JP3595133B2 - Inverter output current waveform control method and inverter device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for controlling an output current waveform of an inverter used in a power converter and the like, and an inverter device.
[0002]
[Prior art]
The current control type inverter device is not only resistant to overload, but also suitable for interconnection with another power source. Some current control type inverter devices have a control method that has a command value of an output current and detects and feeds back the output current. In the inverter device of such a control method, since the accuracy is poor only with the current feedback, a method of adding the output voltage as compensation is also known. That is, the output terminal voltage of the inverter device can be represented by the vector sum of the output voltage (A) on the load side in the output circuit and the voltage loss (B) in the reactor provided in the output circuit. The gain is compensated by the feedback gain, and the portion (A) is compensated by adding the output voltage signal.
[0003]
2. Description of the Related Art Conventionally, as a current control type inverter device, one having several circuit configurations has been used in accordance with the intended use of the inverter device. FIG. 4 is a block diagram showing a configuration of a current control type inverter device that performs an interconnection operation with another power source (commercial system power source or the like). In FIG. 4, a DC / AC inverter 1 is driven by a drive signal from a PWM inverter drive signal circuit 2, converts input DC power into AC power, and converts the converted AC power into a reactor provided in an output circuit. The signal is sent out through an AC filter constituted by 14 and a capacitor 15.
[0004]
In such an inverter device, a current-voltage feedback loop is provided so that the output current of the DC / AC inverter 1 corresponds to the current command signal from the current command signal circuit 6. First, the current command signal will be described. That is, a synchronization signal detection circuit 22 is provided on the secondary side of the voltage transformer 12 provided on the output side of the DC / AC inverter 1, and the voltage of the other power supply which is a detection signal of the voltage transformer 12 is provided here. Detects signal synchronization. The synchronization detection signal detected by the synchronization signal detection circuit 22 is input to the unit sine wave signal generation circuit 24. The unit sine wave signal generation circuit 24 generates a unit sine wave signal (current command signal) based on the input synchronization detection signal. The unit sine wave signal generated by the unit sine wave signal circuit 24 is input to the multiplier 25, where it is multiplied by the power command signal 10, and the multiplication result is output to the current command signal circuit 6. The current command signal circuit 6 outputs the input multiplication result of the multiplier 25 to the subtractor 5.
[0005]
On the other hand, at the output end of the DC / AC inverter 1, a current signal is detected by the current detector 11, and this current signal is fed back to the subtractor 5. The subtractor 5 calculates a deviation between the current signal and the above-described current command signal. The deviation calculated by the subtracter 5 is output to the adder 3 after being amplified by the gain 4.
[0006]
Further, the detection signal of the voltage transformer 12 is averaged in the averaging circuit 21 and then multiplied by the unit sine wave signal in the multiplier 23 to become a sine wave voltage command signal, which is output to the adder 3. You. The adder 3 adds the sine wave voltage command signal and the amplified signal of the above-described deviation, and outputs an inverter drive signal as a result of the addition to the PWM inverter drive signal circuit 2. The PWM inverter drive signal circuit 2 drives the DC / AC inverter 1 based on the input inverter drive signal.
[0007]
[Problems to be solved by the invention]
In the conventional voltage compensation method described above, the voltage signal detected from the output circuit of the DC / AC inverter 1 is averaged instead of being applied to the current command signal as compensation, and is added to the output of the gain 4. That is, the detection signal (voltage signal of the inverter output) of the voltage transformer 12 is averaged by the averaging circuit 21, and the averaged result is multiplied by the multiplier 23 with the unit sine wave signal to obtain a sine wave. A voltage command signal is created, and the sine wave voltage signal is added to the gain 4 output as compensation.
[0008]
Therefore, even when the output voltage waveform is distorted, the distorted waveform is not added to the inverter drive signal component as it is, and the waveform accuracy can be improved to some extent. However, when a sudden change occurs in the voltage of the other power supply when performing interconnection with another power supply, the response of the inverter output current may be delayed by the averaging circuit 21 and may cause an output overcurrent.
[0009]
Further, even when the voltage of the other power supply is slightly distorted, it is difficult to adjust to the current control of the system interconnection inverter which requires an output current without distortion.
