阅读说明：本技术 开关功率放大器及其控制方法、控制系统 (Switching power amplifier and control method and control system thereof ) 是由 徐千鸣 胡家瑜 罗安 郭鹏 李加东 陈燕东 何志兴 李民英 于 2021-07-27 设计创作，主要内容包括：本发明公开了一种开关功率放大器及其控制方法、控制系统,以BUCK电路输出电容作为能量缓冲环节,平衡输入侧和输出侧不平衡能量,同时通过控制两个BUCK电路的输出电压差值实现对额定电压的跟踪保证输出电压波形质量。本发明中两个BUCK电路所需功率器件、无源器件数量均与常规单相逆变器相同,同时本发明有效的抑制了直流母线电压电流纹波,实现了功率解耦,适用范围宽泛。(The invention discloses a switching power amplifier and a control method and a control system thereof.A BUCK circuit output capacitor is used as an energy buffer link to balance unbalanced energy of an input side and an output side, and meanwhile, the tracking of rated voltage is realized by controlling the difference value of output voltages of two BUCK circuits to ensure the quality of output voltage waveform. The number of power devices and passive devices required by the two BUCK circuits is the same as that of a conventional single-phase inverter, and meanwhile, the direct-current bus voltage and current ripple is effectively inhibited, power decoupling is realized, and the application range is wide.)

1. A switching power amplifier comprising m half-bridge circuits; each half-bridge circuit output end is connected with a filter inductor; wherein each of said filter inductors is connected to a filter capacitor; the m filter capacitors are connected in parallel.

2. The switching power amplifier of claim 1, wherein the capacitances of all of the filter capacitors are equal.

3. The switching power amplifier of claim 2, wherein the capacitance C of the first filter capacitor_f1The following relation is satisfied:wherein, P_dcRepresenting the average power, ω, of the output of the switching power amplifier_outRepresenting the output of a switching power amplifierAngular frequency, v_dcThe voltage value of the direct current side of the switching power amplifier is shown.

4. The switching power amplifier of claim 1, wherein the inductance of all filter inductors is equal.

5. The switching power amplifier of claim 4, wherein the inductance L of the first filter inductor_f1The following relation is satisfied:C_f1is the capacitance value, ω, of the first filter capacitor_outRepresenting the output angular frequency of the switching power amplifier.

6. The switching power amplifier according to any of claims 1-5, wherein m is 2.

7. A control method for a switching power amplifier according to any one of claims 1 to 6, comprising the steps of:

1) calculating the AC energy Delta W output by the digital power amplifier by using the following formula: Δ W ═ W_dc-W_cf1-…-W_cfm(ii) a Wherein, W_cf1、W_cfmRespectively representing the capacitance values of the first filter capacitor and the mth filter capacitor; w_dcRepresenting the energy variation of the energy storage capacitor of the switching power amplifier; v_dc(0)，v₀₁(0)，v_0m(0) respectively represent energy storage capacitors C_dcInitial voltages of the first filter capacitor and the mth filter capacitor; v. of_dc(t)，v₀₁(t)，v_0m(t) respectively represent energy storage capacitors C_dcA first filter capacitor,The real-time voltage of the mth filter capacitor, namely the voltage at the time t; wherein the capacitance values of the filter capacitors are the same, i.e. C_f＝C_f1＝C_f2＝…＝C_fm；

2) Calculating decoupling modulation degree m at moment t of decoupling modulation degree by using the following formula_dc(t)：

Wherein v is_out(t) is the actual value of the output voltage of the switching power amplifier; c_fRepresenting the capacitance value of the filter capacitor;

will output a desired value v of voltage_outAnd actual value v of output voltage_out(t) subtracting, and obtaining the AC modulation degree Deltam at the time t through proportional control_ac(t)；

Calculating the theoretical modulation degree of the ith branch by using the following formulaAnd theoretical modulation degree of m-i branch

Wherein, i is 1,2, …, m/2;

3) calculating the duty ratio d of the ith branch by using the following formula_oi：

4) And comparing the duty ratio of the ith branch with the triangular carrier, and conducting an upper bridge arm of the half-bridge circuit in the ith branch when the duty ratio is larger than the carrier, or conducting a lower bridge arm of the half-bridge circuit in the ith branch.

