TWI798898B - Control method of three-phase three-wire inverter - Google Patents

Abstract

A control method of three-phase three-wire inverter is implemented by a control unit and includes: calculating a ratio of the amplitude of the three output phase voltages output from a first power switch to a sixth power switch of a three-phase three-wire inverter to a predetermined voltage value to obtain three amplitude ratios, calculating the three output phase currents output from the first power switch to the sixth power switch and multiply the three amplitude ratios to obtain three adjusted phase currents; generating three phase command voltages based on the three output phase voltages and the three adjustment phase currents; performing pulse width modulation on the three phase command voltages to generate a first control signal to a sixth control signal, and then respectively controlling the first power switch to the sixth power switch to be conductive or non-conductive.

Description

Control method of three-phase three-wire converter

The present invention relates to a control method, in particular to a control method for a three-phase three-wire converter.

With the rising awareness of environmental protection, the development of green energy such as solar or wind power is becoming more and more popular. The energy generated by these generator sets will first be stored in the battery, or converted from direct current to alternating current through a three-phase mains parallel converter, and then directly fed into the mains. Referring to Fig. 1, one of the known three-phase mains parallel converters is, for example, a three-phase three-wire converter, which is suitable for a DC input voltage V _dc and a mains voltage, and includes a first power switch to a sixth power switch Power switches M1~M6, a first inductor to a third inductor L1~L3, and a control unit 1, the control unit 1 controls the first power switch to the sixth power switch M1~M6 to be turned on or off respectively turned on to output three output phase voltages v _an , v _bn , v _cn and corresponding three output phase currents i _a , i _b , i _c . The DC input voltage V _dc is generated by a generator set _{of renewable energy, and the mains voltage includes three phase voltages va , v h ,} and v _c .

1 and 2, FIG. 2 is a control block diagram of the control unit 1, the control unit 1 includes a sinusoidal pulse width modulation module (Sinusoidal pulse width modulation, SPWM) 11, two orthogonal axis conversion modules Groups 12, 13, orthogonal axis inverse conversion module 14, two proportional integral modules 15, 16, two multiplication operation modules 17, 18, two addition operation modules 19, 20, and two subtraction operation modules 21, 22 . In addition, it should be emphasized that: the sine pulse width modulation module 11, the two orthogonal axis forward conversion modules 12, 13, the orthogonal axis inverse conversion module 14, the two proportional integral modules 15, 16, the Any one of the two multiplication operation modules 17, 18, the two addition operation modules 19, 20, and the two subtraction operation modules 21, 22 can be implemented by means of hardware (such as chips or semiconductor elements) The implementation may also be implemented by means of software (such as a digital signal processor (DSP) executing a corresponding program).

The two direct-quadrature transformation modules 12 and 13 perform direct-quadrature transformation (Direct-Quadrature Transformation) on the output phase voltages v _an , v _bn , v _cn and the output phase currents _ia , _ib , and _ic respectively. , to obtain two orthogonal axis voltages v _d , v _q and two orthogonal axis currents _id , i _q . Orthogonal axis transformation, also known as Park Transformation, is used to transform the three-phase voltage (or current) from the three-phase coordinate axis to the orthogonal axis (that is, the d-axis and the q-axis). The relationship of the orthogonal axis forward transformation is as follows Formulas (1) and (2), the two orthogonal axis voltages v _d and v _q are the two components of another orthogonal axis voltage v _o on the d axis and the q axis respectively, and the two orthogonal axis currents i _d and i _q are the other The two components of the orthogonal axis current i _o on the d axis and the q axis respectively, t is the time, and ω _c is the rotation speed of the orthogonal axis.

The control unit 1 also calculates the two orthogonal axis command voltages v _d,cmd and v _q,cmd according to formula (3), and then uses the orthogonal axis inverse conversion module 14 to command the two orthogonal axis voltages v _d,cmd , v _q,cmd perform orthogonal axis inverse transformation to obtain three phase command voltages v _a,cmd , v _b,cmd , v _c,cmd .

Wherein, L _f is the inductance value of each of the first inductor to the third inductor L1~L3, ω is equal to 2π*the frequency of the mains voltage, and the two variables x _d and x _q are respectively two The results of the proportional integral (PI) calculation of the error amounts _ed and e _q by the two proportional integral modules 15 and 16, that is, the calculation of the sum of the proportional gain and the integral gain of the error amounts ed and _{e q each} time . And the error amount ed calculated by the subtraction module 21 is equal to the orthogonal axis command current _{id ,cmd} minus the orthogonal axis current _id , and the error amount e _q calculated by the subtraction module 22 is equal to The other orthogonal axis command current i _q,cmd subtracts this orthogonal axis current i _q . And the multiplication operation of ω and L _f in the formula (3) is performed by the two multiplication operation modules 17,18, and the addition operation in the formula (3) is performed by the two addition operation modules 19,20 .

