Inverter anti-magnetic saturation control method and device and inversion system

Abstract

The invention provides an anti-magnetic saturation control method for an inverter, which belongs to the field of power electronics and comprises the following steps of: sampling a primary side current instantaneous value of a transformer at an output voltage zero-crossing moment of the inverter; calculating the deviation between the current instantaneous value and a transformer primary side current sampling value half a period ahead of the zero-crossing moment, judging whether the deviation exceeds a set threshold value or not, if so, determining a compensation direction according to the deviation and the modulation wave, updating the current compensation amount according to the deviation and the compensation direction, injecting the updated compensation amount into the modulation wave, and outputting the updated compensation amount. The updated compensation amount is attenuated; if not, injecting the current compensation amount into the modulation wave, and attenuating the current compensation amount; the invention also provides an inverter anti-magnetic saturation control device and an inverter system. The DC magnetic bias of the inverter output transformer can be eliminated.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronics, and particularly to an inverter anti-magnetic saturation control method and device and an inverter system. BACKGROUND

[0002] In an ideal case, the power frequency inverter needs to be electrically isolated by a transformer, and the output of the inverter bridge arm should not contain a DC component. However, in actual engineering applications, for an inverter using SPWM modulation technology, due to the DC component of the reference sine wave, the DC bias in the sampling and conditioning circuit, the inconsistency of the switching device, and the asymmetry of the drive signal and the dead time, etc., the positive and negative volt-second values of the output voltage pulse sequence of the inverter in the fundamental period are unbalanced, causing DC magnetic bias. When the magnetic bias is serious, it will cause the transformer core to be saturated, increase the loss of the transformer, cause the output waveform to be distorted and the power device to be damaged, and even cause the inverter to be overturned, which will also have a serious impact on the normal operation of the AC load.

[0003] In order to eliminate the DC magnetic bias of the output transformer of the inverter, various solutions have been proposed in the prior art: (1) Current / voltage detection method: for example, the primary and secondary current detection method of the output transformer, which detects the primary and secondary currents of the transformer to eliminate the DC magnetic bias. However, this method is complex to control and requires sensors to be installed on the primary and secondary sides of the output transformer, which increases the cost and weakens the anti-interference ability. (2) Bridge arm voltage DC compensation method: this method detects the DC component of the output voltage sequence of the inverter bridge and compensates it in real time to suppress the DC component. For example, the Chinese patent application CN111130360A “Method for suppressing DC magnetic bias and harmonic current and photovoltaic inverter system” extracts the DC component on the primary side of the output transformer, amplifies the error of the DC component to obtain an adjustment voltage, adjusts the trigger pulse width of the SPWM through the adjustment voltage, so that the output pulse width tracks the DC component, and the average value is used to correct the reference sine wave to restore the symmetry of the positive and negative pulses of the SPWM waveform. The defects of this method are: when the output end of the inverter is connected to a half-wave rectifier type load, such as an electric kettle, a hair dryer, and a gear adjuster, the load only works in the half cycle of the sine wave, and the equivalent resistance of the transformer secondary side current is significantly different in the positive / negative half cycle, as shown in FIG. 1. Even if the SPWM modulation is perfect, the difference in the internal resistance voltage drop of the transformer primary and secondary coils will form an equivalent DC component to cause magnetic saturation. Since the DC component causing the magnetic saturation is caused by the load characteristics rather than the modulation error, this method cannot solve the problem of DC magnetic bias. Figure 2 SUMMARY ​

[0004] The technical problem to be solved by the present application is how to eliminate the DC bias magnetization of the output transformer of the inverter.

[0005] The present application solves the above technical problem by the following technical scheme: the inverter anti-magnetic saturation control method comprises the following steps: sampling the instantaneous value of the transformer primary side current at the zero-crossing moment of the inverter output voltage; calculating the deviation of the instantaneous value of the current from the sampling value of the transformer primary side current at the zero-crossing moment of the zero-crossing moment of the half cycle, judging whether the deviation exceeds the set threshold, if yes, determining the compensation direction according to the deviation and the modulation wave, updating the current compensation amount according to the deviation and the compensation direction, injecting the updated compensation amount into the modulation wave, and attenuating the updated compensation amount; if not, injecting the current compensation amount into the modulation wave, and attenuating the current compensation amount.

