CN117154743A - Methods to reduce the construction cost of dynamic voltage restorers in parks based on demand response - Google Patents

Abstract

The invention discloses a method for reducing the construction cost of a park's dynamic voltage restorer based on demand response, which specifically includes the following contents: complete voltage compensation principle, sensitive equipment process interruption management method, voltage sag management revenue model, voltage sag Governance cost model, dynamic voltage restorer optimal configuration model taking into account demand response and nested segmentation algorithm model solution. The present invention relates to the technical field of electrical engineering, and specifically provides a method for reducing the construction cost of a dynamic voltage restorer in a park based on demand response. On the one hand, the method uses existing power Internet of Things facilities to implement demand response for interruptible loads, thereby reducing DVR construction costs; on the other hand, it contributes to the overall planning of dynamic voltage restorers and park adjustable power resources for park operators.

Description

Methods to reduce the construction cost of dynamic voltage restorers in parks based on demand response

Technical field

The invention relates to the technical field of electrical engineering, specifically a method for reducing the construction cost of a dynamic voltage restorer in a park based on demand response.

Background technique

As the load capacity of the park and the proportion of new energy become higher and higher, the frequency of voltage sag will also increase. The economic losses caused to sensitive equipment or components such as motors and LED light drivers are becoming more and more serious, and it is necessary to control them. The perspective of voltage sag management is to reduce the frequency of voltage sag and its secondary hazards, which is often solved by using voltage compensation equipment or uninterruptible power supplies.

Voltage sag management is the joint responsibility of park operators and the power grid. However, in real life, park operators are often under greater pressure, which means that most governance strategies from the perspective of the power grid are out of reach for park operators. and. For example, the literature: Research on the optimal configuration of multiple dynamic voltage restorers in distribution networks (Power Grid Technology, 2013, 37(10): 2991-2996) points out that dynamic voltage restorers (dynamic voltageregulator, DVR) to solve the problem; Literature: Comprehensive configuration planning of voltage sag control equipment based on full life cycle cost (Power System Protection and Control, 2018, 46(18):128-134) for static synchronous compensator in transmission network And how to economically configure DVR to alleviate the voltage sag problem was explored. There is no doubt that this can indeed ensure the voltage quality of the grid power supply outlet, but it is not suitable when the park has a high proportion of new energy, because the power supply on the non-grid side of the park will affect the overall power supply voltage quality. For this reason, more and more parks with high new energy capacity have to equip themselves with high-cost DVRs. How to reduce costs and increase efficiency within the control of park operators has become a difficult problem. For park operators, what matters is whether sensitive equipment or components can be produced or operated normally, rather than the internal causes of voltage sag. As a result, the method of focusing on the stability of sensitive equipment process parameters (such as temperature, pressure, flow, and light intensity, etc.) has emerged as the focus of DVR configuration, and process immunity time (PIT), a standard for the unified measurement of process parameters, has become more and more important. been accepted. Literature: voltage dip immunity of equipment in installations-Main contributions and conclusions (International Conference&Exhibition on Electricity Distribution.IET, 2009.) and high-quality park power supply quality classification based on process immunity time and acceptable consequence status (Power Grid Technology, 2014, 38( 01): 211-216) verified the feasibility of PIT in voltage sag economic loss assessment and power supply management respectively; the literature evaluates voltage sag economic loss based on electrical characteristics-physical properties-perceived loss (Chinese Journal of Electrical Engineering, 2018 , 38(S1):105-110) pointed out that DVR can be used to extend the parameters of sensitive equipment at different stages of PIT to control voltage sag. However, the cost of DVR construction, which can easily reach hundreds of thousands, is too high and is still a heavy financial burden for park operators.

The idea of optimizing conventional DVR construction costs is to minimize construction costs by reasonably adapting DVR parameters, or by modifying DVR equipment. It is undeniable that this is a correct and necessary idea, but with more and more intelligent measurement and control equipment in the park, the potential for reducing construction costs has not been fully explored. The DVR construction cost can be divided into the sum of the unit capacity cost and the unit energy storage system cost, and then the product of the DVR capacity. For park operators, the former can be regarded as a fixed item, and the latter is positively related to the energy compensated by the DVR when a voltage sag occurs, and the energy compensated by the DVR is related to the amplitude of the voltage sag and the power angle level. This is completely true. Maneuverable space. When a voltage sag is detected, demand response is implemented based on interruptible loads to reasonably and briefly increase the voltage and power angle levels of sensitive equipment, which can reduce the energy of DVR compensation and thereby reduce DVR construction costs. This approach is currently missing, and given the growing popularity of campus demand response, there is no additional cost to the campus operator.

Contents of the invention

As sensitive load capacity and new energy access become higher and higher, park operators have to configure dynamic voltage restorers on their own to cope with the negative impact of voltage sag on sensitive equipment or components. However, the high construction cost of dynamic voltage restorers, which often cost hundreds of thousands, has deterred park operators. In view of the above situation, in order to make up for the above existing shortcomings, the present invention provides a method to reduce the construction cost of dynamic voltage restorer in the park based on demand response. On the one hand, the method uses existing power Internet of Things facilities to implement interruptible loads. Demand response, thereby reducing DVR construction costs, is the main purpose of the present invention; on the other hand, around the process parameter idea of controlling voltage sag in sensitive equipment, a dynamic voltage restorer optimal configuration model taking into account demand response is proposed, and through demand In response, the compensation capacity of the dynamic voltage restorer is reduced to ensure that the related net present value is maximized, which contributes to the overall planning of the dynamic voltage restorer and the park's adjustable power resources by the park operator.

