CN201623500U - A small wind power grid-connected system with battery - Google Patents

Abstract

The utility model discloses a small-scale wind power generation grid-connected system with accumulators, which comprises a wind turbine, a wind generator, a rectifier circuit, an inverter circuit, a battery pack, a charging circuit, a discharging circuit, a charging controller and a discharging controller. The battery pack is connected to the DC bus through a charging circuit and a discharging circuit, the charging controller is connected to the charging circuit, and the discharging controller is connected to the discharging circuit. The system adds the energy storage link-battery pack to the original small wind power grid-connected system, and adds charge controllers, discharge controllers, etc. to control and set the battery pack reasonably, so that the power generated by the small wind power grid-connected system can be When power is in short supply, it can be supplied to the grid or stored according to load conditions, thereby improving the power utilization rate of small wind power generation systems, broadening its application, and bringing greater economic benefits to users.

Description

A small wind power grid-connected system with battery

technical field

The utility model relates to the field of wind power generation, in particular to a small wind power generation grid-connected system with accumulators.

Background technique

In recent years, the production and promotion of household small wind turbines (50W ~ 1000W) in my country have made great progress. As of 1997, the number of household small-scale wind power generators promoted and applied nationwide has exceeded 136,000 units, with a total installed capacity of 16.5MW, which has solved the electricity consumption problems of more than 130,000 households for lighting, watching TV, and listening to the radio. At present, domestic small wind turbines can be divided into horizontal axis and vertical axis according to the form of wind turbines. No matter which form it is, it mainly transmits electric energy directly to the grid through inverter control, and there is no energy storage device in the intermediate link. This type of system can only convert wind energy and electric energy according to external conditions, and does not make reasonable planning and coordination for the energy generated by wind turbines, so as to improve the utilization rate of electric energy. Therefore, the current domestic small-scale wind power generation system basically has no energy storage link, that is, no battery equipment.

Utility model content

In order to solve the above problems, the utility model provides a small wind power grid-connected system with an energy storage link that can bring good economic benefits.

The technical scheme that the utility model adopts for solving its problem is:

A small wind power grid-connected system with batteries, including:

Wind turbines and wind generators driven by wind turbines;

A rectifier circuit, the input end of which is connected to the output end of the wind power generator;

An inverter circuit, the input end of which is connected to the output end of the rectification circuit through the DC bus, and the output end is connected to the power grid and/or the load;

Also includes:

A battery pack, a charging circuit, a discharging circuit, a charging controller and a discharging controller, the battery pack is respectively connected to the DC bus through the charging circuit and the discharging circuit, the charging controller is connected to the charging circuit, and the discharging controller is connected to the discharging circuit connection.

Preferably, the charging controller is a fuzzy sliding mode charging controller, and the input terminal of the fuzzy sliding mode charger receives a comparison signal between the charging voltage detection value and the charging voltage reference value and the charging current detection value of the battery pack The comparison signal with the charging current reference value, the output terminal is connected with the charging circuit.

Preferably, the discharge controller is a fuzzy sliding mode discharge controller, the input terminal of the fuzzy sliding mode discharge controller receives a comparison signal between the bus voltage detection value of the DC bus and the bus voltage reference value, and the output terminal is connected to discharge circuit connection.

The beneficial effects of the utility model are: the system adds an energy storage link-battery pack to the original small-scale wind power generation grid-connected system, and adds a charge controller, a discharge controller, etc. to control and set the battery pack reasonably, so that the small wind power The power generated by the grid-connected power generation system can be supplied to the grid when power is in short supply or stored according to load conditions, thereby improving the power utilization rate of small wind power generation systems, broadening its application, and bringing greater economic benefits to users.

Description of drawings

Below in conjunction with accompanying drawing and embodiment the utility model is further described:

Fig. 1 is the block diagram of circuit principle of the utility model.

