CN100353637C - Active Harmonic Suppression Device - Google Patents

Abstract

An active harmonic suppression device comprises an energy storage direct current capacitor, an electric energy converter, a filter inductor, a passive compensation capacitor, a filter capacitor resistor group and a control circuit. The energy storage direct current capacitor is used as an electric energy storage element of the device and provides a first voltage. The electric energy converter is used for switching and outputting the first voltage to provide a compensation voltage. The filter inductor, the reactive compensation capacitor and the filter capacitor resistor group convert the compensation voltage into a compensation current, so that the power current approaches to a sine wave. The control circuit captures signals such as load current, power supply current, output current of the electric energy converter, power supply voltage, voltage of the energy storage direct current capacitor and the like to calculate expected output voltage of the electric energy converter, and generates switching signals of a power switch group in the electric energy converter after pulse width modulation; furthermore, the active harmonic suppression device may be controlled to provide fixed or variable output reactive power.

Description

Active Harmonic Suppression Device

technical field

The present invention relates to an active harmonic suppression device, in particular to a device connected in parallel with a non-linear load to filter out the harmonic current generated by it.

Background technique

In recent years, due to the rapid development of semiconductor technology, many power electronic components with good controllability and high voltage and high current resistance have been developed. These components have been widely used in power equipment, such as motors, drives, electric arc furnaces, trams , chargers and lighting fixtures, etc. Due to the non-linear input characteristics of these devices, they will generate a large number of harmonic currents. The existence of harmonic currents will cause some problems, such as overheating of transformers, disturbance of rotating machinery, distortion of supply voltage, damage of electrical components and functional failure of medical equipment, etc. In order to effectively limit the problem of harmonic pollution, some international research institutions have formulated harmonic control standards, such as IEEE519-1992, IEC1000-3-2 and IEC1000-3-4. Taipower Corporation in Taiwan also formulated the "Interim Standards for Harmonic Control of Power System" to control harmonics.

The traditional solution to harmonic problems is the passive power filter, which is composed of passive components, inductors and capacitors. However, there is a potential resonance crisis in passive power filters, which will lead to larger harmonic currents and harmonic voltages, which may damage the filter itself and adjacent power equipment, and the filtering characteristics are greatly affected by the system reactance, so It is difficult to get a good filtering effect, what's more, after installing a passive power filter, it may attract the harmonic current generated by the adjacent nonlinear load, which will cause the passive power filter to overload.

In recent years, a technology that uses a power converter composed of power electronic components to achieve a harmonic filtering function is called an active power filter, such as US patents US6472775 and US6320392. The structure of the active power filter is shown in Figure 1. It includes an energy storage DC capacitor, an electric energy converter and a filter component. The current control mode is used to control the power converter to switch the voltage on the energy storage DC capacitor through the filter component. A compensating current is generated and injected into the power feeder, and the filtering component can be an inductor or a combination of an inductor and a capacitor to filter the high-frequency ripple current caused by switching of the power switching component. In order to effectively filter high-frequency switching currents, the filter components must be selected in accordance with the limitations of switching frequency, DC voltage, and ripple current. Although the active power filter has good filtering characteristics, the power converter capacity of the active power filter must not be less than the product of the load harmonic current and the power supply voltage, so the power converter of the active power filter The capacity is very large, and its practicability is limited due to its high price, and these active power filters are only used to filter switching ripples, so their impedance is not large, so the voltage of the energy storage DC capacitor must be higher than The peak value of the power supply voltage, the higher voltage of the energy storage DC capacitor will cause a larger switching ripple, so the filter component must use a low-pass filter with a lower cut-off frequency to filter out the larger switching ripple, it will This leads to poor high-frequency response, larger volume, and higher electromagnetic interference problems.

