp The following calculation method can be used to obtain: ； （2） C. Compare V dcep With V dcsp The size of V dcep Greater than V dcsp When V increases, the feedback gain k value is increased; when V increases, the feedback gain k value is increased. dcep Less than V dcsp When the system reaches its optimal value, reduce the feedback gain k; use the perturbation-observation method to select the optimal value k; when the system achieves the optimal value k... o At that time, the following conditions are met: V dcep =V dcsp ; (3) Considering the volatility of dynamic systems, rectifiers cannot operate constantly at the static steady point k. o At this point, the optimal value algorithm will lead to k o The value fluctuates continuously, which has an adverse effect on the system. Hysteresis control can suppress k. o The influence of value fluctuations leads to the optimal value k when the hysteresis loop width is h. o The value of should satisfy: ; （4） In this context, an excessively large hysteresis loop width h will lead to a poorer secondary ripple voltage compensation effect, while an excessively small h will cause the dynamic process k0 value to fluctuate back and forth, affecting the control system. The value of h is determined based on simulation or experimentation. Simulation verification shows that the value of h is taken as the DC output voltage deviation amplitude V. dcep Around 3%; D. When the operating conditions of the system change, causing the absolute value of the secondary ripple voltage amplitude error to exceed the set value h, repeat the above steps to make the system work again in the optimal state.

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