EP4022734A1

EP4022734A1 - Method for controlling electrical power flows

Info

Publication number: EP4022734A1
Application number: EP20761187.2A
Authority: EP
Inventors: Mathias Buenemann
Original assignee: SMA Solar Technology AG
Current assignee: SMA Solar Technology AG
Priority date: 2019-08-26
Filing date: 2020-08-20
Publication date: 2022-07-06
Also published as: WO2021037673A1; DE102019122867A1

Abstract

The invention relates to a method for controlling electrical power flows in a multi-phase electrical sub-network (10), the sub-network (10) being connected to a superordinate network (20) by means of a network connection point (11), a plurality of actuators (12-16) being connected to the sub-network (10) on a single phase or on multiple phases and exchanging electrical power (Pi) with the sub-network (10), a specification for electrical power (PNAP) flowing through the network connection point (11) being satisfied by controlling the actuators (12-16), said specification being linked to a superordinate control objective. The method comprises the following steps: determining a target power (PNAP,soll) for satisfying the specification; determining a present power difference (ΔΡΝΑΡ) between the target power (PNAP,soll) and a present measured power (PNAP,ist) at the network connection point (11); specifying a weighting (Gi) of the power difference (ΔΡΝΑΡ) for each actuator (12-16); specifying a significance (Wj) for each phase (j) of the sub-network (10); controlling the actuators (12-16) on the basis of phase-resolved exchange power specifications (L1, L2, L3), which are determined according to the weightings (Gi) and the significances (Wj). The sum of all the exchange power specifications (L1, L2, L3) corresponds to the power difference (ΔΡΝΑΡ).

Description

METHOD FOR REGULATING ELECTRICAL POWER FLOWS

TECHNICAL FIELD OF THE INVENTION

The invention relates to a method for regulating electrical power flows in a multi-phase electrical sub-network that is connected to a higher-level supply network via a connection point.

STATE OF THE ART

A multi-phase electrical sub-network, for example a house network, a network section of a distribution network for supplying an extensive property or a distribution network for supplying a locality, is regularly connected via a node to a higher-level distribution network or transmission network. An active electrical power that flows via this node, for example via a network connection point, depends essentially on the behavior of the electrical devices in the sub-network. Different electrical devices can be connected to the sub-network, in particular energy generation systems, energy consumers and energy stores.

The heat output at the network connection point can be controlled within certain limits by influencing the electrical equipment. Electrical devices, whose power consumption or output can be adjusted (hereinafter referred to as "actuators") and which are electrically connected to the subnetwork, can be used as manipulated variables in the context of a control or regulation structure in order to increase the output at the network connection point adjust or regulate. The subnetwork can in particular include actuators such as a photovoltaic system (PV system), a battery storage system, an electric car and / or an electric heat generator, that is to say a heat pump and / or a heating element.

The exact capabilities of the individual actuators, ie the value range of the currently adjustable heat output, may not be known in advance, but can only be recorded indirectly via the effect of a switching action of an actuator on the heat output at the network connection point. For example, if the heat output at the network connection point is to be reduced because it exceeds a specified target value (so-called peak load shaving), the individual actuators in the sub-network can be switched on or off gradually until the heat output is below the target value. In known methods, for example, a setpoint value for a change in the active power is transferred to a cascade of actuators. The setpoint can include, for example, a reduction in the active power at the grid connection point. This setpoint can first be transferred to a PV inverter or its control unit, which can increase the fed-in power and thus lower the load at the grid connection point. If the available power reserve of the PV inverter (or the connected PV generator) is less than the setpoint, i.e. not sufficient to achieve the required change in active power at the grid connection point, the remaining change in power can be transferred to a first e-car as the remaining setpoint be specified, which reduces its charging power within the scope of its possibilities; If this is still not enough to achieve the required change in active power at the grid connection point, the updated residual setpoint can be transferred to a second electric car, a heating element and / or a battery, all of which try to do their part to contribute to achieving the desired change in active power. At the end of this cascade, the sum of the changes in power of the actuators should at least correspond to the desired change AP in the active power at the grid connection point.

