Capacitive current feed-forward-based system for accelerating load abrupt change response of rectifier

Abstract

The utility model discloses a system for accelerating load abrupt change response of a rectifier based on capacitor current feedforward. The system comprises a control module, a capacitor voltage sampling module, an inductive current sampling module, a PWM modulation module and a power circuit module. When the load suddenly increases, the capacitor rapidly discharges, and the current suddenly changes in the negative direction; when the load suddenly decreases, the capacitor is rapidly charged, and the current suddenly changes in the positive direction; second harmonics exist in the Ic obtained through calculation, the second harmonics are filtered out through a notch filter, a current absolute value threshold t after filtering is set, and sudden change of the load is judged. The abrupt change of the load is judged through the abrupt change of the capacitive current, and the capacitive current is directly fed forward into the integrator of the PI controller, so that the abrupt change of the load can be quickly detected, the current reference value can be quickly adjusted, and the charging and discharging of the capacitor can be inhibited.

Description

TECHNICAL FIELD

[0001] The utility model relates to a rectification technology of switching power supply especially relates to a system of accelerating rectifier load mutation response based on capacitor current feedforward. BACKGROUND

[0002] In the input stage of switching power supply, AC-DC conversion, also known as rectification, is generally required, and the topology architecture of the rectifier is as shown in the figure. Figure 1

[0003] When the input stage of the power supply adopts uncontrolled rectification, although the circuit operation mode is simple, the uncontrollability of the diode leads to that the input current is not a sine wave and contains a large number of harmonic components, the power factor of the circuit is reduced, and the output voltage is not adjustable. Therefore, the rectifier is generally controlled to realize the improvement of the power factor and the adjustment of the output voltage.

[0004] As shown in the figure, the classical rectifier control loop is an output voltage-inductor current double proportional-integral (PI) controller closed loop, and the controller is a proportional element and an integral element in parallel. Figure 2 The output end of the rectifier needs to be designed with a large capacitor for voltage stabilization and filtering. When the load mutates, the loop control is not timely, the capacitor is rapidly charged and discharged, which can cause the DC bus voltage to rise or drop greatly, and the recovery time is relatively long, which can affect the normal work of the electrical equipment, so some means need to be taken to accelerate the load mutation response of the rectifier.

[0005] Prior art and defects:

[0006] The prior art detects the rise and fall of the output voltage to judge the sudden decrease and increase of the load, and then increases the gain of the voltage PI controller to increase the current reference value. This method can accelerate the load mutation response to a certain extent, but this method cannot detect the load mutation in time, and only takes measures after the load mutation has a certain impact. Moreover, increasing the gain of the controller cannot accurately compensate the current reference value, and also raises the cutoff frequency of the loop, reducing the stability of the system.

[0007] In view of the above problems in the prior art, the utility model is provided.

[0008] Utility model content The utility model relates to a rectification technology of switching power supply especially relates to a system of accelerating rectifier load mutation response based on capacitor current feedforward.

[0009] The utility model aims to solve the above technical problems in the prior art by providing a system of accelerating rectifier load mutation response based on capacitor current feedforward.

[0010] The utility model aims to realize the following technical scheme:

[0011] ​The utility model discloses based on the system of capacitor current feedforward of accelerating rectifier load mutation response, including control module, the input of control module is connected with capacitor voltage sampling module and inductance current sampling module, the output of control module is connected with PWM modulation module and power circuit module in proper order.

[0012] Compared with prior art, the system of accelerating rectifier load mutation response based on capacitor current feedforward provided by the utility model judges the mutation of load through the mutation of capacitor current, and directly feeds forward capacitor current into integrator of PI controller, and this mode can quickly detect the mutation of load, and simultaneously quickly adjusts current reference value, and inhibits the charge and discharge of capacitor. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 For prior art rectifier topology structure,

[0014] Figure 2 For prior art rectifier control loop,

[0015] Figure 3 For the flow schematic diagram of the utility model embodiment,

[0016] Figure 4 For the simulation experiment sudden load response of the scheme proposed in the utility model, Figure 1 ;

[0017] Figure 5 For the simulation experiment sudden load response of the scheme proposed in the utility model, Figure 2 ;

[0018] Figure 6 For the system topology graph of the utility model embodiment. DETAILED DESCRIPTION

[0019] The technical scheme in the utility model embodiment is clearly and completely described below with reference to the drawings in the utility model embodiment; obviously, the described embodiment is only a part of the embodiment of the utility model, not all the embodiment, and this does not constitute the limitation of the utility model. Based on the embodiment of the utility model, all other embodiments obtained by the ordinary skill in the art without creative labor belong to the protection scope of the utility model.

