A three-phase inverter power grid phase loss detection device and method

Abstract

The present invention relates to the field of power electronics technology, and in particular to a three-phase inverter power grid phase loss detection device and method, wherein the method is applied to a device, wherein the device comprises a sampling module, a calculation module and a power grid frequency setting module; the sampling module is used to sample the DC bus voltage in the three-phase power grid; the power grid frequency setting module is electrically connected to the calculation module, and is used to change the DC bus voltage frequency to 50HZ or 60HZ; the calculation module is electrically connected to the sampling module and the power grid frequency setting module, respectively, and is used to calculate the amplitude of the bus voltage fundamental component under the corresponding voltage frequency, and compare it with a set threshold value to determine whether a three-phase power grid phase loss occurs. The present invention can accurately detect the situation where input phase loss protection is required, and has higher accuracy and reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a three-phase inverter power grid phase loss detection device and method. Background Art

[0002] AC-DC-AC voltage inverters are commonly used in variable frequency air conditioners. High-power inverters for industrial and commercial applications are mainly powered by three-phase power, and an uncontrolled rectification method is used to obtain a DC voltage for the inverter to generate a voltage with an adjustable frequency.

[0003] In general, the DC voltage ripple obtained by the three-phase uncontrolled rectifier bridge is very small. However, when the three-phase power supply is missing a phase, such as poor contact of the phase line, grid fault, or missing connection, the peak voltage on the grid side is 1.72 times that of the single-phase power supply, resulting in the bus voltage ripple after the three-phase uncontrolled rectifier bridge being much higher than that of the single-phase input power supply. This can easily cause the load after the inverter (such as compressors and fans) to operate unstably. At the same time, under the same working conditions and loads, the grid-side input current increases significantly, which can easily trigger the system overcurrent protection.

[0004] The existing technical solutions mainly use the fluctuation of the bus voltage after the rectifier bridge to indirectly infer whether the grid has a phase loss, but it is likely to be affected by changes in operating conditions (sudden load increase or decrease, light load, heavy load), filter inductance and capacitance, grid voltage distortion, interference (data glitches), etc., and is prone to false detection. Summary of the invention

[0005] The purpose of the present invention is to provide a three-phase inverter power grid phase loss detection device and method, which can accurately detect the situation where input phase loss protection is required, with higher accuracy and reliability.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] A three-phase inverter power grid phase loss detection device, comprising a sampling module, a calculation module and a power grid frequency setting module;

[0008] The sampling module is used to sample the DC bus voltage in the three-phase power grid;

[0009] The grid frequency setting module is electrically connected to the calculation module and is used to change the DC bus voltage frequency to 50HZ or 60HZ;

[0010] The calculation module is electrically connected to the sampling module and the grid frequency setting module respectively, and is used to calculate the amplitude of the bus voltage fundamental component at the corresponding voltage frequency, and compare it with the set threshold to determine whether a phase loss occurs in the three-phase grid.

[0011] Preferably, the sampling module includes a first power supply Ua, a second power supply Ub, a third power supply Uc, a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6, an inductor La, an inductor Lb, an inductor Lc, an inductor Ld, a polarity capacitor Vdc, a resistor R1, a resistor R2 and a resistor R3;

[0012] The first power supply Ua is electrically connected to one end of the inductor La, and the other end of the inductor La is electrically connected to the anode of the diode D1 and the cathode of the diode D2, respectively. The second power supply Ub is electrically connected to one end of the inductor Lb, and the other end of the inductor Lb is electrically connected to the anode of the diode D3 and the cathode of the diode D4, respectively. The third power supply Uc is electrically connected to one end of the inductor Lc, and the other end of the inductor Lc is electrically connected to the anode of the diode D5 and the cathode of the diode D6, respectively. The cathode of the diode D2, the cathode of the diode D4, the cathode of the diode D6, the cathode of the polarity capacitor Vdc, the other end of the resistor R2 and the other end of the resistor R3 are all grounded.

[0013] Preferably, the calculation module includes a proportional amplifier k1, a proportional amplifier k2, a proportional amplifier k3, a proportional amplifier k4, a low-pass filter LPF1, a low-pass filter LPF2, a low-pass filter LPF3, an adder-subtractor J1, an adder-subtractor J2, a multiplier M1, a multiplier M2, a squarer S1, a squarer S2, a square rooter S3, an integrator I1, a cosine generator COS, and a sine generator SIN;

[0014] The input end of the proportional amplifier k1 is electrically connected to the sampling module, the output end of the proportional amplifier k1 is electrically connected to the input end of the adder-subtractor J1 and the input end of the low-pass filter LPF1 respectively, the output end of the low-pass filter LPF1 is electrically connected to the input end of the adder-subtractor J1, the output end of the adder-subtractor J1 is electrically connected to the input end of the multiplier M1 and the input end of the multiplier M2 respectively, the output end of the multiplier M1 is electrically connected to the input end of the low-pass filter LPF2, the output end of the low-pass filter LPF2 is electrically connected to the input end of the proportional amplifier k2, the output end of the proportional amplifier k2 is electrically connected to the input end of the squarer S1, the output end of the squarer S1 is electrically connected to the input end of the adder-subtractor J2, and the output end of the adder-subtractor J2 is electrically connected to the input end of the square rooter S3;

