KR20200098924A - Hybrid power quality compensation device - Google Patents

Abstract

The present invention relates to a hybrid power quality compensation device. More specifically, the hybrid power quality compensation device compensates for a disadvantage of each of a static var compensator (SVC) and a unified power quality conditioner (UPQC) in a form in which the SVC and UPQC are combined and enhances power quality compensation for costs. To this end, the hybrid power quality compensation device comprises a serial transformer, a low pass filter, a serial inverter, a parallel transformer, the SVC, a parallel inverter, and a direct current capacitor.

Description

Hybrid Power Quality Compensation Device{HYBRID POWER QUALITY COMPENSATION DEVICE}

The present invention relates to a hybrid power quality compensation device, and more particularly, in a form in which SVC (Static Var Compensator) and UPQC (Unified Power Quality Conditioner) are combined to compensate for the disadvantages of each of SVC and UPQC, and power quality compensation capability for cost. It relates to this enhanced hybrid power quality compensation device.

The present invention was supported by the Korea Electric Power Corporation's 2018 energy base university cluster project. (Task number:R18XA04)

The present invention was supported by KEPCO's external public offering basic research (individual). (Task number:R18XA06-60)

Recently, as the use of semiconductor devices and electric power electronic devices in general homes or offices has increased rapidly, the amount of harmonics and reactive power generated by these devices increases, leading to serious problems in the surrounding environment and electrical loss.

Power electronics are widely used in automation facilities, building facilities, and even home appliances, and these power electronics devices have nonlinear characteristics.

Therefore, the electronic devices distort the voltage waveform of the power distribution system as a source of harmonic current, overheating the transformer of the substation, adversely affecting other connected loads, and cause a magnetic induction failure in adjacent communication lines.

Under this situation, loads sensitive to power quality rapidly increase, and devices that require various power quality according to the sensitivity of the load are increasingly required.

In other words, the demand for high power quality is increasing rapidly.

Conventionally, a static var compensator (SVC) or a unified power quality conditioner (UPQC) has been used as a device for compensating power quality.

In the case of SVC (Static Var Compensator), which is a power quality compensation device, it is mainly used to dynamically compensate for reactive power when the load changes frequently, but SVC has problems such as a resonance problem and a slow response property when harmonic current is injected.

In the case of UPQC (Unified Power Quality Conditioner), which is a power quality compensating device with fast response, there is a problem that a lot of cost occurs when designing a large rating using a power electronic switch.

In Korean Patent Registration [10-1128377], an electric energy power saving device having a function of improving power quality is disclosed.

Korean Patent Registration [10-1128377] (Registration Date: March 13, 2012)

Accordingly, the present invention was devised to solve the above-described problems, and the object of the present invention is to complement the disadvantages of each of SVC and UPQC in a form in which SVC (Static Var Compensator) and UPQC (Unified Power Quality Conditioner) are combined. And it is to provide a hybrid power quality compensation device with enhanced power quality compensation capability for cost.

Objects of the embodiments of the present invention are not limited to the above-mentioned objects, and other objects not mentioned will be clearly understood by those of ordinary skill in the art from the following description. .

A hybrid power quality compensation apparatus according to an embodiment of the present invention for achieving the above object includes: a series transformer 100 connected in series to a front end of a line between a power system 1 and a load 2; A low-pass filter 200 connected to the secondary side of the series transformer 100 and composed of a reactor 210 and a capacitor 220; A series inverter 300 having a bridge structure connected between the reactor 210 of the low pass filter 200 and the capacitor 220; A parallel transformer 400 connected in parallel to the rear end of the line between the power system 1 and the load 2; SVC (Static Var Compensator) 500 connected in series to the secondary side of the parallel transformer 400; A parallel inverter 600 having a bridge structure connected in series between the serial inverter 300 and the SVC 500; And a DC capacitor having one side connected to one line between the serial type inverter 300 and the parallel type inverter 600 and the other side connected to the other side line between the series type inverter 300 and the parallel type inverter 600. (700); includes.

In addition, the SVC 500 uses FC-TCR (Fixed Capacitor-Thyristor Controlled Reactor), determines the firing angle through calculation of instantaneous active and reactive power, and controls the SVC using the Thyristor firing angle, It is characterized by controlling Reactor through.