In view of this, in order to solve the overload problem caused by the resonance of the passive power filter and the adjacent harmonic current injection, and the expensive problem caused by the large capacity of the power converter of the active power filter, there is a combination of passive components and power The power filter of the converter is developed, and the passive component is used to reduce the capacity of the power converter, such as US Pat. Passive power filters use a larger inductor and are therefore bulky and have higher losses. The passive components of US6,717,465 and US5,614,770 use a capacitor, so the volume and loss can be reduced. The power converter of US5,614,770 adopts a current control type, and the compensation current is calculated from the load current and converted with the feedback power. The closed-loop control is performed on the output current of the converter, so that the power converter operates as a current generator to generate compensation current and inject it into the power feeder to filter out the load harmonic current. However, since the current-controlled power converter is limited by the bandwidth and gain of the controller, there will be a certain error between the output current of the power converter and the calculated compensation current; in addition, it does not simultaneously detect the power supply current for feedback , resulting in partial distortion of the power supply current after compensation; while US6,717,465 adopts a voltage control type, which makes the power converter operate as a voltage source, and feeds back the power supply current to reduce the distortion of the power supply current, which improves the undetected power supply of US5,614,770 Problems caused by current feedback. However, because US6,717,465 must estimate the value of the passive components connected in series to the power converter, it is difficult to manufacture, and because the value of the passive components may be offset due to factors such as temperature and aging, resulting in the filtering performance decline.

In view of this, the present invention still proposes a shortcoming that the voltage control method adopted in US6,717,465 must estimate the value of the passive components connected in series to the power converter, so that the controller of the voltage control method is easier to manufacture, and Its filter characteristics are less affected by the value offset of passive components. The present invention controls the harmonic components of the output current of the power converter and the harmonic components of the load current in a closed loop to improve the voltage control method adopted in US6,717,465. The voltage controller is sensitive to the value of passive components connected in series with the power converter, and can simplify the control circuit, and can further choose whether to adjust the reactive current of the harmonic compensation device.

Contents of the invention

The main purpose of the present invention is to provide an active harmonic suppression device, which includes an energy storage DC capacitor, a power converter, a filter inductor, a reactive power compensation capacitor, a filter capacitor resistor group and a control circuit. The energy storage DC capacitor is used as an electric energy storage device of the device and provides a first voltage. The electric energy converter is electrically connected to the energy storage DC capacitor, and the first voltage switching output provides a compensation voltage. The filter inductor, reactive power compensation capacitor and filter capacitor resistor group convert the compensation voltage into a compensation current and inject it into the power feeder, thereby making the power supply current approach to a sine wave.

The control circuit of the device extracts the load current, power supply current, power converter output current, power supply voltage and energy storage DC capacitor voltage to calculate the expected output voltage, and the expected output voltage is generated by the pulse width modulation circuit in the power converter. The switching signal of the power switch group, thus providing a compensation voltage, and then through the filter inductor, reactive power compensation capacitor and filter capacitor resistor group, the compensation voltage is converted into a compensation current and injected into the power feeder, so that the power supply current tends to be sinusoidal wave; moreover, the active harmonic suppression device can be controlled to provide fixed or variable output reactive power.

Since the present invention has a reactive power compensation capacitor in series on the electric energy converter, the value of the first voltage provided by the energy storage DC capacitor can be reduced, so that the high-frequency ripple generated by the switching of the power switch group of the electric energy converter can be effectively reduced In addition, the control circuit of the present invention is a voltage control type, which can further reduce the high-frequency harmonic current of the power converter. Therefore, the active harmonic suppression device of the present invention can use smaller filter inductors, which can reduce the overall circuit volume, reduce weight, reduce power loss on the inductor, and reduce costs. In addition, the DC side voltage of the power converter of the present invention is lower than that of the traditional active power filter, so its current ripple is also smaller.

Description of drawings

Figure 1: Block schematic diagram of a known active power filter.

Figure 2: A schematic circuit diagram of the active harmonic suppression device of the present invention.

Fig. 3: A block diagram of the control circuit of the active harmonic suppression device according to the first preferred embodiment of the present invention.

Fig. 4: A block diagram of the control circuit of the active harmonic suppression device according to the second preferred embodiment of the present invention.

Fig. 5: A schematic block diagram of the reactive power calculation circuit of the active harmonic suppression device according to the second preferred embodiment of the present invention.

Fig. 6: A schematic block diagram of another reactive power calculation circuit of the active harmonic suppression device according to the second preferred embodiment of the present invention.

