A hybrid vector variable frequency control method based on three-phase rectifier

Abstract

The application provides a kind of hybrid vector variable frequency control method based on three-phase rectifier, it is related to power electronic electric energy conversion technical field;Current three-phase PWM rectification technology is important front-stage equipment, and the current of switch tube is large, and the loss of switch tube is composed of turn-on loss and conduction loss, and conduction loss cannot be avoided in high-power state, and switch loss is related to frequency, if switch tube loss is not controlled, switch tube loss will accumulate in the form of heat, when temperature exceeds the limit of switch tube, it often causes irreversible damage to switch tube, therefore, on the basis of considering the power quality of DC side, the action frequency of switch tube of three-phase PWM rectifier is dynamically controlled to realize the continuous operation of three-phase PWM system under high power, and the method considers the stability of DC side voltage and the temperature characteristics of IGBT to carry out frequency modulation.

Description

Technical Field

[0001] This invention relates to the field of power electronics and power conversion technology, and in particular to a hybrid vector frequency conversion control method based on a three-phase rectifier. Background Technology

[0002] With the development of power electronics technology, the research and development technology of energy routers has become increasingly mature. Due to their ability to control the direction of energy flow, they are widely used in microgrids. Three-phase voltage source PWM rectifiers, with their bidirectional energy flow, four-quadrant operation, controllable output voltage, and unity power factor, are crucial front-end devices in energy routers for AC-DC power conversion; therefore, their stable and reliable operation is paramount.

[0003] Current three-phase PWM rectification technology often involves high current through the switching transistors, which are crucial front-end devices. The losses of these transistors consist of both turn-on and conduction losses. If these losses are not controlled, irreversible damage to the transistors can occur. While single-vector control can significantly reduce heat generation, it results in high DC voltage noise and poor dynamic performance. Multi-vector control can address this issue, but the number of switching cycles varies considerably. Therefore, considering DC power quality, it is necessary to combine multi-vector and single-vector control methods to dynamically control the switching frequency of the three-phase PWM rectifier. Hybrid vector control is used to achieve continuous operation of the three-phase PWM system at high power. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a hybrid vector frequency conversion control method based on a three-phase rectifier.

[0005] A hybrid vector frequency converter control method based on a three-phase rectifier includes the following steps:

[0006] Step 1: For a three-phase PWM rectifier, predict the optimal switching state by utilizing the relationship between the AC voltage measurements of the three-phase PWM rectifier;

[0007] Step 1.1: Collect the voltage and current signals of the three phases A, B, and C of the three-phase rectifier, as well as the DC side voltage signal, as the input of the three-phase rectifier;

[0008] Step 1.2: Based on the time-domain model of the three-phase PWM rectifier, the foundation of the prediction model is first established. The time-domain model of the rectifier is established based on Kirchhoff's voltage law, and after a two-phase rotational transformation, the following relationship is obtained:

[0009]

[0010] Where i α i β eα e β The grid-side current and voltage in the three-phase stationary coordinate system are converted to the grid-side current and voltage in the two-phase stationary coordinate system, respectively. α v β To convert AC voltage measurement to AC voltage measurement in a two-phase stationary coordinate system, R is the grid-side equivalent resistance and L is the grid-side inductance;

[0011] Step 1.3: After transforming Step 1.2 using the forward Euler method, the expression for the AC voltage vector of the rectifier is obtained as follows:

[0012]

[0013] Where v α (k), v β (k), i α (k), i β (k), e α (k), e β (k) is i α i β e α e β v α v β The value of i at time k. α (k+1), i β (k+1) is i α i β The value at time k+1;

[0014] Step 1.4: [The text appears to be incomplete and contains several grammatical errors. A more accurate translation would require the full context.] Replace i in the formula of step 1.3 above α (k+1), i β After (k+1), we get:

[0015]

[0016] in and Provide the DC side voltage value Compared with the actual DC side voltage value v dc (k) After accounting for the deviation, perform a two-phase rotation to a two-phase stationary coordinate transformation. This is the reference voltage vector at the current moment;

[0017] Step 1.5: Based on the reference voltage vector calculated in Step 1.4, determine the location of the N value of the space vector V in the AC measurement space vector sector of the three-phase PWM rectifier. The specific steps are as follows:

[0018] AC voltage vector measurement Is it greater than 0? If the AC voltage vector is measured... If the value is greater than 0, the corresponding value of A is 1; otherwise, the value of A is 0.

