CN204290321U - Micro-capacitance sensor voltage perturbation control system - Google Patents

Abstract

The utility model provides a micro-grid voltage perturbation control system, which includes: an energy storage unit, a converter unit, a coordinate transformation and active power calculation unit, a power controller, a voltage controller, an adaptive limiter, a current Controller, PWM generator; adaptive limiter, used to limit the active current reference value output by the power controller and the reactive current reference value output by the voltage controller, and output active reference current and reactive reference current; The PWM generator is used to perform PWM modulation on the voltage control signal to generate a PWM waveform, which is input to the converter unit. The utility model solves the technical problems of frequent voltage fluctuations and difficult optimal distribution of reactive power in the micro-grid in the prior art, and achieves the technical effect of effectively suppressing the voltage fluctuation of the micro-grid and ensuring stable voltage operation.

Description

Microgrid Voltage Perturbation Control System

technical field

The utility model relates to the technical field of micro-grids, in particular to a micro-grid voltage perturbation control system.

Background technique

In recent years, with the rapid development of micro-grids, micro-grids formed by wind power and solar power have gradually become the mainstream of new energy power supply. Due to the randomness, volatility and intermittent characteristics of wind power and photovoltaic power generation, the voltage in the microgrid formed by wind power generation often fluctuates frequently, causing voltage perturbation, which seriously affects the voltage stability of the microgrid. In order to solve the above problems, a large-scale energy storage device is connected to the microgrid to stabilize the voltage and frequency in the microgrid. Through the introduction of large-scale energy storage technology, the operation characteristics of intermittent power supply can be effectively improved in real time, and the regulation ability of micro-grid can be improved, thereby improving the stability and reliability of micro-grid operation, and at the same time increasing the grid-connected capacity of micro-grid.

At present, the new energy storage technology represented by electrochemical energy storage has developed from small capacity and small scale to the research and application of large capacity and large-scale energy storage systems. To solve the problem of large-scale new energy grid connection, relying on the energy storage system of the wind-solar-storage demonstration power station, it can also carry out research on many related topics including panoramic monitoring of combined power generation systems, operation and maintenance technology, etc.

However, how to make full use of large-scale energy storage devices to participate in the perturbation control of the microgrid voltage and optimize the power distribution in the microgrid has not yet proposed an effective solution.

Utility model content

The embodiment of the utility model provides a micro-grid voltage perturbation control system to solve the technical problems of frequent voltage fluctuations and difficult optimal distribution of reactive power in the micro-grid in the prior art. The system includes:

Energy storage unit, converter unit, coordinate transformation and active power calculation unit, power controller, voltage controller, adaptive limiter, current controller, PWM (Pulse Width Modulation, pulse width modulation) generator;

Wherein, the energy storage unit is used to supply power for the microgrid;

The converter unit is connected to the output terminal of the energy storage unit, and is used to adjust the output current of the energy storage unit to meet the reactive current demand of the microgrid;

The coordinate transformation and active power calculation unit, the input terminal is connected to the output terminal of the converter unit, and is used to convert the variable on the ABC coordinate system output by the converter unit to the variable on the rotating coordinate system dq, wherein , the output end of the coordinate transformation and active power calculation unit includes: an active current feedback output end, a reactive current feedback output end and an active power output end;

In the power controller, the input end is connected to the active power reference value, and is connected to the active power output end of the coordinate transformation and active power calculation unit, and the output end includes: an active current reference value output end;

In the voltage controller, the input terminal is connected to the microgrid voltage and the microgrid voltage reference value, and the output terminal includes: a reactive current reference value output terminal;

The input end of the adaptive limiter is connected to the active current reference value output end of the power controller and the reactive current reference value output end of the voltage controller, and is used to control the active power output by the power controller. The current reference value and the reactive current reference value output by the voltage controller are limited, and the active reference current and the reactive reference current are output;

The input end of the current controller is connected to the output end of the adaptive limiter, and is connected to the active current feedback output end and the reactive current feedback output end of the coordinate transformation and active power calculation unit, for adjusting the active current and the reactive current of the microgrid, so that the active current and the reactive current can track the active reference current and the reactive reference current, and the output terminal of the current controller outputs a voltage control signal;

The PWM generator is connected to the output terminal of the current controller, and is used for performing PWM modulation on the voltage control signal to generate a PWM waveform, which is input to the converter unit.

In one embodiment, the adaptive limiter includes: an active current limiting circuit, a reactive current limiting circuit, a first square processing circuit, a second square processing circuit, an accumulation circuit, a square root processing circuit, and a minimum value circuit, where:

The input terminal of the active current limiting circuit is connected to the active current reference value output terminal of the power controller, and the output terminal of the active current limiting circuit is connected to the first input terminal of the minimum circuit;

The input terminal of the reactive current limiting circuit is connected to the reactive current reference value output terminal of the voltage controller, and the output terminal of the reactive current limiting circuit is the reactive reference value of the adaptive limiter current output;

The input of the first square processing circuit is the reference current limit value output by the converter unit, and the output terminal of the first square processing circuit is connected to the positive input terminal of the accumulation circuit;

The input end of the second square processing circuit is connected to the reactive current reference value output end of the voltage controller, and the output end of the second square processing circuit is connected to the negative value input end of the accumulation circuit;

The output end of the accumulation circuit is connected to the input end of the square root processing circuit, and the output end of the square root processing circuit is connected to the second output end of the minimum value circuit;

The output terminal of the minimum circuit is the active reference current output terminal of the adaptive limiter.

In one embodiment, the converter unit includes: a three-phase converter, which is used to convert the energy of the energy storage unit into energy that needs to be compensated when the microgrid voltage is perturbed;

The filter reactance is connected with the three-phase converter, and is used to filter out high-order harmonics generated when the DC power in the energy storage unit is converted into AC reactive power of the microgrid.