Description of figure number:

1 Harmonic suppression device 10 Power converter 11 Filter inductor

12 Reactive power compensation capacitor 13 Filter capacitor resistor group 14 Energy storage DC capacitor

15 Output current of power converter 16 Load current 17 Power supply current

18 compensation current 2 control circuit 200 harmonic detector

201 first band-stop filter 202 subtractor 203 first amplifier

204 first controller 205 second band-stop filter 206 second amplifier

207 phase shift circuit 208 low pass filter 209 subtractor

210 second controller 211 multiplier 212 adder

213 pulse width modulator 3 control circuit 300 harmonic picker

301 first band-stop filter 302 subtractor 303 first amplifier

304 first controller 305 second band-stop filter 306 second amplifier

307 Low-pass filter 308 Subtractor 309 Second controller

310 Phase Shift Circuit 311 Multiplier 312 Reactive Power Calculation Circuit

313 Limiter 314 Multiplier 315 Adder

316 pulse width modulators 41 phase shift circuits 42 multipliers

43 Low-pass filter 51 Phase detection circuit 52 Amplifier

Detailed ways

In order to make the above and other objects, features and advantages of the present invention more clearly understood, preferred embodiments of the present invention will be exemplified below and described in detail in conjunction with the accompanying drawings.

Please refer to Fig. 2, the system architecture of the active harmonic suppression device 1 of the present invention includes a power converter 10, a filter inductor 11, a reactive power compensation capacitor 12, a filter capacitor resistor group 13, an energy storage DC capacitor 14 and a control circuit 2 . The energy storage DC capacitor 14 is used as an energy storage component of the device, and provides a first voltage. The power converter 10 includes a power switch group, which is electrically connected to the energy storage DC capacitor 14, and provides the first voltage To switch to provide a compensation voltage output, the filter inductor 11, reactive power compensation capacitor 12 and filter capacitor resistor group 13 convert the compensation voltage into a compensation current 18 and inject it into the power feeder to filter out the harmonic component of the load current 16 , so that the power supply current 17 tends to a sine wave, the control circuit 2 is used to generate the drive signal of the power converter 10; the harmonic suppression device 1 can provide a fixed or adjustable of reactive power.

FIG. 3 is a control block diagram showing the control circuit 2 of the active harmonic suppression device 1 according to the first preferred embodiment of the present invention. The active harmonic suppression device 1 has the functions of harmonic filtering and providing a fixed reactive power compensation. The fixed reactive power compensation is determined by the reactive power compensation capacitor 12 and the power supply voltage. If the influence of the filter inductance is ignored, the fixed reactive power The amount of reactive power compensation can be expressed as

$\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; \&ap;</span>\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; \&omega;\; C</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Where ω is the fundamental frequency of the power supply, C is the capacitor value of the reactive power compensation capacitor 12, and V _S1 is the root mean square value of the fundamental wave of the phase voltage of the three-phase power supply.

The first preferred embodiment adopts the voltage control type, so the reference compensation voltage must be calculated. The control block of the first preferred embodiment utilizes the load current 16, the supply current 17, the power converter output current 15, the energy storage DC capacitor 14 The reference compensation voltage is calculated from the voltage and the power supply voltage, and the switching signal of the power switch group of the power converter 10 is generated through pulse width modulation, and the compensation voltage is generated.

The control block of the first preferred embodiment is mainly divided into three loops, which include a load harmonic compensation loop, a power supply harmonic suppression loop, and an energy storage DC capacitor voltage stabilization loop.