[0015] The output end of the power grid frequency setting module is electrically connected to the input end of the proportional amplifier k3, the output end of the proportional amplifier k3 is electrically connected to the input end of the integrator I1, the output end of the integrator I1 is electrically connected to the input end of the cosine device COS and the input end of the sine device SIN respectively, the output end of the cosine device COS is electrically connected to the input end of the multiplier M1, the output end of the sine device SIN is electrically connected to the input end of the multiplier M2, the output end of the multiplier M2 is electrically connected to the input end of the low-pass filter LPF3, the output end of the low-pass filter LPF3 is electrically connected to the input end of the proportional amplifier k4, the output end of the proportional amplifier k4 is electrically connected to the input end of the squarer S2, the output end of the squarer S2 is electrically connected to the input end of the adder-subtractor J2, and the output end of the square rooter S3 outputs the amplitude of the fundamental component of the bus voltage.

[0016] A three-phase inverter power grid phase loss detection method, applied to a three-phase inverter power grid phase loss detection device as described above;

[0017] The method comprises:

[0018] S1. Sampling the DC bus voltage in the three-phase power grid through the sampling module 100 to obtain the actual value V of the DC bus voltage. dc ;

[0019] S2, according to the actual value of DC bus voltage V dc The ripple component in the DC bus voltage is calculated by the calculation module 200

[0020] S3, setting a first grid voltage frequency ω1 and a second grid voltage frequency ω2 through the grid frequency setting module 300; wherein the first grid voltage frequency ω1 is 50 Hz, and the second grid voltage frequency ω2 is 60 Hz;

[0021] S4, calculating the fundamental component frequency ω0 in the corresponding bus voltage ripple according to the first grid voltage frequency ω1 and the second grid voltage frequency ω2;

[0022] S5. According to the ripple component in the bus voltage and the fundamental component frequency ω0 in the two bus voltage ripples, and the fundamental component amplitude U in the bus ripple component under the first grid voltage frequency ω1 is calculated by the calculation module 200 50HZ_mag and the fundamental component amplitude U in the bus ripple component at the second grid voltage frequency 60HZ_mag ;

[0023] S6, the fundamental component amplitude U in the bus ripple component at the first grid voltage frequency ω1 50HZ_magAnd the fundamental component amplitude U in the bus ripple component at the second grid voltage frequency ω2 60HZ_mag The values ​​are compared with the respective set thresholds to determine whether a phase loss occurs in the three-phase power grid.

[0024] Preferably, in S1, the actual value of the DC bus voltage V dc It is expressed as:

[0025]

[0026] Among them, V dc represents the actual value of the bus voltage after being amplified by the proportional amplifier K1; k represents the amplification factor of the proportional amplifier K1; R1 represents the resistance value of the resistor R1; R2 represents the resistance value of the resistor R2; V dc-ab Indicates the sampled value of the DC bus voltage.

[0027] Preferably, in S2, the ripple component in the bus voltage is calculated by the calculation module 200 Specifically include:

[0028] S21. Express the DC bus voltage as:

[0029]

[0030] Where U0 represents the DC component of the DC bus voltage; Indicates the ripple component of the DC bus voltage; n indicates the harmonic order of n times the fundamental frequency; m is the order of all harmonic components; U na Indicates the amplitude of the cosine component of the ripple voltage at n times the fundamental frequency; U nb represents the amplitude of the sinusoidal component of the ripple voltage at n times the fundamental frequency; t represents time;

[0031] S22, extract the DC bus voltage ripple with harmonic order n=1:

[0032] S221, obtain the DC component U0 through the low-pass filter LPF1:

[0033] U0=LPF1(V dc ) (3)

[0034] Where LPF1() represents the effect of low-pass filter LPF1;

[0035] S222. Calculate the ripple component at twice the fundamental frequency when the harmonic order n = 1 frequency:

[0036] The DC bus voltage V dc Subtract the DC component U0 to get the ripple component

[0037]

[0038] According to formula (2), the ripple component It is expressed as:

[0039]

[0040] When the harmonic order n = 1 frequency, the ripple component at twice the fundamental frequency is expressed as:

[0041]

[0042] Among them U a Indicates the amplitude of the cosine component of the ripple voltage at the fundamental frequency, U b It represents the amplitude of the sinusoidal component of the ripple voltage at the fundamental frequency, and φ represents the ripple voltage at the fundamental frequency. The phase, U mag Indicates the amplitude of the fundamental component in the bus ripple component.