In one embodiment, the three-phase converter includes: a device for converting DC power into AC power under PWM control.

In one embodiment, the power controller is provided with a first PI regulator, and the first PI regulator is used to input the power setting value to be compensated for the active power output by the three-phase converter into In the microgrid;

The voltage controller is provided with a second PI regulator, and the second PI regulator is used to input the voltage perturbation setting value that needs to be compensated for the reactive power output by the three-phase converter to the micro in the grid.

In one embodiment, the PWM generator is also used for interlocking, electrically isolating and power amplifying the two driving signals on the same bridge arm of the main circuit.

In one embodiment, the three-phase converter is composed of six fully-controlled switching devices.

In one embodiment, the power controller and the voltage controller are provided with PI regulators for PI regulation.

In one embodiment, the PWM generator is a SKYPER32 PWM generator.

In the embodiment of the utility model, a micro-grid voltage perturbation control system is provided. When the voltage in the micro-grid fluctuates frequently, by detecting the voltage and current in the micro-grid, the voltage control perturbation device is used to make large-scale The energy in the energy storage unit is converted into the reactive current in the stable microgrid, so that the transient voltage can be restored to the normal level. At the same time, by adding an adaptive limiter, the microgrid voltage can fluctuate in a large range, faster Stable at the normal level, thereby ensuring the safe and reliable operation of the micro-grid. The utility model solves the technical problems of frequent voltage fluctuations and difficult optimal distribution of reactive power in the micro-grid in the prior art, and effectively suppresses the voltage fluctuation of the micro-grid. , to ensure the technical effect of voltage stable operation.

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the utility model, constitute a part of the application, and do not constitute a limitation to the utility model. In the attached picture:

Fig. 1 is a schematic structural diagram of a microgrid voltage perturbation control system according to an embodiment of the present invention;

Fig. 2 is the circuit diagram of the converter unit of the utility model embodiment;

Fig. 3 is the circuit diagram of the adaptive limiter of the utility model embodiment;

Fig. 4 is a schematic diagram of the output reference current trajectory of the adaptive limiter according to the embodiment of the present invention;

Fig. 5 is a schematic diagram of the output power curve of the voltage perturbation device when the grid side voltage drops according to the embodiment of the utility model;

Fig. 6 is a block diagram of the inner loop current control of the converter unit of the embodiment of the present invention;

Fig. 7 is the overall architecture diagram of the control system of the utility model embodiment;

Fig. 8 is a structural diagram of a microgrid with a voltage perturbation device according to an embodiment of the present invention;

Fig. 9 is a schematic diagram of the phase voltage waveform output by the voltage perturbation device according to the embodiment of the present invention;

Fig. 10 is a schematic diagram of the phase current waveform output by the voltage perturbation device according to the embodiment of the present invention;

Fig. 11 is a schematic diagram of the microgrid voltage amplitude fluctuation waveform before compensation according to the embodiment of the present invention;

Fig. 12 is a schematic diagram of the voltage amplitude fluctuation waveform of the microgrid after compensation according to the embodiment of the utility model;

Fig. 13 is a schematic diagram of the active power waveform output by the voltage perturbation device of the embodiment of the present invention;

Fig. 14 is a schematic diagram of the reactive power waveform output by the voltage perturbation device of the embodiment of the present invention;

Fig. 15 is a block diagram of the hardware principle circuit of the voltage perturbation device according to the embodiment of the present invention;

Fig. 16 is a flow chart of a microgrid voltage perturbation control method according to an embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the utility model clearer, the utility model will be further described in detail below in combination with the embodiments and accompanying drawings. Here, the exemplary implementation of the utility model and its description are used to explain the utility model, but not as a limitation to the utility model.

In this example, a microgrid voltage perturbation control system is provided, as shown in Figure 1, including: energy storage unit, converter unit, coordinate transformation and active power calculation unit, power controller, voltage controller, automatic To adapt to the limiter, current controller, and PWM generator, the functions of these components, the connection relationship between them and the signal flow direction are described below;

1) Energy storage unit for powering the microgrid;

2) The converter unit is connected to the output terminal of the energy storage unit, and is used to adjust the output current of the energy storage unit to meet the reactive current demand of the microgrid;

3) Coordinate transformation and active power calculation unit, the input terminal is connected to the output terminal of the converter unit, and is used to convert the variable on the ABC coordinate system output by the converter unit to the variable on the rotating coordinate system dq, wherein, the The output terminals of the coordinate transformation and active power calculation unit include: active current feedback output terminals, reactive current feedback output terminals and active power output terminals;

4) a power controller, the input end is connected to the active power reference value, and is connected to the active power output end of the coordinate transformation and active power calculation unit, and the output end includes: an active current reference value output end;

5) A voltage controller, the input terminal is connected to the microgrid voltage and the microgrid voltage reference value, and the output terminal includes: a reactive current reference value output terminal;

6) Adaptive limiter, the input end is connected with the active current reference value output end of the power controller and the reactive current reference value output end of the voltage controller, and is used for the active power outputted by the power controller The current reference value and the reactive current reference value output by the voltage controller are limited, and the active reference current and the reactive reference current are output;

7) A current controller, the input end of which is connected to the output end of the adaptive limiter, and connected to the active current feedback output end and the reactive current feedback output end of the coordinate transformation and active power calculation unit, for adjusting the active current and the reactive current of the microgrid, so that the active current and the reactive current can track the active reference current and the reactive reference current, and the output terminal of the current controller outputs a voltage control signal;

8) A PWM generator, connected to the output terminal of the current controller, used to perform PWM modulation on the voltage control signal to generate a PWM waveform, which is input to the converter unit.