The present invention provides the following technical solution: the method proposed by the present invention to reduce the construction cost of the dynamic voltage restorer in the park based on demand response uses a nested segmentation algorithm to solve the optimal configuration model of the dynamic voltage restorer taking into account the demand response, and obtains the dynamic voltage The planning scheme of the restorer, which involves the principle of complete voltage compensation, the treatment method of process interruption of sensitive equipment, the revenue model of voltage sag management, the cost model of voltage sag management, the dynamic voltage restorer optimal configuration model taking into account demand response and Nested segmentation algorithm model solution.

(1) Principle of complete voltage compensation

The dynamic voltage restorer DVR is used as a voltage sag control device. Its principle is to compensate for the voltage amplitude and phase of sensitive equipment or components through energy exchange with the DVR energy storage system when a voltage sag is detected. Strategies include in-phase compensation, full voltage compensation, minimum energy compensation and hybrid compensation;

This solution adopts a complete voltage compensation strategy, that is, the amplitude and phase are compensated through the DVR to the level before the voltage sag occurs. The active power output by the DVR is as follows:

In the formula: U _S and U _γ are the sag voltage and sensitive equipment voltage respectively; is the load power factor;/> is the phase angle of U _S , I _L is the load current;

(2) Management methods for process interruption of sensitive equipment

The operation of sensitive equipment can be regarded as a continuous exchange with the outside world, its own energy and matter, at the cost of high-quality process parameters being gradually consumed, and eventually tending to be in equilibrium with the environment when there is no external force input; therefore, voltage sag makes the sensitive equipment Equipment shutdown can be seen as the deterioration of the process parameters in the above-mentioned high-quality state until forced downtime, which indicates that the process parameters are related to exogenous factors in addition to the amount of electricity;

When the operation process of sensitive equipment encounters a voltage sag, the process immunity time (PIT) is the time when the process parameters exceed the acceptable limit; usually, the failure of sensitive equipment is manifested by the process parameters exceeding the threshold, and the operation of sensitive equipment is interrupted. If the process is interrupted, the park operator has to bear the corresponding costs;

By installing a DVR, the DVR injects the energy of its energy storage system to increase the residual voltage during the voltage sag, allowing sensitive equipment to ride through the short-term voltage sag, thereby achieving the purpose of governance;

(3) Revenue model for voltage sag management

The configuration of DVR in the park can avoid the interruption of the operation process of sensitive equipment to a certain extent, but it will still cause losses due to voltage fluctuations, such as the production of defective products. These losses are positively related to the deviation of process parameters;

The reduced losses before and after DVR construction are regarded as income B ₁ :

B ₁ =C _bef -C _aft (2)

In the formula: C _bef and C _aft are the annual economic losses caused by the interruption of the operation of sensitive equipment caused by voltage sag before and after DVR construction respectively;

1) Annual economic loss before DVR construction

C _bef ＝P _vs N _vs C _vs,per (3)

In the formula: P _vs is the probability of interruption of operation of sensitive equipment due to voltage sag; N _vs is the number of annual voltage sag; C _{vs, per} is the average loss of a single voltage sag; the relevant parameters can be obtained through history Obtained from voltage monitoring data;

2) Annual economic loss after DVR construction

In the formula: It is the equivalent probability of the loss of a single sensitive equipment during non-operational interruption to the maximum non-operational interruption loss;/> It is the maximum loss value for a single non-operational interruption of sensitive equipment, which can be obtained by the survey method;

The non-operational interruption loss of sensitive equipment is positively related to the square of the process parameter deviation:

In the formula: Ω is the fault zone of the withstand characteristics of sensitive equipment; θ is the severity of a single non-operation interruption loss; p _v (V) and p _T (T) are the probability density of voltage sag duration and amplitude respectively. , obtained by fitting historical voltage data;

(4) Voltage sag control cost model

Relying on the demand response of interruptible loads as an idea to reduce DVR construction costs, voltage sag management costs include DVR construction costs and demand response costs:

C _sum =C _dvr -C _dr (6)

In the formula: C _dvr and C _dr are DVR construction cost and demand response cost respectively;

1) DVR construction cost

Energy storage DVR is used for complete voltage compensation. Its construction cost includes capacity cost and energy storage system cost. The operation and maintenance cost C _op is set to 5% of the construction cost:

In the formula: C _sun and C _eun are the capacity cost and energy storage system cost of DVR respectively, both of which are related to the voltage level; ΔT _Ⅰ is the support time of the energy storage system; It is the compensation capacity of DVR;

Based on the complete voltage compensation strategy, the compensation capacity of the DVR for:

In the formula: N ₁ is the node set of the DVR access park line topology; and/> are the active power and power angle injected into the i-th DVR respectively. The principle is the same as Equation (1);

In order to simplify the DVR planning problem, the average sag voltage can be obtained based on historical voltage data. and average sag angle/> Treating it as a known quantity, formula (1) can be rewritten as:

In the formula: The i-th DVR is responsible for the compensation power of the j-th sensitive device; N ₂ is the node set of sensitive devices connected to the campus line topology;/> and/> are the active power, voltage and power angle of the jth sensitive equipment respectively;