The load harmonic compensation circuit is mainly used to compensate the harmonic current generated by the load. In order to generate the harmonic component of the load current 16, US6,717,465 uses the power converter 10 to generate a harmonic voltage component equal to the harmonic component of the load current 16 and The output compensation voltage is the product of the combined impedance of the filter inductor 11 and the reactive power compensation capacitor 12 . However, US6,717,465 must estimate the value of passive components connected in series with the power converter, thus causing difficulties in manufacturing. Furthermore, since the values of the passive components may shift due to factors such as temperature and aging, the filtering performance is degraded. In order to improve this shortcoming, the present invention performs closed-loop control on the harmonic components of the output current of the power converter and the harmonic components of the load current to reduce the sensitivity of the calculation of the reference compensation voltage to the value of the passive components connected in series with the power converter . Therefore, the load harmonic compensation circuit detects the load current 16 through the harmonic detector 200 to extract the load current harmonic component, and also detects the output current 15 of the power converter through the first band-stop filter 201 to filter out the fundamental wave components to extract its harmonic components. The harmonic component of the load current and the harmonic component of the output current of the power converter are subtracted by the subtractor 202, and the result of the subtraction is amplified by the first amplifier 203. The harmonic detector 200 can be a band-stop filter to filter In addition to the fundamental wave of the load current to extract its harmonic components, a Fourier series (Fourier series) algorithm can also be used to calculate the amount of each harmonic of the load current. If the harmonic detector 200 uses a band-stop filter, its The harmonic current generated by the load will be completely compensated, and if the harmonic detector 200 adopts the Fourier series algorithm, several specific order harmonics can be selected for compensation. In order to obtain the compensation voltage, the output of the first amplifier 203 must be multiplied by the combined impedance of the filter inductor 11 and the reactive power compensation capacitor 12. Since the inductor voltage can be obtained by the differential of the current, the voltage of the capacitor can be obtained by the integral of the current , and the voltage across the stray resistors of the inductor and capacitor can be obtained by multiplying the current by a ratio. Therefore, the output of the first amplifier 203 is multiplied by the combined impedance of the filter inductor 11 and the reactive power compensation capacitor 12, and the output of the first amplifier 203 can be obtained through a PID controller. Since the impedance of the filter inductor 11 in the harmonic suppression device 1 is much smaller than the impedance value of the reactive power compensation capacitor 12 at the main harmonic frequency, the required PID controller can also be simplified into a PI controller to prevent differential The controller is disturbed by noise. Therefore, the output voltage signal of the load harmonic compensation circuit can be obtained from the output of the first amplifier 203 through the first controller 204, and the first controller 204 can be a PID controller or a PI controller.

The power supply harmonic suppression circuit is mainly used to correct the error of the compensation result of the load harmonic compensation circuit, and further suppress the harmonic component of the power supply current. In the power supply harmonic suppression circuit, after the mains power supply current 17 is detected, it is sent to the second band rejection filter 205 to filter out the fundamental wave. If the power supply current 17 still has harmonics after being compensated by the first loop, it can be picked up by the power supply harmonic suppression loop and then amplified by the second amplifier 206 as an output signal of the power supply harmonic suppression loop. Since the harmonic suppression device 1 adopts the voltage control type, the power supply harmonic suppression circuit detects the harmonic component of the power supply current and amplifies it for compensation, and its bandwidth can be much higher than that of the current control type. Therefore, the harmonic suppression of the present invention The control method of the device 1 will obtain a better compensation effect than the traditional current control method. In particular, when digital circuits are used to implement the controller, such as microcontrollers or digital signal processors.

In order to maintain the stability of the first voltage provided by the energy storage DC capacitor 14 so that the power converter 10 can operate normally, an energy storage DC capacitor voltage stabilizing circuit must be provided. The energy storage DC capacitor voltage stabilization circuit must generate a fundamental voltage signal, which is in phase with the current of the harmonic suppression device 1, so that the power converter 10 can absorb active power or release active power to maintain the energy storage DC capacitor 14. stabilization of the first voltage. Since the harmonic suppression device 1 is capacitive at the fundamental frequency, the fundamental frequency current of the harmonic suppression device 1 is 90 degrees ahead of the power supply voltage, and the energy storage DC capacitor voltage stabilizing circuit detects the first voltage of the energy storage DC capacitor 14. The voltage then passes through the low-pass filter 208 to filter out its ripple voltage, and the output of the low-pass filter 208 is sent to the subtractor 209 to subtract the set voltage and then sent to the second controller 210, while the power supply voltage is sent to a phase shifter The circuit 207 generates a 90-degree leading sine wave signal, multiplies the outputs of the second controller 210 and the phase shift circuit 207 through the multiplier 211, and serves as the output signal of the energy storage DC capacitor voltage stabilization circuit.

Finally, the output signals of the load harmonic compensation circuit, the power supply harmonic suppression circuit and the energy storage DC capacitor voltage stabilization circuit are added together by the adder 212 to obtain the reference compensation voltage signal of the power converter 10, and the reference compensation voltage signal is sent to The switching signal of the power switch group in the power converter 10 can be obtained from the pulse width modulator 213 .

