KR102893582B1 - Model predictive control system and control method of integrated on board charger - Google Patents

Abstract

An integrated on-board charging control system using a predictive model according to one aspect of the present invention comprises: a power conversion unit including a full-bridge converter having a plurality of switching elements arranged in a full-bridge configuration to regulate a DC link voltage in a single-phase grid power supply; and a buck converter having a plurality of series-connected switching elements to regulate a battery-side voltage and a battery-side current in a DC link; and a processor that calculates a change in output power through a previously established predictive model, calculates a duty ratio in a next state of a switching element constituting the buck converter based on the change in output power, and then controls the switching element constituting the buck converter according to the duty ratio.

Description

{MODEL PREDICTIVE CONTROL SYSTEM AND CONTROL METHOD OF INTEGRATED ON BOARD CHARGER}

The present invention relates to an integrated onboard charging control system and control method using a predictive model.

Hybrid electric vehicles (HEVs) are powered by both electric energy and engine energy, so they include both an engine system as well as a motor and battery system that process electric energy.

For example, when a hybrid electric vehicle is charged using a regular household power grid, it uses an integrated onboard charger (OBC) to charge the battery.

The integrated onboard charger can both charge the batteries and drive the starter generator to start the engine.

When an integrated onboard charger performs battery charging, the battery side voltage and battery side current are generally controlled by a Proportional-Integral (PI) controller due to its simplicity and intuitiveness of implementation.

However, the PI controller has a disadvantage of poor dynamic characteristics, and gain tuning of the PI controller is required to properly control the voltage and current. However, increasing the gain to improve the dynamic characteristics has problems such as voltage and current overshoot.

The background technology of the present invention is disclosed in Korean Patent No. 10-2376932 (March 16, 2022), ‘Electric Vehicle Integrated Power Conversion System.’

The present invention has been created to improve the above-mentioned problems, and an object of one aspect of the present invention is to provide an integrated onboard charging control system and control method using a prediction model that extracts a duty ratio through a prediction model for an integrated onboard charger, controls a battery-side current based on the extracted duty ratio, and compensates for a battery-side voltage ripple using a power feedforward component.

An integrated on-board charging control system using a predictive model according to one aspect of the present invention comprises: a power conversion unit including a full-bridge converter having a plurality of switching elements arranged in a full-bridge configuration to control a DC link voltage in a single-phase grid power supply; and a buck converter having a plurality of series-connected switching elements to control a battery-side voltage and a battery-side current in the DC link; and a processor for calculating a change in output power through a previously established predictive model, calculating a duty ratio in a next state of a switching element constituting the buck converter based on the change in output power, and then controlling the switching element constituting the buck converter according to the duty ratio.

The above prediction model of the present invention is characterized in that it is established by applying Kirchhoff's current law and Kirchhoff's voltage law to the equivalent model of the buck converter.

The above prediction model of the present invention is characterized by establishing the above prediction model to calculate the impedance of the load, the capacitor current, the amount of change in the output voltage, and the amount of change in the inductor current.

The processor of the present invention is characterized in that it controls the output voltage to a command output voltage based on proportional-integral control, calculates a command inductor current based on the proportional-integral control, calculates a command output power using the command inductor current and the command output voltage, and calculates a change in the output power using the current output power and the output power of the next state.

The change in the output power of the present invention is characterized in that it is calculated through the difference between the current output power and the output power in the next state.

The output power in the above-described next state of the present invention is characterized in that it is calculated through the sum of the current output power and the change in output power.

The processor of the present invention is characterized in that it calculates the duty ratio by dividing it into a first mode and a second mode, and complementarily switches the switching elements constituting the buck converter in the first mode and the second mode, and the first mode and the second mode are distinguished based on the amount of change in the inductor current calculated according to the prediction model.

The processor of the present invention is characterized in that it compensates for battery-side voltage ripple by adding a feedforward component to the command output power to reduce the amount of change in the output voltage.

The feedforward component of the present invention is characterized in that it is calculated by multiplying the output voltage by the difference between the inductor current and the capacitor current.

An integrated on-board charging system control method according to one aspect of the present invention is characterized by comprising: a step in which a processor controls an output voltage to a command output voltage based on proportional-integral control; a step in which the processor calculates a command inductor current based on the proportional-integral control, calculates a command output power using the command inductor current and the command output voltage, calculates a change in the output power using a current output power and a next state output power based on a pre-established prediction model, and then calculates a duty ratio of a switching element constituting a buck converter in a next state based on the change in the output power; and a step in which the processor controls a switching element constituting the buck converter according to the duty ratio.

