TWI509975B - Modulation method for a single phase three-level converter - Google Patents

Description

Modulation method of single-phase three-step converter

A modulation method of a converter, in particular, a modulation method of a single-phase three-step converter.

The structure of the traditional single-phase full-bridge converter is shown in Figure 1, which is US patent US7031176B2. The case uses the traditional H-bridge structure (H Bridge) for voltage conversion from DC voltage to AC voltage. As shown in Fig. 2, the modulation strategy is mainly to obtain a pulse width (PWM) square wave modulation by comparing a carrier with a sine wave. It can be clearly seen from Fig. 2 that in the interval of 0°~360°, the switches are all full-time and full-voltage switching. In other words, there is a high number of switching times between each cycle, and then converted to a 220 VAC system, the voltage difference of each switch is 310V, so the loss is high under high frequency switching, and the efficiency is not good.

In US Patent No. 20090244936A1, as shown in FIG. 3, the method is a three-phase converter architecture of an NPC third-order control strategy.

The energy density and conversion efficiency of solar cells have long been low, which limits their commercial use. The solar photoelectric converter is an end product in the solar system. A common grid-connected solar-to-electrical converter that converts the DC power generated by valuable solar modules into AC power and feeds it back into the grid. Therefore, solar photoelectric converters are required to be extremely efficient, and under this premise, power quality control must still be maintained within reasonable specifications.

The invention focuses on the efficiency improvement of the distributed power supply system, and according to the output voltage polarity, the output current polarity, the 1/2 voltage point, and the analysis through the line operation mode, the voltage intermediate point clamped (NPC) switch switching table is fabricated. . Analysis circuit Equivalent characterization is gradually reduced to achieve the purpose of reducing the number of switching times, which means reducing losses and improving efficiency. However, its energy conversion function cannot be sacrificed due to the adoption of new switching techniques.

The simulation platform used in the modulation mode of the present invention is a T-type intermediate point clamp (T-type NPC) architecture, as shown in FIG. Compared with the traditional half-bridge circuit, the biggest advantage of the neutral point clamped (NPC) half-bridge circuit is that it has a third-order architecture. Compared with the traditional half-bridge circuit, there is only a second-order architecture. The invention can be directly applied to DC/AC. In the converter system, it can be output to a passive load or grid (Vgrid), which is efficient, high performance and economical.

The design of the modulation strategy is first assumed that the system is an ideal balanced structure and the output AC voltage is assumed to be AC220V/60Hz, so the peak voltage is 310Vdc, and the DC power supply (B1)=DC power supply (B2)=1/2 voltage= 155Vdc. According to the current direction, the output voltage polarity and the 1/2 voltage demarcation point establish the conditions for circuit analysis. Here, the 1/2 voltage demarcation point is based on the AC/AC converter's output AC1 AC voltage source. In the positive half cycle, +155V is the 1/2 voltage demarcation point, and in the negative half cycle, the -155V is 1/2. Voltage demarcation point. However, if the DC power supply (B1) voltage is not equal to the DC power supply (B2), the system no longer uses 155V as the 1/2 voltage cut-off point. Instead, the voltages of the DC power supply (B1) and the DC power supply (B2) are dynamically compared with the output AC1 AC voltage source. The third-order voltage source indicates that the positive polarity AC low voltage output 0 < VAC < B1 and the positive polarity AC high voltage output B1 < VAC. For the sake of convenience, the absolute value of the negative polarity voltage is expressed as abs (VAC), whereby the negative polarity AC low voltage output 0 < abs (VAC) < B2, the negative polarity AC high voltage input B2 < abs (VAC). Then add the inductance (L1) current direction condition in the line, that is, the positive current and the negative current, and the combination of these three conditions will form eight states. If the eight circuit operating states are further divided by the pulse width modulation (PWM) duty cycle, two circuit switching patterns are formed in each frame. The upper half belongs to the high pulse width modulation (PWM) duty cycle (Duty-High), and the lower half belongs to the low pulse width modulation (PWM) duty cycle (Duty-Low), which collectively forms a total of 16 circuits.