8. A control system for a switching power amplifier, comprising a controller; the controller is configured for performing the steps of the method of claim 7; the controller controls the on-off of the half-bridge circuit power device.

Technical Field

The invention relates to the technical field of power supplies in electrical engineering, in particular to a switching power amplifier and a control method and a control system thereof.

Background

A conventional switching power amplifier structure is shown in fig. 1. It comprises an energy storage capacitor C_dcTwo half-bridge circuits S consisting of four power devices₁、S₂And S₃、S₄Two filter inductors L_f1、L_f2And a filter capacitor C_f. Energy storage capacitor C_dcAnd a power device S₁、S₂A first half-bridge circuit formed by connecting in series is connected in parallel with the S₃、S₄The second half-bridge circuits connected in series are connected in parallel. One end L of the two filter inductors_f1、L_f2The filter inductor is respectively connected with the middle points of the first half-bridge circuit and the second half-bridge circuit (namely the output end of the half-bridge circuit, namely one end of the filter inductor is correspondingly connected between two power devices of the half-bridge circuit), and the other ends of the two filter inductors are respectively connected with the filter capacitor C_fTwo ends.

A switching power amplifier is one of the commonly used DC/AC converters, and is essentially a single-phase inverter. However, under the influence of the self structure and the output waveform, when the switching power amplifier works, the input and output instantaneous power is unbalanced due to the coupling of the direct current power and the alternating current power, so that the direct current bus has voltage ripples and current ripples, the working performance of the preceding-stage direct current power supply is further influenced, and the working efficiency of the direct current power supply is reduced if the preceding-stage current ripples are increased.

In the face of the common problem of the switching power amplifier, in engineering, a direct current side capacitor is often added as a buffer link, so that low-frequency fluctuation on a direct current bus is suppressed. However, this method may result in a large increase in the size and cost of the switching power amplifier. The invention patent application review in the aspect of power decoupling of the switching power amplifier in recent years is compared as follows: the single-phase grid-connected inverter with the active power decoupling function and the power decoupling method (publication number: CN104104256A, published: 2014, 10 and 15) can achieve decoupling of direct current power and alternating current power by a method of connecting a half-bridge converter in parallel beside a direct current capacitor, but a half-bridge converter and a buffer capacitor are required to be additionally configured, so that the size and the price of the device are increased. A current compensation method, a power decoupling circuit and a power converter system (publication No. CN110690812A, published: 2020, 01, 14) compensate voltage fluctuation on a capacitor by connecting a full-bridge converter in series with a direct current capacitor, but the method needs to add one more full-bridge converter, and the complexity of a control link is greatly improved.

Disclosure of Invention

The invention aims to solve the technical problem that aiming at the defects of the prior art, the invention provides the switching power amplifier, the control method and the control system thereof, other power devices and passive devices are not required to be added, the number of capacitors on the direct current side of the switching power amplifier is greatly reduced, and the volume of the device is reduced.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a switching power amplifier comprising m half-bridge circuits; each half-bridge circuit output end is connected with a filter inductor; each filter inductor is connected with one filter capacitor; the m filter capacitors are connected in parallel.

The invention can effectively increase the output current of the switching power amplifier and the output power of the device by connecting the plurality of paths of half bridges in parallel. Meanwhile, the filter capacitor can be used as an energy buffer link to decouple the direct current power and the alternating current power of the switching power amplifier. The m filter capacitors greatly increase the energy storage energy of the filtering link and enhance the power decoupling capability of the device.

Because the output voltage is alternating voltage, in order to ensure that the device keeps consistency when outputting, the capacitance values of all the filter capacitors are equal.

Capacitance C of the first filter capacitor_f1The following relation is satisfied:wherein, P_dcRepresenting the average power, ω, of the output of the switching power amplifier_outRepresenting the output angular frequency of the switching power amplifier. v. of_dcIndicating the value of the dc side voltage. When the capacitance value of the filter capacitor is larger than the threshold value, the energy stored in the capacitor is enough to balance the energy generated by the alternating current power, and the complete decoupling of the direct current power and the alternating current power can be realized.

The inductance values of all the filter inductors are equal. Because the output voltage is alternating voltage, in order to ensure that the device keeps consistency when outputting, the inductance values of all the filter inductors are set to be equal.

