Hybrid Carrier PWM Modulation Method for Photovoltaic Energy Storage Drive System of Solar Electric Vehicles

Abstract

The present invention discloses a hybrid carrier PWM modulation method for a photovoltaic energy storage drive system used in a solar electric vehicle. First, the ideal values V A ~V W of the output phase voltages of a six-phase inverter are obtained through a charging while driving controller; then, the voltage differences between V A and V B , V C and V U , V V and V W are respectively obtained through a subtractor; the two voltage differences containing the same phase voltage are multiplied, and the corresponding carrier is selected according to the positive or negative of the product of the two voltage differences; then, the ideal values of the six-phase voltages output by the six-phase inverter and their corresponding carriers are respectively compared through a comparator to output the driving signals of the upper IGBTs of the six-phase inverter; finally, the driving signals of the corresponding lower IGBTs are obtained through an inverter. By means of the proposed hybrid carrier PWM modulation method, the present invention reduces the oscillation of the zero-axis voltage in the six-phase motor, thereby reducing the ripple of the output current of the photovoltaic panel and effectively improving the steady-state performance of the system.

Description

Technical Field

[0001] The present invention relates to a hybrid carrier PWM modulation method for a light storage drive system of a solar electric vehicle, belonging to the field of power electronics and electric drive. Background Art

[0002] The sales volume of electric vehicles has been increasing year by year, and certain breakthroughs have been achieved in related technologies such as energy storage, electric drive, and charging. No matter which charging method is adopted, drawing power from the power grid is still the main means. However, at present, the important source of grid electric energy is still fossil fuels, and the proportion of new energy in the entire energy structure is still relatively low. There is still a long way to go for electric vehicles to fully achieve "zero emissions". Therefore, in order to further reduce the emissions of electric vehicles and achieve sustainable development of energy supply, developing renewable energy represented by solar energy to charge electric vehicles has gradually become a topic of common concern among domestic and foreign scholars and automobile manufacturers. Among them, solar electric vehicles, as a new product with solar energy as an auxiliary energy supply, have received extensive attention from domestic and foreign automobile companies and scholars. However, in order to achieve maximum power factor point tracking and raise the output voltage of the solar panel to the power battery voltage level, it is usually necessary to additionally install a dedicated converter between the power battery and the solar battery, which undoubtedly increases the volume, cost, and weight of the whole vehicle.

[0003] Through the electric drive reconstruction technology, converting the output power control of the solar panel in a solar electric vehicle to the motor 0-axis current control will eliminate the installation of a dedicated converter between the power battery and the solar battery. However, the inductance of the motor 0-axis is extremely small, which will bring the problem of excessive ripple of the photovoltaic panel output current, increasing the motor loss while affecting the steady-state performance of the system. Summary of the Invention

[0004] Object of the Invention: Aiming at the above-mentioned existing technologies, a hybrid carrier PWM modulation method for a light storage drive system of a solar electric vehicle is proposed. This hybrid carrier PWM modulation method reduces the 0-axis voltage oscillation in a six-phase symmetrical permanent magnet synchronous motor to suppress the 0-axis current ripple of the motor and improve the steady-state performance of the system.

[0005] Technical Solution: For the hybrid carrier PWM modulation method of the light storage drive system of a solar electric vehicle, the positive pole of the roof photovoltaic panel is connected to the neutral point of the six-phase permanent magnet synchronous motor, and the negative pole is connected to the negative pole of the battery; the method includes the following steps:

[0006] Step 1: In each control cycle, sample the battery voltage and current V b and I b , the output voltage and current V PV and I PV of the roof photovoltaic panel, the phase currents I A , I B, I C , I U , I V , I W , the rotational speed, rotor position n and θ of the six-phase symmetrical permanent magnet synchronous motor, and the ideal values V A , V B , V C , V U , V V , V W ;

[0007] Step 2: Obtain the voltage differences between each pair of V A , V B , V C and V U , V V , V W respectively through a subtractor;

[0008] Step 3: Multiply the two voltage differences containing the same phase voltage obtained in Step 2 through a multiplier;

[0009] Step 4: Select the first triangular carrier or the second triangular carrier as the carrier for the corresponding phase according to the positive or negative of the product of the voltage differences obtained in Step 3 through a selector;

[0010] Step 5: Compare the ideal values of the six-phase inverter output phase voltages with the corresponding triangular carriers obtained in Step 4 through a comparator to obtain the driving signals of the upper IGBTs of the six-phase inverter;

[0011] Step 6: Invert the driving signals of the upper IGBTs of the six-phase inverter obtained in Step 5 through an inverter to obtain the driving signals of the lower IGBTs of the six-phase inverter.