Combining equations (7) to (9), it can be seen that when sensitive equipment is operating normally, and/> tends to the rated value, so it can be increased by increasing/> and/> Come/> become smaller, thus making/> Become smaller and reduce the construction cost of the DVR; therefore, when a voltage sag is detected, it is raised within a suitable range for a short period of time/> Make the sag voltage and sag power angle at this time larger than the history/> and/> This provides a theoretical basis for reducing DVR construction costs;

2) Demand response cost

Park operators obtain direct control of interruptible loads through contract signing. When a voltage sag is detected, the voltage adjustment of sensitive equipment access nodes is achieved by shutting down or adjusting the working conditions of interruptible loads;

In the formula: N ₃ is the set of nodes in the park that can interrupt load access; and/> are respectively the power reduction and compensation price of the interruptible load of the k-th node;

(5) Optimal configuration model of dynamic voltage restorer taking into account demand response

DVR compensation capacity is often benchmarked against the capacity of sensitive equipment, which means that there is no need to pay attention to the campus power network topology and only need to plan the DVR compensation time; the longer the compensation time, the better the effect of stabilizing the process parameters of sensitive equipment, but the construction cost The higher; under the idea of reducing DVR construction costs through demand response, the power network topology must be considered, and the DVR compensation capacity is a decision-making quantity, which is related to the voltage and power angle at sensitive equipment; for this reason, the configuration model is optimized Constraints related to process parameters, demand response constraints, and campus network constraints should be considered;

1) Objective function

The planning goal of DVR is constructed using the net present value method. The design objective function is to maximize the net present value of investment, which can take into account voltage quality while ensuring the shortest payback period;

In the formula: N _Y is the project cycle year;

2) Constraints related to process parameters

By extending the duration of the first stage in Figure 2, the voltage sag that sensitive equipment can ride through in a short time is ensured as follows:

In the formula: and/> are the original process immunity time and restart time of the jth sensitive device respectively;/> is the upper limit of the compensation time of the i-th DVR;

3) Demand response constraints

Mainly the upper and lower bound constraints of interruptible load and 0-1 integer constraints;

In the formula: and/> are respectively the previous and next periods of the kth interruptible load;/> It is a 0-1 variable, 1 means calling, 0 means not calling;

4) Campus network constraints

The park is usually a radial power network. New energy, park incoming lines and sensitive equipment are all connected to the power network nodes. Each node includes equation constraints (balance constraints and power flow constraints) and voltage upper and lower limit constraints. For For sensitive load access nodes, the upper limit of the voltage constraint is the upper limit of the voltage range allowed by the sensitive equipment during normal operation, and the lower limit is the sum of the lower limit of the voltage range allowed by the sensitive equipment during normal operation and the voltage raised by demand response. This can reduce DVR Energy to overcome voltage sag; in addition, sensitive equipment access nodes also include power angle constraints, whose setting principles are the same as voltage constraints. Equation (15) is the power balance constraint, Equation (16) is the power flow constraint of the network, Equation (17) and Equation (18) is the node voltage constraint, and Equation (19) is the power angle constraint of the sensitive load access node;

In the formula: N ₄ and N ₅ are respectively the set of nodes connected to the power grid in the park and the set of all load nodes in the park; Active power injected into the nth park access grid node;/> is the average power of the m-th load node;

In the formula: P _x and Q _x are the active and reactive power of node x; U _x is the voltage of node x; G _xy , B _xy and θ _xy are the conductance, susceptance and work between node x and node y respectively. horn;

In the formula: U ^L,max and U ^L,min are respectively the upper and lower voltage limits of the m-th non-sensitive equipment access node;

In the formula: is the upper limit of the voltage of the access node of the jth sensitive device, which is equal to the upper limit of the allowable voltage of the sensitive device during normal operation;/> is the lower limit of the voltage of the jth sensitive equipment access node, which is equal to the lower limit of the voltage range allowed when the sensitive equipment operates normally/> vs. voltage boosted by demand response/> Sum;

In the formula: is the upper limit of the power angle of the jth sensitive device access node, which is equal to the upper limit of the power angle allowed when the sensitive device is operating normally;/> is the lower limit of the power angle of the jth sensitive device access node, which is equal to the lower limit of the power angle range allowed when the sensitive device is operating normally/> Rising power from demand response/> Sum;

(6) Nested segmentation algorithm model solution

The optimal configuration model of the dynamic voltage restorer taking into account demand response is a mixed integer nonlinear non-convex model, which can be solved by the nested segmentation algorithm. The reason is that the nested segmentation algorithm has global convergence characteristics and avoids falling into the local optimal solution. And affect the DVR construction cost.

The beneficial effects achieved by the present invention by adopting the above structure are as follows: The method proposed by the present invention to reduce the construction cost of dynamic voltage restorer in the park based on demand response can be realized by using the dynamic voltage restorer optimal configuration model that takes into account demand response in this solution. Demand response to reduce DVR compensation capacity, thereby reducing the high construction cost of DVR. The specific advantages of this solution can be summarized as:

1) Implementing demand response can reduce the capacity cost of DVR and the cost of energy storage system, but the economic improvement rate is not high, and the cost savings in medium and large parks are considerable;

2) Voltage sag management strategies for sensitive equipment operating process parameters can mitigate the negative impact of voltage sag;

3) In reality, compared with the power grid, park operators face more challenges caused by voltage sag. In the context of the gradual large-scale application of demand response, internal demand response can be regarded as a way to improve its passive position.