[0043] Preferably, in S4, the step of calculating the fundamental component frequency ω0 in the corresponding bus voltage ripple according to the first grid voltage frequency ω1 and the second grid voltage frequency ω2 specifically includes:

[0044] (1) When the grid frequency setting module 300 sets the first grid voltage frequency ω1 to 50 Hz, the fundamental component frequency ω0 in the bus voltage ripple is obtained as follows: ω0=4π×50;

[0045] (2) When the grid frequency setting module 300 sets the first grid voltage frequency ω1 to 50 Hz, the fundamental component frequency ω0 in the bus voltage ripple is obtained as: ω0=4π×60.

[0046] Preferably, in S5, according to the ripple component in the bus voltage and the fundamental component frequency ω0 in the two bus voltage ripples, and the fundamental component amplitude U in the bus ripple component under the first grid voltage frequency ω1 is calculated by the calculation module 200 50HZ_mag and the fundamental component amplitude U in the bus ripple component at the second grid voltage frequency 60HZ_mag ; Specifically include:

[0047] S51, DC bus voltage ripple Multiply by cos(ω0t), as shown in formula (7):

[0048]

[0049] S52, low-pass filter formula (7) is used to extract the amplitude U of the ripple voltage cosine component of the fundamental frequency a :

[0050]

[0051] Where LPF2() represents the effect of low-pass filter LPF2;

[0052] S53, calculate the amplitude U of the fundamental wave of the sine component in the bus voltage ripple component b :

[0053] DC bus voltage ripple Multiply by sin(ω0t), as shown in formula (9):

[0054]

[0055] The low-pass filter LPF3 of formula (8) can extract the amplitude of the sinusoidal component U of the fundamental wave part of the bus voltage ripple component. b :

[0056]

[0057] Where LPF3() represents the effect of low-pass filter LPF3;

[0058] S54, according to the ripple voltage cosine component amplitude U of the fundamental frequency in the bus voltage ripple component a The amplitude of the ripple voltage sinusoidal component of the fundamental frequency is U b , get the fundamental component amplitude U in the bus ripple component mag :

[0059]

[0060] S55, Substitute ω0 = 4π × 50 into S51 to S54, and obtain U 50HZ_mag ;

[0061] S56, Substitute ω0 = 4π × 60 into S51 to S54, and obtain U 60HZ_mag .

[0062] One of the above technical solutions has the following beneficial effects: using the bus voltage ripple frequency in the single-phase uncontrolled rectifier bridge to be twice the grid voltage frequency when there is a phase loss, by detecting the amplitude of the fundamental component of the grid voltage frequency twice in the bus voltage ripple, to detect whether there is a phase loss. If there is a phase loss when the grid voltage frequency is 50Hz, only the bus voltage ripple of 100Hz will be detected, and the 120Hz will not be detected; similarly, when the grid voltage frequency is 60Hz, the bus fluctuation amplitude of 100Hz is basically zero. As long as it is determined that the amplitude of any fundamental component of the twice grid voltage frequency 100Hz / 120Hz exceeds the set threshold, it can be considered that a phase loss has occurred, so there is no need to judge the grid frequency; if a phase loss occurs, the harmonic amplitude of the grid voltage frequency part in the bus voltage will increase significantly, and when there is no phase loss, the harmonic content of this frequency band is basically undetectable. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 It is a structural schematic diagram of a three-phase uncontrolled rectifier bridge in the prior art;

[0064] Figure 2 It corresponds to Figure 1 Schematic diagram of the relationship between bus ripple voltage and grid voltage;

[0065] Figure 3 It is a structural schematic diagram of an equivalent circuit when three phases are missing in the prior art;

[0066] Figure 4 It corresponds to Figure 3 Schematic diagram of the relationship between capacitor current harmonics and modulation mode;

[0067] Figure 5 It is a structural schematic diagram of a three-phase inverter power grid phase loss detection device of the present invention;

[0068] In the accompanying drawings: a sampling module 100 , a calculation module 200 , and a power grid frequency setting module 300 . DETAILED DESCRIPTION

[0069] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0070] like Figure 5 As shown, a three-phase inverter power grid phase loss detection device includes a sampling module 100, a calculation module 200 and a power grid frequency setting module 300;

[0071] The sampling module 100 is used to sample the DC bus voltage in the three-phase power grid;

[0072] The grid frequency setting module 300 is electrically connected to the calculation module 200 and is used to change the DC bus voltage frequency to 50 Hz or 60 Hz;

[0073] The calculation module 200 is electrically connected to the sampling module 100 and the grid frequency setting module 300 respectively, and is used to calculate the amplitude of the bus voltage fundamental component at the corresponding voltage frequency, and compare it with the set threshold to determine whether a phase loss occurs in the three-phase grid.

[0074] Combination Figure 1 and Figure 2 As shown in the figure, no matter how large the inductance and capacitance before and after the rectifier bridge are, or how large the working current of the whole machine is, or how the grid waveform is distorted, the frequency of the fluctuation part of the DC bus voltage Vdc on the capacitor side is 6 times the frequency of the grid voltage Va. It is only when the reactor or electrolytic capacitor is larger, or the working load is lighter, that the fluctuation amplitude of Vdc is very small. Generally, the fluctuation amplitude is less than 1V under light load conditions.

