BR112020005181A2 - electricity distribution network - Google Patents

Abstract

An electricity distribution network comprises at least two current feeders; at least two loads, each associated with one of the respective feeders; at least one module electrically connected to two feeders and including: a bidirectional auxiliary converter; DC bus, including a capacitor; and a bidirectional balancing converter connected in parallel. The module also includes means to change the current and voltage between the feeders and the bidirectional auxiliary converter and a differential electrical connection between the two feeders and connected in series with the bidirectional balancing converter and a controller configured to control at least one parameter of an electric current flowing through or from each module, the voltage across or from each module being related to the maximum difference in voltage between two feeders.

Description

“ELECTRICITY DISTRIBUTION NETWORK” Domain of the Invention

[0001] The present invention relates to electricity distribution networks and, in particular, to the balancing of the loads received by different parts of such networks. History of the Invention

[0002] There is a growing impulse towards distributed energy generation; for example, many buildings are now equipped with solar energy systems that generate modest amounts of energy and are generally returned to the distribution network. Small-scale wind power systems work in a similar way. However, the electricity distribution network in many countries was designed to distribute centrally generated electricity to several dispersed users, not for these users to generate electricity to return to the distribution network.

[0003] There is an increasing need to adapt the electricity distribution networks to accommodate the generation of distributed electricity.

[0004] Electricity distribution networks comprise numerous feeders. As the number of power generation facilities on the network increases, the load on the feeders to which these power generation facilities are connected increases. This is compounded in the case of renewable electricity sources, whose energy generation is unpredictable. Where there are many solar installations, even when each installation is small, on a sunny day, the feeder to which these solar installations are connected can be significantly overloaded.

[0005] A feeder can also become overloaded when there is a significant amount of consumption by users connected to a specific feeder. As more equipment is electrified, with vehicles being an excellent example, electricity is likely to replace other forms of energy, thus increasing the demands placed on individual networks and feeders.

[0006] With current network arrangements, the load on an electrical feeder can be changed by changing the configuration of feeders in a network from a radial configuration to a mesh configuration, by tying the ends of neighboring feeders directly using a mechanical breaker bus. However, several factors can hinder the use of mechanical bus circuit breakers. For example, the voltage difference between the feeders, the length of the feeders, the total load on a feeder, the failure levels in the feeders, the phase imbalances in which the feeder is a three-phase feeder, in addition to the load distribution along of a feeder.

[0007] In some cases, electronic power solutions have been used to change the additional capacity of an adjacent feeder to an overloaded feeder. When these power electronics are provided at the same location as a bus circuit breaker, the arrangement is commonly known as Soft Open Point.

[0008] The power electronics currently used in Soft Open Points are capable of handling the complete line voltage. For low voltage applications, the electronic components used in the Soft Open Points are bulky. For medium and high voltage parts of electricity distribution networks, the size of electronic energy systems would make their use unlikely.

[0009] The Applicant has developed an active balancing conversion system, illustrated in Figure 1, to be used in low voltage networks. The Soft Open Point illustrated in Figure 1 is located on a network comprising a three-phase high voltage source to which two transformers are connected (which reduce the voltage to a low voltage and which can be considered as feeders), with a load being connected to each of the transformers. Each of the transformers is also connected to a respective bidirectional converter. The bidirectional converters are connected to a C1 capacitor that forms a DC bus. Bidirectional converters and capacitor C1 are rated to transfer the maximum unbalanced load between the two transformers.

[0010] The DC bus must exceed the peak voltage of the line and the maximum balancing current can be equal to the nominal current of the line and, therefore, each active converter must have the same power as one of the low voltage distribution transformers. If the same arrangement were used to share the load between medium and high voltage networks, the physical size of the necessary components would increase and greater energy losses would occur.

[0011] Document DE10103031 describes a system of a high power network that uses two bidirectional converters as modular multilevel converters.