The above prediction model of the present invention is characterized in that it is established by applying Kirchhoff's current law and Kirchhoff's voltage law to the equivalent model of the buck converter.

The above prediction model of the present invention is characterized by establishing the above prediction model to calculate the impedance of the load, the capacitor current, the amount of change in the output voltage, and the amount of change in the inductor current.

In the step of calculating the duty ratio of the present invention, the change in the output power is characterized in that it is calculated through the difference between the current output power and the output power in the next state.

In the step of calculating the duty ratio of the present invention, the output power in the next state is characterized in that it is calculated through the sum of the current output power and the amount of change in the output power.

In the step of calculating the duty ratio of the present invention, the processor calculates the duty ratio by dividing it into a first mode and a second mode, and the first mode and the second mode are characterized in that they are distinguished based on the amount of change in the inductor current calculated according to the prediction model.

The processor of the present invention is characterized in that it further includes a step of adding a feedforward component to the command output power to reduce the amount of change in the output voltage and thereby compensate for the battery-side voltage ripple.

In the step of compensating for the battery-side voltage ripple of the present invention, the feedforward component is characterized in that it is calculated by multiplying the output voltage by the difference between the inductor current and the capacitor current.

An integrated onboard charging control system and control method using a predictive model according to one aspect of the present invention establishes a predictive model of an integrated onboard charger (OBC), extracts a duty ratio based on the predictive model, controls a battery-side current based on the extracted duty ratio, and compensates for a battery-side voltage ripple using a power feedforward component.

FIG. 1 is a schematic diagram of an integrated onboard charging system using a predictive model according to one embodiment of the present invention.
FIG. 2 is a simplified circuit diagram of an integrated onboard charger for performing battery charging according to one embodiment of the present invention.
FIG. 3 is an equivalent operating circuit diagram of a buck converter that performs battery charging according to one embodiment of the present invention.
FIG. 4 is a diagram showing inductor voltage and current waveforms according to the switching state of an integrated onboard charger according to one embodiment of the present invention.
FIG. 5 is a circuit diagram of an integrated onboard charger for building a prediction model according to one embodiment of the present invention.
FIG. 6 is a control block diagram of a full bridge converter of an integrated onboard charger for battery charging according to one embodiment of the present invention.
FIG. 7 is a control block diagram for a predictive control module according to one embodiment of the present invention.
FIG. 8 is a diagram showing the simulation results of the operating principle according to the switching state of an integrated onboard charger according to one embodiment of the present invention.
FIG. 9 is a diagram showing simulation results of an integrated onboard charger that performs battery charging according to one embodiment of the present invention.
FIG. 10 is a diagram showing the results of a simulation of output voltage control of an integrated onboard charger using a PI control method and an integrated onboard charging control method using a predictive model according to one embodiment of the present invention.
FIG. 11 is a diagram showing the results of a simulation of output voltage control of an integrated onboard charger using one embodiment of the present invention.
FIG. 12 is a diagram showing the results of a simulation of output voltage control of an integrated onboard charger according to a feedforward component of the output voltage according to one embodiment of the present invention.
Figure 13 is a schematic diagram of the experimental setup consisting of a control board with a digital signal processor (DSP) using a TMS320F28335, a fan, relays, and switches.
Figure 14 is a diagram showing the experimental results of an integrated onboard charger that performs battery charging.
FIG. 15 is a diagram showing the results of an experiment on output voltage control of an integrated onboard charger using PI control and a method according to an embodiment of the present invention.
Figure 16 is a diagram showing the results of an experiment to control the output voltage of an integrated onboard charger when the load impedance changes abruptly in the case where there is no feedforward component of the output power and in the case where there is a feedforward component of the output power.

Hereinafter, an integrated onboard charging system and control method utilizing a predictive model according to one embodiment of the present invention will be described in detail with reference to the attached drawings. In this process, the thickness of lines and the sizes of components depicted in the drawings may be exaggerated for clarity and convenience. Furthermore, the terms described below are defined based on their functions in the present invention and may vary depending on the intent or custom of the user or operator. Therefore, the definitions of these terms should be based on the contents throughout this specification.

FIG. 1 is a schematic diagram of an integrated onboard charging system using a predictive model according to one embodiment of the present invention.

Referring to FIG. 1, an integrated onboard charging system using a prediction model according to one embodiment of the present invention includes a system power supply (20), a starter generator (10), a battery (30), a plurality of relays (R1 to R7) and a power conversion unit (40), and a processor (100).

