KR20110053795A - Capacitance estimation system of dc link capacitor for single phase pulse width modulation converter - Google Patents

Abstract

PURPOSE: A capacitance estimation system of a dc link capacitor for single phase pulse width modulation(PWM) converter is provided to improve productivity by determining the replacement time of a capacitor in advance by estimating a capacitance state in on-line. CONSTITUTION: An inductor(L) is connected to the backend of an input power source(es). A PWM converter converts AC voltage outputted from the input power source into DC voltage. The capacitor(C) is connected to the backend of the PWM converter and smooths the DC voltage. A voltage controller produces a second current command using the difference of the voltage of capacitor and a first voltage command. The current controller outputs the voltage command from the error current value.

Description

CAPACITANCE ESTIMATION SYSTEM OF DC LINK CAPACITOR FOR SINGLE PHASE pulse width modulation CONVERTER}

The present invention relates to a system for estimating a DC link capacitor capacity of a single phase PWM converter, and more particularly, to a system for estimating the capacity of a DC link capacitor connected to a single phase PWM converter by injecting current or voltage of an AC component.

Recently, single-phase pulse width modulation (PWM) converters are widely used in renewable energy change systems such as photovoltaic, fuel cells, active filters, and uninterruptible power supplies (UPS). have.

The electrolytic capacitor is an energy buffer and is mainly connected to the rear stage of the single-phase PWM converter. The electrolytic capacitor may lose the initial characteristics of the capacitor due to temperature, humidity, and other factors, and the capacitor capacity also decreases over time. . Therefore, it is important to know what percentage of capacitor capacity has been reduced and when to replace a new capacitor, but it is difficult to measure capacitor capacity directly from a capacitor located inside a single-phase PWM converter.

To overcome this problem, for example, methods for measuring capacitor capacity based on an increase in the value of the equivalent series resistance of the capacitor have been proposed.

However, the lifespan of the power semiconductor element and the sensor part used in the power converter is semi-permanent, whereas the electrolytic capacitor has a short lifespan and a high failure rate due to deterioration due to electrolyte evaporation. Even with the same capacitor, electrolyte consumption varies depending on operating temperature and frequency, so it is difficult to predict the capacity reduction rate of the capacitor.In most power conversion systems, since the capacitor is installed inside the power conversion unit, it is inconvenient to separate it from the system for measurement. Follow.

Accordingly, the present invention provides a system for estimating the capacity of a DC link capacitor connected to a single phase PWM converter in software without additional hardware.

In accordance with an aspect of the present invention, a capacitor capacity estimation system of a single phase PWM converter includes an inductor connected to a rear end of an input power supply and an alternating current voltage connected to a rear end of the inductor and output from the input power supply. A PWM converter for converting the voltage into a voltage converter; a capacitor connected to a rear end of the PWM converter to smooth the DC voltage; a voltage controller configured to generate a second current command by using a difference between the voltage of the capacitor and the first voltage command value; A calculation unit configured to generate a final current command through a phase value of the input power source, a magnitude of the second current command, and an injection current, and calculate an error current value from a difference between the final current command and an output current of the input power source; A current controller for generating and outputting a voltage command from the error current value, the voltage command Using the pulse control unit for controlling the pulse of the PWM converter, and comprises estimating unit for estimating the capacity of the capacitor by using the voltage of the DC link current output from the PWM converter and the capacitor.

The operation unit may multiply the phase value of the input power by the magnitude of the second current command, add the injection current to generate the final current command, and the injection current may have an AC component.

The current controller may generate the voltage command from the error current value by using a transfer function as follows.

Here, K _P and K _I are gain values, where K _P and K _I are gain values, s is a Laplace component of an error current value, and ω is a frequency component of a physical quantity to be controlled.

The estimator may estimate the capacitance of the capacitor such that the error cost function is minimized using a recursive least square algorithm.

는 상기 커패시터의 추정 용량이다. Where e ² (n) is the error cost function, BPF [·] is the output value passed through the band pass filter, i _dc is the DC link current output from the PWM converter, v _dc is the voltage of the capacitor ,

Is an estimated capacitance of the capacitor.

The estimated capacity of the capacitor can be updated through the following equation.

Where μ (n) is the gain correction value.

