CN103124074B - A kind of power quality compound compensation method - Google Patents

Abstract

The invention relates to a method for composite power quality compensation, comprising the following steps: sampling the current power grid voltage signal, load current signal and compensation current signal of a compensation device, and selecting different command current calculation methods according to different compensation methods. The first compensation method It is the reactive power and fixed order harmonic compensation method; the second compensation method is reactive power and harmonic compensation method. When the first compensation method is selected, first calculate the fundamental reactive power compensation current component, and then calculate the command harmonic Wave current, the two are added to get the composite compensation command current required by the first compensation method. When the second compensation method is selected, the fundamental active current component is obtained first, and the load current is subtracted from the fundamental active current component to obtain Composite compensation instruction current of the second compensation mode, adopting the present invention realizes composite control of reactive power and harmonics, solves the shortcoming of single function of current power quality control devices, and improves the cost performance of power quality control devices.

Description

A Composite Compensation Method for Power Quality

technical field

The invention belongs to the field of compound control of electric energy quality, and in particular relates to a control method of comprehensive reactive power compensation technology and harmonic control technology.

Background technique

Electric energy is an important material guarantee for the rapid development of social economy. In recent years, various electric power users have higher and higher requirements for electric energy quality, and pay more and more attention to various quality problems in the process of electric energy application. The usual power quality problems are mainly caused by various reactive loads, unbalanced loads and nonlinear loads. These devices not only consume a large amount of reactive power during operation, but also generate a large number of harmonics, causing the grid voltage to fluctuate violently. Reduce the efficiency of grid use, seriously affect the quality of grid power supply, and cause users connected to the same grid to fail to work normally. In order to improve the power quality of the power grid, various harmonic suppression and reactive power compensation devices have appeared. The modern static var generator STATCOM has many advantages, such as continuous adjustment, large adjustment range, fast response speed, high control accuracy, and easy operation. Reliable, less harmonic content, small size and other advantages, the cascaded structure is easy to achieve high voltage and large capacity, so that STATCOM has attracted extensive attention from the power industry. At the same time, the control research on STATCOM has also become the focus of discussion at home and abroad.

The current control strategy of STATCOM is an important technology related to the performance of equipment. The current control method can make the output performance and quality of STATCOM different.

One of the existing power quality control methods is applied to devices such as SVC and STATCOM to compensate the reactive power of the grid; the other is applied to devices such as APF to compensate the harmonics of the grid. These two applications are currently It is widely used and has great advantages in reactive power compensation and harmonic control. However, the compensation functions of these two applications are relatively single, and the cost performance is not high for occasions that require multiple compensation methods.

The existing technology applied to power quality control has the following disadvantages:

The function is single, which cannot meet the needs of diverse compensation methods, and the system engineering cost is high and covers a large area.

Contents of the invention

The purpose of the present invention is to provide a composite compensation method for power quality, which can overcome the defects of the existing single power quality control technology. Optimizing compensation can effectively solve the problem of large equipment investment and large floor area.

In order to achieve the purpose of the above invention, the solution adopted is: a composite compensation method for power quality, comprising the following steps:

1) Sampling the current grid voltage signal, load current signal and compensation current signal of the compensation device;

2) Select different command current calculation methods according to different compensation methods. The first compensation method is reactive power and fixed-order harmonic compensation; the second compensation method is reactive power and harmonic compensation. When the first compensation method is selected In the compensation mode, the phase-locked loop is used to extract the synchronous angular frequency of the grid voltage signal, and the synchronous angular frequency wt is used to perform dq transformation on the load current in step 1), to obtain the AC active current component and the AC reactive current component, and the AC reactive current component The current component passes through a low-pass filter to obtain the fundamental reactive power compensation current component;

3) Use the n-time multiplier nwt of the synchronous angular frequency to perform dq transformation on the load current to obtain the d-axis component and q-axis component with the harmonic order n=3k+1, and pass the d-axis component and q-axis component through a low-pass filter , use the synchronous angular frequency of nwt to perform dq inverse transformation to obtain a compensation current with a harmonic order of n=3k+1; use the negative n-time multiplier of the synchronous angular frequency -nwt to perform dq transformation on the load current to obtain a harmonic order of n =3k-1 d-axis component and q-axis component, after the d-axis component and q-axis component are passed through the low-pass filter, the dq inverse transformation is performed with the synchronous angular frequency of -nwt, and the harmonic order is n=3k-1 compensation current;

4) Add the fundamental reactive power compensation current in step 2) and the compensation current with harmonic order n=3k-1 in step 3) to obtain the composite compensation command current required by the first compensation method;

5) When the second compensation method is selected, use the synchronous angular frequency of the grid voltage signal obtained by the phase-locked loop to perform dq transformation on the sampled load current to obtain the d-axis active current component and the q-axis reactive current component. The active component of the d-axis passes through a low-pass filter to obtain the fundamental active current component;

6) After subtracting the fundamental active current component in step 5) from the load current, the compound compensation command current of the second compensation mode is obtained.