Description of the drawings

The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. In the attached picture:

Figure 1 is a complete voltage compensation vector diagram of the present invention;

Figure 2 is a schematic diagram of the process immunity time of the present invention;

Figure 3 is a schematic diagram of the dynamic voltage restorer of the present invention for controlling voltage sag;

Figure 4 is a flow chart for solving the nested segmentation algorithm of the present invention;

Figure 5 is a typical park topology diagram of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them; based on The embodiments of the present invention and all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

It should be noted that the words "front", "back", "left", "right", "upper" and "lower" used in the following description refer to the directions in the drawings, and the words "inside" and "outside" ” refers to the direction toward or away from the geometric center of a specific part, respectively.

The method proposed by this invention to reduce the construction cost of dynamic voltage restorer in the park based on demand response specifically includes the following steps:

(1) Full voltage compensation

The dynamic voltage regulator (DVR) is used as a voltage sag management device. Its principle is to control the voltage amplitude of sensitive equipment or components through energy exchange with the DVR energy storage system when a voltage sag is detected. Compensate with the phase. The compensation strategies include in-phase compensation, complete voltage compensation, minimum energy compensation and hybrid compensation;

The key technology of the present invention is applicable to the complete voltage compensation strategy, that is, the amplitude and phase are compensated through the DVR to the level before the voltage sag occurs. The principle is shown in Figure 1. In the figure: U _S and U _γ are the sag voltage and sensitive equipment voltage respectively; U _PLL is the voltage phasor before the sag; U _dvr is the output voltage of the DVR; and/> are the phase angles of U _dvr and U _S respectively;/> is the load power factor; _IL is the load current. For this reason, the active power output by the DVR is as follows:

In the formula: U _S and U _γ are the sag voltage and sensitive equipment voltage respectively; is the load power factor;/> is the phase angle of U _S , I _L is the load current;

(2) Management methods for process interruption of sensitive equipment

The operation of sensitive equipment can be regarded as a continuous exchange with the outside world, its own energy and matter, at the cost of high-quality process parameters being gradually consumed, and eventually tending to be in equilibrium with the environment when there is no external force input; therefore, voltage sag makes the sensitive equipment Equipment shutdown can be seen as the deterioration of the process parameters in the above-mentioned high-quality state until forced downtime, which indicates that the process parameters are related to exogenous factors in addition to the amount of electricity;

When sensitive equipment encounters a voltage sag during operation, the process immunity time (PIT) is the time during which the process parameters exceed acceptable limits, as shown in Figure 2. In the figure: p _nom and p _lim are the rated values and thresholds of sensitive equipment process parameters respectively; t ₀ , t ₁ and t ₂ are respectively the starting moment of voltage sag, equipment failure moment and process interruption moment. Usually, the failure of sensitive equipment is manifested as process parameters exceeding the threshold. If the operation of sensitive equipment is interrupted, the process will be interrupted, and the park operator has to bear the corresponding price.

By installing a DVR, the duration of the first stage in Figure 2 can be extended. The DVR injects the energy of its energy storage system to increase the residual voltage during the voltage sag, allowing sensitive equipment to ride through the short-term voltage sag, thereby achieving control purpose, as shown in Figure 3. In the figure: the blue line is the voltage and the change of process parameters after DVR control. T _sup and T _toler are respectively the voltage compensation time and the sag tolerance time of sensitive equipment.

(3) Revenue model for voltage sag management

The configuration of DVR in the park can avoid the interruption of the operation process of sensitive equipment to a certain extent, but it will still cause losses due to voltage fluctuations, such as the production of defective products. These losses are positively related to the deviation of process parameters;

The reduced losses before and after DVR construction are regarded as income B ₁ :

B ₁ =C _bef -C _aft (2)

In the formula: C _bef and C _aft are the annual economic losses caused by the interruption of the operation of sensitive equipment caused by voltage sag before and after DVR construction respectively;

1) Annual economic loss before DVR construction

C _bef ＝P _vs N _vs C _vs,per (3)

In the formula: P _vs is the probability of interruption of operation of sensitive equipment due to voltage sag; N _vs is the number of annual voltage sag; C _{vs, per} is the average loss of a single voltage sag; the relevant parameters can be obtained through history Obtained from voltage monitoring data;

2) Annual economic loss after DVR construction

In the formula: It is the equivalent probability of the loss of a single sensitive equipment during non-operational interruption to the maximum non-operational interruption loss;/> It is the maximum loss value for a single non-operational interruption of sensitive equipment, which can be obtained by the survey method;

The non-operational interruption loss of sensitive equipment is positively related to the square of the process parameter deviation:

In the formula: Ω is the fault zone of the withstand characteristics of sensitive equipment; θ is the severity of a single non-operation interruption loss; p _v (V) and p _T (T) are the probability density of voltage sag duration and amplitude respectively. , obtained by fitting historical voltage data;

(4) Voltage sag control cost model

Relying on the demand response of interruptible loads as an idea to reduce DVR construction costs, voltage sag management costs include DVR construction costs and demand response costs:

C _sum =C _dvr -C _dr (6)

In the formula: C _dvr and C _dr are DVR construction cost and demand response cost respectively;

1) DVR construction cost

Energy storage DVR is used for complete voltage compensation. Its construction cost includes capacity cost and energy storage system cost. The operation and maintenance cost C _op is set to 5% of the construction cost:

In the formula: C _sun and C _eun are the capacity cost and energy storage system cost of DVR respectively, both of which are related to the voltage level; ΔT _Ⅰ is the support time of the energy storage system; It is the compensation capacity of DVR;

Based on the complete voltage compensation strategy, the compensation capacity of the DVR for:

In the formula: N ₁ is the node set of the DVR access park line topology; and/> are the active power and power angle injected into the i-th DVR respectively. The principle is the same as Equation (1);

In order to simplify the DVR planning problem, the average sag voltage can be obtained based on historical voltage data. and average sag angle/> Treating it as a known quantity, formula (1) can be rewritten as:

In the formula: The i-th DVR is responsible for the compensation power of the j-th sensitive device; N ₂ is the node set of sensitive devices connected to the campus line topology;/> and/> are the active power, voltage and power angle of the jth sensitive equipment respectively;

Combining equations (7) to (9), it can be seen that when sensitive equipment is operating normally, and/> tends to the rated value, so it can be increased by increasing/> and/> Come/> become smaller, thus making/> Become smaller and reduce the construction cost of the DVR; therefore, when a voltage sag is detected, it is raised within a suitable range for a short period of time/> Make the sag voltage and sag power angle at this time larger than the history/> and/> This provides a theoretical basis for reducing DVR construction costs;

2) Demand response cost

Park operators obtain direct control of interruptible loads through contract signing. When a voltage sag is detected, the voltage adjustment of sensitive equipment access nodes is achieved by shutting down or adjusting the working conditions of interruptible loads;

In the formula: N ₃ is the set of nodes in the park that can interrupt load access; and/> are respectively the power reduction and compensation price of the interruptible load of the k-th node;

(5) Optimal configuration model of dynamic voltage restorer taking into account demand response

DVR compensation capacity is often benchmarked against the capacity of sensitive equipment, which means that there is no need to pay attention to the campus power network topology and only need to plan the DVR compensation time; the longer the compensation time, the better the effect of stabilizing the process parameters of sensitive equipment, but the construction cost The higher; under the idea of reducing DVR construction costs through demand response, the power network topology must be considered, and the DVR compensation capacity is a decision-making quantity, which is related to the voltage and power angle at sensitive equipment; for this reason, the configuration model is optimized Constraints related to process parameters, demand response constraints, and campus network constraints should be considered;

1) Objective function

The planning goal of DVR is constructed using the net present value method. The design objective function is to maximize the net present value of investment, which can take into account voltage quality while ensuring the shortest payback period;

In the formula: N _Y is the project cycle year;

2) Constraints related to process parameters

By extending the duration of the first stage in Figure 2, the voltage sag that sensitive equipment can ride through in a short time is ensured as follows:

In the formula: and/> are the original process immunity time and restart time of the jth sensitive device respectively;/> is the upper limit of the compensation time of the i-th DVR;

3) Demand response constraints

Mainly the upper and lower bound constraints of interruptible load and 0-1 integer constraints;

In the formula: and/> are respectively the previous and next periods of the kth interruptible load;/> It is a 0-1 variable, 1 means calling, 0 means not calling;

4) Campus network constraints

The park is usually a radial power network. New energy, park incoming lines and sensitive equipment are all connected to the power network nodes. Each node includes equation constraints (balance constraints and power flow constraints) and voltage upper and lower limit constraints. For For sensitive load access nodes, the upper limit of the voltage constraint is the upper limit of the voltage range allowed by the sensitive equipment during normal operation, and the lower limit is the sum of the lower limit of the voltage range allowed by the sensitive equipment during normal operation and the voltage raised by demand response. This can reduce DVR Energy to overcome voltage sag; in addition, sensitive equipment access nodes also include power angle constraints, whose setting principles are the same as voltage constraints. Equation (15) is the power balance constraint, Equation (16) is the power flow constraint of the network, Equation (17) and Equation (18) is the node voltage constraint, and Equation (19) is the power angle constraint of the sensitive load access node;

In the formula: N ₄ and N ₅ are respectively the set of nodes connected to the power grid in the park and the set of all load nodes in the park; Active power injected into the nth park access grid node;/> is the average power of the m-th load node;

In the formula: P _x and Q _x are the active and reactive power of node x; U _x is the voltage of node x; G _xy , B _xy and θ _xy are the conductance, susceptance and work between node x and node y respectively. horn;

In the formula: U ^L,max and U ^L,min are respectively the upper and lower voltage limits of the m-th non-sensitive equipment access node;

In the formula: is the upper limit of the voltage of the access node of the jth sensitive device, which is equal to the upper limit of the allowable voltage of the sensitive device during normal operation;/> is the lower limit of the voltage of the jth sensitive equipment access node, which is equal to the lower limit of the voltage range allowed when the sensitive equipment operates normally/> vs. voltage boosted by demand response/> Sum;

In the formula: is the upper limit of the power angle of the jth sensitive device access node, which is equal to the upper limit of the power angle allowed when the sensitive device is operating normally;/> is the lower limit of the power angle of the jth sensitive device access node, which is equal to the lower limit of the power angle range allowed when the sensitive device is operating normally/> Rising power from demand response/> Sum;

(6) Nested segmentation algorithm model solution

The optimal configuration model of the dynamic voltage restorer taking into account demand response is a mixed integer nonlinear non-convex model, which can be solved by the nested segmentation algorithm. The reason is that the nested segmentation algorithm has global convergence characteristics and avoids falling into the local optimal solution. The process that affects DVR construction costs is shown in Figure 4.