The grid power (20) is a general household power source that supplies voltage (v _grid ) and current (i _grid ).

The power conversion unit (40) includes a plurality of switching elements (S _Ap , S _An , S _Bp , S _Bn , S _Cp , S _Cn ) and a plurality of capacitors (C _DC , C _bat ).

The power conversion unit (40) connects a starter generator (10) to a plurality of switching elements (S _Ap , S _An , S _Bp , S _Bn , S _Cp , S _Cn ) and a plurality of capacitors (C _DC , C _bat ) depending on the mode, and is equipped with at least one of a full bridge converter, a DC-DC converter, and an inverter.

The power conversion unit (40) includes a single-phase full bridge converter including a plurality of switching elements (S _Ap , S _An , S _Bp , S _Bn ).

In addition, the power conversion unit (40) includes a DC-DC converter including windings (11 to 13) and switching elements (S _Cp, S _Cn ) provided inside the starter generator (10).

Although the starter generator (10) does not operate when charging the battery (30), the windings (11 to 13) provided inside the starter generator in the power conversion unit (40) can be used as a filter inductor of a DC-DC converter for charging the battery.

In addition, in the power conversion unit (40), a three-phase inverter can be implemented based on a plurality of switching elements (S _Ap , S _An , S _Bp , S _Bn , S _Cp , S _Cn ). Three legs are formed through the switching element (S _Ap ) and the switching element (S _An ), the switching element (S _Bp ), the switching element (S _Bn ), and the switching element (S _Cp ) and the switching element (S _Cn ).

The power conversion unit (40) changes the circuit connection according to the on/off operation of multiple relays, thereby configuring the circuit in either the battery charging mode or the starter generator driving mode.

The processor (100) establishes a prediction model. The prediction model will be described later. The processor (100) calculates the change in output power through the established prediction model, calculates the duty ratio constituting the buck converter based on the calculated change in output power, and controls the switching elements (S _{Cp ,} S _Cn ) constituting the buck converter according to the duty ratio. This will be described with reference to FIGS. 2 to 7.

The processor (100) controls multiple relays to set the battery charging mode and charge the battery when battery charging is required or when an external power source is connected to the charging terminal.

FIG. 2 is a simplified circuit diagram of an integrated onboard charger for performing battery charging according to one embodiment of the present invention.

Referring to FIG. 2, the processor (100) turns off the first relay (R ₁ ) to the third relay (R ₃ ) and turns on the fourth relay (R ₄ ) to the seventh relay (R ₇ ) to operate in battery charging mode.

In battery charging mode, the processor (100) receives single-phase system power (20) and generates charging power for charging the battery (30).

Additionally, the processor (100) sets the starter-generator driving mode when the engine starts. The starter-generator driving mode can be set when the ignition key is input or when the engine starts to operate according to the vehicle speed.

The processor (100) sets the starter generator driving mode by turning on the first relay (R ₁ ) to the third relay (R ₃ ) and turning off the fourth relay (R ₄ ) to the seventh relay (R ₇ ).

The first relay (R ₁ ) to the third relay (R ₃ ) can form a first relay group, and the fourth relay (R ₄ ) to the seventh relay (R ₇ ) can be set as a second relay group. The second relay group connects or disconnects the system power (20) to a plurality of switching elements.

FIG. 3 is an equivalent operating circuit diagram of a buck converter that performs battery charging according to one embodiment of the present invention.

Referring to FIG. 3, the power conversion unit (400) of the integrated onboard charging system according to one embodiment of the present invention includes a full bridge converter and a buck converter.

A full bridge converter continuously regulates the DC link voltage (v _DC ) from a single-phase grid supply.

The buck converter regulates the battery-side voltage (v _bat ) and battery-side current (i _bat ) in the DC link. In addition, since the winding of the starter generator (10) is used as the inductor of the buck converter, the equivalent inductance (L _SG ) of the inductor is 1.5 times that of the starter generator (10).

Hereinafter, a model prediction control process of an integrated onboard charger according to one embodiment of the present invention will be described in detail.

In a full-bridge converter, leg-A and leg-B operate independently.

Leg-A is formed by a switching element (S _Ap ) and a switching element (S _An ). The switching element (S _Ap ) and the switching element (S _An ) of leg-A have complementary switching states. That is, when the switching element (S _Ap ) is turned on, the switching element (S _An ) is turned off, and when the switching element (S _Ap ) is turned off, the switching element (S _An ) is turned on.

