Capacitive current feed-forward-based system and method for accelerating load sudden change response of rectifier

Abstract

The invention discloses a system and a method for accelerating rectifier load abrupt change response 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 present invention relates to a rectification technology for a switching power supply, and in particular to a system and method for accelerating the response of a rectifier to a sudden load change based on capacitor current feedforward. Background Art

[0002] At the input stage of the switching power supply, AC-DC conversion is generally required, also known as rectification. The topology of the rectifier is as follows: Figure 1 shown.

[0003] When the input stage of a power supply uses uncontrolled rectification, although the circuit operation mode is simple, the uncontrollable nature of the diode causes the input current to be non-sinusoidal and contain a large number of harmonic components, which reduces the power factor of the circuit and makes the output voltage unadjustable. Therefore, the rectifier is generally controlled to achieve power factor improvement and output voltage regulation.

[0004] like Figure 2 As shown, the classic rectifier control loop is an output voltage-inductor current dual proportional-integral (PI) controller closed loop, where the controller is a proportional link and an integral link in parallel.

[0005] A large capacitor is required at the rectifier's output for voltage stabilization and filtering. If the load suddenly changes, the loop control is not timely, and the capacitor rapidly charges and discharges, causing the DC bus voltage to rise or fall sharply. This can also take a long time to recover, potentially affecting the normal operation of electrical equipment. Therefore, some method is needed to accelerate the rectifier's response to sudden load changes.

[0006] Existing technology and defects:

[0007] The existing technology determines the sudden decrease and increase of the load by detecting the rise and fall of the output voltage, and then increases the gain of the voltage PI controller to increase the current reference value. This method can speed up the response to the sudden load change to a certain extent, but this method cannot detect the sudden load change in time. Measures are only taken after the sudden load change has a certain impact. In addition, increasing the gain of the controller cannot accurately compensate for the current reference value, and it will also increase the cutoff frequency of the loop, reducing the stability of the system.

[0008] In view of this, the present invention is proposed. Summary of the Invention

[0009] The purpose of the present invention is to provide a system and method for accelerating the response of a rectifier to a sudden load change based on capacitor current feedforward, so as to solve the above-mentioned technical problems existing in the prior art.

[0010] The purpose of the present invention is achieved through the following technical solutions:

[0011] The system of the present invention for accelerating the sudden load response of a rectifier based on capacitor current feedforward includes a control module, the input end of the control module is connected to a capacitor voltage sampling module and an inductor current sampling module, and the output end of the control module is connected to a PWM modulation module and a power circuit module in sequence.

[0012] The above-mentioned system for accelerating the sudden load response of the rectifier based on capacitor current feedforward implements a method for accelerating the sudden load response of the rectifier, including:

[0013] When the load suddenly increases, the capacitor discharges rapidly and the current suddenly changes to a negative direction; when the load suddenly decreases, the capacitor charges rapidly and the current suddenly changes to a positive direction.

[0014] The calculation method of capacitor current Ic is as follows:

[0015]

[0016] 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.

[0017] Compared with the existing technology, the system and method provided by the present invention for accelerating the sudden change response of the rectifier load based on capacitor current feedforward judge the sudden change of the load through the sudden change of the capacitor current, and directly feed the capacitor current forward into the integrator of the PI controller. This method can quickly detect the sudden change of the load and quickly adjust the current reference value to suppress the charging and discharging of the capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a rectifier topology structure in the prior art;

[0019] Figure 2 It is a prior art rectifier control loop;

[0020] Figure 3 A schematic diagram of a flow chart of an embodiment of the present invention;

[0021] Figure 4 To simulate the sudden load response of the solution proposed by the present invention Figure 1 ;

[0022] Figure 5 To simulate the sudden load response of the solution proposed by the present invention Figure 2 ;

[0023] Figure 6 This is a system topology diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The following is a clear and complete description of the technical solutions in the embodiments of the present invention, in conjunction with the accompanying drawings. It is obvious that the described embodiments are only some of the embodiments of the present invention, not all of them, and do not constitute a limitation of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] First, the following terms may be used in this article:

[0026] The term “and / or” means that either or both of them can be realized at the same time. For example, X and / or Y includes both “X” or “Y” and “X and Y”.

[0027] The terms "include," "comprises," "contains," "has," or other similar expressions should be interpreted as non-exclusive. For example, "including certain technical features (such as raw materials, components, ingredients, carriers, dosage forms, materials, dimensions, parts, components, mechanisms, devices, steps, procedures, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products, or manufactured articles, etc.) should be interpreted as including not only the technical features explicitly listed, but also other technical features known in the art that are not explicitly listed.

