CN105490305A - Distributed energy access system and power grid power factor improving method thereof - Google Patents

Abstract

The invention discloses a distributed energy access system, which is connected to the grid side through a grid bus; the system includes: a distributed power generation device, whose output circuit is connected to the grid bus, generates power and outputs electric energy to the grid side; The compensation device, whose circuit is connected to the output end of the distributed generation device and the grid bus, reduces the reactive power supply of the grid; the energy storage device, whose circuit is connected to the output end of the distributed generation device and the grid bus, to compensate the fluctuation of the active output of the distributed generation device; control The system communicates with a distributed power generation device, a reactive power compensation device and an energy storage device. The control system of the invention takes the power factor as the control target, reduces the reactive power supply of the power grid through the reactive power compensation device, and compensates the fluctuation of the active output of the distributed power supply through the energy storage device, which can effectively improve the power factor of the power grid and maintain stability.

Description

Distributed energy access system and method for improving power factor of power grid

technical field

The invention relates to the field of power system power quality, in particular to a distributed energy access system and a method for improving power factor of a power grid.

Background technique

The electric power industry is the economic lifeline of a country and occupies an extremely important position in the national economy and people's lives. At present, the shortage of traditional energy sources, smog and other environmental pollution problems have prompted clean energy to gradually replace fossil energy in an all-round way. Clean substitution and electric energy substitution will be an important direction for the sustainable development of world energy in the future. With the continuous decline in the production price per kilowatt of electricity and the strong support at the policy level, the application range of distributed energy generation such as photovoltaic power generation and wind power generation has become wider and wider, and it has begun to develop from special occasion applications to commercial applications. Large-scale business districts, hospitals and other load power supplies have gradually formed a new power supply mode that combines large power grids with distributed power generation technology.

Distributed power output power has strong intermittency, randomness and volatility. Distributed energy access to the grid will cause voltage fluctuations and flicker, power factor fluctuations and reductions, power harmonics, voltage sags and deviations, etc. Seriously affect the power quality of the distribution network and even the transmission network. As far as the power factor is concerned, the distributed power supply and the grid supply power to the load at the same time, resulting in a decrease in the active power provided by the grid and fluctuating with the fluctuation of the distributed power output power, causing an increase in the loss of the grid and a decrease in power quality. Damage to related equipment; What's more, the power consumption unit may even be fined for lowering the power factor.

In order to improve the efficiency of electric energy use, the former Ministry of Water Resources and Electric Power and the State Price Bureau issued the "Power Factor Adjustment Electricity Fee Measures" in 1983, using economic means to assess the power factor of customers' electricity consumption, and to promote users to strengthen reactive power management and install Set up reactive power compensation equipment, save electric energy, played a big role. However, the output power of distributed power generation is very intermittent, random and fluctuating, and it is impossible to maintain a high power factor all the time only by relying on reactive power compensation equipment; in addition, for loads with small reactive power demand, reactive power compensation equipment ( For example, the static var generator, SVG) may not be put into operation because it cannot meet the minimum reactive power requirement.

Contents of the invention

The invention provides a distributed energy access system and a method for improving power factor of a grid, which can improve and stabilize the power factor after the distributed energy is connected to the grid, and is beneficial to improving power quality.

In order to achieve the above purpose, the present invention provides a distributed energy access system, which is characterized in that the system is connected to the grid side through the grid bus; the system includes:

Distributed power generation device, the output circuit of which is connected to the grid bus, generates electricity and outputs electric energy to the grid side;

The reactive power compensation device, whose circuit is connected to the output end of the distributed power generation device and the grid bus, reduces the reactive power supply of the grid;

The energy storage device, whose circuit is connected to the output terminal of the distributed power generation device and the busbar of the grid, compensates the fluctuation of the active power output of the distributed power generation device;

The control system communicates with the distributed power generation device, the reactive power compensation device and the energy storage device.

The above system also includes a load that is electrically connected to the output terminal of the distributed generation device and the busbar of the grid.

The above-mentioned reactive power compensation device is a static var generator.

The above-mentioned energy storage device is a hybrid energy storage system.

A method for improving the grid power factor of a distributed energy access system, which is characterized in that the distributed energy access system includes a distributed power generation device connected to the grid bus, a reactive power compensation device, and an energy storage device, as well as communication connection distribution The control system of type power generation device, reactive power compensation device and energy storage device: the improvement method includes:

Type selection and capacity calculation of reactive power compensation device;

Selection and capacity calculation of energy storage devices;

The control system uniformly controls the operation of the reactive power compensation device and the energy storage device.

The type selection of the above reactive power compensation device is a static var generator.

The above energy storage device is selected as a hybrid energy storage system.