Leg-B is formed by a switching element (S _Bp ) and a switching element (S _Bn ). The switching element (S _Bp ) and the switching element (S _Bn ) of leg-B also have complementary switching states. That is, when the switching element (S _Bp ) is turned on, the switching element (S _Bn ) is turned off, and when the switching element (S _Bp ) is turned off, the switching element (S _Bn ) is turned on.

The duty ratio of the switching elements (S _Ap ) and (S _An ) of leg-A and the switching elements (S _Bp ) and (S _Bn ) of leg-B is determined by controlling the DC link voltage (v _DC ) and the grid-side current (i _g ).

As a result, the operation of the full bridge converter converts the grid-side voltage (v _g ) into an AC value and the DC link voltage (v _DC ) into a DC value, enabling power factor correction (PFC) of the single-phase grid power supply.

In addition, in the buck converter, leg-C is formed by a switching element (S _Cp ) and a switching element (S _Cn ). The switching element (S _Cp ) and the switching element (S _Cn ) of leg-C have complementary switching states. That is, when the switching element (S _Cp ) is turned on, the switching element (S _Cn ) is turned off, and when the switching element (S _Cp ) is turned off, the switching element (S _Cn ) is turned on.

The duty cycle of the switching elements (S _Cp ) and (S _Cn ) is determined by controlling the battery-side voltage (v _bat ) and battery-side current (i _bat ). Consequently, the operation of the buck converter performs battery charging in the DC link.

In Fig. 3a, the switching element (S _Cp ) of leg-C is on and the switching element (S _Cn ) is off. Therefore, the inductor voltage (v _L ) is expressed as in Equation 1 by Kirchhoff's voltage law (KVL), and the inductor current (i _L ) increases because the inductor voltage (v _L ) is positive.

Here, v _out is the output voltage.

In the first mode, as illustrated in Fig. 3, the switching element (S _Cp ) is in the off state and the switching element (S _Cp ) is in the on state. The inductor voltage (v _L ) is expressed by mathematical expression 2, and the inductor current (i _L ) decreases because the inductor voltage (v _L ) is negative.

When voltage-second balance is applied to the inductor voltage (v _L ), the voltage transfer ratio of the buck converter is calculated as in Equation 3.

Here, D is the duty cycle and T _s is the control period.

FIG. 4 is a diagram showing inductor voltage and current waveforms according to the switching state of an integrated onboard charger according to one embodiment of the present invention.

Referring to Fig. 4, each leg of the full bridge converter composed of switching elements (S _Ap , S _An , S _Bp , S _Bn ) operates independently with a duty ratio determined by controlling the DC link voltage (v _DC ) and grid-side current (i _g ).

In addition, the operation of the buck converter is divided into the first mode and the second mode as shown in Fig. 3 depending on the switching state of the switching elements (S _Cp , S _Cn ).

The switching element (S _Cp ) is on for a first set time of the first mode, for example, T ₁ , and the switching element (S _Cn ) is on for a second set time of the second mode, for example, T ₂ .

Additionally, T ₁ and T ₂ are determined by the duty ratio (D) as in Equation 4.

In the first mode, the inductor current (i _L ) increases by Δi _L,1 during T ₁ because the inductor voltage (v _L ) is positive, as in Equation 1.

In contrast, in the second mode, the inductor current (i _L ) decreases by Δi _L,2 during T ₂ because the inductor voltage (v _L ) is negative, as in Equation 2.

First, we explain the process of establishing a prediction model.

FIG. 5 is a circuit diagram of an integrated onboard charger for building a prediction model according to one embodiment of the present invention.

First, when Kirchhoff's current law is applied to node D, the inductor current (i _L ) is expressed as in mathematical equation 5, as shown in Fig. 5.

Here, i _out is the output current. i _C is the capacitor current, and is expressed as in mathematical equation 6.

Here, C _out is the output capacitance, and by substituting Equation 6 into Equation 5, the variation (Δv _out ) of the output voltage (v _out ) is calculated as in Equation 7.

Here, Z _L is the impedance of the resistive load, and Δv _out can be expressed as in mathematical equation 8.

Here, v _out(k) and v out(k-1) are the output voltages (v _out ) of the current state, respectively, and v _out(k-1) is the output voltage (v _out ) of the previous state.

In mathematical expression 8, the impedance (Z _L ) of the resistive load is calculated as in mathematical expression 9.

Additionally, the impedance of the resistive load (Z _L ) can be used to calculate the output current (i _out ) or capacitor current (i _C ) as in Equation 10.

Next, when KVL is applied to the loop E connected to nodes A, B, C, and D as shown in Fig. 5, the voltage (v _AB ) between nodes A and B is expressed as in mathematical equation 11.