In this example, a microgrid voltage perturbation control system is provided. When the voltage in the microgrid fluctuates frequently, by detecting the voltage and current in the microgrid, the voltage control perturbation device is applied to make the large-scale energy storage unit The energy in the microgrid is converted into reactive current in the stable microgrid, so that the transient voltage can be restored to the normal level. At the same time, by adding an adaptive limiter, the microgrid voltage can be stabilized at the normal level more quickly when it fluctuates in a wide range. level, thereby ensuring the safe and reliable operation of the micro-grid. The utility model solves the technical problems of frequent voltage fluctuations and reactive power distribution in the micro-grid in the prior art, and achieves effective suppression of the voltage fluctuation of the micro-grid and ensures that the voltage The technical effect of stable operation.

The specific functions and working principles of the above-mentioned components are described below in conjunction with Figure 1:

1) Large-scale energy storage unit (ie, the above-mentioned energy storage unit)

The large-scale energy storage unit in the microgrid is mainly composed of multiple groups of various types of batteries, which store the energy of wind and solar energy in the batteries for power supply and voltage suppression of the microgrid.

2) Converter unit

The converter unit can be composed of a three-phase power electronic converter and a filter reactance. Using the basic principle of a synchronous compensator, the self-commutated bridge circuit is connected to the microgrid through a series reactance. According to the input microgrid voltage and active power instructions , properly adjust its AC side current to meet the reactive current demand of the microgrid, realize the purpose of dynamic reactive power compensation, and finally realize the rapid stability of voltage. Specifically, the three-phase converter in the converter unit converts the energy of the large-scale energy storage unit into energy that needs to be compensated when the microgrid voltage is perturbed, and the filter reactance in the converter unit is used to filter out the energy in the energy storage unit The higher harmonics generated when the DC power is converted into the AC reactive power of the microgrid.

Specifically, the structure of the converter can be shown in Figure 2, which is composed of DC capacitor C, IGBT, filter inductor L, and resistor R. The phase converter inputs inductive or capacitive reactive current to the system, and through the six fully-controlled switching devices IGBTs set in the three-phase converter, the DC power can be converted into AC power more quickly under the PWM control method.

U _A represents the space vector of converter output voltage u _Aa , u _Ab and u _Ac , and U _S represents the space vector of microgrid voltage u _Sa , u _Sb , u _Sc .

Then, the relationship between the converter output voltage and the DC side voltage is:

$\left\{\begin{array}{c}{u}_A={\mathrm{MU}}_{\mathrm{dc}}\sin (\mathrm{\ωt}-\mathrm{\δ})\\ u_{\mathrm{Ab}}={\mathrm{MU}}_{\mathrm{dc}}\sin (\mathrm{\ωt}-\frac{2\mathrm{\π}}{3}-\mathrm{\δ})\\ u_{\mathrm{Ac}}={\mathrm{MU}}_{\mathrm{dc}}\sin (\mathrm{\ωt}+\frac{2\mathrm{\π}}{3}-\mathrm{\δ})\end{array}\right.$ (Formula 1)

Among them, M is the proportional coefficient, U _dc is the DC side voltage, and δ is the angle between U _A and U _S , all of which are controllable.

From the schematic diagram of the converter unit in Figure 2, it can be concluded that:

$\left\{\begin{array}{c}{u}_A={\mathrm{Ri}}_a+L\frac{{\mathrm{di}}_a}{\mathrm{dt}}+u_{\mathrm{Sa}}\\ u_{\mathrm{Ab}}={\mathrm{Ri}}_b+L\frac{{\mathrm{di}}_b}{\mathrm{dt}}+u_{\mathrm{Sb}}\\ u_{\mathrm{Ac}}={\mathrm{Ri}}_c+L\frac{{\mathrm{di}}_c}{\mathrm{dt}}+u_{\mathrm{sc}}\end{array}\right.$ (Formula 2)

Substituting formula 1 into formula 2, we can get:

$\left\{\begin{array}{c}L\frac{{\mathrm{di}}_a}{\mathrm{dt}}={\mathrm{MU}}_{\mathrm{dc}}\sin (\mathrm{\ωt}-\mathrm{\δ})-u_{\mathrm{Sa}}-{\mathrm{Ri}}_a\\ L\frac{{\mathrm{di}}_b}{\mathrm{dt}}={\mathrm{MU}}_{\mathrm{dc}}\sin (\mathrm{\ωt}-\frac{2\mathrm{\π}}{3}-\mathrm{\δ})-u_{\mathrm{Sb}}-{\mathrm{Ri}}_b\\ L\frac{{\mathrm{di}}_C}{\mathrm{dt}}={\mathrm{MU}}_{\mathrm{dc}}\sin (\mathrm{\ωt}+\frac{2\mathrm{\π}}{3}-\mathrm{\δ})-u_{\mathrm{sc}}-{\mathrm{Ri}}_C\end{array}\right.$ (Formula 3)

From the energy relationship, the DC side voltage equation can be obtained:

$\frac{d}{\mathrm{dt}}\left(\frac{1}{2}{\mathrm{CU}}_{\mathrm{dc}}^2\right)=-[u_A{i}_a+u_{\mathrm{Ab}}{i}_b+u_{\mathrm{Ac}}{i}_c]$ (Formula 4)

Substituting Equation 1 into Equation 4 and simplifying it can get:

$\frac{U_{\mathrm{dc}}}{\mathrm{dt}}=-\frac{m}{C}[i_a\sin (\mathrm{\ωt}-\mathrm{\δ})+i_b\sin (\mathrm{\ωt}-\frac{2\mathrm{\π}}{3}-\mathrm{\δ})+i_C\sin (\mathrm{\ωt}+\frac{2\mathrm{\π}}{3}-\mathrm{\δ})$ (Formula 5)

Further, the mathematical model of the main circuit unit in the ABC coordinate system can be obtained:

$\left\{\begin{array}{c}L\frac{{\mathrm{di}}_a}{\mathrm{dt}}={\mathrm{MU}}_{\mathrm{dc}}\sin (\mathrm{\ωt}-\mathrm{\δ})-u_{\mathrm{Sa}}-{\mathrm{Ri}}_a\\ L\frac{{\mathrm{di}}_b}{\mathrm{dt}}={\mathrm{MU}}_{\mathrm{dc}}\sin (\mathrm{\ωt}-\frac{2\mathrm{\π}}{3}-\mathrm{\δ})-u_{\mathrm{Sb}}-{\mathrm{Ri}}_b\\ L\frac{{\mathrm{di}}_c}{\mathrm{dt}}={\mathrm{MU}}_{\mathrm{dc}}\sin (\mathrm{\ωt}+\frac{2\mathrm{\π}}{3}-\mathrm{\δ})-u_{\mathrm{sc}}-{\mathrm{Ri}}_c\\ \frac{d{u}_{\mathrm{dc}}}{\mathrm{dt}}=-\frac{m}{C}[i_a\sin (\mathrm{\ωt}-\mathrm{\δ})+i_b\sin (\mathrm{\ωt}-\frac{2\mathrm{\π}}{3}-\mathrm{\δ})+i_c\sin (\mathrm{\ωt}+\frac{2\mathrm{\π}}{3}-\mathrm{\δ})\end{array}\right.$ (Formula 6)

3) Coordinate transformation and active power calculation unit

By analyzing the above formula 6, we can know the changing law of the variables of the converter unit. The coefficients in formula 6 change with time, and it is difficult to analyze and solve it. Therefore, the ABC/dq transformation is applied to convert the coefficients on the ABC coordinate system to Variables are transformed to variables on the rotating coordinate system dq. Assuming that the three phases are balanced, and the direction of the d-axis is consistent with the direction of the microgrid voltage space vector US, the mathematical model after dq coordinate transformation is:

$\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_d\\ i_q\\ u_{\mathrm{dc}}\end{array}\right]=\left[\begin{array}{ccc}-\frac{R}{L}& -\mathrm{\ω}& \frac{m}{L}\sin \mathrm{\δ}\\ -\mathrm{\ω}& -\frac{R}{L}& \frac{m}{L}\cos \mathrm{\δ}\\ -\frac{m}{C}\sin \mathrm{\δ}& -\frac{m}{C}\sin \mathrm{\δ}& 0\end{array}\right]\left[\begin{array}{c}{i}_d\\ i_q\\ u_{\mathrm{dc}}\end{array}\right]+\frac{1}{L}\left[\begin{array}{c}-u_m\\ 0\\ 0\end{array}\right]$ (Formula 7)

Among them, i _d represents the d-axis current in the dq coordinate system (active current feedback of the inner loop current controller), i _q represents the q-axis current in the dq coordinate system (reactive current feedback of the inner loop current controller), U _m represents the phase voltage amplitude of the microgrid.

Since Equation 7 is a constant coefficient differential equation system, it is convenient to analyze and solve the coordinate transformation and each variable of the active power calculation unit. After the dq transformation, the equivalent voltage of the unit is a DC voltage, which is:

$\left\{\begin{array}{c}{v}_d=m\sin \mathrm{\δ}\\ v_q=m\cos \mathrm{\δ}\end{array}\right.$ (Formula 8)

Therefore, the relationship between the voltage and current of the unit on the dq coordinate axis is:

$L\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_d\\ i_q\end{array}\right]=\left[\begin{array}{cc}-R& \mathrm{\ωL}\\ -\mathrm{\ωL}& -R\end{array}\right]\left[\begin{array}{c}{i}_q\\ i_q\end{array}\right]+\left[\begin{array}{c}{v}_d-u_m\\ v_q\end{array}\right]$ (Formula 9)

According to the instantaneous power theory, the active power P output by the unit can be obtained as:

$P=\frac{3}{2}(u_{\mathrm{SD}}{i}_d+u_{\mathrm{Sq}}{i}_q)=\frac{3}{2}{u}_m{i}_d$ (Formula 10)

Therefore, the unit outputs the d-axis current id as the active current feedback of the inner loop current controller _, outputs the q-axis current i _q as the reactive current feedback of the inner loop current controller, and outputs the active power P as the outer loop power Active power feedback for the controller.

4) Adaptive limiter

When the microgrid voltage fluctuates, in order to realize the rapid recovery of the transient voltage support capability and reduce the constraint of the conventional control method on the output reference current limit value of the power outer loop controller, an adaptive limiter is proposed. As shown in Figure 3, the adaptive limiter can dynamically adjust the limit value of the active reference current according to the reactive reference current output by the power outer loop controller when the microgrid voltage fluctuates or even fails, so that the output has no The work reference current is maximized, and ultimately the stability of the microgrid voltage can be restored more quickly.

