Technical Field

[0001] The present relates to the field of battery charging systems such as are used in, e.g., electric vehicles. The present also relates to the field of rectifiers such as two-phase rectifiers operating at residential voltage and power.

Background

[0002] Currently, an electric vehicle (EV) typically comprises a battery bank and battery charging system. The battery bank typically requires direct current (DC) input to charge the batteries. To that end, an on-board charging circuit is provided that converts AC power typically found in the home to a DC input for the battery bank. In what is typically known as "level 1" and "level 2" charging, the battery charging system is provided with household or similar alternating current power, which it converts to DC in order to feed the battery bank. Level 1 and level 2 charging mainly differs by the amount of power supplied and sometimes by the voltage as well.

[0003] "Level 3" charging generally refers to DC charging, which can involve DC current at high power, e.g. voltages above 350V and high currents leading to charging powers that are typically above 15 kW and run up to 160kW. Level 3 charging stations are commercial charging stations that seek to charge EVs as quickly as possible. With current EV batteries, very rapid charging can be achieved up to about 75% to 80% of the battery's charge capacity. With some EV batteries, charging from 15% to 80% of battery capacity can be done within 15 to 20 minutes of high power charging. After this point, charging is very slow, for example, it can take a number of hours to raise the charge level from 80% to 99%. Normally the customer will be encouraged to leave the charging station so that other customers can charge their vehicles. Such rapid charging is convenient for commercial charging station operations, however, it can shorten the lifespan of some EV batteries to be subjected to such high power charging. For example, it might be preferable in terms of battery lifespan to allow for 2 hours to charge a battery from 15% to 80% of capacity instead of 20 minutes.

[0004] The DC power for such charging is supplied from three-phase power mains that are normally made available to commercial installations and not residences. Three-phase AC electrical power can be efficiently converted to DC. Typically, this kind of charging is unavailable in residences where available power is also typically limited to below 60 kW. In certain places, for example, power supply to the residential panel may be capped at 200A at 240V (RMS), giving a total available power, for all household use, of 48kW. By providing such a power limit using a main circuit breaker, the local distribution transformer, which is often sized using "oversubscription" assumptions, is statistically protected against overload as a result of too many residences drawing too much power. Moreover, level 3 charging, when starting from a single-phase AC current source requires a rectifier circuit, which is typically not provided in the home because of cost issues among other reasons.

[0005] Current residential car charging systems behave essentially like a high-power appliance, drawing from, e.g., a clothes dryer plug. In level 2 charging, the power is typically limited to about 7 kW or less that is a load comparable to a clothes dryer (30 amps at 240 V is 7.2 kW). The charging unit installed in the home connects the mains AC power to the vehicle through a breaker circuit so that the vehicle's on-board AC to DC conversion circuitry can charge the vehicle battery.

[0006] Most electric vehicles allow for "fast" DC charging in which case the AC to DC converter is external to the EV. An advantage of DC charging is not only that the charge power can be greater than the capacity of the AC to DC converter in the vehicle, but also that the efficiency of the conversion is not dependent of the converter provided by the manufacturer at the time of making the vehicle. If DC charging can be made efficiently available to residences, then heavy and expensive level 2 charging equipment onboard vehicles could be omitted.

With level 2 power consumption, the probability that vehicle's charging will cause the residential electrical entry or main circuit panel to draw more than its allowed power budget (and thus cause the main breaker to trip with the result that the panel is disconnected from the distribution transformer) is quite low. However, when a load greater than 7 kW is added to most domestic electrical panels, and for a duration of a number of hours, the risk increases that the total power budget of the domestic electric panel will be exceeded.

Summary

[0007] This patent application provides complementary improvements that may be applied separately or in combination. The first improvement relates to an improved rectifier used in DC charging. In one aspect, the improved rectifier has a high voltage capacitor module that is easily replaced within the charger. In another aspect, the charger comprises a backplane and blade architecture that allows the AC to DC conversion to be distributed over a number of lower power blade modules so as to use blade modules providing each less than about 3 kVA (preferably about 2 kVA) so that the combination of blade modules can provide power conversion of over 10 kVA (and preferably over 20 kVA) of AC single phase power into DC charging power output. In another aspect, the charger is a five-level PUC5 charger having redundant states. The second improvement relates to a battery charging system that allows a power level to be used for battery charging that would exceed the nominal budget of the electrical entry if all non-charging loads were connected to the entry drawing their loads at the same time. Therefore, according to the second improvement, a time-based prediction of non- charging load power consumption is made based on modelling and/or historical monitoring of non-charging load power consumption. A third improvement relates to a power converter having a charging power program module with a user input interface for receiving user input defining charging aggressivity parameters, wherein the charging power program module controls a current level over time in response to the charging aggressivity parameters. A fourth improvement relates to a socket-type connector for removing and replacing a high voltage capacitor from a power converter.