[0010]
In addition, since no countermeasures have been taken to reduce distortion due to disturbance factors in current feedback, non-linear effects caused by the fact that the collector current when a switch element such as an IGBT constituting an inverter main circuit is on is not proportional to the on-time, etc. In addition, there is a problem that an odd-order output waveform is distorted.
[0011]
However, such a problem can be solved by canceling disturbance due to nonlinearity, as long as the gain at the gain 4 can be made infinite. However, making the gain of the gain 4 infinite is impractical because the feedback control system becomes unstable, and does not solve the problem.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problem in the related art, in the present invention, the voltage compensation method maintains a high-speed response to a system voltage fluctuation by directly adding a voltage signal detected from an output circuit as compensation. On the other hand, the above control alone cannot compensate for the distortion component generated in the current feedback control system or the distortion component generated by adding the voltage signal as it is. Therefore, the current command signal is corrected in real time by a current command correction waveform created by integrating an error waveform between the current waveform of the inverter output and the waveform of the current command signal, thereby canceling these distortion components.
[0013]
Specifically, the present invention is configured as follows. In other words, the invention according to claim 1 of the present invention provides an inverter output current having a current feedback that amplifies a deviation between a current command signal created according to an inverter output current and the inverter output current to generate an inverter drive signal. In a waveform control method, a current command correction waveform is created by integrating an error waveform between a waveform of the inverter output current and a waveform of the current command signal in a synchronized predetermined cycle, and a current command correction waveform is generated in accordance with the current command correction waveform. The present invention is characterized in that the current command signal is corrected, thereby having the following operation. That is, when a steady distortion component is present in the inverter output current, a current command correction waveform is formed so as to cancel the steady distortion, and the current command signal is corrected, so that the amplification factor of the deviation is extremely increased. Without this, it is possible to perform low-distortion current feedback control.
[0014]
The invention according to claim 7 of the present invention is an inverter device having a current feedback that amplifies a deviation between a current command signal created according to an inverter output current and the inverter output current to generate an inverter drive signal, As the current command signal, current command signal generating means for generating a current command signal consisting of a sine wave signal having a fixed amplitude synchronized with the main voltage of the inverter , and synchronizing an error waveform between the inverter output current and the current command signal. Current command signal correction means for correcting the current command signal in accordance with a current command correction waveform created by integrating at a predetermined cycle , and amplitude control means for changing the amplitude of the corrected current command signal based on an inverter output power command. And has the following effects. That is, when a steady distortion component is present in the inverter output current, a current command correction waveform is formed so as to cancel the steady distortion, and the current command signal is corrected, so that the amplification factor of the deviation is extremely increased. Without this, it is possible to perform low-distortion current feedback control. In addition, since the waveform of the current command signal can be instantaneously changed in response to the change in the output power command, the responsiveness of the current command signal is improved.
[0015]
The invention according to claim 3 of the present invention is the inverter output current waveform control method according to claim 1 or 2, wherein an error waveform between the inverter output current waveform and the current command signal waveform is integrated. Previously, the feature is that the waveform of the inverter output current is normalized by the amplitude of the current command signal, thereby having the following operation. That is, before calculating the error waveform between the waveform of the inverter output current and the waveform of the current command signal, the waveform of the inverter output current is normalized by the amplitude of the current command signal. The current command signal corrected by use has almost no fundamental frequency component, and includes only harmonic distortion components to be canceled. As a result, it is possible to prevent the response speed of the fundamental wave component to the output power command from decreasing.
[0016]
According to a fourth aspect of the present invention, there is provided the inverter output current waveform control method according to the first aspect, wherein a sine wave signal having a fixed amplitude synchronized with an inverter output voltage is used as the current command signal. Normalizing the inverter output current with the amplitude of the sine wave signal, correcting the current command signal with a current command correction waveform created by integrating an error waveform between the normalized inverter output current and the sine wave signal, and correcting the current command signal. The characteristic feature is that the amplitude of the current command signal is changed based on the inverter output power command, thereby having the following operation. That is, the operation is the same as that of the control method of the second and third aspects, and the configuration is simplified.