Table 1 is the intermediate point clamped (NPC) basic switch switching table (I++) indicating positive polarity current increase, (I+) indicating positive polarity current reduction, Table (I--) It indicates that the negative polarity current is increased, and (I-) indicates that the negative polarity current is decreased. The invention directly compares the first direct current power source (B1) and the second direct current power source (B2) with the 1/2 output voltage, except for being applied to the balance system. It is also possible to realize an unbalanced system in which the voltages of the first direct current power source (B1) and the second direct current power source (B2) are different.

The present invention can be implemented in a software or hardware manner. As shown in the dotted line in FIG. 5, it is one of the specific implementable schemes, which is a controller 31. After the scheme is verified by using the power electronic simulation software PSIM, the communication can be generated as shown in FIG. Voltage output. The load of this example is a resistor. According to an embodiment of the present invention, the system is a balanced structure, and is a modulation method of a single-phase three-step converter. The modulation method includes the following steps: using a single-phase third-order circuit to connect an AC voltage through an inductor. One end of the source, and a capacitor; and a single-phase third-order circuit is controlled using a voltage intermediate point clamped (NPC) switch switching table; wherein, through the voltage intermediate point clamped (NPC) The switch switching table selects the current loop of the single-phase third-order circuit to reduce the switching frequency of the single-phase third-order circuit and provide a DC to AC conversion with low energy loss. If the system is unbalanced, for example, the terminal voltage of the first DC power source (B1) is not equal to the terminal voltage of the second DC power source (B2). At this point, the first DC power supply (B1) must be compared to the 1/2 grid voltage of the corresponding polarity. Only then can you decide the steps.

Q1A‧‧‧Q1A switch

Q2A‧‧‧Q2A switch

Q2‧‧‧Q2 switch

Q1‧‧‧Q1 switch

Q3‧‧‧Q3 switch

Q4‧‧‧Q4 switch

L1‧‧‧Inductance

AC1‧‧‧ AC voltage source

C1‧‧‧ capacitor

B1‧‧‧First DC power supply

B2‧‧‧second DC power supply

Figure 1 is a diagram showing a conventional technical structure.

Fig. 2 is a pulse width (PWM) square wave modulation obtained by comparing a conventional carrier with a sine wave.

Figure 3 is an illustration of the modified structure to full bridge architecture of the present invention.

Figure 4 is a schematic diagram of the full bridge architecture and three-phase architecture of the extended intermediate point clamped (NPC) of the present invention.

Fig. 5 is a diagram showing an example of a neutral point clamped (NPC) control scheme of the present invention.

Figure 6 is a simulation state diagram of a neutral point clamped (NPC) architecture of the present invention.

Figures 7A-7H are diagrams of the 16 types of loop structures of the present invention.

The present invention provides an embodiment in which the system is a balanced structure that produces an AC voltage source (AC1) output. As shown in FIG. 7A to FIG. 7H, a modulation method of a single-phase three-step converter, wherein the step of the modulation method includes: using a single-phase third-order circuit, connecting one through an inductor (L1) One end of an alternating voltage source (AC1) and a capacitor (C1); and a single phase third-order circuit is controlled using a voltage intermediate point clamped (NPC) switch switching table; wherein the intermediate point of the voltage is passed A neutral point clamped (NPC) switch switching table selects a current loop in the single-phase third-order circuit to reduce the switching frequency of the single-phase third-order circuit and provide a DC-AC with low energy loss (DC to AC) ) Conversion.

The single third-order circuit, as shown in FIG. 4, includes: a Q1A switch (Q1A), a Q2A switch (Q2A), a Q2 switch (Q2), a Q1 switch, a Q3 switch (Q3), and A Q4 switch (Q4). Wherein, one end of the Q1A switch (Q1A) is connected to a negative end of the first DC power supply (B1) and a positive end of a second DC power supply; one end of the Q2A switch (Q2A) is connected to the other of the Q1A switch (Q1A) One end of the Q2 switch (Q2) is connected to the negative end of the second DC power supply (B2); one end of the Q1 switch is connected to the positive end of the first DC power supply (B1), and the other end of the Q1 switch is Connecting the other end of the Q2A switch (Q2A), the other end of the Q2 switch (Q2), and the other end of the AC voltage source (AC1); one end of the Q3 switch (Q3) is connected to the first DC power supply ( a positive end of B1); and one end of the Q4 switch (Q4) is connected to the negative of the second DC power supply (B2) End, the other end of the Q4 switch (Q4) is connected to the other end of the Q3 switch (Q3), and the inductor (L1); wherein the first DC power source (B1) and the second DC power source (B2) Providing a DC voltage, through which the DC voltage is converted to an AC voltage source (AC1) via the single-phase third-order converter; wherein the Q1A switch (Q1A), the Q2A switch (Q2A), and the Q2 switch (Q2) The Q1 switch, the Q3 switch (Q3), and the Q4 switch (Q4) are metal oxide semiconductors (MOS).