The inductance value of the first filter inductor satisfies the following relation:C_f1is the capacitance value, ω, of the first filter capacitor_outRepresenting the output angular frequency of the switching power amplifier. According to the design, the cut-off angular frequency of the filter inductor and the filter capacitor is more than 10 times of the output angular frequency, so that the phenomenon that the output waveform of the device is amplitude-limited and distorted due to the fact that the cut-off frequency of the filter is too low can be prevented.

The invention also provides a control method of the switching power amplifier, which comprises the following steps:

1) calculating the AC energy Delta W output by the digital power amplifier by using the following formula: Δ W ═ W_dc-W_cf1-…-W_cfm(ii) a Wherein, W_cf1、W_cfmRespectively representing the capacitance values of the first filter capacitor and the mth filter capacitor; w_dcRepresenting the energy variation of the energy storage capacitor of the switching power amplifier; v_dc(0)，v₀₁(0)，v_0m(0) respectively represent energy storage capacitors C_dcThe initial voltage of the first filter capacitor and the mth filter capacitor; v. of_dc(t)，v₀₁(t)，v_0m(t) respectively represent energy storage capacitors C_dcReal-time voltages of the first filter capacitor and the mth filter capacitor; wherein the capacitance values of the filter capacitors are the same, i.e.

C_f＝C_f1＝C_f2＝…＝C_fm；

2) Calculating decoupling modulation degree m at moment t of decoupling modulation degree by using the following formula_dc(t)：

Wherein v is_out(t) is the actual value of the output voltage of the switching power amplifier; c_fRepresenting the capacitance value of the filter capacitor;

will output a desired value v of voltage_outAnd actual value v of output voltage_out(t) subtracting, and obtaining the AC modulation degree Deltam at the time t through proportional control_ac(t)；

Calculating the theoretical modulation degree of the ith branch by using the following formulaAnd theoretical modulation degree of m-i branch

Wherein, i is 1,2, …, m/2;

3) calculating the duty cycle of the ith branch using:

4) and comparing the duty ratio of the ith branch with the triangular carrier, and conducting an upper bridge arm of the half-bridge circuit in the ith branch when the duty ratio is larger than the carrier, or conducting a lower bridge arm of the half-bridge circuit in the ith branch.

In the invention, the number of half-bridge circuits and the number of filter capacitors, namely m, are even numbers.

The output current of the switching power amplifier can be effectively increased by connecting the plurality of half bridges in parallel, and the output power of the device is increased. Meanwhile, a filter capacitor in the traditional full-bridge converter is split into a plurality of capacitors, so that the original filtering function is kept; on the other hand, the control method provided by the invention can be matched, and the direct current power and the alternating current power of the switching power amplifier are decoupled by taking the cracked filter capacitor as an energy buffer link, so that the voltage fluctuation of the direct current side is greatly reduced, and the output waveform quality is improved. The m filter capacitors greatly increase the energy storage energy of the filtering link, enhance the power decoupling capacity of the device, realize the power decoupling strategies under different power levels by changing the number of the bridge arms and the number of the filter capacitors, and increase the universality of the method.

A control system for a switching power amplifier, comprising a controller; the controller is configured for performing the steps of the above-described method of the invention; the controller controls the on-off of the half-bridge circuit power device.

Compared with the prior art, the invention has the beneficial effects that:

1. according to the invention, the multiple half-bridges are connected in parallel, so that the output current of the switching power amplifier can be effectively increased, and the output power of the device is increased. Meanwhile, the filter capacitor can be used as an energy buffer link to decouple the direct current power and the alternating current power of the switching power amplifier. The m filter capacitors greatly increase the energy storage energy of the filtering link and enhance the power decoupling capability of the device.

2. According to the control method, the cracked filter capacitor is used as an energy buffer link to decouple the direct current power and the alternating current power of the switching power amplifier, so that the voltage fluctuation of the direct current side is greatly reduced, and the output waveform quality is improved.