In addition, the SVC (500) is the following equation

은 FC-TCR의 점호각(

)에 따른 임피던스를 의미한다.)(here,

Is the firing angle of FC-TCR (

) Means the impedance according to.)

It is characterized in that the reactive power compensation is performed through the control of the thyristor firing angle as described above.

을 만족시키는 공진점 조정 설계를 하여, 수동(Passive) 소자의 공진 문제를 해결하는 필터(800)가 병렬형변압기(400)와 SVC(500) 사이에 직렬로 구비된 것을 특징으로 한다.In addition, the hybrid power quality compensation device is a harmonic order

A filter 800 for solving the resonance problem of a passive element is provided in series between the parallel transformer 400 and the SVC 500 by designing a resonance point adjustment that satisfies

According to the hybrid power quality compensation apparatus according to an embodiment of the present invention, when designing in a form in which SVC and UPQC are combined, it is possible to design a small rated UPQC, thereby reducing cost.

In addition, by using a serial type inverter (voltage control) and a parallel type inverter (current control), there is an effect of enabling rapid control when Sag, Swell, Flicker, Interruption, etc. occur.

In addition, it is possible to simultaneously remove harmonics and compensate for reactive power by calculating the instantaneous active and reactive power by measuring the voltage and current applied to the load, and extracting and compensating the harmonic component through a low-pass filter.

In addition, by using FC-TCR as the SVC and determining the firing angle through calculation of instantaneous active and reactive power, there is an effect that it is possible to control the firing angle through Thyristor switching.

을 만족시키는 공진점 조정 설계를 하여, 수동(Passive) 소자의 공진 문제를 해결하는 필터를 구비함으로써, Passive 소자의 공진 문제를 해결할 수 있는 효과가 있다.In addition, harmonic order

By providing a filter that solves the resonance problem of a passive element by designing a resonance point adjustment that satisfies the above, there is an effect of solving the resonance problem of the passive element.

1 is a conceptual diagram of a hybrid power quality compensation apparatus according to an embodiment of the present invention.
2 is an exemplary diagram showing a VI characteristic curve when a system is designed in a conventional SVC type.
3 is an exemplary view showing a VI characteristic curve when a system is designed in a conventional UPQC format.
4 is an exemplary view showing a VI characteristic curve of a hybrid power quality compensation apparatus according to an embodiment of the present invention.
5 is a conceptual diagram of a hybrid power quality compensation apparatus according to another embodiment of the present invention using FC-TCR as an SVC in a three-phase AC power system.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to a specific embodiment, it should be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

When a component is referred to as being "connected" or "connected" to another component, it is understood that it may be directly connected or connected to the other component, but other components may exist in the middle. Should be.

On the other hand, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there is no other component in the middle.

The terms used in the present specification are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, processes, operations, components, parts, or combinations thereof described in the specification, but one or more other features. It is to be understood that the possibility of addition or presence of elements or numbers, processes, operations, components, parts, or combinations thereof is not preliminarily excluded.

Unless otherwise defined, all terms including technical or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning of the related technology, and should not be interpreted as an ideal or excessively formal meaning unless explicitly defined in this application. Does not.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventors appropriately explain the concept of terms in order to explain their own invention in the best way. Based on the principle that it can be defined, it should be interpreted as a meaning and concept consistent with the technical idea of the present invention. In addition, unless there are other definitions in the technical terms and scientific terms used, they have the meanings commonly understood by those of ordinary skill in the art to which this invention belongs, and the gist of the present invention in the following description and accompanying drawings Descriptions of known functions and configurations that may be unnecessarily obscure will be omitted. The drawings introduced below are provided as examples in order to sufficiently convey the spirit of the present invention to those skilled in the art. Accordingly, the present invention is not limited to the drawings presented below and may be embodied in other forms. In addition, the same reference numbers throughout the specification indicate the same elements. It should be noted that the same elements in the drawings are indicated by the same reference numerals wherever possible.