FIG. 4 is a control block diagram showing the control circuit 2 of the active harmonic suppression device 1 according to the second preferred embodiment of the present invention. The active harmonic suppression device 1 has the functions of harmonic filtering and providing a variable reactive power compensation. The range of the variable reactive power compensation is between the maximum value Q _MAX and the minimum value Q _MIN . If the filter inductance is ignored The influence of Q _MAX and Q _MIN can be expressed as

${\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; MAX</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; \&omega;\; C</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Q _MIN = Q _MAX (1-V _{ai, max} /V _s1 ) (3)

Among them, ω is the frequency of the fundamental wave of the power supply, C is the capacitor value of the reactive power compensation capacitor 12, V _S1 is the root mean square value of the fundamental wave of the phase voltage of the three-phase power supply, and V _ai,max is the maximum fundamental wave that the power converter 10 can produce. The root mean square value of the wave voltage can be expressed as follows

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; ai</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Wherein V _dc is the first voltage of the energy storage DC capacitor 14 .

This second preferred embodiment adopts the voltage control formula, therefore must calculate the reference compensation voltage, the control block of this second preferred embodiment is to utilize load current 16, supply current 17, electric energy converter output current 15, energy storage DC capacitor The reference compensation voltage is calculated from the voltage of 14 and the power supply voltage, and the switching signal of the power switch group of the power converter 10 is generated through pulse width modulation, and the compensation voltage is generated.

The control circuit 3 is mainly divided into four circuits, including a load harmonic compensation circuit, a power supply harmonic suppression circuit, an energy storage DC capacitor voltage stabilization circuit and a reactive power adjustment circuit.

The load harmonic compensation circuit is mainly used to compensate the harmonic current generated by the load. In order to output the harmonic component of the load current 16, US6,717,465 uses the power converter 10 to generate a harmonic voltage component equal to the harmonic component of the load current 16 and The output compensation voltage is the product of the combined impedance of the filter inductor 11 and the reactive power compensation capacitor 12 . However, US6,717,465 must estimate the value of passive components connected in series with the power converter, thus causing difficulties in manufacturing. Furthermore, since the values of the passive components may shift due to factors such as temperature and aging, the filtering performance is degraded. In order to improve this shortcoming, the present invention performs closed-loop control on the harmonic components of the output current of the power converter and the harmonic components of the load current to reduce the sensitivity of the calculation of the reference compensation voltage to the value of the passive components connected in series with the power converter . Therefore, the load harmonic compensation circuit detects the load current 16 through a harmonic detector 300 to extract the harmonic components of the load current, and also detects the output current 15 of the power converter through the first band-stop filter 301 to filter In addition to the fundamental wave components to take out its harmonic components. The harmonic component of the load current and the harmonic component of the output current of the power converter are subtracted by the subtractor 302, and the result of the subtraction is amplified by the first amplifier 303. The harmonic detector 300 can be a band-stop filter to filter In addition to the fundamental wave of the load current to take out its harmonic components, a Fourier series algorithm can also be used to calculate the amount of each harmonic of the load current. If the harmonic detector 300 uses a band-stop filter, it will The generated harmonic current is completely compensated, and if the harmonic detector 300 adopts the Fourier series algorithm, several specific order harmonics can be selected for compensation. To obtain the compensation voltage, the output of the first amplifier 303 must be multiplied by the combined impedance of the filter inductor 11 and the reactive compensation capacitor 12 . Since the inductor voltage can be obtained by the differential of the current, the voltage of the capacitor can be obtained by the integral of the current, and the voltage of the stray resistors of the inductor and capacitor can be obtained by multiplying the current by a ratio, so the output of the first amplifier 303 is multiplied by The combined impedance of the filter inductor 11 and the reactive power compensation capacitor 12 can be obtained from the output of the first amplifier 303 through a PID controller. Since the impedance of the filter inductor 11 in the harmonic suppression device 1 is much smaller than the impedance value of the reactive power compensation capacitor 12 at the main harmonic frequency, the required PID controller can also be simplified into a PI controller to prevent differential The controller is disturbed by noise. Therefore, the output voltage signal of the load harmonic compensation loop can be obtained from the output of the first amplifier 303 through the first controller 304, and the first controller 304 can be a PID controller or a PI controller.