Drawings

Fig. 1 is a circuit configuration diagram of a conventional switching power amplifier;

FIG. 2 is a topology diagram of a dual BUCK-type switching power amplifier with power decoupling capability according to the present invention;

FIG. 3 is a control block diagram of a dual BUCK type switching power amplifier with power decoupling capability according to the present invention;

FIG. 4 is a voltage comparison graph of the output voltage of the switching power amplifier, the filter capacitor voltage vo1, and the filter capacitor voltage vo2 before and after power decoupling by using the present invention in a simulation example;

FIG. 5 shows the DC-side capacitor voltage v before and after power decoupling by the present invention in a simulation example_dcComparing the images;

FIG. 6 shows DC bus current i before and after power decoupling by the present invention in a simulation example_dcCompare the figures.

Detailed Description

As shown in fig. 2, the dual BUCK switching power amplifier according to the embodiment of the present invention includes a first capacitor C_dc2 switching devices S₁、S₂Filter inductance L_f1And a filter capacitor C_f1The first BUCK circuit (i.e. the first branch) is formed by 2 switching devices S₃、S₄Filter inductance L_f2And a filter capacitor C_f2A second BUCK circuit (i.e., a second branch); the first capacitor is connected with the input ends of the first BUCK circuit and the second BUCK circuit, and the output end of the first capacitor is composed of the anode of the output capacitor of the first BUCK circuit and the anode of the output capacitor of the second BUCK circuit. In the present embodiment, the switching device S₁～S₄Wide bandgap devices are used. The first filter inductor is connected with the first filter capacitor, and the second filter inductor is connected with the second filter capacitor; the first filter capacitor and the second filter capacitor are connected in parallel, and the first filter capacitor and the second filter capacitor are respectively connected in parallel with the lower bridge arms of the two half-bridge circuits.

In the invention, the number of the filter capacitors is consistent with that of the half-bridge circuits.

As shown in fig. 3, the method for controlling a dual BUCK switching power amplifier with power decoupling capability according to the present invention includes:

suppose the output voltage amplitude of the switching power amplifier is v_outThe amplitude of the output current is i_outOutput angular frequency of omega_outOutput power of P_outThe DC side input voltage of the device is v_dcThe impedance of the load is R_load，P_dcRepresenting the DC power, P, of the output of a switching power amplifier_acRepresenting the ac power output by the switching power amplifier. The output power of the switching power amplifier is calculated to satisfy the following conditions:

as can be seen from equation (1), the output power of the switching power amplifier contains constant dc power and variable ac power, and the variable frequency of the ac power is 2 times the output frequency of the switching power amplifier. Under the condition of no power decoupling, the input power P is equal according to the principle that the input and output instantaneous powers are equal_inIt should satisfy:

in order to provide alternating current power Pac in output power, the input current of the direct current bus of the front-stage direct current power supply necessarily contains alternating current ripples, and the alternating current components cause voltage fluctuation on the first capacitor, so that the input voltage and the input current of the direct current bus of the switching power amplifier can be represented as the direct current bus input voltage and the direct current of the switching power amplifier without loss of generality

In the formula (3), i_dc(t) is the input current of the converter, v_dc(t) is the input voltage of the converter, v₀Is v is_dc(t) a direct current component, i₀Is i_dc(t) a direct current component, v_2fIs v is_dc(t) the amplitude of the double frequency component, i_2fIs i_dc(t) the amplitude of the double frequency component contained in (t),is a double frequency voltage v_2fThe phase angle of (a) is determined,is a frequency doubling current i_2fThe phase angle of (c).

As can be seen from equation (2) and equation (3), in order to eliminate the voltage-current double frequency power in equation (3), the ac power in equation (2) is required to be equal to 0. Considering that the output power cannot be changed, it is necessary to provide ac power in a link other than the dc power supply in the input power. Because the power density of the capacitor is much greater than that of the inductor, an output filter capacitor is used to provide the alternating current power. Formula (2) can be rewritten as

The instantaneous power of the capacitor can be expressed as the capacitance current and the capacitance voltage

Considering the symmetry of positive and negative output waveforms of the switching power amplifier, in order to keep the consistency of filter parameters, the values of the filter capacitors of the first BUCK circuit and the second BUCK circuit are the same

C_f1＝C_f2＝C_f (6)

On the premise of not counting energy loss, the filter capacitor C_f1And C_f2The energy variation amount of (c) can be integrated by equation (5):

the first capacitance C at the direct current side can be calculated by the same method_dcEnergy variation amount of (d):

under the ideal condition, the energy variation of the filter capacitor is equal to the energy value of the alternating current power consumption, and the following conditions are met:

W_ac+∫P_ac(t)dt＝0 (9)

in an actual device, there is always a certain difference between the energy variation of the filter capacitor and the energy consumed by the actual ac power, and an ideal tracking effect cannot be achieved, and the difference between the two energies is provided by the first capacitor on the dc side:

W_dc＝W_ac+∫P_ac(t)dt (10)

in order not to affect the waveform quality of the output voltage, the positive electrode output voltages of the first BUCK circuit and the second BUCK circuit satisfy the condition that:

v_out＝v_o1-v_o2 (11)

due to v_outThere is periodicity, and v can be assumed without loss of generality_o1And v_o2Satisfies the following conditions:

wherein f (t) represents v_o1And v_o2Of the common mode component. In order to make the filter capacitor provide alternating current power, the following steps (5), (10) and (12) can be combined:

because the nature of the BUCK circuit determines that the output side voltage can not be greater than the input voltage, and because the BUCK circuit is a chopper circuit, the output voltage thereof is also necessarily greater than zero. So v_o1And v_o2Should satisfy

To make v_outHas the maximum output amplitude, and the initial value of f (t) should satisfy

Calculated by equation (13)

Therefore, the formula (12) can be rewritten as

Wherein u is_1refRepresenting the theoretical degree of modulation, u, of the first BUCK circuit_2refThe theoretical modulation degree of the second BUCK circuit is shown.

In order to realize power decoupling without reducing the quality of output voltage waveform, an output voltage outer ring is added in a control ring for correction, and the specific method is to make difference between theoretical output voltage and actual output voltage and then obtain corresponding correction error quantity Deltam through proportional control_acWhere k represents a scaling factor. The specific mathematical expression is as follows:

according to the formula (17) and the formula (18), the duty ratio of the first BUCK circuit and the second BUCK circuit is obtained

In the formula

The duty ratios in the equation (19) are compared with triangular carriers having thresholds of 0 to 1, respectively, and when the duty ratios are larger than the carriers, S₁、S₃Is turned on and is turned off S₂、S₄And (6) conducting.

The invention provides a filtering parameter calculation method of a double BUCK type switch power amplifier with power decoupling capacity, which comprises the following steps: a capacitance value calculation method of a filter capacitor and an inductance value calculation method of a filter inductor.

When the output filter capacitor voltage fluctuates to the limit, v is expressed by equation (14)_o1Should be equal to the DC side voltage, v_o2Equal to zero, while the circuit has just no power decoupling capability. And then formula (1), formula (7), formula (9) and formula (17) are combined to obtain:

so that the capacitance value of the filter capacitor should satisfy

In the formula P_dcRepresenting the DC power, i.e. the output average power, omega, of a switching power amplifier_outRepresenting the output angular frequency of the switching power amplifier.

The LC low-pass filter, which is a common circuit in the filter circuit, has a cutoff frequency set to at least 10 times the output frequency. The formula for calculating the cut-off frequency of the LC filter is

(10ω_out)²LC＝1 (23)

Since the filter circuits in the switching power amplifier are connected to the negative end of the direct current bus, the filter circuits are independent of each other, and the calculation of the filter inductance can be expressed as

As shown in fig. 5, based on the switching power amplifier structure designed by the present invention, when t is 0.20s, the control method designed by the present invention is used to replace the conventional control method of the switching power amplifier, and it can be seen that the fluctuation of the input voltage doubling frequency of the switching power amplifier is significantly reduced due to the action of the converter of the present invention. The conventional switching power amplifier generates a frequency-doubled voltage ripple with a peak-to-peak value of 22.6V; after the replacement, the peak-to-peak value of the voltage ripple is reduced to 6.3V, the reduction is 72.1%, and the voltage ripple inhibition effect is obvious. As shown in fig. 6, similar to fig. 5, the current ripple of the dc bus is greatly suppressed at the same time, and the peak-to-peak value of the double frequency current component is reduced from 5.4A to 1.4A. From the comparison of the output waveforms of fig. 4, it can be seen that the quality of the output waveform is good, and the quality of the output waveform is not degraded by the ripple of the converter input voltage unless there is a short-time oscillation during the transient at the switching instant.