[0008] In some embodiments, a battery charger converts single phase AC power and delivers DC power to an electric power storage battery. An AC input receives single phase power from an electrical entry, a power converter is connected to the AC input and responds to a charge voltage value and a desired charge current value to convert power to a variable DC voltage at a variable current not exceeding a desired charge current value for a DC load. The power converter has at least one high voltage capacitor for storing power at a voltage boosted above a peak voltage of the AC input.

[0009] Provided are systems, methods and more broadly technology as described herein and claimed below.

Brief Description of the Drawings

[0010] The present examples will be better understood with reference to the appended illustrations which are as follows:

Figure 1 is a schematic illustration of the physical installation of a home EV charging system including a pole-top transformer, residential electrical entry with a load sensor and a main circuit breaker panel, a 240V AC power line between the panel and a charger, a charge cable extending between the charger and an electric vehicle (EV) with CAN bus connection between the EV and the charger;

Figure 2A shows a circuit diagram of a battery charger rectifier according to a particular example of implementation;

Figure 2B shows a circuit diagram of a packed U-cell topology circuit of the battery charger rectifier of Figure 2A showing connectivity under one switching configuration called "State 2";

Figure 2C shows a circuit diagram of a packed U-cell topology circuit of the battery charger rectifier of Figure 2A showing connectivity under one switching configuration called "State

3";

Figure 3 A shows a block diagram of a modulator with voltage balancing of the battery charger rectifier of Figure 1; Figure 3B shows a signal graph showing a 4-carrier pulse-width modulation technique used in the modulator of Figure 3 A;

Figure 3C shows a circuit diagram showing elements of a controller of the battery charger rectifier of Figure 1;

Figure 4 shows a block diagram of the battery charger rectifier of Figure 1 including controller circuitry;

Figure 5 shows a signal graph illustrating steady state results of the battery charger rectifier of Figure 1 at 1 kW operation;

Figure 6 shows a screenshot of a power analyzer showing some parameters of the battery charger rectifer of Figure 1 measured by the power analyzer;

Figure 7 shows a signal graph illustrating performance of the battery charger rectifier of Figure 1 during a 50% change I the DC load;

Figure 8 is a block diagram showing a modular rectifier battery charging system;

Figure 9 is a block diagram showing a charging power budget controller; and

Figure 10 is a schematic diagram of a power converter module according to one embodiment.

Description

[0011] Fig. 1 illustrates the physical context of an embodiment in which split single phase mains power is delivered from a utility pole top transformer, as is the most common type of electrical power delivery in North America. The transformer receives typically 14.4 kV or 25 kV single phase power from a distribution line and the transformer can handle approximately 50 kVA to 167 kVA of power delivered as split phase 240 VAC to a small number of homes or electrical entries. Each electrical entry is typically configured to handle between 100 A to 200 A of power at 240 VAC, namely about 24 kVA to 48 kVA (the common assumption is that 1 kVA is equivalent to 1 kW).

[0012] It will be appreciated that embodiments are not restricted to split single phase 240 VAC power systems, and that the embodiments disclosed herein can be adapted to the power networks in use that are single phase of any existing AC voltage delivered to the electrical entry of homes or businesses.

[0013] The electrical entry typically comprises a usage meter, a main breaker having a rating corresponding to the total permitted load (e.g. 100 A or 200 A), and a panel having circuit breakers for each household circuit which may be supplied with 240 VAC power or 120 VAC power from the split-phase 240 VAC input. While most circuit breakers have capacities of between 15 A to 30 A, some can be lower (namely 10 A) and some may be larger, such as 40 A, for large appliances. In some countries, electrical entries have a lower capacity, such as 40 A to 60 A, and in countries with 240 VAC in all household circuits, the power is not split phase, but regular single phase 240 VAC (the voltage level used can vary from about 100 V to 250 V).

[0014] As illustrated in Figure 1, the DC charger is connected to a circuit breaker of the main panel through a breaker having a larger current rating, such as 40 A to 80 A, although the charger disclosed can consume over 100 A if desired. The need for a circuit breaker specific to the charger is determined by electrical codes. The cable connecting the charger to the panel is rated for such high current. The connection to the electrical panel can be a direct fixed wiring, or a high voltage socket can be installed and connected to the electrical panel such that the DC charger connects to the panel using a cable and plug, for example those that are similar to those used for appliances like ovens or clothes driers. The charger is shown to be connected to a single load sensor that senses the load drawn by the whole panel including the charger.