[0006] Beneficial effects: the present application collects the instantaneous value of the transformer primary side current at the zero-crossing moment of the inverter output voltage, judges whether the deviation of the instantaneous value of the transformer primary side current at the zero-crossing moment from the sampling value of the transformer primary side current at the zero-crossing moment of the half cycle exceeds the set threshold, so as to judge whether the transformer is saturated, when it is judged that the deviation exceeds the set threshold, it means that the transformer is saturated, the compensation direction is determined according to the deviation and the modulation wave, and the current compensation amount is updated according to the deviation and the compensation direction, the updated compensation amount is injected into the modulation wave, and after several cycles of adjustment, the transformer gradually exits saturation, so as to eliminate the DC bias magnetization of the output transformer of the inverter, solve the bias magnetization problem caused by half-wave rectification load, and compatibly process inherent errors such as modulation imbalance dead zone asymmetry and device parameter drift. In addition, by attenuating the compensation amount, the iron core can be stabilized at the critical saturation state.

[0007] Preferably, the deviation I c is calculated as follows:

[0008] I c = |I z (t0)| - |I z (t0-0.5T k )|

[0009] Wherein, I z (t0) is the instantaneous value of the transformer primary side current at the zero-crossing moment t0 of the inverter output voltage, I z (t0-0.5T k ) is the sampling value of the transformer primary side current at the zero-crossing moment t0 of the half cycle, and T k is the output cycle of the power frequency.

[0010] Beneficial effects: when the transformer iron core is close to saturation, the excitation current near the zero-crossing point of the power frequency changes nonlinearly, which is manifested as that the amplitude of the transformer primary side current is significantly higher or lower than the current sampling value near the zero-crossing point, if the deviation I cExceeding the set threshold I s (I c >I s or I c <-I s ), that is, the instantaneous value of the current I z (t0) is significantly higher or lower than the zero-crossing time by half a cycle (t0 - 0.5T). k The primary current sampling value I of the transformer z (t0-0.5T k This indicates that the transformer is saturated and compensation of the modulation wave is required.

[0011] Preferably, the process of determining the compensation direction based on the deviation includes: calculating the value of the modulation wave that is ahead of a set time at the zero-crossing moment, where the set time is less than half a cycle; if the value of the modulation wave has the same sign as the deviation, the compensation direction is negative; if the value of the modulation wave has the opposite sign to the deviation, the compensation direction is positive.

[0012] Beneficial effects: By judging whether the value of the modulation wave that is ahead of the set time Δt at the zero crossing moment has the same sign as the deviation, the present invention can determine the reverse direction of compensation. Regardless of the sensor installation direction (i.e., whether the current flows through the sensor in the forward or reverse direction), the compensation direction can be correctly determined, thereby automatically adapting to the installation direction of the primary current sensor.

[0013] Preferably, if the deviation I c Greater than the set threshold I s The zero-crossing time t0 is the transformer saturation time; if the deviation I c Less than the set threshold - I s The zero crossing time is half a cycle ahead of t0-0.5T. k This represents the transformer saturation point.

[0014] Preferably, if the value M(t0-Δt) of the modulated wave has the same sign as the deviation, the compensation sign is sign(I). c If M(t0-Δt))>0, decrease the current compensation amount; if the value of the modulated wave M(t0-Δt) is opposite in sign to the deviation, change the compensation sign to sign(I). c If M(t0-Δt))<0, increase the current compensation amount.

[0015] Preferred, updated compensation amount for:

[0016]

[0017] Where, ΔV dc K represents the current compensation amount. p The adjustment coefficient is denoted by 'sign', which represents the compensation sign and takes a value of 1 or -1. cFor the deviation, M(t0-Δt) is the value of the modulation wave ahead of the setting time Δt at the zero-crossing moment.

[0018] Preferably, when the inverter triggers the over-current protection, the adjustment coefficient K is increased p , the saturation current peak is suppressed, and when the over-current protection is released, the adjustment coefficient K p is gradually restored to the original value by multiplying by a decay factor β every half power frequency cycle, and 0<β<1.

[0019] Beneficial effects: the application synchronously starts the compensation algorithm, increases the adjustment coefficient, suppresses the saturation current peak, and realizes the cooperation with the system protection function when the inverter triggers the over-current protection through linkage with the over-current protection.

[0020] Preferably, the updated compensation amount or the current compensation amount is exponentially attenuated every half power frequency cycle.