Such a cascaded control can be refined by different weighting of the individual actuators, provided that these actuators can not only be switched on and off, but can also make a specifiable change in their active power. It can make sense to integrate several (similar) actuators into the control system at the same time, but to different degrees, i.e. with different weighting. For example, the memory of a first electric car can be charged with the maximum possible active power, while the memory of a second electric car is not charged at all; alternatively, both e-cars could be charged at “half power”.

Such a weighting of the actuators that can be influenced can be specified, for example, by a higher-level energy management system. User specifications can be taken into account, for example the urgency of charging a storage device in an electric car or supplying a consumer. Any further electrical storage devices can also participate in the regulation, with different boundary conditions being relevant for different storage types, which depend on the intended use of the stored electrical power. For example, a battery can participate in the above-mentioned peak load shaving by emitting electrical power and thus reducing the active electrical power flowing into the sub-network via the network connection point, although it should be noted that energy required for other purposes should remain in the battery, for example for later extraction to avoid active power consumption via the grid connection point, ie in particular to increase self-consumption. In addition, several battery storage systems can be prioritized against one another, especially if they are assigned to different actuators within the subnetwork independently of one another. For example, if the sub-network has several PV systems that are spatially oriented differently and each coupled with its own battery storage system, it can make sense in the mornings to involve the battery of a PV system facing west more strongly in peak load shaving than the battery of a PV system. Facility with east orientation, as the former can be charged with higher power in the afternoon due to the relatively stronger solar radiation.

Simultaneous use and weighting of the actuators to achieve a control goal is therefore particularly advantageous if the actuators are required for another purpose that deviates from or even contradicts the control goal, for example the battery of the electric car for driving, a stationary battery to (later) increase self-consumption, a heat generator and / or a heat storage device to provide heat, etc.

A disadvantage of such methods is that no further actuators are addressed as soon as the setpoint is reached. Therefore, actuators called up first contribute with their full capacity to achieving the setpoint, which in the case of consumers regularly means a complete shutdown, while all other actuators can continue their operation unaffected. This procedure does not result in optimal behavior with regard to the actual, primary purpose of the actuators used.

OBJECT OF THE INVENTION

The invention is based on the object of providing a method for regulating power flows of electrical power in a multiphase electrical sub-network, with which the real power exchanged with the sub-network can be reliably regulated, the actuators connected in the sub-network within the scope of their technical possibilities, taking into account their primary Operational purpose and further user specifications are optimally operated and at the same time optimally contribute to the regulation of the total power exchanged with the subnetwork.

SOLUTION

The object is achieved by a method with the features of claim 1. Preferred embodiments are defined in the dependent claims. DESCRIPTION OF THE INVENTION

In a method for regulating power flows of electrical power in a multi-phase electrical sub-network, the sub-network is connected to a higher-level network via a network connection point. A plurality of actuators is connected to the sub-network in one or more phases and exchanges electrical power with the sub-network. By controlling the actuators, a specification linked to a higher-level control target for electrical power flowing via the network connection point is met. In this case, a target power to meet the specification and a current difference in power between the target power and a current actual power at the network connection point are determined. Furthermore, a momentary weighting of the differential power per actuator and a momentary weighting per phase of the multiphase sub-network are specified. The actuators are then controlled on the basis of phase-resolved exchange performance specifications, the exchange performance specifications being determined as a function of the weightings and the values, and the sum of the exchange performance specifications corresponding to the differential performance.

By means of this method, in particular an actuator that is connected in multiple phases and can be operated asymmetrically can thus be controlled in such a way that power is actually exchanged with the sub-network in a targeted manner. This can be used to avoid overloading individual phases and to minimize unbalanced loads.

A higher-level control goal can be the maximization of self-consumption of electrical energy. In the case of a multi-phase sub-network, the calculation of this self-consumption relates to the sum of the electrical power flowing over the individual phases of the network connection point. The superordinate regulation target can include a target value for a heat output at the network connection point, so that the target output correlates with the target value. As an alternative or in addition, the regulation objective can include a limitation of the active power and / or a limitation of the unbalanced load at the grid connection point.