Since the inductor current (v _L ) is expressed as in Equation 12, when Equation 12 is substituted into Equation 11, the change in the inductor current (i _L ) is calculated as in Equation 13.

In mathematical expression 13, the voltage (v _AB ) between nodes A and B can be divided as in mathematical expression 14 according to the switching state of the buck converter as shown in FIG. 3.

Therefore, by substituting Equation 14 into Equation 13 and using Equation 4, the variation (Δi _L ) of the inductor current (i _L ) is calculated as in Equation 15.

Here, Δi _L,1 is the amount of increased inductor current (i _L ) in the first mode during T ₁ and Δi _L,2 is the amount of decreased inductor current (i _L ) in the second mode during T ₂ .

Next, the full bridge converter control method is explained.

FIG. 6 is a control block diagram of a full bridge converter of an integrated onboard charger for battery charging according to one embodiment of the present invention.

The processor (100) functions as a DC link voltage controller, a single-phase grid power current controller, and a third harmonic reduction unit.

The DC link voltage controller controls the DC link voltage (v DC ) by referring to the command DC link voltage (v ^* _DC ).

The single-phase system power current controller controls the dq-axis current (i _d and i _q ) by referring to the dq-axis current (i ^* _d and i ^* _q ), respectively.

Additionally, i ^* _d is set to 0 for unit power factor control of single-phase system power.

In third-harmonic reduction, the non-ideal PR (Proportional-Resonant) controller is suitable for reducing the third-harmonic component contained in the grid-side current (i _g ), which is close to the fundamental component of the grid-side current (i _g ), due to its narrow frequency bandwidth. Consequently, the full-bridge converter of the integrated onboard charger performs AC-DC power conversion between the single-phase grid power and the DC link.

Next, we describe the model predictive control method.

FIG. 7 is a control block diagram for a predictive control module according to one embodiment of the present invention.

Referring to FIG. 7, the processor (100) performs predictive model control using an output voltage and feedforward component based on PI control (proportional-integral control), and an established predictive model.

The processor (100) controls the current output voltage (v _out ) of the integrated onboard charger based on PI control according to the command output voltage (v ^* _out ). The command output power (P ^* _out ) according to PI control is calculated as the product of the command inductor current (i ^* _L ) and the command output voltage (v ^* _out ), as in Equation 16.

Next, using the prediction model construction, the impedance of the resistive load (Z _L ), the capacitor current (i _C ), the variation of the output voltage (v _out ) (Δv _out ), the amount of increased inductor current (i _L ) in the first mode during T ₁ (Δi _L,1 ), and the amount of decreased inductor current (i _L ) in the second mode during T ₂ (Δi _L,2 ) are calculated.

Finally, the duty cycle D of the integrated onboard charger is obtained through the proposed model prediction method.

To explain more specifically, first, the current output power of the integrated OBC of the processor (100) is expressed as in mathematical expression 17.

In Equation 17, the output power (P _out (k+1)) of the next state of the integrated on-board charger can be predicted using the variation (Δv _out ) of the current output voltage (v out) calculated in Equations 8 and ₁₃ and the amount (Δi _{L ,1} ) of the increased inductor current (i _L ) in the first mode during T 1, as in Equation 18.

In mathematical expressions 17 and 18, the change in current output power (P _out ) of the integrated onboard charger (ΔP _out ) is calculated as in mathematical expression 19.

In Equation 19, using the amount (Δi _L,1 ) of the increased inductor current (i _L ) in the first mode during T ₁ as in Equation 15, and the amount (Δi L,2) of the decreased inductor current (i _L ) in the second mode during T ₂ , the slope (ΔP _out,1 , ΔP _{out,2 )} of the current output power (P _out ) is expressed as in Equation 20.

Here, ΔP _out,1 is the increasing slope of the current output power (P _out ) in mode 1 during T ₁ , and ΔP _out,2 is the decreasing slope of the current output power (P _out ) in mode 2 during T ₂ .

In mathematical expressions 19 and 20, the output power (P _out(k+1) ) in the next state is expressed as in mathematical expression 21.

The cost function of the proposed prediction model method is defined as the error (P _err ) between the command output power (P ^* _out ) of the current output power (P _out ) and the output power in the next state (P _out(k+1) ), as in mathematical expression 22.

When the output voltage (v _out ) is appropriately controlled to the command output voltage (v ^* _out ), the error (P _err ) of the output power (P _out ), which is a cost function, is set to 0. Therefore, the cost function, such as Equation 22, is expressed as Equation 23.

