CN-115459616-B - General rapid modulation method for VIENNA rectifier

Abstract

The invention discloses a general rapid modulation method of a VIENNA rectifier, which comprises the steps of 1) establishing a mathematical model of the VIENNA rectifier through the mathematical model of the VIENNA rectifier to obtain equality constraints of nine switches and modulation waves, 2) establishing two equations meeting control voltage constraints through defined new variables to give a general solution meeting equality constraint conditions, 3) obtaining six states according to different directions of three-phase current, obtaining inequality constraint conditions under different states according to the six states, obtaining upper and lower limits of values of free variables according to the inequality constraint conditions of the six states, and 4) solving compensation quantity of neutral point potential balance control from a control equation of capacitance neutral point potential control of the VIENNA rectifier. The invention discloses a modulation model and a solving process of a VIENNA rectifier, which have small calculation workload, and greatly reduce calculation time compared with a SVPWM modulation technology of a three-level converter.

Inventors

• LI BIN
• ZHENG ANQI
• LIANG JIAN
• MA ENLU

Assignees

• 扬州大学

Dates

Publication Date

20260505

Application Date

20221012

Claims (3)

1. 1. A general rapid modulation method for a VIENNA rectifier is characterized by comprising the following steps: 1) Establishing a mathematical model of nine switches through a mathematical model of a VIENNA rectifier, and establishing the relation between the nine switches and the three real switches and the current direction to obtain the equality constraint of the duty ratio of the nine switches and the modulation wave; the step 1) specifically comprises the step of assuming that the VIENNA rectifier control voltage is By using , , , Obtaining And (3) with The relation between the two is shown in the formula (1): (1) Because of three switches In relation to the direction of the current For the duty ratio of the three-phase switch, let , Is an intermediate variable of the duty cycle of the three-phase switch, (2) Then the modulation equation constraint equation is obtained: (3) Wherein sign is a sign function, u a 、u b 、u c is a modulated output phase voltage, Is that Modulation coefficients in the coordinate system; is the current on the three-phase inductor; The duty cycle of the positive level switch of a phase, the duty cycle of the positive level switch of a Xiang Fudian, the duty cycle of the positive level switch of b Xiang Zhengdian, the duty cycle of the positive level switch of b Xiang Fudian, the duty cycle of the positive level switch of c Xiang Zhengdian and the duty cycle of the positive level switch of c Xiang Fudian are respectively; S apn 、 S bpn 、S cpn is a, b, c three-phase modulation factor intermediate variable; Is duty cycle Intermediate variables of (2); 2) Establishing two equations meeting control voltage constraint through defined new variables, and giving a general solution meeting the constraint condition of the equations; the step 2) specifically comprises the steps that a free variable exists in the constraint equation (3), and the general structure of the obtained solution is as follows: (4) Wherein the method comprises the steps of Is that S apn 、 S bpn 、S cpn is a, b, c three-phase modulation factor intermediate variable, in which case the free variable S cpn relates to the current direction, S x 、S y is based on A defined intermediate variable; 3) Obtaining six states according to different directions of three-phase current, obtaining inequality constraint conditions under different states according to the six states, obtaining upper and lower limits of the value of a free variable according to the inequality constraint conditions of the six states, and finally determining the duty ratios of the three bidirectional switching tubes; 4) Starting from a control equation of capacitance neutral point potential control of the VIENNA rectifier, solving the compensation quantity of neutral point potential balance control.
2. 2. The method for universal fast modulation of a VIENNA rectifier according to claim 1, wherein said step 3) comprises determining six possible current directions and The ranges of variation of (2) are shown in Table 1: TABLE 1 Direction of (2) Range correspondence ; According to the six conditions of Table 1 and deformation, free variables were obtained The constraints satisfied are shown in Table 2: TABLE 2 Direction of (2) Constraint conditions of (2) ; Obtained in Table 2 To satisfy the constraint conditions of three inequalities, to satisfy the three inequalities simultaneously, the common interval of the inequalities should be taken, for which the lower limit of the common interval is defined And upper limit of Corresponding to Table 2 、 See table 3: TABLE 3 Table 3 Direction of (2) 、 Definition of (2) ; Thereby obtaining The conditions to be satisfied are: (5) determination by means of (5) Obtained according to formula (4) Deforming the formula (2) to obtain: (6) The foregoing definition The final duty cycle is obtained as: (7)。
3. 3. the general fast modulation method for a VIENNA rectifier according to claim 1, wherein the step 4) specifically includes that the compensation amount of the capacitive neutral point control of the VIENNA rectifier is as follows: (8) Wherein the method comprises the steps of The capacitive neutral point control current of (9) is satisfied, The compensation amount for the capacitive neutral point control of the switching tube duty cycle, Is three-phase current on the inductor; (9) (9) In the middle of For the proportional and integral coefficients of capacitive neutral control, The compensation amount obtained by the voltage difference of the upper capacitor and the lower capacitor at the direct current side is as follows: (10) Wherein the method comprises the steps of Is that Is a function of the magnitude of (a).

