阅读说明：本技术 一种解决pfc输入动态的可靠控制方法 (Reliable control method for solving PFC input dynamic ) 是由 付加友 张凯旋 李晨光 吴琼 踪成林 张煌玉 朱建国 于 2020-09-01 设计创作，主要内容包括：本发明提出的一种PFC输入动态的可靠控制方法,在传统的PFC控制环路中,加入输入电流的变化量ΔI作用于电流环最终的环路输出结果Piout,来抑制由输入电压跳变造成的电流尖峰；通过实时采样的输出电压波形,来识别输入电压跳变的类型,并且可通过不同的输入电压跳变类型切换相应的控制策略,本发明提出的在非过零点处和过零点处输入电压跳变的两种有效识别方法,有效抑制所有输入电压跳变产生的输入电流尖峰。(The invention provides a reliable control method of PFC input dynamics, in the traditional PFC control loop, the variable quantity delta I of the input current is added to act on the final loop output result Piout of the current loop, so as to restrain the current peak caused by the jump of the input voltage; the type of input voltage jump is identified through the output voltage waveform sampled in real time, and corresponding control strategies can be switched through different input voltage jump types.)

1. A kind of input dynamic control method of PFC circuit, output voltage waveform sampled in real time, come to discern the type of input voltage jump, and switch over the corresponding control strategy through different input voltage jump types, when discerning the input voltage jump, through calculating the change difference Δ I of the current beat Iin0 of the input current and sampling value Iin1 of the previous beat, multiply the compensation coefficient Kp by the Δ I value after getting positive and get the compensation quantity dIout of the loop, the output result Piout acting on the current loop directly, reduce the duty cycle of sending a wave immediately at the current beat, thus inhibit the input current spike that the input voltage jumps and produce; the compensation coefficient Kp depends on the rising slope of the input current and the attenuation speed of the output duty ratio, and the larger the Kp value is, the better the Kp value is on the premise of ensuring that the input current does not oscillate dynamically.

2. The control method of claim 1, wherein the type of input voltage transition comprises a type of input voltage transition at a non-zero crossing and a zero crossing.

3. The control method of claim 1, wherein obtaining an output result Piout with a loop compensation amount dout acting directly on the current loop comprises: and subtracting the input current variable compensation value from the loop output result of the current beat current loop to obtain a final control wave generation value.

4. The control method according to claim 1, wherein when the input voltage jump occurs in a non-zero-crossing region of the input voltage, the input voltage jump direction is determined by detecting that Δ VI of the input voltage has a sudden rise or a sudden fall, and a corresponding control strategy is triggered.

5. The control method according to claim 4, comprising:

(1) powering on a power supply module;

(2) initializing variables, namely clearing all input voltage Vin, an input voltage sampling value Vin1 of the previous beat, input current Iin, an input voltage effective value Vin _ rms, an input current effective value Iin _ rms, an input current peak value Iin _ pk before jumping and a loop output result Piout of a current loop;

(3) sampling the current input voltage Vin and the current input current Iin at a set sampling frequency f, and keeping the input voltage sampled value Vin1 of the previous beat;

(4) calculating an input voltage effective value Vin _ rms and an input current effective value Iin _ rms before the input voltage jumps by sampling all input voltage sampling values and input current sampling values in a power frequency period;

(5) by sampling the input voltage value of the current beat and the input voltage value of the last beat, if the input voltage variation | Vin-Vin1| is greater than or equal to the Vset value, the jump of the input voltage is judged;

(6) judging the jumping direction of the input voltage by comparing the amplitude of the current-beat sampling voltage of the input voltage with the amplitude of the previous-beat sampling voltage;

(7) - (8) when the | Vin | > | Vin1| is in a jump state, the input voltage jumps from a low voltage to a high voltage, and the actually required input current is smaller than the previous input current, so that the input current peak value Iin _ pk is calculated through the effective value Iin _ rms of the input current before the jump, and the input current after the jump is limited;