In one embodiment of the method, the actuators can independently set their performance based on the phase-resolved exchange performance specifications or can be allocated a performance preset using the phase-resolved exchange performance specifications from an additional device connected upstream of the respective actuator. As a result, the method can be used flexibly for a wide variety of actuators, the subnetwork being able to include, in particular, single-phase connected actuators and multi-phase connected actuators. In embodiments of the method, the actuators can comprise a renewable energy source, in particular a PV system, and an energy store, in particular a battery, and alternatively or additionally an electric car and / or an electric heat generator, in particular a heater. The sub-network itself can be a house network, a network section of a distribution network for supplying an extensive property or a distribution network for supplying a locality or a municipality.

In one embodiment of the method, the actuators have a respective primary benefit which is taken into account when specifying the weighting of the target power per actuator. The primary benefit is the actual operational purpose of the actuator; For example, a heat generator is primarily set up to generate heat and pursues the primary goal of making a requested amount of heat available at the right time, while an electric car is primarily set up for driving and pursues the primary goal of ensuring a sufficient range. The primary benefit can in particular include a minimum reference power of an actuator, for example in that charging an electric car requires a minimum charging power, or in that a compressor of a cooling device requires a minimum start-up power.

In the procedure, the values per phase can represent the relative resilience of the individual phases. Taking into account the power currently exchanged over the individual phases at the grid connection point, it can be identified within the framework of the procedure which power reserves exist in which phases, and this knowledge can be used to redistribute the power over the individual phases.

BRIEF DESCRIPTION OF THE FIGURES

In the following, the invention is further explained and described with reference to the embodiments shown in the figures.

1 shows a multi-phase sub-network with a connection to a higher-level network, and FIG. 2 shows a method according to the invention for regulating electrical power flows in a multi-phase electrical sub-network.

FIGURE DESCRIPTION

1 shows a multiphase electrical sub-network 10 which is connected to a higher-level network 20 via a network connection point 11. The network 20 is an electrical alternating voltage network and can in particular comprise a distribution network or a transmission network. The sub-network 10 can in particular a house network, a network section of a Distribution network to supply an extensive property or a distribution network to supply a locality or a municipality.

Within the sub-network 10, various actuators 12-16 are arranged, which draw electrical power from the network 20 or feed it into the network 20 via the network connection point 11 and corresponding power lines. In particular, a load 12, for example a commercially available consumer such as a refrigerator or a washing machine, an energy generation system, here in particular a photovoltaic system (PV) 13, an electrical energy storage device, here in particular a battery 14, an electrically operated heater, are in the subnetwork 10 15, for example a heat pump or a heating rod, and an electric car 16 are connected.

The sub-network 10 is designed to be multi-phase, so that the network connection point 11 and the connections to the actuators 12-16 basically also comprise several phase conductors. The individual actuators 12-16 can be connected to sub-network 10 in single-phase or multiple-phase fashion, as required.

The subnetwork 10 comprises an energy management system 30, for example a computer or a controller. The energy management system 30 records the electrical power at the network connection point 11 by means of suitable measuring devices (not shown) and generates control commands which are transmitted to the actuators 12-16 via appropriate communication connections (dashed lines). The control commands include, in particular, power setpoints which are each to be set individually by the actuators 12-16. The actuators 12-16 themselves can be equipped with receivers for the control commands and suitable control devices for setting the respective power setpoints. Alternatively, additional devices (not shown) can be provided which are connected upstream of the actuators 12-16, receive control commands and set an electrical power allocated to or removed from the actuators 12-16 as a function of the control commands; Such additional devices can be designed as simple (remotely) switchable sockets for smaller loads or as powerful electrical converters, in particular as (bidirectional and / or multi-phase) inverters, for larger storage units.