[0021] Beneficial effects: the application can avoid the accumulation of the compensation amount to cause the core reverse magnetization, and the compensation amount is automatically attenuated to zero when the load returns to normal, so that the working point of the transformer core can return to the origin of the magnetization curve.

[0022] The application also provides an inverter anti-magnetic saturation control device, which comprises:

[0023] A current collection unit is configured to sample the instantaneous value of the transformer primary side current at the zero-crossing moment of the inverter output voltage.

[0024] A modulation wave dynamic compensation unit is configured to calculate the deviation of the current instantaneous value from the transformer primary side current sampling value ahead of half a cycle at the zero-crossing moment, judge whether the deviation exceeds a set threshold, if yes, determine the compensation direction according to the deviation and the modulation wave, update the current compensation amount according to the deviation and the compensation direction, inject the updated compensation amount into the modulation wave, and attenuate the updated compensation amount; and if not, inject the current compensation amount into the modulation wave and attenuate the current compensation amount.

[0025] The application also provides an inverter system comprising an SPWM full-bridge inverter and an output transformer, which adopts the inverter anti-magnetic saturation control method, the input end of the SPWM full-bridge inverter is connected to the modulation wave, the output end of the SPWM full-bridge inverter is connected to the input end of the output transformer, and the output end of the output transformer is connected to the load.

[0026] The application has the advantages that the existing primary side current sensor is reused without adding a detection circuit, and zero hardware cost is achieved; and the application can avoid switch noise interference in zero-crossing detection. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The waveform diagram of the transformer primary side current when the transformer is saturated.

[0028] Figure 2 Flow chart of the inverter anti-magnetic saturation control method provided for the embodiment 1 of the present application;

[0029] Figure 3 Flow chart of the inverter anti-magnetic saturation control method provided for the embodiment 1 of the present application;

[0030] Figure 4 Schematic diagram of the embodiment 1 of the present application in which the current compensation amount needs to be increased;

[0031] Figure 5 Schematic diagram of the embodiment 1 of the present application in which the current compensation amount needs to be reduced;

[0032] Figure 6 Waveform diagram of the primary side current of the transformer when the inverter anti-magnetic saturation control method provided for the embodiment 1 of the present application is used to quickly adjust the transformer when the transformer is connected to a half-wave load and saturation occurs;

[0033] Figure 7 Waveform diagram of the continuous operation current of the transformer when the inverter anti-magnetic saturation control method provided for the embodiment 1 of the present application is used to quickly adjust the transformer when the transformer is connected to a half-wave load and saturation occurs;

[0034] Figure 8 Schematic diagram of the inverter system provided for the embodiment 3 of the present application;

[0035] In the figure: 100, SPWM full-bridge inverter. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present application clearer and more apparent, the technical solutions of the present application are described clearly and completely below in combination with specific embodiments and with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0037] The core of the power frequency transformer is generally made of silicon steel sheet. When the transformer is close to saturation, the primary side current of the transformer changes abruptly due to the sharp change of the excitation current, and the shape of the abrupt change is often related to the saturation degree of the magnetic core. For example, when the transformer is connected to a half-wave load, the primary side current of the transformer is a half-wave current. When the transformer is close to saturation, the primary side current of the transformer changes abruptly, and the shape of the abrupt change is related to the saturation degree of the magnetic core. Figure 1As shown, when the transformer is saturated, the primary current of the transformer gradually increases, and due to the effect of the volt-second integral of the magnetic core saturation, the saturation usually starts before the zero-crossing of the inverter output voltage, and the excitation current reaches the peak at the zero-crossing point, at which time the saturation is the most serious (in actual operation, the start of saturation does not necessarily occur at the zero-crossing, but after stabilization, the saturation at the zero-crossing point is the most serious), if not compensated, the overcurrent protection will be triggered after multiple cycles, and even the power device will be damaged, the present application captures the current characteristics of the transformer core saturation in real time, dynamically modifies the SPWM modulation wave, and actively offsets the transformer magnetic bias effect, which belongs to an active treatment type solution, and the specific introduction is as follows:

[0038] Embodiment 1

[0039] As shown in Figure 2 and Figure 3 , the present embodiment provides an inverter anti-magnetic saturation control method, which comprises the following steps:

[0040] Step 1, sampling the instantaneous value I z (t0) of the primary current of the transformer at the zero-crossing time t0 of the inverter output voltage.