[0012] The document US20160141876 describes an alternative arm converter to be used in the transmission of high voltage direct current energy and reactive energy compensation and a method to control this alternative arm converter. The alternate arm converter includes a combination of semiconductor switches connected in series and full bridge converter modules connected in series. Serial switches direct the flow of energy from a network branch, while full bridge modules allow multi-level operation.

[0013] The document US2017 / 0141694 describes an energy management system using a low voltage preload. The low voltage source provides a charging current for electrically isolated batteries.

[0014] The document US2013 / 0024043 describes a computer implementation method that configures and reconfigures parameters of distribution automation devices that are part of a grid topology.

[0015] Document US2015 / 0314696 describes a method and coordinated control system that can accommodate distributed energy resources and the charging of electric vehicles.

[0016] However, all the solutions mentioned above have disadvantages associated with them. For example, in the provisions described in DE10103031 and US20160141876, bidirectional energy converters are rated with the same power as the feeder, thus limiting their use in high power distribution networks.

[0017] It would be desirable to provide a control system that would provide load balancing between the transformers of the neighboring feeders. This system would allow conventional distribution networks to be improved so that they can deal with the new demands that are being imposed on them. Summary of the Invention

[0018] According to the invention, there is an electricity distribution network comprising: at least two feeders that carry current; at least two loads, each associated with one of the respective feeders; at least one module electrically connected to two feeders and including: a bidirectional auxiliary converter; DC bus, including a capacitor; and a bidirectional balancing converter connected in parallel; the module also includes means to change the current and voltage between the feeders and the bidirectional auxiliary converter and a differential electrical connection between the two feeders and connected in series with the bidirectional balancing converter; a controller configured to control at least one parameter of an electric current flowing through or from each module, the voltage across or from each module being related to the maximum voltage difference between two of the feeders.

[0019] Preferably, the bidirectional balancing converter is single-phase.

[0020] Advantageously, the two feeders are three-phase feeders; three modules are connected to the respective phases of the feeders; and the bidirectional auxiliary converter is a three-phase converter.

[0021] The module may comprise a plurality of submodules connected in parallel, each submodule comprising a bidirectional auxiliary converter, a DC bus including a capacitor and a bidirectional balancing converter connected in parallel, with the submodule also including means for changing the current and the voltage between the feeders and the bidirectional auxiliary converter.

[0022] Preferably, a step-down transformer is the means by which the input current and the voltage of the bidirectional auxiliary converter are changed.

[0023] The step-down transformer may comprise a single primary delta with three isolated star-connected secondary ones, each supplying a respective module of the three in a secondary manner.

[0024] The step-down transformer can comprise a single transformer and three isolated high-frequency bidirectional DC / DC converters, each DC / DC converter being associated with a respective of the three phases.

[0025] Preferably, a DC / DC converter is the means by which the input current and the voltage of the bidirectional auxiliary converter are changed.

[0026] The auxiliary converter and the balancing converter can include semiconductor devices with forced switching.

[0027] Forced switching devices can be composed of a semiconductor material, such as silicon carbide.

[0028] Preferably, forced switching devices are selected from the group comprising: bipolar isolated port transistors (IGBTs), integrated port switched thyristors (GTOs) and metal oxide semiconductor field effect transistors (MOSFETs ).

[0029] Preferably, the auxiliary converter and the balancing converter are configured to operate at frequencies up to 100 kHz.

[0030] Advantageously, the electrical connection between the two feeders includes a means of detecting the fault and protection condition.

[0031] It is preferable that the means of detecting the fault condition and protection comprise a saturable reactor or a plurality of high voltage semiconductor switches connected in series.

[0032] The controllable parameter can be selected from the group comprising: voltage magnitude, phase angle, active power and reactive power.

[0033] In an embodiment of the invention, the electricity distribution network is configured as a STATCOM compensator and includes a P / Q controller (active power / reactive power) 60.