[0015] The DC charger cable can be a conventional DC charger cable and plug, as is known in the art.

[0016] Fig. 2 A shows a battery charger rectifier 100 for an electric vehicle according to a particular example of implementation. The circuit features a 5-level Packed U-Cell topology providing an active rectifier with power factor correction. The charger has several noteworthy advantages over other types of rectifiers and features a boost mode operation which allows supra- AC peak output while reducing or eliminating input side current harmonics.

[0017] The battery charger rectifier 100 comprises an AC input 105, an inductive filter 110 connected in series with the AC input 105, and a packed U-cell topology (PUC) circuit 115 which in this example is a 5-level packed U-cell topology (PUC5) circuit.

[0018] The inductive filter 110 in this non-limiting example is a 2.5 mH inductor. For a typical 1 to 3kW range of power to be delivered (during all charging states of full power to under- power), a lmH line inductor provided good results which complied with existing standards. For higher power ranges, the inductance may be reduced; for example, for a high wattage (e.g. greater than 2kW, and preferably greater than 3kW, and more preferably approximately 5kW) power rating, the inductive filter 110 may instead use a 500μΗ inductor. Conveniently the present design allows for a small geometry of the overall battery charger rectifier 110, due in part to the small size of the inductive filter 110. The inductive filter 110 can vary according to design as chosen based on the application, power rating, utility voltage harmonics, switching frequency, etc. Although the simplest such filter is a single inductor, in alternative embodiment the inductive filter 110 may include a combination of inductor(s) and capacitor(s), e.g. an (e.g. 2mH) inductor connected to a (e.g. 30μΡ) capacitor, itself connected to ground. The choice of filter has an impact on overall size of the design and losses, with a bigger filter increasing the size of the overall design and generally incurring more losses. [0019] The PUC circuit comprises a high voltage capacitor 120, at least one low voltage capacitor 125, two high voltage power switches 130a, 130b connected between a first terminal 135 and respective opposed ends 145a, 145b of the high voltage capacitor 120, two intermediate low voltage power switches 140a, 140b, each connected between respective ones of the two opposed ends 145a, 145b of the high voltage capacitor 120 and respective opposed ends 155a, 155b of the low voltage capacitor 125, and two terminal low voltage power switches 150a, 150b each connected between a second input terminal 160 and respective ones of the opposed ends 155a, 155b of the low voltage capacitor 125.

[0020] The capacitors are so named because the high voltage capacitor 120 has, in use, a higher voltage across it than there is across the low voltage capacitor 125. In this particular example, the voltage Vo across the high voltage capacitor 120 is approximately twice the voltage Vc across the low voltage capacitor 125. In the present example, the high voltage capacitor 120 and the low voltage capacitor 125 are different devices, the high voltage capacitor 120 being a 2mF capacitor and the low voltage capacitor being a 50μΤ capacitor. For a typical 1 to 3kW range of power to be delivered (during all charging states of full power to under-power), a combination of a 2mF capacitor for the high voltage capacitor 120 and a ΙΟΟμΡ capacitor for the low voltage capacitor 125 gave good results which complied with existing standards. This has been found to work when using a 20μβ sampling time for the voltage balancing. For a 5kW power device, a combination of a 4mF capacitor for the high voltage capacitor 120 and a 200μΡ capacitor for the low voltage capacitor 125 may be suitable, however it may be possible to use smaller capacitors by increasing the speed of sampling done for voltage balancing and so achieve more precise calculations for voltage balancing. This may be achieved by using a faster microprocessor. Each of the capacitors may be electrolytic or film capacitors but in the present example, the low voltage capacitor 125, which is not connected to the load, is a high lifetime film capacitor. The high voltage capacitor 120 will have a shorter lifetime and will likely be the cause of failure in the circuit. In the embodiment illustrated in Figure 10, the high voltage capacitor is therefore provided as a replaceable component, as will be further described with reference to Figure 10.

[0021] Naturally, it is more economical to use capacitors having characteristics not exceeding their requirements, however nothing prevents the use of identical capacitors for both the high voltage capacitor 120 and the low voltage capacitor 125, although in such a case the low voltage capacitor 125 would be over-specified.