[0041] The present application realizes zero hardware cost by real-time acquisition of the instantaneous value of the primary current of the transformer through the current sensor of the transformer primary side without adding a detection circuit. When the transformer core is close to saturation, the excitation current near the power frequency zero-crossing point changes nonlinearly, which is manifested as that the amplitude of the primary current of the transformer is significantly higher or lower than the current sampling value near the zero-crossing point, for example: if the transformer is saturated at the zero-crossing time t0 of the inverter output voltage, the transformer will not be saturated at the zero-crossing time t0-0.5T k ) (opposite to the zero-crossing point); on the contrary, if the transformer is saturated at the zero-crossing time t0-0.5T k ), the transformer will not be saturated at the zero-crossing time t0 of the inverter output voltage. The present application can avoid the interference of switching noise in zero-crossing detection.

[0042] Step 2, calculating the deviation I z of the instantaneous value I k (t0) of the current and the sampling value I z (t0-0.5T k ) of the primary current of the transformer at the zero-crossing time t0-0.5T c , judging whether the deviation I c exceeds the set threshold I s , if yes, determining the compensation direction according to the deviation I c and the modulation wave, and updating the current compensation amount AV c according to the deviation I dcIf not, inject the updated compensation amount into the modulated wave and attenuate the updated compensation amount; otherwise, reduce the current compensation amount ΔV. dc Inject the modulated wave and attenuate the current compensation amount.

[0043] Among them, deviation I c The calculation method is as follows:

[0044] I c =|I z (t0)|-|I z (t0-0.5T k )|

[0045] Among them, I z (t0) is the instantaneous value of the transformer primary current at the zero-crossing moment t0 of the inverter output voltage, I z (t0-0.5T k T represents the sampled value of the transformer primary current at the zero-crossing time t0, which is half a cycle ahead. k This is the power frequency output cycle.

[0046] Judgment bias I c Does it exceed the set threshold I? s Set threshold I s The compensation accuracy is determined by a value typically set to 10% of the rated current, and a threshold I is set. s The smaller the value, the less pronounced the saturation at steady state. If the deviation I... c Exceeding the set threshold I s (I c >I s Or I c <-I s ), that is, the instantaneous value of the current I z (t0) is significantly higher or lower than the zero-crossing time by half a cycle (t0 - 0.5T). k The primary current sampling value I of the transformer z (t0-0.5T k This indicates that the transformer is saturated and requires compensation of the modulation wave to suppress transformer core saturation. If the deviation I... c It did not exceed the set threshold I s , that is -I s c s At that time, the current compensation amount will remain unchanged.

[0047] According to deviation I c Determine the saturation time t * , if the deviation I c Greater than the set threshold I s The zero-crossing time t0 is the transformer saturation time t. * ;If the deviation is I​​c Less than a set threshold - I s , the zero-crossing time t0-0.5T k is the transformer saturation time t * .

[0048] According to the deviation I c and the modulation wave, the compensation direction is determined by calculating the value of the modulation wave at the zero-crossing time t0 advanced by a set time Δt, and the set time Δt is greater than 0 and less than half a period 0.5T k , and in this embodiment, the set time Δt is advanced by a quarter of a period, i.e. 0.25T k ; if the value M(t0-0.25T k ) of the modulation wave is the same as the sign of the deviation, the compensation direction is negative, and at this time the compensation sign sign(I c ·M(t0-0.25T k ))>0, the current compensation amount ΔV dc is reduced to offset the saturation; if the value M(t0-0.25T k ) of the modulation wave is opposite to the sign of the deviation, the compensation direction is positive, and at this time the compensation sign sign(I c ·M(t0-0.25T k ))<0, the current compensation amount ΔV dc is increased to offset the saturation. The modulation wave is a sine wave, M=A·sin(ωT), where ω=50×2π.

[0049] The updated compensation amount is:

[0050]

[0051] Where ΔV dc is the current compensation amount, K p is the adjustment coefficient, K p ∈[0,1], and is usually a value between 0 and 1, for example, it can be 0.3 or 0.5, etc., sign is the compensation sign, and takes the value 1 or -1, I c is the deviation, and M(t0-Δt) is the value of the modulation wave at the zero-crossing time advanced by a set time Δt.