1 is a conceptual diagram of a hybrid power quality compensation apparatus according to an embodiment of the present invention, FIG. 2 is an exemplary diagram showing a VI characteristic curve when a system is designed in a conventional SVC type, and FIG. 3 is a conventional UPQC type Fig. 4 is an exemplary diagram showing a VI characteristic curve when a furnace system is designed, Fig. 4 is an exemplary diagram showing a VI characteristic curve of a hybrid power quality compensation device according to an embodiment of the present invention, and Fig. 5 is a three-phase AC power system It is a conceptual diagram of a hybrid power quality compensation apparatus according to another embodiment of the present invention using FC-TCR as an SVC.

In the case of the conventional UPQC system, it is a model with fast response and excellent power quality compensation performance. However, when designing a high rating due to the power electronic switch-based design, a lot of cost is required.

In the present invention, a new hybrid UPQC type has been developed that can improve the disadvantages of the existing UPQC and exhibit cost-effective performance.

The hybrid power quality compensation apparatus according to an embodiment of the present invention is a combination of SVC and UPQC.

When combined with SVC, when reactive power is compensated, a large amount of reactive power is compensated by the SVC, and UPQC can be designed with a small rating.

Therefore, it has the advantages of fast response and harmonic compensation of the existing UPQC, and it compensates for the disadvantage of high cost by enabling design with a small rating.

As shown in Fig. 1, the hybrid power quality compensation apparatus according to an embodiment of the present invention includes a series transformer 100, a low pass filter 200, a series inverter 300, a parallel transformer 400, and SVC. (Static Var Compensator) 500, a parallel type inverter 600 and a DC capacitor 700.

The series transformer 100 is connected in series to the front end of the line between the power supply system 1 and the load 2.

In the series transformer 100, the primary side of the series transformer 100 is connected in series to a line between the power supply system 1 and the load 2. That is, the primary side of the series transformer 100 is connected in series on a line between the power supply system 1 and the load 2.

The electrical connection of the secondary side of the series transformer 100 is connected to a series inverter 300 to be described later.

The series-type transformer 100 serves to reduce the voltage rating of the series-type inverter 300.

The low-pass filter 200 is connected to the secondary side of the series transformer 100 and is composed of a reactor 210 and a capacitor 220.

The low pass filter 200 is for extracting harmonic components.

At this time, the reactor 210 is connected to the secondary side of the series transformer 100 and the capacitor 220 is connected to the rear end of the reactor 210.

The capacitor 220 is used to remove high frequency.

A waveform closer to direct current (lower frequency) increases the resistance of the capacitor 220 and makes it difficult to pass, while a waveform closer to AC (higher frequency) decreases resistance of the capacitor 220 to pass through.

That is, the low-pass filter 200 serves as a low pass filter and removes the harmonic switching ripple of the output voltage of the series inverter 300.

The series inverter 300 has a bridge structure connected between the reactor 210 and the capacitor 220 of the low pass filter 200.

The series-type inverter 300 is connected between the reactor 210 and the capacitor 220, and a low-frequency component that has passed through the reactor 210 is supplied to the series-type inverter 300.

The series inverter 300 is for generating a compensation voltage to compensate for reactive power, and the following equation

는 보상전압,

는 부하(2) 측 부하 전단 전압,

는 전원계통(1) 측 전원계통(1) 후단 전압을 의미한다.)(here,

Is the compensation voltage,

Is the load shear voltage on the load (2) side,

Means the voltage at the rear end of the power system (1) side of the power system (1).)

Compensation voltage can be generated like this.

The parallel transformer 400 is connected in parallel to the rear end of the line between the power system 1 and the load 2.

The primary side of the parallel transformer 400 is connected to the SVC 500 to be described later, and the secondary side is connected to the front end of the load 2 which is the rear end of the line between the power system 1 and the load 2.

The parallel transformer 400 serves to reduce the voltage rating of the SVC 500 to be described later.

SVC (Static Var Compensator) 500 is connected in series to the secondary side of the parallel transformer 300.

SVC (Static Var Compensator) 500 is connected to the parallel type inverter 600.

The SVC 500 has a function similar to that of a synchronous control device, and is a device that maintains a voltage within an allowable range by continuously supplying variable lead/ground reactive power from a prescribed reactor and capacitor bank by a thyristor.