Some of the actuators 12-16, in particular the PV system 12 and the battery 14, can function as an energy source and feed single-phase or multi-phase electrical power into the sub-network 10. Due to the multi-phase design of sub-network 10 and network connection point 11, situations can arise in which the sum of the electrical power in the individual phases at network connection point 11 is equal to or close to zero, so that effectively no active power is exchanged between sub-network 10 and network 20. At the same time, however, there can be a significant unbalanced load by significantly different Power with opposite power flow direction flow over the individual phases at the grid connection point 11. For example, the PV system 12 can be connected as a single-phase energy source to a first phase of the sub-network 10 and feed in electrical power which, however, due to the lack of an energy sink, is not taken from this first phase within the sub-network 10 and via the network connection point 11 to the higher-level network 20 flows away, while an energy sink, for example the load 12, is connected to a second phase of the sub-network and, in the absence of an energy source, has to draw electrical power from the higher-level network 20 via the network connection point 11 in this second phase.

On the one hand, such unbalanced loads in conventional sub-networks 10 can be viewed as uncritical if a balancing electricity meter should be arranged at the network connection point 11, which only determines the total power over all phases and, if necessary, bills an operator of sub-network 10. On the other hand, it does not prove to be very expedient to minimize the sum of the electrical power in the individual phases at the network connection point 11 in such a way that the absolute difference between the powers on the individual phases and thus the asymmetrical load is increased even further. For example, if the power of the PV system 13 fed into a first phase as an energy source is higher than the power drawn from a second phase by the load 12 as an energy sink, i.e. a total of power flows from the sub-network 10 into the higher-level network 20, could the drawn power of the load 12 on the second phase can be increased. This would allow the total power to be minimized, but at the same time the unbalanced load would also be increased, possibly even beyond a normatively permitted level.

Furthermore, individual actuators 12-16 can be connected to sub-network 10 in multiple phases and can themselves act as an unbalanced load, i.e. exchange asymmetrical electrical power with the individual phases of sub-network 10. Such actuators can act as energy sources, in particular the PV system 13 or the battery 14, or represent energy sinks, in particular the load 12, the heater 15 or the electric car 16. In addition, individual actuators can also be operated bidirectionally, ie after Take electrical power from the sub-network in one or more phases or feed it into the sub-network.

The energy management system 30 can know both the specific unbalanced load capabilities of the multi-phase connected actuators and the phase actually used by the single-phase connected loads, for example by including or using a method for identifying the phase assignment of an electrical device.

Fig. 2 shows an embodiment of a method for regulating power flows of electrical power in a polyphase electrical sub-network 10, which is via a Network connection point 11 is connected to a higher-level network 20. _{A nominal electrical power PNAP.S O} II is intended to flow from or into the higher-level network 20 via the network connection point 11. The setpoint power PNAP.S _O II represents a specification of a higher-level control target, which includes, for example, a minimization of the electrical energy drawn from the higher-level network 20. In this respect, the specification of the regulation goal can be a minimization of the electrical power PNAP currently drawn via the network connection point 11, so that the overriding regulation goal in this example can be represented by a setpoint power PNAP.S _O II equal to zero.

In a detection section 31 of the method, the setpoint power PNAP.S _O II is compared with an actual electrical power PNAP, is compared at the network connection point 11, and a difference power DRNAR is formed between the setpoint and actual power. This desired differential power DRNAR is transferred to a control section 32 of the method. By means of an energy management system 30, the control section 32 generates phase-resolved exchange power specifications for the actuators 12-16, which the actuators 12-16 receive and, if possible, implement in an action section 33 of the method.

In order to set the target power PNAP, S _O M, the exchange powers P, of several of the actuators 12-16 in the sub-network 10 are influenced on the basis of the control section 32 as a function of a higher-level control objective, in particular by adding individual exchange power specifications DR to these actuators 12-16 or whose controls or ballasts are transmitted. An exchange power specification DR can specify an absolute value for the exchange power P, one of the actuators 12-16 or also a change in the exchange power P, one of the actuators 12-16.

To determine suitable exchange performance specifications DR, the actuators 12-16 are each assigned individual weightings Gi with values between 0 and 1. The weightings Gi can be normalized in such a way that their sum is equal to one. The weightings can be calculated specifically by the energy management system 30 and applied to the differential power DRNAR by means of a distributor 34. From this, weighted output specifications 12a-16a for the actuators 12-16 are calculated by multiplying the differential power DRNAR necessary for setting the setpoint output PNAP.SOII by the weighting G assigned to the respective actuators 12-16.