[0028] The term "consisting of" excludes any technical features not explicitly listed. If used in a claim, this term renders the claim closed, excluding any technical features other than those explicitly listed, except for conventional impurities associated with them. If this term appears only in a clause of a claim, it limits only the elements explicitly listed in that clause; elements listed in other clauses are not excluded from the claim as a whole.

[0029] The contents not described in detail in the examples of the present invention belong to the prior art known to those skilled in the art. If specific conditions are not specified in the examples of the present invention, the methods are carried out according to conventional conditions in the art or the conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments used in the examples of the present invention are not specified, they are all conventional products that can be purchased commercially.

[0030] The system of the present invention for accelerating the sudden load response of a rectifier based on capacitor current feedforward includes a control module, the input end of the control module is connected to a capacitor voltage sampling module and an inductor current sampling module, and the output end of the control module is connected to a PWM modulation module and a power circuit module in sequence.

[0031] The control module includes a capacitor current Ic calculation unit, a capacitor current notch filter Ic' unit, a steady-state capacitor current recording unit Istab, a filtered current absolute value threshold th judgment unit and an integrator.

[0032] The above-mentioned system for accelerating the sudden load response of the rectifier based on capacitor current feedforward implements a method for accelerating the sudden load response of the rectifier, including:

[0033] When the load suddenly increases, the capacitor discharges rapidly and the current suddenly changes to a negative direction; when the load suddenly decreases, the capacitor charges rapidly and the current suddenly changes to a positive direction.

[0034] The calculation method of capacitor current Ic is as follows:

[0035]

[0036] 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.

[0037] The calculated Ic contains a second harmonic, which is removed using a notch filter. The transfer function of the notch filter is shown in the following equation:

[0038]

[0039] Among them, ζ1 and ζ2 are notch factors, ζ1 should be much smaller than ζ2; ω0 is the notch center frequency.

[0040] Assume that the capacitor current in steady state is Istab, the capacitor current after filtering is Ic', and set the absolute value threshold of the filtered current th = 1.3Istab. If |Ic'|>th, it means that the load has a sudden change.

[0041] Also includes capacitor current feedforward:

[0042] When the capacitor current changes, the reference value of the inductor current is compensated in time, so that the inductor current changes quickly to suppress the change of the capacitor current;

[0043] Assuming the capacitor current during a sudden load change is Ic', the capacitor current should be reduced by Ic'. If the output voltage is Udc and the effective value of the input voltage is Us, and assuming 100% efficiency, the inductor current should be reduced by Ic'*Udc / Us.

[0044] When the load suddenly increases, Ic'<0, the capacitor current will actually increase, and when the load suddenly decreases, Ic'>0, the capacitor current will actually decrease. The change in load is related to the sign of Ic', and these two situations are handled uniformly.

[0045] The amount of capacitor current feedforward cannot be canceled and is fed forward into the integrator of the PI controller. Assuming that the output of the integrator is errorsum, after feedforward, errorsum = errorsum + Ic'*Udc / Us / Ki. Because errorsum has a Ki times gain at the controller output, the true current reference is obtained by offsetting this part of the gain during feedforward.

[0046] In summary, the system and method for accelerating the sudden load response of a rectifier based on capacitor current feedforward according to the embodiments of the present invention judge the sudden load change by the sudden change of the capacitor current, and directly feed the capacitor current forward into the integrator of the PI controller. This method can quickly detect the sudden change of the load, and at the same time quickly adjust the current reference value to suppress the charging and discharging of the capacitor.

[0047] In order to more clearly demonstrate the technical solutions and technical effects provided by the present invention, the embodiments of the present invention are described in detail below with reference to specific embodiments.

[0048] Example 1

[0049] like Figures 3 to 6 As shown:

[0050] 1. Description of the principle of the present invention:

[0051] 1. Load mutation detection

[0052] 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.

[0053]

[0054] 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.

[0055] 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.

[0056]

[0057] Among them, ζ1 and ζ2 are notch factors, ζ1 should be much smaller than ζ2; ω0 is the notch center frequency.

[0058] 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.

[0059] 2. Capacitor current feedforward

[0060] The idea behind capacitor current feedforward is this: when the capacitor current changes, the reference value of the inductor current is compensated in a timely manner, causing the inductor current to change rapidly to suppress changes in the capacitor current. Assuming the capacitor current during a sudden load change is Ic', the capacitor current should be reduced by Ic'. If the output voltage is Udc and the effective value of the input voltage is Us, assuming 100% efficiency, the inductor current should be reduced by Ic'*Udc / Us. When the load suddenly increases, Ic'<0, the capacitor current will actually increase. When the load suddenly decreases, Ic'>0, the capacitor current will actually decrease. This is consistent with the compensation logic. It can be seen that the change in load is associated with the sign of Ic'. These two situations can be handled uniformly and do not require special consideration.

