阅读说明：本技术 一种基于多变量控制技术的车载电源pwm控制策略 (Vehicle-mounted power supply PWM control strategy based on multivariable control technology ) 是由 崔熠凡 陈歌 伍俊明 于 2019-09-26 设计创作，主要内容包括：本发明公开了一种基于多变量控制技术的车载电源PWM控制策略,属于电力技术领域,包括建立采用了辅助电流源网络的移相全桥变换器拓扑电路,通过输出电压电流双环PID控制环路计算得到超前桥臂与滞后桥臂的移相角,通过辅助电流环PID控制环路计算得到开关管的导通角,从而既调节输出功率,又解决了对辅助电流源无功电流量的控制,提高系统工作效率的技术问题,本发明解决了采用移相全桥拓扑的车载电源在使用辅助电流源实现轻负载条件下滞后桥臂实现ZVS所需无功电流量不受控制的问题,既利用辅助电流源电路实现了轻载条件下滞后桥臂的ZVS,又可以调节不同负载条件下辅助电流源无功电流量,提升了车载电源的工作效率。(The invention discloses a vehicle power supply PWM control strategy based on multivariable control technology, belonging to the technical field of electric power, comprising establishing a phase-shifted full-bridge converter topological circuit adopting an auxiliary current source network, calculating through an output voltage and current double-loop PID control loop to obtain phase shift angles of an advance bridge arm and a lag bridge arm, calculating through an auxiliary current loop PID control loop to obtain a conduction angle of a switch tube, thereby regulating output power, solving the technical problems of controlling the reactive current quantity of an auxiliary current source and improving the working efficiency of a system, solving the problem that the reactive current quantity required by the lag bridge arm to realize ZVS under the condition of realizing light load by using the auxiliary current source in a vehicle power supply adopting the phase-shifted full-bridge topology is not controlled, realizing the ZVS of the lag bridge arm under the light load condition by using the auxiliary current source circuit, and regulating the reactive current quantity of the auxiliary current source under different, the work efficiency of vehicle mounted power source has been promoted.)

1. A vehicle power supply PWM control strategy based on multivariable control technology is characterized in that: the method comprises the following steps:

step 1: establishing a phase-shifted full-bridge converter topology circuit adopting an auxiliary current source network, and setting a switching tube bridge in the circuit to comprise a switching tube Q₁And a switching tube Q₄And a switching tube Q₂And a switching tube Q₃；

Setting phase shift angle

step 2: detecting output current i of vehicle-mounted power supply in current working environment_LDetermining that the vehicle-mounted power supply is in a light-load working condition;

and step 3: detecting auxiliary current source current i of vehicle-mounted power supply in current working environment_LaSize of (d), calculate i_LaDifference value delta i from given reactive current quantity of auxiliary current source_LaCalculating to obtain the duty ratio d of the switching tube through an auxiliary current PID control loop;

and 4, step 4: detecting output voltage v of vehicle-mounted power supply in current working environment_oAnd an output current i_LSize of (2), calculatingv_oAnd i_LDifference Deltav from given output voltage and output current respectively_oAnd Δ i_LCalculating the phase shift angle of the leading bridge arm and the lagging bridge arm by a double-loop PID control loop of the output voltage and the output current

2. An on-board power supply PWM control strategy based on multivariable control technology as claimed in claim 1, characterized in that: when step 4 is performed, when

when in use

3. An on-board power supply PWM control strategy based on multivariable control technique as claimed in claim 2, characterized in that: phase shift angle

4. an on-board power supply PWM control strategy based on multivariable control technology as claimed in claim 1, characterized in that: the output voltage and the inductive current as feedback signals participate in phase shifting angle

Technical Field

The invention belongs to the technical field of electric power, and particularly relates to a PWM control strategy of a vehicle-mounted power supply based on a multivariable control technology.

Background

With the aggravation of energy crisis and environmental pollution, new energy automobiles are beginning to be accepted by more and more consumers as energy-saving and environment-friendly vehicles for replacing traditional automobiles. Pure Electric Vehicles (EV), which are the most important new energy vehicles, are also considered as the development direction of future vehicles. In order to meet the requirements of loads with different voltage grades in automobiles, the electric system of the electric automobile at present comprises a high-voltage system and a low-voltage system. In the high-voltage system, a high-voltage power battery supplies electric energy to a motor, an air conditioning system and the like; in the low-voltage system, a low-voltage storage battery supplies electric energy to automobile low-voltage loads such as an instrument panel and a windscreen wiper. The high-voltage power battery and the low-voltage storage battery are connected through a primary vehicle-mounted auxiliary charging DC-DC converter and are used for supplying power to a low-voltage load by the high-voltage battery and charging the low-voltage battery.