As a result of Equation 23, the duty ratio (D) for the next state of the integrated onboard charger is calculated as in Equation 24.

Finally, the switching states of the switching elements (S _Cp ) and the switching elements (S _Cn ) are determined as shown in Fig. 4 according to the duty ratio D calculated as in mathematical expression 24.

In addition, the ripple component of the output voltage (v _out ) occurs when the load impedance changes abruptly. The ripple component of the output voltage (v _out ) must be compensated for because it degrades the dynamic characteristics and reliability of the integrated onboard charger. Therefore, to compensate for the abrupt change in the load impedance, the feedforward component of the output power (P _ff ) as shown in Equation 25 is added to the commanded output power (P ^* _out ).

The feedforward component is calculated by multiplying the output voltage by the difference between the inductor current and the capacitor current.

Next, we explain the simulation results.

The validity of the predictive model method according to one embodiment of the present invention can be verified through PSIM simulation. The simulation parameters are as shown in Table 1.

Parameters Value single-phase grid source (v _g ) 220 V _rms /60 Hz filter inductance (L _f ) 4 mH DC-link capacitance (C _DC ) 2000㎌ single-winding inductance 0.605 mH equivalent inductance (L _SG ) 0.9075 mH output capacitance (C _out ) 610 ㎌ output resistance (R _out ) 20 Ω control period (T _s ) 100 ㎲

FIG. 8 is a diagram showing the simulation results of the operating principle according to the switching state of an integrated onboard charger according to one embodiment of the present invention.

Figures 8a and 8b show the switching states of the switching elements (S _Ap , S _An , S _Bp , and S _Bn ) of the full bridge converter determined by the control of the DC link voltage (v _DC ) and the _grid -side current (i g ). Figure 8c shows the switching states of the switching elements (S _Cp , S _Cn ) of the buck converter determined by the control of the output voltage (v _out ) by the predictive model control method according to an embodiment of the present invention. Figure 8d shows the inductor voltage (v _L ) determined to be positive or negative depending on the switching states of the switching elements (S _Cp , S _Cn ). Finally, Figure 8e shows that the inductor current (i _L ) increases or decreases depending on the inductor voltage (v _L ).

FIG. 9 is a diagram showing simulation results of an integrated onboard charger that performs battery charging according to one embodiment of the present invention.

Figures 9a and 9b show the grid-side voltage (v _g ) and grid-side current (i _g ). In addition, the grid-side voltage (v _g ) can be set to 220 V _rms /60 Hz. Figures 9c and 9d show the DC-link voltage (v _DC ) and the output voltage (v _out ). The DC-link voltage (v _DC ) is controlled to the reference DC-link voltage (v ^* _DC ) set to 400 V using a full-bridge converter. In addition, the DC-link voltage (v _DC ) is controlled to the reference output voltage (v ^* _out ) set to 140 V using a buck converter. In Figure 9c, the fluctuation of the DC-link voltage (v _DC ), which is the second harmonic component, is generated in the full-bridge converter with a single-phase grid power supply. It can be reduced by using a reduction technique with a PR controller and feedforward compensation.

FIG. 10 is a diagram showing the results of a simulation of output voltage control of an integrated onboard charger using a PI control method and an integrated onboard charging control method using a prediction model according to one embodiment of the present invention.

Figure 10 shows the results of simulating the output voltage control of the integrated onboard controller using (a) PI control and (b) the predictive model control method according to the present embodiment.

In Fig. 10a, the output voltage (v _out ) of the integrated onboard controller is controlled to the command output voltage (v ^* _out ) using PI control, and the settling time to reach 160 V is about 80 ms in the transient state.

Increasing the gain of the PI controller to improve the dynamic characteristics of the integrated onboard controller leads to unstable control of the integrated OBC. Therefore, the bandwidth of the PI controller-based output voltage regulator is set to 1/40 times the switching frequency, and the bandwidth of the output current controller is set to 1/5 times the bandwidth of the output voltage controller.

In Fig. 10b, the gain of the output voltage control device based on PI control is the same as in Fig. 10a, and the output voltage (v _out ) of the integrated onboard charger is controlled to the command output voltage (v ^* _out ) using the model predictive control method. In this case, the settling time to reach 160 V is approximately 45 ms in the transient state. Compared to Fig. 10a, the improvement in the dynamic characteristics of the integrated onboard controller can be achieved using the proposed predictive model control method.

FIG. 11 is a diagram showing the results of a simulation of output voltage control of an integrated onboard charger using one embodiment of the present invention.