The SVC 500 is characterized by fast responsiveness, almost no restrictions on operation, high reliability and simple maintenance,

The SVC 500 is for use in compensation of reactive power (reactive power supply source), and its response time is very fast, so it detects voltage fluctuations for fluctuating loads at high speed to absorb the fluctuations in reactive power, and absorbs reactive power for each phase. By compensating, it eliminates voltage/current unbalance and improves power factor for reactive power loads.

In addition, since it can be used for voltage compensation (voltage control), it increases static stability extreme power by voltage control, and improves transient stability by voltage control when load or power generation is lost, and improves voltage fluctuation rate.

Types of SVCs that can be used as the SVC 500 include TCR, TSC, FC-TCR, TSC-TCR, and the like.

TCR connects anti-parallel thyristor to a fixed reactor to generate ground reactive power, and can continuously control reactive power by PWM control, and can be used for flicker prevention and voltage stabilization.

TSC generates true reactive power by connecting anti-parallel Thyristor S/W to a power capacitor, and can adjust reactive power control in a stepwise fashion by on-off control, and can be used for voltage control purposes.

FC-TCR can generate reactive power by adding a fixed power capacitor to the TCR method, and the adjustment is continuous by continuous control, and can be used for voltage stabilization, power fluctuation suppression, stability improvement, etc. Do.

TSC-TCR is a mixed method of TSC and TCR, capable of generating ground and leading reactive power, continuous adjustment by continuous control, and can be used for voltage stabilization, power fluctuation suppression, stability improvement, etc. Do.

The parallel inverter 600 is a bridge structure connected in series between the serial inverter 300 and the SVC 500.

The parallel inverter 600 is for generating a compensation current to compensate for reactive power, and the following equation

는 보상전압,

는 전원계통(1) 측 전원계통(1) 후단 전류,

는 부하(2) 측 부하 전단 전류를 의미한다.)(here,

Is the compensation voltage,

Is the current at the rear end of the power system (1) on the power system (1) side,

Means the load shear current on the load (2) side.)

Compensating current can be generated as

That is, the parallel inverter 600 serves to maintain the DC Bus Voltage as a reference value and to remove harmonics generated by a nonlinear load.

The DC capacitor 700 is connected to one side of the line between the series type inverter 300 and the parallel type inverter 600, and the other side line between the series type inverter 300 and the parallel type inverter 600. The other side is connected.

The DC capacitor 700 is for stabilizing the DC voltage of the inverter by connecting the DC side of the series inverter 200 and the parallel inverter 500 in common, and the series inverter 300 and the parallel type It realizes DC-Link by using a capacitor that interconnects the inverter 600, and plays a role of maintaining a constant self-supporting DC bus voltage.

The hybrid power quality compensating apparatus according to an embodiment of the present invention constitutes a Unified Power Quality Conditioner (UPQC) with the series inverter 300, the parallel inverter 600, and the DC capacitor 700.

As shown in Fig. 1, the hybrid power quality compensation apparatus according to an embodiment of the present invention uses the following equations through SVC and UPQC when reactive power is generated in the load (2).

는 부하에 걸리는 무효전력,

는 보상되는 무효전력,

는 SVC의 보상 무효전력,

는 UPQC의 보상 무효전력을 의미한다.)(here,

Is the reactive power applied to the load,

Is the compensated reactive power,

Is the compensated reactive power of SVC,

Means the compensated reactive power of UPQC.)

By compensating as described above, it is possible to compensate for reactive power in a wider area.

2 is a VI characteristic curve of a conventional SVC, FIG. 3 is a VI characteristic curve of a conventional UPQC, and FIG. 4 is a VI characteristic curve of a hybrid power quality compensation apparatus according to an embodiment of the present invention. In the hybrid power quality compensation apparatus according to the embodiment, as shown in FIG. 4, VI characteristics are increased through SVC+UPQC combination.

Therefore, it has a wider compensation range than when using SVC and UPQC separately.