[0020] Firstly, the terms possibly used in the paper are explained as follows:

[0021] The term "and / or" means either one or both, for example, X and / or Y means three cases including "X", "Y" or "X and Y".

[0022] The terms "comprise", "include", "contain", "have" or other similar semantic descriptions should be interpreted as non-exclusive inclusion. For example: including a technical feature element (such as raw materials, components, ingredients, carriers, dosage forms, materials, sizes, parts, components, mechanisms, devices, steps, processes, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products or articles, etc.) should be interpreted as not only including the explicitly listed technical feature element, but also including other technical feature elements not explicitly listed in the art.

[0023] The term "consisting of" means excluding any technical feature element not explicitly listed. If this term is used in the claims, the term will make the claim closed, so that it does not contain technical feature elements other than the explicitly listed technical feature elements, except for conventional impurities related thereto. If the term only appears in a certain clause of the claim, it only limits the elements explicitly listed in that clause, and the elements described in other clauses are not excluded from the overall claim.

[0024] The contents not described in detail in the embodiments of the present application are the prior art known to those skilled in the art. The embodiments of the present application are not marked with specific conditions, and are carried out according to the conventional conditions in the art or the conditions recommended by the manufacturer. The reagents or instruments used in the embodiments of the present application are not marked with the manufacturer, and are all conventional products that can be purchased on the market.

[0025] The system for accelerating rectifier load mutation response based on capacitor current feedforward, comprising a control module, a capacitor voltage sampling module and an inductance current sampling module are connected to the input end of the control module, and a PWM modulation module and a power circuit module are connected to the output end of the control module in turn.

[0026] The control module comprises a capacitor current Ic calculation unit, a capacitor current notch filter Ic' unit, a recording steady-state capacitor current Istab unit, a filtered current absolute value threshold th judgment unit and an integrator.

[0027] The above-mentioned system for accelerating rectifier load mutation response based on capacitor current feedforward realizes the method for accelerating rectifier load mutation response, comprising:

[0028] When the load suddenly increases, the capacitor rapidly discharges, and the current suddenly changes in the negative direction; when the load suddenly decreases, the capacitor rapidly charges, and the current suddenly changes in the positive direction;

[0029] The calculation method of the capacitor current Ic is as follows:

[0030]

[0031] Wherein, Udc (n) is current interrupt period sampling voltage, Udc (n-1) is last period sampling voltage, Ts is interrupt period, C is capacitance value.

[0032] The calculated Ic has a second harmonic, and the second harmonic is filtered out using a notch filter, and the transfer function of the notch filter is as follows:

[0033]

[0034] Wherein, ζ1 and ζ2 are notch factors, ζ1 should be much smaller than ζ2, and ω0 is the center frequency of the notch.

[0035] Suppose that the capacitance current is Istab at steady state, the filtered capacitance current is Ic', and the absolute value threshold of the filtered current is set to th=1.3Istab, and if |Ic'|>th, it indicates that the load has a sudden change.

[0036] It also includes a capacitance current feedforward:

[0037] When the current of the capacitor changes, the reference value of the inductance current is compensated in time, so that the inductance current changes rapidly to suppress the change of the capacitance current.

[0038] Suppose that the capacitance current is Ic' when the load suddenly changes, then the capacitance current should be reduced by Ic', and if the output voltage is Udc and the input voltage effective value is Us, then the inductance current should be reduced by Ic'*Udc / Us considering 100% efficiency.

[0039] When the load suddenly increases, Ic'<0, the capacitance current will actually increase, and when the load suddenly decreases, Ic'>0, the capacitance current will actually decrease, and the change of the load is associated with the sign of Ic', and the two cases are uniformly processed.

[0040] The amount of capacitance current feedforward cannot be revoked, and it is fed forward into the integrator of the PI controller, and suppose that the output of the integrator is errorsum, after feedforward, errorsum=errorsum+Ic'*Udc / Us / Ki, because the errorsum has Ki times gain when the controller outputs, so when feedforward, the gain is offset to be the real current reference.

[0041] As can be seen from the above, the system for accelerating the response of the rectifier load mutation based on the capacitance current feedforward can quickly detect the mutation of the load by the mutation of the capacitance current, and directly feed forward the capacitance current into the integrator of the PI controller, which can quickly detect the mutation of the load and quickly adjust the current reference value to suppress the charging and discharging of the capacitor.

[0042] In order to more clearly demonstrate the technical solution and technical effects provided by the present invention, the embodiments of the present invention are described in detail below with reference to specific embodiments.