The implementation steps of the voltage intermediate point clamped (NPC) switch switching table are as follows: The first step, as shown in FIG. 7A, is that the AC voltage source (AC1) is positive and its terminal voltage is lower than The first DC power (B1) voltage, and the current is positive; in the pulse width modulation (PWM) enable, the Q3 switch (Q3) is turned on, the Q2A switch (Q2A) is turned on, and the circuit is provided to make the positive current Increase (I++); the pulse width modulation (PWM) disables, the Q3 switch (Q3) turns on, providing a loop to reduce the positive current (I+).

The second step, as shown in FIG. 7B, is that the AC voltage source (AC1) is positive polarity and its terminal voltage is lower than the first DC power source (B1) voltage, and the current is negative polarity; (PWM) disable, the Q3 switch (Q3) is turned on, the Q1 switch (Q1) is turned on, and the loop is provided to increase the negative current (I--); the pulse width modulation (PWM) is enabled, the Q3 switch ( Q3) Conduction, the Q1A switch (Q1A) is turned on, and the circuit is provided to reduce the negative current (I-).

The third step, as shown in FIG. 7C, is that the AC voltage source (AC1) is positive polarity and its terminal voltage is greater than the first DC power source (B1) voltage, and the current is positive polarity; PWM) enable, the Q3 switch (Q3) is turned on, the Q2 switch (Q2) is turned on, and the loop is provided to increase the positive current (I++); the pulse width modulation (PWM) is disabled, and the Q3 switch (Q3) is turned on. The Q2A switch (Q2A) is turned on to provide a loop to reduce the positive current (I+).

The fourth step, as shown in FIG. 7D, is that the AC voltage source (AC1) is positive polarity and its terminal voltage is greater than the first DC power source (B1) voltage, and the current is negative polarity; PWM) disable, the Q3 switch (Q3) is turned on, the Q1A switch (Q1A) is turned on, and the loop is provided to increase the negative current (I--); the pulse width modulation (PWM) is enabled, the Q3 switch (Q3) Turn on, providing a loop to reduce the negative current (I-).

The fifth step, as shown in FIG. 7E, is that the AC voltage source (AC1) is negative polarity and the terminal voltage absolute value is lower than the second DC power source (B2) voltage, and the current is positive polarity; Variable (PWM) enable, the Q4 switch (Q4) is turned on, the Q2 switch (Q2) is turned on, the loop is provided to increase the positive current (I++), and the pulse width modulation (PWM) is disabled, the Q4 switch (Q4) The conduction, the Q2A switch (Q2A) is turned on, and the circuit is provided to reduce the positive current (I+).

The sixth step, as shown in FIG. 7F, is that the AC voltage source (AC1) is negative polarity and the terminal voltage absolute value is lower than the second DC power source (B2) voltage, and the current is negative polarity; Variable (PWM) disable, the Q4 switch (Q4) is turned on, the Q1A switch (Q1A) is turned on, the loop is provided to increase the negative current (I--); the pulse width modulation (PWM) is enabled, the Q4 switch (Q4) is turned on, providing a loop to reduce the negative current (I-).

The seventh step, as shown in FIG. 7G, is that the AC voltage source (AC1) is negative polarity and the terminal voltage absolute value is higher than the second DC power source (B2) voltage, and the current is positive polarity; Variable (PWM) enable, the Q4 switch (Q4) is turned on, the Q2A switch (Q2A) is turned on, and the loop is provided to increase the positive current (I++); the pulse width modulation (PWM) is disabled, the Q4 switch (Q4) Turn on, providing a loop to reduce the positive current (I+).