A real power P and a reactive power Q output by the three-phase three-wire converter are shown in formula (4). According to the specification requirements of the real power P and the imaginary power Q to be output by the three-phase three-wire converter during design, that is, the real power P and the imaginary power Q are known parameters, then the control unit 1 The two orthogonal axis command currents _id,cmd and i _q,cmd can be obtained by formula (5).

The sinusoidal pulse width modulation module 11 respectively compares the three phase command voltages v _{a, cmd} , v _{b, cmd} , v _{c, cmd} with the three triangular wave signals to generate a first control signal to a The sixth control signals SS1 - SS6 further control the conduction or non-conduction of the first power switch to the sixth power switch M1 - M6 respectively. Wherein, the second control signal SS2, the fourth control signal SS4, and the sixth control signal SS6 are respectively complementary to the first control signal SS1, the third control signal SS3, and the fifth control signal SS5 (for example, a One is logic 1 and the other is logic 0). For another example, when the phase command voltage v _b,cmd is greater than one of the triangular wave signals, the third control signal SS3 and the fourth control signal SS4 respectively control the third power switch M3 to turn on and the fourth power switch M4 is not conducting; and when the phase command voltage v _b,cmd is less than the triangular wave signal, the third control signal SS3 and the fourth control signal SS4 respectively control the third power switch M3 to be non-conducting and the fourth power switch M4 conduction.

In addition, the control unit 1 also detects the three phases of the three phase voltages v _a , v _b , and v _c of the mains voltage (for example, through a phase-locked loop (PLL) module), and controls the output The three phases of the three output phase voltages _van , v _bn , v _cn are respectively _{the same as the three phases of the three phase voltages va , v b ,} v _c .

However, in the control method performed by the aforementioned conventional control unit 1 for the three-phase three-wire converter, when the three phase voltages v _a , v _b , and v _c of the mains voltage are unbalanced, that is, When the voltage of at least one of them is different, the problem of real power oscillation of the three-phase three-wire converter will be caused. Therefore, how to solve the phenomenon of real power oscillation caused by the conventional technology, especially whether there is a simple and effective control method has become a problem to be solved.

Therefore, the object of the present invention is to provide a control method for a three-phase three-wire converter that solves the real power oscillation generated when the three-phase voltage is unbalanced.

Therefore, the present invention provides a control method for a three-phase three-wire converter, which is suitable for a three-phase three-wire converter, a DC input voltage, and a mains voltage. The three-phase three-wire converter includes a first power switch to a sixth power switch, a first inductor to a third inductor, and a control unit. The control method of the three-phase three-wire converter includes steps (A) to (D).

In step (A), the control unit calculates the ratios of the amplitudes of the three output phase voltages v _an , v _bn , v _cn outputted by the first power switch to the sixth power switch to a predetermined voltage value respectively. Three amplitude ratios k _a , k _b , k _c are obtained, wherein _ka , k _b , k _c are all positive numbers.

In step (B), the control unit calculates the three output phase currents _ia , _ib , and _ic outputted by the first power switch to the sixth power switch by multiplying the three amplitude ratios _ka , k _b , k _c , to obtain three adjusted phase currents.

In step (C), three phase command voltages are generated by the control unit according to the three output phase voltages and the three adjusted phase currents.

In step (D), the control unit performs pulse width modulation (PWM) on the command voltages of the three phases to generate a first control signal to a sixth control signal, and then respectively control the first power switch to The sixth power switch is turned on or not turned on.

In some implementation aspects, wherein, in step (C), the control unit performs orthogonal-axis forward conversion on the output phase voltages and the adjusted phase currents respectively to obtain two orthogonal-axis voltages and two orthogonal-axis voltages. current, and according to the two quadrature axis voltages and the two quadrature axis currents, two quadrature axis command voltages are generated, and then the quadrature axis inverse conversion is performed on the two quadrature axis command voltages respectively to obtain the three phase command voltages .

，計算該二個直交軸命令電 壓v_d,cmd、v_q,cmd。其中，v_d、v_q是該二個直交軸電壓，L_f是該第一電感器至該第三電感器之其中每一者的電感值，二個變數x_d、x_q分別是二個誤差量e_d、e_q作比例積分(PI)計算的結果，該誤差量e_d等於一直交軸命令電流i_d,cmd減去該直交軸電流i_d，該誤差量e_q等於 另一直交軸命令電流i_q,cmd減去該直交軸電流i_q。 In some implementation aspects, wherein, in step (C), the control unit is according to the formula:

, and calculate the two orthogonal axis command voltages v _d,cmd and v _q,cmd . Wherein, v _d and v _q are the voltages of the two orthogonal axes, L _f is the inductance value of each of the first inductor to the third inductor, and the two variables x _d and x _q are respectively two The error amount _ed and e _q is the result of proportional integral (PI) calculation, the error amount _ed is equal to the orthogonal axis command current _{id, cmd} minus the orthogonal axis current _id , the error amount e _q is equal to the other orthogonal axis The orthogonal axis current i _q is subtracted from the axis command current i _q ,cmd.