[0022] The intermediate low voltage power switches 140a, 140b and the terminal low voltage power switches 150a, 150b together make up the auxiliary power switches. As with the capacitors, the high voltage power switches 130a, 130b and the low voltage power switches are so called because high voltage power switches 130a, 130b have, in use, a higher voltage across them than the auxiliary power switches. Moreover, according to the present design, the low voltage power switches are high frequency power switches while the high voltage power switches 130a, 130b are low frequency switches. Again they are so called because, in use, the high frequency switches are operated/switched at a higher frequency than the low frequency switches. In fact, identical switches may be used throughout provided that they are suitable for the highest frequency applied to the high frequency switches and that they are suitable for the high voltage applied across the high voltage switches. However, it is preferable to provide switches that are suited only for their intended use so as to reduce costs, as well as, potentially, size and weight. The switches may all be of the FET, JFET, IGBT and MOSFET types.

[0023] The low voltage capacitor 125 of the PUC circuit 115 may be considered an auxiliary capacitor which, together with the auxiliary power switches makes up the auxiliary circuitry 116 of the PUC circuit 115. As described herein, additional auxiliary capacitor(s) and pair(s) of switches may be provided in the auxiliary circuitry 116 in alternative embodiments.

[0024] The PUC circuit 115 switching states have been investigated to reveal the redundant ones so as to help balancing the auxiliary capacitor voltage. The capacitor voltage balancing allows producing 5 voltage levels at the rectifier input and reducing the voltage harmonics that affects the current harmonic contents directly. The output terminal voltage is regulated to supply DC loads. Herein, experimental results are provided demonstrating dynamic performance of the proposed rectifier operating at unity power factor and drawing low harmonic AC current from the utility/source.

[0025] As shown in Fig. 2A, the battery charger rectifier 100 has only 6 switches, with which it generates 5 voltage levels. The promising feature of that configuration is the redundant switching states which facilitate voltage balancing between DC links. The PUC5 rectifier is proposed in this paper operating at unity power factor as well as eliminating input AC current harmonics since working in boost mode. The low THD 5-level voltage waveform of the PUC5 rectifier affects the line current harmonics directly so that the inductive filter could be smaller than 2-level rectifier one in order to reduce the size of the product. Since the auxiliary DC capacitor voltage could be balanced just by the redundant switching states, the voltage/current regulation of the PUC5 rectifier is same as a full bridge one with single output DC terminal which could be done through a cascaded PI controller.

[0026] The PUC5 rectifier configuration and switching states will now be discussed. Provided herein is a voltage balancing based switching technique. With respect to the described design, practical tests have been performed in different conditions such as load changes, AC main variation, which tests have shown good dynamic performance for the battery charger rectifier 100 [0027] The PUC circuit 115 has two DC links. The main DC link comprises the high voltage capacitor 120 that is voltage regulated to supply DC load. The voltage across the high voltage capacitor 120 is designated Vo herein. A secondary DC link comprises the auxiliary capacitor (low voltage capacitor 125). The voltage across the low voltage capacitor 125 is designated Vc herein. Vc has half the voltage amplitude of main terminal (VO) and is used for forming the rectifier input voltage (Vin), across the first and second terminals, as a 5-level quasi sine wave. Therefore, VC = E, VO = 2E and 5 voltage levels include 0, ±E, ±2E.

[0028] Operating in boost mode means herein that the output DC voltage is higher than the input AC peak value. In the present example:

Vs-rms = 120 V → Vs-peak = 120Λ/2 = 170 V

[0029] Based on the peak value of the AC grid, the DC voltage was selected at 200V. Now since Vc is half of Vo, we have:

Vo = 200 V → Vc = 100 V

[0030] To that end, the output terminal voltage Vo is regulated at 200V to feed the DC load which in this example is an EV battery bank. Moreover, the auxiliary capacitor voltage Vc is balanced at 100V in order to generate 5-level voltage waveform as Vin.

[0031] Based on the above selected voltages, the two high voltage power switches 130a, 130b are selected to withstand 200V. The auxiliary power switches see only approximately half the voltage of the high voltage power switches 130a, 130b, which in this example is 100V.

[0032] Table 1 shows the switching states of the PUC circuit 115. Each pair of switches, which in this example include the pair of high voltage power switches 130a, 130b, the pair of intermediate low voltage power switches 140a, 140b and the pair of terminal low voltage power switches 150a, 150b, are complimentary, meaning that when one is open the other is closed and vice versa.