When the system is designed in the conventional SVC type, the VI characteristic curve as shown in Fig. 2 is shown, and when the system is designed in the conventional UPQC type, the VI characteristic curve is shown as shown in Fig. 3, but according to an embodiment of the present invention The hybrid power quality compensation device shows an increased VI characteristic curve as shown in FIG. 4.

The hybrid power quality compensation apparatus according to an embodiment of the present invention includes a serial type inverter 300 for controlling voltage and a parallel inverter 600 for controlling current when Sag, Swell, Flicker, and Interruption occur. It is possible to compensate for voltage and current more quickly.

In addition, instantaneous active and reactive power is calculated by measuring the voltage and current applied to the load, and it is possible to compensate by extracting the harmonic component through the Low Pass Filter. That is, harmonics and reactive power compensation are possible.

As shown in Figure 5, the SVC 500 of the hybrid power quality compensation apparatus according to an embodiment of the present invention uses a FC-TCR (Fixed Capacitor-Thyristor Controlled Reactor), through calculation of instantaneous active and reactive power. The firing angle is determined, and the SVC may be controlled using the Thyristor firing angle, and the Reactor is controlled through the Thyristor switching.

That is, the firing angle is determined through calculation of the instantaneous active and reactive power, and the SVC is controlled through the thyristor firing angle, so that the reactor can be controlled through the thyristor switching.

In other words, firing angle control is possible through thyristor switching using FC-TCR (Fixed Capacitor-Thyristor Controlled Reactor).

SVC (500) of the hybrid power quality compensation device according to an embodiment of the present invention is the following equation

은 FC-TCR의 점호각(

)에 따른 임피던스를 의미한다.)(here,

Is the firing angle of FC-TCR (

) Means the impedance according to.)

As described above, it may be characterized in that reactive power compensation is performed through the control of the thyristor firing angle.

을 만족시키는 공진점 조정 설계를 하여, 수동(Passive) 소자의 공진 문제를 해결하는 필터(800)가 병렬형변압기(400)와 SVC(500) 사이에 직렬로 구비된 것을 특징으로 할 수 있다.Hybrid power quality compensation apparatus according to an embodiment of the present invention is a harmonic order

It may be characterized in that a filter 800 for solving a resonance problem of a passive element is provided in series between the parallel transformer 400 and the SVC 500 by designing a resonance point adjustment that satisfies the above.

The present invention is not limited to the above-described embodiments, and of course, various modifications can be made without departing from the gist of the present invention as claimed in the claims.

1: power system 2: load
100: in-line transformer
200: low pass filter
210: reactor 220: capacitor
300: serial type inverter
400: parallel type transformer
500: SVC
600: parallel type inverter
700: DC capacitor
800: filter

Claims (4)

A series transformer 100 connected in series to the front end of the line between the power system 1 and the load 2;
A low-pass filter 200 connected to the secondary side of the series transformer 100 and composed of a reactor 210 and a capacitor 220;
A series inverter 300 having a bridge structure connected between the reactor 210 of the low pass filter 200 and the capacitor 220;
A parallel transformer 400 connected in parallel to the rear end of the line between the power system 1 and the load 2;
SVC (Static Var Compensator) 500 connected in series to the secondary side of the parallel transformer 400;
A parallel inverter 600 having a bridge structure connected in series between the serial inverter 300 and the SVC 500; And
A DC capacitor ( 700);
Hybrid power quality compensation device comprising a.
The method of claim 1,
The SVC 500 is
FC-TCR (Fixed Capacitor-Thyristor Controlled Reactor) is used,
A hybrid power quality compensation device, characterized in that the firing angle is determined through calculation of the instantaneous active and reactive power, and the SVC is controlled using the Thyristor firing angle, and the Reactor is controlled through Thyristor switching.
The method of claim 2,
The SVC (500) is the following equation

(here,

Is the firing angle of FC-TCR (

) Means the impedance according to.)
Hybrid power quality compensation device, characterized in that the reactive power compensation through the Thyristor firing angle control as described above.
The method of claim 1,
The hybrid power quality compensation device
Harmonic order

Hybrid power quality compensation, characterized in that a filter 800 that solves the resonance problem of a passive element is provided in series between the parallel transformer 400 and the SVC 500 by designing a resonance point adjustment that satisfies Device.

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