The power supply harmonic suppression circuit is mainly used to correct the error of the compensation result of the load harmonic compensation circuit, and further suppress the harmonic component of the power supply current. In the power supply harmonic suppression circuit, after the mains power supply current 17 is detected, it is sent to the second band rejection filter 305 to filter out the fundamental wave. If the power supply current 17 still has harmonics after being compensated by the first loop, it can be detected by the power supply harmonic suppression loop and then amplified by the second amplifier 306 as the output signal of the power supply harmonic suppression loop. The device 1 adopts the voltage control type, so the harmonic component of the power supply current detected by the power supply harmonic suppression loop is amplified for compensation, and its bandwidth can be much higher than that of the current control type. Therefore, the control method of the harmonic suppression device 1 of the present invention A better compensation effect will be obtained than the traditional current control method. In particular, when digital circuits are used to implement the controller, such as microcontrollers or digital signal processors.

In order to maintain the stability of the first voltage provided by the energy storage DC capacitor 14 so that the power converter 10 can operate normally, there is an energy storage DC capacitor voltage stabilization circuit, and the energy storage DC capacitor voltage stabilization circuit must generate a fundamental wave The voltage signal is in the same phase as the current of the harmonic suppression device 1 , so that the electric energy converter 10 can absorb active power or release active power, so as to maintain the stability of the first voltage provided by the energy storage DC capacitor 14 . Since the harmonic suppression device 1 is capacitive at the fundamental frequency, the fundamental frequency current of the harmonic suppression device 1 is 90 degrees ahead of the power supply voltage, and the energy storage DC capacitor voltage stabilizing circuit detects the first voltage of the energy storage DC capacitor 14. The voltage is filtered by a low-pass filter 307 to filter out its ripple voltage, and the output of the low-pass filter 307 is sent to the subtractor 308 to subtract the set voltage and then sent to the second controller 309, while the power supply voltage is sent to a phase shifter The circuit 310 generates a 90-degree leading sine wave signal, multiplies the outputs of the second controller 309 and the phase shift circuit 310 through the multiplier 311, and serves as the output signal of the energy storage DC capacitor voltage stabilization circuit.

The reactive power adjustment circuit is used to adjust the reactive power provided by the harmonic suppression device 1, and the reactive power provided by the harmonic suppression device 1 is

Q＝Q _MAX (1-V _a1 /V _s1 ) (5)

Among them, V _a1 is the root mean square value of the output fundamental wave voltage of the power converter 10 in phase with the fundamental wave voltage of the power supply. It can be seen from formula (5) that by adjusting the output of the power converter 10 in phase with the fundamental wave voltage of the power supply The fundamental wave voltage can change the reactive power provided by the harmonic suppression device 1, so the reactive power calculated by the reactive power calculation circuit 312 to be compensated can be obtained by the power converter 10 and the fundamental wave voltage of the power supply after passing through a limiter 313 The amplitude of the output fundamental voltage with the same phase, the output of the limiter 313 and the detected power supply voltage are sent to the multiplier 314 to obtain the output signal of the reactive power calculation circuit. The limiter 313 is mainly used to limit the range of reactive power provided by the harmonic suppression device 1 between the maximum value Q _MAX and the minimum value Q _MIN . The reactive power calculation circuit 312 will be described in detail below.

FIG. 5 and FIG. 6 are block diagrams illustrating two implementations of the reactive power calculation circuit 312 . Please refer to FIG. 5, which is the first realization block diagram of the reactive power calculation circuit. The reactive power calculation is performed by the power supply voltage through a phase shift circuit 41 to generate a 90-degree leading phase shift, and then multiplied by the load current through a multiplier 42. The output of the multiplier 42 is then passed through a low-pass filter 43 to take out the average component, which is the required compensation reactive power. Please refer to FIG. 6 which is the second implementation block diagram of the reactive power calculation circuit. The reactive power calculation is to detect the phase difference between the power supply voltage and current through a phase detection circuit 51, and then through an amplifier 52. And have to compensate reactive power.

Please refer to Figure 4 again. Finally, the output signals of the load harmonic compensation circuit, the power supply harmonic suppression circuit, the energy storage DC capacitor voltage stabilization circuit and the reactive power adjustment circuit are added by the adder 315, and then it is used as a power converter. The reference compensation voltage signal of 10 is sent to the pulse width modulator 316 to obtain the switching signal of the power switch group in the power converter 10 .