Table I - Switching States of the PUC Circuit 115 [0033] It is observable that based on each configuration of switches, a path is provided to flow the current through the converter and a voltage level is appeared at the input that together form the 5-level voltage waveform. That smooth waveform has low total harmonic distortion (THD) and affects directly on the drawing current harmonic contents (If there is harmonic in voltage waveform, then it will be injected into current waveform, too. A low harmonic voltage waveform causes a low harmonic current waveform). The naturally reduced amount of THD permits the use of a smaller filter in the AC line with acceptable performance compared to the larger filter typical of 2-level converters.

[0034] As will be noted from table 1, the high voltage power switches 130a, 130b, are in fact only switched twice per period. However, the auxiliary power switches may be switched at a much higher frequency, e.g. switching between redundant states (e.g. states 2 and 3) multiple times before moving on to the next non-redundant state (e.g. state 4). In certain embodiments, the low voltage power switches may be switched at a high frequency, of at least, or more than, 1 kHz, for example greater than 10 kHz. In this particular example, the switching frequency may be of 48kHz.

[0035] Voltage balancing for the present battery charger rectifier 100 will now be described. As will be seen in Table I, there exist some redundancies among switching states -that is to say that there exist switching states resulting in a same Vin voltage such as states 2 and 3 or states 6 and 7. Since the main output is Vo and is controlled by an external PI controller, the redundant switching states can help in several ways. One benefit of the redundant switching states is that reducing the voltage error of Vo results in lowering the external controller burden, Moreover, balancing the auxiliary capacitor voltage Vc allows providing 5 identical voltage levels in order to generate a low THD quasi sine waveform.

[0036] In Figs. 2B and 2C, the current paths 205, 210 for redundant states 2 and 3, respectively, are shown to better illustrate the effect of redundant switching states on the DC links voltage balancing.

[0037] The DC links polarities are assumed as shown in the figure. They can be charged or discharged based on the current sign. At state 2, assuming that the current is positive, then the high voltage capacitor 120 is charged while the low voltage capacitor 125 is discharged due to its reversed polarity. Thus, Vo and Vc are increased and decreased, respectively. However, at state 3, the low voltage capacitor 125 will be charged by a positive current in state 3. Those states will affect reversely if the current sign is negative. It should be also noted that the Vo will be decreased due to discharging on the load whenever it is not connected through the AC source. [0038] Table II similarly shows the effect of each switching state on the high voltage capacitor 120 and on the low voltage capacitor 125, which gives helpful information to design the associated voltage balancing technique.

Table 2 - Effect of Switching States on Vo and Vc

[0039] Since the proposed converter may be a grid-connected one and the associated controller already includes a current sensor, there it is possible to avoid having additional sensors and the associated costs. A same line current sensor feedback signal may be used in the voltage balancing technique. Two voltage sensors may be used as DC voltages feedbacks and the switching technique may include a multi carrier PWM manipulated by the voltage effects listed in Table II. The switching technique selects the redundant switching state based on the feedbacks received from the current and voltages sensors.

[0040] Fig. 3A illustrates a schematic of the voltage balancing technique integrated into a modulator with voltage balancing 305. As shown, in this example a modulator 310 is used that provides 5-level PWM. In this example, a 4-carrier PWM technique is used to modulate the reference signal 320, as shown in Figure 3B. The reference signal 320 therefor is provided from the controller which is described below. The output of the modulator 310 is provided to a state selection circuit 315 which enforces the logic of Table I and Table II to generate inputs to the switches, here in the form of signals to SI, S2, and S3 and inverse (NOTed) version of these signals to S4, S5, and S6, respectively. The state selection circuit 315 provides a rapid voltage balancing procedure integrated into switching technique, thanks to which it is expected that a small size capacitor would be suitable for the auxiliary capacitor. A schematic illustration of the algorithm used is illustrated in Figure 3C, which shows logic elements of both the modulator 310 and the state selection circuit 315 to provide 8 signals indicative of respective states. These signals are then used by a pulse generator circuit 325 to generate the pulse outputs to the switches.

[0041] In Figure 3 A, it is shown that a voltage feedback is used in voltage balancing part. However, the voltage balancing unit can use voltage or current feedback. When both are used, it is possible to balance the capacitor voltage more robustly.

[0042] A controller 410 for the system the system may employ a cascaded proportional- integral (PU) controller, which will now be described. As mentioned above, the present exemplary configuration was may be used as a single-DC-source inverter since the auxiliary capacitor voltage is balanced through the switching states. Although some of the proposed topology has been proposed for rectification with two DC capacitors, in the present embodiment the auxiliary capacitor is voltage controlled by the designed switching technique and does not require any additional voltage regulator. Hence, we may use only one external voltage controller to fix the output DC terminal to a desired level, which in the present example is 200V. As a result, a simple cascaded PI Controller may be used to regulate the output DC voltage as well as to control the input current and synchronize it with the grid voltage to ensure power factor correction (PFC) operation of the rectifier. The controller 410 is responsible for regulating V ₀ and is, which it does in response to an input from a battery management system (BMS), such as may be provided on an EV.