As shown in Figure 3, the adaptive limiter may include: an active current limiting circuit, a reactive current limiting circuit, a first square processing circuit, a second square processing circuit, a first accumulation circuit, a square root processing circuit, A minimum value circuit, wherein: the input terminal of the active current limiting circuit is connected to the active current reference value output terminal of the power controller, and the output terminal of the active current limiting circuit is connected to the first input terminal of the minimum value circuit; The input end of the current limiting circuit is connected with the reactive current reference value output end of the voltage controller, the output end of the reactive current limiting circuit is the reactive power reference current output end of the adaptive limiter; the first square processing circuit The input is the reference current limit value output by the converter unit, the output terminal of the first square processing circuit is connected with the positive value input terminal of the first accumulation circuit; the input terminal of the second square processing circuit is connected with the reactive current reference of the voltage controller The value output end is connected, the output end of the second square processing circuit is connected with the negative value input end of the first accumulation circuit; the output end of the first accumulation circuit is connected with the input end of the square root processing circuit, and the output end of the square root processing circuit is connected with the The second output end of the minimum value seeking circuit is connected; the output end of the minimum value seeking circuit is the active reference current output end of the adaptive limiter.

In order to prevent system overcurrent, the current reference value is usually limited in the outer loop power controller. The maximum current output by the converter is generally 1.5 times the rated current, that is, the limiting condition of the current reference value output by the converter is:

$i_{\lim }^{*}=1.5i_e$ (Formula 11)

in, Indicates the reference current limit value output by the converter, i _e represents the rated value of the AC current on the microgrid side, and the reference current limit value Includes active reference current limit value and reactive reference current limit value The relationship between the two satisfies:

$i_{\lim }^{*}=\sqrt{i_{\mathrm{d\; lim}}^{*2}+i_{\mathrm{qlim}}^{*2}}$ (Formula 12)

The working principle of the adaptive limiter is shown in Figure 3, and it can be drawn from Figure 3 that and The output range is:

$i_q^{*}=\left\{\begin{array}{cc}{i}_{q1}^{*},& -i_{\lim }^{*}<i_{q1}^{*}<i_{\lim }^{*}\\ i_{\lim }^{*},& i_{q1}^{*}\&Greater\; Equal;i_{\lim }^{*}\\ -i_{\lim }^{*},& i_{q1}^{*}\&le;-i_{\lim }^{*}\end{array}\right.$ (Formula 13)

$i_d^{*}=\left\{\begin{array}{cc}{i}_{d1}^{*},& i_{\mathrm{dlim}}^{*}<i_{d1}^{*}\&le;\sqrt{i_{\lim }^{*2}-i_{q1}^{*2}}\\ \sqrt{i_{\lim }^{*2}-i_{q1}^{*2}},& \sqrt{i_{\lim }^{*2}-i_{q1}^{*2}}<i_{d1}^{*}<i_{\lim }^{*}\\ i_{\lim }^{*},& i_{d1}^{*}\&Greater\; Equal;i_{\lim }^{*}\\ i_{\mathrm{dlim}}^{*},& i_{d1}^{*}\&le;i_{\mathrm{dlim}}^{*}\end{array}\right.$ (Formula 14)

From the above formula 13 and formula 14, it can be seen that in the case of the voltage drop of the microgrid, the reference current track output by the adaptive limiter is shown in Fig. 4 . At the initial operating point D, the reference current output by the adaptive limiter is the same as that output by the outer loop controller, which is and When the microgrid voltage drops slightly, the reference current output by the outer loop controller is still within the semicircle in Figure 4, and the system will reach a new stable operating point M, but when the microgrid voltage drops sharply, it will cause the outer loop control The active and reactive reference currents output by the device increase significantly. When the reference current increased to its limiting condition , according to Equation 13 and Equation 14, it can be obtained that the active reference current output by the adaptive limiter becomes Therefore, the reference current trajectory reaches point A and can rotate clockwise along the semicircle of the current control range, as shown in Figure 4. According to the degree of voltage drop of the microgrid, the reference current vector may reach point B and run stably, or continue to rotate to point C. When the reference current vector moves to point C, at this time Converter output power factor angle for Therefore, the converter only outputs reactive power.

As shown in Figure 5, it is the power curve output by the converter when the microgrid voltage drops. Assuming that the system starts to run stably at point Z, the microgrid voltage drops suddenly, making the operating point change to point F in Figure 5. When the conventional control method is adopted, the reactive reference current output by the outer loop controller is limited, and its output reactive reference current The maximum value is After the transient state, the system runs stably at point M, and the microgrid voltage at this time is U ₁ . After adopting the adaptive limiter, the reactive power reference current output can be directly maximized After the transient state, the system will transition to stable operation at point N, at which point the microgrid voltage is U ₂ . As shown in Figure 5, the adaptive limiter can increase the reactive power output capability of the converter, which is more beneficial to the recovery of the microgrid voltage and is superior to conventional control methods.

5) Current controller and PWM generator

The current controller mainly adjusts the active current and reactive current. The purpose of the current inner loop control is to make the output current i _d and i _q of the main circuit unit track their reference values, so that the microgrid voltage U _S can be stabilized at a desired constant value, and output PWM control signal. It can be seen from formula 9 that i _d and i _q can be controlled and adjusted by v _d and v _q , but there is coupling between the voltage and current of the converter between the d axis and the q axis, and the change of i _d will cause v q and v _q i _q changes accordingly, and vice versa. Coupled loops cannot be separated for independent analysis, so decoupling is required. The feedforward compensation items ωLi _d and ωLi _q are added to the output value of the PI controller of the current inner loop. The specific control block diagram is shown in Figure 6.