[0019] AC voltage vector measurement Is it less than If AC voltage vector is measured Less than The corresponding B value is 1; otherwise, the B value is 0.

[0020] AC voltage vector measurement Is it less than If AC voltage vector is measured Less than The corresponding C value is 1; otherwise, the C value is 0.

[0021] The formula for determining the value of N is:

[0022] N = A + 2B + 4C

[0023] Step 1.6: Set the carrier frequency to f and the amplitude to a triangular wave of 1. Determine the corresponding sector based on the N value obtained in Step 1.5 to determine the action. Each PWM cycle time is T. S At the beginning of each cycle, the rectifier's three bridge arms are in the state of the lower bridge arm being on and the upper bridge arm being off. When the carrier value equals the action value, the switching state of the upper and lower bridge arms of each bridge arm changes once. The action value for each bridge arm is as follows:

[0024]

[0025] In the above formula, T1 and T2 are as shown below, let... For A1, For B1, For C1, S a ,S b ,S c The node that switches the switching state of each bridge arm within a periodic time;

[0026]

[0027] Step 1.7: Based on T1 and T2 calculated in Step 1.6, calculate the VT value as follows:

[0028]

[0029] In the above formula, the adjustment coefficient λ is 0.05;

[0030] If the value of VT is 0, the system output is based on the action value of each bridge arm calculated in step 1.6.

[0031] If VT is 0 and T1 ≤ λT2, then the motion value of each arm of the system is output according to the following formula:

[0032]

[0033] If VT is 1 and T2 ≤ λT1, then the motion value of each arm of the system is output according to the following formula:

[0034]

[0035] Step 2: Real-time monitoring of the temperature status of the three-phase PWM rectifier, and setting different temperature ranges. When the three-phase PWM rectifier is in different temperature ranges, switching control is used to maintain the normal operation of the rectifier.

[0036] Step 2.1: Collect the temperature values ​​of the 6 switching transistors on the three-phase PWM rectifier using temperature sensors, and set the warning temperature as T0 and the extreme temperature as TMAX;

[0037] Step 2.2: Construct the frequency reduction function with the switching transistor's case temperature T as the independent variable as follows:

[0038]

[0039] Step 2.3: Construct a system based on the DC voltage value v dc The compensation frequency function for the independent variable:

[0040]

[0041] When F T When the value of (T) is 1, the output is as specified in step 1.7;

[0042] When F T When the value of (T) is 2, the output is as specified in step 1.7, but the carrier frequency is changed as shown in the following formula:

[0043]

[0044] When F T When the value of (T) is 3, according to the output specified in step 1.7, the adjustment coefficient λ and the set carrier frequency are changed. The change of the set carrier frequency is shown in the following formula:

[0045]

[0046] The adjustment coefficient λ is used when the compensation frequency function F V (v dc When ) is 1, it remains unchanged, and when the compensation frequency function F V (v dc When ) is 2, the adjustment coefficient is changed to 2λ, and the compensation frequency function FV (v dc When the value is 3, the adjustment coefficient is changed to 3λ.

[0047] The beneficial effects of this invention are as follows:

[0048] This technical solution provides a hybrid vector frequency conversion control method based on a three-phase rectifier, relating to the field of power electronics energy conversion technology. Current three-phase PWM rectification technology, being a crucial front-end device, often involves large currents through its switching transistors. The losses of these transistors consist of both turn-on and conduction losses. Conduction losses are unavoidable under high power conditions, and since switching losses are frequency-dependent, they accumulate as heat if not controlled. When the temperature exceeds the transistor's limit, irreversible damage often occurs. Therefore, it is necessary to dynamically control the switching frequency of the three-phase PWM rectifier while considering DC-side power quality to achieve continuous operation of the three-phase PWM system under high power. This method considers the stability of the DC-side voltage and the temperature characteristics of the IGBT to modulate the drive frequency. Attached Figure Description

[0049] Figure 1 This is a flowchart illustrating the overall process of a hybrid vector frequency conversion control method based on a three-phase rectifier according to the present invention.