[0034] During operation, the bidirectional converter can initially operate in the boost mode, charging the bus capacitor 16 for a DC potential greater than the peak supply potential, configuring the P / Q 60 controller so that the parameter P be zero.

[0035] The STATCOM compensator can also comprise a transformer located between the three-phase source and the bidirectional converter.

[0036] Preferably, during operation, reactive energy can be exchanged between the source and the bus capacitor 16 (STATCOM operation), changing the phase angle with the P / Q controller. Brief description of the drawings

[0037] In the drawings, which illustrate the prior art and the preferred embodiments of the invention, serving as examples:

[0038] Figure 1 is a schematic representation of a prior art Soft Open Point arrangement;

[0039] Figure 2 is a schematic representation of a simple load balancing system according to the invention;

[0040] Figure 3 is a schematic representation of a load balancing system according to the invention with a treatment and protection arrangement against failures;

[0041] Figure 4 is a schematic representation of a load balancing system integrated with an electricity distribution network;

[0042] Figure 5 illustrates balancing voltages and currents for the load balancing system illustrated in Figure 3;

[0043] Figure 6 is a schematic representation of a load balancing system according to the invention for connection to more than two feeders;

[0044] Figure 7 is a schematic representation of an alternative load balancing system according to the invention for connection to more than two feeders;

[0045] Figure 8 illustrates a part of the load balancing system including a STATCOM compensator;

[0046] Figure 9 illustrates a part of the load balancing system including a STATCOM compensator;

[0047] Figure 10 is a circuit diagram of the configuration illustrated in Figure 8; and

[0048] Figure 11 is a circuit diagram illustrating a controller for the load balancing system of the invention. Detailed Description of the Preferred Embodiments

[0049] Referring now to Figure 2, it is possible to see a part of a three-phase electricity distribution network 1. The network comprises a high voltage feeder 2 whose output is divided into three phases 3a, 3b and 3c. The three phases 3a to 3c are connected to medium voltage power transformers 4, 5, the power transformers with three-phase outputs 4a-4c and 5a-5c. Loads 6, 7 are connected to feeder transformers 4, 5, respectively.

[0050] So that the loads 6, 7 can be balanced through the feeder transformers, 4,5 the respective pairs of phases 4a, 5a, 4b, 5b, 4c, 5c are connected to each other by the modules A-C. Each of the AC modules is connected to the output phases 5a-5c of the feeder transformer 5 by the respective lowering auxiliary transformers 9, 10, 11, each of which is part of one of the AC modules and to the output phases 4a-4c of the transformer feeder 4 by the LC circuits 12, 13, 14, each of which is part of one of the AC modules and comprises an inductor 12a, 13a, 14a and a capacitor 12b, 13b, 14b. Each capacitor 12b, 13b, 14b is connected on the side of the module to one of the respective output phases 5a to 5c of the feeder transformer 5. The inductive side of each capacitor 12b, 13b, 14b is connected to one of the output phases 4a-4c corresponding to feeder transformer 4, that is, for module A, one side of capacitor 12b is connected to output phase 5a of feeder transformer 5 and the other side of capacitor 12b is connected to output phase 4a of feeder transformer 4.

[0051] In Figure 2, only module A is shown in detail. However, each of the A-C modules is the same, except for the output phases of the feeder transformers 4, 5 to which they are connected.

[0052] Module A comprises a three-phase bidirectional converter (auxiliary converter) 15 connected in parallel with a capacitor 16, which forms a DC bus and a single-phase bidirectional converter (balancing converter)

17. The DC bus voltage marginally exceeds the voltage difference between the corresponding phases of the feeder transformers 4, 5. If the voltage difference between the corresponding phases of the feeder transformers 4, 5 does not exceed 12% of the peak voltage of the feeder system line, the DC bus will be around 1.5kV in an 11kV medium voltage system. The DC bus voltage supplies the bidirectional single-phase converter 17 which increases or decreases the differential voltage between the corresponding phases 4a-4c, 5a-5c to supply a balancing current between the phases.