The transfer function of the converter output voltage in Figure 6 is:

$\left\{\begin{array}{c}{v}_d=(K_P+\frac{K_I}{\mathrm{the\; s}})(i_d^{*}-i_d)-\mathrm{\&omega;}{\mathrm{Li}}_q+u_m\\ v_q=(K_P+\frac{K_I}{\mathrm{the\; s}})(i_q^{*}-i_q)+\mathrm{\&omega;}{\mathrm{Li}}_d\end{array}\right.$ (Formula 15)

Among them, K _P and K _I are the proportional coefficient and the integral coefficient of the PI controller respectively. Putting Equation 15 into Equation 9, we can get:

$L\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_d\\ i_q\end{array}\right]=\left[\begin{array}{cc}R+K_P+\frac{K_I}{\mathrm{the\; s}}& 0\\ 0& R+K_P+\frac{K_I}{\mathrm{the\; s}}\end{array}\right]\left[\begin{array}{c}{i}_d\\ i_q\end{array}\right]+(K_P+\frac{K_I}{\mathrm{the\; s}})\left[\begin{array}{c}{i}_d^{*}\\ i_q^{*}\end{array}\right]$ (Formula 16)

Among them, the off-diagonal elements are 0. It can be seen that after adding feed-forward compensation to the PI output of the current inner loop, the d and q axis variables realize decoupling control, and the current controller finally outputs v _d and v _q to PWM generator, the PWM generator receives the control signals v _d and v _q output by the current controller, and generates PWM waveform after PWM modulation.

The PWM generator is not only used to generate PWM modulation waveforms, but also used to interlock, electrically isolate and amplify the two driving signals on the same bridge arm of the main circuit, so as to ensure that the output fundamental frequency and voltage amplitude are the same as those of the microgrid .

6) Voltage controller and power controller

Both the voltage controller and the power controller are outer-loop controllers, which can also be called active power controllers and voltage controllers. Both the power controller and the voltage controller are equipped with PI (proportional-integral) regulators for Perform PI adjustments.

Among them, the active power controller, through PI adjustment, outputs the given value of active current Adjust the output active power of the converter, compare the given value of active power with the output active power value of the converter, and then adjust through PI to generate the d-axis current reference value To stabilize the active power voltage output by the converter. satisfy:

$i_{d1}^{*}=(K_{\mathrm{dP}}+\frac{K_{\mathrm{iGO}}}{\mathrm{the\; s}})(P^{*}-P)$ (Formula 17)

Among them, K _dP and K _dI are the proportional coefficient and integral coefficient of the d-axis PI controller, respectively.

Voltage controller, through PI regulation, outputs a given value of reactive current Adjust the output reactive power of the converter, and then adjust the fluctuation of the microgrid voltage. The microgrid voltage perturbation control link is through the microgrid voltage U _S and its reference value comparison, resulting in a q-axis current reference value To control the microgrid voltage and prevent microgrid voltage perturbation, where, Need to meet:

$i_{q1}^{*}=(K_{\mathrm{QUR}}+\frac{K_{\mathrm{QI}}}{\mathrm{the\; s}})(u_S^{*}-u_S)$ (Formula 18)

Among them, K _qP and K _qI are the proportional coefficient and integral coefficient of the q-axis PI controller, respectively.

That is, the PI regulator set in the power controller can input the active power output by the converter into the microgrid according to the power setting value to be compensated, so as to maintain the active power balance in the microgrid. The PI regulator can input the reactive power output by the converter into the microgrid according to the voltage perturbation setting value that needs to be compensated, so as to keep the voltage in the microgrid stable.

In this example, when the voltage in the microgrid fluctuates frequently, the voltage of the microgrid is detected by the voltage transformer, and the effective value and amplitude of the voltage are calculated to form the control of the voltage fluctuation of the microgrid. Detect the output current of the converter through the current transformer, and then use the ABC/dq coordinate transformation to convert the three-phase current into a DC variable that rotates synchronously at the fundamental frequency of the microgrid, and the active power obtained by the outer loop voltage/power controller It is compared with the reference current of reactive power, and then through the optimization of the adaptive limiter, the reference value of reactive current is output to the maximum extent, and the current reference value of corresponding active power is obtained at the same time, and then the two currents are obtained through the inner loop current control The phase voltage, through the PWM generator, controls the power electronics main circuit to output the corresponding AC voltage, and the DC side voltage of the power electronics main circuit is the voltage output by the large-scale energy storage device. Through the energy conversion in the large-scale energy storage device, the amount of reactive power compensation to the micro-grid is regulated, thereby stabilizing the voltage of the micro-grid.

The following is a simulation example of microgrid voltage perturbation control to illustrate the function and effect of the above microgrid voltage perturbation control system. Figure 7 shows the overall architecture of the control system. The microgrid structure diagram of the perturbation device. When the fan in Figure 8 is suddenly incorporated into the microgrid or a load is short-circuited, it will cause fluctuations in the microgrid voltage. In this example, the simulated AC power supply uses a three-phase AC programmable power supply model, and the line voltage is set to 0.4kV and the frequency is 50Hz. During the simulation, the microgrid voltage fluctuates: it rises to 1.06 times the rated value at 0.2s, decreases to 0.94 times the rated value at 0.3s, and returns to the rated value at 0.4s. The specific simulation results are shown in Figure 9 To 14, where the abscissa represents the time, the unit is s, and the ordinate represents the increase multiple relative to the rated value.

Among them, Figure 9 and Figure 10 are the phase voltage waveform and phase current waveform corresponding to the output of the voltage perturbation device when the grid voltage fluctuates. It can be seen from Figure 10 that the voltage perturbation device consumes neither active power nor Reactive power and current are basically zero. When the microgrid voltage fluctuates, the voltage perturbation device can quickly generate reactive current. Before and after 0.3s, the reactive current flow direction changes, and the current phase can transition quickly and smoothly , the impact is small.