[0043] With reference to Figure 10, it will be understood that the controller 410 also controls a DC to DC downconverter in response to the desired output DC voltage requested by the BMS. In Figure 10, this is a simple buck converter controlled by switch S7 using the feedback of the measured DC output voltage using a sensor.

[0044] In the example of Figure 4, controller 410 regulates the V ₀ voltage at a reference level of Vref received as input and also controls the grid current is to eliminate or reduce its harmonics and make it in-phase wit grid voltage as unit power factor operation or close thereto (e.g. PF=99.99%). An exemplary implementation of the controller 410 is shown schematically in Fig. 4 where current and/or voltage from the sensor is sampled by the controller 410 as required (e.g. about every 20 microseconds).

[0045] The voltage regulator tries to minimize the Vo error by adjusting the current reference (is ^* ) amplitude. The shape of the current reference is generated in this example through a unit sample of the grid voltage to ensure the PFC mode. Eventually the controller output 320 is modulated by the standard 4-carrier PWM technique to send the required pulses.

[0046] Experimental results for the battery charger rectifier 100 will now be described. In one particular example of testing, practical tests have been carried out on a silicon carbide (SiC) based PUC5 converter. Six 1 2KV 40A SiC MOSFETs type SCT2080KE were used as active switches. The proposed voltage balancing approach integrated into switching technique and the cascaded controller were implemented on dSpace 1 103 and consequently, switching pulses were sent to the PUC5 switches. The tested system parameters are listed in Table III.

Table 3 - Practical Test Parameters

[0047] In alternate embodiments, the AC input (grid) voltage may be about 240V RMS and the DC load may be greater than 350 V, as provided by boost mode rectification in the manner described herein.

[0048] The steady state results at 1 kW have been captured as seen in Fig. 5. As shown, the output DC terminal voltage was regulated at 200V with acceptable voltage ripple less than 10%. Moreover, due to effective voltage balancing of Vc, the Vin has been formed by 5 identical voltage levels of 0, ±100, ±200V with lower harmonic pollution than a 2-level voltage waveform. Moreover, PFC operation of the battery charger rectifier 100 can be observed through the input voltage and current waveforms (v _s and is). Eventually, the load current (/ ^' /) was measured at almost 5 A which demonstrates an achievement of the IkW operating system.

[0049] Fig. 6 depicts some other parameters measured by an AEMC™ power analyzer. It is to be appreciated that the battery charger rectifier 100 was tested at IkW with the highest possible power factor (close to unity) which reduces the amount of reactive power significantly and promises the good performance of the controller in synchronizing the line current with the grid voltage. Moreover, the current THD is also low thanks to the low harmonic pollution of the multilevel voltage waveform generated by the PUC5 rectifier (The standards of IEEE519 and IEC61000 require a line current with THE) of less than 5%).

[0050] In this testing, a 50% load change was eventually made intentionally (from 38Ω to 75Ω) in order to examine the dynamic performance of the controller. As shown in Fig. 7, the load current was reduced to almost half of the initial amplitude. Consequently, due to change in the amount of energy delivered to the load, the Vo varied but was well stabilized by the controller and voltage balancing technique without unexpected over or undershoot. Moreover, the input AC current was kept synchronized with the grid voltage while its amplitude was changing to reach the steady state mode. It will be appreciated that the current harmonic is also eliminated during the transition.

[0051] The practical results of the battery charger rectifier 100 have shown good dynamic performance of the controller and voltage balancing technique which has been integrated into the modulation process. The auxiliary capacitor voltage is kept regulated at desired level with low voltage ripple due in part to such fast and accurate voltage balancing approach results in generating a 5-level quasi-sine voltage waveform at the input of the rectifier with low harmonic contents. Such multilevel waveform allows the use of small size filter to eliminate the line current harmonics. The battery charger rectifier 100 may therefore be well suited potential candidate to be used as industrial rectifier in traction systems or battery charger for EV applications.

[0052] A voltage balancing technique has been designed and integrated into switching pattern to regulate the auxiliary capacitor voltage resulted in generating 5 identical voltage levels at the input of that rectifier to form a 5-level smooth voltage waveform with low harmonic content. A standard cascaded PI controller has been implemented on the proposed rectifier in part due to having a single DC terminal without any split capacitors at the output. Practical tests shown good dynamic performance of the battery charger rectifier 100, implemented voltage balancing technique and controller during steady state and load change conditions. It may also be a potential product for the PFC rectifier market.