[0075] Combination Figure 3 and Figure 4 As shown in the figure, compared with the three-phase rectification, the bus voltage Vdc ripple frequency is twice the grid voltage Va frequency when the phase is missing, which has nothing to do with the selection of the inductance and capacitance before and after the rectifier bridge, or the working current of the whole machine, or how the grid waveform is distorted. It can be seen from the simulation in the figure above that the bus voltage fluctuation frequency is twice the grid voltage frequency when the phase is missing, and the fluctuation amplitude is large.

[0076] It can be concluded that when there is no phase loss, the fluctuation frequency of the bus voltage is 100Hz / 120Hz, and the harmonic content amplitude is very small, which is basically undetectable and will not cause false detection; however, if only the overall ripple amplitude of the bus voltage is detected, it is likely to be affected by changes in working conditions such as sudden load increase and decrease, light load, heavy load, filter inductance and capacitance, grid voltage distortion, interference such as data glitches, etc., which may easily lead to false detection;

[0077] The present invention utilizes the bus voltage ripple frequency in a single-phase uncontrolled rectifier bridge to be twice the grid voltage frequency when a phase is missing, and detects whether a phase is missing by detecting the amplitude of the fundamental component of the grid voltage frequency twice in the bus voltage ripple. If the phase is missing when the grid voltage frequency is 50Hz, only the bus voltage ripple of 100Hz will be detected, and the 120Hz will not be detected; similarly, when the grid voltage frequency is 60Hz, the bus fluctuation amplitude of 100Hz is basically zero. As long as it is determined that the amplitude of any fundamental component of the twice grid voltage frequency 100Hz / 120Hz exceeds the set threshold, it can be considered that a phase is missing, so there is no need to judge the grid frequency; if a phase is missing, the harmonic amplitude of the grid voltage frequency part in the bus voltage will increase significantly, while the harmonic content of this frequency band is basically undetectable when there is no phase missing.

[0078] In summary, the device of the present invention can accurately detect situations where input phase loss protection is required, and has higher accuracy and reliability.

[0079] To further illustrate, the sampling module 100 includes a first power supply Ua, a second power supply Ub, a third power supply Uc, a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6, an inductor La, an inductor Lb, an inductor Lc, an inductor Ld, a polarity capacitor Vdc, a resistor R1, a resistor R2, and a resistor R3;

[0080] The first power supply Ua is electrically connected to one end of the inductor La, and the other end of the inductor La is electrically connected to the anode of the diode D1 and the cathode of the diode D2, respectively. The second power supply Ub is electrically connected to one end of the inductor Lb, and the other end of the inductor Lb is electrically connected to the anode of the diode D3 and the cathode of the diode D4, respectively. The third power supply Uc is electrically connected to one end of the inductor Lc, and the other end of the inductor Lc is electrically connected to the anode of the diode D5 and the cathode of the diode D6, respectively. The cathode of the diode D2, the cathode of the diode D4, the cathode of the diode D6, the cathode of the polarity capacitor Vdc, the other end of the resistor R2 and the other end of the resistor R3 are all grounded.

[0081] To further illustrate, the calculation module 200 includes a proportional amplifier k1, a proportional amplifier k2, a proportional amplifier k3, a proportional amplifier k4, a low-pass filter LPF1, a low-pass filter LPF2, a low-pass filter LPF3, an adder-subtractor J1, an adder-subtractor J2, a multiplier M1, a multiplier M2, a squarer S1, a squarer S2, a square rooter S3, an integrator I1, a cosine device COS, and a sine device SIN;

[0082] The input end of the proportional amplifier k1 is electrically connected to the sampling module 100, the output end of the proportional amplifier k1 is electrically connected to the input end of the adder-subtractor J1 and the input end of the low-pass filter LPF1 respectively, the output end of the low-pass filter LPF1 is electrically connected to the input end of the adder-subtractor J1, the output end of the adder-subtractor J1 is electrically connected to the input end of the multiplier M1 and the input end of the multiplier M2 respectively, the output end of the multiplier M1 is electrically connected to the input end of the low-pass filter LPF2, the output end of the low-pass filter LPF2 is electrically connected to the input end of the proportional amplifier k2, the output end of the proportional amplifier k2 is electrically connected to the input end of the squarer S1, the output end of the squarer S1 is electrically connected to the input end of the adder-subtractor J2, and the output end of the adder-subtractor J2 is electrically connected to the input end of the square rooter S3;

[0083] The output end of the power grid frequency setting module 300 is electrically connected to the input end of the proportional amplifier k3, the output end of the proportional amplifier k3 is electrically connected to the input end of the integrator I1, the output end of the integrator I1 is electrically connected to the input end of the cosine analyzer COS and the input end of the sine analyzer SIN respectively, the output end of the cosine analyzer COS is electrically connected to the input end of the multiplier M1, the output end of the sine analyzer SIN is electrically connected to the input end of the multiplier M2, the output end of the multiplier M2 is electrically connected to the input end of the low-pass filter LPF3, the output end of the low-pass filter LPF3 is electrically connected to the input end of the proportional amplifier k4, the output end of the proportional amplifier k4 is electrically connected to the input end of the squarer S2, the output end of the squarer S2 is electrically connected to the input end of the adder-subtractor J2, and the output end of the square rooter S3 outputs the amplitude of the fundamental component of the bus voltage.

