CN102904259A - PAM (pulse amplitude modulation)-inverter-based cascade STATCOM (static synchronous compensator) control method - Google Patents

Abstract

The invention relates to a PAM (pulse amplitude modulation)-inverter-based cascade STATCOM (static synchronous compensator) control method. The method comprises the following steps that: S1: to-be-compensated reactive power of a power grid and a reference reactive power output by a compensator are subjected to PI adjustment, thereby obtaining the reactive power output by the compensator; S2. an offset angle delta between a power supply voltage and a STATCOM output voltage can be obtained through the reactive power calculation; S3. the sine of an angle obtained from adding initial phase angle obtained by a phase-locked loop to the offset angle delta is solved, thereby obtaining a reference voltage waveform required by the PAM inverter; S4. the switch angle of each H-bridge is calculated through PAM modulation for the reference voltage, finally the compensation voltage output by each phase of the reactive compensator through lamination is obtained; and S5. aiming at the variation required by reactive compensation, a neural network adaptive PI controller is adopted, parameters of the controller kp and ki are set on line by the neural network, and the neural network sets the parameters of the PI controller according to the running state of the system through self learning and the adjustment on the weight number so as to achieve the best performance index.

Description

Cascade STATCOM control method based on the PAM inverter

Technical field

The present invention relates to the STATCOM in the electric power quality reactive power compensation, particularly relate to a kind of STATCOM control method based on the PAM inverter.

Background technology

STATCOM (STATCOM) can the effective compensation reactive power, keeps the voltage stabilization of access point, thereby reaches the purpose of improving the quality of power supply.Compare traditional Static Var Compensator (SVC), STATCOM has better reactive power characteristic and voltage stabilization characteristic, and cascaded multilevel structure, harmonic wave of output voltage is little, loss is low except having, the low cost and other advantages, also have simple in structure, required device is few, be easy to the expansion and modular characteristics, being the optimal selection of the many level of large capacity, also is the focus of Recent study.

The pulse modulation mode is to reduce the effective ways of contained low-order harmonic composition in the inverter output voltage, has again the function of adjusting output frequency and output voltage simultaneously, has therefore obtained developing widely and using in electrical engineering and power industry field.Up to the present, pulse modulation mode mainly contains 3 kinds of pulse amplitude modulation (PAM), pulse width modulation (PWM), pulse frequency modulated (PFM).Wherein front two kinds of modulation systems are used more, particularly the PWM mode is controlled at converter system with its good variable voltage variable frequency characteristic and harmonic suppression effect, Electric Machine Control and other electrical industry fields are generally paid attention to. but the PWM system is in structure, control, operation, debugging and safeguard that the aspect is all relatively complicated and difficult, add the impact of some measures in the PWM method implementation process, existence such as Dead Time can make frequency converter can not fully accurately reappear the ideal waveform of pwm control signal, can not accurately realize controlling target, or produce more multiple-harmonic and cause the output torque pulsation, or make electric current, magnetic linkage tracking performance variation, these factors are all so that the PWM mode can not obtain gratifying control effect in some application scenario.And can not show a candle to the PAM mode of PWM mode as concerned degree, have then that switching loss is low, control is simple, the system effectiveness high; Simultaneously, the PAM mode can reach with lower switching frequency the harmonic wave eradicating efficacy close with the PWM mode, and this also is a remarkable advantage of PAM mode.

Summary of the invention

Do not need pressure regulation for some application scenario, only need to improve output voltage waveforms, reduce harmonic content, the present invention proposes a kind of STATCOM control method based on the PAM inverter.The method is found the solution the switch angle of each H bridge according to finding the solution the optimal objective function, and at last stack obtains the voltage waveform of desired output; And solving dc-voltage balance problem employing H bridge modulation ratio circulation exchange control program; The neural net adaptive PI controller has been proposed to regulate the PI parameter for idle variation to be compensated.

The present invention takes following technical scheme: based on the STATCOM control method of PAM inverter, it is characterized in that: it can be according to the variation of required compensating power, under lower switching frequency, realize the purpose of reactive power compensation by the PAM modulator approach, select corresponding PI controller parameter for different access loads, to adapt to the variation of load.