Since the present invention has a reactive power compensation capacitor 12 connected in series on the power converter 10, the value of the first voltage provided by the energy storage DC capacitor 14 can be reduced, thereby effectively reducing the switching of the power switch group of the power converter 10. In addition, the control circuit 2 of the present invention is a voltage control type, which can further reduce the high-frequency harmonic current of the power converter. Therefore, the active harmonic suppression device 1 of the present invention can use a smaller filter inductor 11, which can reduce the volume of the overall circuit, reduce the weight, reduce the power loss on the inductor, and reduce the cost. In addition, the DC side voltage of the power converter of the present invention is lower than that of the traditional active power filter, so its current ripple is also smaller.

Although the present invention has been disclosed with the aforementioned preferred embodiments, it is not intended to limit the present invention. Any skilled person can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore The protection scope of the present invention should be determined by the claims.

Claims (11)

1. An active harmonic suppression device, characterized in that it comprises: an energy storage DC capacitor for providing a stable DC voltage; A power converter, which includes a power switch group, the power converter is connected to the energy storage DC capacitor, and a compensation voltage is generated through switching of the power switch group; a filter inductor, which is electrically connected to the power converter, and the filter inductor is used to filter the switching ripple current of the power converter; A reactive power compensation capacitor, which is connected in series with the filter inductor, the reactive power compensation capacitor is used as a reactive power generation component of the active harmonic suppression device, and can reduce the DC side energy storage required by the power converter DC capacitor voltage; A filter capacitor resistor group, which is electrically connected between the series filter inductor and reactive power compensation capacitor and an AC power feeder; it is used to cooperate with the filter inductor, thereby filtering out the power generated by the power converter Harmonics; and A control circuit, which is used to generate the switching signal of the power switch of the electric energy converter, the control circuit uses the load current, the power supply current, the output current of the electric energy converter, the voltage of the energy storage DC capacitor and the power supply voltage to calculate a reference Compensation voltage, the reference compensation voltage is generated via a pulse width modulator, which is used as a control signal of the power switch group of the power converter; The control circuit adopts a voltage control type, and the control circuit includes a load harmonic compensation circuit, a power supply harmonic suppression circuit and an energy storage DC capacitor voltage stabilization circuit, which are commonly connected to an adder; The compensation voltage generated by the switching of the power converter is converted into a compensation current by the filter inductor, reactive power compensation capacitor and filter capacitor resistor group and injected into the AC power feeder to filter the harmonic current generated by the load and make the power supply The current tends to be a sine wave and provides a fixed reactive power. 2. The active harmonic suppression device according to claim 1, wherein the load harmonic compensation circuit comprises a harmonic detector, a first band-stop filter, a subtractor, a first Amplifier and a first controller, wherein the load current is detected through the harmonic detector to extract its harmonic components, and the output current of the power converter is also detected to be filtered out by the first band-stop filter The harmonic component is extracted from the wave component, the harmonic component of the load current and the harmonic component of the output current of the power converter are subtracted by the subtractor, and the result of the subtraction is amplified by the first amplifier, and the output of the first amplifier is The output voltage of the load harmonic compensation circuit can be obtained through the first controller. 3. The active harmonic suppression device according to claim 1, wherein the power supply harmonic suppression circuit includes a second band-stop filter and a second amplifier, after the power supply current is detected, It is then sent to the second band-stop filter to filter out the fundamental wave. Once the power supply current still has harmonics, it can be amplified by the second amplifier to generate an output signal. 4. The active harmonic suppression device according to claim 1, wherein the energy storage DC capacitor voltage stabilization loop comprises a phase shift circuit, a low-pass filter, a subtractor, and a second controller And a multiplier, the DC voltage of the energy storage DC capacitor is filtered by the low-pass filter to filter the ripple voltage, and the output of the low-pass filter is sent to the subtractor to be subtracted from a set voltage and then sent to the second After the controller, it is output to the multiplier, and the power supply voltage is generated by the phase shift circuit to generate a 90-degree ahead signal, and then output to the multiplier, and the output signal is obtained after being multiplied by the multiplier. 