According to another embodiment of the present invention, a capacitor capacity estimation system of a single phase PWM converter includes: an inductor connected to a rear end of an input power source, a PWM converter connected to a rear end of the inductor and converting an AC voltage output from the input power source into a DC voltage; A capacitor connected to a rear end of the PWM converter to smooth the DC voltage, a first voltage command and an injection voltage are generated to generate a second voltage command, and an error voltage value from a difference between the voltage of the second voltage command and the capacitor; A first calculating unit for calculating a value, a voltage control unit generating an initial current command from the error voltage value, generating a final current command through a magnitude of the initial current command and a phase value of the input power source passed through a phase synchronization circuit, A second calculating unit which generates an error current value from a difference between a current command and an output current of the input power source, A current controller for generating and outputting a final voltage command from the error current value, a pulse controller for adjusting a pulse of the PWM converter using the final voltage command, and using the output power of the PWM converter and the output power of the capacitor An estimator for estimating the capacitance of the capacitor.

The first calculator may add the first voltage command and the injection voltage to generate the second voltage command, and the injection voltage may have an AC component.

The estimator may estimate the capacitance of the capacitor such that the error cost function is minimized using a recursive least square algorithm.

는 상기 커패시터의 추정 용량이다. Where e ² (n) is the error cost function, BPF [·] is the output value passed through the band pass filter, P _cap is the difference value between the output power of the PWM converter and the output power of the capacitor, v _dc Is the voltage of the capacitor,

Is an estimated capacitance of the capacitor.

The estimated capacity of the capacitor can be updated through the following equation.

Where μ (n) is the gain correction value.

As described above, according to the present invention, the DC link capacitor capacity estimating system of the single phase PWM converter can estimate the deterioration state of the capacitor capacity on-line by simply adding software without adding additional hardware. Therefore, the replacement time can be determined in advance before the capacitor fails, and productivity can be improved. In addition, the AC signal can be accurately followed by injecting an AC component current or voltage into the single-phase PWM converter, thereby increasing the accuracy of the capacitor capacity estimation.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, this includes not only "directly connected" but also "electrically connected" with another element in between. . In addition, when a part is said to "include" a certain component, which means that it may further include other components, except to exclude other components unless otherwise stated.

In addition, the expression that voltage is maintained throughout the specification indicates that even if the potential difference between two specific points changes over time, the change is within an allowable range in the design or the cause of the change is due to parasitic components that are ignored in the design practice of those skilled in the art. Include cases by. In addition, since the threshold voltage of a semiconductor device (transistor, diode, etc.) is very low compared to the discharge voltage, the threshold voltage is regarded as 0V and approximated.

1 is a system block diagram for explaining a method of estimating the capacity of a DC link capacitor of a single-phase PWM converter according to an embodiment of the present invention.

As shown in FIG. 1, according to the system for estimating the capacitance of the DC link capacitor of the single-phase PWM coverter according to the embodiment of the present invention, the inductor L is connected to the rear end of the input power source e _s , and the inductor ( At the rear of L), a PWM converter for converting an input power source e _s into a direct current power source is connected.

The PWM converter according to the embodiment of the present invention includes four switches (A +, A-, B +, and B-), and the switch is mainly composed of an Insulated Gate Bipolar Transistor (IGBT) and has a pulse width. It can be implemented with other kinds of adjustable transistors, for example MOSFETs, BJTs and the like.

When the switches A + and B- are turned on, the alternating current i _a output from the input power source e _s is input through the inductor L, the switch A +, the capacitor C and the switch B-. power (e _s) is input, the input power (e _s) the current (i _b) that is input has a direct current form. In addition, when the switches A- and B + are turned on, the AC current output from the input power source e _s is transferred to the input power source through the switch B +, the capacitor C, the switch A-, and the inductor L. e _s ).

The DC link voltage V _dc is charged to the capacitor C connected to the rear end of the PWM converter, smoothes the DC voltage, and supplies power to the load connected to the rear end. The voltage controller outputs a current command value using the voltage V _dc of the capacitor C input thereto.

A current controller (Current controller) is a phase-locked loop (Phase-locked loop, PLL) for coarse input power (e _s) phase, the input power (e _s) the output current (i _s), the voltage through the command current value command of the The value is output, and the pulse controller adjusts the pulse width of the PWM converter using the voltage command value.