[0043] Example 1

[0044] like Figures 3 to 6 As shown:

[0045] 1. Description of the principle of this utility model:

[0046] 1. Load mutation detection

[0047] When the load increases suddenly, the capacitor discharges quickly. Figure 3 If the current is in the positive direction, the current suddenly changes to the negative direction. When the load suddenly decreases, the capacitor charges rapidly, and the current suddenly changes to the positive direction. The capacitor current Ic is calculated as shown in the following formula.

[0048]

[0049] Wherein, Udc(n) is the sampling voltage of the current interruption period, Udc(n-1) is the sampling voltage of the previous period, Ts is the interruption period, and C is the capacitance value.

[0050] Because Udc is obtained by rectifying AC voltage and is not a pure DC voltage, it contains the second harmonic of the AC voltage. Therefore, the calculated Ic also contains second harmonics. A notch filter is required to remove these second harmonics, otherwise the determination of current changes will be affected. The transfer function of the notch filter is shown below.

[0051]

[0052] Among them, ζ1 and ζ2 are notch factors, ζ1 should be much smaller than ζ2; ω0 is the notch center frequency.

[0053] Assuming that the capacitor current in steady state is Istab and the filtered capacitor current is Ic', the absolute value threshold of the filtered current th can be set to 1.3Istab. If |Ic'|>th, it means that the load has a sudden change.

[0054] 2. Capacitor current feedforward

[0055] The idea of capacitor current feedforward is that when the capacitor current changes, the reference value of inductor current is compensated in time to make the inductor current change rapidly to suppress the change of capacitor current. Assuming that the capacitor current is Ic' when the load changes suddenly, the capacitor current should be reduced by Ic', if the output voltage is Udc and the input voltage effective value is Us, and the efficiency is considered as 100%, then the inductor current should be reduced by Ic'*Udc / Us. When the load increases suddenly, Ic'<0, the capacitor current actually increases, and when the load decreases suddenly, Ic'>0, the capacitor current actually decreases, which is consistent with the compensation logic. It can be known that the change of the load is associated with the sign of Ic', and the two cases can be processed uniformly without special consideration.

[0056] The amount of capacitor current feedforward cannot be revoked, and once revoked, the sudden change of current reference will still occur, which does not conform to the original intention of suppressing the change of capacitor current, therefore, the feedforward is considered to be fed into the integrator of the PI controller, because the integrator is used at all times, so that the amount of feedforward is effective all the time. Assuming that the output of the integrator is errorsum, after feedforward, errorsum=errorsum+Ic'*Udc / Us / Ki, because errorsum has Ki times gain at the output of the controller, therefore, the gain should be offset at the time of feedforward to be the real current reference.

[0057] II. Detection and experimental verification

[0058] The simulation experiment is carried out on the scheme of the utility model, the simulation condition is that the output alternating voltage effective value is 90V, the output direct current voltage is 150V, and the 25Ω load is suddenly added from the no-load state or suddenly reduced from the 25Ω load to the no-load state.

[0059] The sudden load response is as shown in Figure 4 Before compensation, the maximum voltage drop value is 40V, and the voltage recovery time is 340ms; after compensation, the maximum voltage drop value is 20V, and the voltage recovery time is 170ms, which is equivalent to that the maximum voltage drop value and the voltage recovery time are reduced by 50%.

[0060] The sudden load response is as shown in Figure 5 Before compensation, the maximum voltage drop value is 40V, and the voltage recovery time is 340ms; after compensation, the maximum voltage drop value is 20V, and the voltage recovery time is 170ms, which is equivalent to that the maximum voltage drop value and the voltage recovery time are reduced by 50%.

[0061] The simulation results show that, whether for the sudden load or the sudden load reduction, the voltage change and the recovery time are greatly reduced after compensation, the system response is accelerated, which proves the effectiveness of the scheme of the utility model.

[0062] The above merely describes a preferred specific implementation of the present application, but the scope of protection of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be encompassed within the scope of protection of the present application. Therefore, the scope of protection of the present application should be subject to the scope of protection of the claims. The information disclosed in the background section of the present application is merely intended to deepen the understanding of the overall background technology of the present application, and should not be regarded as acknowledging or implying in any form that the information constitutes the prior art known to those skilled in the art.

Claims

1. A system for accelerating response to load step in a rectifier based on capacitive current feed forward, characterized by, The control module is connected with a capacitor voltage sampling module and an inductor current sampling module at the input end, and connected with a PWM modulation module and a power circuit module at the output end in sequence.

2. The system for accelerating response to load step in a rectifier based on capacitive current feed forward as claimed in claim 1, wherein, The control module comprises a capacitor current Ic calculation unit, a capacitor current trap filter Ic' unit, a unit for recording a steady-state capacitor current as Istab, a filter current absolute value threshold th judgment unit, and an integrator.

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