The specific implementation steps of this plan are as follows:

Step 1: Preparation

Based on historical data and sensitive equipment or park parameter information, the following information is collected:

1) The probability of operation interruption of sensitive equipment, the number of annual sag, the sag loss, the equivalent probability of the loss of a single sensitive equipment during non-operation interruption to the maximum non-operation interruption loss, the maximum loss value of non-operation interruption, etc. regarding sensitivity Device data statistics information;

2) Information about the cost such as access voltage level of sensitive equipment, unit capacity and unit energy storage system cost, demand response subsidy price of interruptible load and its upper and lower limits;

3) The original process immunity time and restart time of the sensitive equipment process, the upper limit of the compensation time and other attribute information of the sensitive equipment;

4) Network topology information such as park power network parameters, upper and lower limits of node voltage and phase angle, normalized capacity of non-sensitive load nodes, etc.

Step 2: Build an optimized configuration model of the dynamic voltage compensator

Substitute the information obtained in the previous step into the proposed dynamic voltage restorer optimal configuration model that takes into account demand response, and compile the code;

Step 3: Solve the planning model

By calling the application program interface of the nested segmentation algorithm to solve the model in the previous step, and using its solution as the basis for the configuration of the dynamic voltage restorer, its construction cost can be further reduced.

A radial 6-node power network is used to simulate a park with new energy access, as shown in Figure 5. The park contains a wind turbine connected to 6 nodes, with a normalized trusted capacity of 10kW, which can be regarded as a power supply; it contains 3 sensitive equipment and 2 regular loads, and each sensitive equipment is equipped with a DVR, which is related to The production process and its parameters are shown in Table 1; the average load of conventional load node 4 and node 5 is set to 100kW. Demand response is implemented at these two nodes. The compensation unit price of demand response is 2 yuan/kW. The relevant The upper and lower limits of the interruption load are both 100kW and 0kW; the line parameters between each node are set with reference to the most common single-conductor transmission line parameters, as shown in Table 2; the upper and lower limits of the voltage of the non-sensitive load access node are 420V and 400V. The upper and lower voltage limits of sensitive equipment access nodes are both 410 and 400, and the upper and lower limits of the power angle are 25.84 (that is, the power factor is 0.85) and 18.20 (that is, the power factor is 0.95); the project cycle year is set to 15 years. The interest rate is 5%; grid access and photovoltaic access node 6 maintain a stable voltage of 410V and its power angle of 18.20°.

Table 1 Basic parameter table of sensitive load

Table 2 Park line parameter table

line Conductance G Susceptance B 1-2 0 2.85×10-7 2-3 0 2.65×10-7 3-4 0 2.75×10-7 4-5 0 3×10-7 5-6 0 2.9×10-7

The proposed dynamic voltage restorer optimal configuration model taking into account demand response is solved by the nested segmentation algorithm. The voltages of the three sensitive equipment access nodes, the support time of the energy storage system, the capacity of DVR compensation and its related costs are shown in the attached table. 3. As can be seen from Appendix Table 3, by configuring DVRs with capacities of 198.34kVA, 135.50kVA and 97.25kVA at node 1, node 2 and node 3 respectively, and the support times of the three energy storage systems are 3.80s, 3.88s and 3.91s, it can Realize the management of voltage sag in the park. At the same time, through the demand response mechanism, the voltage of the three sensitive equipment nodes can be raised to above 409V when a voltage sag occurs. The demand response fee paid for this is 9,000 yuan. The total cost of building the voltage sag management system is 0.9+53.88+56.82=1.116 million yuan. It can be seen that the demand response cost is much smaller than the capacity cost of DVR and energy storage system. In the construction cost of DVR, the capacity cost and energy storage system cost are almost equal, but the energy storage system cost is slightly higher.

Table 3 Model solution set considering demand response

project value DVR1 energy storage support time (s) 3.80 DVR2 energy storage support time (s) 3.88 DVR3 energy storage support time (s) 3.91 Node 1 voltage (V) 409.12 Node 2 voltage (V) 409.65 Node 3 voltage (V) 409.98 DVR1 compensation capacity (kVA) 198.34 DVR2 compensation capacity (kVA) 135.50 DVR3 compensation capacity (kVA) 97.25 Demand response cost (10,000 yuan) 0.9000 DVR capacity cost/energy storage system cost (10,000 yuan) 53.88/56.82

Appendix Table 4 shows the DVR configuration without considering demand response, that is, the voltage sag management model does not consider demand response constraints and demand response costs, and is also solved by the nested segmentation algorithm. Comparing Table 4-3, we can see that implementing demand response will hardly affect the support time of the energy storage system. The overall voltage of sensitive equipment that does not implement demand response is lower, making the compensation capacity of the DVR higher, resulting in capacity costs and energy storage system costs. The solution is higher than the voltage sag management model considering demand response, which is 55.18+58.19=1.1337 million yuan.

project value DVR1 energy storage support time (s) 3.80 DVR2 energy storage support time (s) 3.88 DVR3 energy storage support time (s) 3.91 Node 1 voltage (V) 407.22 Node 2 voltage (V) 407.53 Node 3 voltage (V) 407.76 DVR1 compensation capacity (kVA) 203.32 DVR2 compensation capacity (kVA) 138.97 DVR3 compensation capacity (kVA) 99.16 DVR capacity cost/energy storage system cost (10,000 yuan) 55.18/58.19

To sum up, although the implementation of demand response requires additional demand response costs, it improves the economy by (113.37-111.6)/113.37=1.56%. Although the improvement rate is not high, demand response within the park has become increasingly common in industrial and commercial parks. It does not require additional costs and infrastructure and is fully controllable by the park operator. It should be noted that this calculation example is for a park with a scale of 0.63MW, and the DVR transformation cost is only more than one million yuan. For investments in voltage sag management in medium and large parks above 20MW, even if demand response can only improve the economy by 1.56%, the total savings The cost is also close to one million, which also proves that the model in this chapter is highly implementable.