On the other hand, the DC link voltage (i _dc ) of a single phase AC / DC PWM converter has a constant DC value except for the harmonic ripple associated with the switching frequency. In order to estimate the capacitance of a capacitor connected to a PWM converter, it is difficult to extract capacitor capacity information from a signal of a constant DC value. Therefore, according to the embodiment of the present invention, by injecting an alternating current or an alternating current voltage having a sinusoidal wave shape, a ripple component corresponding to the DC link voltage is generated and the capacitor capacity is estimated using the ripple component.

Hereinafter, a method of estimating capacitor capacity by injecting a current through the first embodiment will be described.

2 is a diagram illustrating a single-phase PWM converter circuit capable of measuring capacitor capacity according to a first embodiment of the present invention.

First, the first calculator 110 obtains a difference value between the reference voltage V _dc and the voltage command V _dc ^* of the sensed capacitor C. Here, the reference voltage V _dc of the capacitor C is a mixture of an alternating current component and a direct current component, and the voltage command V _dc ^* is composed of only a direct current component.

The voltage command (V _dc ^* ) represents the voltage value to be maintained across the capacitor (C) before the current is injected. The voltage command (V _dc ^* ) can be set in consideration of the rated voltage and load characteristics on the load side.

The first operator 110 subtracts the reference voltage V _dc of the capacitor C from the voltage command V _dc ^* , and the low pass filter LPF removes noise of an output value and a band The band stop filter (BSF) removes AC components.

Accordingly, the voltage controller 120 applies the capacitor voltage of the DC component, and the voltage controller 120 outputs the magnitude component i _mag of the current command from the capacitor voltage of the DC component.

Here, the voltage control unit 120 is a value of the input terminal (difference value between the voltage command (V _dc ^* ) and the sensed capacitor voltage (V _dc )) and the gain (proportional gain and integral gain) and current command of the voltage control unit 120 Is substituted into the power balance equation to find the transfer function between the voltage command and the sensed capacitor voltage (V _dc ). The transfer function includes proportional gain and integral gain, and these gain values determine the performance of the voltage controller 120. That is, the voltage controller 120 calculates a current command that causes the value of the input terminal (a difference value between the voltage command V _dc ^* and the sensed capacitor voltage V _dc ) to converge to zero, thereby calculating the magnitude component of the current command ( i _mag ) Here, since the power balance equation and the transfer function required for calculating the current command in the voltage controller 120 can be easily changed by those skilled in the art, a detailed description thereof will be omitted.

The phase synchronization circuit PLL calculates the phase component sin θ from the input power source e _s , and the phase synchronization circuit PLL calculates the phase component sin θ from the input power source e _s . Will be described in detail with reference to FIG.

The second calculator 130 receives the magnitude component i _mag of the current command and the phase component sin θ of the input power source e _s and generates a current command of the AC component through a multiplication process. The third calculator 140 adds the current command and the injection current i ^* _inj to generate a final current command i ^* _s .

Here, the injection current (i ^* _inj ) will be described briefly. First, the DC link voltage of the single-phase PWM converter has a constant value except for the harmonic ripple associated with the switching frequency. Therefore, if the DC link voltage is constant, it is difficult to obtain information for estimating the capacitor capacity from the constant DC voltage, so that the current i ^* _inj is injected as a specific signal to excite the system.

Therefore, according to the first embodiment of the present invention, a low frequency alternating current component is injected into the single phase PWM converter, and this signal is used for estimating capacitor capacity. The injection current (i ^* _inj ) having a low frequency alternating current component may be expressed by Equation 1 below.

The injection current i ^* _inj generates a ripple component in the DC link voltage at the same frequency, and in the DC link capacitor, the AC current and the voltage component are used to measure the capacitor capacity.

The fourth calculator 150 receives the final current command i ^* _s from the third calculator 140 and simultaneously receives the sensing current i _s of the input power source e _s . The fourth calculator 150 outputs an error value i _err by subtracting the final current command i ^* _s from the sensing current i _s of the input power source e _s .

The current controller 160 generates the final voltage command V ^* _ref using the error value i _err , and the current controller 170 generates the final voltage command V ^* _ref . It will be described in detail with reference to Figure 4 to be described later.

The pulse controller 170 adjusts the pulse width of the switch included in the single phase PWM converter in response to the final voltage command V ^* _ref .