The eighth step, as shown in FIG. 7H, is that the AC voltage source (AC1) is negative polarity and the absolute value of the terminal voltage is higher than the voltage of the second DC power source (B2), and the current is negative polarity; Variable (PWM) disable, the Q4 switch (Q4) is turned on, the Q1 switch (Q1) is turned on, and the loop is provided to increase the negative current (I--); the pulse width modulation (PWM) is enabled, the Q4 switch (Q4) is turned on, the Q1A switch (Q1A) is turned on, and a loop is provided to reduce the negative current (I-).

In this implementation, the pulse width modulation (PWM) disable or enable is not fixed with the definition of the control mode. Its main function is to distinguish the controlled current from increasing or decreasing. Therefore, positive logic, negative logic, and positive can be used. The logic is mixed with negative logic. If the direction of the current is opposite to the direction of the voltage of the DC power supply, it indicates that the power factor is not equal to 1, and the AC power supply (AC1) at the output will be reversely transmitted to the DC terminal by the load grid voltage (Vgrid). The load is not limited to the AC grid power supply (Vgrid), and may be a passive load such as a pure resistor. In this case, the AC power source (AC1) is the AC output generated after the system is converted.

The above description is only intended to describe the preferred embodiments or embodiments of the present invention, which are not intended to limit the scope of the invention. That is, the equivalent changes and modifications made in accordance with the scope of the patent application of the present invention or the scope of the invention are covered by the scope of the invention.

Q1A‧‧‧Q1A switch

Q2A‧‧‧Q2A switch

Q2‧‧‧Q2 switch

Q1‧‧‧Q1 switch

Q3‧‧‧Q3 switch

Q4‧‧‧Q4 switch

L1‧‧‧Inductance

AC1‧‧‧ AC voltage source

C1‧‧‧ capacitor

B1‧‧‧First DC power supply

B2‧‧‧second DC power supply

Claims (11)