[0053] In Figure 2, each module is shown as comprising its own step down transformer 9-11. However, these could be replaced by a single transformer using a configuration comprising a single delta primary coil with three isolated star-connected secondary coils, each secondary coil supplying a module. Alternatively, the separate step-down transformers can be replaced by a single transformer that powers three isolated high-frequency bidirectional AC / DC converters, each feeding one of the balancing modules.

[0054] In a low voltage system, step-down transformers can be omitted and the power for each module derived from isolated AC / DC converters.

[0055] Figure 3 illustrates a more sophisticated arrangement that provides detection and protection from fault conditions. While the configuration illustrated in Figure 2 balances the load on transformers 4, 5 and prevents the circulation of currents, in the event of an earth fault in a feeder, the potential fault current will be twice that of a single transformer. This is because the voltage rating of the devices that make up the single-phase bidirectional converter 17 is not adequate to limit the fault current and would be bypassed in the event of a fault. Figure 3 illustrates two possible configurations for managing the fault condition.

[0056] The first configuration provides a saturable reactor comprising an inductor 21 and a capacitor 22 in series between the capacitor of the LC circuit 12 and the output phase 5a of the feeder transformer 5. During normal operation, inductor 21 and capacitor 22 they are resonant and offer negligible impedance to the alternating balancing current (alternating at 50Hz in the UK). When a fault occurs, inductor 21 saturates and capacitor 22 limits the current flowing between the feeder transformers 4, 5.

[0057] The second configuration provides a full phase blocking circuit 30 comprising a plurality of high voltage IGBTs connected in series 31 between capacitor 12b of the LC circuit 12 and the output phase 5a of the feeder transformer 5.

[0058] IGBTs 31 are in driving mode during normal operation, but are switched off in the event of an overcurrent and provide full phase blocking capability for the circuit, ie when a fault condition is detected, the converter is disconnected . Example

[0059] The configuration illustrated in Figure 3 was modeled using the PLECS energy simulation software with the following system conditions: SIMULATION 1 Nominal feeder voltage - 11kV; Load rated by transformer - 5MVA; Transformer default setting - power transformer 4 1.2%, power transformer 5 2.4%; Loads applied - feeder load 6, 0.4MW, feeder load 7, 9.6MW. SIMULATION 2

[0060] Simulation 2 comprised a new execution of simulation 1 with the inverted load. Results

[0061] The results of simulation 1 and simulation 2 were almost identical. The traces of the balancing voltage and current for simulations 1 and 2 are illustrated in Figure 5. The values for currents and voltages of the feeder transformer, auxiliary transformer load and power dissipation for simulation 1 are shown in the table below:

Unbalanced Parallel balanced without using the control system of Figure 3 Line current of 21A RMS 332A RMS 271A RMS Transformer Feeder 4 Volts LL O / P of 10990V RMS 10900V 10947V RMS Transformer RMS Feeder 4 Line current of 515A RMS 214A RMS 271A RMS Transformer Feeder 5 Volts LL O / P of 10740V RMS 10900V 10828V RMS Transformer RMS Feeder 5 Load of transformer NA NA 58kVA auxiliary 9 Dissipation of module NA NA 6.7kW / Module as simulated

[0062] Figure 4 illustrates an installation in which the load balancing system is integrated with an electricity distribution network. The three-phase vacuum circuit breakers 40, 50 are placed between the three-phase outputs 4a-4c and 5a-5c of the feeder transformers 4, 5 to isolate the A-C balancing modules from the feeder outputs. Instead of using a three-phase vacuum circuit breaker on each side of the A-C modules, three separate single-phase circuit breakers can be used.