[0050] Figure 2 This is a schematic diagram of the frequency reduction control principle of the three-phase PWM rectifier of the present invention. Detailed Implementation

[0051] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0052] This invention proposes a hybrid vector frequency conversion control method based on a three-phase rectifier, which simultaneously monitors the temperature of the IGBT and the DC-side voltage value, and ensures the normal operation of the three-phase PWM rectifier by predicting a reasonable frequency conversion strategy from a multi-vector model.

[0053] A hybrid vector frequency converter control method based on a three-phase rectifier is shown in the attached figure. Figure 1 As shown; including the following steps:

[0054] Step 1: For a three-phase PWM rectifier, predict the optimal switching state by utilizing the relationship between the AC voltage measurements of the three-phase PWM rectifier; the frequency reduction control principle diagram of the three-phase PWM rectifier is attached. Figure 2 As shown;

[0055] Step 1.1: Collect the voltage and current signals of the three phases A, B, and C of the three-phase rectifier, as well as the DC side voltage signal, as the input of the three-phase rectifier;

[0056] Step 1.2: Based on the time-domain model of the three-phase PWM rectifier, the foundation of the prediction model is first established. The time-domain model of the rectifier is established based on Kirchhoff's voltage law, and after a two-phase rotational transformation, the following relationship is obtained:

[0057]

[0058] Where i α i β e α e β The grid-side current and voltage in the three-phase stationary coordinate system are converted to the grid-side current and voltage in the two-phase stationary coordinate system, respectively. α v β To convert AC voltage measurement to AC voltage measurement in a two-phase stationary coordinate system, R is the grid-side equivalent resistance and L is the grid-side inductance;

[0059] Step 1.3: After transforming Step 1.2 using the forward Euler method, the expression for the AC voltage vector of the rectifier is obtained as follows:

[0060]

[0061] Where v α (k), v β (k), i α (k), i β (k), e α (k), e β (k) is i α i β e α e β v α v β The value of i at time k. α (k+1), i β (k+1) is i α i β The value at time k+1;

[0062] Step 1.4: [The text appears to be incomplete and contains several grammatical errors. A more accurate translation would require the full context.] Replace i in the formula of step 1.3 above α (k+1), i β After (k+1), we get:

[0063]

[0064] in and Provide the DC side voltage value Compared with the actual DC side voltage value v dc (k) After accounting for the deviation, perform a two-phase rotation to a two-phase stationary coordinate transformation. This is the reference voltage vector at the current moment;

[0065] Step 1.5: Based on the reference voltage vector calculated in Step 1.4, determine the location of the N value of the space vector V in the AC measurement space vector sector of the three-phase PWM rectifier. The specific steps are as follows:

[0066] AC voltage vector measurement Is it greater than 0? If the AC voltage vector is measured... If the value is greater than 0, the corresponding value of A is 1; otherwise, the value of A is 0.

[0067] AC voltage vector measurement Is it less than If AC voltage vector is measured Less than The corresponding B value is 1; otherwise, the B value is 0.

[0068] AC voltage vector measurement Is it less than If AC voltage vector is measured Less than The corresponding C value is 1; otherwise, the C value is 0.

[0069] The formula for determining the value of N is:

[0070] N = A + 2B + 4C

[0071] The operating state of the three-phase PWM rectifier is determined by the value of N.