Because the voltage grade of the high-voltage power battery is 400V, and the voltage grade of the low-voltage storage battery is 12V, the DC-DC converter is required to realize the electrical isolation of high voltage and low voltage; in order to increase the charging efficiency of the battery, the DC-DC converter is required to have the capability of outputting a large current; meanwhile, as the charging process of the storage battery is mostly accompanied with the use of the storage battery, the converter works under the condition of light load more, and therefore the converter is required to have higher light load efficiency. Common isolated DC-DC topologies mainly include a two-transistor forward topology, a half-bridge topology, a full-bridge topology, and the like. The full-bridge topology is more suitable for being applied to vehicle-mounted auxiliary charging DC-DC due to the characteristics of smaller voltage and current stress, smaller magnetic element size, higher magnetic core utilization rate, more flexible and changeable control mode and capability of outputting larger power under the same condition. The phase-shifted full bridge is used as one of full bridge topologies, and besides the advantages of the full bridge circuit, the phase-shifted full bridge can realize Zero Voltage Switching (ZVS) of a primary side switching tube, is favorable for improving the switching frequency, efficiency and power density of a converter, reduces switching noise, is simple to control, and is widely applied to the current medium and high power occasions.

The main problem with the conventional full-bridge converter is the loss of ZVS under light load conditions, which worsens the efficiency and performance of the converter for this particular application. Passive asymmetric auxiliary circuits can effectively solve this problem without much complexity.

As shown in fig. 1, a method adopting an auxiliaryA phase-shifted full-bridge converter topology for a boost current source network. It is composed of an auxiliary inductor L_aAnd an auxiliary capacitor C_a1And C_a2And (4) forming. Auxiliary inductor L_aIs connected with the middle point of the bridge arm. C_a1And C_a2Is a voltage dividing capacitor. Through analysis, the following results are obtained: when Q is₂When conducting, the inductance L_aThe voltage across is-V_Ca1So that i_LaA linear decrease; when Q is₄When conducting, the inductance L_aVoltage at both ends is V_Ca2So that i_LaIncreasing linearly. The auxiliary circuit provides reactive current to ensure ZVS operation regardless of load conditions.

Although the auxiliary current source circuit can expand the load range of realizing ZVS, the reactive current amount of the auxiliary current source is not controlled because the duty ratio of each switching tube is 50%, and the reactive current amount is constant for different working ranges. This reduces the efficiency of the converter, especially for light load conditions.

Disclosure of Invention

The invention aims to provide a vehicle-mounted power supply PWM control strategy based on a multivariable control technology, which solves the technical problems of controlling the reactive current magnitude of an auxiliary current source and improving the working efficiency of a system.

In order to achieve the purpose, the invention adopts the following technical scheme:

a PWM control strategy of a vehicle power supply based on multivariable control technology comprises the following steps:

step 1: establishing a phase-shifted full-bridge converter topology circuit adopting an auxiliary current source network, and setting a switching tube bridge in the circuit to comprise a switching tube Q₁And a switching tube Q₄And a switching tube Q₂And a switching tube Q₃；

Setting phase shift angle

Is Q₁And Q₂And Q₃And Q₄The conduction interval angle between the two ends;

step 2: detecting output current i of vehicle-mounted power supply in current working environment_LSize of (2)Determining that the vehicle-mounted power supply is in a light-load working condition;

and step 3: detecting auxiliary current source current i of vehicle-mounted power supply in current working environment_LaSize of (d), calculate i_LaDifference value delta i from given reactive current quantity of auxiliary current source_LaCalculating to obtain the duty ratio d of the switching tube through an auxiliary current PID control loop;

and 4, step 4: detecting output voltage v of vehicle-mounted power supply in current working environment_oAnd an output current i_LSize of (d), calculate v_oAnd i_LDifference Deltav from given output voltage and output current respectively_oAnd Δ i_LCalculating the phase shift angle of the leading bridge arm and the lagging bridge arm by a double-loop PID control loop of the output voltage and the output current

Thereby regulating the output power.