It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that these entities or operations must be mutually exclusive. any such actual relationship or sequence exists between them. Furthermore, the terms "comprises," "comprises," or any other variation thereof are intended to cover a non-exclusive inclusion such that a process, method, material or apparatus that includes a list of elements includes not only those elements but also those not expressly listed other elements, or elements inherent to the process, method, material or equipment.

Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art will understand that various changes, modifications, and substitutions can be made to these embodiments without departing from the principles and spirit of the invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (1)

1. A method to reduce the construction cost of dynamic voltage restorers in parks based on demand response, which is characterized by solving the optimal configuration model of dynamic voltage restorers taking into account demand response through a nested segmentation algorithm to obtain the planning scheme of dynamic voltage restorers, It involves the principle of complete voltage compensation, the management method of process interruption of sensitive equipment, the revenue model of voltage sag management, the cost model of voltage sag management, the dynamic voltage restorer optimal configuration model taking into account demand response, and the solution of the nested segmentation algorithm model Several parts, the specific contents of each part are: (1) Principle of complete voltage compensation The dynamic voltage restorer DVR is used as a voltage sag control device. Its principle is to compensate for the voltage amplitude and phase of sensitive equipment or components through energy exchange with the DVR energy storage system when a voltage sag is detected. Strategies include in-phase compensation, full voltage compensation, minimum energy compensation and hybrid compensation; This solution adopts a complete voltage compensation strategy, that is, the amplitude and phase are compensated through the DVR to the level before the voltage sag occurs. The active power output by the DVR is as follows: In the formula: U _S and U _γ are the sag voltage and sensitive equipment voltage respectively; is the load power factor;/> is the phase angle of U _S , I _L is the load current; (2) Management methods for process interruption of sensitive equipment The operation of sensitive equipment can be regarded as a continuous exchange with the outside world, its own energy and matter, at the cost of high-quality process parameters being gradually consumed, and eventually tending to be in equilibrium with the environment when there is no external force input; therefore, voltage sag makes the sensitive equipment Equipment shutdown can be seen as the deterioration of the process parameters in the above-mentioned high-quality state until forced downtime, which indicates that the process parameters are related to exogenous factors in addition to the amount of electricity; When the operation process of sensitive equipment encounters a voltage sag, the process immunity time (PIT) is the time when the process parameters exceed the acceptable limit; usually, the failure of sensitive equipment is manifested by the process parameters exceeding the threshold and the operation of the sensitive equipment being interrupted. If the process is interrupted, the park operator will have to bear the corresponding costs; By installing a DVR, the DVR injects the energy of its energy storage system to increase the residual voltage during the voltage sag, allowing sensitive equipment to ride through the short-term voltage sag, thereby achieving the purpose of governance; (3) Revenue model for voltage sag management The configuration of DVR in the park can avoid the interruption of the operation process of sensitive equipment to a certain extent, but it will still cause losses due to voltage fluctuations, such as the production of defective products. These losses are positively related to the deviation of process parameters; The reduced losses before and after DVR construction are regarded as income B ₁ : B ₁ =C _bef -C _aft (2) In the formula: C _bef and C _aft are the annual economic losses caused by the interruption of the operation of sensitive equipment caused by voltage sag before and after DVR construction respectively; 1) Annual economic loss before DVR construction C _bef ＝P _vs N _vs C _vs,per (3) In the formula: P _vs is the probability of interruption of operation of sensitive equipment due to voltage sag; N _vs is the number of annual voltage sag; C _{vs, per} is the average loss of a single voltage sag; the relevant parameters can be obtained through history Obtained from voltage monitoring data; 2) Annual economic loss after DVR construction In the formula: It is the equivalent probability of the loss of a single sensitive equipment during non-operational interruption to the maximum non-operational interruption loss; It is the maximum loss value for a single non-operational interruption of sensitive equipment, which can be obtained by the survey method; The non-operational interruption loss of sensitive equipment is positively related to the square of the process parameter deviation: In the formula: Ω is the fault zone of the withstand characteristics of sensitive equipment; θ is the severity of a single non-operation interruption loss; p _v (V) and p _T (T) are the probability density of voltage sag duration and amplitude respectively. , obtained by fitting historical voltage data; (4) Voltage sag control cost model Relying on the demand response of interruptible loads as an idea to reduce DVR construction costs, voltage sag management costs include DVR construction costs and demand response costs: C _sum =C _dvr -C _dr (6) In the formula: C _dvr and C _dr are DVR construction cost and demand response cost respectively; 1) DVR construction cost Energy storage DVR is used for complete voltage compensation. Its construction cost includes capacity cost and energy storage system cost. The operation and maintenance cost C _op is set to 5% of the construction cost: In the formula: C _sun and C _eun are the capacity cost and energy storage system cost of DVR respectively, both of which are related to the voltage level; ΔT _Ⅰ is the support time of the energy storage system; It is the compensation capacity of DVR; Based on the complete voltage compensation strategy, the compensation capacity of the DVR for: In the formula: N ₁ is the node set of DVR access