[0053] To provide a 7-level / 3-capacitor implementation, two more power switches and one additional low voltage capacitor would need to be added. The modulation block would also be changed to have six carrier waves. The voltage balancing unit will be changed because there would be more switching states to charge and discharge the capacitors and regulate their voltages.

[0054] The battery charger rectifier 100 may be provided in a battery charger alongside other parallel battery charger rectifier circuits of like construction, as illustrated in Figure 8, each working in parallel to provide DC power to the load. To this end, the battery charger may comprise a housing including a connector backplane having a number of sockets for receiving a plurality of modules each comprising a battery charger rectifier of the type described herein, although a common controller can be used as illustrated in Figure 8. An advantage of this modular approach can be that a backplane can be first installed, possibly using the services of a professional electrician, while an end-user may add or replace the modules 100 as required. The modular approach illustrated is not limited to any particular number of modules 100, however, Applicant has found that, in particular using the rectifier design described herein above, that a 5 kW rectifier module is efficient, and 5 of such modules provides a combined DC charging power of about 25 kW. This amount of power is suitable for high speed battery charging while being feasible within the available power budgets of most conventional single- phase electrical entries.

[0055] For practical implementation, a battery charger comprising the battery charger rectifier 100 may comprise a user-interchangeable DC vehicle charging cable and charging plug, e.g. having a compatible format for fitting a standardized plug/socket (i.e. SAE J1772, ChaDeMo, or other) in an EV.

[0056] Figure 9 is a block diagram showing a battery charger for an electric power storage battery. An electrical entry is connected to a local distribution transformer of a power grid via a sensor and a main breaker having a predetermined current threshold. The sensor provides a value of current drawn by the electrical entry. A battery charging controller interface communicates with the electric power storage battery and receives a charge voltage value and a desired charge current value. A rectifier circuit is connected to the electrical entry for receiving single phase AC input power, and it outputs a high DC voltage that can be downconverter using, for example, a DC buck converter circuit. The buck converter has a control input defining an output DC voltage and current. As illustrated in Figure 10, the controller 410 can control the buck converter to output the desired DC voltage and current.

[0057] A logging module stores in a memory at least one parameter derived from the current drawn as measured by the sensor less any power drawn by the rectifier circuit over time for various sub-periods within each day. This parameter can be the greatest probable increase in non-charging loads for the present time period and the present non-charging load. Jumps in load can be derived from one or more appliances turning on. AC motors, such as heat pump and air conditioning compressor motors, typically draw at least twice their steady state current when starting. As can be appreciated, the probability of an increase in power drawn can be within a desired likelihood, such as within 97% probability.

[0058] An available power predictor calculator receives the current drawn value and the logging module parameter and provides a maximum charge load value as a function of a predetermined electrical entry maximum power load. The maximum load value for the electrical entry can be set using a user interface (not shown). A power budget controller receives the maximum charge load value and, from the battery management interface, the desired charge voltage value and desired charge current value and provides the control input to the rectifier circuit.

[0059] In one embodiment, the greatest probable increase is determined based on long term observation data. Until such data is acquired, the available power predictor may behave more conservatively, and as the certainty increases about the prediction, the predictor calculator can be more aggressive.

[0060] In another embodiment, the variations in power consumption are analyzed to determine the number and sizes of the main household loads. A behavior pattern for these loads is then detected. Loads that are estimated to be on, can only be turned off, and so they do not contribute to a risk of increasing the total load. The probability that a load will turn on is based on the state of other loads, time of day and time of year. For example, if a water heater is off, there can be a higher likelihood that it will turn on at any given moment from 7AM to 8AM due to water usage than from 11PM to 6AM. In summer, electric heating loads are unlikely to turn on, while AC is more likely, and the opposite may hold true in winter. Based on behavior patterns and the current estimate of what loads are on, the available power predictor can predict the greatest probable immediate increase in power.

[0061] The power budget controller considers the risk of the greatest probable increase in power to determine what power is available to the charger for consumption, and the power budget controller causes the rectifier circuit and/or the DC-DC downconverter to adjust DC power delivered to the EV when the requested power would be too great.

[0062] Furthermore, the power budget controller can consider battery degradation when setting the charging rate. This can involve referencing a predetermined maximum charge current or power value. As described below, a user-selected charge aggressivity level can also be referenced.