[0084] Specifically, the proportional amplifier k1, proportional amplifier k2, proportional amplifier k3 and proportional amplifier k4 are used to amplify the voltage signal at a built-in set ratio;

[0085] The low-pass filter LPF1, the low-pass filter LPF2 and the low-pass filter LPF3 are used to obtain a low-frequency voltage signal below a set critical value;

[0086] The adder-subtractor J1 and the adder-subtractor J2 are used to add or subtract two voltage signals according to a built-in set algorithm;

[0087] The multiplier M1 and the multiplier M2 are used to multiply two voltage signals by a built-in set algorithm;

[0088] The squarer S1 and the squarer S2 are used to square the voltage signal with a built-in set ratio;

[0089] The square root device S3 is used to square the voltage signal with a built-in set ratio;

[0090] The integrator I1 is used to integrate the voltage signal at a built-in set ratio;

[0091] The cosine generator COS is used to calculate the voltage signal at a built-in set ratio;

[0092] The sinusoidal generator SIN is used to calculate the voltage signal according to a built-in set ratio.

[0093] The calculation module 200 mainly calculates the amplitude of the corresponding frequency point through Fourier series, and the delay time is only 1 to 2 seconds. The calculation result is statistical, long-term, and continuous, and will not change suddenly due to accidental data, and there is no need to judge the working condition. The calculation module 200 has a simple circuit structure, which makes its calculation accuracy high and cost low.

[0094] A three-phase inverter power grid phase loss detection method, applied to a three-phase inverter power grid phase loss detection device as described above;

[0095] The method comprises:

[0096] S1. Sampling the DC bus voltage in the three-phase power grid through the sampling module 100 to obtain the actual value V of the DC bus voltage. dc ;

[0097] S2, according to the actual value of DC bus voltage V dc The ripple component in the DC bus voltage is calculated by the calculation module 200

[0098] S3, setting a first grid voltage frequency ω1 and a second grid voltage frequency ω2 through the grid frequency setting module 300; wherein the first grid voltage frequency ω1 is 50 Hz, and the second grid voltage frequency ω2 is 60 Hz;

[0099] S4, calculating the fundamental component frequency ω0 in the corresponding bus voltage ripple according to the first grid voltage frequency ω1 and the second grid voltage frequency ω2;

[0100] S5. According to the ripple component in the bus voltage and the fundamental component frequency ω0 in the two bus voltage ripples, and the fundamental component amplitude U in the bus ripple component under the first grid voltage frequency ω1 is calculated by the calculation module 200 50HZ_mag and the fundamental component amplitude U in the bus ripple component at the second grid voltage frequency 60HZ_mag ;

[0101] S6, the fundamental component amplitude U in the bus ripple component at the first grid voltage frequency ω1 50HZ_mag And the fundamental component amplitude U in the bus ripple component at the second grid voltage frequency ω2 60HZ_mag The values ​​are compared with the respective set thresholds to determine whether a phase loss occurs in the three-phase power grid.

[0102] The present invention utilizes the bus voltage ripple frequency in a single-phase uncontrolled rectifier bridge to be twice the grid voltage frequency when a phase is missing, and detects whether a phase is missing by detecting the amplitude of the fundamental component of the grid voltage frequency twice in the bus voltage ripple. If the phase is missing when the grid voltage frequency is 50Hz, only the bus voltage ripple of 100Hz will be detected, and the 120Hz will not be detected; similarly, when the grid voltage frequency is 60Hz, the bus fluctuation amplitude of 100Hz is basically zero. As long as it is determined that the amplitude of any fundamental component of the twice grid voltage frequency 100Hz / 120Hz exceeds the set threshold, it can be considered that a phase is missing, so there is no need to judge the grid frequency; if a phase is missing, the harmonic amplitude of the grid voltage frequency part in the bus voltage will increase significantly, while the harmonic content of this frequency band is basically undetectable when there is no phase missing.

[0103] In summary, the device of the present invention can accurately detect situations where input phase loss protection is required, and has higher accuracy and reliability.

[0104] To further illustrate, in S1, the actual value of the DC bus voltage V dc It is expressed as:

[0105]

[0106] Among them, V dc represents the actual value of the bus voltage after being amplified by the proportional amplifier K1; k represents the amplification factor of the proportional amplifier K1; R1 represents the resistance value of the resistor R1; R2 represents the resistance value of the resistor R2; V dc-ad Indicates the sampled value of the DC bus voltage.