[0012] Furthermore, in the said Step 2, the voltage differences d A , V B , V C and V U , V V , V W between each pair are obtained according to formula (1) through a subtractor; A , d B , d C , d U , d V , d W ;

[0013]

[0014] Furthermore, in the said Step 3, the product n of the two voltage differences containing the same phase voltage is obtained according to formula (2) through a multiplierA , n B , n C , n U , n V , n W ;

[0015]

[0016] Further, in the step 4, the first triangular carrier wave and the second triangular carrier wave are 10 kHz triangular waves and have a 180° phase difference; the first triangular carrier wave is the main carrier wave of V A , V B , V C , and the second triangular carrier wave is the auxiliary carrier wave of V A , V B , V C . When n x is greater than 0, the second triangular carrier wave serves as the carrier wave of V x , otherwise the first triangular carrier wave serves as the carrier wave of V x , where x ∈ {A, B, C}; the second triangular carrier wave is the main carrier wave of V U , V V , V W , and the first triangular carrier wave is the auxiliary carrier wave of V U , V V , V W . When n y is greater than 0, the first triangular carrier wave serves as the carrier wave of V y , otherwise the second triangular carrier wave serves as the carrier wave of V y , where y ∈ {U, V, W}.

[0017] Beneficial effects: A hybrid carrier PWM modulation method for a light storage drive system of a solar electric vehicle proposed by the present invention greatly reduces the 0-axis voltage oscillation in a six-phase permanent magnet synchronous motor by adopting the hybrid carrier PWM modulation method, so as to reduce the output current ripple of the photovoltaic panel, reduce the motor loss, and improve the steady-state performance of the system. Description of the Drawings

[0018] Figure 1 is a hybrid carrier PWM modulation control block diagram of a light storage drive system of a solar electric vehicle;

[0019] Figure 2 is the first triangular carrier wave and the second triangular carrier wave;

[0020] Figure 3 is the carrier wave corresponding to the ideal voltage output by the six-phase inverter within 1 cycle;

[0021] Figure 4 is the simulation result of the motor zero-sequence current and the photovoltaic panel output current;

[0022] Figure 5 are the simulation results of the motor speed and torque;

[0023] Figure 6 are the phase A and phase U currents of the six-phase symmetrical permanent magnet synchronous motor. Specific embodiments

[0024] The present invention will be further explained below with reference to the accompanying drawings.

[0025] As Figure 1 shown, a hybrid carrier PWM modulation method for a photovoltaic energy storage drive system of a solar electric vehicle, the positive pole of the roof photovoltaic panel is connected to the neutral point of the six-phase symmetrical permanent magnet synchronous motor, and the negative pole is connected to the negative pole of the battery. The control method includes the following steps:

[0026] Step 1: In each control cycle, sample the battery voltage and current V b and I b in the main circuit 1, the output voltage and current V PV and I PV of the roof photovoltaic panel, the motor phase currents I A 、I B 、I C 、I U 、I V 、I W and the motor speed and rotor position n and θ, and output the ideal values V A 、V B 、V C 、V U 、V V 、V W of the output phase voltages of the six-phase inverter through the photovoltaic energy storage drive system while driving and charging controller 2;

[0027] Step 2: Through the subtractor 3, obtain the voltage differences between V A 、V B 、V C and V U 、V V 、V W in pairs; specifically:

[0028] Through the subtractor, obtain the voltage differences d A 、V B 、V C and V U 、V V 、V W between V A 、d B 、d C 、d U 、d V 、d W;

[0029]

[0030] Step 3: Multiply the two voltage differences containing the same-phase voltage obtained in Step 2 by the multiplier 4; specifically:

[0031] Obtain the product n of the two voltage differences containing the same-phase voltage according to formula (2) through the multiplier A , n B , n C , n U , n V , n W ;

[0032]

[0033] Step 4: Select the first triangular carrier 5 or the second triangular carrier 6 as the carrier for the corresponding phase through the selector 7 according to the positive or negative of the voltage difference product obtained in Step 3; specifically:

[0034] As Figure 2 shown, the first triangular carrier and the second triangular carrier are 10 kHz triangular waves, and they are 180° out of phase; the first triangular carrier is the main carrier of V A , V B , V C , and the second triangular carrier is the auxiliary carrier of V A , V B , V C . When n x is greater than 0, the second triangular carrier is used as the carrier of V x , otherwise the first triangular carrier is used as the carrier of V x , x ∈ {A, B, C}; the second triangular carrier is the main carrier of V U , V V , V W , and the first triangular carrier is the auxiliary carrier of V U , V V , V W . When n y is greater than 0, the first triangular carrier is used as the carrier of V y , otherwise the second triangular carrier is used as the carrier of V y , y ∈ {U, V, W}. In one cycle, the carriers corresponding to the ideal voltages V A , V B , V C , V U , V V , V W output by the six-phase inverter are as Figure 3 shown.