[0017]
According to a fifth aspect of the present invention, there is provided the method of controlling an output current waveform of an inverter according to any one of the first to fourth aspects, wherein a system voltage waveform is detected and a voltage proportional to the detected system voltage waveform is detected. It is characterized in that a feedforward signal is added to the inverter drive signal, and has the following effect. That is, even when a change occurs in the system voltage, the change is instantaneously reflected in the inverter drive signal, so that a faster response of the inverter output can be obtained, and the stability at the time of system fluctuation is enhanced.
[0018]
An invention according to claim 6 of the present invention is the inverter output current waveform control method according to claim 5, wherein the voltage feedforward signal is changed so as to cancel the fluctuation of the DC input voltage of the inverter. It has the following features. That is, even when the DC input voltage of the inverter fluctuates, the fluctuation is canceled out by the inverter drive signal, and the stability when the DC input of the inverter fluctuates is increased.
[0019]
The invention according to claim 7 of the present invention is an inverter device having a current feedback that amplifies a deviation between a current command signal created according to an inverter output current and the inverter output current to generate an inverter drive signal, As the current command signal, current command signal generating means for creating a current command signal consisting of a sine wave signal having a fixed amplitude synchronized with an inverter output voltage, and integrating an error waveform between the inverter output current and the current command signal. Current command signal correction means for correcting the current command signal according to the current command correction waveform created in the above manner, and amplitude control means for changing the amplitude of the corrected current command signal based on the inverter output power command. Which has the following effect. That is, when a steady distortion component is present in the inverter output current, a current command correction waveform is formed so as to cancel the steady distortion, and the current command signal is corrected, so that the amplification factor of the deviation is extremely increased. Without this, it is possible to perform low-distortion current feedback control. In addition, since the waveform of the current command signal can be instantaneously changed in response to the change in the output power command, the response of the current signal signal is improved.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
First Embodiment FIG. 1 is a block diagram of an inverter device implementing a method for controlling an output current waveform of an inverter according to a first embodiment of the present invention. The present invention is embodied in an inverter device that operates in connection with a commercial system power supply.
[0021]
This inverter device includes a DC / AC inverter 1 for converting DC power into AC power synchronized with a commercial system power supply, a PWM inverter drive signal circuit 2 for driving the DC / AC inverter 1, and an output of the DC / AC inverter circuit 1. The reactor 14 and the capacitor 15 which are provided in the circuit and constitute the AC filter F, the current detector 11 provided at the input terminal of the AC filter F, and the voltage transformer 12 provided at the output terminal of the AC filter F Have.
[0022]
Further, the inverter device includes a current command signal generating means 16 for generating a current command signal AS corresponding to the inverter output current, and a current command signal correcting means 17 for correcting the current command signal AS to create a corrected current command signal ASc. And an amplitude control means 18 for changing the amplitude of the correction current command signal ASc based on the power command signal (inverter output power command) 10 to generate a reference current signal SS. A subtractor 5 that generates a current error signal Ie by subtraction, a gain 4 that amplifies the current error signal Ie to generate an error amplified signal Iea, and an inverter drive by adding the voltage feedforward signal FF to the error amplified signal Iea Normalizing the output current Is of the inverter and the voltage feed signal addition means 19 for generating the signal ID; Create a normalized output current signal Isn and a normalizing circuit 33 supplies the current command signal correction means 17.
[0023]
The current command signal generating means 16 includes a synchronization signal detection circuit 22 for detecting the synchronization of the voltage signal Vs of the commercial power supply, and a current consisting of a unit sine wave signal based on the output (synchronization detection signal Sy) of the synchronization signal detection circuit 22. A unit sine wave signal generation circuit 24 for generating the command signal AS.
[0024]
The current command signal correcting means 17 subtracts the normalized output current signal Isn from the current command signal AS to generate a normalized error signal Aa, and integrates the normalized error signal Aa to generate a current command corrected waveform signal. An error waveform integration circuit 34 for generating Aai and an adder 31 for adding a current command correction waveform signal Aai to the current command signal AS to generate a correction current command signal ASc.