As such, when the pulse width of the switch included in the single-phase PWM converter is adjusted in response to the final voltage command (V ^* _ref ), the RLS estimator 180 adjusts the DC link current and the capacitor output from the pulse width-controlled PWM converter. The capacity of the capacitor is estimated using the voltage V _dc .

First, a band pass filter (BPF) removes a DC link current and a voltage ripple component at an injection frequency by passing only a frequency component corresponding to an injected current, and the RLS estimator 180 outputs a PWM converter. The capacitance of the capacitor is estimated using the DC link current and the voltage of the capacitor (V _dc ). DC link current (i _dc ) must be obtained to measure capacitor capacity. It is inefficient to obtain DC link current (i _dc ) by installing an additional DC current sensor. Therefore, instead of directly measuring the direct current link current (i _dc ), it can be calculated using the gating time and the phase current, it can be expressed as Equation 2.

Here, S _a and S _b are switching functions for the switches at both ends connected to the input AC power source, and have a value of '1' or '0' depending on whether the switch is turned on or off. And i _a and i _b are currents flowing through both ends of the single-phase PWM converter, respectively, i _a = -i _b = i _s is satisfied.

Instead, using the output current (i _s ) and the gating time of the input AC power source, the average value of the DC link current (i _{dc , cal} ) can be obtained as shown in Equation 3 below.

T _a and T _b are the gating time for the switch turned on in a single-phase PWM converter, and T _sampling represents the sampling time.

3A and 3B are diagrams for describing a gating time and a sampling time.

Sampling time (T _sampling ) is a time period in which all sensors sense the measured value. For example, if the sampling time is one second, the sampling time T _sampling indicates that the measured value is sensed again after one second. The sampling time also corresponds to the PWM period of a single-phase PWM converter. For example, in FIG. 1, when the A + switch is turned on, the A- switch is turned off, and the relationship between the B + switch and the B- switch is also the same. Gating time is the time that indicates how long the PWM converter should turn on the A + and B- switches, or the A- and B + switches for one sampling time (i.e., PWM period). 3A and 3B, V ^* _ref represents a final voltage command generated by the current controller 160.

Hereinafter, the method of estimating the capacitance of the capacitor by the RLS estimator 180 will be described in more detail. First, the relationship between the current and the capacitor voltage can be expressed as shown in Equation 4.

Assuming no load, Equation 4 is applied to the capacitor according to the embodiment of the present invention.

Where i _dc is the DC link current output from the single-phase PWM converter and v _dc is the capacitor voltage. In addition, i _{dc and cal} obtained from Equation 3 to i _dc of Equation 5 Assign a value.

A band pass filter (BPF) is used to extract a DC link current and a voltage ripple component at an injection frequency, and can be expressed by Equation 6.

Here, BPF [·] represents the output value which passed the band pass filter BPF.

The RLS estimator 180 minimizes the least square cost function through a recursive least square algorithm. The error cost function can be expressed as Equation 7 below.

는 상기 커패시터의 추정 용량이다. Where e ² (n) is the error cost function, BPF [·] is the output value passed through the band pass filter, i _dc is the DC link current output from the PWM converter, v _dc is the voltage of the capacitor ,

Is an estimated capacitance of the capacitor.

는 오차 비용 함수 e²(n)를 최소화하기 위하여 갱신되도록 한다. 따라서, 계수

는 다음의 수학식 8과 같이 나타낼 수 있다.Where capacitor estimated capacitance

Is updated to minimize the error cost function e ² (n). Thus, the coefficient

Can be expressed as Equation 8 below.

Here, μ (n) is a gain correction value and can be selected as a constant (0.1 * 10 ⁻⁸ ).

4 is a block diagram illustrating a phase synchronization circuit PLL according to an embodiment of the present invention.

The phase synchronization circuit PLL shown in FIG. 4 follows the three-phase pq theorem, and the measured voltage e _{s as the} input signal is set to V _α in the α-β coordinate system. The vertical component of V _β can be obtained by delaying V _α by π / 2 from a two phase generator. The virtual currents i _α and i _β are orthogonal to the voltages V _α and V _β .

The PI current controller is a controller for improving the steady state error and the response speed, and can accurately estimate the angle when the steady state is reached. The PI controller shows excellent performance in DC component control, but the system cannot estimate the command value completely even after long time if the controller gain is not high when the current command is AC.