Referring to Fig. 11, the output voltage (v _out ) of the integrated onboard charger increases from 80 V to 160 V in 0.8 seconds and from 160 V to 100 V in 1.0 seconds. Using the predictive model control method according to one embodiment of the present invention, the output voltage (v _out ) of the integrated onboard controller is controlled to the command output voltage (v ^* _out ), and the robustness of the proposed MPC method is verified through simulation results.

FIG. 12 is a diagram showing the results of a simulation of output voltage control of an integrated onboard charger according to a feedforward component of the output voltage according to one embodiment of the present invention.

Figure 12 shows the simulation results of output voltage control of the integrated OBC when the load impedance changes abruptly (a) in the case where there is no feedforward component of the output power and (b) in the case where there is a feedforward component of the output power.

The output voltage (v _out ) of the integrated onboard charger is controlled to the command output voltage (v ^* _out ) using the model predictive control method according to an embodiment of the present invention, and the load impedance is abruptly changed from 40 W to 20 W in 1.2 seconds. In Fig. 12a, when the load impedance is suddenly changed, the output voltage (v _out ) fluctuates significantly.

However, in Fig. 12b, since the feedforward component of the output power is applied to the proposed predictive control method, the output voltage (v _out ) does not fluctuate even if the load impedance changes rapidly.

The following describes the experimental results.

Figure 13 is a schematic diagram of the experimental setup consisting of a control board with a digital signal processor (DSP) using a TMS320F28335, a fan, relays, and switches.

Experiments were conducted to verify the validity of the proposed MPC method for integrated onboard chargers.

The grid-side voltage (v _g ) is set to 220 V _rms /60 Hz, and the DC link voltage (v _DC ) is controlled to 400 V using a full bridge converter. In addition, unit power factor control of the single-phase grid power is performed, and the third-order harmonic component included in the grid-side current (i _g ) is reduced by a non-PR controller, as shown in the FFT spectrum of Fig. 14. The source and harmonic components are affected by converter control.

FIG. 14 is a diagram showing the experimental results of an integrated on-board charger performing battery charging, and FIG. 15 is a diagram showing the experimental results of output voltage control of an integrated on-board charger using PI control and a method according to an embodiment of the present invention.

Referring to Fig. 14, the command output voltage (v ^* _out ) is changed from 80 V to 160 V and from 160 V to 80 V.

Referring to Fig. 15a, the output voltage (v _out ) is controlled to the command output voltage (v ^* _out ) using PI control, and the time to reach 160 V in a transient state is approximately 112 ms.

In Fig. 15b, the output voltage (v _out ) is controlled to the command output voltage (v ^* _out ) using the model prediction control method in one embodiment of the present invention, and the time to reach 160 V is about 50 ms in the transient state.

That is, compared to Fig. 15a, the dynamic characteristics of the integrated onboard charger were improved using the model predictive control method according to one embodiment of the present invention. Furthermore, as shown in Figs. 10 and 14 in the simulation and experimental results using the proposed MPC method, the settling time for controlling the output voltage in a transient state was reduced by 50% compared to the case using a PI controller. In other words, the experimental results show that the dynamic characteristics improvement performance of the proposed MPC method is similar to the simulation results.

Figure 16 is a diagram showing the results of an experiment to control the output voltage of an integrated onboard charger when the load impedance changes abruptly in cases where there is no feedforward component of the output power and when there is a feedforward component of the output power.

Referring to Fig. 16, the grid-side voltage (v _g ) is set to 220 V _rms /60 Hz, and the DC link voltage (v _DC ) is controlled to 400 V using a full bridge converter. In addition, unit power factor control of the single-phase grid power is performed, and the third-order harmonic component included in the grid-side current (i _g ) is reduced by a non-PR controller, as shown in the FFT spectrum of Fig. 14. The source and harmonic components are affected by converter control.

The output voltage (v _out ) fluctuates significantly when the load impedance changes suddenly in Fig. 16a. However, since the model predictive control method according to an embodiment of the present invention illustrated in Fig. 16b applies the feedforward component of the output power (P _out ), the output voltage (v _out ) does not fluctuate even if the load impedance changes suddenly.

The implementations described herein may be implemented as, for example, a method or process, an apparatus, a software program, a data stream, or a signal. Even if discussed only in the context of a single form of implementation (e.g., discussed only as a method), the implementation of the discussed features may also be implemented in other forms (e.g., as an apparatus or a program). An apparatus may be implemented using suitable hardware, software, firmware, and the like. A method may be implemented in an apparatus such as a processor, which generally refers to a processing device including, for example, a computer, a microprocessor, an integrated circuit, or a programmable logic device. A processor also includes a communication device such as a computer, a cell phone, a personal digital assistant ("PDA"), and other devices that facilitate the communication of information between end-users.