[0063] The A-C modules in Figure 4 include two 8 'submodules connected in series. When connecting more than one module in series feeders with greater voltage differences, they can be connected together for balance. When each submodule is specified to handle a voltage difference between the corresponding phases of the feeder of approximately 1.5kV, the use of two submodules will increase the possible voltage difference between the phases of the feeder to 3kV. Each submodule includes a single-phase bidirectional converter 15 and a single-phase bidirectional converter 17, both connected to a DC bus 16. The fault protection for the two submodules 8 'is provided by the phase lock circuit 30 comprising a plurality of pairs of IGBTs 31 , each pair of IGBTs provided with a voltage-dependent resistor 32 in parallel. In the illustrated mode, IGBTs are configured to switch off when the current exceeds 300Arms and / or when the voltage exceeds 1600 volts.

[0064] Sub-circuits 9 ', 12' comprise a voltage-dependent resistor 9a, 12a that limits voltage peaks and transients, voltage transducers 9b, 12b and current transducers 9c, 12c. The function of voltage transducers 9b, 12b and current transducers 9c, 12c is to provide information related to the operating conditions of the converter for the control system. Sub-circuits 9 ', 12' also comprise an inductor 9e, 12e and a capacitor 9d, 12d which together form a filtered low-pass input for bidirectional converters 15, 17, respectively. Low-pass filters prevent the transfer of high-frequency noise from the auxiliary transformer 9. In fact, the low-pass filter removes a high-frequency carrier signal from the sinusoidal output of the single-phase converter 17. The high-frequency carrier signal is introduced during pulse width modulation of a signal derived from the DC 16 bus.

[0065] Figures 6 and 7 illustrate alternative arrangements to balance three (or more) feeders A, B and C. In Figure 6, the three feeders A, B and C are interconnected by two modules D, E. The modules D, And they include auxiliary converters 15 and balancing converters 17 and a DC bus capacitor 16.

[0066] Figure 8 illustrates a part of a module configured as a STATCOM compensator and includes a P / Q controller (active power / reactive power) 60. The bidirectional converter initially in impulse mode charges the bus capacitor 16 to a potential DC higher than the peak supply potential, configuring the P / Q 60 controller so that the P parameter is zero, that there is no active energy exchange and the Q parameter has an initial or delayed value. Reactive power can be exchanged between the three-phase source and the bus capacitor within the limits of the capacity of the inverter, the input inductor and the capacitor current.

[0067] Figure 9 illustrates a part of a module configured as a STATCOM compensator similar to that shown in Figure 8, but with the addition of a transformer 70 between the three-phase supply and the bidirectional converter 17 that simply changes the operating voltage levels of the auxiliary converter.

[0068] Figure 10 is a circuit diagram corresponding to the part of the module illustrated in Figure 8. The auxiliary converter 15 comprises six semiconductor switches 15 '. The DC 16 bus capacitor is charged with a voltage that exceeds the peak value of the three-phase source. To transfer current to capacitor 16 of the source, the six semiconductor switches 15 'act as boost converters. To transfer current from capacitor 16 to the source, semiconductor switches 15 'act as buck converters (or inverters). Reactive power can be exchanged between the source and the bus capacitor 16 (STATCOM operation) by changing the phase angle with controller 60. Note, controller 60 corresponds to control elements 104, 105 described below with reference to Figure 11 .

[0069] Figure 11 illustrates a controller operationally connected to the active balance converter illustrated in Figure 3. The controller causes the active balance converter to operate in two modes, a standby mode and a current control mode.

[0070] In standby mode, the two interconnected feeders 4, 5 are monitored continuously, measuring the current and voltage of each phase of the feeder and calculating the energy flow. If the energy flowing through each feeder 4, 5 does not exceed a PREF power limit value, the active balancing converter will remain in standby mode, that is, the current will not flow between the feeders 4, 5.

[0071] If the power flowing through one of the feeders exceeds PREF, then the current control mode will be activated.