The unified control of the operation of the reactive power compensation device and the energy storage device by the above control system includes:

The control system sets the power factor target value;

The control system collects the state parameters of the distributed power generation device, reactive power compensation device, energy storage device and grid side;

The control system calculates the operating parameters of the energy storage device and reactive power compensation device according to the target value of maintaining the power factor;

The control system sends control commands to the energy storage device and the reactive power compensation device according to the operating parameters.

Compared with the distributed energy access technology of the prior art, the distributed energy access system of the present invention and its method for improving the grid power factor have the advantage that the control system of the present invention takes the power factor as the control target, and reduces The reactive power supply of the grid, through the energy storage device to compensate for the fluctuation of the active output of the distributed power supply, can effectively improve the power factor of the grid and maintain stability.

Description of drawings

Fig. 1 is a circuit block diagram of the distributed energy access system of the present invention;

Fig. 2 is a flow chart of the method for improving the grid power factor of the distributed energy access system of the present invention.

detailed description

Specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

As shown in Figure 1, it is an embodiment of a distributed energy access system. The distributed energy access system is connected to the grid side 106 through the grid bus 105 . The system includes: a distributed power generation device 101 , a reactive power compensation device 102 , an energy storage device 103 , a control system and a load 104 .

The output circuit of the distributed power generation device 101 is connected to the grid bus 105 , connected to the grid side 106 through the grid bus 105 for power generation, and outputs electric energy to the grid side 106 through the grid bus 105 .

The reactive power compensation device 102 adopts a static var generator (SVG), and its circuit is connected to the output end of the distributed power generation device 101 and the grid bus 105 to reduce the reactive power supply of the grid and thereby control the power factor.

The energy storage device 103 adopts a hybrid energy storage system (HybridEnergyStorageSystem, HESS), and its circuit is connected to the output terminal of the distributed power generation device 101 and the grid bus 105, which is used to compensate the fluctuation of the active output of the distributed power generation device, improve the grid power factor and maintain stability.

The load 104 is electrically connected to the output end of the distributed generation device 101 and the grid bus 105 .

The control system communicates with the distributed power generation device 101, the reactive power compensation device 102, and the energy storage device 103, which is used for real-time recording and collection of the relevant State parameters, taking the maintenance of power factor as the target value as the control target, analyze and calculate the operating parameters that the energy storage device 103 and the reactive power compensation device 102 need to achieve, and issue control to the energy storage device 103 and the reactive power compensation device 102 instruction.

As shown in Figure 2, the present invention also discloses a method for improving the power factor of the distributed energy access system power grid, which specifically includes the following steps:

Step 1. Selection and capacity calculation of reactive power compensation device.

Step 1.1, selection of reactive power compensation device.

The typical representative of the early power factor compensation device is the synchronous condenser. The synchronous condenser can not only compensate the fixed reactive power, but also dynamically compensate the changing power factor. This device is still used in the field of power factor compensation, and with the advancement of control technology, its control performance has been improved.

The reactive power compensation capacitor is one of the traditional methods to compensate reactive power. Compared with the synchronous condenser, the cost of the reactive power compensation capacitor is much less when the adjustment effect is similar. Therefore, the rapid development of capacitors has almost replaced the synchronous speed governor in the transmission system. However, compared with synchronous speed controllers, capacitors are suitable for local dispersion compensation, but when there are harmonics in the system, parallel resonance may occur, which amplifies the harmonics, and accidents of capacitors burning out occur from time to time.

Static var compensation (SVC) has been greatly developed in recent years, and has been widely used in wave impedance compensation of power transmission system and section compensation of long-distance power transmission, and is also widely used in load reactive power compensation. Its typical representatives are fixed capacitors and thyristor controlled reactors. Thyristor switched capacitors are also widely used. An important characteristic of the static var compensation device is that it can continuously adjust the reactive power of the compensation device. This continuous adjustment is achieved by adjusting the trigger delay angle Q of the thyristor in the TCR. TCS can only be switched in groups, and cannot continuously adjust reactive power. Only when it is used in conjunction with TCR, can the continuous adjustment of the overall reactive power of the compensation device be realized.

A more advanced modern compensation device than SVC is the Static Var Generator (SVG). Compared with the traditional SVC device represented by TCR, SVG has a faster adjustment speed and a wider operating range, and can greatly reduce the harmonic content in the compensation current after taking measures such as multiplexing, multilevel or PWM technology. More importantly, the reactor and capacitive components used in SVG are much smaller than those used in SVC, which will greatly reduce the size and cost of the device. SVG has such superior performance, showing the development direction of dynamic reactive power compensation device.

As mentioned above, the reactive power compensation device 102 in the present invention uses a static var generator.

Step 1.2, determining the capacity of the reactive power compensation device.