[0025]
The amplitude control means 18 includes a multiplier 30 that multiplies the corrected current command signal ASc by the power command signal 10 to generate a reference current signal SS.
[0026]
The voltage feedforward signal adding means 19 creates a inverter 36 by adding the voltage feedforward signal FF to the error amplification signal Iea and a divider 36 for dividing the voltage signal Vs of the system commercial power supply by the DC voltage signal 35. And an adder 3.
[0027]
Hereinafter, a method of controlling the output current waveform of the inverter by the inverter device will be described. The voltage signal Vs of the commercial power supply detected by the voltage transformer 12 is input to the synchronization signal detection circuit 22, where the synchronization is detected. The synchronization detection signal Sy output from the synchronization signal detection circuit 22 is input to the unit sine wave signal circuit 24. The unit sine wave signal generation circuit 24 generates a current command signal AS composed of a unit sine wave signal based on the input synchronization detection signal Sy, and outputs the current command signal AS to the subtractor 32 of the current command signal correction means 17.
[0028]
On the other hand, the output current Is of the DC / AC inverter 1 detected by the current detector 11 is input to the normalization circuit 33. The normalization circuit 33 normalizes the output current Is of the inverter with the maximum amplitude value of the input current command signal AS, thereby generating a normalized output current signal Isn and outputting it to the subtractor 32. The subtractor 32 generates a normalized error signal Aa by subtracting the normalized output current signal Isn from the current command signal AS, and outputs the normalized error signal Aa to the error waveform integration circuit 34. The error waveform integration circuit 34 integrates the input normalized error signal Aa with a length corresponding to the cycle of the synchronization detection signal Sy detected by the synchronization signal detection circuit 22 to create a current command correction waveform signal Aai and add it. 31. At this time, the integration start phase of the normalized error signal Aa at the time of waveform integration and the output start phase of the current command correction waveform signal Aai are synchronized by the synchronization detection signal Sy.
[0029]
The adder 31 adds the input current command correction waveform signal Aai and the current command signal AS, and outputs a correction current command signal ASc as a result of the addition to the multiplier 30 of the amplitude control means 18.
[0030]
The multiplier 30 multiplies the input correction current command signal ASc by the power command signal 10 to create a reference current signal SS, and outputs the reference current signal SS to the subtractor 5. The subtracter 5 subtracts the inverter output current Is (detected by the current detector 11) from the input reference current signal SS to generate a current error signal Ie and outputs the current error signal Ie to the gain 4. At a gain of 4, the input current error signal Ie is amplified to generate an error amplified signal Iea, which is output to the voltage feedforward signal addition circuit 19. The voltage feedforward signal adding circuit 19 divides the voltage signal Vs (detected by the voltage transformer 12) of the commercial power supply by the DC voltage signal 35 in the divider 36 to obtain the voltage feedforward signal (voltage compensation amount) FF. It is created and input to the adder 3. The adder 3 generates the inverter drive signal ID by adding the voltage feedforward signal FF to the error amplification signal Iea input from the gain 4, and outputs the inverter drive signal ID to the PWM inverter drive signal circuit 2. The PWM inverter drive signal circuit 2 drives the DC / AC inverter 1 based on the input inverter drive signal ID.
[0031]
In the inverter device according to the present embodiment configured as described above, since control is performed so as to perform compensation based on the waveform fluctuation of the system voltage, there is a case where the system voltage has a steady distortion or a non-linearity caused by the inverter main circuit. (For example, when the ON time of the switching element is not proportional to the output), harmonic distortion may occur. However, in the inverter device of the present embodiment, by providing the current command signal correcting means 17, the current command signal AS is compensated so as to cancel the steady component of the harmonic distortion generated in the inverter output current Is. Therefore, harmonic distortion does not occur and an output current with low distortion can be obtained.
[0032]
Further, in the inverter device of the present embodiment, by providing the amplitude control means 18, the amplitude of the corrected current command signal ASc corrected according to the current command correction waveform signal Aai is changed based on the power command signal 10. Thus, it becomes possible to instantaneously change the waveform of the correction current command signal ASc according to the change of the power command signal 10, and accordingly, the responsiveness of the inverter output can be improved.