[0035] Step 5: Through the comparator 8, compare the ideal value of the output phase voltage of the six-phase inverter with the corresponding triangular carrier wave obtained in Step 4 to obtain the driving signals of the upper IGBTs of the six-phase inverter;

[0036] Step 6: Through the inverter 9, invert the driving signals of the upper IGBTs of the six-phase inverter obtained in Step 5 to obtain the driving signals of the lower IGBTs of the six-phase inverter.

[0037] To verify the technical problems of the present invention, based on Figure 1 the hybrid carrier PWM modulation control block diagram of a light storage drive system for a solar electric vehicle shown in

[0038] In this embodiment, the 01-axis current I 01 , 02-axis current I 02 and the output current I PV of the roof photovoltaic panel obtained by the method of the present invention have simulation waveforms as Figure 4 shown. During the whole process, I 01 , I 02 and I PV remain unchanged, and I 02 always remains zero, ensuring that there is no zero-sequence circulating current between the two sets of motor windings. The ripple of I 01 is less than 0.5 A, the ripple of I PV is less than 1.5 A and I PV is exactly three times that of I 01 . The simulation results of the motor speed n and torque T e are as Figure 5 shown. It can be seen from the figure that the motor speed follows the given 500 r / min, and the motor output torque is constant at 5 N·m. The simulation results of the motor phase currents I A , I U are as Figure 6 shown. During the whole operation process, the motor current remains sinusoidal. Due to the injection of the 01-axis current, there is a negative offset in the motor phase current.

[0039] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. Hybrid carrier PWM modulation method for a photovoltaic energy storage drive system of a solar electric vehicle, characterized in that: The positive pole of the roof photovoltaic panel is connected to the neutral point of the six-phase permanent magnet synchronous motor, and the negative pole is connected to the negative pole of the battery; the method includes the following steps: Step 1: In each control cycle, sample the battery voltage and current V b and I b , the output voltage and current V PV and I PV of the roof photovoltaic panel, the phase currents I A , I B , I C , I U , I V , I W of the six-phase symmetrical permanent magnet synchronous motor, the speed and rotor position n and θ of the six-phase symmetrical permanent magnet synchronous motor, and obtain the ideal values V A , V B , V C , V U , V V , V W of the output phase voltage of the six-phase inverter through the controller of the charging while driving system of the photovoltaic-battery-inverter system; Step 2: Through a subtractor, obtain the voltage differences between V A , V B , V C and V U , V V , V W in pairs respectively; Step 3: Multiply the two voltage differences containing the voltage of the same phase obtained in Step 2 through a multiplier; Step 4: According to the positive or negative of the voltage difference product obtained in Step 3, select the first triangular carrier or the second triangular carrier as the carrier for the corresponding phase through a selector; Step 5: Through a comparator, compare the ideal value of the output phase voltage of the six-phase inverter with the corresponding triangular carrier obtained in Step 4 to obtain the driving signal of the upper IGBTs of the six-phase inverter; Step 6: Through an inverter, invert the driving signal of the upper IGBTs of the six-phase inverter obtained in Step 5 to obtain the driving signal of the lower IGBTs of the six-phase inverter; In step 2, through a subtractor, obtain V according to formula (1) A , V B , V C and V U , V V , V W voltage differences d A , d B , d C , d U , d V , d W ; In step 3, through a multiplier, the product n of two voltage differences including the same-phase voltage is obtained according to formula (2). A , n B , n C , n U , n V , n W ; 2. The hybrid carrier PWM modulation method for the photovoltaic energy storage drive system of a solar electric vehicle according to claim 1, wherein: In step 4, the first triangular carrier wave and the second triangular carrier wave are 10 kHz triangular waves and have a 180° phase difference; the first triangular carrier wave is the main carrier wave of V A , V B , V C , and the second triangular carrier wave is the auxiliary carrier wave of V A , V B , V C . When n x is greater than 0, the second triangular carrier wave serves as the carrier wave of V x , otherwise the first triangular carrier wave serves as the carrier wave of V x , where x ∈ {A, B, C}; the second triangular carrier wave is the main carrier wave of V U , V V , V W , and the first triangular carrier wave is the auxiliary carrier wave of V U , V V , V W . When n y is greater than 0, the first triangular carrier wave serves as the carrier wave of V y , otherwise the second triangular carrier wave serves as the carrier wave of V y , where y ∈ {U, V, W}.

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