(9) - (10) when the current sampled input current value is greater than or equal to the input current peak value Iin _ pk before jumping, inputting a jumping identification mark Sd to 1, and finally controlling the wave generation value to be the subtraction of the input current variation compensation value from the loop output result of the current loop of the current beat, so that the current spike caused by the input voltage jumping from low voltage to high voltage can be immediately inhibited;

(11) - (12) when Vin < | Vin1| the input voltage jumps from high voltage to low voltage, the actually required input current will be larger than the previous input current, but smaller than the input current peak value corresponding to the minimum input voltage at the current input power,

namely: iin _ pk = 1.414 (Vin _ rms Iin _ rms/Vin _ min)

The input power before jumping in the formula is (Vin _ rms × Iin _ rms), and the allowed minimum input voltage is Vin _ min;

(13) - (14) when the current sampled input current value is greater than or equal to the calculated Iin _ pk, inputting a jump identification mark Sd to 1, and subtracting an input current variation compensation value from a loop output result of the current beat current loop to serve as a final control wave generation value, so that a current spike caused by the input voltage jumping from high voltage to low voltage can be immediately inhibited;

(15) - (16) using the Piout result as the wave duty ratio value of the PFC switch tube in the current beat.

6. The control method of claim 5, wherein the magnitude of the Vset value is related to a sampling frequency, and a change in sampling between two beats of the input voltage in a steady state is not greater than the Vset.

7. The control method according to claim 1, wherein when the jump of the input voltage is in the vicinity of the zero crossing point of the input voltage, the jump input voltage step Δ VII is small, the jump input voltage condition is identified by the input voltage peak value, and the input current spike is suppressed by the corresponding control strategy.

8. The control method according to claim 7, comprising:

(1) powering on a power supply module;

(2) initializing variables, namely resetting all the variables, namely resetting the input voltage Vin, the sampled value Vin1 of the input voltage of the previous beat, the input current Iin, the effective value Vin _ rms of the input voltage, the effective value Iin _ rms of the input current, the peak value Iin _ pk of the input current before jumping and the loop output result Piout of the current loop;

(3) sampling the current input voltage Vin and the current input current Iin at a set sampling frequency f, and keeping the input voltage sampled value Vin1 of the previous beat;

(4) by sampling all input voltage sampling values and input current sampling values in a power frequency (frequency) period, an input voltage effective value Vin _ rms and an input current effective value Iin _ rms before input voltage jumping can be calculated;

(5) when the current sampling value of the input voltage Vin is larger than or equal to the peak value 1.414 of the input voltage before jumping plus the set sampling deviation value Vset, judging that the input voltage jumps from low voltage to high voltage; when the judgment is not true, the input voltage is normal;

(6) - (7) when the | Vin | > | Vin1| is in a jump state, the input voltage jumps from a low voltage to a high voltage, the actually required input current is smaller than the previous input current, the input current peak value Iin _ pk is calculated through the input current effective value Iin _ rms before the jump state, and the input current after the jump state is limited;

(8) - (9) when the current sampled input current value is greater than or equal to the input current peak value Iin _ pk before hopping, inputting a hopping identification mark Sd to 1, and subtracting an input current variation compensation value from a loop output result of a current beat loop to obtain a final control wave sending value, so that a current peak caused by the fact that the input voltage is hopped from low voltage to high voltage can be immediately inhibited;

(10) when the input voltage is judged to be normal, the maximum value of the input current can be limited, namely the maximum input current is smaller than the maximum current peak value of full power output under the lowest output voltage;

namely: iin _ pk = 1.414 Pmax/(Vin _ min η)

In the formula, Pmax is the maximum output power, the allowed minimum input voltage is Vin _ min, and eta is the lower limit value of efficiency;

(11) - (12) when the current sampled input current value is greater than or equal to the calculated Iin _ pk, inputting a jump identification mark Sd to 1, and subtracting an input current variation compensation value from a loop output result of the current beat current loop to be used as a final control wave generation value, so that a current peak caused by the input voltage jumping from high voltage to low voltage can be immediately inhibited;

(13) - (14) using the Piout result as the wave duty ratio value of the PFC switch tube in the current beat.