The current controller 100 comprises a current reference calculator 101 that receives input currents from the current transducer 102, 102 ', each associated with one of the phases of the two feeder transformers 4, 5 (note that the current transducers current 102, 102 'are shown for only one of the three phases of feeders 4, 5 although, in practice, each phase would be provided with a current transducer).

[0073] When the current control mode is initiated, the energy is exchanged between the feeders 4, 5 by switching the auxiliary converter 15 and the balancing converter 17.

[0074] Controller 100 controls auxiliary converter 15 as follows:

[0075] The DC link voltage (which is the voltage across capacitor 16) is measured by the voltage transducer 103 and compared to a defined value VdcRef (for example, 1.5kV) on the DC voltage regulator 104. The output of the DC voltage regulator is a reference voltage waveform. If the measured voltage deviates from the set value VdcRef, the DC voltage regulator 104, which may consist of an integral proportional controller (PI), will emit a reference voltage waveform with an amplitude proportional to the voltage error (Vmeasured - VdcRef) This reference voltage waveform is compared on pulse width modulator 105 to a high frequency (> 5kHz) sawtooth modulation waveform that produces a working relationship that switches the auxiliary converter switches 15. Increasing the working ratio results in the time that capacitor 16 is connected to the feeder being increased and controls which switch (auxiliary converter 15 can comprise a plurality of switches 15 ', as shown in Figure 10) of the auxiliary converter is on and off and directs the current in the change of direction or direction of discharge through capacitor 16. This means that the pulse width modulator 105 controls both the service rate (the period of charge or discharge of capacitor 16) as to the direction of the current (up or down on capacitor 16) and, in doing so, increases or decreases the amplitude of the DC link voltage, to maintain it regulated around the set value VdcRef.

[0076] Controller 100 controls balancing converter 17 as follows:

[0077] Currents measured by current transducers 102, 102 'and voltages measured by voltage transducers 103, 103' (note - each phase of each feeder would be supplied with current and voltage transducers) are used to calculate the energy flow at each stage of feeders 4,

5. These values are compared with a reference value defined on a current reference calculator 101 that generates an error signal. This errocurrent signal forms an input for current limiter 107. Current limiter 107 checks whether the errocurrent signal is within the current limitation of the balance converter 17 in current limit block 107. If the errocurrent signal is within of the aforementioned current limitation, it is used as an input for current controllers 108, 109 and 110, together with the voltage difference generator output with voltage difference 111 to calculate a VREF reference voltage waveform. This waveform can be calculated for the 50Hz nominal power reference and also some higher harmonic components can be extracted from the 50Hz waveform using a 112, 113 phase locking loop, providing inputs to the shape generator. voltage difference wave 111 in order to calculate a reference voltage in each of the harmonic reference frames of interest.

[0078] The voltage reference outputs generated from current controllers 108 to 110 are then added together to produce a single 50 Hz reference sinusoidal voltage waveform with the overlapping harmonic components that the controller was designed to compensate for.

[0079] This waveform of the reference voltage is then compared on the pulse width modulator 106 with a high frequency (> 5kHz) sawtooth modulation signal that generates the service rate for each device in the balancing converter 17 and selects the devices in order to control the flow of energy in the required direction. The service charge generated determines the duration for which capacitor 16 appears to be connected through the feeders (charging and discharging), and the choice of switches determines which polarity of the DC link voltage appears on the feeders 4,

5. If capacitor 16 discharges through the balancing converter, it charges back through the auxiliary converter and vice versa, so that its voltage is regulated around VdcRef during the current control period.

[0080] The electric power distribution network of the invention allows the loads to be shared between the feeders. Reactive energy can be extracted from one feeder and fed into the corresponding phase from another feeder. The device can also be configured to provide STATCOM compensation. This is achieved without subjecting the components that connect the feeders to the total current and the voltage carried to the load by the feeders.