，計算該兩個直交軸命令電流i_d,cmd、i_q,cmd， 其中，P及Q分別是該三相三線式換流器所輸出的一實功率及一虛功率。 In some implementation aspects, wherein, in step (C), the control unit uses the formula:

, calculate the two orthogonal axis command currents _id,cmd , i _q,cmd , where P and Q are respectively a real power and a reactive power output by the three-phase three-wire converter.

In some implementation aspects, wherein, in step (D), the control unit includes a sinusoidal pulse width modulation module, and the sinusoidal pulse width modulation module respectively combines the three phase command voltages with the three Three triangle wave signals are compared to generate a first control signal to a sixth control signal. The second control signal, the fourth control signal, and the sixth control signal are complementary to the first control signal, the third control signal, and the fifth control signal, respectively.

In some implementation aspects, wherein, in step (D), when the sinusoidal pulse width modulation module determines that the phase command voltage v _a,cmd is greater than one of the triangular wave signals, output the first control signal and The second control signal respectively controls the conduction of the first power switch and the non-conduction of the second power switch; and when the sinusoidal pulse width modulation module determines that the phase command voltage v _a,cmd is smaller than the triangular wave signal, it outputs the The first control signal and the second control signal respectively control the first power switch to be off and the second power switch to be on.

When the sinusoidal pulse width modulation module judges that the phase command voltage v _b,cmd is greater than the other triangular wave signal, output the third control signal and the fourth control signal to control the third power switch to turn on and the The fourth power switch is not turned on; and when the sinusoidal pulse width modulation module determines that the phase command voltage v _{b, cmd} is smaller than the triangular wave signal, output the third control signal and the fourth control signal to control the third The power switch is not turned on and the fourth power switch is turned on.

When the sinusoidal pulse width modulation module determines that the phase command voltage v _{c, cmd} is greater than the other triangular wave signal, output the fifth control signal and the sixth control signal to control the fifth power switch to be turned on and the The sixth power switch is not turned on; and when the sinusoidal pulse width modulation module determines that the phase command voltage v _c,cmd is smaller than the triangular wave signal, output the fifth control signal and the sixth control signal to control the fifth The power switch is not turned on and the sixth power switch is turned on.

In some other implementation aspects, wherein, in step (A), the predetermined voltage value is a preset value.

In some other implementation aspects, wherein, in the step (A), the predetermined voltage value is the largest of the three amplitudes of the three output phase voltages.

In some other implementation aspects, wherein, in the step (A), the predetermined voltage value is the same two of the three amplitudes of the three output phase voltages.

The efficacy of the present invention lies in: the three amplitude ratios are calculated by the control unit to know the change ratios of the three output phase voltages in the amplitude, and the three output phase currents are respectively multiplied by the three amplitude ratios to obtain obtain the three adjusted phase currents such that Compared with the conventional control method, the control unit uses the three output phase voltages and the three adjusted phase currents to generate the three phase command voltages, and then generates the first control signal to the sixth control signal, so as to avoid the problem of real power oscillation of the three-phase three-wire converter when the three phase voltages of the mains voltage are unbalanced.