Figure 11 and Figure 12 show the grid voltage amplitude waveforms before and after compensation. It can be seen from Figure 12 that the change range of the voltage amplitude after compensation is significantly lower than that before compensation, and the rated voltage can be basically maintained after compensation. Change. Figures 13 and 14 show the active power and reactive power of the voltage perturbation device. The active power reduces the active power output under the action of the adaptive limiter when the reactive power changes suddenly, thereby maximizing the output reactive power. When the grid voltage After the fluctuation occurs, the voltage perturbation device responds quickly to generate corresponding reactive power, so that the voltage fluctuation of the microgrid can quickly recover to the rated value.

As shown in Figure 15 is the working principle diagram of the voltage perturbation system. The system uses the TMS320F28335 digital signal processor as the core control unit, and has an A/D sampling module, a main program module, a serial communication module, and a PWM generation module. At the same time, the sampling and conditioning circuit converts the three-phase voltage and current analog signals in the microgrid into digital signals acceptable to DSP (Digital Signal Process, digital signal processing), and then sends them to the I/O pins of the DSP , DSP samples, filters, and corrects the input signal to obtain the value corresponding to the analog signal. The system control program calculates the corresponding control amount and outputs it according to the sampling result and the control method. FPGA (Field-Programmable Gate Array, Field Programmable Gate Array) generates a PWM pulse signal after receiving the output of the outer loop control and inner loop controller, and then controls the output of the drive circuit, so that the main circuit outputs and controls the output of the microgrid. The voltage fluctuation of the microgrid can be stabilized. Specifically, AD7656 can be used for A/D, TMS320F28335 can be used for DSP, IS61LV51216-12T can be used for RAM, XC6SLX45-3CSG324I can be used for FPGA, and SKYPER32 can be used for PWM.

In this example, the microgrid voltage perturbation control method based on the above-mentioned voltage perturbation system can be shown in Figure 16, including the following steps:

Step 1601: Detect the three-phase current output by the converter unit;

Step 1602: converting the three-phase current into a DC variable synchronously rotating at the fundamental frequency of the microgrid;

Step 1603: Obtain the active current reference value output by the power controller, and the reactive power reference value output by the voltage controller;

Step 1604: Compare the DC variable with the active current reference value and the reactive power reference value to obtain a comparison result;

Step 1605: optimize the comparison result through an adaptive limiter, and output the active reference current and the reactive reference current to the maximum;

Step 1606: through the current controller, control the active reference current and the reactive reference current output by the adaptive limiter to the maximum to obtain a two-phase voltage control signal;

Step 1607: Perform PWM modulation on the two-phase voltage control signal to obtain a PWM waveform, and input the PWM waveform into the converter unit.

During specific implementation, in the above step 1605, optimization can be performed according to the following limiting conditions:

$\sqrt{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; dlim</span>}}^{<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; qlim</span>}}^{<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1.5</span>}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}$

in, Indicates the active reference current limit value, Indicates the reactive power reference current limit value, the reactive power reference current output by the adaptive limiter to the maximum, ie indicates the rated value of the AC current on the microgrid side;

The maximum output active reference current and reactive reference current are:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; ,</span>& {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; dlim</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; \&le;</span>\sqrt{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; lim</span>}}^{<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 2</span>}}}\\ \sqrt{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; lim</span>}}^{<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; ,</span>& \sqrt{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; lim</span>}}^{<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; lim</span>}}^{<span\; class="notranslate">\; *</span>}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; lim</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; ,</span>& {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; \&Greater\; Equal;</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; lim</span>}}^{<span\; class="notranslate">\; *</span>}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; dlim</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; ,</span>& {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; \&le;</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; dlim</span>}}^{<span\; class="notranslate">\; *</span>}\end{array}\right.$

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; ,</span>& <span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; lim</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; lim</span>}}^{<span\; class="notranslate">\; *</span>}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; lim</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; ,</span>& {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; \&Greater\; Equal;</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; lim</span>}}^{<span\; class="notranslate">\; *</span>}\\ <span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; lim</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; ,</span>& {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; \&le;</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; lim</span>}}^{<span\; class="notranslate">\; *</span>}\end{array}\right.$

in, Indicates the active current reference value output by the power controller, Indicates the reactive power reference value output by the voltage controller.

The DC variable synchronously rotating at the fundamental frequency of the microgrid in the above step 1602 may include: active current feedback, reactive current feedback and active power, specifically, the maximum output of the adaptive limiter through the current controller The active reference current and reactive reference current are controlled to obtain two-phase voltage control signals, which can include:

The two-phase voltage control signal is obtained according to the following transfer function:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}{\mathrm{<span\; class="notranslate">\; Li</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}\\ {\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}{\mathrm{<span\; class="notranslate">\; Li</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}\end{array}\right.$

Among them, v _d and v _q represent the two-phase voltage control signals, K _P represents the proportional coefficient of the PI controller, K _I represents the integral coefficient of the PI controller, i _d represents the active current feedback, i _q represents the reactive current feedback, L Represents the inductance value of the inductor, ω represents the angular frequency of the microgrid voltage, U _m represents the amplitude of the phase voltage of the microgrid, and s represents the complex variable.

In the above-mentioned embodiments, it is just considering that in the existing micro-grids formed by wind power and solar power, frequent voltage fluctuations (that is, voltage perturbation) often occur so that the micro-grids cannot operate independently, and at the same time cannot be incorporated into In order to operate in a large power grid, it is proposed to add a large-scale energy storage device to the micro-grid to form an integration of wind, wind and storage. Through the voltage perturbation device and control method, the energy in the large-scale energy storage device is adjusted according to the voltage fluctuation margin in the micro-grid. The degree and frequency are converted into the reactive energy required in the microgrid in real time, so as to ensure the stable voltage and safe and reliable operation of the microgrid. Furthermore, an adaptive limiter is embedded in the power electronic device to form a micro-grid voltage perturbation control device. The adaptive limiter can generate voltage fluctuations in the micro-grid, and even voltage drops during faults. With the support of large-scale energy storage devices, the limit value of the active reference current is dynamically adjusted according to the reactive reference current output by the power outer loop controller, so as to maximize the output reactive reference current and ultimately restore the grid-side voltage more quickly The stability of the system can effectively control the voltage perturbation in the microgrid.