Preferably, when step 4 is performed, when

Time, i.e. phase shift angle

Less than Q₁And Q₂Conduction angle, duty ratio d and Q of output voltage₁And Q₂Is independent of conduction angle and is only affected by Q₁And Q₂Phase shift angle therebetween

The modulation can not influence the output voltage when the current of the auxiliary current source is controlled to modulate the duty ratio d;

when in use

Time, i.e. phase shift angleGreater than Q₁And Q₂Conduction angle of, duty ratio of output voltage directlyFrom Q₁And Q₂Modulation of conduction angle of₁And Q₂Phase shift angle therebetweenOnly the distance between the positive and negative voltage square waves of the secondary side of the transformer is changed.

Preferably, the phase shift angle

And duty cycle d needs to satisfy the following condition:

preferably, the output voltage and the inductor current participate as feedback signals in the phase shift angle

And the reactive current quantity is used as a feedback signal to participate in the calculation and control of the duty ratio d of the switching tube.

The invention relates to a vehicle-mounted power supply PWM control strategy based on a multivariable control technology, which solves the technical problems of controlling the reactive current amount of an auxiliary current source and improving the working efficiency of a system, solves the problem that the reactive current amount required by a lagging bridge arm to realize ZVS of a vehicle-mounted power supply adopting a phase-shifted full-bridge topology under the condition of realizing light load by using the auxiliary current source is not controlled, realizes the ZVS of the lagging bridge arm under the condition of light load by using an auxiliary current source circuit, can adjust the reactive current amount of the auxiliary current source under different load conditions, improves the working efficiency of the vehicle-mounted power supply, has a simple structure of an auxiliary current source current control loop, is relatively independent from a control loop of output voltage and inductive current, does not interfere with each other, and can simultaneously realize the control of the output voltage.

Drawings

FIG. 1 is a conventional phase-shifted full-bridge converter topology employing an auxiliary current source network;

FIG. 2 is a waveform diagram of auxiliary current source current at different duty cycles;

FIG. 3 is a diagram of the conventional phase-shifted full-bridge PWM control strategy and the main waveforms;

FIG. 4 shows step 4 of the present invention

Duty cycle diagrams of time;

FIG. 5 shows step 4 of the present inventionDuty cycle diagrams of time;

FIG. 6 is a block diagram of an auxiliary current control loop;

FIG. 7 is a schematic diagram of the control system of the present invention.

Detailed Description

1-7, the PWM control strategy of the vehicle power supply based on the multivariable control technology comprises the following steps:

step 1: establishing a phase-shifted full-bridge converter topology circuit adopting an auxiliary current source network, and setting a switching tube bridge in the circuit to comprise a switching tube Q₁And a switching tube Q₄And a switching tube Q₂And a switching tube Q₃；

Setting phase shift angle

Is Q₁And Q₂And Q₃And Q₄The conduction interval angle between the two ends;

the traditional phase-shifted full-bridge PWM control strategy is shown in FIG. 3: two switching tubes Q of leading bridge arm₁And Q₃Conducting alternately, and conducting each switch tube for 180 degrees; two switch tubes Q of lagging bridge arm₂And Q₄Conducting alternately, and conducting each switch tube for 180 degrees;

in fig. 3, Q1, Q2, Q3 and Q4 are driving waveforms of 4 switching tubes respectively; i.e. i_pIs a primary side resonance inductance current waveform; v. of_ABIs the voltage waveform of the primary side of the transformer; v. of_rectThe voltage waveform of the secondary side voltage of the transformer is rectified.

In this example, each cigaretteThe duty ratio of the switch tube and the phase shift angle between the corresponding switch tubes are controlled as control variables, and the corresponding switch tube is defined as Q₁And Q₂And Q₃And Q₄The phase shift angle is Q₁And Q₂And Q₃And Q₄The conduction interval angle between the two ends; meanwhile, the duty ratio of each switching tube is variable.

In the embodiment, an ePWM module 1 adopting a TMS320F28035 chip generates two PWM signals EPWM1A and EPWM1B, and an ePWM module 2 generates two PWM signals EPWM2A and EPWM 2B. Two PWM signals EPWM1A and EPWM1B generated by the ePWM module 1 are used for respectively controlling a switching tube Q₁And Q₃Namely, an ePWM module 1 is used for controlling an advance bridge arm; similarly, two PWM signals EPWM2A and EPWM2B generated by the ePWM module 2 are used for respectively controlling the switching tube Q₂And Q₄Namely, an ePWM module 2 is used for controlling a hysteresis bridge arm;

step 2: detecting output current i of vehicle-mounted power supply in current working environment_LDetermining that the vehicle-mounted power supply is in a light-load working condition;

and step 3: detecting auxiliary current source current i of vehicle-mounted power supply in current working environment_LaSize of (d), calculate i_LaDifference value delta i from given reactive current quantity of auxiliary current source_LaCalculating to obtain the duty ratio d of the switching tube through an auxiliary current PID control loop;

and 4, step 4: detecting output voltage v of vehicle-mounted power supply in current working environment_oAnd an output current i_LSize of (d), calculate v_oAnd i_LDifference Deltav from given output voltage and output current respectively_oAnd Δ i_LCalculating the phase shift angle of the leading bridge arm and the lagging bridge arm by a double-loop PID control loop of the output voltage and the output current

Thereby regulating the output power.