[0033]
Further, in the inverter device of the present embodiment, the system voltage waveform is compensated by providing the voltage feedforward signal adding means 19, whereby the response to the inverter output at the time of system fluctuation is quickened, and the stable control is performed. Actions can be taken. In addition, the voltage feedforward signal adding means 19 adjusts the voltage feedforward signal FF so as to cancel the fluctuation of the DC voltage signal 35 according to the fluctuation of the DC voltage signal 35 by providing the divider 36. The stability when the DC input of the inverter is fluctuated is increased.
[0034]
Second Embodiment FIG. 2 is a block diagram of an inverter device that implements an inverter output current waveform control method according to a second embodiment of the present invention. As in the embodiment, the present invention is implemented in an inverter device in which the inverter is connected to a commercial system power supply.
[0035]
This embodiment is different from the first embodiment in the configuration of the amplitude control means 18 '. Further, the configuration of the voltage command signal correction means 17' is changed in accordance with the change in the configuration of the amplitude control means 18 '. However, this is slightly different from the first embodiment. The other configuration is the same as that of the first embodiment, and the same or similar parts are denoted by the same reference numerals and description thereof will be omitted.
[0036]
In the present embodiment, the position at which the power command signal 10 is multiplied by the amplitude control means 18 'is equivalently moved with respect to the configuration of the first embodiment. That is, this inverter device includes a first multiplier 30a and a second multiplier 30b as multipliers for multiplying the power command signal 10. The first multiplier 30a multiplies the current command correction waveform signal Aai output from the error waveform integration circuit 34 by the power command signal 10, and outputs the multiplication result Aai 'to the adder 31'. The second multiplier 30b multiplies the current command signal AS output from the current command signal generating means 16 by the power command signal 10, and outputs the multiplication result AS 'to the adder 31'. The adder 31 'adds the input multiplication result Aai' of the first multiplier 30a and the second multiplication result AS 'to generate the reference current signal SS.
[0037]
In the present embodiment, by configuring the first and second multipliers 30a and 30b in this way, the amplitude control means 18 'is configured to be equivalent to the amplitude control means 18 of the first embodiment. And the operation and effect are exactly the same.
[0038]
Third Embodiment FIG. 3 is a block diagram of an inverter device that implements an inverter output current waveform control method according to a third embodiment of the present invention. As in the embodiment, the present invention is implemented in an inverter device in which the inverter is connected to a commercial system power supply.
[0039]
This embodiment is obtained by removing the voltage feedforward signal adding means 19 for compensating for the system voltage from the configuration of the first embodiment, and the other configuration is the same as that of the first embodiment. . Therefore, in FIG. 3, the same or similar portions as in FIG. 1 are denoted by the same reference numerals as in FIG. 1, and the description thereof will be omitted.
[0040]
In the configuration of the present embodiment, the response during system oscillation is inferior to those of the first and second embodiments, but the output current waveform is the same as that of the first and second embodiments. It is possible to obtain a low distortion current output by canceling the components.
[0041]
It is needless to say that the implementation of the inverter devices according to the first to third embodiments can be implemented using dedicated hardware, or can be implemented using software such as a microcomputer or a DSP.
[0042]
【The invention's effect】
As described above, according to the present invention, even when a steady harmonic distortion component exists in the inverter output current, a current command correction waveform is formed so as to cancel the steady distortion, and then the current command correction waveform is formed. Since the current command signal is corrected according to the waveform, an output current with low distortion can be obtained. Moreover, if the amplitude of the current command correction waveform is changed together with the current command signal based on the output power command, the current command correction waveform can also instantaneously change with respect to the change of the output power command. The responsiveness of the inverter output can be improved.
[0043]
Further, when calculating the error waveform between the inverter output current waveform and the current reference waveform, if the output current waveform is normalized by the amplitude of the current command waveform, the fundamental frequency component included in the current command correction waveform can be calculated. As much as possible, only harmonic distortion components to be canceled can be included, and a decrease in the response speed of the fundamental component to the output power command can be prevented.