In Figure 4, ω _ff represents the feed-forward frequency for the source voltage. In this case, the all-pass filter is used by the two-phase signal generator to delay the measured voltage e _s by 90 degrees, and the transfer function is expressed by Equation 9 below.

Here, ζ is set to 1 as the damping ratio, and ω _n is the frequency with respect to the input power supply.

5 is a block diagram illustrating a current controller according to an embodiment of the present invention.

First, the fourth operator 150 receives a final current command i ^* _s corresponding to the reference current from the third operator 140 and inputs the measured source current i _s of the input AC power supply e _s . Receives the error value (i _err ) corresponding to the difference value. In order to synchronize the final current command (i ^* _s ) corresponding to the reference current, the phase of the reference current is determined from the source voltage measured by the PLL. The transfer function of the current controller 160 shown in FIG. 4 may be expressed by Equation 10 below.

Here, it is preferable to set the gain value K _P to 29 and the gain value K _I to 100, where K _P and K _I are gain values, s is a Laplace component of an error current value, and ω is to be controlled. It is the frequency component of the physical quantity.

Therefore, as shown in FIG. 4, the current controller 160 outputs the final voltage command V ^* _ref using Equation 10. FIG.

Hereinafter, a method of estimating capacitor capacity by injecting a voltage through the second embodiment will be described. 6 is a diagram illustrating a single-phase PWM converter circuit capable of measuring capacitor capacity according to a second embodiment of the present invention.

As in the first embodiment, since the DC link voltage of the single-phase PWM converter has a constant value except for the harmonic ripple associated with the switching frequency, if the DC link voltage is constant, information for estimating capacitor capacity from the constant DC voltage is obtained. Since this is difficult, it is possible to inject a voltage V ^* _inj as a specific signal to excite the system.

First, an initial voltage command V ^* _dc0 and an injection voltage V ^* _inj are input to the first calculator 610. Here, the initial voltage command (V ^* _dc0 ) is a DC voltage, the injection voltage (V ^* _inj ) is an AC voltage, it can be expressed by the following equation (11).

The first calculator 610 calculates an initial voltage command V ^* _dc0 and an injection voltage V ^* _inj , and outputs a final voltage command V ^* _{dc as} shown in Equation 12.

Here, the initial voltage command (V ^* _dc0 ) is a reference voltage of the DC link voltage in the initial normal state. Therefore, the injection voltage V ^* _inj having the AC component is injected into the DC link voltage and calculated as the final voltage command V ^* _dc .

The second operator 620 receives the final voltage command V ^* _dc from the first operator 610, receives the reference voltage V _dc of the capacitor C, and receives the voltage command V ^* through an operation process. _dc ) outputs an error value obtained by subtracting the reference voltage V _dc of the capacitor C.

As in the first embodiment, noise is removed using a low pass filter (LPF), and other AC high frequency components except frequencies injected through a band stop filter (BSF) are removed. .

The capacitor voltage of the DC component is applied to the voltage controller 630, and the voltage controller 630 outputs the current command i ^* _{L_ fb} from the capacitor voltage of the DC component.

As in the first embodiment, the voltage controller 630 calculates a current command that causes the value of the input terminal (a difference value between the voltage command V _dc ^* and the sensed capacitor voltage V _dc ) to converge to 0, thereby providing a current command. Output the size component of i ^* _{L_ fb} .

A third computing unit (640) is the current command from the voltage control section (630) (i ^* _{L_ fb)} input receives a feed forward compensation component (i ^* _{L_ ff)} the input received magnitude component of the final current command to add operations (i ^* _L ) is printed.

The fourth operator 650 receives the magnitude component i ^* _L of the final current command from the third operator 640 and receives the phase component sin θ from the input AC power supply e from the phase synchronization circuit PLL. It receives the input and outputs the final current command (i ^* ) through the calculation process.

The fifth operator 660 subtracts the final current command i ^* from the current i _s of the input AC power supply e _s and outputs an error value i _err .

The current controller 670 generates a final voltage command V ^* _ref using the error value, and the pulse controller 680 is included in the single phase PWM converter in response to the final voltage command V ^* _ref . The pulse width of the configured switch.