[0052] The present application can determine the compensation direction by judging whether the value of the modulation wave at the zero-crossing time t0 advanced by a set time Δt is the same as the sign of the deviation, as shown in Figure 4 and Figure 5 , for example, if the saturation time occurs at the zero-crossing time t0, and the zero-crossing time t0 is advanced by a set time Δt (for example, 0.25T k ).When the value of the modulated wave is positive, it indicates that the positive adjustment has caused the transformer to saturate, and the magnetic core deflects in the positive direction. Therefore, the next adjustment needs to reduce the current compensation amount to counteract the positive saturation. If the saturation occurs at the zero-crossing time t0, and the zero-crossing time t0 is ahead of the set time Δt (e.g., 0.25T), then the saturation is further affected. k When the value of the modulation wave is negative, it indicates that the negative adjustment has caused the transformer to saturate and the magnetic core to deflect in the negative direction. Therefore, the next adjustment needs to increase the current compensation amount to counteract the negative saturation.

[0053] If the saturation time occurs at the zero-crossing time t0, which is half a period ahead of t0-0.5T... k And the zero-crossing time t0 is ahead of the set time Δt (e.g., 0.25T). k When the value of the modulated wave is positive, it indicates that the negative adjustment has caused the transformer to saturate, and the magnetic core deflects in the negative direction. Therefore, the next adjustment needs to increase the current compensation amount to counteract the negative saturation. If the saturation time occurs at the zero-crossing time t0, which is half a cycle ahead of t0-0.5T,... k And the zero-crossing time t0 is ahead of the set time Δt (e.g., 0.25T). k When the value of the modulation wave is negative, it indicates that the positive adjustment has caused the transformer to saturate and the magnetic core to deflect in the positive direction. Therefore, the next adjustment needs to reduce the current compensation amount to counteract the positive saturation.

[0054] Therefore, the compensation direction can be correctly determined regardless of the sensor's installation orientation (i.e., whether the current flows through the sensor in the forward or reverse direction). If the sensor's installation orientation is reversed, the compensation direction will also be reversed accordingly, thus automatically adapting to the installation orientation of the primary current sensor.

[0055] When the inverter triggers overcurrent protection, increase the regulation coefficient K. p The adjustment coefficient K is usually used. p Increase it to 1.5 to 2 times the original value to suppress the peak saturation current. After the overcurrent protection is released, the adjustment coefficient K... p The inverter gradually restores its original value by multiplying by an attenuation factor β every half power frequency cycle, where 0 < β < 1. The attenuation factor β is typically set to 0.9. This invention, through linkage with overcurrent protection, synchronously activates a compensation algorithm when the inverter triggers overcurrent protection, increasing the regulation coefficient and suppressing the saturation current peak, thus achieving synergy with the system protection function.

[0056] In step 2, if the updated compensation amount is injected into the modulated wave, the resulting compensated modulated wave is: If the current compensation amount ΔV dc Injecting a modulated wave yields a compensated modulated wave of A·sin(ωT)+ΔV dc Every half power frequency cycle, the updated compensation amount or the current compensation amount is exponentially decayed, and the decayed compensation amount ΔVdc (n) = a * Delta V dc (n-1), Delta V dc (n-1) is the updated compensation or current compensation, Delta V dc (n-1) is the compensation before attenuation, attenuation coefficient a [0.85, 0.95]. The application can avoid the accumulation of compensation leading to the reverse bias of the core by setting the abnormal recovery mechanism. When the load returns to normal, the compensation automatically attenuates to zero, which can effectively make the transformer core operating point return to the origin of the magnetization curve.

[0057] The application collects the instantaneous value of the transformer primary current at the zero-crossing moment of the inverter output voltage, judges whether the deviation between the instantaneous value of the transformer primary current at the zero-crossing moment and the sampling value of the transformer primary current at the zero-crossing moment half a cycle ahead exceeds the set threshold, to determine whether the transformer is saturated. When the deviation exceeds the set threshold, it indicates that the transformer is saturated. The compensation direction is determined according to the deviation and the modulation wave, and the current compensation is updated according to the deviation and the compensation direction. The updated compensation is injected into the modulation wave. After several cycles of adjustment, the transformer gradually exits saturation, thereby eliminating the direct current bias of the inverter output transformer, solving the problem of bias caused by half-wave rectification load, and compatible with inherent errors such as modulation imbalance dead zone asymmetry and device parameter drift. In addition, by attenuating the compensation, the core can be stabilized in a critical saturation state.