Detailed ways

Referring to Fig. 1, a small wind power grid-connected system with batteries of the present invention includes:

Wind turbines and wind turbines driven by wind turbines. Wind turbines can use horizontal or vertical axis wind turbines to capture wind energy and convert it into mechanical energy. Wind turbines can use permanent magnet synchronous generators. It is used to convert mechanical energy into AC electrical energy whose frequency changes with wind speed;

The rectifier circuit, whose input terminal is connected to the output terminal of the wind turbine, can adopt a three-phase uncontrollable rectifier circuit. In order to provide more stable and high-efficiency direct current, the back end of the three-phase uncontrollable rectifier circuit can also be connected with a DC/DC Transformation circuits, such as BOOST circuits, etc., three-phase uncontrollable rectification circuits convert AC power with unstable frequency into DC power, and send it to the low-voltage side of the BOOST circuit. The BOOST circuit converts low-voltage and unstable DC power into stable high-voltage power. And sent to the DC bus;

An inverter circuit, the input end of which is connected to the output end of the rectifier circuit through the DC bus, and the output end is connected to the power grid and/or the load, and the inverter circuit reconverts the DC voltage on the DC bus into a stable AC power suitable for use by the load and the power grid;

A battery pack, a charging circuit, a discharging circuit, a charging controller and a discharging controller, the battery pack is respectively connected to the DC bus through the charging circuit and the discharging circuit, the charging controller is connected to the charging circuit, and the discharging controller is connected to the discharging circuit connection.

When the DC energy on the DC bus is supplied to the battery pack, grid and/or load, it is generally executed in the following order of priority: When the power generated by the wind turbine is greater than the power required by the load, and the DC bus is stable at the required voltage condition, the DC The busbar charges the battery pack through the charging circuit; when the power generated by the wind turbine generator is less than the power required by the load and the battery pack has power reserves, the battery pack provides energy to the DC bus through the discharge circuit, and the electric energy stored in the battery pack is transmitted to the load and the grid .

In order to better control the charging of the storage battery pack, the charging controller implements a two-stage charging control of the storage battery pack, which is firstly charged with a constant current and then charged with a constant voltage. That is, when the battery pack needs to be charged, the charging current of the battery pack remains constant, and the battery pack maintains a constant current charging state until the terminal voltage rises to the switching voltage value between the two stages; when the battery pack terminal voltage rises to the switching voltage value When the voltage value is lower, the battery pack is charged at a constant charging voltage at a constant voltage until the charging current of the battery pack is reduced to a certain value to complete the charging process. In order to be able to use the above-mentioned control strategy for control, the utility model preferably adopts a fuzzy sliding mode charge controller, and the input terminal of the fuzzy sliding mode charger receives the comparison signal between the charging voltage detection value and the charging voltage reference value and the battery pack The comparison signal between the charging current detection value and the charging current reference value, the output terminal is connected to the charging circuit. The theory of fuzzy sliding mode control is described below.

(1) Sliding mode variable structure system

The sliding mode of the sliding mode variable structure is completely self-adaptive, which is the most prominent advantage of the sliding mode variable structure system, and it is also the main reason for its attention. In any actual system, there are some uncertain parameters, changing parameters, mathematical description is always inaccurate, and is disturbed by the external environment, so a simple general linear model is established, but a perturbed system . For perturbations, it can be complex: include many terms, develop mathematical expressions, even be uncertain, etc. However, since the variable structure control can be constructed, such a perturbation has no effect on the sliding mode at all, even though the sliding mode is fully adaptive to the perturbation. In this way, we can solve very complex system stabilization problems.

Sliding mode control is to switch the control amount back and forth uninterruptedly, so that the system is always constrained on the switching surface, and then the state of the system automatically slides to the origin, which is an essential problem. Now assume that the control system equation of a research object is:

x=f(x, u, t) (Formula 1)

x∈R ⁿ is the state quantity of the system, u∈R ^m is the control quantity of the system, and t∈R.