1: Control unit

11, 31: Sine pulse width modulation module

12, 13, 32, 33: Orthogonal axis forward conversion module

14, 34: Orthogonal axis reverse conversion module

15, 16, 35, 36: proportional integral module

17, 18, 37, 38: Multiplication operation module

19, 20, 39, 40: Addition operation module

21, 22, 41, 42: Subtraction operation module

S1~S4: steps

SS1~SS6: the first control signal ~ the sixth control signal

M1~M6: first power switch~sixth power switch

L1~L3: the first inductor~the third inductor

V _dc : DC input voltage

V1, V2: reference voltage

VDD: power supply voltage

Vin1: input voltage

Vout1: the first output voltage

Vout2: Second output voltage

Vex: Zero crossing indication signal

v _a , v _b , v _c : phase voltage

v _an , v _bn , v _cn : output phase voltage

v _d , v _q , v _d1 , v _d2 : orthogonal axis voltage

v _{a, cmd} , v _{b, cmd} , v _{c, cmd} : phase command voltage

v _{d, cmd} , v _{q, cmd} : Orthogonal axis command voltage

Iin1: input current

i _a , i _b , i _c : output phase current

i _a' , i _b' , i _c' : adjust the phase current

i _d , i _q , i _d1 , i _d2 : orthogonal axis current

i _d,cmd , i _q,cmd : orthogonal axis command current

x _d , x _q : variables

e _d , e _q : error amount

P1, P2: real power

R1~R6, R11~R17: resistors

C1, C2, C11~C13: Capacitors

D1, D2, D11, D12: Diodes

5: Voltage detection circuit

51~53, 62, 63: operational amplifier

6: Current detection circuit

61: Hall sensor

Other features and effects of the present invention will be clearly presented in the implementation manner with reference to the drawings, wherein: Fig. 1 is a block diagram, illustrating the control method of the conventional three-phase three-wire converter of the present invention and applicable A three-phase three-wire converter; Fig. 2 is a block diagram illustrating a control unit of a conventional three-phase three-wire converter; Fig. 3 is a flow chart illustrating the three-phase three-wire converter of the present invention An embodiment of the control method; Fig. 4 is a circuit diagram illustrating a voltage detection circuit of this embodiment; Fig. 5 is a circuit diagram illustrating a current detection circuit of this embodiment; Fig. 6 is a block diagram illustrating the A control unit of the embodiment; FIG. 7 is a schematic diagram illustrating a phenomenon of real power oscillation in the prior art; and FIG. 8 is a schematic diagram illustrating that the real power of this embodiment of the present invention does not oscillate The phenomenon.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are denoted by the same numerals.

Referring to Fig. 1, one embodiment of the control method of the three-phase three-wire converter of the present invention is applicable to a three-phase three-wire converter, a DC input voltage V _dc , and a mains voltage, the DC input voltage V _dc For example, it is generated by a generator set of renewable energy. The mains voltage is, for example, 220 volts and 60 Hz alternating current, and includes three phase voltages v _a , v _b , and v _c . The three-phase three-wire converter includes a first power switch to a sixth power switch M1-M6, a first inductor to a third inductor L1-L3, and a control unit 1. The first power switch M1 and the second power switch M2 in series, the third power switch M3 and the fourth power switch M4 in series, and the fifth power switch M5 and the sixth power switch M6 in series form a parallel connection , to receive the DC input voltage V _dc . The common electrical connection end of the first power switch M1 and the second power switch M2, the common electrical connection end of the third power switch M3 and the fourth power switch M4, and the fifth power switch M5 and the sixth power switch M5 The common electrical connection end of the switch M6 is respectively electrically connected to the first inductor to a third inductor L1-L3.

The control unit 1 generates a first control signal to a sixth control signal SS1~SS6 to respectively control the conduction or non-conduction of the first power switch to the sixth power switch M1~M6, so that the first power switch M1 The common electrical connection end of the second power switch M2, the common electrical connection end of the third power switch M3 and the fourth power switch M4, and the common electrical connection of the fifth power switch M5 and the sixth power switch M6 The terminals respectively output three output phase voltages v _an , v _bn , v _cn and corresponding three output phase currents i _a , i _b , i _c , that is, after converting the direct current of the direct current input voltage V _dc into alternating current, and then Feed directly into the mains.

Referring to FIG. 1 and FIG. 3 , the embodiment of the control method of the three-phase three-wire converter of the present invention includes steps S1-S4.

In step S1, the control unit 1 calculates the amplitudes of the three output phase voltages v _an , v _bn , v _cn outputted by the first power switch to the sixth power switch M1~M6 and a predetermined voltage value respectively Three amplitude ratios k _a , k _b , k _c are obtained, wherein k _a , k _b , k _c are all positive numbers. In more detail, the control unit 1 can detect the three output phase voltages v _an , v _bn , v _cn through a voltage detection circuit in the prior art to obtain the three output phase voltages v _an , v _bn , and the amplitude of v _cn . Alternatively, the control unit 1 may also include the voltage detection circuit. In this embodiment, the predetermined voltage value is a preset value, for example, the amplitude corresponding to the standard value of the mains voltage, that is, 311 volts (equal to 2 times the square root of 220).

Referring to Fig. 4 again, Fig. 4 illustrates a kind of voltage detecting circuit 5 that present embodiment adopts, and this voltage detecting circuit 5 comprises four resistors R1 (resistance=50k), four resistors R2 (resistance=50k) 120k), two resistors R3 (resistance = 2k), one resistor R4 (resistance value = 10k), a resistor R5 (resistance = 10k), two resistors R6 (resistance = 1k), three operational amplifiers 51~53, a capacitor C1 (capacity = 330p), a capacitor C2 ( Capacitance = 2u), and two diodes D1, D2, and are used to receive an input voltage Vin1 to output a first output voltage Vout1 and a zero-crossing indication signal Vex. The relationship between the first output voltage Vout1 and the input voltage Vin1 is shown in the following formula, the zero-crossing indication signal Vex is equal to logic 1 or logic 0, and when the input voltage Vin1 is equal to 0 each time, a zero-crossing occurs , the logic value of the zero-crossing indication signal Vex is changed (that is, from logic 0 to logic 1 or from logic 1 to logic 0).