[0058] When the load is a half-wave rectification load (such as an electric pot, a tuning hair dryer, etc.), the transformer appears to be biased, Figure 6 The transformer primary current waveform diagram of the application is shown in the figure. Under the sine wave, the half-cycle load causes the half-cycle volt-second integral to gradually saturate the transformer in the half-cycle. After the system is adjusted by the method, the saturation gradually decreases. After saturation, the primary current no longer increases, and the system runs stably, as shown in the figure. The method makes the transformer run in a near-saturation state (near-saturation means that the magnetic core is still saturated, which is related to the detection sensitivity preset value in the method, otherwise the method cannot be perceived). The algorithm design has a compensation gradually attenuating mechanism. When the abnormal load is removed or the saturation-causing condition is removed, the compensation is gradually eliminated, so that the inverter works in the magnetic core origin state. Figure 7

[0059] Embodiment 2

[0060] The difference between this embodiment and embodiment 1 is that the application provides an inverter anti-magnetic saturation control device, which comprises:

[0061] The current acquisition unit is used to sample the instantaneous value of the transformer primary current at the zero-crossing moment of the inverter output voltage.

[0062] ​The modulation wave dynamic compensation unit is used for calculating the deviation of the current instantaneous value and the transformer primary side current sampling value at the half cycle ahead of the zero crossing time, judging whether the deviation exceeds the set threshold, if yes, determining the compensation direction according to the deviation and the modulation wave, updating the current compensation amount according to the deviation and the compensation direction, injecting the updated compensation amount into the modulation wave, and attenuating the updated compensation amount; if no, injecting the current compensation amount into the modulation wave, and attenuating the current compensation amount. The updated compensation amount or the current compensation amount is exponentially attenuated every half power frequency cycle.

[0063] Wherein, the deviation I c is calculated as follows:

[0064] I c = |I z (t0)| - |I z (t0-0.5T k )|

[0065] Wherein, I z (t0) is the transformer primary side current instantaneous value at the zero crossing time t0 of the inverter output voltage, I z (t0-0.5T k ) is the transformer primary side current sampling value at the half cycle ahead of the zero crossing time t0, and T k is the power frequency output cycle.

[0066] The process of determining the compensation direction according to the deviation and the modulation wave includes: calculating the value of the modulation wave at the set time ahead of the zero crossing time, and the set time is less than half a cycle; if the value of the modulation wave and the sign of the deviation are the same, the compensation direction is negative; if the value of the modulation wave and the sign of the deviation are opposite, the compensation direction is positive.

[0067] If the deviation I c is greater than the set threshold I s , the zero crossing time t0 is the transformer saturation time t * ; if the deviation I c is less than the set threshold -I s , the half cycle t0-0.5T k ahead of the zero crossing time is the transformer saturation time t * .

[0068] If the value M(t0-Δt) of the modulation wave and the sign of the deviation are the same, the compensation sign sign(I c ·M(t0-Δt))>0, the current compensation amount is reduced; if the value M(t0-Δt) of the modulation wave and the sign of the deviation are opposite, the compensation sign sign(I c ·M(t0-Δt))<0, the current compensation amount is increased.

[0069] The updated compensation amount is:

[0070]

[0071] wherein, ΔV dc is the current compensation amount, K p is the adjustment coefficient, sign is the compensation sign, and takes the value of 1 or -1, I c is the deviation, and M(t0-Δt) is the value of the modulation wave at the zero-crossing time advanced by the set time Δt.

[0072] When the inverter triggers the over-current protection, the adjustment coefficient K p is increased to suppress the saturation current peak value, and when the over-current protection is released, the adjustment coefficient K p is multiplied by the attenuation factor β every half power frequency period, and gradually returns to the original value, 0<β<1.

[0073] Embodiment 3

[0074] The difference between this embodiment and embodiment 1 is that, referring to Figure 8 , this embodiment provides an inverter system, which comprises an SPWM full-bridge inverter 100 and an output transformer T2, and adopts the inverter anti-magnetic saturation control method in embodiment 1; the input end of the SPWM full-bridge inverter 100 is connected to a modulation wave, the modulation wave and a carrier wave are input to the driving end of four power tubes in the SPWM full-bridge inverter 100 after comparison and amplification, the output end of the SPWM full-bridge inverter 100 is connected to the input end of the output transformer T2, and the output end of the output transformer T2 is connected to a load.