It is necessary to determine the switching function s(x), s∈R ^m (the dimension of which is generally equal to the dimension of the control variable)

$\mathrm{the\; s}\left(x\right)=\mathrm{cx}=\underset{i=1}{\overset{\mathrm{no}}{\mathrm{\Σ}}}{c}_i{x}_i$ (Formula 2)

and seek variable structure control:

(公式3)

(Formula 3)

使得满足下面3种情况：A、滑动模态存在，即满足公式3；B、满足可达性条件，就是在切换面s(x)＝0以外的运动点都将于有限的时间内到达切面；C、保证滑模运动的稳定性系统运动进入滑动模态区后，就开始沿滑模面运动。对通常的反馈控制系统而言，除了滑模的存在性和可达性以外，还要求系统的滑动模态是渐进稳定的且具有良好的动态品质。Sliding mode variable structure embodiment

So that the following three conditions are satisfied: A. The sliding mode exists, that is, formula 3 is satisfied; B. The accessibility condition is satisfied, that is, all moving points other than s(x)=0 on the switching surface will reach the cutting surface within a limited time ; C. Guarantee the stability of the sliding mode motion. After the system moves into the sliding mode area, it starts to move along the sliding mode surface. For the usual feedback control system, in addition to the existence and accessibility of the sliding mode, the sliding mode of the system is also required to be asymptotically stable and have good dynamic quality.

(2) Fuzzy control

Fuzzy theory is based on fuzzy sets and fuzzy logic, through the concept of membership function to describe the transition process between "belonging" and "not belonging", so that each element is not only "0" or "1" Belongs to a certain set, and also belongs to a certain set to a certain degree between "0" and "1", each element belongs to a certain set more or less. Fuzzy set is a whole with some characteristic factors to a certain extent, so fuzzy set theory breaks the O-1 boundary of distinct set, and provides a new mathematical tool for describing fuzzy information and dealing with fuzzy phenomena. Fuzzy control is based on fuzzy set theory, uses fuzzy language variables and logical reasoning as tools, and can use human experience and knowledge to incorporate intuitive reasoning into decision-making. The basic concept and algorithm of fuzzy mathematics used in fuzzy control are as follows: Let U be a collection of some objects, called domain of discourse (it can be continuous or discrete). u represents an element of U, which is written as U={u}.

Any mapping u _F from domain U to [0, 1] interval, that is, u _F : U → [0, 1], all determine a fuzzy subset F of U, and μ _F is called the membership function of F (Membership Funetion) Or membership (Grade of Membership), that is, μ _F indicates the degree or level that u belongs to the fuzzy subset F. In the domain of discourse U, the fuzzy subset can be expressed as an ordinal set of element u and its membership function μ _F (u), which is denoted as: F={u, μ _F (u)|u∈U}. If U is continuous, then the fuzzy set F can be written as:

$f={\∫}_J\frac{{\mathrm{\μ}}_f\left(u\right)}{u}\mathrm{du}$ (Formula 4)

If F is discrete, the fuzzy set F can be written as

$f=\frac{{\mathrm{\μ}}_f\left(u_1\right)}{u_1}+\frac{{\mathrm{\μ}}_f\left(u_2\right)}{u_2}+...+\frac{{\mathrm{\μ}}_f\left(u_{\mathrm{no}}\right)}{u_{\mathrm{no}}}=\underset{i=1}{\overset{\mathrm{no}}{\mathrm{\Σ}}}\frac{{\mathrm{\μ}}_f\left(u_i\right)}{u_i},i=\mathrm{1,2},...\mathrm{no}$ (Formula 5)

(3) The principle of two-stage charging control

First, according to the equivalent state equation listed in formula 1 of the charging main circuit, and then design the switching plane according to the above principles, and obtain the equivalent control u _eq by the equivalent control method of the sliding mode equation, and then according to the sliding mode arrival condition Design the switching control u _s to complete the design process of the sliding mode controller.

According to the design principle of sliding mode controller, it is composed of equivalent control and switching control, and the control rule is: if s is non-zero then u is u _eq +u _s . Therefore, the fuzzy controller design also has these two parts, which can be designed as: u=u _eq +u _NZ (s)u _s .