Phase factors 35 are applied to the performance specifications 12a-16a. For this purpose, values W for the individual phases of the sub-network 30 are specified by the energy management system 30. The weights W _j include values between 0 and 1, it being possible for the sum of the weights W _{j to be} equal to one. Specifically, for example, a phase j in which predominantly non-controllable electrical loads are connected, a lower value W _j than the other phases are assigned.

The performance specifications 12a-16a are multiplied by a set of phase factors 35 applicable to the respective actuator 12-16. This results in phase-resolved exchange performance specifications for the actuators 12-16, which are designated redundantly with L1, L2, L3 in FIG. 2 for the sake of clarity. The actuators 12-16 in the action section 33 are controlled with these phase-resolved exchange performance specifications L1, L2, L3.

When determining the exchange performance specifications DR for the actuators 12-16, it is thus taken into account which phase j has which value W _j . For this purpose, a differential power DR _NA R at the network connection point 11, which is to be minimized by the exchange power specifications DR, for example, is divided between the actuators 12-16 by multiplying the differential power DR _NA R with the weightings G and based on the weightings W _j on the individual phases j is distributed.

For an actuator that is connected in multiple phases and can be operated asymmetrically, for example for the battery 14 or the electric car 16, the replacement power specification consists of three values L1, L2, L3, in that the corresponding power specification 14a or 16a is multiplied _{by the values W j;} The sum of the values L1, L2, L3 for the respective actuators 14 or 16 can essentially correspond to the respective output specification 14a or 16a. The resulting phase-resolved exchange power specifications are transmitted to the actuators 14, 16, so that they exchange electrical power with the sub-network correspondingly asymmetrically.

Specifically, for example, a phase j with a low value W _j , from which a relatively high power is already drawn, is less loaded by the asymmetrically operated electric car 16 than a phase j with a high value W _j , which is still relatively lightly loaded. This avoids an overload on phase j with low significance W _j and at the same time minimizes an unbalanced load at the network connection point NAP. In this example, the value represents the relative load capacity of the individual phases, ie their possible contribution to an increase in active power. In principle, many other definitions or derivations for the values W _j and the use of the phase factors 35 are conceivable, with the specific values also being able to depend in particular on the overriding control objective.

For the single-phase connected actuators, for example the load 12 or the PV system 13, the phase-resolved exchange power specifications each consist of only one value. This value can also result from the multiplication of the corresponding Power specification 12a or 13a with the value W _{j of} the respective phase j to which the load 12 or the PV system 13 is connected. The exchange power specification is all the smaller, the lower the value W, of that phase j to which the actuator is connected. As a result, a phase j with a low value W _j , from which, for example, a lot of electrical power is already drawn by the uncontrollable loads, is only used to a small extent to compensate for the differential power DRNAR. Conversely, those single-phase actuators can preferably contribute to the differential power DRNAR which are connected to phases j with the highest valency W _j ; In the above example, these are precisely the phases j from which the least amount of electrical power is drawn by the uncontrollable loads.

The actuators are now instructed to implement the phase-resolved exchange performance specifications L1, L2, L3 by in particular changing the exchange performance P 1 of the actuators 12-16 accordingly. The measured values at the network connection point 11 are then used to evaluate the extent to which the actual power P _NAP .i _st now corresponds to the setpoint power PNAP.SOII. If the differential power DRNAR continues to have a value not equal to zero, the described method can be iteratively run through again in order to regulate the remaining difference between the actual power and the target power by means of further optimized exchange power specifications.