[0107] To further illustrate, in S2, the ripple component in the bus voltage is calculated by the calculation module 200; specifically, it includes:

[0108] S21. Express the DC bus voltage as:

[0109]

[0110] Where U0 represents the DC component of the DC bus voltage; Indicates the ripple component of the DC bus voltage; n indicates the harmonic order of n times the fundamental frequency; m is the order of all harmonic components; U na Indicates the amplitude of the cosine component of the ripple voltage at n times the fundamental frequency; Unb represents the amplitude of the sinusoidal component of the ripple voltage at n times the fundamental frequency; t represents time;

[0111] Because it is only necessary to detect the ripple voltage when n=1 (i.e., twice the grid voltage frequency), the part n>1 does not need to be paid attention to.

[0112] S22, extract the DC bus voltage ripple with harmonic order n=1:

[0113] Because the bus voltage ripple component The DC signal is too small. For example, the general ripple size is 20-50V, while the DC value is 500V, and the ripple signal accounts for less than 0.1. Direct processing is prone to large errors, low accuracy, and large delays, so it needs to pass through the low-pass filter LPF1 first;

[0114] S221, obtain the DC component U0 through the low-pass filter LPF1:

[0115] U0=LPF1(V dc ) (3)

[0116] Where LPF1() represents the effect of low-pass filter LPF1;

[0117] S222. Calculate the ripple component at twice the fundamental frequency when the harmonic order n = 1 frequency:

[0118] The DC bus voltage V dc Subtract the DC component U0 to get the ripple component

[0119]

[0120] According to formula (2), the ripple component It is expressed as:

[0121]

[0122] When the harmonic order n = 1 frequency, the ripple component at twice the fundamental frequency is expressed as:

[0123]

[0124] Among them U a Indicates the amplitude of the cosine component of the ripple voltage at the fundamental frequency, U b It represents the amplitude of the sinusoidal component of the ripple voltage at the fundamental frequency, and φ represents the ripple voltage at the fundamental frequency. The phase, U mag Indicates the amplitude of the fundamental component in the bus ripple component.

[0125] The voltage amplitude of the ripple fundamental wave is Umag is the final calculation goal. Before that, the amplitude of the fundamental cosine component U needs to be calculated. a and the sine component amplitude U b .

[0126] Further explanation, in S4, the calculation of the fundamental component frequency ω0 in the corresponding bus voltage ripple according to the first grid voltage frequency ω1 and the second grid voltage frequency ω2 specifically includes:

[0127] (1) When the grid frequency setting module 300 sets the first grid voltage frequency ω1 to 50 Hz, the fundamental component frequency ω0 in the bus voltage ripple is obtained as follows: ω0=4π×50;

[0128] (2) When the grid frequency setting module 300 sets the first grid voltage frequency ω1 to 50 Hz, the fundamental component frequency ω0 in the bus voltage ripple is obtained as: ω0=4π×60.

[0129] Further explanation, in S5, according to the ripple component in the bus voltage and the fundamental component frequency ω0 in the two bus voltage ripples, and the fundamental component amplitude U in the bus ripple component under the first grid voltage frequency ω1 is calculated by the calculation module 200 50HZ_mag and the fundamental component amplitude U in the bus ripple component at the second grid voltage frequency 60HZ_mag ; Specifically include:

[0130] S51, DC bus voltage ripple Multiply by cos(ω0t), as shown in formula (7):

[0131]

[0132] The above equation has a unique DC component U a / 2, that is, the fundamental component of the bus voltage ripple component The amplitude of the cosine component of the fundamental frequency ripple voltage is extracted by low-pass filtering formula (7) through S52: a :

[0133]

[0134] Where LPF2() represents the effect of low-pass filter LPF2;

[0135] S53, calculate the amplitude U of the fundamental wave of the sine component in the bus voltage ripple component b :

[0136] DC bus voltage ripple Multiply by sin(ω0t), as shown in formula (9):

[0137]

[0138] The above equation has a unique DC component U b / 2, that is, the fundamental component of the bus voltage ripple component The amplitude of the sinusoidal component of the bus voltage ripple component can be extracted by low-pass filter LPF3. b :

[0139]

[0140] Where LPF3() represents the effect of low-pass filter LPF3;

[0141] S54, according to the ripple voltage cosine component amplitude U of the fundamental frequency in the bus voltage ripple component a The amplitude of the ripple voltage sinusoidal component of the fundamental frequency is U b , get the fundamental component amplitude U in the bus ripple component mag :

[0142]

[0143] S55, Substitute ω0 = 4π × 50 into S51 to S54, and obtain U 50HZ_mag ;

[0144] S56, Substitute ω0 = 4π × 60 into S51 to S54, and obtain U 60HZ_mag .