Technical Field

The invention relates to the field of high-frequency digital control power supplies and electric automobile charging modules, in particular to an AC-DC (alternating current-direct current) rectification power supply and a vehicle-mounted power supply.

Background

In the field of power supplies, transmission loss caused by reactive current is reduced, and harmonic pollution of a power grid from power supply equipment is avoided. All single-phase or three-phase power supply modules with commercial power alternating current input have strict standard limits on power factor (PF value) and total harmonic component of input current (i.e. ITHD of input current).

In order to ensure a high power factor PF value and a low total harmonic component ITHD, a power supply module needs to add a power factor correction circuit (i.e., a PFC circuit).

For example, a loop control strategy of the PFC is implemented by nesting a voltage outer loop and a current inner loop, that is, a real-time sampled waveform value Vin _ samp of an input voltage multiplied by a result Vpiout of an output voltage outer loop is used as a given value of an input current inner loop. The input current waveform is enabled to follow the input voltage waveform in real time, so that the smaller the phase angle of the input voltage waveform is reduced after the input current lags, and the power factor PF value is improved.

As shown in fig. 1, in the normal operation mode, the conventional control strategy can ensure that the input current follows the input voltage waveform in real time, so as to achieve a higher PF value and a lower ITHD. However, when the input voltage has a large jump, especially the input voltage jumps from low voltage to high voltage, the relationship is calculated according to the duty ratio of the single-phase BOOST circuit:

when the output voltage Vout is constant, the actually required duty cycle D should become small when the input voltage Vin jumps from a low voltage to a high voltage. However, according to the conventional control strategy, when the input voltage jumps from low voltage to high voltage, the real-time sampling value of the input voltage becomes larger, and the given value Iref of the current loop is the product of the real-time sampling value Vin _ samp and the output result Vpiout of the voltage loop, and since the bandwidth of the voltage loop is very low and generally below 50Hz, the output result Vpiout of the voltage loop is basically unchanged, and the given value of the current loop depends on the real-time sampling value of the input voltage. When the real-time sampling value of the input voltage is increased, the given value of the current loop is correspondingly increased, so that the output result of the current loop is increased, and finally, the loop outputs a larger duty ratio D.

When the loop output duty ratio D is much larger than the duty ratio actually required in the final steady state, the inductor current of the PFC will rise sharply, so that a large peak appears in the input current, and there is a serious risk of reliability.

Disclosure of Invention

In order to solve the above problems, the present invention provides an input dynamic control method for a PFC circuit, which adds a variation Δ I of an input current to act on a final loop output result Piout of a current loop when an input voltage jump is recognized based on a conventional PFC loop control, so as to suppress a current spike caused by the input voltage jump, and greatly improve the reliability of a power module in an input dynamic state.

The type of input voltage jump is identified through the output voltage waveform sampled in real time, and corresponding control strategies can be switched through different input voltage jump types.

When the input voltage jumps, calculating a change difference value delta I between the current beat Iin0 of the input current and the previous beat of sampling value Iin1, assigning 0 to the delta I when the delta I is smaller than 0, enabling the input current to be in a descending state, not needing to subtract a compensation value of the change amount of the input current from the output result of a current loop, and multiplying the positive delta I value by a compensation coefficient Kp, wherein the compensation coefficient Kp depends on the rising slope of the input current and the attenuation speed of the output duty ratio; on the premise of ensuring that the input current does not oscillate dynamically, the larger the Kp value is, the better the Kp value is. And obtaining a loop compensation quantity dIout which directly acts on an output result Piout of the current loop, and immediately reducing the wave-sending duty ratio at the current beat so as to inhibit an input current peak generated by input voltage jump.

Drawings

Fig. 1 is a conventional PFC loop control block diagram;

fig. 2 is a control block diagram of a PFC loop after adding a hopping strategy according to the present invention;

FIG. 3 shows a transition condition near a non-zero crossing point of an input voltage in section I;

FIG. 4 shows a transition near the zero crossing of the input voltage in zone II;

FIG. 5 is a flow chart of an input voltage jump strategy in a non-zero crossing region of zone I;

fig. 6 is a flow chart of an input voltage jump strategy in a zero-crossing region of a region II.