In one embodiment, it can be determined to what extent the actuators 12-16 have actually implemented the exchange performance specification instructed to them. This determination can take place by measuring the exchange powers P 1 of the actuators 12-16, this measurement being carried out by the actuators 12-16 themselves and being made available to a control unit, for example the energy management system 30, in a communicative manner. In particular, if one or more of the actuators 12-16 does not provide the required (phase-resolved) exchange performance specification, the weightings G of these actuators that do not or could not provide the required exchange performance P can be set to 0 in one iteration of the method. The remaining weights are re-normalized and the remaining differential power DRNAR is distributed to the remaining actuators. This iteration is continued until the actual output PNAP ISI corresponds to the setpoint output PNAP.SOII at the connection point and thus the specification that is linked to the higher-level control objective is met.

In further embodiments, the weighting can take into account already known boundary conditions of individual actuators, such as, for example, predetermined minimum powers of certain actuators. This ensures that the corresponding actuators are not placed in an invalid operating state, for example in that an actuator receives a power specification that is lower than the respective predetermined minimum power. In further embodiments, instead of the (balanced) active power at the network connection point, other variables can also be regulated, such as the active power at critical points in the sub-network or phase-resolved active and / or apparent powers.

REFERENCE CHARACTERISTICS LIST Sub-network network connection point -16 actuators a-16a Power specification network Energy management system Acquisition section Control section Action section Distributor phase factors

Claims

PATENT CLAIMS

1. A method for regulating electrical power flows in a multi-phase electrical sub-network (10), the sub-network (10) being connected to a higher-level network (20) via a network connection point (11) and wherein a plurality of actuators (12-16) are single-phase or are connected in multiple phases to the sub-network (10) and exchange electrical power (P,) with the sub-network (10), whereby, by controlling the actuators (12-16), a specification linked to a higher-level control target for a network connection point (11) flowing electrical power (PNAP) is met, the method comprising the following steps:

- Determination of a target performance (PNAP.SOII) to meet the specification,

- Determination of a momentary differential power (DRNAR) between the target power (PNAP.SOII) and a momentary actual power (PNAP, actual) at the grid connection point (1 1),

- Specifying a weighting (Gi) of the differential power (DRNAR) per actuator (12-16),

- Presetting a value (W _j ) per phase (j) of the sub-network (10),

- Control of the actuators (12-16) on the basis of phase-resolved exchange performance specifications (L1, L2, L3), which are determined as a function of the weightings (Gi) and the values (W _j ), the sum of all exchange performance specifications (L1, L2, L3) corresponds to the differential power (DR _{N AR).}

2. The method according to claim 1, wherein the superordinate control target comprises a setpoint value for an active power at the network connection point (11), so that the setpoint power (PNAP.SOII) correlates with the setpoint value.

3. The method according to claim 1 or 2, wherein the control objective comprises a limitation of the active power at the network connection point (11).

4. The method according to any one of the preceding claims, wherein the regulation target alternatively or additionally comprises a limitation of the unbalanced load at the network connection point (11).

5. The method according to any one of the preceding claims, wherein the actuators (12-16) constantly adjust their performance based on the phase-resolved exchange performance specifications (L1, L2, L3) or a performance of a specified using the phase-resolved exchange performance specifications (L1, L2, L3) get assigned additional device upstream of the respective actuator (12-16).

6. The method according to any one of the preceding claims, wherein the sub-network comprises single-phase connected actuators (12, 13, 15) and multi-phase connected actuators (14, 16).

7. The method according to any one of the preceding claims, wherein the actuators (12-16) comprise a renewable energy source, in particular a PV system (13), and an energy store, in particular a battery (14).

8. The method according to any one of the preceding claims, wherein the actuators (12-16) comprise an electric car (16) and / or an electric heat generator, in particular a heater (15).

9. The method according to any one of the preceding claims, wherein the sub-network (10) is a house network, a network section of a distribution network for supplying an extensive property or a distribution network for supplying a locality or a municipality.

10. The method according to any one of the preceding claims, wherein the actuators (12-16) have a respective primary benefit which is _{taken into account when specifying the weighting (G,) of the target power (P NA} P. _SO II) per actuator (12-16) , wherein the primary benefit includes in particular a minimum reference power of an actuator (12-16).

11. The method according to any one of the preceding claims, wherein the values (W _j ) represent the relative resilience of the individual phases (j).