[0145] The technical principle of the present invention is described above in conjunction with specific embodiments. These descriptions are only for explaining the principle of the present invention and cannot be interpreted as limiting the scope of protection of the present invention in any way. Based on the explanations herein, those skilled in the art can associate other specific embodiments of the present invention without creative work, and these equivalent variations or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A three-phase inverter power grid phase loss detection device, characterized in that: It includes a sampling module, a calculation module and a power grid frequency setting module; The sampling module is used to sample the DC bus voltage in the three-phase power grid; The grid frequency setting module is electrically connected to the calculation module and is used to change the DC bus voltage frequency to 50HZ or 60HZ; The calculation module is electrically connected to the sampling module and the grid frequency setting module respectively, and is used to calculate the amplitude of the bus voltage fundamental component at the corresponding voltage frequency, and compare it with the set threshold value to determine whether a phase loss occurs in the three-phase grid; The sampling module includes a first power supply Ua, a second power supply Ub, a third power supply Uc, a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6, an inductor La, an inductor Lb, an inductor Lc, an inductor Ld, a polarity capacitor Vdc, a resistor R1, a resistor R2 and a resistor R3; The first power supply Ua is electrically connected to one end of the inductor La, and the other end of the inductor La is electrically connected to the anode of the diode D1 and the cathode of the diode D2, respectively. The second power supply Ub is electrically connected to one end of the inductor Lb, and the other end of the inductor Lb is electrically connected to the anode of the diode D3 and the cathode of the diode D4, respectively. The third power supply Uc is electrically connected to one end of the inductor Lc, and the other end of the inductor Lc is electrically connected to the anode of the diode D5 and the cathode of the diode D6, respectively. The cathode of the diode D1, the cathode of the diode D3 and the cathode of the diode D5 are all electrically connected to one end of the inductor Ld, the other end of the inductor Ld is respectively electrically connected to the anode of the polar capacitor Vdc, one end of the resistor R1 and one end of the resistor R3, the other end of the resistor R1 is electrically connected to the other end of the resistor R2, the cathode of the diode D2, the cathode of the diode D4, the cathode of the diode D6, the cathode of the polar capacitor Vdc, the other end of the resistor R2 and the other end of the resistor R3 are all grounded; The calculation module includes a proportional amplifier k1, a proportional amplifier k2, a proportional amplifier k3, a proportional amplifier k4, a low-pass filter LPF1, a low-pass filter LPF2, a low-pass filter LPF3, an adder-subtractor J1, an adder-subtractor J2, a multiplier M1, a multiplier M2, a squarer S1, a squarer S2, a square rooter S3, an integrator I1, a cosine generator COS, and a sine generator SIN; The input end of the proportional amplifier k1 is electrically connected to the sampling module, the output end of the proportional amplifier k1 is electrically connected to the input end of the adder-subtractor J1 and the input end of the low-pass filter LPF1 respectively, the output end of the low-pass filter LPF1 is electrically connected to the input end of the adder-subtractor J1, the output end of the adder-subtractor J1 is electrically connected to the input end of the multiplier M1 and the input end of the multiplier M2 respectively, the output end of the multiplier M1 is electrically connected to the input end of the low-pass filter LPF2, the output end of the low-pass filter LPF2 is electrically connected to the input end of the proportional amplifier k2, the output end of the proportional amplifier k2 is electrically connected to the input end of the squarer S1, the output end of the squarer S1 is electrically connected to the input end of the adder-subtractor J2, and the output end of the adder-subtractor J2 is electrically connected to the input end of the square rooter S3; The output end of the power grid frequency setting module is electrically connected to the input end of the proportional amplifier k3, the output end of the proportional amplifier k3 is electrically connected to the input end of the integrator I1, the output end of the integrator I1 is electrically connected to the input end of the cosine device COS and the input end of the sine device SIN respectively, the output end of the cosine device COS is electrically connected to the input end of the multiplier M1, the output end of the sine device SIN is electrically connected to the input end of the multiplier M2, the output end of the multiplier M2 is electrically connected to the input end of the low-pass filter LPF3, the output end of the low-pass filter LPF3 is electrically connected to the input end of the proportional amplifier k4, the output end of the proportional amplifier k4 is electrically connected to the input end of the squarer S2, the output end of the squarer S2 is electrically connected to the input end of the adder-subtractor J2, and the output end of the square rooter S3 outputs the amplitude of the fundamental component of the bus voltage.