Detailed Description

In order to implement the technical solution of the present invention, so that more engineers can understand the present invention, the energy balancing strategy will be further explained in conjunction with the detailed description and the control scheme.

As shown in fig. 2, the main power circuit: an input alternating current source Vac, a rectifier bridge B1, Lpfc is an input differential mode inductor, D1 is an output diode, Q1 is a switch MOS tube, Cout is an output filter capacitor, and RL is an output load. A control loop: vout is an output voltage value, 1/HS is an output voltage sampling coefficient, Vref is an output voltage setting value, VA is a voltage operational amplifier, Kv is voltage loop compensation and can be generally designed into a PI compensator form, MPY is a multiplier, 1/Kv is an input voltage sampling coefficient, and the output result of a voltage loop is multiplied by an input voltage waveform to be used as a given Iref of a current loop; iin is input current, Ri is an input current sampling coefficient, Iin0 is a current beat input current sampling value, CA is an input current operational amplifier, PI is a loop PI compensator of a current loop, and Piout is a loop output result of the current loop; iin1 is a sampling value of one beat of the input current, and Kp is a current compensation coefficient, wherein the compensation coefficient Kp depends on the rising slope of the input current and the decay speed of the output duty ratio; the larger the value of Kp is, the higher the peak suppression speed of the input current is, but the larger the value of Kp is, the oscillation of the input current can be caused in the dynamic state. Therefore, when the Kp value is adjusted in an actual project, the larger the Kp value is, the better the Kp value is on the premise that the input current does not oscillate dynamically. dIout is the loop compensation quantity of the input current change, Sd is the input jump identification flag bit, and mod is the pulse width modulator of PWM wave-sending.

In an actual power grid, input voltage jump may occur at any phase angle in a power frequency cycle of an alternating current input. We divide the case of input voltage jump into two cases as shown in fig. 3 and 4:

region I-input voltage jump in non-zero crossing region:

when the input voltage jump occurs in a non-zero-crossing region of the input voltage, the digital control chip can detect the input voltage through ADC sampling, and determine the input voltage jump direction by detecting that the Δ VI of the input voltage suddenly rises or drops, and trigger a corresponding control strategy, wherein the specific control flow is as shown in FIG. 5.

The specific strategy is described in detail as follows:

(1) powering on a power supply module;

(2) initializing variables, and clearing all variables Vin, Vin1, Iin, Vin _ rms, Iin _ pk and Piout;

(3) sampling the current input voltage Vin and the current input current Iin at a set sampling frequency f, and keeping the input voltage sampled value Vin1 of the previous beat;

(4) by sampling all input voltage sampling values and input current sampling values in a power frequency period, an input voltage effective value Vin _ rms and an input current effective value Iin _ rms of the module before input voltage jumping can be calculated;

(5) by sampling the input voltage value of the current beat and the input voltage value of the last beat, if the input voltage variation | Vin-Vin1| is greater than the Vset value, it is determined that the input voltage has a jump. The size of the Vset value is related to the sampling frequency, and the design needs to ensure that the sampling variation between two beats of the input voltage under a steady state is not larger than the Vset;

(6) judging the jumping direction of the input voltage by comparing the amplitude of the current-beat sampling voltage of the input voltage with the amplitude of the previous-beat sampling voltage;

(7) - (8) when the | Vin | > | Vin1| is in a jump state, the input voltage jumps from a low voltage to a high voltage, and the input current actually required by the module is smaller than the previous module input current, so that a current peak value Iin _ pk is calculated through an effective value Iin _ rms of the input current before the jump, and the input current after the jump is limited;

(9) - (10) when the input current value of the current sample is greater than the input current peak value Iin _ pk before jumping, inputting a jumping identification mark Sd to 1, and finally controlling the wave generation value to be the sum of the loop output result of the current loop of the previous beat and the input current variation compensation value, namely Piout = Piout-dIout, so that the current spike caused by the jumping of the input voltage from low voltage to high voltage can be immediately inhibited;