Description

General rapid modulation method for VIENNA rectifier Technical Field The invention relates to the technical field of power electronic and electric equipment and electric engineering, in particular to a general rapid modulation method for a VIENNA rectifier. Background The VIENNA rectifier is a two-quadrant neutral point clamped three-level PWM rectifier topology. In applications where energy does not need bi-directional flow, the VIENNA rectifier has many advantages. On one hand, compared with the traditional two-level structure, the Harmonic Distortion (THD) of current and the voltage stress of the power switching device are reduced due to the increase of the level number, on the other hand, compared with the three-level PWM rectifier, the required power switching devices are reduced from 12 to 6, the switching loss, the cost and the complexity of control are reduced, in addition, when the power switching devices are conducted, the diodes connected to the direct current buses can block direct current, the direct current problem of an output voltage bridge arm does not exist, the dead time of driving is not required, and therefore the reliability of the rectifier is further improved. The control strategy of the VIENNA rectifier is mainly divided into single-cycle control and vector control. Single cycle control is a non-linear control technique that requires no multipliers and no input voltage detection, and that allows the controlled quantity to track the control reference value during one switching cycle by resetting the integrator. Meanwhile, the single-period control technology has the advantages of constant switching frequency, high response speed, simplicity in control and the like. However, the single-period control of the VIENNA rectifier ignores the dynamic process of the current inner loop, and the duty ratio of the fully-controlled switching tube is directly obtained by the absolute value of the sampling current. Because there is no inner loop of current, the current is controlled to be in open loop state, and the current is easy to be disturbed. The vector control consists of a voltage outer ring and a current inner ring, the control output of the vector control is a control voltage under a 2-phase coordinate system, and the duty ratio of an actual switch is obtained through modulation. The two most common methods currently under investigation and application are sinusoidal carrier modulation (sinusoidal carrier-based modulation, SPWM) and space vector pulse width modulation (space vector pulse width modulation, SVPWM). The carrier modulation method is simple to operate and easy to realize, is convenient for multi-module cascading, but has low utilization rate of the voltage at the direct current side, and cannot control the voltage at the direct current side. The SVPWM switching model is simple, is convenient for microcomputer real-time control, has the characteristics of small torque pulsation, low noise, high voltage utilization rate and the like, and can realize control of direct-current side voltage and reduce switching loss by utilizing the redundant state of a voltage vector. But the algorithm is too complex and uses less because of the increased redundancy state of the voltage vectors. If the essential relation between the SPWM and SWPVM can be found, the SVPWM modulation effect can be realized by a simple and easy-to-realize SPWM modulation method, the SVPWM application can be promoted to any level, and the SVPWM modulation advantage is fully utilized. However, the research on the inherent relation between the two modulation methods still fails to obtain deep analysis and knowledge. In the prior art, the VIENNA rectifier is a three-level rectifier, has small ripple waves, and is widely applied to high-voltage high-power occasions, and the control strategy mainly comprises single-period control and vector control. The single-period control method is a disclosed simple and easy-to-realize method for realizing the unit power factor, but the triple frequency pulsation of the voltage on the upper capacitor and the lower capacitor of the direct current side can occur by using the method. Vector controlled SVPWM modulation is computationally complex because of the large number of synthesized vectors. Disclosure of Invention The invention aims to overcome the defects of the prior art, and provides a VIENNA rectifier rapid modulation method considering neutral-point potential balance control, wherein the calculation workload of a modulation model and a solving process of the VIENNA rectifier is small, and compared with the SVPWM modulation technology of a three-level converter, the calculation time is greatly reduced. The invention aims to realize the general rapid modulation method of the VIENNA rectifier, which comprises the following steps: 1) Establishing a mathematical model of nine switches through a mathematical model of a VIENNA rectifier, and establishing the relation between the nine s