[0044]
Also, by detecting a system voltage waveform and adding a voltage feedforward signal proportional to the voltage waveform to the inverter drive signal, even when a system voltage change occurs, the change is instantaneously reflected in the inverter drive signal. Therefore, the response of the inverter output can be further increased, thereby increasing the stability at the time of system fluctuation. Further, if the voltage feedforward signal is changed so as to cancel the fluctuation of the DC input voltage of the inverter, even if the DC input voltage of the inverter fluctuates, the fluctuation is canceled in the inverter drive signal, and Can be further improved in the case where the DC input fluctuates.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an inverter device according to a first embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of an inverter device according to a second embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration of an inverter device according to a third embodiment of the present invention.
FIG. 4 is a block diagram showing a configuration of a conventional inverter device.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 DC / AC converter 2 PWM inverter drive signal circuit 3 Adder 4 Gain 5 Subtractor 6 Current command signal circuit 10 Power command signal 11 Current detector 12 Voltage transformer 14 Reactor 15 Capacitor F AC filter 16 Current command signal generating means 17 Current command signal correction means 18 Amplitude control means 19 Voltage feedforward signal addition means 21 Averaging circuit 22 Synchronous signal detection circuit 23 Multiplier 24 Unit sine wave signal circuit 25 Multiplier 30 Multiplier 30a First multiplier 30b Second Multiplier 31 Adder 32 Subtractor 33 Normalization circuit 34 Error waveform integration circuit 35 DC voltage signal 36 Divider AS Current command signal ASc Correction current command signal SS Reference current signal Is Inverter output current Isn Normalized output current signal Aa Normalized error signal Ie Current error signal Iea Differential amplification signal FF voltage feedforward signal Vs voltage signal Sy synchronization detection signal Aa normalization error signal Aai current command correction waveform signal ID inverter driving signal

Claims (7)

An output current waveform control method for an inverter having a current feedback to amplify a deviation between a current command signal created according to an inverter output current and the inverter output current and to provide an inverter drive signal,
An error waveform between the waveform of the inverter output current and the waveform of the current command signal is integrated at a synchronized predetermined cycle to create a current command correction waveform, and the current command signal is corrected according to the current command correction waveform. A method for controlling an output current waveform of an inverter. The method for controlling an output current waveform of an inverter according to claim 1, wherein
An inverter output current waveform control method, wherein the amplitude of the current command signal corrected according to the current command correction waveform is changed based on an inverter output power command. 3. The output current waveform control method for an inverter according to claim 1 or 2,
A method for controlling an output current waveform of an inverter, comprising: normalizing an inverter output current waveform by an amplitude of a current command signal before integrating an error waveform between the inverter output current waveform and the current command signal waveform. . The method for controlling an output current waveform of an inverter according to claim 1, wherein
As the current command signal, a sine wave signal having a fixed amplitude synchronized with the inverter output voltage is used, and the inverter output current is normalized by the amplitude of the sine wave signal. An output current waveform control method for an inverter, wherein the current command signal is corrected by a current command correction waveform created by integrating an error waveform, and the amplitude of the corrected current command signal is changed based on the inverter output power command. . 5. The method for controlling an output current waveform of an inverter according to claim 1, wherein
A method of controlling an output current waveform of an inverter, comprising detecting a system voltage waveform and adding a voltage feedforward signal proportional to the detected system voltage waveform to the inverter drive signal. The output current waveform control method for an inverter according to claim 5,
A method of controlling an output current waveform of an inverter, wherein the voltage feedforward signal is changed so as to cancel a fluctuation of a DC input voltage of the inverter. An inverter device having current feedback that amplifies a deviation between a current command signal created in accordance with an inverter output current and the inverter output current and sets the deviation as an inverter drive signal,
As the current command signal, a current command signal generating means for creating a current command signal consisting of a sine wave signal having a fixed amplitude synchronized with the inverter output voltage,
Current command signal correction means for correcting the current command signal according to a current command correction waveform created by integrating an error waveform between the inverter output current and the current command signal at a synchronized predetermined cycle; An amplitude control means for changing the amplitude of the signal based on the inverter output power command.

Images