[0072] Step 1.6: Set the carrier frequency to f and the amplitude to a triangular wave of 1. Determine the corresponding sector based on the N value obtained in Step 1.5 to determine the action. Each PWM cycle time is T. S At the beginning of each cycle, the rectifier's three bridge arms are in the state of the lower bridge arm on and the upper bridge arm off. When the carrier value equals the action value in the table below, the switching state of the upper and lower bridge arms of each bridge arm changes once. Since the carrier is symmetrical, only the first half of the cycle is set, and the switching state changes symmetrically in the second half of the cycle. The action values ​​for each bridge arm are as follows:

[0073]

[0074]

[0075] In the above formula, T1 and T2 are as shown below, let... For A1, For B1, For C1, S a ,S b ,S c The node that switches the switching state of each bridge arm within a periodic time;

[0076]

[0077]

[0078] Step 1.7: Based on T1 and T2 calculated in Step 1.6, calculate the VT value as follows:

[0079]

[0080] In the above formula, the adjustment coefficient λ is 0.05;

[0081] If the value of VT is 0, the system output is based on the action value of each bridge arm calculated in step 1.6.

[0082] If VT is 0 and T1 ≤ λT2, then the motion value of each arm of the system is output according to the following formula:

[0083]

[0084] If VT is 1 and T2 ≤ λT1, then the motion value of each arm of the system is output according to the following formula:

[0085]

[0086] Because the switching sequence described in step 1.6 involves four switching state changes within one cycle, this leads to increased heating of the switching transistors in the three-phase PWM rectifier, reducing overall power transfer efficiency. Switch losses are divided into conduction losses and switching losses. Conduction losses are related to the current in the line, while switching losses are related to the number of switching cycles. Therefore, frequent changes in the switching transistor state can increase switching losses and easily cause system failures. Thus, the hybrid vector control design incorporates a parameter of 0.05 to select the primary voltage vector participating in the synthesis of the reference voltage vector in the next control cycle.

[0087] Step 2: Real-time monitoring of the temperature status of the three-phase PWM rectifier, and setting different temperature ranges. When the three-phase PWM rectifier is in different temperature ranges, switching control is used to maintain the normal operation of the rectifier.

[0088] Step 2.1: Collect the temperature values ​​of the 6 switching transistors on the three-phase PWM rectifier using temperature sensors, and set the warning temperature as T0 and the extreme temperature as TMAX;

[0089] Step 2.2: Construct the frequency reduction function with the switching transistor's case temperature T as the independent variable as follows:

[0090]

[0091] Step 2.3: Construct a system based on the DC voltage value v dc The compensation frequency function for the independent variable:

[0092]

[0093] When F T When the value of (T) is 1, the output is as specified in step 1.7;

[0094] When F T When the value of (T) is 2, the output is as specified in step 1.7, but the carrier frequency is changed as shown in the following formula:

[0095]

[0096] When F T When the value of (T) is 3, according to the output specified in step 1.7, the adjustment coefficient λ and the set carrier frequency are changed. The change of the set carrier frequency is shown in the following formula:

[0097]

[0098] The adjustment coefficient λ is used when the compensation frequency function F V (v dc When ) is 1, it remains unchanged, and when the compensation frequency function F V (v dc When ) is 2, the adjustment coefficient is changed to 2λ, and the compensation frequency function F V (v dc When the value is 3, the adjustment coefficient is changed to 3λ.

Claims

1. A hybrid vector frequency conversion control method based on a three-phase rectifier, characterized in that, Includes the following steps: Step 1: For a three-phase PWM rectifier, predict the optimal switching state by utilizing the relationship between the AC side voltages of the three-phase PWM rectifier; Step 1.1: Collect the voltage and current signals of the three phases A, B, and C of the three-phase rectifier, as well as the DC side voltage signal, as the input of the three-phase rectifier; Step 1.2: Based on the time-domain model of the three-phase PWM rectifier, the foundation of the prediction model is first established. The time-domain model of the rectifier is established based on Kirchhoff's voltage law, and after a two-phase rotational transformation, the following relationship is obtained: in , , , The grid-side current and voltage in the three-phase stationary coordinate system are converted into grid-side current and voltage in the two-phase stationary coordinate system, respectively. , To convert AC voltage measurement to AC voltage measurement in a two-phase stationary coordinate system, R is the grid-side equivalent resistance and L is the grid-side inductance; Step 1.3: After transforming Step 1.2 using the forward Euler method, the expression for the AC voltage vector of the rectifier is obtained as follows: in , , , , , for , , , , , The value at time k, , for , The value at time k+1; Step 1.4: [The text appears to be incomplete and contains several grammatical errors. A more accurate translation would require the full context.] Replace the formula in step 1.3 above. , The result was: in and Provide the DC side voltage value Compared with the actual DC side voltage value After accounting for the deviation, a two-phase rotation to a two-phase stationary coordinate transformation is performed. , This is the reference voltage vector at the current moment; Step 1.5: Based on the reference voltage vector calculated in Step 1.4, determine the position of the N value of the space vector V in the AC measurement space vector sector of the three-phase PWM rectifier; Step 1.6: Set the carrier frequency to... A triangular wave with an amplitude of 1 is used to determine the corresponding sector and thus the action based on the N value obtained in step 1.