A kind of cascade STATCOM control method based on the PAM inverter comprises the following steps:

S1: the reference reactive power of the reactive power that electrical network is to be compensated and the output of compensator device is regulated the reactive power that is compensated device output by PI;

S2: above-mentioned reactive power is brought into Q in the formula (1) by calculating the deviation angle δ between supply voltage and STATCOM output voltage;

$\left\{\begin{array}{c}P=\frac{U_S^2}{R}{\sin }^2\mathrm{\&delta;}\\ Q=\frac{{\mathrm{<figure-callout\; id="2"\; label="U\; S"\; filenames="HDA00001953169700012.png"\; state="\{\{state\}\}">U</figure-callout>}}_S^{}}{2R}\sin 2\mathrm{\&delta;}\end{array}\right.---\left(1\right)$

U _SBe line voltage, R is the resistance of linked reactor; P is the active-power P that STATCOM absorbs from electric power system; The reactive power of Q for providing to electric power system;

S3: obtain the needed reference voltage waveform of PAM inverter after the initial phase angle that is obtained by phase-locked loop adds resulting deviation angle δ sineization;

S4: reference voltage is modulated the final stack of the switch angle of calculating each H bridge by PAM and is obtained each bucking voltage of exporting mutually of reactive-load compensator;

S5: adopt a kind of neural net adaptive PI controller for the variation of required compensating reactive power, its controller parameter k _p, k _iAdjusted by Neural Network Online, neural net is according to the running status of system, and by the adjustment of self study and weights, the parameter of on-line tuning PI controller is in the hope of reaching the optimum of performance index.

Preferably, described method adopts the pulse modulated method of PAM inverter.

Preferably, described method adopts H bridge modulation ratio circulation exchange control program.

Preferably, described method adopts neural network adaptive controller with automatic adjusting PI parameter.

Secondly in order to solve the dc-voltage balance problem, adopt H bridge modulation ratio circulation exchange control program, whenever, through a fundamental frequency cycles each H bridge trigger impulse is once rotated, is finished a circulation through ten fundamental frequency cycles, like this so that on average meaning dc voltage reach balance.

The present invention is owing to take above technical scheme, and it has the following advantages: 1. inverter adopts the PAM modulation scheme, can obtain identical harmonic wave with respect to PWM under lower switching frequency and eliminate and the reactive power compensation effect; 2. this design has solved the unbalanced problem of dc voltage and need the compensating power variation be the problem of tuning of PI parameter; 3. the method is easy to realize in engineering reality.

Description of drawings

Fig. 1 is the main circuit structure schematic diagram of chain type STATCOM;

The vectogram of output voltage and electric current when Fig. 2 is the STATCOM steady operation;

Fig. 3 a is the voltage waveform behind each single-phase inversion H bridge vector superposition;

Fig. 3 b is modulation ratio circulation swap operation schematic flow sheet;

Fig. 4 is the neural network adaptive controller schematic diagram;

Fig. 5 is the flow chart of a kind of cascade STATCOM control method based on the PAM inverter of the present invention.

Embodiment

Below in conjunction with drawings and Examples the present invention is described in detail.

Fig. 1 is the main circuit structure schematic diagram of chain type STATCOM, whenever is in series by a plurality of half-bridge converters (H bridge), and three-phase is independent separately, realizes easily a minute phase control.The vectogram of output voltage and electric current, wherein U when Fig. 2 is the STATCOM steady operation _SBe line voltage, U _IBe the compensator output voltage, Δ U is U _SAnd U _IVector difference, I _IBe the compensator output current, R and X are respectively resistance and the inductance of linked reactor.Can get STATCOM after the derivation of equation from the active-power P of electric power system absorption with to the reactive power Q that electric power system provides is:

$\left\{\begin{array}{c}P=\frac{U_S^2}{R}{\sin }^2\mathrm{\&delta;}\\ Q=\frac{{\mathrm{<figure-callout\; id="2"\; label="U\; S"\; filenames="HDA00001953169700012.png"\; state="\{\{state\}\}">U</figure-callout>}}_S^{}}{2R}\sin 2\mathrm{\&delta;}\end{array}\right.---\left(1\right)$

Know from following formula, by the angle between computing system voltage and the compensator output voltage, just can obtain the size of the reactive power of needs compensation.

According to the control requirement of large capacity STATCOM, the control target of PAM is:

1. make the fundamental voltage amplitude of total output voltage be the control desired value,

2. make the low-order harmonic performance of total output voltage reach optimum.

According to above control target, it can be expressed as mathematical optimization problem, wherein, the optimal objective function is:

MinF is the optimal objective function in the following formula, and n is harmonic number, and H is the high order harmonic component number of times that compensates, K _nBe the weights coefficient, can effectively eliminate certain specific times harmonic, a by changing _nAmplitude for each harmonic.Can calculate the switch angle of each Cascade H bridge by finding the solution optimal function, then each H bridge output voltage stack be got final product to get every mutually reactive power compensation voltage of output.Method by the PAM modulation can obtain preferably harmonic characterisitic and compensation effect under lower switching frequency.