2. A three-phase inverter power grid phase loss detection method, characterized in that: Applicable to a three-phase inverter power grid phase loss detection device as claimed in claim 1; The method comprises: S1. Sampling the DC bus voltage in the three-phase power grid through the sampling module to obtain the actual value V of the DC bus voltage dc ; S2, according to the actual value of DC bus voltage V dc The ripple component in the DC bus voltage is calculated by the calculation module S3, setting a first grid voltage frequency ω1 and a second grid voltage frequency ω2 by the grid frequency setting module; wherein the first grid voltage frequency ω1 is 50 Hz, and the second grid voltage frequency ω2 is 60 Hz; S4, calculating the fundamental component frequency ω0 in the corresponding bus voltage ripple according to the first grid voltage frequency ω1 and the second grid voltage frequency ω2; S5. According to the ripple component in the bus voltage and the fundamental component frequency ω0 in the two bus voltage ripples, and the fundamental component amplitude U in the bus ripple component under the first grid voltage frequency ω1 is calculated by the calculation module 50HZ_mag and the fundamental component amplitude U in the bus ripple component at the second grid voltage frequency 60HZ_mag ; S6, the fundamental component amplitude U in the bus ripple component at the first grid voltage frequency ω1 50HZ_mag And the fundamental component amplitude U in the bus ripple component at the second grid voltage frequency ω2 60HZ_mag The values ​​are compared with the respective set thresholds to determine whether a phase loss occurs in the three-phase power grid.

3. A three-phase inverter power grid phase loss detection method according to claim 2, characterized in that: In S1, the actual value of the DC bus voltage V dc It is expressed as: Among them, V dc represents the actual value of the bus voltage after being amplified by the proportional amplifier K1; k represents the amplification factor of the proportional amplifier K1; R1 represents the resistance value of the resistor R1; R2 represents the resistance value of the resistor R2; V dc-ad Indicates the sampled value of the DC bus voltage.

4. A three-phase inverter power grid phase loss detection method according to claim 3, characterized in that: In S2, the ripple component in the bus voltage is calculated by the calculation module Specifically include: S21. Express the DC bus voltage as: Where U0 represents the DC component of the DC bus voltage; Indicates the ripple component of the DC bus voltage; n indicates the harmonic order of n times the fundamental frequency; m is the order of all harmonic components; U na Indicates the amplitude of the cosine component of the ripple voltage at n times the fundamental frequency; U nb represents the amplitude of the sinusoidal component of the ripple voltage at n times the fundamental frequency; t represents time; S22, extract the DC bus voltage ripple with harmonic order n=1: S221, obtain the DC component U0 through the low-pass filter LPF1: U0=LPF1(V dc ) (3) Where LPF1() represents the effect of low-pass filter LPF1; S222. Calculate the ripple component at twice the fundamental frequency when the harmonic order n = 1 frequency: The DC bus voltage V dc Subtract the DC component U0 to get the ripple component According to formula (2), the ripple component It is expressed as: When the harmonic order n = 1 frequency, the ripple component at twice the fundamental frequency is expressed as: Among them U a Indicates the amplitude of the cosine component of the ripple voltage at the fundamental frequency, U b It represents the amplitude of the sinusoidal component of the ripple voltage at the fundamental frequency, and φ represents the ripple voltage at the fundamental frequency. The phase, U mag Expressed as the amplitude of the fundamental component in the bus ripple component.

5. A three-phase inverter power grid phase loss detection method according to claim 4, characterized in that: In S4, the calculation of the fundamental component frequency ω0 in the corresponding bus voltage ripple according to the first grid voltage frequency ω1 and the second grid voltage frequency ω2 specifically includes: (1) When the grid frequency setting module sets the first grid voltage frequency ω1 to 50 Hz, the fundamental component frequency ω0 in the bus voltage ripple is obtained as follows: ω0=4π×50; (2) When the grid frequency setting module sets the first grid voltage frequency ω1 to 50 Hz, the fundamental component frequency ω0 in the bus voltage ripple is obtained as: ω0=4π×60.

6. A three-phase inverter power grid phase loss detection method according to claim 5, characterized in that: In S5, according to the ripple component in the bus voltage and the fundamental component frequency ω0 in the two bus voltage ripples, and the fundamental component amplitude U in the bus ripple component under the first grid voltage frequency ω1 is calculated by the calculation module 50HZ_mag and the fundamental component amplitude U in the bus ripple component at the second grid voltage frequency 60HZ_mag ; Specifically include: S51, DC bus voltage ripple Multiply by cos(ω0t), as shown in formula (7): S52, low-pass filter formula (7) to extract the amplitude U of the ripple voltage cosine component of the fundamental frequency a : Where LPF2() represents the effect of low-pass filter LPF2; S53, calculate the amplitude U of the sinusoidal component of the fundamental wave part of the bus voltage ripple component b : DC bus voltage ripple Multiply by sin(ω0t), as shown in formula (9): The low-pass filter LPF3 of formula (8) can extract the amplitude of the sinusoidal component U of the fundamental wave part of the bus voltage ripple component. b : Where LPF3() represents the effect of low-pass filter LPF3; S54, according to the ripple voltage cosine component amplitude U of the fundamental frequency in the bus voltage ripple component a The amplitude of the ripple voltage sinusoidal component of the fundamental frequency is U b , get the fundamental component amplitude U in the bus ripple component mag : S55, Substitute ω0 = 4π × 50 into S51 to S54, and obtain U 50HZ_mag ; S56, Substitute ω0 = 4π × 60 into S51 to S54, and obtain U 60HZ_mag .

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