Preferably, when step 4 is performed, when

Time, i.e. phase shift angle

Less than Q₁And Q₂Conduction angle, duty ratio d and Q of output voltage₁And Q₂Is independent of conduction angle and is only affected by Q₁And Q₂Phase shift angle therebetween

The modulation can not influence the output voltage when the current of the auxiliary current source is controlled to modulate the duty ratio d;

when in use

Time, i.e. phase shift angle

Greater than Q₁And Q₂Conduction angle of, duty ratio of output voltage directly from Q₁And Q₂Modulation of conduction angle of₁And Q₂Phase shift angle therebetween

Only the distance between the positive and negative voltage square waves of the secondary side of the transformer is changed.

Preferably, the phase shift angle

And duty cycle d needs to satisfy the following condition:

the control loop of the auxiliary current can be obtained by modeling the small signal of the auxiliary current source as shown in fig. 6, i in fig. 6_La,refIs an auxiliary inductor current reference value; g_c(s) is an auxiliary current loop PI control transfer function; h_i(s) is the auxiliary current loop sampling transfer function; g_id(s) is the auxiliary current loop duty cycle to auxiliary current transfer function; 1/V_MIs the transfer function of PWM pulse width modulation.

Preferably, the output voltage and the inductor current participate in the phase shift as feedback signals as shown in FIG. 7

The amount of the reactive current is taken as a feedback signal to participate in the calculation and control of the duty ratio d of the switching tube, the control loops of the two variables are mutually independent and have no coupling, and V in figure 7_O,refIs the output voltage reference value; v_OIs the current output voltage value; i.e. i_LThe current value of the output inductance current is; i.e. i_L,refTo output an inductor current reference value; i.e. i_LaThe current value of the auxiliary inductance current is obtained; i.e. i_La,refIs an auxiliary inductor current reference value;

is the phase shift angle of the corresponding switch tube; d is the duty ratio of the switching tube; q1, Q2, Q3 and Q4 are driving signals of 4 switching tubes respectively.

In a conventional control system using a phase-shifted full-bridge DC-DC converter, the duty cycle of the switching tube of each bridge arm is kept constant at 50%, and the output voltage is adjusted by changing the phase shift between the switching tubes corresponding to the two bridge arms. A symmetrical 50% duty cycle produces a perfectly triangular current that flows through the auxiliary circuit connected to each bridge arm switching tube. Varying the duty cycle results in a skewed triangular current with different peak values in the auxiliary current source network, and fig. 2 shows the auxiliary current source current at different duty cycles. The amount of ZVS current can be controlled according to the load condition. In the proposed multivariable control technique, the phase shift between the corresponding switching tubes of the two legs and the duty cycle of the switching tubes are controlled simultaneously, so that the output voltage is regulated and the reactive current required to ensure ZVS is minimized. Changing the duty cycle hardly affects the average value of the output voltage, but only makes it asymmetric.

The invention relates to a vehicle-mounted power supply PWM control strategy based on multivariable control technology, which solves the technical problems of controlling the reactive current amount of an auxiliary current source and improving the working efficiency of a system, solves the problem that the reactive current amount required by a lagging bridge arm to realize ZVS of a vehicle-mounted power supply adopting a phase-shifted full-bridge topology under the condition of realizing light load by using the auxiliary current source is not controlled, realizes the ZVS of the lagging bridge arm under the condition of light load by using an auxiliary current source circuit, can adjust the reactive current amount of the auxiliary current source under different load conditions, improves the working efficiency of the vehicle-mounted power supply, has a simple structure of an auxiliary current source current control loop, is relatively independent from a control loop of output voltage and inductive current, does not interfere with each other, can simultaneously realize the control of the output voltage, the inductive current and the auxiliary current source current, can adjust the output power and control the ZVS-free current required by using an The power flow reduces the loss of the system.