The control unit 1 is, for example, a digital signal processor (DSP). The voltage range of the signal received by the digital signal processor is, for example, between 0 and 3.3 volts. Then, a power supply voltage VDD and a power supply voltage of the voltage detection circuit 5 The reference voltages V1 are 3.3 and 0.825 volts respectively, and the three output phase voltages _van , v _bn and v _cn between -311~311 volts are respectively received by the three voltage detection circuits 5 (that is, as the The input voltage Vin1) is used to output the three first output voltages Vout1 corresponding to 0-3.3 volts and the three zero-crossing indication signals Vex. The digital processor then samples the first output voltages Vout1 and the zero-crossing indication signals Vex to respectively obtain the amplitudes of the three output phase voltages _van , v _bn , v _cn and the three phases Zero crossing time point.

In step S2, the control unit 1 calculates the three output phase currents _ia , _ib , and _ic outputted by the first power switch to the sixth power switch M1~M6 respectively multiplied by the three amplitude ratios k _a , k _b , k _c , to obtain three adjusted phase currents i _a' , i _b' , i _c' . In more detail, the control unit 1 can detect the three output phase currents _ia , _ib , and _ic through a current detection circuit in the prior art to obtain the three output phase currents _ia , i _b , i _c size. Alternatively, the control unit 1 may also include the current detection circuit.

Referring to Fig. 5 again, Fig. 5 illustrates a kind of current detecting circuit 6 adopted in the present embodiment, and this current detecting circuit 6 comprises a Hall sensor 61, a resistor R11 (resistance=1k), a resistor Device R12 (resistance = 1k), a resistor R13 (resistance = 1k), a resistor R14 (resistance = 1k), a resistor R15 (resistance = 1k), a resistor R16 (resistance = 1k), a resistor R17 (resistance = 1k), two operational amplifiers 62, 63, a capacitor C11 (capacity = 330p), a capacitor C12 (capacity = 2u), a capacitor C13 (capacity = 2u ), and two diodes D11, D12, and are used to receive an input current Iin1 to output a second output voltage Vout2, the relationship between the second output voltage Vout2 and the input current Iin1 is shown in the following formula.

The voltage range of the signal received by the digital signal processor is, for example, between 0 and 3.3 volts, then the power supply voltage VDD and another reference voltage V2 of the current detection circuit 6 are respectively 3.3 and 0.825 volts, by three The current detection circuit 6 respectively receives the three output phase currents _ia , _ib , and _ic between -6~6 amperes (that is, as the input current Iin1), and outputs correspondingly 0~3.3 volts Between the three second output voltages Vout2. The digital processor then samples the second output voltages Vout2 to respectively obtain the amplitudes of the three output phase currents _ia , _ib , and _ic .

In step S3, the control unit 1 generates three phase command voltages according to the three output phase voltages _van , v _bn , v _cn and the three adjusted phase currents _ia' , _ib' , ic _' v _a,cmd , v _b,cmd , v _c,cmd . In more detail, refer to FIG. 6 again. FIG. 6 is a control block diagram of the control unit 1. The control unit 1 includes a sinusoidal pulse width modulation module 31, two orthogonal axis forward conversion modules 32, 33, Orthogonal axis inverse conversion module 34 , two proportional integral modules 35 , 36 , two multiplication operation modules 37 , 38 , two addition operation modules 39 , 40 , and two subtraction operation modules 41 , 42 . In addition, it should be emphasized that in this embodiment, the sine pulse width modulation module 31, the two orthogonal axis forward conversion modules 32, 33, the orthogonal axis inverse conversion module 34, the two proportional integral modules Groups 35, 36, the two multiplication operation modules 37, 38, the two addition operation modules 39, 40, and the two subtraction operation modules 41, 42 are implemented by the digital signal processor (DSP) corresponding In other embodiments, it can also be implemented in the form of hardware (such as chips or semiconductor devices).

The two orthogonal-axis forward conversion modules 32 and 33 perform orthogonal-axis forward conversion on the three output phase voltages v _an , v _bn , v _cn and the three adjusted phase currents i _a' , ib _' , and i _c' respectively , to obtain two orthogonal axis voltages v _d , v _q and two orthogonal axis currents _id , i _q . The relational expressions of the positive conversion of the orthogonal axis are as formulas (6) and (7). The two orthogonal axis voltages v _d and v _q are the two components of the other orthogonal axis voltage v _o on the d axis and the q axis respectively. The two orthogonal axis voltages The current _id and i _q are the two components of another orthogonal axis current i _o on the d axis and the q axis respectively, t is time, and ω _c is the rotation speed of the orthogonal axis.