[0061] The amount of capacitor current feedforward cannot be revoked. Once revoked, it will still cause a sudden change in the current reference, which is not in line with the original intention of suppressing capacitor current changes. Therefore, it is considered to feed it forward into the integrator of the PI controller. Because the integrator is shared at all times, the amount of feedforward is permanently effective. Assuming the output of the integrator is errorsum, after feedforward, errorsum = errorsum + Ic' * Udc / Us / Ki. Because the errorsum has a Ki times gain at the controller output, this gain must be offset during feedforward to obtain the true current reference.

[0062] 2. Testing and experimental verification

[0063] A simulation experiment was conducted on the solution proposed in the present invention. The simulation conditions were an output AC voltage effective value of 90V, an output DC voltage of 150V, and a sudden addition of a 25Ω load from a no-load state or a sudden reduction of the load from 25Ω to no-load.

[0064] Sudden load response such as Figure 4 Before compensation, the maximum voltage drop was 40V and the voltage recovery time was 340ms. After compensation, the maximum voltage drop was 20V and the voltage recovery time was 170ms, which means that both the maximum voltage drop and the voltage recovery time were reduced by 50%.

[0065] Sudden load reduction response Figure 5 Before compensation, the maximum voltage overshoot was 75V and the voltage recovery time was 340ms. After compensation, the maximum voltage overshoot was 22V and the voltage recovery time was 250ms, which means that the maximum voltage overshoot was reduced by 70% and the voltage recovery time was reduced by 26%.

[0066] The simulation results show that, regardless of sudden loading or sudden unloading, the voltage variation and recovery time are greatly reduced after compensation, and the system response is accelerated, which proves the effectiveness of the solution proposed in the present invention.

[0067] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or any form of implication that the information constitutes prior art already known to those skilled in the art.

Claims

1. A system for accelerating the response of a rectifier to a sudden load change based on capacitor current feedforward, characterized in that: It comprises a control module, the input end of which is connected to a capacitor voltage sampling module and an inductor current sampling module, and the output end of which is connected to a PWM modulation module and a power circuit module in sequence.

2. The system for accelerating rectifier load sudden change response based on capacitor current feedforward according to claim 1, characterized in that: The control module includes a capacitor current Ic calculation unit, a capacitor current notch filter Ic' unit, a steady-state capacitor current recording unit Istab, a filtered current absolute value threshold th judgment unit and an integrator.

3. A method for accelerating the sudden change response of a rectifier load by using a system for accelerating the sudden change response of a rectifier load based on capacitor current feedforward as claimed in claim 1 or 2, characterized in that: include: When the load suddenly increases, the capacitor discharges rapidly and the current suddenly changes to a negative direction; when the load suddenly decreases, the capacitor charges rapidly and the current suddenly changes to a positive direction; The calculation method of capacitor current Ic is as follows: 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.

4. The method for accelerating the rectifier load sudden change response based on capacitor current feedforward according to claim 3 is characterized in that: The calculated Ic contains a second harmonic, which is filtered out using a notch filter. The transfer function of the notch filter is shown in the following formula: in, and is the notch factor, Should be much smaller than ω0 is the center frequency of the notch.

5. The method for accelerating the rectifier load sudden change response based on capacitor current feedforward according to claim 4, characterized in that: Assume that the capacitor current in steady state is Istab, the capacitor current after filtering is Ic', and set the absolute value threshold of the current after filtering th = 1.3Istab. If |Ic'|>th, it means that the load has a sudden change.

6. The method for accelerating the rectifier load sudden change response based on capacitor current feedforward according to claim 5, characterized in that: Also includes capacitor current feedforward: When the current of the capacitor changes, the reference value of the inductor current is compensated in time, so that the inductor current changes quickly to suppress the change of the capacitor current; Assuming that the capacitor current when the load changes suddenly is Ic', the capacitor current should be reduced by Ic'. If the output voltage is Udc and the effective value of the input voltage is Us, and the efficiency is 100%, the inductor current should be reduced by Ic'*Udc / Us.

7. The method for accelerating the rectifier load sudden change response based on capacitor current feedforward according to claim 6, characterized in that: When the load suddenly increases, Ic'<0, the capacitor current will actually increase, and when the load suddenly decreases, Ic'>0, the capacitor current will actually decrease. The change in load is associated with the sign of Ic', and these two situations are handled uniformly.

8. The method for accelerating the rectifier load sudden change response based on capacitor current feedforward according to claim 7, characterized in that: The amount of capacitor current feedforward cannot be cancelled, and it is fed forward into the integrator of the PI controller. 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 controller output, the real current reference is obtained by offsetting this part of the gain during feedforward.

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