As such, when the pulse width of the switch included in the single-phase PWM converter is adjusted in response to the final voltage command V ^* _ref , the RLS estimator 700 outputs the power output from the PWM converter with the adjusted pulse width and the output power of the capacitor. Estimate the capacitance of the capacitor using.

When the output power P _in of the PWM converter and the output power P _out of the capacitor are respectively applied to the sixth calculator 690, the sixth operator 690 may output the output power P _in of the PWM converter and the capacitor. Find the difference in output power (P _out ).

The DC link power P _cap corresponding to the difference between the output power P _in of the PWM converter and the output power P _out of the capacitor can be expressed by Equation 13 below.

Where P _in is the output power of the PWM converter, P _out is the power consumed by the load, V _dc is the DC link voltage, and C is the DC link capacitor capacity. And, as shown in FIG. 6, if there is no load, P _in is the output power of the PWM converter and the input power of the capacitor.

The DC link power P _cap may be represented by Equation 14 below.

If the device loss is ignored in Equation 14, the input power P _in of the PWM converter may be expressed as Equation 15 below.

Here, E represents the magnitude (magnitude) of the source voltage, I ^* _L is a reference value of the output current of the PWM converter, can be expressed as shown in Equation 16.

Here, the current command (i ^* _{L_ fb} ) is the output voltage of the voltage controller 630, the feed forward compensation component (i ^* _{L_ ff} ) can be expressed by the following equation (17).

Here, Substituting Equation 11 in Equation 17, the feed-forward compensation component (i ^* _{L_ ff)} can be expressed as: Equation (18) of.

If a band pass filter (BPF) is applied to both ends of Equation 14 representing the relationship between the power and the capacitor voltage, it can be expressed as Equation 19 below.

Here, BPF [·] represents the output value which passed the band pass filter BPF.

The RLS estimator 700 minimizes the least square cost function through a recursive least square algorithm. The error cost function can be expressed as Equation 20 below.

는 상기 커패시터의 추정 용량이다. Where e ² (n) is the error cost function, BPF [·] is the output value passed through the band pass filter, P _cap is the difference value between the output power of the PWM converter and the output power of the capacitor, v _dc Is the voltage of the capacitor,

Is an estimated capacitance of the capacitor.

는 오차 비용 함수 e²(n)를 최소화하기 위하여 갱신되도록 한다. 따라서, 계수

는 다음의 수학식 21과 같이 나타낼 수 있다.Where capacitor estimated capacitance

Is updated to minimize the error cost function e ² (n). Thus, the coefficient

Can be expressed as Equation 21 below.

Here, μ (n) is a gain correction value and can be selected as a constant (0.1 * 10 ⁻⁸ ).

Meanwhile, the current controller, the phase synchronization circuit PLL, the voltage controller, the pulse controller, the various calculators, the RLS estimator, the filters LPF, BSF, BPF, and the like described in the embodiments of the present invention can be implemented in software. In particular, the RLS estimator can accurately estimate the capacity of the DC link capacitor using the RLS algorithm.

As described above, according to the exemplary embodiment of the present invention, the DC link capacitor capacity estimation system of the single phase PWM converter can estimate the deterioration state of the capacitor on-line by simply adding software without adding additional hardware. Therefore, the replacement time can be determined in advance before the capacitor fails, and productivity can be improved. In addition, the AC signal can be accurately followed by injecting an AC component current or voltage into the single-phase PWM converter, thereby increasing the accuracy of the capacitor capacity estimation.

In addition, the method of estimating the DC link capacitor capacity of the single-phase PWM converter described above is implemented by code / instructions / program that can be read by a computer. For example, the method may be implemented in a general-purpose digital computer operating the code / instructions / program using a computer readable recording medium. The computer-readable recording media may include magnetic storage media (ex, ROM, floppy disk, hard disk, magnetic tape, etc.), optical reading media (ex, CD-ROM, DVD, etc.) and carrier waves (ex, transmission via the Internet). Storage media, and the like. In addition, embodiments of the present invention may be implemented as a medium (s) containing computer readable code, such that a plurality of computer systems connected via a network can be distributed and processing operations. It is obvious that the functional programs, codes and code segments realized by the method of the present invention can be easily inferred by programmers in the technical field to which the present invention belongs.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a system block diagram for explaining a method of estimating the capacity of a DC link capacitor of a single-phase PWM converter according to an embodiment of the present invention.