A modulation method for a single-phase three-step converter, the modulation method comprising the steps of: connecting a capacitor via an inductor using a single-phase third-order circuit, the single-order third-order circuit comprising: a Q1A switch, the Q1A switch One end is connected to a negative end of the first DC power supply, and a positive end of a second DC power supply; a Q2A switch, one end of the Q2A switch is connected to the other end of the Q1A switch; and a Q2 switch is connected to one end of the Q2 switch a negative end of the second DC power supply; a Q1 switch, one end of the Q1 switch is connected to the positive end of the first DC power supply, and the other end of the Q1 switch is respectively connected to the other end of the Q2A switch, and the other end of the Q2 switch One end, and the other end of the AC voltage source; a Q3 switch, one end of the Q3 switch is connected to the positive end of the first DC power source; and a Q4 switch, one end of the Q4 switch is connected to the negative end of the second DC power source One end of the Q4 switch is connected to the other end of the Q3 switch, and the inductor; and a single-phase third-order circuit is controlled by using a voltage intermediate point clamped (NPC) switch switching table; Intermediate voltage a clamp switch switching table, selecting a circuit of the current in the single-phase third-order circuit to reduce the switching frequency of the single-phase third-order circuit, and providing a DC-to-AC voltage conversion with low energy loss; The first step of the voltage intermediate point clamp switch switching table is: the output AC voltage source is positive polarity and the terminal voltage is lower than the first DC power supply voltage, and the current is positive polarity; Variable (PWM) enable, the Q3 switch is turned on, the Q2A switch is turned on, providing a loop to increase the positive current; and the pulse width modulation (PWM) is disabled, the Q3 switch is turned on, providing a loop to reduce the positive current. The modulation method of the single-phase three-step converter according to claim 1, wherein the first DC power source and the second DC power source provide a DC voltage, and the single-phase three-step converter is provided The DC voltage converts the AC voltage to the AC voltage source. The modulation method of the single-phase three-step converter according to claim 1, wherein the Q1A switch, the Q2A switch, the Q2 switch, the Q1 switch, the Q3 switch, the Q4 open relationship metal oxide semiconductor (MOS). The modulation method of the single-phase three-step converter according to claim 1, wherein the load AC voltage source of the single-order third-order circuit is changed to a passive load. The modulation method of the single-phase three-step converter according to the first aspect of the patent application, wherein the second step of the voltage intermediate point clamped (NPC) switch switching table is the output AC voltage source It is positive polarity and its terminal voltage is lower than the first DC power supply voltage, and the current is negative polarity; when the pulse width modulation (PWM) is disabled, the Q3 switch is turned on, the Q1 switch is turned on, and the loop is provided to make the negative current Increased; enabled by pulse width modulation (PWM), the Q3 switch is turned on, the Q 1A switch is turned on, and the loop is provided to reduce the negative current. The modulation method of the single-phase three-step converter according to the first aspect of the patent application, wherein the third step of the voltage intermediate point clamped (NPC) switch switching table is the output AC voltage source. It is positive polarity and its terminal voltage is greater than the first DC power supply voltage, and the current is positive polarity; the pulse width modulation (PWM) enables, the Q3 switch is turned on, the Q2 switch is turned on, and the loop is provided to increase the positive polarity current. In the pulse width modulation (PWM) disable, the Q3 switch is turned on, and the Q2A switch is turned on to provide a loop to reduce the positive current. The modulation method of the single-phase three-step converter according to the first aspect of the patent application, wherein the fourth step of the voltage intermediate point clamped (NPC) switch switching table is the output AC voltage source It is positive polarity and its terminal voltage is greater than the first DC power supply voltage, and the current is negative polarity; the pulse width modulation (PWM) is disabled, the Q3 switch is turned on, the Q1A switch is turned on, and the loop is provided to increase the negative current. In the pulse width modulation (PWM) enable, the Q3 switch is turned on, providing a loop to reduce the negative current. The modulation method of the single-phase three-step converter according to the first aspect of the patent application, wherein the fifth step of the voltage intermediate point clamped (NPC) switch switching table is The output AC voltage source is negative polarity and the terminal voltage absolute value is lower than the second DC power supply voltage, and the current is positive polarity; the pulse width modulation (PWM) enables, the Q4 switch is turned on, the Q2 switch is turned on, The loop is provided to increase the positive current; in the pulse width modulation (PWM) disable, the Q4 switch is turned on, the Q2A switch is turned on, and the loop is provided to reduce the positive current. The modulation method of the single-phase three-step converter according to the first aspect of the patent application, wherein the sixth step of the voltage intermediate point clamped (NPC) switch switching table is the output AC voltage source It is negative polarity and its terminal voltage absolute value is lower than the second DC power supply voltage, and the current is negative polarity; the pulse width modulation (PWM) is disabled, the Q4 switch is turned on, the Q1A switch is turned on, and the loop is provided to make the negative polarity The current is increased; the pulse width modulation (PWM) enables the Q4 switch to conduct, providing a loop to reduce the negative current. The modulation method of the single-phase three-step converter according to the first aspect of the patent application, wherein the seventh step of the voltage intermediate point clamped (NPC) switch switching table is the output AC voltage source For the negative polarity, the absolute value of the terminal voltage is higher than the second DC power supply voltage, and the current is positive polarity; the pulse width modulation (PWM) is enabled, the Q4 switch is turned on, the Q2A switch is turned on, and the circuit is provided to positive polarity. The current is increased; the pulse width modulation (PWM) is disabled, and the Q4 switch is turned on, providing a loop to reduce the positive current. The modulation method of the single-phase three-step converter according to the first aspect of the patent application, wherein the eighth step of the voltage intermediate point clamped (NPC) switch switching table is the output AC voltage source For the negative polarity, the absolute value of the terminal voltage is higher than the second DC power supply voltage, and the current is negative polarity; the pulse width modulation (PWM) is disabled, the Q4 switch is turned on, the Q1 switch is turned on, and the loop is provided to make the negative polarity The current is increased; the pulse width modulation (PWM) is enabled, the Q4 switch is turned on, the Q1A switch is turned on, and the loop is provided to reduce the negative current.