[0075] The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to some technical features therein; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for controlling antimagnetic saturation in an inverter, characterized in that: The methods include: At the moment when the inverter output voltage crosses zero, sample the instantaneous value of the transformer primary current; The deviation between the instantaneous current value and the sampled value of the transformer primary current half a cycle ahead of the zero crossing time is calculated. It is determined whether the deviation exceeds the set threshold. If so, the compensation direction is determined based on the deviation and the modulation wave. The current compensation amount is updated based on the deviation and the compensation direction. The updated compensation amount is injected into the modulation wave and attenuated. If not, the current compensation amount is injected into the modulation wave and attenuated.

2. The inverter antimagnetic saturation control method according to claim 1, characterized in that: Deviation I c The calculation method is as follows: I c =|I z (t0)|-|I z (t0-0.5T k )| Among them, I z (t0) is the instantaneous value of the transformer primary current at the zero-crossing moment t0 of the inverter output voltage, I z (t0-0.5T k T represents the sampled value of the transformer primary current at the zero-crossing time t0, which is half a cycle ahead. k This is the power frequency output cycle.

3. The inverter antimagnetic saturation control method according to claim 2, characterized in that: The process of determining the compensation direction based on the deviation and the modulation wave includes: calculating the value of the modulation wave that is ahead of the set time at the zero-crossing moment, where the set time is less than half a cycle; if the value of the modulation wave has the same sign as the deviation, the compensation direction is negative; if the value of the modulation wave has the opposite sign to the deviation, the compensation direction is positive.

4. The inverter antimagnetic saturation control method according to claim 2, characterized in that: If the deviation I c Greater than the set threshold I s The zero-crossing time t0 is the transformer saturation time; if the deviation I c Less than the set threshold - I s The zero crossing time is half a cycle ahead of t0-0.5T. k This represents the transformer saturation point.

5. The inverter antimagnetic saturation control method according to claim 3, characterized in that: If the value of the modulated wave M(t0-Δt) has the same sign as the deviation, the compensation sign is sign(I). c If M(t0-Δt))>0, decrease the current compensation amount; if the value of the modulated wave M(t0-Δt) is opposite in sign to the deviation, change the compensation sign to sign(I). c If M(t0-Δt))<0, increase the current compensation amount.

6. The inverter antimagnetic saturation control method according to claim 1, characterized in that: Updated compensation amount for: Where, ΔV dc K represents the current compensation amount. p The adjustment coefficient is denoted by 'sign', which represents the compensation sign and takes a value of 1 or -1. c The deviation is M(t0-Δt), which is the value of the modulated wave that is ahead of the set time Δt at the zero crossing time.

7. The inverter antimagnetic saturation control method according to claim 6, characterized in that: When the inverter triggers overcurrent protection, increase the regulation coefficient K. p To suppress the peak saturation current, the adjustment coefficient K is adjusted after the overcurrent protection is released. p The original value is gradually restored by multiplying by the attenuation factor β every half power frequency cycle, where 0 < β < 1.

8. The inverter antimagnetic saturation control method according to claim 1, characterized in that: The updated compensation amount or the current compensation amount is exponentially decayed every half power frequency cycle.

9. An inverter antimagnetic saturation control device, characterized in that: The device includes: The current acquisition unit is used to sample the instantaneous value of the transformer primary current at the moment when the inverter output voltage crosses zero. The modulation wave dynamic compensation unit is used to calculate the deviation between the instantaneous current value and the sampled value of the transformer primary current half a cycle ahead of the zero crossing time, determine whether the deviation exceeds the set threshold, if so, determine the compensation direction based on the deviation and the modulation wave, update the current compensation amount based on the deviation and the compensation direction, inject the updated compensation amount into the modulation wave, and attenuate the updated compensation amount; if not, inject the current compensation amount into the modulation wave and attenuate the current compensation amount.

10. An inverter system, comprising an SPWM full-bridge inverter and an output transformer, characterized in that: The inverter antimagnetic saturation control method according to any one of claims 1-8 is adopted, wherein the input terminal of the SPWM full-bridge inverter is connected to the modulation wave, the output terminal of the SPWM full-bridge inverter is connected to the input terminal of the output transformer, and the output terminal of the output transformer is connected to the load.

Images