[0063] When the available power predictor module forecasts that an increase in power is probable that could risk exceeding the power budget (entry limit), an optional sheddable load switch can be used to prevent a significant load from drawing power that can result in exceeding the power budget. This can delay or shift the added load to avoid exceeding the power budget of the electric entry. The sheddable load switch can include a line voltage power switch connected between one or more electrical loads and the electrical panel, for example a hot water heater, to prevent the load from drawing current from the electrical panel with the risk that such additional load could exceed the power budget. Preferably, the load switch includes a sensor, for example a current sensor, to measure whether the load is currently drawing power. In this way, the power budget controller can detect if the load in question is drawing power. The sheddable load switch, when open, can be equipped with sensors to detect when the disconnected load is looking to draw power, and in this case, the power budget controller can then decide to reconnect the load after reducing DC charging power accordingly.

[0064] Some loads that draw high current include control electronics that draw a small load in a stand-by state, for example, less than about 100 watts. In this case, it is possible to include by-pass low power AC to the sheddable load while the sheddable load switch is open. An example of a low power AC by-pass connection is an isolation transformer configured to provide about ten to several tens of watts of power for the electronics of the sheddable load. When the load switches on, the sheddable load switch module can detect the draw of power on the load side of the isolation transformer and then signal the power budget controller to decide whether to reduce DC charge power to allow the sheddable load to be reconnected to full AC power, or whether DC charging at the same rate should continue. When DC charging load demand is over and then permits, the sheddable load can be reconnected.

[0065] The embodiment in Figure 9 includes a charging power program module that responds to user input to curb the charge rate when the user is not in a rush to charge the EV. While EV's can permit fast charging, and embodiments disclosed herein can allow for charging with powers of about 25 kVA, battery life can be reduced by repeated fast charging. Additionally, the charging power program module may be used to select a time program for charging, namely to delay and/or otherwise tailor power consumption in accordance with time-variable energy costs and/or the availability of power within the distribution network. The charge connector can, for example, provide a user interface for selecting a charge aggressivity level, namely a variable level of charge rate when the battery requests high rate charging. Alternatively, a network interface can be provided to allow a remote user interface to be used to set charging power program parameters.

[0066] Figure 10 illustrates schematically a single "blade" 100 of the modular system illustrated in Figure 8. In the embodiment illustrated, a printed circuit board is provided along one edge with high voltage AC and DC connectors as well as connectors for a data interface. The blade 100 contains the power switches for the power converter, and in this embodiment, there are six switches SI to S6 for the PUC 5 active rectifier and one switch S7 for the buck converter providing DC to DC downconversion.

[0067] The capacitor 120 is provided on a small module that has a socket for connecting into a plug on blade 100. The quality of the high voltage capacitor 120 can be important for proper and safe operation of the rectifier. Timely replacement can therefore be advisable. The socket can include an identification circuit that can be read by controller 410 to determine a variety of information. First, it can be used to determine whether or not a new capacitor has been installed as required. Second, it can be used to determine whether the capacitor installed has been previously used. This can be achieved in a variety of ways. For example, the controller 410 can report to an external database the usage of each capacitor 120 as identified by its unique ID. Such a database can be queried when a new capacitor is plugged in. Alternatively, the identification circuit within the capacitor plug module can store information about usage in a non-volatile memory that can be read by controller 410. In this way, when a new capacitor module is connected to a blade 100, the controller 410 can determine if capacitor 120 should be considered to be fully new, partly used, or expired. In the case of an expired capacitor 120, the controller 410 can refuse to provide power and issue a warning to prompt replacement of the capacitor 120.

[0068] It will be appreciated that the manner of providing connectivity to a blade module 100 can use cable connectors instead of the edge connection shown. It will also be appreciated that the capacitor module's socket can be provided on the blade 100 as shown in Figure 10, or it can be provided elsewhere, such as in a separate portion of the back plane (see Figure 8).

[0069] The socket can include a switch to detect that the capacitor plug module is being removed or is exposed for removal, so that powering down of the blade or blades 100 can be done to allow for safe removal and replacement of the capacitor modules 120. While each blade 100 is shown in the embodiment of Figure 10 to have its own controller 410, it is possible to have a common controller 410 on the back plane control the switches from a number of blades.

[0070] The sensor block in Figure 10 is illustrated as being connected to measure the voltage at the low voltage capacitor, the DC output current ad the DC output voltage. Other values can be also measured if desired. The values measured are provided to the controller 410.

[0071] Although the above description has been provided with reference to specific example, this was for the purpose of illustrating, not limiting, the invention. Variants as may be understood by the skilled person as being within the scope of the claims are intended to