The determination of the optimal reactive power compensation capacity mainly adopts artificial intelligence methods such as traditional optimization algorithms, tabu search algorithms, simulated annealing algorithms, artificial neural networks, expert systems, genetic algorithms, and particle swarm optimization algorithms. Distributed power supply systems generally have a small number of users and a small system capacity. It is relatively reasonable to calculate the compensation capacity using the traditional optimization method, that is, to find the best compensation capacity from the perspective of the smallest network loss, the smallest annual operating cost, and the smallest annual expenditure.

To sum up, the present invention uses a traditional optimization algorithm to determine the capacity of the reactive power compensation device.

Step 2. Type selection and capacity calculation of the energy storage device.

Step 2.1, selection of the energy storage device.

Commonly used energy storage methods include pumped water storage, compressed air energy storage, battery energy storage, superconducting magnetic energy storage, and supercapacitor energy storage. Among them, pumped water storage, compressed air energy storage and battery energy storage are energy-based energy storage systems, which have the characteristics of high energy density, slow response speed, or not suitable for frequent switching between charge and discharge; superconducting magnetic energy storage and supercapacitors are power-type energy storage systems The system has the characteristics of high power density, fast response and low energy storage capacity. At present, the hybrid energy storage system composed of a combination of multiple energy storage methods has higher practical application value because it combines the advantages of multiple energy storage technologies.

The hybrid energy storage of supercapacitor and energy storage battery (hybrid energy storage system, HybridEnergyStorageSystem, referred to as HESS) can effectively play complementary characteristics and make full use of the respective advantages of energy storage equipment.

In summary, the energy storage device 103 of the present invention uses a hybrid energy storage system.

Step 2.2, determining the capacity of the energy storage device.

In order to meet the requirement of smoothing the power output fluctuations of distributed energy sources, the energy storage device 103 should have a large enough capacity. The maximum capacity required by the energy storage device 103 can also be obtained using a simulation method.

Step 3, the control system uniformly controls the operation of the reactive power compensation device 102 and the energy storage device 103 .

Step 3.1, the control system sets the target value of the power factor.

Step 3.2, the control system enters the parameters of the distributed power generation device 101, the energy storage transposition 103, the reactive power compensation device 102 and the related parameters of the grid side 106.

Step 3.3. The control system collects relevant data of the distributed power generation device 101 , the energy storage transposition 103 , the reactive power compensation device 102 and the grid side 106 .

Step 3.4, the control system takes maintaining the power factor as the target value as the control target, and after analysis and calculation, the operation requirements of the energy storage device 103 and the reactive power compensation device 102 are obtained.

Step 3.5, the control system sends control commands to the energy storage transposition 103 and the reactive power compensation device 102 .

Although the content of the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description should not be considered as limiting the present invention. Various modifications and alterations to the present invention will become apparent to those skilled in the art upon reading the above disclosure. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims (8)

1. A distributed energy access system, characterized in that the system is connected to the grid side through the grid bus; the system includes: Distributed power generation device, the output circuit of which is connected to the grid bus, generates electricity and outputs electric energy to the grid side; The reactive power compensation device, whose circuit is connected to the output end of the distributed power generation device and the grid bus, reduces the reactive power supply of the grid; The energy storage device, whose circuit is connected to the output terminal of the distributed power generation device and the busbar of the grid, compensates the fluctuation of the active power output of the distributed power generation device; The control system communicates with the distributed power generation device, the reactive power compensation device and the energy storage device. 2. The distributed energy access system according to claim 1, characterized in that the system further comprises a load that is electrically connected to the output end of the distributed generation device and the grid bus. 3. The distributed energy access system according to claim 1, wherein the reactive power compensation device is a static var generator. 4. The distributed energy access system according to claim 1, wherein the energy storage device is a hybrid energy storage system. 5. A method for improving the grid power factor of a distributed energy access system, characterized in that the distributed energy access system includes a distributed power generation device connected to the grid bus, a reactive power compensation device and an energy storage device, and a communication Control system connecting distributed power generation devices, reactive power compensation devices, and energy storage devices: the improvement method includes: Type selection and capacity calculation of reactive power compensation device; Selection and capacity calculation of energy storage devices; The control system uniformly controls the operation of the reactive power compensation device and the energy storage device. 6. The method for improving the grid power factor of a distributed energy access system according to claim 5, wherein the reactive power compensation device is selected as a static var generator. 7. The method for improving the grid power factor of a distributed energy access system according to claim 5, wherein the energy storage device is selected as a hybrid energy storage system. 8. The method for improving the grid power factor of the distributed energy access system according to claim 5, wherein the unified control of the operation of the reactive power compensation device and the energy storage device by the control system includes: The control system sets the power factor target value; The control system collects the state parameters of the distributed power generation device, reactive power compensation device, energy storage device and grid side; The control system calculates the operating parameters of the energy storage device and reactive power compensation device according to the target value of maintaining the power factor; The control system sends control commands to the energy storage device and the reactive power compensation device according to the operating parameters.