park line topology; P _i ^dvr and are the active power and power angle injected into the i-th DVR respectively. The principle is the same as Equation (1); In order to simplify the DVR planning problem, the average sag voltage can be obtained based on historical voltage data. and average sag angle Treating it as a known quantity, formula (1) can be rewritten as: In the formula: The i-th DVR is responsible for the compensation power of the j-th sensitive device; N ₂ is the node set of sensitive devices connected to the campus line topology;/> and/> are the active power, voltage and power angle of the jth sensitive equipment respectively; Combining equations (7) to (9), it can be seen that when sensitive equipment is operating normally, and/> tends to the rated value, so it can be increased by increasing/> and/> Come/> becomes smaller, thereby making Pi _dvr smaller and reducing the construction cost of DVR; therefore, when a voltage sag is detected, ^it is raised within a suitable range for a short time/> Make the sag voltage and sag power angle at this time larger than the historical and/> This provides a theoretical basis for reducing DVR construction costs; 2) Demand response cost Park operators obtain direct control of interruptible loads through contract signing. When a voltage sag is detected, the voltage adjustment of sensitive equipment access nodes is achieved by shutting down or adjusting the working conditions of interruptible loads; In the formula: N ₃ is the set of nodes in the park that can interrupt load access; and/> are respectively the power reduction and compensation price of the interruptible load of the k-th node; (5) Optimal configuration model of dynamic voltage restorer taking into account demand response DVR compensation capacity is often benchmarked against the capacity of sensitive equipment, which means that there is no need to pay attention to the campus power network topology and only need to plan the DVR compensation time; the longer the compensation time, the better the effect of stabilizing the process parameters of sensitive equipment, but the construction cost The higher; under the idea of reducing DVR construction costs through demand response, the power network topology must be considered, and the DVR compensation capacity is a decision-making quantity, which is related to the voltage and power angle at sensitive equipment; for this reason, the configuration model is optimized Constraints related to process parameters, demand response constraints, and campus network constraints should be considered; 1) Objective function The planning goal of DVR is constructed using the net present value method. The design objective function is to maximize the net present value of investment, which can take into account voltage quality while ensuring the shortest payback period; In the formula: N _Y is the project cycle year; 2) Constraints related to process parameters By extending the duration of the first stage in Figure 2, the voltage sag that sensitive equipment can ride through in a short time is ensured as follows: 0≤ΔT _Ⅰ ≤ΔT _i ^max (13) In the formula: T _i ^PIO and T _i ^res are the original process immunity time and restart time of the j-th sensitive device respectively; ΔT _i ^max is the upper limit of the compensation time of the i-th DVR; 3) Demand response constraints Mainly the upper and lower bound constraints of interruptible load and 0-1 integer constraints; In the formula: and/> are respectively the previous and next periods of the kth interruptible load;/> It is a 0-1 variable, 1 means calling, 0 means not calling; 4) Campus network constraints The park is usually a radial power network. New energy, park incoming lines and sensitive equipment are all connected to the power network nodes. Each node includes equation constraints (balance constraints and power flow constraints) and voltage upper and lower limit constraints. For For sensitive load access nodes, the upper limit of the voltage constraint is the upper limit of the voltage range allowed by the sensitive equipment during normal operation, and the lower limit is the sum of the lower limit of the voltage range allowed by the sensitive equipment during normal operation and the voltage raised by demand response. This can reduce DVR Energy to overcome voltage sag; in addition, sensitive equipment access nodes also include power angle constraints, whose setting principles are the same as voltage constraints. Equation (15) is the power balance constraint, Equation (16) is the power flow constraint of the network, Equation (17) and Equation (18) is the node voltage constraint, and Equation (19) is the power angle constraint of the sensitive load access node; In the formula: N ₄ and N ₅ are respectively the set of nodes connected to the power grid in the park and the set of all load nodes in the park; Active power injected into the nth park access grid node;/> is the average power of the m-th load node; In the formula: P _x and Q _x are the active and reactive power of node x; U _x is the voltage of node x; G _xy , B _xy and θ _xy are the conductance, susceptance and work between node x and node y respectively. horn; In the formula: U ^L,max and U ^L,min are respectively the upper and lower voltage limits of the m-th non-sensitive equipment access node; In the formula: is the upper limit of the voltage of the access node of the jth sensitive device, which is equal to the upper limit of the allowable voltage of the sensitive device during normal operation;/> is the lower limit of the voltage of the jth sensitive equipment access node, which is equal to the lower limit of the voltage range allowed when the sensitive equipment operates normally/> vs. voltage boosted by demand response/> Sum; In the formula: is the upper limit of the power angle of the jth sensitive device access node, which is equal to the upper limit of the power angle allowed when the sensitive device is operating normally;/> is the lower limit of the power angle of the jth sensitive device access node, which is equal to the lower limit of the power angle range allowed when the sensitive device is operating normally/> Rising power from demand response/> Sum; (6) Nested segmentation algorithm model solution The optimal configuration model of the dynamic voltage restorer taking into account demand response is a mixed integer nonlinear non-convex model, which can be solved by the nested segmentation algorithm. The reason is that the nested segmentation algorithm has global convergence characteristics and avoids falling into the local optimal solution. And affect the DVR construction cost.