The control unit 1 also calculates the two orthogonal axis command voltages v _d,cmd and v _q,cmd according to formula (8), and then uses the orthogonal axis inverse conversion module 34 to command the two orthogonal axis voltages v _d,cmd , v _q,cmd perform orthogonal axis inverse transformation to obtain three phase command voltages v _a,cmd , v _b,cmd , v _c,cmd .

Wherein, L _f is the inductance value of each of the first inductor to the third inductor L1~L3, ω is equal to 2π*the frequency of the mains voltage, and the orthogonal axis rotation speed ω _c =ω, two The variables x _d and x _q are the results of the proportional integral (PI) calculation of the two error quantities ed _and e _q by the two proportional integral modules 35 and 36 respectively, that is, for each error quantity ed _and e _q Computation of the sum of proportional gain and integral gain respectively. And the error amount ed calculated by the subtraction module 41 is equal to the orthogonal axis command current _{id , cmd} minus the orthogonal axis current _id , and the error amount e _q calculated by the subtraction module 42 is equal to The other orthogonal axis command current i _q,cmd subtracts this orthogonal axis current i _q . And the logical operations of multiplication and addition in the formula (8) are executed by the two multiplication operation modules 37 , 38 and the two addition operation modules 39 , 40 .

A real power P and a reactive power Q output by the three-phase three-wire converter are shown in formula (9). According to the specification requirements of the real power P and the imaginary power Q to be output by the three-phase three-wire converter during design, that is, the real power P and the imaginary power Q are known parameters, then the control unit 1 The two orthogonal axis command currents _id,cmd and i _q,cmd can be obtained by formula (10). For example, when the three-phase three-wire converter is designed to output currents of 2 amps, 4 amps, and 6 amps, the corresponding real power output is 933 watts, 1866 watts, and 2799 watts , and the corresponding virtual power to be output is 0 watts.

In step S4, the control unit 1 performs pulse width modulation (PWM) on the three phase command voltages v _{a, cmd} , v _{b, cmd} , v _{c, cmd} to generate the first control signal to the second The six control signals SS1-SS6 control the conduction or non-conduction of the first power switch to the sixth power switch M1-M6 respectively. Wherein, the second control signal SS2, the fourth control signal SS4, and the sixth control signal SS6 are respectively complementary to the first control signal SS1, the third control signal SS3, and the fifth control signal SS5 (for example, a One is logic 1 and the other is logic 0). In more detail, in this embodiment, the sinusoidal pulse width modulation module 31 respectively sets the three phase command voltages v _a,cmd , v _b,cmd , v _c,cmd with the three triangular wave signals respectively. comparison to generate the first control signal to the sixth control signal SS1˜SS6.

For another example, when the sine pulse width modulation module 31 judges that the phase command voltage v _a,cmd is greater than one of the triangular wave signals, it outputs the first control signal SS1 and the second control signal SS2 to control the The first power switch M1 is turned on and the second power switch M2 is not turned on; and when the sinusoidal pulse width modulation module 31 judges that the phase command voltage v _a,cmd is smaller than the triangular wave signal, it outputs the first control signal SS1 And the second control signal SS2 respectively controls the first power switch M1 to be non-conductive and the second power switch M2 to be conductive.

Similarly, when the sinusoidal pulse width modulation module 31 judges that the phase command voltage v _{b, cmd} is greater than the other triangular wave signal, it outputs the third control signal SS3 and the fourth control signal SS4 to control the second control signal SS4 respectively. The three power switches M3 are turned on and the fourth power switch M4 is not turned on; and when the sinusoidal pulse width modulation module 31 judges that the phase command voltage v _b,cmd is smaller than the triangular wave signal, output the third control signal SS3 and The fourth control signal SS4 respectively controls the third power switch M3 to be off and the fourth power switch M4 to be on.

Similarly, when the sinusoidal pulse width modulation module 31 judges that the phase command voltage v _c,cmd is greater than the other triangular wave signal, it outputs the fifth control signal SS5 and the sixth control signal SS6 to control the first The fifth power switch M5 is turned on and the sixth power switch M6 is not turned on; and when the sinusoidal pulse width modulation module 31 judges that the phase command voltage v _c,cmd is smaller than the triangular wave signal, it outputs the fifth control signal SS5 and The sixth control signal SS6 respectively controls the fifth power switch M5 to be off and the sixth power switch M6 to be on.