While the present invention has been described with reference to the embodiments illustrated in the drawings, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent embodiments are possible. Accordingly, the true technical protection scope of the present invention should be defined by the following claims.

10: Starter generator
20: Grid power
30: Battery
40: Power conversion unit
100: Processor

Claims (17)

A power conversion unit including a full bridge converter having a plurality of switching elements arranged in a full bridge form to regulate a DC link voltage in a single-phase grid power source, and a buck converter having a plurality of series-connected switching elements to regulate a battery-side voltage and a battery-side current in the DC link; and
A processor is included that calculates the change in output power through an established prediction model, calculates the duty ratio in the next state of the switching element constituting the buck converter based on the change in output power, and then controls the switching element constituting the buck converter according to the duty ratio.
An integrated onboard charging system characterized in that the above prediction model establishes the above prediction model to calculate the load impedance, capacitor current, change in output voltage, and change in inductor current. In the first paragraph, the prediction model
An integrated onboard charging system using a prediction model characterized in that it is established by applying Kirchhoff's current law and Kirchhoff's voltage law to an equivalent model of the above buck converter. delete In the first paragraph, the processor
An integrated onboard charging system characterized in that the output voltage is controlled to a command output voltage based on proportional-integral control, the command inductor current is calculated based on the proportional-integral control, the command output power is calculated using the command inductor current and the command output voltage, and the change in the output power is calculated using the current output power and the output power of the next state. In the fourth paragraph, the change in the output power is
An integrated onboard charging system characterized in that the current output power is calculated based on the difference between the current output power and the output power in the next state. In the fourth paragraph, the output power in the following state is
An integrated onboard charging system characterized in that the current output power is calculated by the sum of the change in output power and the current output power. In the fourth paragraph, the processor
The above duty ratio is calculated by dividing it into the first mode and the second mode,
The switching elements constituting the buck converter are complementarily switched in the first mode and the second mode,
An integrated onboard charging system, characterized in that the first mode and the second mode are distinguished based on the amount of change in the inductor current calculated according to the prediction model. In the fourth paragraph, the processor
An integrated onboard charging system characterized in that a feedforward component is added to the command output power to reduce the amount of change in the output voltage and thereby compensate for the battery-side voltage ripple. In the 8th paragraph, the feedforward component
An integrated onboard charging system characterized in that the output voltage is calculated by multiplying the difference between the inductor current and the capacitor current. A step in which the processor controls the output voltage to a command output voltage based on proportional-integral control;
A step of calculating a command inductor current based on the proportional-integral control by the processor, calculating a command output power with the command inductor current and the command output voltage, calculating a change in the output power with the current output power and the output power of the next state based on a previously established prediction model, and then calculating a duty ratio of the switching element constituting the buck converter in the next state based on the change in the output power; and
The above processor comprises a step of controlling a switching element constituting the buck converter according to the duty ratio,
A control method for an integrated onboard charging system, characterized in that the prediction model establishes the prediction model to calculate the impedance of the load, the capacitor current, the amount of change in the output voltage, and the amount of change in the inductor current. In the 10th paragraph, the prediction model
A control method for an integrated onboard charging system using a predictive model characterized in that it is established by applying Kirchhoff's current law and Kirchhoff's voltage law to an equivalent model of the above buck converter. delete In the 10th paragraph, in the step of calculating the duty ratio,
A control method for an integrated onboard charging system, characterized in that the change in the above output power is calculated through the difference between the current output power and the output power in the next state. In the 10th paragraph, in the step of calculating the duty ratio,
A control method for an integrated onboard charging system, characterized in that the output power in the above-described next state is calculated through the sum of the current output power and the change in output power. In the 10th paragraph, in the step of calculating the duty ratio,
The above processor calculates the duty ratio by dividing it into the first mode and the second mode,
A control method for an integrated onboard charging system, characterized in that the first mode and the second mode are distinguished based on the amount of change in inductor current calculated according to the prediction model. In the 10th paragraph, the processor
A control method for an integrated onboard charging system, characterized in that it further includes a step of adding a feedforward component to the command output power to reduce the amount of change in the output voltage and thereby compensate for the battery-side voltage ripple. In the 16th paragraph, in the step of compensating for the battery side voltage ripple,
A control method for an integrated onboard charging system, characterized in that the above feedforward component is calculated by multiplying the output voltage by the difference between the inductor current and the capacitor current.