From the above description, it can be seen that the embodiment of the utility model achieves the following technical effects: a microgrid voltage perturbation control system is provided, and when the voltage in the microgrid fluctuates frequently, by detecting the voltage in the microgrid and current, the voltage control perturbation device is used to convert the energy in the large-scale energy storage unit into the reactive current in the stable microgrid, so that the transient voltage can return to the normal level, and at the same time, by adding an adaptive limiter, the The voltage of the micro-grid can be stabilized at a normal level more quickly when fluctuating in a large range, thereby ensuring the safe and reliable operation of the micro-grid. The technical problems of the micro-grid have been effectively suppressed and the technical effect of ensuring stable voltage operation has been achieved.

The above descriptions are only preferred embodiments of the present utility model, and are not intended to limit the present utility model. For those skilled in the art, various modifications and changes may be made to the embodiments of the present utility model. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present utility model shall be included in the protection scope of the present utility model.

Claims (6)

1. A microgrid voltage perturbation control system, comprising: the device comprises an energy storage unit, a converter unit, a coordinate conversion and active power calculation unit, a power controller, a voltage controller, a self-adaptive amplitude limiter, a current controller and a PWM generator;

the energy storage unit is used for supplying power to the micro-grid;

the converter unit is connected with the output end of the energy storage unit and used for adjusting the output current of the energy storage unit to meet the reactive current requirement of the microgrid;

the input end of the coordinate transformation and active power calculation unit is connected with the output end of the converter unit, and is used for converting variables on an ABC coordinate system output by the converter unit into variables on a rotating coordinate system dq, wherein the output end of the coordinate transformation and active power calculation unit comprises: an active current feedback output terminal, a reactive current feedback output terminal and an active power output terminal;

the input end of the power controller is connected with the active power reference value and is connected with the active power output end of the coordinate transformation and active power calculation unit, and the output end of the power controller comprises: an active current reference value output end;

the input end of the voltage controller is connected with the microgrid voltage and the microgrid voltage reference value, and the output end of the voltage controller comprises: a reactive current reference value output end;

the input end of the self-adaptive amplitude limiter is connected with the active current reference value output end of the power controller and the reactive current reference value output end of the voltage controller, and the self-adaptive amplitude limiter is used for carrying out amplitude limiting on the active current reference value output by the power controller and the reactive current reference value output by the voltage controller and outputting active reference current and reactive reference current;

the input end of the current controller is connected with the output end of the adaptive amplitude limiter, and is connected with the active current feedback output end and the reactive current feedback output end of the coordinate transformation and active power calculation unit, so that the active current and the reactive current of the microgrid can be regulated, the active current and the reactive current can track the active reference current and the reactive reference current, and the output end of the current controller outputs a voltage control signal;

and the PWM generator is connected with the output end of the current controller and used for carrying out PWM modulation on the voltage control signal to generate a PWM waveform, and the PWM waveform is input into the converter unit.

2. The microgrid voltage perturbation control system of claim 1, wherein the adaptive limiter comprises: active current amplitude limiting circuit, idle current amplitude limiting circuit, first square processing circuit, second square processing circuit, accumulation circuit, square processing circuit, the minimum circuit of asking, wherein:

the input end of the active current amplitude limiting circuit is connected with the active current reference value output end of the power controller, and the output end of the active current amplitude limiting circuit is connected with the first input end of the minimum value calculating circuit;

the input end of the reactive current amplitude limiting circuit is connected with the reactive current reference value output end of the voltage controller, and the output end of the reactive current amplitude limiting circuit is the reactive reference current output end of the self-adaptive amplitude limiter;

the input of the first square processing circuit is a reference current amplitude limiting value output by the converter unit, and the output end of the first square processing circuit is connected with the positive value input end of the accumulation circuit;

the input end of the second square processing circuit is connected with the reactive current reference value output end of the voltage controller, and the output end of the second square processing circuit is connected with the negative value input end of the accumulation circuit;

the output end of the accumulation circuit is connected with the input end of the squaring processing circuit, and the output end of the squaring processing circuit is connected with the second output end of the minimum value calculating circuit;

and the output end of the minimum value calculating circuit is the active reference current output end of the self-adaptive amplitude limiter.

3. The microgrid voltage perturbation control system of claim 1 wherein the converter unit comprises:

the three-phase converter is used for converting the energy of the energy storage unit into energy required to be compensated during the perturbation of the voltage of the microgrid;

and the filtering reactance is connected with the three-phase converter and is used for filtering out higher harmonics generated when the direct current power in the energy storage unit is converted into the alternating current reactive power of the micro-grid.

4. The microgrid voltage perturbation control system of claim 3 wherein the three-phase inverter comprises: for converting the dc power into the ac power under the PWM control.

5. The microgrid voltage perturbation control system of claim 3, wherein:

the power controller is internally provided with a first PI regulator, and the first PI regulator is used for inputting a power set value required to be compensated by active power output by the three-phase converter into the microgrid;

and a second PI regulator is arranged in the voltage controller and used for inputting a voltage perturbation set value required by reactive power output by the three-phase converter and compensated into the microgrid.

6. The microgrid voltage perturbation control system of claim 1 wherein the PWM generator is further configured to interlock, electrically isolate and power amplify two drive signals on the same leg of the main circuit.