5. An active harmonic suppression device, characterized in that it comprises: an energy storage DC capacitor for providing a stable DC voltage; A power converter, which includes a power switch group, the power converter is connected to the energy storage DC capacitor, and a compensation voltage is generated through switching of the power switch group; a filter inductor, which is electrically connected to the power converter, and the filter inductor is used to filter the switching ripple current of the power converter; A reactive power compensation capacitor, which is connected in series with the filter inductor, the reactive power compensation capacitor is used as a reactive power generation component of the active harmonic suppression device, and can reduce the DC side energy storage required by the power converter DC capacitor voltage; A filter capacitor resistor group, which is electrically connected between the series filter inductor and reactive power compensation capacitor and an AC power feeder, which is used to cooperate with the filter inductor, thereby filtering the power of the power converter Harmonics generated by switching of switch blocks; and A control circuit, which is used to generate the switching signal of the power switch of the electric energy converter, the control circuit uses the load current, the power supply current, the output current of the electric energy converter, the voltage of the energy storage DC capacitor and the power supply voltage to calculate a reference Compensation voltage, the reference compensation voltage is generated via a pulse width modulator, which is used for the control signal of the power switch group of the power converter; The control circuit adopts a voltage control type, and the control circuit includes a load harmonic compensation circuit, a power supply harmonic suppression circuit, an energy storage DC capacitor voltage stabilization circuit and a reactive power adjustment circuit, which are jointly connected to an adder; The compensation voltage generated by the switching of the power converter is converted into a compensation current and injected into the AC power feeder through the filter inductor, reactive power compensation capacitor and filter capacitor resistor group, so as to filter out the harmonic current generated by the load and make the The current of the power supply tends to be a sine wave, and an adjustable reactive power is provided to improve the input power factor. 6. The active harmonic suppression device according to claim 5, wherein the load harmonic compensation loop comprises a harmonic detector, a first band-stop filter, a subtractor, a first Amplifier and a first controller, wherein the load current is detected and its harmonic components are taken out through the harmonic detector, and the output current of the power converter is also detected to be filtered out by the first band-stop filter The harmonic component is extracted from the wave component, the harmonic component of the load current and the harmonic component of the output current of the power converter are subtracted by the subtractor, and the result of the subtraction is amplified by the first amplifier, and the output of the first amplifier is The output voltage of the load harmonic compensation circuit can be obtained through the first controller. 7. The active harmonic suppression device according to claim 5, wherein the power supply harmonic suppression circuit includes a second band-stop filter and a second amplifier, and after the power supply current is detected, it is sent to Until the second band-stop filter filters out the fundamental wave, once the power supply current still has harmonics, it can be amplified by the second amplifier to generate an output signal. 8. The active harmonic suppression device according to claim 5, wherein the energy storage DC capacitor voltage stabilization circuit comprises a phase shift circuit, a low-pass filter, a subtractor, and a second controller And a multiplier, the DC voltage of the energy storage DC capacitor is filtered by the low-pass filter to filter the ripple voltage, and the output of the low-pass filter is sent to the subtractor to be subtracted from a set voltage and then sent to the second After the controller, it is output to the multiplier, and the power supply voltage is generated by the phase shift circuit to generate a 90-degree ahead signal, and then output to the multiplier, and the output signal is obtained after being multiplied by the multiplier. 9. The active harmonic suppression device according to claim 5, wherein the reactive power adjustment loop includes a reactive power calculation circuit, a limiter and a multiplier, and the reactive power calculation circuit calculates the required After the compensated reactive power passes through the limiter, the amplitude of the output fundamental voltage of the power converter and the fundamental voltage of the power supply in the same phase can be obtained, and the output of the limiter and the detected power supply voltage are sent to the multiplier. That is, the output signal of the reactive power calculation loop can be obtained, and the limiter is used to limit the range of the maximum value and the minimum value of the reactive power provided by the harmonic suppression device. 10. The active harmonic suppression device according to claim 9, wherein the reactive power calculation circuit comprises a phase shift circuit, a multiplier and a low-pass filter, and the power supply voltage passes through the phase shift circuit After the 90-degree leading phase shift is generated, it is multiplied by the multiplier with the load current, and the output of the multiplier is then taken out by the low-pass filter to obtain the average component, which is the required reactive power compensation amount. 11. The active harmonic suppression device according to claim 9, wherein the reactive power calculation circuit includes a phase detection circuit and an amplifier, and the power supply voltage and current are generated by the phase detection circuit The phase difference is amplified by the amplifier to obtain reactive power compensation.

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