In addition, the digital signal processor of the control unit 1 also detects the three phases of the three phase voltages v _a , v _b , and v _c of the mains voltage, for example, through the other three voltage detections shown in FIG. 4 The other three zero-crossing indication signals Vex obtained by the circuit 5 control the phases of the three triangular wave signals of the sinusoidal pulse width modulation module 31, so that by judging the corresponding three phase voltages v _a , The phase relationship between the zero-crossing indication signals Vex of v _b , v _c and the zero-crossing indication signals _Vex corresponding to the three output phase voltages van , v _bn , v _cn is achieved to control the output The three phases of the three output phase voltages v _an , v _bn , v _cn are respectively the same as the three phases of the three phase voltages v _a , v _b , v _c .

Referring to Fig. 1, Fig. 2 and Fig. 7, Fig. 7 exemplarily illustrates that the three-phase three-wire converter known in the prior art is unbalanced in the three phase voltages v _a , v _b , and v _c of the mains voltage , that is, when the voltage of at least one of them is different, the orthogonal axis voltage v _d1 after the three output phase voltages _van , v _bn , and v _cn are transformed by the orthogonal axis will be shown in the timing diagram on the left of Figure 7 . And the orthogonal axis current _id1 after the three output phase currents _ia , _ib , and _ic are transformed by the orthogonal axis is shown in the timing diagram in the middle of FIG. 7 . Then multiply the two timing diagrams on the left and middle of FIG. 7 at the same time point, and a timing diagram of real power P1 on the right side of FIG. 7 will be obtained. Obviously, the real power P1 will oscillate between two values.

Referring to Fig. 1, Fig. 6 and Fig. 8, Fig. 8 exemplarily illustrates that by the control method of the three-phase three-wire converter of the present invention, when the three phase voltages v _a , v _b , and v _c of the mains voltage occur differently When balanced, that is, when at least one of them has different voltages, the orthogonal axis voltage v _d2 after the three output phase voltages v _an , v _bn , and v _cn are directly converted by the orthogonal axis will be as shown in the timing diagram on the left of Figure 8 Show. And the orthogonal axis current _id2 after the corresponding three adjusted phase currents _ia' , _ib' , and ic _' are transformed by the orthogonal axis forward conversion will be as shown in the timing diagram in the middle of FIG. 8 . Then multiply the two timing diagrams on the left and middle of FIG. 8 at the same time point, and a timing diagram of real power P2 on the right side of FIG. 8 will be obtained. Obviously, the real power P2 remains stable without oscillation.

In addition, it should be added that: in this embodiment, the predetermined voltage value is a preset value, such as the amplitude of the standard value of the mains voltage, then when the three phase voltages v _a , The voltage of at least one of _vb , _vc (that is, any one, any two or three) becomes larger or smaller, and the control method of the present invention can make the output real power compared with the mains power When the voltage is not unbalanced, it remains constant and stable without oscillation. In other embodiments, the predetermined voltage value is the largest of the three amplitudes of the three output phase voltages _van , v _bn , v _cn , or may be the three output phase voltages _van , The three amplitudes of v _hn and v _cn are equal to the size of the two. At this time, even if the predetermined voltage value is not equal to the amplitude of the standard value of the mains voltage, the control method of the present invention can also make the output The real power remains steady without oscillation.

To sum up, the three amplitude ratios are calculated by the control unit 1 to know the change ratios of the three output phase voltages v _an , v _bn , v _cn in amplitude, and the three output phase currents i _a , _ib , _ic are respectively multiplied by the three amplitude ratios to obtain the three adjusted phase currents _ia' , _ib' , ic _' , so that the control unit 1 is improved compared to the conventional control method To generate the three phase command voltages v a,cmd , v b according to the three output phase voltages v _an , v _bn , v _cn and the three adjusted phase currents i _a' , i _{b' ,} i _{c ' , cmd} , v _{c, cmd} , and then generate the first control signal to the sixth control signal SS1~SS6, so as to avoid the unbalance of the three phase voltages v _a , v _b , v _c of the mains voltage, which will As a result, the three-phase three-wire converter produces real power oscillations, so the purpose of the present invention can indeed be achieved.

But the above-mentioned ones are only embodiments of the present invention, and should not limit the scope of the present invention. All simple equivalent changes and modifications made according to the patent scope of the present invention and the content of the patent specification are still within the scope of the present invention. Within the scope covered by the patent of the present invention.