Fuzzy controller input s and output u, through the membership function. The change of u _NZ (s) realizes the elimination of chattering. According to artificial thinking and expert knowledge reasoning, the knowledge base is established as:

The fuzzy subset of s is {NB, NM, NS, ZO, PS, PM, PB}

u two fuzzy subsets are {NB, NM, NS, ZO, PS, PM, PB}

When the system state trajectory is far away from the switching function s, u _NZ should be large to speed up the response speed. When the system state trajectory is close to the switching function s, u _NZ should be small. When the system trajectory reaches the switching function s, u _NZ = 0, so the inference The rules are:

s NB N M NS ZO P.S. PM PB u _NZ PB PM PS ZO PS PM PB

Table 1

Based on the fuzzy sliding mode discharge controller established above, the two-stage charging control of the storage battery is realized. That is, when the battery pack needs to be charged, the fuzzy sliding mode controller controls the charging circuit according to the comparison signal between the charging current detection value of the battery pack and the charging current reference value, so as to keep the charging current of the battery pack constant, and the battery pack The battery pack maintains a constant current charging state until the terminal voltage rises to the switching voltage value between the two stages; The comparison signal between the charging voltage reference values controls the charging circuit so that the battery pack is charged at a constant charging voltage at a constant voltage until the charging current of the battery pack is reduced to a certain value to complete the charging process. The constant charging voltage when the battery pack is charged at a constant voltage is generally preferably selected to be equal to the switching voltage value between the two stages.

In this grid-connected system, the battery pack is directly connected to the DC bus through the discharge circuit. Because the voltage of the DC bus needs to be stable, it is necessary to control the DC bus while the battery pack is discharging. According to the analysis of the principle of energy conservation, assuming that the load is fixed (in practical applications, the load is basically constant or changes in stages, and can be maintained for a long time), it is only necessary to control the DC bus voltage to be stable, then the discharge current of the battery pack is constant. of. Therefore, the preferred control strategy of the discharge controller in this system is to ensure that the DC bus remains stable when the battery pack is discharging. The above control strategy can also be completed by fuzzy sliding mode control, that is, the discharge controller is designed as a fuzzy sliding mode discharge controller. The comparison signal, the output terminal is connected with the discharge circuit. The design of this fuzzy sliding mode discharge controller is basically the same as that of the fuzzy sliding mode charge controller, so it will not be repeated here.

When the battery pack is discharging, the fuzzy sliding mode discharge controller controls the opening and closing of the switching device of the discharge circuit according to the comparison signal between the bus voltage detection value of the DC bus and the bus voltage reference value, and quickly adjusts according to the load change To ensure that the DC bus voltage is stable within the allowable error range of the ideal value, and then keep the discharge current of the battery pack constant, and realize the constant current discharge control of the battery pack.

The energy generated by the small-scale wind power grid-connected system of the utility model can be supplied to the power grid when the power is in short supply or store the power according to the load, especially at night when the power consumption of the power grid is not large, and the power required by the load is less than that of the wind power generation system Under the condition of the generated power, the storage battery is used to store energy, and when the power consumption increases during the day, it supplies power to the grid and loads, thereby improving the power utilization rate of the small wind power generation system, broadening its application area, and bringing greater economic benefits to users. benefit.

The above is only a preferred embodiment of the utility model, and it should be pointed out that for those of ordinary skill in the art, some improvements can be made without departing from the principle of the utility model, and these improvements should also be regarded as the present invention. Protection scope of utility model.

Claims (3)

1. small-size wind power-generating grid-connected system with storage battery comprises:

Wind energy conversion system and the wind-driven generator of under wind energy conversion system drives, working;

Rectification circuit, its input is connected with the output of wind-driven generator;

Inverter circuit, its input is connected with the output of rectification circuit by dc bus, and output links to each other with electrical network and/or load;

It is characterized in that also comprising:

Batteries, charging circuit, discharge circuit, charge controller and discharge controller, described batteries is connected with dc bus with discharge circuit by charging circuit respectively, described charge controller is connected with charging circuit, and described discharge controller is connected with discharge circuit.

2. a kind of small-size wind power-generating grid-connected system according to claim 1 with storage battery, it is characterized in that described charge controller is fuzzy sliding formwork charge controller, the input of described fuzzy sliding formwork charger receives comparison signal and the charging current detected value of batteries and the comparison signal between the charging current reference value between charging voltage detected value and the charging voltage reference value, and output is connected with charging circuit.

3. a kind of small-size wind power-generating grid-connected system according to claim 1 with storage battery, it is characterized in that described discharge controller is fuzzy sliding formwork discharge controller, the input of described fuzzy sliding formwork discharge controller receives the busbar voltage detected value of dc bus and the comparison signal between the busbar voltage reference value, and output is connected with discharge circuit.

Images