Claims (19)

1. Electricity distribution network, characterized by the fact that it comprises: - at least two current feeders; - at least two loads, each associated with one of the respective feeders; - at least one module electrically connected to two feeders and including: a bidirectional auxiliary converter; DC bus, including a capacitor; and a bidirectional balancing converter connected in parallel; with the module also including means to change the current and voltage between the feeders and the bidirectional auxiliary converter and a differential electrical connection between the two feeders and connected in series with the bidirectional balancing converter; - a controller configured to control at least one parameter of an electric current flowing through or from each module, the voltage across or from each module being related to the maximum voltage difference between two of the feeders. 2. Electricity distribution network, according to claim 1, characterized by the fact that the bidirectional balancing converter is single-phase. 3. Electricity distribution network, according to claim 1 or 2, characterized by the fact that: - the two feeders are three-phase; - three modules are connected to the respective phases of the feeders; and the bidirectional auxiliary converter is a three-phase converter. Electricity distribution network according to any one of claims 1 to 3, characterized in that at least one module comprises a plurality of submodules connected in parallel, each submodule comprising a bidirectional auxiliary converter, a DC bus including a capacitor and a bidirectional balancing converter connected in parallel, with the submodule also including means to change the current and voltage between the feeders and the bidirectional auxiliary converter. 5. Electricity distribution network according to any one of claims 1 to 4, characterized in that a step-down transformer is the means by which the input current and the voltage of the bidirectional auxiliary converter are changed. 6. Electricity distribution network, according to claim 5, when dependent on claim 3, characterized by the fact that the step-down transformer comprises a single primary delta with three isolated star-connected secondary ones, each feeding one of the three modules . 7. Electricity distribution network, according to claim 5, when dependent on claim 3, characterized by the fact that the step-down transformer comprises a single transformer and three isolated bidirectional high-frequency DC / DC converters, each DC / DC converter being associated with one of the respective phases. 8. Electricity distribution network according to any one of claims 1 to 3, characterized by the fact that a DC / DC converter is the means through which the input current and the voltage of the bidirectional auxiliary converter are changed. 9. Electricity distribution network according to any one of claims 1 to 8, characterized in that the auxiliary converter and the balancing converter include semiconductor devices with forced switching. 10. Electricity distribution network, according to claim 9, characterized in that the forced switching devices are made of a semiconductor material, such as silicon carbide. 11. Electricity distribution converter, according to claim 9 or 10, characterized by the fact that the forced switching devices are selected from the group comprising: bipolar isolated transistors (IGBTs), switched integrated port thyristors (GTOs) ) and metal oxide semiconductor field effect transistors (MOSFETs). 12. Electricity distribution network, according to any of claims 1 to 11, characterized by the fact that the auxiliary converter and the balancing converter are configured to operate at frequencies up to 100 kHz. 13. Electricity distribution network, according to any of claims 1 to 12, characterized by the fact that the electrical connection between the two feeders includes a means of detecting the fault and protection condition. 14. Electricity distribution network, according to claim 13, characterized in that the means of detecting the fault condition and protection comprise a saturable reactor or a plurality of high voltage semiconductor switches connected in series. 15. Electricity distribution network, according to any of claims 1 to 14, characterized by the fact that at least one controllable parameter is selected from the group comprising: voltage magnitude, phase angle, active power and reactive power . 16. Electricity distribution network, according to any of claims 1 to 15, characterized by the fact that it is configured as a STATCOM compensator and including a P / Q controller (active power / reactive power). 17. Electricity distribution network, according to claim 16, characterized by the fact that, during operation, the bidirectional converter initially operates in the boost mode, charging the bus capacitor to a DC potential above the peak potential of supply, configuring the P / Q controller so that the parameter P is zero. 18. Electricity distribution network, according to claims 16 or 17, characterized by the fact that it comprises a transformer located between the three-phase source and the bidirectional converter. 19. Electricity distribution network, according to any of claims 16 to 18, characterized by the fact that, during operation, reactive energy can be exchanged between the source and the bus capacitor (STATCOM operation) by changing the phase angle with the P / Q controller.