S1~S4: steps

Claims (9)

A control method for a three-phase three-wire converter, suitable for a three-phase three-wire converter, a DC input voltage, and a mains voltage, the three-phase three-wire converter includes a first power switch to a first power switch Six power switches, a first inductor to a third inductor, and a control unit, the control method of the three-phase three-wire converter includes: (A) using the control unit to calculate the first power switch to the The amplitudes of the three output phase voltages ( _van ), (v _bn ), (v _cn ) output by the sixth power switch are respectively compared with a predetermined voltage value to obtain three amplitude ratios k _a , k _b , k _c , where k _a , k _b , k _c are all positive numbers; (B) the control unit calculates the three output phase currents ( _ia ), (i _b ), ( _ic ) are multiplied by the three amplitude ratios k _a , k _b , k _c respectively to obtain three adjusted phase currents; (C) through the control unit according to the three output phase voltages and the three and (D) performing pulse width modulation (PWM) on the three phase command voltages by the control unit to generate a first control signal to a sixth control signal , and further control the first power switch to the sixth power switch to conduct or not conduct respectively. The control method for a three-phase three-wire converter as described in Claim 1, wherein, in step (C), the control unit performs orthogonal axis forward conversion on the output phase voltages and the adjusted phase currents, so that Obtain two orthogonal axis voltages and two orthogonal axis currents, and generate two orthogonal axis command voltages according to the two orthogonal axis voltages and the two orthogonal axis currents, and then command the two orthogonal axes The voltages are inversely converted on the quadrature axis to obtain the three phase command voltages. The control method of the three-phase three-wire converter as described in claim 2, wherein, in step (C), the control unit calculates the two orthogonal axis command voltages (v _{d, cmd} ), ( v _{q, cmd} ),

Wherein, (v _d ), (v _q ) are the two orthogonal axis voltages, L _f is the inductance value of each of the first inductor to the third inductor, and ω is equal to 2π*the mains voltage Frequency, the two variables (x _d ), (x _q ) are the results of proportional integral (PI) calculation of two error quantities (e _d ), (e _q ), respectively, and the error quantity (e _d ) is equal to the orthogonal axis The command current (i _d,cmd ) minus the orthogonal axis current ( _id ), the error amount (e _q ) is equal to the other orthogonal axis command current (i _q,cmd ) minus the orthogonal axis current (i _q ). The control method of the three-phase three-wire converter as described in claim 3, wherein, in step (C), the control unit calculates the two orthogonal axis command currents ( _{id, cmd} ), ( i _{q, cmd} ),

Wherein, P and Q are respectively a real power and a reactive power output by the three-phase three-wire converter. The control method for a three-phase three-wire converter as described in Claim 4, wherein, in step (D), the control unit includes a sinusoidal pulse width modulation module, and the sinusoidal pulse width modulation module respectively comparing the three phase command voltages (v _a,cmd ), (v _b,cmd ), (v _b,cmd ) with a first triangular wave signal, a second triangular wave signal, and a third triangular wave signal , to generate a first control signal to a sixth control signal, the second control signal, the fourth control signal, and the sixth control signal are respectively connected with the first control signal, the third control signal, and the first control signal The five control signals are complementary. The control method for a three-phase three-wire converter as described in Claim 5, wherein, in step (D), when the sinusoidal pulse width modulation module determines that the phase command voltage ( _{va, cmd} ) is greater than the When the first triangular wave signal is used, the first control signal and the second control signal are output to control the first power switch to be turned on and the second power switch to be turned off; and when the sine pulse width modulation module determines the phase command When the voltage (va _{, cmd} ) is less than the first triangular wave signal, the first control signal and the second control signal are output to respectively control the first power switch to be off and the second power switch to be on; when the sinusoidal pulse width When the modulation module judges that the phase command voltage (v _{b, cmd} ) is greater than the second triangular wave signal, it outputs the third control signal and the fourth control signal to control the third power switch to turn on and the fourth power switch to turn off, respectively. and when the sinusoidal pulse width modulation module determines that the phase command voltage (v _{b, cmd} ) is less than the second triangular wave signal, output the third control signal and the fourth control signal to control the third power respectively The switch is not turned on and the fourth power switch is turned on; when the sinusoidal pulse width modulation module determines that the phase command voltage (v _{c, cmd} ) is greater than the third triangular wave signal, it outputs the fifth control signal and the sixth The control signal respectively controls the conduction of the fifth power switch and the non-conduction of the sixth power switch; and when the sinusoidal pulse width modulation module determines that the phase command voltage (v _{c, cmd} ) is less than the third triangular wave signal, output The fifth control signal and the sixth control signal respectively control the fifth power switch to be off and the sixth power switch to be on. The control method for a three-phase three-wire converter as claimed in Claim 1, wherein, in step (A), the predetermined voltage value is a preset value. The control method for a three-phase three-wire converter as claimed in Claim 1, wherein, in step (A), the predetermined voltage value is the largest of the three amplitudes of the three output phase voltages. The control method for a three-phase three-wire converter as claimed in claim 1, wherein, in step (A), the predetermined voltage value is the same two of the three amplitudes of the three output phase voltages.

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