(11) - (12) when Vin < | Vin1| the input voltage jumps from high voltage to low voltage, the input current actually required by the module is greater than the previous module input current, but less than the input current peak value corresponding to the minimum input voltage at the current input power;

namely: iin _ pk = 1.414 (Vin _ rms Iin _ rms/Vin _ min)

The input power before jumping in the formula is (Vin _ rms × Iin _ rms), and the minimum input voltage allowed by the module is Vin _ min;

(13) - (14) when the current sampled input current value is greater than the calculated Iin _ pk, setting the input jump identification flag Sd to 1, and subtracting the input current variation compensation value from the loop output result of the current loop to serve as a final control wave sending value, namely, Piout = Piout-dlout, so that a current spike caused by the input voltage jumping from high voltage to low voltage can be immediately inhibited;

(15) - (16) using the Piout result as the wave duty ratio value of the PFC switch tube in the current beat.

Input voltage jump in zone II-zero crossing region:

when the jump of the input voltage is close to the zero crossing point of the input voltage, the jump of the input voltage is small in step delta VII, and the jump cannot be identified in a mode of the difference value between the current beat and the previous beat of the sampling value. The jump working condition of the input voltage can be identified through the peak value of the input voltage, and then the input current peak is restrained through a corresponding control strategy. As shown in fig. 6:

(1) powering on a power supply module;

(2) initializing variables, and clearing all variables Vin, Vin1, Iin, Vin _ rms, Iin _ pk and Piout;

(3) sampling the current input voltage Vin and the current input current Iin at a set sampling frequency f, and keeping the input voltage sampled value Vin1 of the previous beat;

(4) by sampling all input voltage sampling values and input current sampling values in a power frequency period, an input voltage effective value Vin _ rms and an input current effective value Iin _ rms of the module before input voltage jumping can be calculated;

(5) and when the current sampling value Vin of the input voltage is greater than the peak value 1.414 of the input voltage before the jump, Vin _ rms and the set sampling deviation value Vset, judging that the input voltage jumps from the low voltage to the high voltage. When the judgment is not true, the input voltage is normal;

(6) deleting;

(7) - (8) when the | Vin | > | Vin1| is in a jump state, the input voltage jumps from a low voltage to a high voltage, and the input current actually required by the module is smaller than the previous module input current, so that a current peak value Iin _ pk is calculated through an effective value Iin _ rms of the input current before the jump, and the input current after the jump is limited;

(9) - (10) when the input current value of the current sample is larger than the input current peak value Iin _ pk before jumping, inputting a jumping identification mark Sd to 1, and subtracting the input current variation compensation value from the loop output result of the current beat loop to obtain a final control wave sending value, namely, Piout = Piout-dlout, so that the current spike caused by the jumping of the input voltage from low voltage to high voltage can be immediately inhibited;

(11) deleting;

(12) when the input voltage is judged to be normal, the maximum value of the input current can be limited. Namely, the maximum input current of the module is smaller than the maximum current peak value of full power output under the lowest output voltage;

namely: iin _ pk = 1.414 Pmax/(Vin _ min η)

In the formula, Pmax is the maximum power which can be output by the module, the minimum input voltage allowed by the module is Vin _ min, and η is the lower limit value of the efficiency of the module;

(13) - (14) when the current sampled input current value is greater than the calculated Iin _ pk, inputting a jump identification mark Sd to 1, and subtracting an input current variation compensation value from a loop output result of the current beat loop to be used as a final control wave generation value, namely, Piout = Piout-dlout, so that a current spike caused by input voltage jumping from high voltage to low voltage can be immediately inhibited;

(15) - (16) using the Piout result as the wave duty ratio value of the PFC switch tube in the current beat.

The invention identifies the jump working condition of the input voltage through the output voltage waveform sampled in real time. And then according to different types of input voltage jump types, corresponding control strategies are carried out to inhibit input current spikes, and the reliability of the PFC part device is greatly improved.

The above embodiments are merely exemplary illustrations of the present invention, and are not intended to limit the present invention. Further steps not described in detail belong to technical content well known to the person skilled in the art. Corresponding changes and modifications within the spirit of the invention are also within the scope of the invention.