2 is a diagram illustrating a single-phase PWM converter circuit capable of measuring capacitor capacity according to a first embodiment of the present invention.

3A and 3B are diagrams for describing a gating time and a sampling time.

4 is a block diagram illustrating a phase synchronization circuit PLL according to an embodiment of the present invention.

5 is a block diagram illustrating a current controller according to an embodiment of the present invention.

6 is a diagram illustrating a single-phase PWM converter circuit capable of measuring capacitor capacity according to a second embodiment of the present invention.

Claims (10)

An inductor connected to the rear end of the input power supply, A PWM converter connected to a rear end of the inductor and converting an AC voltage output from the input power source into a DC voltage; A capacitor connected to a rear end of the PWM converter to smooth the DC voltage; A voltage controller configured to generate a second current command using a difference between the voltage of the capacitor and the first voltage command value; A final current command is generated through the phase value of the input power source, the magnitude of the second current command, and the injection current through the phase synchronization circuit, and an error current value is calculated from the difference between the final current command and the output current of the input power source. Computation unit to do, A current controller for generating and outputting a voltage command from the error current value; A pulse controller for adjusting a pulse of the PWM converter using the voltage command, and And an estimator for estimating the capacitance of the capacitor by using the DC link current output from the PWM converter and the voltage of the capacitor. The method of claim 1, The calculation unit, And multiplying a phase value of the input power by a magnitude of the second current command, adding the injection current to generate the final current command, wherein the injection current has an alternating current component. The method of claim 2, The current control unit, Capacitor capacity estimation system of a single phase PWM converter generating the voltage command from the error current value using the transfer function as follows:

Here, K _P and K _I are gain values, s is a Laplace component of the error current value, and ω is a frequency component of the physical quantity to be controlled. The method of claim 3, The estimating unit, A capacitor capacity estimation system of a single phase PWM converter for estimating the capacitance of the capacitor to minimize the error cost function using a recursive least square algorithm:

Where e ² (n) is the error cost function, BPF [·] is the output value passed through the band pass filter, i _dc is the DC link current output from the PWM converter, v _dc is the voltage of the capacitor ,

Is an estimated capacitance of the capacitor. The method of claim 4, wherein Capacitor capacity estimation system of the single-phase PWM converter is updated through the following equation:

Where μ (n) is the gain correction value. An inductor connected to the rear end of the input power supply, A PWM converter connected to a rear end of the inductor and converting an AC voltage output from the input power source into a DC voltage; A capacitor connected to a rear end of the PWM converter to smooth the DC voltage; A first calculator configured to generate a second voltage command by calculating a first voltage command and an injection voltage, and calculate an error voltage value from a difference between the second voltage command and the voltage of the capacitor; A voltage controller configured to generate an initial current command from the error voltage value; A second calculator configured to generate a final current command through a magnitude of the initial current command and a phase value of the input power source that has passed through a phase synchronization circuit, and generate an error current value from a difference between the final current command and an output current of the input power source; , A current controller configured to generate and output a final voltage command from the error current value; A pulse controller for adjusting a pulse of the PWM converter using the final voltage command; And an estimator for estimating the capacitance of the capacitor using the output power of the PWM converter and the output power of the capacitor. The method of claim 6, The first operation unit, And adding the first voltage command and the injection voltage to generate the second voltage command, wherein the injection voltage has an alternating current component. The method of claim 7, wherein The current control unit, Capacitor capacity estimation system of a single phase PWM converter generating the final voltage command from the error current value using the transfer function as follows:

Here, K _P and K _I are gain values, s is a Laplace component of the error current value, and ω is a frequency component of the physical quantity to be controlled. The method of claim 8, The estimating unit, A capacitor capacity estimation system of a single phase PWM converter for estimating the capacitance of the capacitor to minimize the error cost function using a recursive least square algorithm:

Where e ² (n) is the error cost function, BPF [·] is the output value passed through the band pass filter, P _cap is the difference value between the output power of the PWM converter and the output power of the capacitor, v _dc Is the voltage of the capacitor,

Is the estimated capacity of the capacitor. 10. The method of claim 9, Capacitor capacity estimation system of the single-phase PWM converter is updated through the following equation:

Where μ (n) is the gain correction value.

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