Such as Fig. 5, a kind of cascade STATCOM control method based on the PAM inverter, it may further comprise the steps:

S1: the reference reactive power of the reactive power that electrical network is to be compensated and the output of compensator device is regulated the reactive power that is compensated device output by PI;

S2: above-mentioned reactive power is brought into Q in the formula (1) by calculating the deviation angle δ between supply voltage and STATCOM output voltage;

S3: obtain the needed reference voltage waveform of PAM inverter after the initial phase angle that is obtained by phase-locked loop adds resulting deviation angle δ sineization;

S4: reference voltage is modulated the final stack of the switch angle of calculating each H bridge by PAM and is obtained each bucking voltage of exporting mutually of reactive-load compensator.

S5: adopt a kind of neural net adaptive PI controller for the variation of required compensating reactive power, its controller parameter k _p, k _iAdjusted by Neural Network Online, neural net is according to the running status of system, and by the adjustment of self study and weights, the parameter of on-line tuning PI controller is in the hope of reaching the optimum of performance index.

Secondly in order to solve the dc-voltage balance problem, adopt H bridge modulation ratio circulation exchange control program, whenever, through a fundamental frequency cycles each H bridge trigger impulse is once rotated, is finished a circulation through ten fundamental frequency cycles, like this so that on average meaning dc voltage reach balance.

Single-phase inversion H bridge modulation ratio circulation exchange control program main thought is: the mean value of single-phase inversion H bridge modulation ratio keeps constant arbitrarily in N power frequency period time range, namely

Keep constant.

The concrete operations scheme is: orderly circulation change, i.e. M occur in single-phase inversion H bridge modulation ratio behind each power frequency period arbitrarily ₁→ M _N→ M ₁, cycle period is N power frequency period, and the operating process schematic diagram is shown in Fig. 3 b, and Fig. 3 a is depicted as the voltage waveform behind each single-phase inversion H bridge vector superposition, and obviously there is not any impact in modulation ratio circulation exchange control program for the device output voltage waveforms.Show that by Digital Simulation this control strategy can effectively be regulated chain type STATCOM dc voltage distribution situation so that the device in the steady-state adjustment process and the transient state adjustment process in each dc voltage substantially be consistent.

Need to carry out PI and regulate in obtaining the reference voltage process, the PI controller directly carries out closed-loop control to controlled device, its controller parameter k _p, k _iAdjusted by Neural Network Online; Neural net is according to the running status of system, and by the adjustment of self study and weights, the parameter of on-line tuning PI controller is in the hope of reaching the optimum of performance index.Neural network adaptive controller provides in Fig. 4.

Claims (4)

1. the cascade STATCOM control method based on the PAM inverter is characterized in that, comprises the following steps:

S1: the reference reactive power of the reactive power that electrical network is to be compensated and the output of compensator device is regulated the reactive power that is compensated device output by PI;

S2: above-mentioned reactive power is brought into Q in the formula (1) by calculating the deviation angle δ between supply voltage and STATCOM output voltage;

$\left\{\begin{array}{c}P=\frac{U_S^2}{R}{\sin }^2\mathrm{\&delta;}\\ Q=\frac{U_S^2}{2R}\sin 2\mathrm{\&delta;}\end{array}\right.---\left(1\right)$

U _SBe line voltage, R is the resistance of linked reactor; P is the active-power P that STATCOM absorbs from electric power system; The reactive power of Q for providing to electric power system;

S3: obtain the needed reference voltage waveform of PAM inverter after the initial phase angle that is obtained by phase-locked loop adds resulting deviation angle δ sineization;

S4: reference voltage is modulated the final stack of the switch angle of calculating each H bridge by PAM and is obtained each bucking voltage of exporting mutually of reactive-load compensator;

S5: adopt a kind of neural net adaptive PI controller for the variation of required compensating reactive power, its controller parameter k _p, k _iAdjusted by Neural Network Online, neural net is according to the running status of system, and by the adjustment of self study and weights, the parameter of on-line tuning PI controller is in the hope of reaching the optimum of performance index.

2. the cascade STATCOM control method of a kind of PAM inverter as claimed in claim 1 is characterized in that: the pulse modulated method of described method employing PAM inverter.

3. the as claimed in claim a kind of cascade STATCOM control method based on the PAM inverter is characterized in that: described method employing H bridge modulation ratio circulation exchange control program.

4. kind as claimed in claim 1 is characterized in that based on the cascade STATCOM control method of PAM inverter: described method adopts neural network adaptive controller with automatic adjusting PI parameter.

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