As shown in Fig. 1, the present invention is mainly applied to a STATCOM device, and the main power circuit of the device is composed of a three-phase or single-phase topology converter device, a series inductor and a control circuit. The three-phase output of the converter device is connected to the A, B, and C three-phases of the AC power supply through the inductance. The part of the converter device is an inverter structure, which can be a H-bridge-based chain structure or a three-phase bridge structure. The DSP control circuit is used for command current calculation, PWM pulse triggering and control of the DC bus voltage of the converter device.

Beneficial effects of the present invention: the present invention realizes the composite control of reactive power and harmonics, solves the shortcoming of single function of the current power quality control device, and improves the cost performance of the power quality control device.

Description of drawings

Figure 1. Schematic diagram of power quality composite compensation device.

detailed description

A method for compound compensation of power quality, comprising the steps of:

1) Sampling the current grid voltage signal, load current signal and compensation current signal of the compensation device;

2) Select different command current calculation methods according to different compensation methods. The first compensation method is reactive power and fixed-order harmonic compensation; the second compensation method is reactive power and harmonic compensation. When choosing the first In the compensation mode, the phase-locked loop is used to extract the synchronous angular frequency of the grid voltage signal, and the synchronous angular frequency wt is used to perform dq transformation on the load current in step 1), to obtain the AC active current component and the AC reactive current component, and the AC reactive current component The current component passes through a low-pass filter to obtain the fundamental reactive power compensation current component;

3) Use the n-time multiplier nwt of the synchronous angular frequency to perform dq transformation on the load current to obtain the d-axis component and q-axis component with the harmonic order n=3k+1, and pass the d-axis component and q-axis component through a low-pass filter , use the synchronous angular frequency of nwt to perform dq inverse transformation to obtain a compensation current with a harmonic order of n=3k+1; use the negative n-time multiplier of the synchronous angular frequency -nwt to perform dq transformation on the load current to obtain a harmonic order of n =3k-1 d-axis component and q-axis component, after the d-axis component and q-axis component are passed through the low-pass filter, the dq inverse transformation is performed with the synchronous angular frequency of -nwt, and the harmonic order is n=3k-1 compensation current;

4) Add the fundamental reactive power compensation current in step 2) and the compensation current with harmonic order n=3k-1 in step 3) to obtain the composite compensation command current required by the first compensation method;

5) When the second compensation method is selected, use the synchronous angular frequency of the grid voltage signal obtained by the phase-locked loop to perform dq transformation on the sampled load current to obtain the d-axis active current component and the q-axis reactive current component. The active component of the d-axis passes through a low-pass filter to obtain the fundamental active current component;

6) After subtracting the fundamental active current component in step 5) from the load current, the compound compensation command current of the second compensation mode is obtained.

Claims (1)

1. a kind of power quality compound compensation method, comprises the following steps：

The compensating current signal of step one, sampling current electric grid voltage signal, load current signal and compensation device；

Step 2, different instruction current computational methods are selected according to different compensation way, the first compensation way is idle With determine subharmonic compensation way；Second compensation way is idle harmonic compensation way, when the first compensation way is selected, The synchronous angular frequency of mains voltage signal is extracted using phaselocked loop, the load current in step one is entered using synchronous angular frequency wt Row dq is converted, and is obtained exchange active current and is exchanged reactive current component, exchange reactive current component by low pass filtered Ripple device, obtains fundamental wave reactive power compensation current component；

Step 3, dq conversion is carried out to load current using n frequency multiplication nwt of synchronous angular frequency obtain overtone order for n=3k+1 D axles component and q axle components, by d axles component and q axles component by low pass filter, dq is carried out with the synchronous angular frequency of nwt anti- Conversion, obtains the compensation electric current that overtone order is n=3k+1；Negative n frequency multiplication-nwt using synchronous angular frequency enters to load current Row dq conversion obtains the d axles component and q axle components that overtone order is n=3k-1, and d axles component and q axles component are passed through into LPF After device, dq inverse transformations are carried out with the synchronous angular frequency of-nwt, obtain the compensation electric current that overtone order is n=3k-1；

Step 4, the compensation electric current that the overtone order compensated the fundamental wave reactive power in step 2 in electric current and step 3 is n=3k-1 It is added, the combined compensation instruction current needed for obtaining the first compensation way；

Step 5, when select second compensation way when, the synchronous angular frequency of the mains voltage signal obtained using phaselocked loop is right The load current for sampling carries out dq conversion, obtains d axles active current and q axle reactive current components, by d axle active components Fundamental active current component is obtained by low pass filter；

The compound of second compensation way is obtained after step 6, the fundamental active current component for subtracting load current in step 5 Compensating instruction electric current.