5. The duration of each PWM cycle is... At the beginning of each cycle, the three bridge arms of the rectifier are in the state of the lower bridge arm being on and the upper bridge arm being off. When the carrier value equals the action value, the switching state of the upper and lower bridge arms of each bridge arm changes once. Step 2: Real-time monitoring of the temperature status of the three-phase PWM rectifier, and setting different temperature ranges. When the three-phase PWM rectifier is in different temperature ranges, switching control is used to maintain the normal operation of the rectifier.

2. The hybrid vector frequency conversion control method based on a three-phase rectifier according to claim 1, characterized in that, Step 1.5 determines the location of the N value of the space vector V within the AC measurement space vector sector of the three-phase PWM rectifier, as follows: AC voltage vector measurement Is it greater than 0? If the AC voltage vector is measured... If the value is greater than 0, the corresponding value of A is 1; otherwise, the value of A is 0. AC voltage vector measurement Is it less than If AC voltage vector measurement Less than If the value is 1, then the value of B is 1; otherwise, the value of B is 0. AC voltage vector measurement Is it less than If AC voltage vector measurement Less than If the value is 1, then the value of C is 1; otherwise, the value of C is 0. The formula for determining the value of N is: 。 3. The hybrid vector frequency conversion control method based on a three-phase rectifier according to claim 2, characterized in that, The motion values ​​for each bridge arm in step 1.6 are shown below: In the above formula, T1 and T2 are as shown below, let... For A1, For B1, For C1, The node that switches the switching state of each bridge arm within a periodic time; This is the actual DC-side voltage value; 。 4. The hybrid vector frequency conversion control method based on a three-phase rectifier according to claim 3, characterized in that, Step 1.7: Based on T1 and T2 calculated in Step 1.6, calculate the VT value as follows: Adjustment coefficient in the above formula The value is 0.

05.

5. The hybrid vector frequency conversion control method based on a three-phase rectifier according to claim 4, characterized in that, Step 1.7 If the VT value is 0, the system output is based on the motion value of each bridge arm calculated in Step 1.6; If VT is 0, and The motion value of each bridge arm of the system is then output according to the following formula: If VT is 1, and The motion value of each bridge arm of the system is then output according to the following formula: 。 6. The hybrid vector frequency conversion control method based on a three-phase rectifier according to claim 5, characterized in that, Step 2 is as follows: Step 2.1: Collect the temperature values ​​of the 6 switching transistors on the three-phase PWM rectifier using temperature sensors, and set the warning temperature as T0 and the extreme temperature as TMAX; Step 2.2: Construct the frequency reduction function with the switching transistor's case temperature T as the independent variable as follows: Step 2.3: Construct a system based on DC voltage values The compensation frequency function for the independent variable: 。 7. The hybrid vector frequency conversion control method based on a three-phase rectifier according to claim 6, characterized in that, when When the value is 1, the output is as specified in step 1.7; when When the value is 2, the output follows the procedure specified in step 1.7, but the carrier frequency is changed as shown in the following formula: when When the value is 3, the adjustment coefficient is changed according to the output specified in step 1.

7. The carrier frequency is set, and the change of the carrier frequency is shown in the following formula: Adjustment coefficient When the compensation frequency function When it is 1, it remains unchanged; when the compensation frequency function is 1, it remains unchanged. When the value is 2, the adjustment factor is changed to 2. When the compensating frequency function When the value is 3, the adjustment factor is changed to 3. .

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